Identification of novel antigen candidates for a tuberculosis vaccine in the adult zebrafish (<i>Danio rerio</i>)

<div><p>Tuberculosis (TB) remains a major global health challenge and the development of a better vaccine takes center stage in fighting the disease. For this purpose, animal models that are capable of replicating the course of the disease and are suitable for the early-stage screening of vaccine candidates are needed. A <i>Mycobacterium marinum</i> infection in adult zebrafish resembles human TB. Here, we present a pre-clinical screen for a DNA-based tuberculosis vaccine in the adult zebrafish using an <i>M</i>. <i>marinum</i> infection model. We tested 15 antigens representing different types of mycobacterial proteins, including the Resuscitation Promoting factors (Rpf), PE/PPE protein family members, other membrane proteins and metabolic enzymes. The antigens were expressed as GFP fusion proteins, facilitating the validation of their expression <i>in vivo</i>. The efficiency of the antigens was tested against a low-dose intraperitoneal <i>M</i>. <i>marinum</i> infection (≈ 40 colony forming units), which mimics a primary <i>M</i>. <i>tuberculosis</i> infection. While none of the antigens was able to completely prevent a mycobacterial infection, four of them, namely RpfE, PE5_1, PE31 and cdh, led to significantly reduced bacterial burdens at four weeks post infection. Immunization with RpfE also improved the survival of the fish against a high-dose intraperitoneal injection with <i>M</i>. <i>marinum</i> (≈ 10.000 colony forming units), resembling the disseminated form of the disease. This study shows that the <i>M</i>. <i>marinum</i> infection model in adult zebrafish is suitable for the pre-clinical screening of tuberculosis vaccines and presents RpfE as a potential antigen candidate for further studies.</p>