Active and passive vaccination against hantavirus pulmonary syndrome with Andes virus M genome segment-based DNA vaccine

Hantavirus pulmonary syndrome (HPS) is a rapidly progressing human disease with one of the highest case fatality rates (30 to 50%) of any acute viral disease known. There are no vaccines, effective antiviral drugs, or immunologics to prevent or treat HPS. In an attempt to develop HPS medical countermeasures, we constructed an expression plasmid, pWRG/AND-M, that contains the full-length M genome segment of Andes virus (ANDV), a South American hantavirus. Transfection experiments in cell culture indicated that both the G1 and G2 glycoproteins are expressed from pWRG/AND-M. Rhesus macaques vaccinated by gene gun with pWRG/AND-M developed remarkably high levels of neutralizing antibodies that not only neutralized ANDV but also cross-neutralized other HPS-associated hantaviruses, including Sin Nombre virus. To determine if the antibodies elicited in the monkeys could confer protection, we performed a series of passive-transfer experiments using a recently described lethal HPS animal model (i.e., adult Syrian hamsters develop HPS and die within 10 to 15 days after challenge with ANDV). When injected into hamsters 1 day before challenge, sera from the vaccinated monkeys either provided sterile protection or delayed the onset of HPS and death. When injected on day 4 or 5 after challenge, the monkey sera protected 100% of the hamsters from lethal disease. These data provide a proof of concept for a gene-based HPS vaccine and also demonstrate the potential value of a postexposure immunoprophylactic to treat individuals after exposure, or potential exposure, to these highly lethal hantaviruses.