We acknowledge Praveen, Kusum, Chandan, Isha, Rashmi, Babli, Shivani, Ankita, and Shikha for their technical assistance.

This study did not involve any human participants or clinical samples. The only biological material used was the 4th WHO International Standard for HBV DNA for nucleic acid test (NIBSC code 10/266). This standard is a publicly available reference material that does not contain any personal information or identifiable data. As such, no ethical approval was required for this study.
1. DNA Extraction
<ol>
	<li>Extract the viral DNA from human serum or plasma sample. Store the extracted DNA at -20 &#176;C until further use in PCR. 
	&#8203;NOTE: The recommended volume of serum or plasma for DNA extraction is 500 &#181;L, and the elution volume is 50 &#181;L. In this study, the viral DNA was extracted using a viral nucleic acid extraction kit (Table of Materials).</li>
</ol>
2. Real-time PCR
<ol>
	<li>Thaw all the reagents (Table 1) of the real-time PCR kit at room temperature (RT; 15-25 &#176;C) before starting the PCR. When thawed, mix the components by pulse vortexing for 10 s at a moderate speed and centrifuge at 8,000 &#215; g for 15 s at RT. Keep all the thawed components on a cooling block.</li>
	<li>Reaction preparation
	<ol>
		<li>Prepare a PCR mix according to Table 2. Calculate the volume of the reagents to be added based on the number of samples, standards, and no template control. 
		NOTE: When preparing the PCR mix, at least 10% extra volume of each reagent should be added (e.g., if 10 reactions are required, calculate for 11 reactions).</li>
		<li>Pipet 15 &#181;L of the above-prepared PCR mix into each PCR tube. Then, add 15 &#181;L of the extracted sample DNA. Add 15 &#181;L of at least one of the standards for HBV (HBV Standard 1-5) as a positive control (PC) for detecting HBV DNA and 15 &#181;L of PCR-grade nuclease-free water as a negative control (NC). To generate a standard curve required for quantitation of the HBV DNA, use all 5 quantitation standards supplied with the kit (HBV Standard 1-5) for each PCR run.</li>
		<li>Close the tubes, mix the components by pulse vortexing for 10 s at a moderate speed, and centrifuge at 8,000 &#215; g for 15 s at RT before proceeding to the thermal cycler. Ensure no bubbles are in the reaction mix, as it may interfere with fluorescence detection.</li>
	</ol>
	</li>
	<li>Program setup
	<ol>
		<li>Program the thermal cycler using the cycling conditions as recommended in Table 3.</li>
	</ol>
	</li>
	<li>Channel/Fluorophore Selection
	<ol>
		<li>Select the fluorescent dyes for commonly used real-time PCR platforms, as mentioned in Table 4.</li>
	</ol>
	</li>
	<li>Data analysis
	<ol>
		<li>After the run is completed, analyze the amplification plot on a linear scale.</li>
		<li>Threshold setting
		<ol>
			<li>Set the threshold within the exponential phase of a PCR reaction. Recommended threshold values for the kit are mentioned in Table 5. Be consistent with the threshold setting. Once the optimal threshold for the assay is determined, use it consistently for all the samples for a particular PCR machine. This will help to ensure that the results are accurate and reproducible. 
			&#8203;NOTE: If the threshold is set too low, the signal may be below the noise level, and the Ct value will be unreliable. If the threshold is set too high, the signal may be in the plateau phase of the reaction, where the amplification is not as efficient, and the Ct value may be inaccurate.</li>
		</ol>
		</li>
		<li>Cutoff
		<ol>
			<li>Run the kit for 40 amplification cycles. Do not consider any amplification beyond 38 cycles for any interpretation.</li>
		</ol>
		</li>
		<li>Qualitative result analysis
		<ol>
			<li>Use the kit for qualitative detection of HBV DNA. Use Standard 2 as PC with expected Ct values at 20 &#177; 2 for HBV and 24 &#177; 3 for IC.</li>
			<li>Ensure no template control (NTC) does not exhibit any amplification for both HBV and internal control (IC) targets. If an amplification reaction occurs in the NTC reaction, then sample contamination may have occurred.</li>
			<li>Since the assay cutoff is 38, consider any amplification before 38 Ct for the HBV target as an HBV-positive sample. When all controls meet the above-stated requirements, consider a specimen following the interpretations mentioned in Table 6.</li>
		</ol>
		</li>
		<li>Quantitative result analysis
		<ol>
			<li>Use the set of 5 quantification standards of known concentrations for HBV-specific DNA that are calibrated against the 4th WHO International standard for HBV DNA for nucleic acid amplification techniques (NAT)20 (Table 7).</li>
			<li>Employ these standards to generate a standard curve. Utilize the standard curve to quantify the HBV DNA of an unknown sample. 
			NOTE: The real-time PCR software will generate a standard curve using the Ct values obtained for the HBV targets of all 5 standards and their corresponding concentrations in international units per microliter (IU/&#181;L).</li>
			<li>Only interpret the values for unknown samples if the slope of standards falls between -3.1 and -3.6, the R2 value is between 0.99 and 1.0, the PCR efficiency is between 90%-110% (0.9-1.1), and there is no amplification in the negative control.</li>
			<li>The software will calculate the concentration of each HBV-positive sample in international units per microliter (IU/&#181;L). To calculate the viral load (conversion of IU/&#181;L to international units per milliliter [IU/mL]), use the following equation: 
			Result (IU/mL) = (Result [IU/&#181;L] x Elution Volume [&#181;L])/ Sample Volume (mL) 
			NOTE: The 4th WHO International Standard for HBV DNA, NIBSC code 10/266, was extracted for viral DNA purification from 0.5 mL plasma, eluted the purified viral DNA into 50 &#181;L of elution buffer and used with the PCR kit as a reference sample along with the 5 HBV standards and NTC. The HBV viral load of the reference sample (NIBSC code 10/266) was calculated as (6659 IU/&#181;L x 50 &#181;L)/0.5 mL = 6,65,900 IU/mL.</li>
		</ol>
		</li>
	</ol>
	</li>
</ol>

Detection and Quantification of Hepatitis B Virus DNA in Human Serum

<ol>
	<li>Ryu, W. -. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Molecular Virology of Human Pathogenic Viruses. , (2016).</li><li>Lin, X., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chronic+hepatitis+b+virus+infection+in+the+Asia-Pacific+region+and+Africa:+Review+of+disease+progression.">Chronic hepatitis b virus infection in the Asia-Pacific region and Africa: Review of disease progression.</a> Journal of Gastroenterology and Hepatology. 20 (6), 833-843 (2005).</li><li>Iloeje, U. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Predicting+cirrhosis+risk+based+on+the+level+of+circulating+Hepatitis+B+viral+load.">Predicting cirrhosis risk based on the level of circulating Hepatitis B viral load.</a> Gastroenterology. 130 (3), 678-686 (2006).</li><li>Huang, Y. -. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lifetime+risk+and+sex+difference+of+hepatocellular+carcinoma+among+patients+with+chronic+Hepatitis+B+and+C.">Lifetime risk and sex difference of hepatocellular carcinoma among patients with chronic Hepatitis B and C.</a> Journal of Clinical Oncology. 29 (27), 3643 (2011).</li><li>. World Health Organization fact sheet Available from: <a target="_blank" href="https://www.who.int/news-room/fact-sheets">https://www.who.int/news-room/fact-sheets</a> (2023)</li><li>Watanabe, M., Toyoda, H., Kawabata, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+quantification+assay+of+hepatitis+b+virus+DNA+in+human+serum+and+plasma+by+fully+automated+genetic+analyzer+mutaswako+g1.">Rapid quantification assay of hepatitis b virus DNA in human serum and plasma by fully automated genetic analyzer mutaswako g1.</a> PLoS One. 18 (2), e0278143 (2023).</li><li>Chan, H. L. -. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Viral+genotype+and+Hepatitis+B+virus+DNA+levels+are+correlated+with+histological+liver+damage+in+HBeAg-negative+chronic+Hepatitis+B+virus+infection.">Viral genotype and Hepatitis B virus DNA levels are correlated with histological liver damage in HBeAg-negative chronic Hepatitis B virus infection.</a> The American Journal of Gastroenterology. 97 (2), 406-412 (2002).</li><li>Liu, C. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Viral+factors+correlate+with+Hepatitis+B+e+antigen+seroconverson+in+patients+with+chronic+Hepatitis+B.">Viral factors correlate with Hepatitis B e antigen seroconverson in patients with chronic Hepatitis B.</a> Liver International. 26 (8), 949-955 (2006).</li><li>Liu, C. -. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+Hepatitis+B+viral+load+and+basal+core+promoter+mutation+in+hepatocellular+carcinoma+in+Hepatitis+B+carriers.">Role of Hepatitis B viral load and basal core promoter mutation in hepatocellular carcinoma in Hepatitis B carriers.</a> The Journal of Infectious Diseases. 193 (9), 1258-1265 (2006).</li><li>Yeo, W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hepatitis+B+viral+load+predicts+survival+of+HCC+patients+undergoing+systemic+chemotherapy.">Hepatitis B viral load predicts survival of HCC patients undergoing systemic chemotherapy.</a> Hepatology. 45 (6), 1382-1389 (2007).</li><li>Yim, H. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Levels+of+Hepatitis+B+virus+(HBV)+replication+during+the+nonreplicative+phase:+HBV+quantification+by+real-time+PCR+in+korea.">Levels of Hepatitis B virus (HBV) replication during the nonreplicative phase: HBV quantification by real-time PCR in korea.</a> Digestive Diseases and Sciences. 52, 2403-2409 (2007).</li><li>Noh, R., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Clinical+impact+of+viral+load+on+the+development+of+hepatocellular+carcinoma+and+liver-related+mortality+in+patients+with+hepatitis+c+virus+infection.">Clinical impact of viral load on the development of hepatocellular carcinoma and liver-related mortality in patients with hepatitis c virus infection.</a> Gastroenterology Research and Practice. 2016, 7476231 (2016).</li><li>Mendy, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hepatitis+B+viral+load+and+risk+for+liver+cirrhosis+and+hepatocellular+carcinoma+in+the+Gambia,+West+Africa.">Hepatitis B viral load and risk for liver cirrhosis and hepatocellular carcinoma in the Gambia, West Africa.</a> Journal of Viral Hepatitis. 17 (2), 115-122 (2010).</li><li>Abe, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitation+of+Hepatitis+B+virus+genomic+DNA+by+real-time+detection+PCR.">Quantitation of Hepatitis B virus genomic DNA by real-time detection PCR.</a> Journal of Clinical Microbiology. 37 (9), 2899-2903 (1999).</li><li>Pas, S. D., Fries, E., De Man, R. A., Osterhaus, A. D., Niesters, H. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+a+quantitative+real-time+detection+assay+for+Hepatitis+B+virus+DNA+and+comparison+with+two+commercial+assays.">Development of a quantitative real-time detection assay for Hepatitis B virus DNA and comparison with two commercial assays.</a> Journal of Clinical Microbiology. 38 (8), 2897-2901 (2000).</li><li>Ronsin, C., Pillet, A., Bali, C., Denoyel, G. R. -. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evaluation+of+the+cobas+ampliprep-total+nucleic+acid+isolation-cobas+Taqman+Hepatitis+B+Virus+(HBV)+quantitative+test+and+comparison+to+the+versant+HBV+DNA+3.0+assay.">Evaluation of the cobas ampliprep-total nucleic acid isolation-cobas Taqman Hepatitis B Virus (HBV) quantitative test and comparison to the versant HBV DNA 3.0 assay.</a> Journal of Clinical Microbiology. 44 (4), 1390-1399 (2006).</li><li>Sum, S. S. M., Wong, D. K. H., Yuen, J. C. H., Lai, C. L., Yuen, M. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+the+cobas+taqman&#8482;+HBV+test+with+the+cobas+amplicor+monitor&#8482;+test+for+measurement+of+Hepatitis+B+virus+DNA+in+serum.">Comparison of the cobas taqman&#8482; HBV test with the cobas amplicor monitor&#8482; test for measurement of Hepatitis B virus DNA in serum.</a> Journal of Medical Virology. 77 (4), 486-490 (2005).</li><li>Lall, S., Choudhary, M. C., Mahajan, S., Kumar, G., Gupta, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Performance+evaluation+of+TRUPCR&#174;+HBV+real-time+PCR+assay+for+Hepatitis+B+virus+DNA+quantification+in+clinical+samples:+Report+from+a+tertiary+care+liver+centre.">Performance evaluation of TRUPCR&#174; HBV real-time PCR assay for Hepatitis B virus DNA quantification in clinical samples: Report from a tertiary care liver centre.</a> Virusdisease. 30 (2), 186-192 (2019).</li><li>Garg, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Presence+of+entry+receptors+and+viral+markers+suggest+a+low+level+of+placental+replication+of+Hepatitis+B+virus+in+a+proportion+of+pregnant+women+infected+with+chronic+Hepatitis+B.">Presence of entry receptors and viral markers suggest a low level of placental replication of Hepatitis B virus in a proportion of pregnant women infected with chronic Hepatitis B.</a> Scientific Reports. 12 (1), 17795 (2022).</li><li>NIBSC-Code:10/266. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Standard for Hepatitis B Virus (Hbv) DNA for Nucleic Acid Amplification Techniques (NAT). , (2016).</li><li>Kim, H., Hur, M., Bae, E., Lee, K. A., Lee, W. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Performance+evaluation+of+cobas+HBV+real-time+PCR+assay+on+Roche+cobas+4800+system+in+comparison+with+cobas+Ampliprep/cobas+Taqman+HBV+test.">Performance evaluation of cobas HBV real-time PCR assay on Roche cobas 4800 system in comparison with cobas Ampliprep/cobas Taqman HBV test.</a> Clinical Chemistry and Laboratory Medicine. 56 (7), 1133-1139 (2018).</li><li>Madihi, S., Syed, H., Lazar, F., Zyad, A., Benani, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Performance+comparison+of+the+artus+HBV+QS-RGQ+and+the+CAP/CTM+HBV+v2.0+assays+regarding+HEPATITIS+B+virus+DNA+quantification.">Performance comparison of the artus HBV QS-RGQ and the CAP/CTM HBV v2.0 assays regarding HEPATITIS B virus DNA quantification.</a> BioMed Research International. 2020, 4159189 (2020).</li><li>. Nibsc-14/198 Available from: <a target="_blank" href="https://www.nibsc.org/">https://www.nibsc.org/</a> (2023)</li><li>Guvenir, M., Arikan, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hepatitis+B+virus:+From+diagnosis+to+treatment.">Hepatitis B virus: From diagnosis to treatment.</a> Polish Journal of Microbiology. 69 (4), 391-399 (2020).</li></ol>

The authors are associated with Kilpest India Limited, the manufacturer of the HBV viral load kit used in this study.

NIBSC code 10/266 has been assigned a unit of 9,55,000 IU/mL when reconstituted in 0.5 mL of nuclease-free water as per the supplier information21. This can be considered a high-load HBV positive sample. The HBV viral load determined by the viral load kit used in this study was 6,65,900 IU/mL (Figure 4). As the DNA extraction efficiency of any DNA extraction kit is not 100%, some DNA is often lost during the purification process. Although the viral load determined by ...

Hepatitis B virus (HBV) is a partially double-stranded DNA virus from the genus Orthohepadnavirus and the Hepadnaviridae family1. It can trigger a chronic infection that persists throughout one&#39;s life, potentially leading to liver cirrhosis and hepatocellular carcinoma2,3,4. According to the World Health Organization (WHO), an estimated population of 296 million people were living with chronic hepatitis B infection in 2019, and 1.5 million people were newly infected each year5.
The identification and measurement of HBV DNA in serum or plasma samples serve as a valuable method for detecting individuals with an ongoing hepatitis B infection, assessing the efficacy of antiviral treatment, and predicting the probability of treatment success6,7,8,9,10,11. High viral load is associated with an increased risk of liver disease progression, including cirrhosis and liver cancer12,13. Hence, precise measurement of viral load is crucial for tracking the progression of HBV infection and informing decisions regarding treatment.
Quantitative real-time PCR assays have higher sensitivity, broader dynamic range, and more accurate quantification of HBV DNA than conventional PCR techniques14,15,16,17. Several commercial real-time PCR-based molecular diagnostic kits for the quantitation of HBV DNA in serum or plasma samples are available in the market. Here, we describe a detailed workflow for the detection and quantification of HBV DNA in human serum or plasma using a commercially available, IVD-marked real-time PCR-based kit. The kit is a widely used18,19, low-cost, yet highly sensitive assay, and its performance characteristics are comparable with other commercially available CE-marked kit(s)18. Apart from the HBV target region amplification, an endogenous internal control gene is also included in the kit to verify the quality of samples, quality of extracted DNA, PCR amplification, and possible PCR inhibition.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>4th WHO International Standard for hepatitis B virus DNA</td>
			<td>NIBSC</td>
			<td>NIBSC code: 10/266</td>
			<td>The 4th WHO International Standard for hepatitis B virus (HBV) DNA, NIBSC code 10/266, is intended to be used for the calibration of secondary reference reagents used in HBV nucleic acid amplification techniques (NAT).</td>
		</tr>
		<tr>
			<td>ABI real-time PCR machines&#160;</td>
			<td>ThermoFisher Scientific</td>
			<td>ABI 7500; QuantStudio 5</td>
			<td>This is a real time PCR machine&#160;</td>
		</tr>
		<tr>
			<td>HBV, HCV and HIV Multiplex 14/198</td>
			<td>NIBSC</td>
			<td>NIBSC code: 14/198</td>
			<td>This is a very low positive triplex reagent for NAT assays containing hepatitis B (HBV), hepatitis C (HCV) and human immunodeficiency virus-1 (HIV-1)</td>
		</tr>
		<tr>
			<td>QIAGEN real-time PCR machine</td>
			<td>Qiagen</td>
			<td>Rotor-Gene Q</td>
			<td>This is a real time PCR machine&#160;</td>
		</tr>
		<tr>
			<td>TRUPCR HBV Viral Load kit&#160;</td>
			<td>Kilpest India Limited</td>
			<td>3B294</td>
			<td>This is a real time PCR based kit used in this study for the HBV DNA detection and viral load determination</td>
		</tr>
		<tr>
			<td>TRUPCR Viral Nucleic Acid Extraction Kit</td>
			<td>Kilpest India Limited</td>
			<td>3B214</td>
			<td>This is a DNA extraction kit used for the extraction of HBV viral DNA from NIBSC:10/266 and NIBSC:14/198</td>
		</tr>
	</tbody>
</table>

real-time polymerase chain reaction-based detection and quantification of hepatitis b virus dna

Hepatitis B virus (HBV) is a significant cause of liver disease worldwide. It can lead to acute or chronic infections, making individuals highly susceptible to fatal cirrhosis and liver cancer. Accurate detection and quantification of HBV DNA in the blood are essential for diagnosing and monitoring HBV infection. The most common method for detecting HBV DNA is real-time PCR, which can be used to detect the virus and assess the viral load to monitor the response to antiviral therapy. Here, we describe a detailed protocol for the detection and quantification of HBV DNA in human serum or plasma using an IVD-marked real-time PCR-based kit. The kit uses primers and probes that target the highly conserved core region of the HBV genome and can accurately quantify all HBV genotypes (A, B, C, D, E, F, G, H, I, and J). The kit also includes an endogenous internal control to monitor possible PCR inhibition. This assay runs for 40 cycles, and its cutoff is 38 Ct. For the quantification of HBV DNA in clinical samples, a set of 5 quantification standards is provided with the kit. The standards contain known concentrations of HBV-specific DNA that are calibrated against the 4th WHO International Standard for HBV DNA for the nucleic acid test (NIBSC code 10/266). The standards are used to validate the functionality of the HBV-specific DNA amplification and to generate a standard curve, allowing the quantification of HBV DNA in a sample. HBV DNA as low as 2.5 IU/mL was detected using the PCR kit. The high sensitivity and reproducibility of the kit make it a powerful tool in clinical laboratories, aiding healthcare professionals in effectively diagnosing and managing HBV infections.

A schematic diagram of the workflow to detect and quantify HBV DNA from human plasma/serum is shown in Figure 1. An amplification plot of Standard 2 (used as a PC) and NTC for both HBV and IC is shown in Figure 2. Figure 3 shows the amplification curves for an HBV-positive sample, an HBV-negative sample, and a sample with PCR inhibition. The amplification curve, Ct value for HBV, and obtained HBV concentration in international units...

Watch this Scientific Journal Video about Advancements and Challenges in Hepatitis B Virus Detection at JoVE.com

Author Spotlight: Advancements and Challenges in Hepatitis B Virus Detection 

Real-time polymerase chain reaction (PCR)-based detection and quantification of hepatitis B virus (HBV) DNA is a sensitive and accurate method for diagnosing and monitoring HBV infection. Here, we present a protocol for HBV DNA detection and the viral load measurement of a sample.

Real-Time Polymerase Chain Reaction-Based Detection and Quantification of Hepatitis B Virus DNA

Hepatitis B virus (HBV) is a significant cause of liver disease worldwide. It can lead to acute or chronic infections, making individuals highly ...

real-time-polymerase-chain-reaction-based-detection-quantification

Research

JoVE Journal

Biology

2.8K Views.  3B BlackBio Biotech India Limited. Real-time polymerase chain reaction (PCR)-based detection and quantification of hepatitis B virus (HBV) DNA is a sensitive and accurate method for diagnosing and monitoring HBV infection. Here, we present a protocol for HBV DNA detection and the viral load measurement of a sample.

Video: Author Spotlight: Advancements and Challenges in Hepatitis B Virus Detection 

Combining QD-FRET and Microfluidics to Monitor DNA Nanocomplex Self-Assembly in Real-Time

Advances in genomics continue to fuel the development of therapeutics that can target pathogenesis at the cellular and molecular level. Typically functional inside the cell, nucleic acid-based therapeutics require an efficient intracellular delivery system. One widely adopted approach is to complex DNA with a gene carrier to form nanocomplexes via electrostatic self-assembly, facilitating cellular uptake of DNA while protecting it against degradation. The challenge lies in the rational design of efficient gene carriers, since premature dissociation or overly stable binding would be detrimental to the cellular uptake and therapeutic efficacy. Nanocomplexes synthesized by bulk mixing showed a diverse range of intracellular unpacking and trafficking behavior, which was attributed to the heterogeneity in size and stability of nanocomplexes. Such heterogeneity hinders the accurate assessment of the self-assembly kinetics and adds to the difficulty in correlating their physical properties to transfection efficiencies or bioactivities. We present a novel convergence of nanophotonics (i.e. QD-FRET) and microfluidics to characterize the real-time kinetics of the nanocomplex self-assembly under laminar flow. QD-FRET provides a highly sensitive indication of the onset of molecular interactions and quantitative measure throughout the synthesis process, whereas microfluidics offers a well-controlled microenvironment to spatially analyze the process with high temporal resolution (~milliseconds). For the model system of polymeric nanocomplexes, two distinct stages in the self-assembly process were captured by this analytic platform. The kinetic aspect of the self-assembly process obtained at the microscale would be particularly valuable for microreactor-based reactions which are relevant to many micro- and nano-scale applications. Further, nanocomplexes may be customized through proper design of microfludic devices, and the resulting QD-FRET polymeric DNA nanocomplexes could be readily applied for establishing structure-function relationships. 

We present a novel and powerful integration of nanophotonics (QD-FRET) and microfluidics to investigate the formation of polyelectrolyte polyplexes, which is expected to provide better control and synthesis of uniform and customizable polyplexes for future nucleic acid-based therapeutics.

Advances in genomics continue to fuel the development of therapeutics that can target pathogenesis at the cellular and molecular level. Typically ...

Chemically-blocked Antibody Microarray for Multiplexed High-throughput Profiling of Specific Protein Glycosylation in Complex Samples

In this study, we describe an effective protocol for use in a multiplexed high-throughput antibody microarray with glycan binding protein detection that allows for the glycosylation profiling of specific proteins. Glycosylation of proteins is the most prevalent post-translational modification found on proteins, and leads diversified modifications of the physical, chemical, and biological properties of proteins. Because the glycosylation machinery is particularly susceptible to disease progression and malignant transformation, aberrant glycosylation has been recognized as early detection biomarkers for cancer and other diseases. However, current methods to study protein glycosylation typically are too complicated or expensive for use in most normal laboratory or clinical settings and a more practical method to study protein glycosylation is needed. The new protocol described in this study makes use of a chemically blocked antibody microarray with glycan-binding protein (GBP) detection and significantly reduces the time, cost, and lab equipment requirements needed to study protein glycosylation. In this method, multiple immobilized glycoprotein-specific antibodies are printed directly onto the microarray slides and the N-glycans on the antibodies are blocked. The blocked, immobilized glycoprotein-specific antibodies are able to capture and isolate glycoproteins from a complex sample that is applied directly onto the microarray slides. Glycan detection then can be performed by the application of biotinylated lectins and other GBPs to the microarray slide, while binding levels can be determined using Dylight 549-Streptavidin. Through the use of an antibody panel and probing with multiple biotinylated lectins, this method allows for an effective glycosylation profile of the different proteins found in a given human or animal sample to be developed.
Introduction
Glycosylation of protein, which is the most ubiquitous post-translational modification on proteins, modifies the physical, chemical, and biological properties of a protein, and plays a fundamental role in various biological processes1-6. Because the glycosylation machinery is particularly susceptible to disease progression and malignant transformation, aberrant glycosylation has been recognized as early detection biomarkers for cancer and other diseases 7-12. In fact, most current cancer biomarkers, such as the L3 fraction of &alpha;-1 fetoprotein (AFP) for hepatocellular carcinoma 13-15, and CA199 for pancreatic cancer 16, 17 are all aberrant glycan moieties on glycoproteins. However, methods to study protein glycosylation have been complicated, and not suitable for routine laboratory and clinical settings. Chen et al. has recently invented a chemically blocked antibody microarray with a glycan-binding protein (GBP) detection method for high-throughput and multiplexed profile glycosylation of native glycoproteins in a complex sample 18. In this affinity based microarray method, multiple immobilized glycoprotein-specific antibodies capture and isolate glycoproteins from the complex mixture directly on the microarray slide, and the glycans on each individual captured protein are measured by GBPs. Because all normal antibodies contain N-glycans which could be recognized by most GBPs, the critical step of this method is to chemically block the glycans on the antibodies from binding to GBP. In the procedure, the cis-diol groups of the glycans on the antibodies were first oxidized to aldehyde groups by using NaIO4 in sodium acetate buffer avoiding light. The aldehyde groups were then conjugated to the hydrazide group of a cross-linker, 4-(4-N-MaleimidoPhenyl)butyric acid Hydrazide HCl (MPBH), followed by the conjugation of a dipeptide, Cys-Gly, to the maleimide group of the MPBH. Thus, the cis-diol groups on glycans of antibodies were converted into bulky none hydroxyl groups, which hindered the lectins and other GBPs bindings to the capture antibodies. This blocking procedure makes the GBPs and lectins bind only to the glycans of captured proteins. After this chemically blocking, serum samples were incubated with the antibody microarray, followed by the glycans detection by using different biotinylated lectins and GBPs, and visualized with Cy3-streptavidin. The parallel use of an antibody panel and multiple lectin probing provides discrete glycosylation profiles of multiple proteins in a given sample 18-20. This method has been used successfully in multiple different labs 1, 7, 13, 19-31. However, stability of MPBH and Cys-Gly, complicated and extended procedure in this method affect the reproducibility, effectiveness and efficiency of the method. In this new protocol, we replaced both MPBH and Cys-Gly with one much more stable reagent glutamic acid hydrazide (Glu-hydrazide), which significantly improved the reproducibility of the method, simplified and shorten the whole procedure so that the it can be completed within one working day. In this new protocol, we describe the detailed procedure of the protocol which can be readily adopted by normal labs for routine protein glycosylation study and techniques which are necessary to obtain reproducible and repeatable results.

In this study, we describe an improved protocol for a multiplexed high-throughput antibody microarray with lectin detection method that can be used in glycosylation profiling of specific proteins. This protocol features new reliable reagents and significantly reduces the time, cost, and lab equipment requirements as compared to the previous procedure.

 In this study, we describe an effective protocol for use in a multiplexed high-throughput antibody microarray with glycan binding protein detection that ...

Polymerase Chain Reaction: Basic Protocol Plus Troubleshooting and Optimization Strategies

In the biological sciences there have been technological advances that catapult the discipline into golden ages of discovery. For example, the field of microbiology was transformed with the advent of Anton van Leeuwenhoek&#39;s microscope, which allowed scientists to visualize prokaryotes for the first time. The development of the polymerase chain reaction (PCR) is one of those innovations that changed the course of molecular science with its impact spanning countless subdisciplines in biology. The theoretical process was outlined by Keppe and coworkers in 1971; however, it was another 14 years until the complete PCR procedure was described and experimentally applied by Kary Mullis while at Cetus Corporation in 1985. Automation and refinement of this technique progressed with the introduction of a thermal stable DNA polymerase from the bacterium Thermus aquaticus, consequently the name Taq DNA polymerase.
PCR is a powerful amplification technique that can generate an ample supply of a specific segment of DNA (i.e., an amplicon) from only a small amount of starting material (i.e., DNA template or target sequence). While straightforward and generally trouble-free, there are pitfalls that complicate the reaction producing spurious results. When PCR fails it can lead to many non-specific DNA products of varying sizes that appear as a ladder or smear of bands on agarose gels. Sometimes no products form at all. Another potential problem occurs when mutations are unintentionally introduced in the amplicons, resulting in a heterogeneous population of PCR products. PCR failures can become frustrating unless patience and careful troubleshooting are employed to sort out and solve the problem(s). This protocol outlines the basic principles of PCR, provides a methodology that will result in amplification of most target sequences, and presents strategies for optimizing a reaction. By following this PCR guide, students should be able to: 
 
&#9679; Set up reactions and thermal cycling conditions for a conventional PCR experiment 
&#9679; Understand the function of various reaction components and their overall effect on a PCR experiment 
&#9679; Design and optimize a PCR experiment for any DNA template 
&#9679; Troubleshoot failed PCR experiments

PCR has emerged as a common technique in many molecular biology laboratories. Provided here is a quick guide to several conventional PCR protocols. Because each reaction is a unique experiment, optimal conditions required to generate a product vary. Understanding the variables in a reaction will greatly enhance troubleshooting efficiency, thereby increasing the chance to obtain the desired result.

In the biological sciences there have been technological advances that catapult the discipline into golden ages of discovery. For example, the field of ...

Real-time Imaging of Single Engineered RNA Transcripts in Living Cells Using Ratiometric Bimolecular Beacons

The growing realization that both the temporal and spatial regulation of gene expression can have important consequences on cell function has led to the development of diverse techniques to visualize individual RNA transcripts in single living cells. One promising technique that has recently been described utilizes an oligonucleotide-based optical probe, ratiometric bimolecular beacon (RBMB), to detect RNA transcripts that were engineered to contain at least four tandem repeats of the RBMB target sequence in the 3&#8217;-untranslated region. RBMBs are specifically designed to emit a bright fluorescent signal upon hybridization to complementary RNA, but otherwise remain quenched. The use of a synthetic probe in this approach allows photostable, red-shifted, and highly emissive organic dyes to be used for imaging. Binding of multiple RBMBs to the engineered RNA transcripts results in discrete fluorescence spots when viewed under a wide-field fluorescent microscope. Consequently, the movement of individual RNA transcripts can be readily visualized in real-time by taking a time series of fluorescent images. Here we describe the preparation and purification of RBMBs, delivery into cells by microporation and live-cell imaging of single RNA transcripts.

Ratiometric bimolecular beacons (RBMBs) can be used to image single engineered RNA transcripts in living cells. Here, we describe the preparation and purification of RBMBs, delivery of RBMBs into cells by microporation and fluorescent imaging of single RNA transcripts in real-time.

The growing realization that both the temporal and spatial regulation of gene expression can have important consequences on cell function has led to the ...

Probe-based Real-time PCR Approaches for Quantitative Measurement of microRNAs

Probe-based quantitative PCR (qPCR) is a favoured method for measuring transcript abundance, since it is one of the most sensitive detection methods that provides an accurate and reproducible analysis. Probe-based chemistry offers the least background fluorescence as compared to other (dye-based) chemistries. Presently, there are several platforms available that use probe-based chemistry to quantitate transcript abundance. qPCR in a 96 well plate is the most routinely used method, however only a maximum of 96 samples or miRNAs can be tested in a single run. This is time-consuming and tedious if a large number of samples/miRNAs are to be analyzed. High-throughput probe-based platforms such as microfluidics (e.g. TaqMan Array Card) and nanofluidics arrays (e.g. OpenArray) offer ease to reproducibly and efficiently detect the abundance of multiple microRNAs in a large number of samples in a short time. Here, we demonstrate the experimental setup and protocol for miRNA quantitation from serum or plasma-EDTA samples, using probe-based chemistry and three different platforms (96 well plate, microfluidics and nanofluidics arrays) offering increasing levels of throughput.

Circulating microRNAs have recently emerged as promising and novel biomarkers for various cancers and other diseases. The goal of this article is to discuss three different probe-based real-time PCR platforms and methods that are available to quantify and determine the abundance of circulating microRNAs.

Probe-based quantitative PCR (qPCR) is a favoured method for measuring transcript abundance, since it is one of the most sensitive detection methods that ...

Dried Blood Spots - Preparing and Processing for Use in Immunoassays and in Molecular Techniques

The idea of collecting blood on a paper card and subsequently using the dried blood spots (DBS) for diagnostic purposes originated a century ago. Since then, DBS testing for decades has remained predominantly focused on the diagnosis of infectious diseases especially in resource-limited settings or the systematic screening of newborns for inherited metabolic disorders and only recently have a variety of new and innovative DBS applications begun to emerge. For many years, pre-analytical variables were only inappropriately considered in the field of DBS testing and even today, with the exception of newborn screening, the entire pre-analytical phase, which comprises the preparation and processing of DBS for their final analysis has not been standardized. Given this background, a comprehensive step-by-step protocol, which covers al the essential phases, is proposed, i.e., collection of blood; preparation of blood spots; drying of blood spots; storage and transportation of DBS; elution of DBS, and finally analyses of DBS eluates. The effectiveness of this protocol was first evaluated with 1,762 coupled serum/DBS pairs for detecting markers of hepatitis B virus, hepatitis C virus, and human immunodeficiency virus infections on an automated analytical platform. In a second step, the protocol was utilized during a pilot study, which was conducted on active drug users in the German cities of Berlin and Essen.

The preparing and processing of dried blood spots (DBS) for their final analysis are still poorly standardized for most diagnostic applications. To overcome this shortcoming, a comprehensive step-by-step protocol is suggested and subsequently evaluated with regard to its effectiveness for detecting markers of viral infections.

The idea of collecting blood on a paper card and subsequently using the dried blood spots (DBS) for diagnostic purposes originated a century ago. Since ...

Absolute Quantification of Plasma MicroRNA Levels in Cynomolgus Monkeys, Using Quantitative Real-time Reverse Transcription PCR

RT-qPCR is one of the most common methods to assess individual target miRNAs. MiRNAs levels are generally measured relative to a reference sample. This approach is appropriate for examining physiological changes in target gene expression levels. However, absolute quantification using better statistical analysis is preferable for a comprehensive assessment of gene expression levels. Absolute quantification is still not in common use. This report describes a protocol for measuring the absolute levels of plasma miRNA, using RT-qPCR with or without pre-amplification.
A fixed volume (200 &#181;L) of EDTA-plasma was prepared from the blood collected from the femoral vein of conscious cynomolgus monkeys (n = 50). Total RNA was extracted using commercially available system. Plasma miRNAs were quantified by probe-based RT-qPCR assays which contains miRNA-specific forward/reverse PCR primer and probe. Standard curves for absolute quantification were generated using commercially available synthetic RNA oligonucleotides. A synthetic cel-miR-238 was used as an external control for normalization and quality assessment. The miRNAs that showed quantification cycle (Cq) values above 35 were pre-amplified prior to the qPCR step.
Among the 8 miRNAs examined, miR-122, miR-133a, and miR-192 were detectable without pre-amplification, whereas miR-1, miR-206, and miR-499a required pre-amplification because of their low expression levels. MiR-208a and miR-208b were not detectable even after pre-amplification. Sample processing efficiency was evaluated by the Cq values of the spiked cel-miR-238. In this assay method, technical variation was estimated to be less than 3-fold and the lower limit of quantification (LLOQ) was 102 copy/&#181;L, for most of the examined miRNAs.
This protocol provides a better estimate of the quantity of plasma miRNAs, and allows quality assessment of corresponding data from different studies. Considering the low number of miRNAs in body fluids, pre-amplification is useful to enhance detection of poorly expressed miRNAs.

This report describes a protocol for measuring the absolute levels of plasma miRNA, using quantitative real-time reverse transcription PCR with or without pre-amplification. This protocol affords better understanding of the quantity of plasma miRNAs and allows qualitative assessment of corresponding data from different studies or laboratories.

RT-qPCR is one of the most common methods to assess individual target miRNAs. MiRNAs levels are generally measured relative to a reference sample. This ...

Isolation of Primary Patient-specific Aortic Smooth Muscle Cells and Semiquantitative Real-time Contraction Measurements In Vitro

Smooth muscle cells (SMCs) are the predominant cell type in the aortic media. Their contractile machinery is important for the transmission of force in the aorta and regulates vasoconstriction and vasodilation. Mutations in genes encoding for the SMC contractile apparatus proteins are associated with aortic diseases, such as thoracic aortic aneurysms. Measuring SMC contraction in vitro is challenging, especially in a high-throughput manner, which is essential for screening patient material. Currently available methods are not suitable for this purpose. This paper presents a novel method based on electric cell-substrate impedance sensing (ECIS). First, an explant protocol is described to isolate patient-specific human primary SMCs from aortic biopsies and patient-specific human primary dermal fibroblasts for the study of aortic aneurysms. Next, a detailed description of a new contraction method is given to measure the contractile response of these cells, including the subsequent analysis and suggestion for comparing different groups. This method can be used to study the contraction of adherent cells in the context of translational (cardiovascular) studies and patient and drug screening studies.

Isolation of Primary Patient-specific Aortic Smooth Muscle Cells and Semiquantitative Real-time Contraction Measurements In Vitro

This paper describes an explant culture-based method for the isolation and culturing of primary, patient-specific human aortic smooth muscle cells and dermal fibroblasts. Furthermore, a novel method is presented for measuring cell contraction and subsequent analysis, which can be used to study patient-specific differences in these cells.

Smooth muscle cells (SMCs) are the predominant cell type in the aortic media. Their contractile machinery is important for the transmission of force in ...

Real-Time Detection of Reactive Oxygen Species Production in Immune Response in Rice with a Chemiluminescence Assay

Reactive oxygen species (ROS) play vital roles in a variety of biological processes, including the sensing of abiotic and biotic stresses. Upon pathogen infection or challenge with pathogen-associated chemicals (pathogen-associated molecular patterns [PAMPs]), an array of immune responses, including a ROS burst, are quickly induced in plants, which is called PAMP-triggered immunity (PTI). A ROS burst is a hallmark PTI response, which is catalyzed by a group of plasma membrane-localized NADPH oxidases-the RBOH family proteins. The vast majority of ROS comprise hydrogen peroxide (H2O2), which can be easily and steadily detected by a luminol-based chemiluminescence method. Chemiluminescence is a photon-producing reaction in which luminol, or its derivative (such as L-012), undergoes a redox reaction with ROS under the action of a catalyst. This paper describes an optimized L-012-based chemiluminescence method to detect apoplast ROS production in real-time upon PAMP elicitation in rice tissues. The method is easy, steady, standardized, and highly reproducible under firmly controlled conditions.

Here, we describe a method for the real-time detection of apoplastic reactive oxygen species (ROS) production in rice tissues in pathogen-associated molecular pattern-triggered immune response. This method is simple, standardized, and generates highly reproducible results under controlled conditions.

Reactive oxygen species (ROS) play vital roles in a variety of biological processes, including the sensing of abiotic and biotic stresses. Upon pathogen ...

Real-Time Quantification of the Effects of IS200/IS605 Family-Associated TnpB on Transposon Activity

Here, a protocol is outlined to perform live, real-time imaging of transposable element activity in live bacterial cells using a suite of fluorescent reporters coupled to transposition. In particular, it demonstrates how real-time imaging can be used to assess the effects of the accessory protein TnpB on the activity of the transposable element IS608, a member of the IS200/IS605 family of transposable elements. The IS200/IS605 family of transposable elements are abundant mobile elements connected with one of the most innumerable genes found in nature, tnpB. Sequence homologies propose that the TnpB protein may be an evolutionary precursor to CRISPR/Cas9 systems. Additionally, TnpB has received renewed interest, having been shown to act as a Cas-like RNA-guided DNA endonuclease. The effects of TnpB on the transposition rates of IS608 are quantified, and it is demonstrated that the expression of TnpB of IS608 results in ~5x increased transposon activity compared to cells lacking TnpB expression.

A protocol is outlined to perform live real-time imaging to quantify how the accessory protein TnpB affects the dynamics of transposition in individual live Escherichia coli cells.

Here, a protocol is outlined to perform live, real-time imaging of transposable element activity in live bacterial cells using a suite of fluorescent ...