Cross-protective immunity between equine encephalomyelitis viruses in equids.

The study examines the cross-protective immunity between different strains of horse encephalitis viruses in equids. It found that equids inoculated with eastern and western types demonstrated an immune response that lowered mortality rates when subsequently exposed to the Venezuelan variety.

Overview of Research Methods

• Scientists inoculated a set of 18 equids each with eastern equine encephalomyelitis (EEE) and western equine encephalomyelitis (WEE) to create two separate groups of EEE and WEE virus-immunized equids.
• Out of the surviving EEE and WEE virus-positive equids and a group of 10 non-immunized, seronegative equids (used as controls), each was subsequently exposed to an equine pathogenic strain of Venezuelan equine encephalomyelitis (VEE) virus.

Findings on Cross-Protective Immunity

• From the process, the study found a high mortality rate of 90% among the control group of non-immunized equids.
• In contrast, WEE virus-seropositive equids displayed a decrease in mortality at 40%, and all EEE virus-seropositive equids survived. This indicates an apparent cross-protective immunity in EEE and WEE virus-immunized equids against the VEE virus.
• What’s more, post-challenge exposure of VEE viremia levels in EEE and WEE virus-seropositive equids were lower than those in the nonimmune control group, effectively demonstrating a distinct protection mechanism via a prior exposure to either EEE or WEE virus.
• A significant similarity was also observed in the time of onset and titers of plaque-neutralizing antibody responses to VEE virus in both EEE and WEE virus-seropositive equids, compared to the responses in non-immunized equids.

Neutralizing Antibody to the Third Equine Encephalomyelitis Virus

• The team detected neutralizing antibodies to the third equine encephalomyelitis virus (either EEE or WEE virus) in 19 of 27 equids after inoculation with the challenge virus. This shows that exposure to one type of equine encephalitis virus can stimulate an immune response against another strain.
• These findings confirm field observations made during the VEE outbreak in Texas in 1971 and advance our understanding of interconnected immunity responses among different viruses in equids.