EVALUATION OF THE EFFICACY OF MODIFIED VACCINIA ANKARA (MVA)/IMVAMUNE IN THE AEROSOLIZED RABBITPOX RABBIT MODEL

Abstract

Rabbitpox virus (RPXV) is an orthopoxvirus that, when aerosolized, causes severe respiratory disease in rabbits. The rabbitpox (RPX) rabbit model is a valuable, informative model system to test medical countermeasures against orthopoxviruses because the disease course is similar to monkeypox (MPX) and smallpox in humans. Because smallpox has been eradicated, efficacy evaluation of new-generation vaccines against this disease depends on a combination of relevant animal efficacy studies for vaccine licensure. In this study, we tested the efficacy of MVA-BN (Bavarian Nordic) (IMVAMUNE) vaccine for protecting rabbits against aerosolized RPXV. Rabbits were vaccinated with phosphate-buffered saline (PBS), Dryvax®, low dose IIVIVAMUNE, high dose IMVAMUNE, or twice (14 days apart) with high dose IMVAMUNE. An aerosol challenge of a targeted dose of 100 LD50 was performed 4 weeks after the last vaccination. All PBS control animals were euthanized or succumbed to the disease ~7 days post aerosol challenge. While none of the rabbits vaccinated with Dryvax®, low dose IMVAMUNE, or high dose IMVAMUNE succumbed to the disease, they did show minimal to moderate clinical signs of the disease. Two rabbits vaccinated twice with high dose IMVAMUNE showed signs of mild anorexia, however the remaining rabbits in the group were fully protected from the disease and all rabbits survived aerosol challenge. This study shows that IMVAMUNE can be a very effective vaccine against aerosolized RPXV.