Immunogens of encephalitis viruses.

The research article discusses equine encephalitis viruses, which affect horses and are transmitted by mosquito bites. The article also provides information about the virus structure, vaccines developed for it, and the ongoing research on understanding the virus attenuation or weakening mechanism.

Equine Encephalitis Viruses: An Overview

• The study focuses on equine encephalitis viruses, which are part of the Alphavirus genus and the Togaviridae family. There are three main types of this virus, namely, western (WEE), eastern (EEE), and Venezuelan equine encephalitis (VEE) viruses. These viruses cause infections in horses across the Western hemisphere and are transmitted through mosquito bites.

Vaccines for Equine Encephalitis Viruses

• The first vaccines for these viruses were made by virus inactivation. However, there were issues with insufficient inactivation, leading to a major VEE outbreak in Central America and Texas in the 1970s.
• Subsequently, a live attenuated VEE virus vaccine, known as TC-83, was developed through cell culture passage, a process involving propagating cells in a controlled environment. Inactivated vaccines are still in use to prevent WEE and EEE infections in horses.

The Structure of Alphaviruses

• Alphaviruses are small, single-stranded positive sense RNA viruses. Their genome, made of 12,000 nucleotides, is enclosed in a structure called an icosahedral nucleocapsid, which consists of multiple copies of a protein called the capsid protein.
• The virions, or virus particles, of this virus are enveloped, meaning they are surrounded by a lipid membrane. This membrane is modified by inserting two types of glycoproteins: E1 and E2.

Understanding Protective Antigens and Virus Attenuation

• Monoclonal antibody analysis of the surface glycoproteins has resulted in a better understanding of protective antigens, the parts of a pathogen that the immune system recognizes and reacts to.
• Recent studies that compare gene sequences from virulent (disease-causing) and avirulent (non-disease-causing) VEE viruses are beginning to uncover the mechanisms of alphavirus attenuation or virus weakening. This could potentially help in creating more effective vaccines in the future.