TC-83 vaccine protects against airborne or subcutaneous challenge with heterologous mouse-virulent strains of Venezuelan equine encephalitis virus

Vaccination with TC-83 virus produced solid protection against subcutaneous challenge with Venezuelan equine encephalitis (VEEV) viruses from homologo us and heterologous serogroups. but breakthrough infection and disease occu rred after airborne challenge, Breakthrough occurred more often with time a fter vaccination, and was more frequent with epizootic, homologous serogrou p 1A/B viruses than with enzootic, heterologous serogroup viruses. A decrea se in VEEV-specific IgA levels in the respiratory tract of vaccinated mice may explain the increased frequency of breakthrough with time after vaccina tion. However increased breakthrough with the highly virulent homologous se rogroup 1A/B viruses (compared to less virulent viruses from heterologous s erogroups) may be a consequence of their greater ability to invade the brai n via the olfactory neuroepithelium and olfactory nerve. (C) 1999 Elsevier Science Ltd. All rights reserved.