Comparative pathology study of Venezuelan, eastern, and western equine encephalitis viruses in non-human primates.

The study examines the pathology of Venezuelan, eastern, and western equine encephalitis viruses in non-human primates, specifically cynomolgus macaques, through a route that closely mimics natural infection. The results show differences in the pathogenic nature of the three encephalitic viruses, with the eastern variety proving significantly more detrimental than the Venezuelan one, a pattern also observed in humans.

Methodology

• The researchers studied the pathogenesis of Venezuelan, eastern, and western equine encephalitis viruses (VEEV, EEEV, and WEEV) in non-human primates, particularly cynomolgus macaques.
• The way of exposure to the viruses was made to mimic natural infection, through subcutaneous exposure, imitating a mosquito transmission or needle stick accident closely.

Findings

• One of the significant findings of the study is that EEEV or Eastern Encephalitis Virus is a lot more pathogenic compared to VEEV (Venezuelan equine encephalitis viruses). This finding mirrors the pattern observed in human infections, thus, validating its accuracy.
• When the EEEV was transmitted subcutaneously, its neuropathogenic effects were found to be similar to those observed in aerosol exposure studies, i.e., the method of transmission doesn’t alter its pathogenesis.
• On the other hand, the WEEV or Western Encephalitis Virus presented limited disease symptoms when introduced subcutaneously into the macaques. This contradicts previous findings using aerosol exposure, indicating that the exposure method might influence the pathogenesis of this virus.
• The researchers observed differences in viremia (the presence of viruses in the blood), hematology (study of blood), and tissue tropism (the cells and tissues of a host which support growth of a particular virus) when animals were exposed subcutaneously compared to prior aerosol exposure studies.

Implications

• By presenting a more comprehensive understanding of the pathogenesis of the encephalitic alphaviruses, the study aids in the development of medical countermeasures against these neurovirulent viruses.
• The findings underline the importance of further defining the neuropathology of these viruses to improve treatments and preventative strategies in humans and equids, largely horses, donkeys, and zebras.