Pseudotyped viruses permit rapid detection of neutralizing antibodies in human and equine serum against Venezuelan equine encephalitis virus.

Virus envelope proteins are the primary targets of neutralizing antibody responses. The epitopes recognized differ sufficiently between virus subtypes and species to distinguish viruses and provide an important basis for disease diagnosis. Venezuelan equine encephalitis virus (VEEV) causes acute febrile illness in humans and has high mortality in equines. The most specific detection methods for serum antibodies use live virus in neutralization assays or in blocking enzyme linked immunosorbent assays. However, work with Venezuelan equine encephalitis virus requires biosafety level 3 containment and select agent security in the United States. We report two new assays for detection of Venezuelan equine encephalitis virus neutralizing antibody responses, based on virus pseudotypes. The first provides detection by marker gene expression after 20 hours and is particularly suited for high-throughput screening; the second uses a new, rapid virus entry assay to give readouts within 1 hour. Both assays are safe, sensitive, and in general recapitulate neutralizing antibody titers obtained by conventional plaque reduction assays. Each is suitable as a rapid primary screen for detection of neutralizing antibodies against Venezuelan equine encephalitis virus.