Figure 2.

Methods for Studying Host–Pathogen Interactions Using Zebrafish. (A) Routes of zebrafish injection. Larvae can be injected locally into the YS or in body cavities, such as the HV and OV. Other compartments for injection include SC, IM, or the NC. HV, OV, IM, and TF infection all permit study of immune cell recruitment. The NC is inaccessible to immune cells but is valuable to model bone and cartilage inflammation. Injection into the circulation can be achieved by intravenous injections, for example via the CV/BI or the DC. This results in a rapid systemic dissemination of microbes throughout the body. (B) Chemical treatments. Zebrafish are suitable for toxicology research and for screening of libraries of bioactive compounds, including antimicrobials, because molecules in the bath water can be absorbed via the zebrafish skin. Survival and bacterial burden can be quantified to compare susceptibility of different genetic conditions or to assess the effect of chemicals/therapeutics in disease prevention. (C) Intravital imaging. Host–pathogen interactions can be followed in vivo by combining fluorescently-labeled bacteria and zebrafish transgenic lines reporting the expression pattern of specific genes or labeling specific cell types. A variety of proteins and subcellular compartments can also be tagged by fusing specific markers with fluorescent tags. (D) Parabiosis. Two zebrafish embryos can be fused by surgically forcing their blastulae into direct contact. This results in the development of conjoined embryos sharing blood circulation and body parts, enabling secreted factors and circulating cells to distribute in the bodies of both individuals. When applied to embryos with different genetic/transgenic makeup, this technique is useful to distinguish cell-autonomous from non-cell-autonomous functions. Abbreviations: BI, blood island; CV, caudal vein; DC, duct of Cuvier; HV, hindbrain ventricle; IM, intramuscular; NC, notochord; OV, otic vesicle; SC, subcutaneous; TF, tail fin; YS, yolk sac.