Name: modeling tuberculosis in mycobacterium marinum infected adult zebrafish
Uploaded: 2018-10-08T14:00:00
Description: Watch this Scientific Journal Video about Modeling Tuberculosis in Mycobacterium marinum Infected Adult Zebrafish at JoVE.com

This work has been supported by the Finnish Cultural Foundation (H.L.), Tampere Tuberculosis Foundation (H.L., L.-M.V., M.M.H., M.P.), Foundation of the Finnish Anti-Tuberculosis Association (Suomen Tuberkuloosin Vastustamisyhdistyksen Sa&#776;a&#776;tio&#776;) (H.L., M.M.H., M.P.), Sigrid Juse&#769;lius Foundation (M.P.), Emil Aaltonen Foundation (M.M.H.), Jane and Aatos Erkko Foundation (M.P.) and Academy of Finland (M.P.). Leena Ma&#776;kinen, Hanna-Leena Piippo and Jenna Iloma&#776;ki are acknowledged for their technical assistance.&#160;The authors acknowledge the Tampere Zebrafish Laboratory for their service.

All zebrafish experiments have been approved by the Animal Experiment Board in Finland (ESAVI/8245/04.10.07/2015). Methods are performed according to the act (497/2013) and the government decree (564/2013) on the protection of animals used for scientific or educational purposes in Finland.
1. Culturing of Mycobacterium marinum 
NOTE: Since Mycobacterium marinum is a pathogen capable of causing superficial infections in humans, find out the local guidelines fo...

Here we describe a qPCR-based application to measure mycobacterial loads from DNA extracted from experimentally infected adult zebrafish tissues. This application is based on primers designed around the 16S-23S rRNA internal transcribed spacer sequence40. The total mycobacterial load in a fish sample is estimated using a standard curve prepared from DNA extracted from a known number of cultured mycobacteria and assuming that one bacterium has one copy of its genome at any given moment. The detecti...

Zebrafish (Danio rerio) is a widely used animal model in biomedical research and it is an accepted model for common vertebrate biology. The zebrafish has been adapted to many fields of research modeling human diseases and disorders ranging from cancer1 and cardiac disease2 to infection and immunological studies of several bacterial 3 and viral infections4,5. In addition, the ex utero development of zebrafish embryos has made the zebrafish a popular model in developmental biology6 and toxicology7,8.
In many fields of research, including infection biology, the optically transparent zebrafish larvae are commonly used. The first immune cells appear within 24 h post fertilization (hpf), when primitive macrophages are detected9. Neutrophils are the next immune cells to appear around 33 hpf10. Zebrafish larvae are thus feasible for studying the early stages of infection and the role of innate immunity in the absence of adaptive immune cells11. However, the adult zebrafish with its fully functional adaptive immune system provides an additional layer of complexity for infection experiments. T cells can be detected around 3 days post fertilization12, and B cells are able to produce functional antibodies by 4 weeks post fertilization13. The adult zebrafish has all the main counterparts of the mammalian innate and adaptive immune system. The main differences between the immune systems of fish and humans are found in antibody isotypes as well as in the anatomy of lymphoid tissues. The zebrafish has only three antibody classes14, whereas humans have five15. In the absence of bone marrow and lymph nodes, the primary lymphoid organs in the fish are the kidney and the thymus16 and the spleen, the kidney and the gut serve as secondary lymphoid organs17. Despite these differences, with its full immune arsenal of innate and adaptive cells, the adult zebrafish is a highly applicable, easy-to-use, non-mammalian model for host-pathogen interaction studies.
The zebrafish has lately been established as a feasible model to study tuberculosis18,19,20,21,22. Tuberculosis is an airborne disease caused by Mycobacterium tuberculosis. According to the World Health Organization, tuberculosis caused1.7 million deaths in 2016 and is the leading cause of death by a single pathogen worldwide23. Mice24,25, rabbits26 and non-human primates27 are the best-known animal models in tuberculosis research but each face their limitations. The non-human primate model of M. tuberculosis infection resembles the human disease most closely, but using this model is limited due to serious ethical considerations. Other animal models are hindered by the host-specificity of M. tuberculosis that affects the disease pathology. Probably the biggest issue in modeling tuberculosis is the wide spectrum of infection and disease outcomes in the human disease: tuberculosis is a very heterogeneous disease ranging from sterilizing immunity to latent, active and reactivated infection28, which can be hard to reproduce and model experimentally.
Mycobacterium marinum is a close relative of M. tuberculosis with ~3,000 orthologous proteins with 85% amino acid identity29. M. marinum naturally infects zebrafish producing granulomas, the hallmarks of tuberculosis, in its internal organs19,30. Unlike other animal models used in tuberculosis research, zebrafish produces many offspring, it requires only a limited space and importantly, it is neurophysiologically the least developed vertebrate tuberculosis model available. Additionally, the M. marinum infection causes latent infection, active disease or even sterilization of mycobacterial infection in adult zebrafish closely mimicking the spectrum of disease outcomes of human tuberculosis19,31,32. Here, we describe methods for the experimental tuberculosis model of adult zebrafish by injecting M. marinum into the abdominal cavity and using quantitative PCR to measure the mycobacterial loads and immune responses from zebrafish tissue samples.

<table>
	<tbody>
		<tr>
			<td>Mycobacterium marinum</td>
			<td>American Type Culture Collection</td>
			<td>ATCC 927</td>
			<td></td>
		</tr>
		<tr>
			<td>Middlebrock 7H10 agar</td>
			<td>BD, Thermo Fisher Scientific</td>
			<td>11799042</td>
			<td></td>
		</tr>
		<tr>
			<td>Middlebrock OADC enrichment</td>
			<td>BD, Thermo Fisher Scientific</td>
			<td>11718173</td>
			<td></td>
		</tr>
		<tr>
			<td>Middlebrock 7H9 medium</td>
			<td>BD, Thermo Fisher Scientific</td>
			<td>11753473</td>
			<td></td>
		</tr>
		<tr>
			<td>Middlebrock ADC enrichment</td>
			<td>BD, Thermo Fisher Scientific</td>
			<td>11718173</td>
			<td></td>
		</tr>
		<tr>
			<td>Tween 80</td>
			<td>Sigma-Aldrich</td>
			<td>P1754</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycerol</td>
			<td>Sigma-Aldrich</td>
			<td>G5516-500ML</td>
			<td></td>
		</tr>
		<tr>
			<td>GENESYS20 Spectrophotometer</td>
			<td>Thermo Fisher Scientific</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate buffered saline tablets (PBS)</td>
			<td>Sigma-Aldrich</td>
			<td>P4417-50TAB</td>
			<td></td>
		</tr>
		<tr>
			<td>Phenol red</td>
			<td>Sigma-Aldrich</td>
			<td>P3532</td>
			<td></td>
		</tr>
		<tr>
			<td>27G needle</td>
			<td>Henke Sass Wolf</td>
			<td>4710004020</td>
			<td></td>
		</tr>
		<tr>
			<td>1 ml syringe</td>
			<td>Henke Sass Wolf</td>
			<td>4010.200V0</td>
			<td></td>
		</tr>
		<tr>
			<td>Omnican 100 30G insulin needle</td>
			<td>Braun</td>
			<td>9151133</td>
			<td></td>
		</tr>
		<tr>
			<td>3-aminobenzoic acid ethyl ester (pH 7.0)</td>
			<td>Sigma-Aldrich</td>
			<td>A5040</td>
			<td></td>
		</tr>
		<tr>
			<td>1.5 ml homogenization tube</td>
			<td>Qiagen</td>
			<td>13119-1000</td>
			<td></td>
		</tr>
		<tr>
			<td>2.8 mm ceramic beads</td>
			<td>Qiagen</td>
			<td>13114-325</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol, ETAX Aa</td>
			<td>Altia</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>2-propanol</td>
			<td>Sigma-Aldrich</td>
			<td>278475</td>
			<td></td>
		</tr>
		<tr>
			<td>Chloroform</td>
			<td>VWR</td>
			<td>22711.290</td>
			<td></td>
		</tr>
		<tr>
			<td>Guanidine thiocyanate</td>
			<td>Sigma-Aldrich</td>
			<td>G9277</td>
			<td>FW 118.2 g/mol</td>
		</tr>
		<tr>
			<td>Sodium citrate</td>
			<td>Sigma-Aldrich</td>
			<td>1613859</td>
			<td>FW 294.1 g/mol</td>
		</tr>
		<tr>
			<td>Tris (free base)</td>
			<td>Sigma-Aldrich</td>
			<td>TRIS-RO</td>
			<td>FW 121.14 g/mol</td>
		</tr>
		<tr>
			<td>TRI reagent</td>
			<td>Molecular Research Center</td>
			<td>TR118</td>
			<td>Guanidine thiocyanate-phenol solution</td>
		</tr>
		<tr>
			<td>PowerLyzer24 homogenizator</td>
			<td>Qiagen</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sonicator m08</td>
			<td>Finnsonic</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Nanodrop 2000</td>
			<td>Thermo Fisher Scientific</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>SENSIFAST No-ROX SYBR, Green Master Mix</td>
			<td>Bioline</td>
			<td>BIO-98005</td>
			<td></td>
		</tr>
		<tr>
			<td>qPCR 96-well plate</td>
			<td>BioRad</td>
			<td>HSP9601</td>
			<td></td>
		</tr>
		<tr>
			<td>Optically transparent film</td>
			<td>BioRad</td>
			<td>MSB1001</td>
			<td></td>
		</tr>
		<tr>
			<td>C1000 Thermal cycler with CFX96 real-time system</td>
			<td>BioRad</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>RNase AWAY</td>
			<td>Thermo Fisher Scientific</td>
			<td>10666421</td>
			<td>decontamination reagent eliminating RNases</td>
		</tr>
		<tr>
			<td>DNase I</td>
			<td>Thermo Fisher Scientific</td>
			<td>EN0525</td>
			<td></td>
		</tr>
		<tr>
			<td>Reverse Transcription Master Mix</td>
			<td>Fluidigm</td>
			<td>100-6298</td>
			<td></td>
		</tr>
		<tr>
			<td>SsoFast Eva Green master mix</td>
			<td>BioRad</td>
			<td>172-5211</td>
			<td></td>
		</tr>
	</tbody>
</table>

modeling tuberculosis in mycobacterium marinum infected adult zebrafish

Mycobacterium tuberculosis is currently the deadliest human pathogen causing 1.7 million deaths and 10.4 million infections every year. Exposure to this bacterium causes a wide disease spectrum in humans ranging from a sterilized infection to an actively progressing deadly disease. The most common form is the latent tuberculosis, which is asymptomatic, but has the potential to reactivate into a fulminant disease. Adult zebrafish and its natural pathogen Mycobacterium marinum have recently proven to be an applicable model to study the wide disease spectrum of tuberculosis. Importantly, spontaneous latency and reactivation as well as adaptive immune responses in the context of mycobacterial infection can be studied in this model. In this article, we describe methods for the experimental infection of adult zebrafish, the collection of internal organs for the extraction of nucleic acids for the measurement of mycobacterial loads and host immune responses by quantitative PCR. The in-house-developed, M. marinum-specific qPCR assay is more sensitive than the traditional plating methods as it also detects DNA from non-dividing, dormant or recently dead mycobacteria. As both DNA and RNA are extracted from the same individual, it is possible to study the relationships between the diseased state, and the host and pathogen gene-expression. The adult zebrafish model for tuberculosis thus presents itself as a highly applicable, non-mammalian in vivo system to study host-pathogen interactions.

The natural fish pathogen Mycobacterium marinum infects the internal organs of the zebrafish and produces a systemic infection with histologically visible granulomas19. Adult zebrafish are infected with M. marinum by an intraperitoneal injection. The DNA and RNA are extracted, and the mycobacterial load is measured by quantitative polymerase chain reaction (qPCR) using DNA as the template. The outline of the method is shown in <strong class="xfig"...

Watch this Scientific Journal Video about Modeling Tuberculosis in Mycobacterium marinum Infected Adult Zebrafish at JoVE.com

Modeling Tuberculosis in Mycobacterium marinum Infected Adult Zebrafish

Here, we present a protocol to model human tuberculosis in an adult zebrafish using its natural pathogen Mycobacterium marinum. Extracted DNA and RNA from the internal organs of infected zebrafish can be used to reveal the total mycobacterial loads in the fish and the host&#39;s immune responses with qPCR.

Modeling Tuberculosis in Mycobacterium marinum Infected Adult Zebrafish

Mycobacterium tuberculosis is currently the deadliest human pathogen causing 1.7 million deaths and 10.4 million infections every year. Exposure to this ...

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