This work was supported by the Wuhan Science and Technology Plan Project (2018201261638501).

1. Mosquito sampling and sorting
<ol>
	<li>Trap the adult mosquitoes through the light traps MXA-02 or carbon dioxide mosquito traps in the field.</li>
	<li>Kill the collected mosquitoes by dipping in liquid nitrogen10,11. Transport them to the laboratory by the cold-chain logistics system12. 
	NOTE: Dry ice was primarily used in the cold-chain logistics system.</li>
	<li>(Optional) If the sample sites were near the lab, directly send the alive mosquitoes in the net traps to the laboratory and euthanize them by freezing at &#8804;-20 &#176;C for 30 min4.</li>
	<li>Make a morphological identification of the collected mosquitoes through the tool book13 for classification and identification of mosquitoes. 
	NOTE: If necessary, DNA barcoding could be used to classify and identify mosquitoes14,15.&#160;</li>
	<li>Based on sampling dates and sites, assign them into different pools,&#160;and then store&#160;them in 2-5&#160;mL tubes.</li>
	<li>Draw a table to record each tube with mosquito species, number, sampling code, date, and sites.</li>
	<li>Print the labels with sampling codes and attach them to the tubes.</li>
	<li>Keep tubes with the mosquito samples at -80 &#176;C until further analysis.</li>
</ol>
2. Mosquito grinding
<ol>
	<li>Place 20-50 mosquitoes into each 2 mL sterile tube with 3 mm ceramic beads with 1.5 mL of Roswell Park Memorial Institute (RPMI) medium containing 2% Penicillin-Streptomycin-Amphotericin B Solution. 
	NOTE: Keep the tubes on ice oron anice tray.</li>
	<li>Homogenize the mosquitoes with a low-temperature tissue homogenizer by grinding for 30 s at 70 Hz at 4 &#176;C for three cycles16.</li>
	<li>Centrifuge the mixtures at 15,000 &#215; g for 30 min at 4 &#176;C and transfer the supernatants to new tubes.</li>
	<li>Centrifuge the supernatants again at 15,000 &#215; g for 10 min at 4 &#176;C to remove the mosquito debris12,17. 
	NOTE: If necessary, the supernatants can be filtered using 0.22 &#956;m filters.</li>
	<li>Aliquot the supernatants (P0) into 2 mL screw cap storage tubes (200 &#181;L per tube) and store them at -80 &#176;C.</li>
</ol>
3. Preparation of cells and cell culture maintenance medium
NOTE: Mosquito cell line C6/36 (Aedes albopictus RNAi-deficient) and vertebrate cell line BHK-21 (baby hamster kidney) were used for the virus amplification and isolation.
<ol>
	<li>Inoculate 1 &#215; 106 C6/36 cells into a 75 cm2 flask with 10 mL of RPMI medium supplemented with 10% fetal bovine serum (FBS) and 1% penicillin/streptomycin (P/S) at 28 &#176;C in a 5% CO2 humidified incubator.</li>
	<li>Inoculate 1 &#215; 106 BHK-21 cells into a 75 cm2 flask with 10 mL of Dulbecco&#39;s modified Eagle medium (DMEM) supplemented with 10% FBS and 1% P/S at 37 &#176;C in a 5% CO2 humidified incubator. 
	NOTE: The cells were passaged two or three times per week17,18.</li>
	<li>Seed the cells cultured in a 75 cm2 flask (C6/36 or BHK-21 cells) into the 24-well plates (C6/36 per well: 1.4 &#215; 105; BHK-21 per well: 0.8 &#215; 105).</li>
	<li>Place the 24-well plates at 28 &#176;C or 37 &#176;C overnight.</li>
	<li>Observe the cells under the microscope and confirm whether cell confluency in each well is 80%-90%.</li>
	<li>Prepare the cell culture maintenance medium (500 mL). 
	&#8203;NOTE: For C6/36, the medium was RPMI medium supplemented with 2% FBS and 2% Penicillin-Streptomycin-Amphotericin B Solution. For BHK-21, the medium was DMEM medium supplemented with 2% FBS and 2% Penicillin-Streptomycin-Amphotericin B Solution.</li>
</ol>
4. Virus isolation
NOTE: All steps were carried out in a biosafety level 2 (BSL-2) laboratory. The safety level requirement of the biosafety laboratory was determined by the biosafety risk assessment based on the regulations of different countries and regions. The process must be performed in a biosafety cabinet.
<ol>
	<li>Remove the cell culture medium from the 24-well plates and add 100 &#181;L of the cell culture maintenance medium and 100 &#181;L of the supernatant of the mosquito homogenate (P0) to each well.</li>
	<li>Incubate the plates at 28 &#176;C or 37 &#176;C for 60 min and gently shake them every 15 min to prevent cell drying.</li>
	<li>Remove the supernatant and rinse each well gently with 600 &#181;L of cell culture maintenance medium to remove the debris completely.</li>
	<li>Add 800 &#181;L of cell culture maintenance medium to each well and keep the plates in a 5% CO2 humidified incubator at 28 &#176;C or 37 &#176;C for 7 days.</li>
	<li>Monitor the cell state of each well under the microscope daily15.</li>
	<li>Collect the supernatants of cells (P1 supernatants) on the 7th day and store the supernatants at -80 &#176;C.</li>
	<li>Repeat steps 4.1-4.6 2x to get P2 and P3 supernatants. 
	NOTE: In step 4.3, rinsing each well gently with 600 &#181;L of cell culture maintenance medium was optional for the P2 and P3.</li>
	<li>Depending on which well shows the cytopathogenic effect (CPE) &#160;&#8212;&#160;cells die, pyknosis,&#160;and detach from the surface; fusion with adjacent cells to form syncytia; or the appearance of nuclear or cytoplasmic inclusion bodies &#8212; add 300-400 &#181;L of the supernatant of this CPE well into each well of the new 6-well plates containing cells (the cell confluency was 80%-90%) to greatly amplify the viruses.</li>
	<li>Collect the supernatants and aliquot them into 2 mL screw cap storage tubes (500 &#181;L per tube). Store them at -80 &#176;C. 
	&#8203;NOTE: After three generations of successive passaging in cells, the samples that did not induce CPE were discarded. If necessary, the generations of successive passaging in cells can be increased.</li>
</ol>
5. Detecting viral sequences by RT-PCR
<ol>
	<li>Extract total RNA from 200 &#181;L of the viral supernatant using a viral RNA mini kit16. 
	NOTE: Here, anautomated nucleic acid extraction system was used to extract total RNA following the instrument manufacturer&#39;s instructions.</li>
	<li>Convert the RNA to cDNA following the RT-PCR kit instructions using a PCR instrument.
	<ol>
		<li>Add 15 &#181;L of RNA mixed with 1 &#181;L of random primers into the PCR tube. Place the tube at 70 &#176;C for 5 min and then place it on ice for 5 min.</li>
		<li>Add 5 &#181;L of 5x buffer and 25 &#181;L of mixture (10 mM dNTP, 40 U/&#181;L RNase inhibitor, and 200 U/&#181;L M-MLV) into the tube and place the tube at 42 &#176;C for 60 min and 95 &#176;C for 10 min.</li>
		<li>Store the tube at -20 &#176;C.</li>
	</ol>
	</li>
	<li>Use a PCR kit and universal primers (Table 1) to detect viruses by PCR.
	<ol>
		<li>For arboviruses, set up the PCR reaction system (total 30 &#181;L) with the following components: 3 &#181;L of 10x Taq buffer, 3 &#181;L of dNTP (1mM), 1 &#181;L of forward primer (10 &#181;m), 1 &#181;L of reverse primer (10 &#181;m), 0.3 &#181;L of Taq (10 U/&#181;L), 19.7 &#181;L of ddH2O, and 2 &#181;L of cDNA.</li>
		<li>For the detection of flaviviruses, set up the reaction process as: stage 1: 35 cycles of 94 &#176;C for 30 s, 52 &#176;C for 30 s, and 72 &#176;C for 30 s; stage 2: 72 &#176;C for 10 min.</li>
		<li>For the detection of alphaviruses, set up the reaction process as: stage 1: 35 cycles of 94 &#176;C for 30 s, 50 &#176;C for 30 s, and 72 &#176;C for 30 s; stage 2: 72 &#176;C for 10 min.</li>
		<li>For the detection of bunyaviruses, set up the reaction process as: stage 1: 35 cycles of 94 &#176;C for 30 s, 50 &#176;C for 30 s, and 72 &#176;C for 30 s; stage 2: 72 &#176;C for 10 min.</li>
	</ol>
	</li>
	<li>Detect the PCR amplification products by 1% agarose gel electrophoresis and send them for sequencing analysis. 
	NOTE: If conditions permit, the supernatants can be undergo next generation sequencing analysis to identfy new viruses and obtain the whole viral genome seqeunces.</li>
</ol>

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The authors have no conflicts of interest to disclose.

The objective of this method was to offer a practical way for isolating mosquito-associated viruses using various cell lines. It is critical to add the Antibiotic-Antimycotic (Penicillin-Streptomycin-Amphotericin) to the supernatants of the mosquito homogenates to avoid contamination by bacteria or fungi. Mosquitoes and viral supernatants obtained in the field must be refrigerated at -80 &#176;C to avoid repeated freeze-thaw cycles.
Another critical step in the protocol was grinding. Mosquito ...

Mosquitoes are a group of important pathogenic arthropod vectors. There are approximately 3,500 species of mosquitoes in the family Culicidae1,2. The development of high-throughput sequencing technologies has led to the discovery of many novel, virus-like sequences in mosquitoes from different parts of the world3. Generally, these mosquito-associated viruses can be classified into two main groups: MBVs and MSVs.
MBVs are a group of diverse viruses that are causative agents of many human or animal illnesses, such as yellow fever virus (YFV), dengue virus (DENV), Japanese encephalitis virus (JEV), West Nile virus (WNV), and Rift Valley fever virus (RVFV)4. They have seriously threatened public health by causing severe morbidity and mortality in both humans and animals across the world. MBVs naturally sustain a life cycle between diverse hosts through transmission from an infected mosquito to a na&#239;ve host, as well as from a virus-infected host and to a feeding mosquito5. Therefore, these viruses can infect both mosquito cell lines and vertebrate cell lines in the lab1.
MSVs, which include Yichang virus (YCN), Culex flavivirus (CxFV), and Chaoyang virus (CHAOV), are a subgroup of insect-specific viruses1,6,7. In recent years, there has been a rise in the discovery of novel MSVs, and some of these MSVs have been found to have an impact on the transmission of MBVs. For example, CxFV, which can be a persistent infection in Culex pipiens, could suppress WNV replication at an early stage8. Another insect-specific flavivirus, cell-fusing agent virus (CFAV), has been found to inhibit the propagation of DENV and Zika virus (ZIKV) in Aedes aegypti mosquitoes9. Thus, this protocol is a useful approach for isolating mosquito-associated viruses and can help in further research into the distribution of pathogens related to mosquitoes and the control of mosquito-borne diseases.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>0.22 &#181;m membrane filter</td>
			<td>Millipore</td>
			<td>SLGP033RB</td>
			<td>Polymer films with specific pore ratings.To remove cell debris and bacteria.</td>
		</tr>
		<tr>
			<td>24-well plates</td>
			<td>CORNING</td>
			<td>3524</td>
			<td>Containers for cell</td>
		</tr>
		<tr>
			<td>75 cm2 flasks</td>
			<td>CORNING</td>
			<td>430641</td>
			<td>Containers for cell</td>
		</tr>
		<tr>
			<td>a sterile 2 mL tube with 3 mm ceramic beads</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Antibiotic-Antimycotic</td>
			<td>Gibco</td>
			<td>15240-062</td>
			<td>Antibiotic in the medium to prevent contamination from bacteria and fungi</td>
		</tr>
		<tr>
			<td>Automated nucleic acid extraction system</td>
			<td>NanoMagBio</td>
			<td>S-48</td>
			<td></td>
		</tr>
		<tr>
			<td>BHK-21 cells</td>
			<td>National Virus Resource Center, Wuhan Institute of Virology</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>C6/36 cells</td>
			<td>National Virus Resource Center, Wuhan Institute of Virology</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifugal machine</td>
			<td>Himac</td>
			<td>CF16RN</td>
			<td>Instrument for centrifugation of mosquito samples</td>
		</tr>
		<tr>
			<td>CO2</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#8217;s minimal essential medium (DMEM)</td>
			<td>Gibco</td>
			<td>C11995500BT</td>
			<td>medium for vertebrate cell lines</td>
		</tr>
		<tr>
			<td>Ebinur Lake virus</td>
			<td></td>
			<td></td>
			<td>Cu20-XJ isolation</td>
		</tr>
		<tr>
			<td>Feta Bovine Serum (FBS)</td>
			<td>Gibco</td>
			<td>10099141C</td>
			<td> 
			 
			Provide nutrition for cells</td>
		</tr>
		<tr>
			<td>high-speed low-temperature tissue homogenizer</td>
			<td>servicebio</td>
			<td>KZ-III-F</td>
			<td>Instrument for grinding</td>
		</tr>
		<tr>
			<td>incubator (28 &#176;C)</td>
			<td>Panasonic</td>
			<td>MCO-18AC</td>
			<td>Instrument for cell culture</td>
		</tr>
		<tr>
			<td>incubator (37 &#176;C)</td>
			<td>Panasonic</td>
			<td>MCO-18AC</td>
			<td>Instrument for cell culture</td>
		</tr>
		<tr>
			<td>PCR tube</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>penicillin-streptomycin</td>
			<td>Gibco</td>
			<td>15410-122</td>
			<td>Antibiotic in the medium to prevent contamination from bacteria</td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin-Amphotericin B Solution</td>
			<td>Gibco</td>
			<td>15240096</td>
			<td></td>
		</tr>
		<tr>
			<td>Refrigerator (-80 &#176;C)</td>
			<td>sanyo</td>
			<td>MDF-U54V</td>
			<td></td>
		</tr>
		<tr>
			<td>Roswell Park Memorial Institute&#160; medium (RPMI)</td>
			<td>Gibco</td>
			<td>C11875500BT</td>
			<td>medium for mosiquto cell lines</td>
		</tr>
		<tr>
			<td>Screw cap storage tubes (2 mL)</td>
			<td>biofil</td>
			<td>&#160;FCT010005</td>
			<td></td>
		</tr>
		<tr>
			<td>sterile pestles</td>
			<td>Tiangen</td>
			<td>OSE-Y004</td>
			<td>Consumables&#160; for grinding</td>
		</tr>
		<tr>
			<td>TGrinder OSE-Y30 electric tissue grinder</td>
			<td>Tiangen</td>
			<td>OSE-Y30</td>
			<td>Instrument for grinding</td>
		</tr>
		<tr>
			<td>The dissecting microscope</td>
			<td>ZEISS</td>
			<td>stemi508</td>
			<td></td>
		</tr>
		<tr>
			<td>the light traps MXA-02</td>
			<td>Maxttrac</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>The mosquito absorbing machine</td>
			<td>Ningbo Bangning</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>The pipette tips</td>
			<td>Axygen</td>
			<td>TF</td>
			<td></td>
		</tr>
		<tr>
			<td>The QIAamp viral RNA mini kit</td>
			<td>QIAGEN</td>
			<td>52906</td>
			<td></td>
		</tr>
		<tr>
			<td>Tweezers</td>
			<td>Dumont</td>
			<td>0203-5-PO</td>
			<td></td>
		</tr>
	</tbody>
</table>

mosquito-associated virus isolation from field-collected mosquitoes

With the broad application of sequencing technologies, many novel virus-like sequences have been discovered in arthropods, including mosquitoes. The two main categories of these new mosquito-associated viruses are &#34;mosquito-borne viruses (MBVs)&#34; and &#34;mosquito-specific viruses (MSVs)&#34;. These novel viruses might be pathogenic to both vertebrates and mosquitoes, or they could just be symbiotic with mosquitoes. Entity viruses are essential to confirm the biological characters of these viruses. Thus, a detailed protocol has been described here for virus isolation and amplification from field-collected mosquitoes. First, the mosquito samples were prepared as supernatants of mosquito homogenates. After centrifugation twice, the supernatants were then inoculated into either mosquito cell line C6/36 or vertebrate cell line BHK-21 for virus amplification. After 7 days, the supernatants were collected as the P1 supernatants and stored at -80 &#176;C. Next, P1 supernatants were passaged twice more in C6/36 or BHK-21 cells while the cell status was being checked daily. When cytopathogenic effect (CPE) on the cells was discovered, these supernatants were collected and used to identify viruses. This protocol serves as the foundation for future research on mosquito-associated viruses, including MBVs and MSVs.

After inoculation with the supernatants of the mosquito homogenates (P0), the C6/36 cells exhibited a wide intercellular space, and exfoliated cells were observed at 120 h (Figure 1A) compared to the uninoculated cells (control) at the same time (Figure 1B). After incubating the BHK-21 cells with the P3 supernatants, visible CPE was observed in the BHK-21 cells at 48 h (Figure 1C) in contrast to the control cells (<strong class="xfi...

Watch this Scientific Journal Video about Mosquito-Associated Virus Isolation from Field-Collected Mosquitoes at JoVE.com

Mosquito-Associated Virus Isolation from Field-Collected Mosquitoes

Numerous novel virus-like sequences have been found in mosquitoes due to the extensive use of sequencing technologies. We provide an effective procedure for isolating and amplifying viruses using vertebrate and mosquito cell lines, which might serve as the basis for future studies on mosquito-associated viruses, including mosquito-borne and mosquito-specific viruses.

With the broad application of sequencing technologies, many novel virus-like sequences have been discovered in arthropods, including mosquitoes. The two ...

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Research

JoVE Journal

Biology

1.7K Views.  Chinese Academy of Sciences. Numerous novel virus-like sequences have been found in mosquitoes due to the extensive use of sequencing technologies. We provide an effective procedure for isolating and amplifying viruses using vertebrate and mosquito cell lines, which might serve as the basis for future studies on mosquito-associated viruses, including mosquito-borne and mosquito-specific viruses.

Video: Mosquito-Associated Virus Isolation from Field-Collected Mosquitoes

Dissection of Midgut and Salivary Glands from Ae. aegypti Mosquitoes

The mosquito midgut and salivary glands are key entry and exit points for pathogens such as Plasmodium parasites and Dengue viruses. This video protocol demonstrates dissection techniques for removal of the midgut and salivary glands from Aedes aegypti mosquitoes. 



The mosquito midgut and salivary glands are key entry and exit points for vector pathogens like Plasmodium falciparum and the dengue virus. This video demonstrates the dissection techniques for removing the midgut and salivary glands from Aedes aegypti mosquitoes.

The mosquito midgut and salivary glands are key entry and exit points for pathogens such as Plasmodium parasites and Dengue viruses. This video protocol ...

Isolation of Genomic DNA from Mouse Tails

Mitochondrial Isolation from Skeletal Muscle

Mitochondria are organelles controlling the life and death of the cell. They participate in key metabolic reactions, synthesize most of the ATP, and regulate a number of signaling cascades2,3. Past and current researchers have isolated mitochondria from rat and mice tissues such as liver, brain and heart4,5. In recent years, many researchers have focused on studying mitochondrial function from skeletal muscles.
Here, we describe a method that we have used successfully for the isolation of mitochondria from skeletal muscles 6. Our procedure requires that all buffers and reagents are made fresh and need about 250-500 mg of skeletal muscle. We studied mitochondria isolated from rat and mouse gastrocnemius and diaphragm, and rat extraocular muscles. Mitochondrial protein concentration is measured with the Bradford assay. It is important that mitochondrial samples be kept ice-cold during preparation and that functional studies be performed within a relatively short time (~1 hr). Mitochondrial respiration is measured using polarography with a Clark-type electrode (Oxygraph system) at 37&deg;C7. Calibration of the oxygen electrode is a key step in this protocol and it must be performed daily. Isolated mitochondria (150 &mu;g) are added to 0.5 ml of experimental buffer (EB). State 2 respiration starts with addition of glutamate (5mM) and malate (2.5 mM). Then, adenosine diphosphate (ADP) (150 &mu;M) is added to start state 3. Oligomycin (1 &mu;M), an ATPase synthase blocker, is used to estimate state 4. Lastly, carbonyl cyanide p-[trifluoromethoxy]-phenyl-hydrazone (FCCP, 0.2 &mu;M) is added to measurestate 5, or uncoupled respiration 6. The respiratory control ratio (RCR), the ratio of state 3 to state 4, is calculated after each experiment. An RCR &ge;4 is considered as evidence of a viable mitochondria preparation.
In summary, we present a method for the isolation of viable mitochondria from skeletal muscles that can be used in biochemical (e.g., enzyme activity, immunodetection, proteomics) and functional studies (mitochondrial respiration).

This protocol describes a procedure to study the respiration of mitochondria isolated from skeletal muscles. This method was adapted from Scorrano et al. (2007). The mitochondrial isolation procedure requires about 2 hours. The mitochondrial respiration can be completed in about 1 hour.

Mitochondria are organelles controlling the life and death of the cell. They participate in key metabolic reactions, synthesize most of the ATP, and ...

Isolation and Purification of Kinesin from Drosophila Embryos

Motor proteins move cargos along microtubules, and transport them to specific sub-cellular locations. Because altered transport is suggested to underlie a variety of neurodegenerative diseases, understanding microtubule based motor transport and its regulation will likely ultimately lead to improved therapeutic approaches. Kinesin-1 is a eukaryotic motor protein which moves in an anterograde (plus-end) direction along microtubules (MTs), powered by ATP hydrolysis. Here we report a detailed purification protocol to isolate active full length kinesin from Drosophila embryos, thus allowing the combination of Drosophila genetics with single-molecule biophysical studies. Starting with approximately 50 laying cups, with approximately 1000 females per cup, we carried out overnight collections. This provided approximately 10 ml of packed embryos. The embryos were bleach dechorionated (yielding approximately 9 grams of embryos), and then homogenized. After disruption, the homogenate was clarified using a low speed spin followed by a high speed centrifugation. The clarified supernatant was treated with GTP and taxol to polymerize MTs. Kinesin was immobilized on polymerized MTs by adding the ATP analog, 5'-adenylyl imidodiphosphate at room temperature. After kinesin binding, microtubules were sedimented via high speed centrifugation through a sucrose cushion. The microtubule pellet was then re-suspended, and this process was repeated. Finally, ATP was added to release the kinesin from the MTs. High speed centrifugation then spun down the MTs, leaving the kinesin in the supernatant. This kinesin was subjected to a centrifugal filtration using a 100 KD cut off filter for further purification, aliquoted, snap frozen in liquid nitrogen, and stored at -80 &deg;C. SDS gel electrophoresis and western blotting was performed using the purified sample. The motor activity of purified samples before and after the final centrifugal filtration step was evaluated using an in vitro single molecule microtubule assay. The kinesin fractions before and after the centrifugal filtration showed processivity as previously reported in literature. Further experiments are underway to evaluate the interaction between kinesin and other transport related proteins.

Isolation and Purification of Kinesin from Drosophila Embryos

This is a protocol to isolate active full length Kinesin from Drosophila embryos for single-molecule biophysical studies. We show how to collect embryos, make the embryo lysate, and then polymerize microtubules (MTs). Kinesin is purified by immobilizing it on the MTs, spinning down the Kinesin-MT complexes, and then releasing the kinesin from the MTs via ATP addition.

Motor proteins move cargos along microtubules, and transport them to specific sub-cellular locations. Because altered transport is suggested to underlie a ...

Isolation of Immune Cells from Primary Tumors

Tumors create a unique immunosuppressive microenvironment (tumor microenvironment, TME) whereby leukocytes are recruited into the tumor by various chemokines and growth factors 1,2. However, once in the TME, these cells lose the ability to promote anti-tumor immunity and begin to support tumor growth and down-regulate anti-tumor immune responses 3-4. Studies on tumor-associated leukocytes have mainly focused on cells isolated from tumor-draining lymph nodes or spleen due to the inherent difficulties in obtaining sufficient cell numbers and purity from the primary tumor. While identifying the mechanisms of cell activation and trafficking through the lymphatic system of tumor bearing mice is important and may give insight to the kinetics of immune responses to cancer, in our experience, many leukocytes, including dendritic cells (DCs), in tumor-draining lymph nodes have a different phenotype than those that infiltrate tumors 5,6 . Furthermore, we have previously demonstrated that adoptively-transferred T cells isolated from the tumor-draining lymph nodes are not tolerized and are capable of responding to secondary stimulation in vitro unlike T cells isolated from the TME, which are tolerized and incapable of proliferation or cytokine production 7,8. Interestingly, we have shown that changing the tumor microenvironment, such as providing CD4+ T helper cells via adoptive transfer, promotes CD8+ T cells to maintain pro-inflammatory effector functions 5. The results from each of the previously mentioned studies demonstrate the importance of measuring cellular responses from TME-infiltrating immune cells as opposed to cells that remain in the periphery. To study the function of immune cells which infiltrate tumors using the Miltenyi Biotech isolation system9, we have modified and optimized this antibody-based isolation procedure to obtain highly enriched populations of antigen presenting cells and tumor antigen-specific cytotoxic T lymphocytes. The protocol includes a detailed dissection of murine prostate tissue from a spontaneous prostate tumor model (TRansgenic Adenocarcinoma of the Mouse Prostate -TRAMP) 10 and a subcutaneous melanoma (B16) tumor model followed by subsequent purification of various leukocyte populations.

In this report, we describe a protocol for isolating highly purified populations of leukocytes that infiltrate tumors. This protocol is adapted from the Miltenyi Biotech protocol to enhance yield and purity for isolating cells from complex tumor tissue.

Tumors create a unique immunosuppressive microenvironment (tumor microenvironment, TME) whereby leukocytes are recruited into the tumor by various ...

The MultiBac Protein Complex Production Platform at the EMBL

Proteomics research revealed the impressive complexity of eukaryotic proteomes in unprecedented detail. It is now a commonly accepted notion that proteins in cells mostly exist not as isolated entities but exert their biological activity in association with many other proteins, in humans ten or more, forming assembly lines in the cell for most if not all vital functions.1,2 Knowledge of the function and architecture of these multiprotein assemblies requires their provision in superior quality and sufficient quantity for detailed analysis. The paucity of many protein complexes in cells, in particular in eukaryotes, prohibits their extraction from native sources, and necessitates recombinant production. The baculovirus expression vector system (BEVS) has proven to be particularly useful for producing eukaryotic proteins, the activity of which often relies on post-translational processing that other commonly used expression systems often cannot support.3 BEVS use a recombinant baculovirus into which the gene of interest was inserted to infect insect cell cultures which in turn produce the protein of choice. MultiBac is a BEVS that has been particularly tailored for the production of eukaryotic protein complexes that contain many subunits.4 A vital prerequisite for efficient production of proteins and their complexes are robust protocols for all steps involved in an expression experiment that ideally can be implemented as standard operating procedures (SOPs) and followed also by non-specialist users with comparative ease. The MultiBac platform at the European Molecular Biology Laboratory (EMBL) uses SOPs for all steps involved in a multiprotein complex expression experiment, starting from insertion of the genes into an engineered baculoviral genome optimized for heterologous protein production properties to small-scale analysis of the protein specimens produced.5-8 The platform is installed in an open-access mode at EMBL Grenoble and has supported many scientists from academia and industry to accelerate protein complex research projects.

Protein complexes catalyze key cellular functions. Detailed functional and structural characterization of many essential complexes requires recombinant production. MultiBac is a baculovirus/insect cell system particularly tailored for expressing eukaryotic proteins and their complexes. MultiBac was implemented as an open-access platform, and standard operating procedures developed to maximize its utility.

Proteomics  research revealed the impressive complexity of eukaryotic proteomes in  unprecedented detail. It is now a commonly accepted notion that ...

Isolation of Small Noncoding RNAs from Human Serum

The analysis of RNA and its expression is a common feature in many laboratories. Of significance is the emergence of small RNAs like microRNAs, which are found in mammalian cells. These small RNAs are potent gene regulators controlling vital pathways such as growth, development and death and much interest has been directed at their expression in bodily fluids. This is due to their dysregulation in human diseases such as cancer and their potential application as serum biomarkers. However, the analysis of miRNA expression in serum may be problematic. In most cases the amount of serum is limiting and serum contains low amounts of total RNA, of which small RNAs only constitute 0.4-0.5%1. Thus the isolation of sufficient amounts of quality RNA from serum is a major challenge to researchers today. In this technical paper, we demonstrate a method which uses only 400 &#181;l of human serum to obtain sufficient RNA for either DNA arrays or qPCR analysis. The advantages of this method are its simplicity and ability to yield high quality RNA. It requires no specialized columns for purification of small RNAs and utilizes general reagents and hardware found in common laboratories. Our method utilizes a Phase Lock Gel to eliminate phenol contamination while at the same time yielding high quality RNA. We also introduce an additional step to further remove all contaminants during the isolation step. This protocol is very effective in isolating yields of total RNA of up to 100 ng/&#181;l from serum but can also be adapted for other biological tissues.

This protocol describes a method for extracting small RNAs from human serum. We have used this method to isolate microRNAs from cancer serum for use in DNA arrays and also singleplex quantitative PCR. The protocol utilizes phenol and guanidinium thiocyanate reagents with modifications to yield high quality RNA.

The analysis of RNA and its expression is a common feature in many laboratories. Of significance is the emergence of small RNAs like microRNAs, which are ...

A Multi-detection Assay for Malaria Transmitting Mosquitoes

The Anopheles gambiae species complex includes the major malaria transmitting mosquitoes in Africa. Because these species are of such medical importance, several traits are typically characterized using molecular assays to aid in epidemiological studies. These traits include species identification, insecticide resistance, parasite infection status, and host preference. Since populations of the Anopheles gambiae complex are morphologically indistinguishable, a polymerase chain reaction (PCR) is traditionally used to identify species. Once the species is known, several downstream assays are routinely performed to elucidate further characteristics. For instance, mutations known as KDR in a para gene confer resistance against DDT and pyrethroid insecticides. Additionally, enzyme-linked immunosorbent assays (ELISAs) or Plasmodium parasite DNA detection PCR assays are used to detect parasites present in mosquito tissues. Lastly, a combination of PCR and restriction enzyme digests can be used to elucidate host preference (e.g., human vs. animal blood) by screening the mosquito bloodmeal for host-specific DNA. We have developed a multi-detection assay (MDA) that combines all of the aforementioned assays into a single multiplex reaction genotyping 33SNPs for 96 or 384 samples at a time. Because the MDA includes multiple markers for species, Plasmodium detection, and host blood identification, the likelihood of generating false positives or negatives is greatly reduced from previous assays that include only one marker per trait. This robust and simple assay can detect these key mosquito traits cost-effectively and in a fraction of the time of existing assays.

Malaria transmitting mosquitoes have a number of epidemiologically important characteristics that can only be detected using molecular techniques. Utilizing a MALDI-TOF based SNP genotyping platform, we developed an assay for simultaneously detecting multiple key traits (species, insecticide resistance, parasite infection and host choice) of malaria vectors.

The Anopheles gambiae species complex includes the major malaria transmitting mosquitoes in Africa. Because these species are of such medical importance, ...

Isolation of High Quality Murine Atrial and Ventricular Myocytes for Simultaneous Measurements of Ca2+ Transients and L-Type Calcium Current

Mouse models play a crucial role in arrhythmia research and allow studying key mechanisms of arrhythmogenesis including altered ion channel function and calcium handling. For this purpose, atrial or ventricular cardiomyocytes of high quality are necessary to perform patch-clamp measurements or to explore calcium handling abnormalities. However, the limited yield of high-quality cardiomyocytes obtained by current isolation protocols does not allow both measurements in the same mouse. This article describes a method to isolate high-quality murine atrial and ventricular myocytes via retrograde enzyme-based Langendorff perfusion, for subsequent simultaneous measurements of calcium transients and L-type calcium current from one animal. Mouse hearts are obtained, and the aorta is rapidly cannulated to remove blood. Hearts are then initially perfused with a calcium-free solution (37 &#176;C) to dissociate the tissue at the level of intercalated discs and afterwards with an enzyme solution containing little calcium to disrupt extracellular matrix (37 &#176;C). The digested heart is subsequently dissected into atria and ventricles. Tissue samples are chopped into small pieces and dissolved by carefully pipetting up and down. The enzymatic digestion is stopped, and cells are stepwise reintroduced to physiologic calcium concentrations. After loading with a fluorescent Ca2+-indicator, isolated cardiomyocytes are prepared for simultaneous measurement of calcium currents and transients. Additionally, isolation pitfalls are discussed and patch-clamp protocols and representative traces of L-type calcium currents with simultaneous calcium transient measurements in atrial and ventricular murine myocytes isolated as described above are provided.

Isolation of High Quality Murine Atrial and Ventricular Myocytes for Simultaneous Measurements of Ca2+ Transients and L-Type Calcium Current

Mouse models allow studying key mechanisms of arrhythmogenesis. For this purpose, high quality cardiomyocytes are necessary to perform patch-clamp measurements. Here, a method to isolate murine atrial and ventricular myocytes via retrograde enzyme-based Langendorff perfusion, which allows simultaneous measurements of calcium-transients and L-type calcium current, is described.

Mouse models play a crucial role in arrhythmia research and allow studying key mechanisms of arrhythmogenesis including altered ion channel function and ...

Chromatin Extraction from Frozen Chimeric Liver Tissue for Chromatin Immunoprecipitation Analysis

Crosslinking Chromatin Immunoprecipitation (X-ChIP) is a widely used technique to assess levels of histone marks and occupancy of transcription factors on host and/or pathogen chromatin. Chromatin preparation from tissues creates additional challenges that need to be overcome to obtain reproducible and reliable protocols comparable to those used for cell culture. Tissue disruption and fixation are critical steps to achieve efficient shearing of chromatin. Coexistence of different cell types and clusters may also require different shearing times to reach optimal fragment size and hinders shearing reproducibility. The purpose of this method is to achieve reliable and reproducible host chromatin preparations from frozen tissue (liver) suitable for both ChIP-qPCR and next generation sequencing (NGS) applications. We observed that the combination of liquid nitrogen tissue pulverization followed by homogenization leads to increased reproducibility compared to homogenization only, since it provides a suspension consisting mostly of dissociated single cells that can be efficiently sheared. Moreover, the fixation step should be performed under mild rotation to provide homogeneous crosslinking. The fixed material is then suitable for buffer-based nuclei isolation, to reduce contamination of cytoplasmic protein and pathogen DNAs and RNAs (when applicable), avoiding time-consuming centrifugation gradients. Subsequent sonication will complete nuclear lysis and shear the chromatin, producing a specific size range according to the chosen shearing conditions. The size range should fall between 100 and 300 nt for NGS applications, while it could be higher (300-700 nt) for ChIP-qPCR analysis. Such protocol adaptations can greatly improve chromatin analyses from frozen tissue specimens.

This protocol focuses on chromatin preparation from snap frozen tissues and it is suitable for Crosslinking Chromatin Immunoprecipitation (X-ChIP) followed by either quantitative PCR analysis (X-ChIP-qPCR) or next generation sequencing approaches (X-ChIP-seq).

Crosslinking Chromatin Immunoprecipitation (X-ChIP) is a widely used technique to assess levels of histone marks and occupancy of transcription factors on ...