Investigation of antigenic structure of attenuated and virulent Venezuelan equine encephalomyelitis virus by means of monoclonal antibodies.

The research focuses on investigating the differences in the antigenic structure between the strains of a virus causing Venezuelan equine encephalomyelitis (VEEV) that are widely circulating and those that have been weakened for use in vaccines. The researchers pinpoint specific parts of two viral proteins that provoke a response from the immune system, some of which have been found effective in protecting against serious infection.

Understanding the Antigenic Structure

• The research begins by performing a comparative study of the antigenic structure of the Venezuelan equine encephalomyelitis virus. The antigenic structure refers to the specific parts of a virus that the immune system recognises and responds to. These can be comprised of various viral components, such as proteins, that are unique to each virus.
• The two strains of the VEEV that are compared are virulent strains, which are capable of causing the actual disease, and attenuated vaccine strains, which are versions of the virus that have been weakened to the point that they are no longer harmful.

The Role of Glycoproteins E1 and E2

• The study specifically looks at the roles of two envelope glycoproteins, known as E1 and E2. These are proteins located on the surface of the virus that play a direct role in how the virus infects hosts and are commonly the target of immune responses.
• On the E1 glycoprotein, the researchers found five nonoverlapping antigenic sites consisting of eight epitopes recognised by monoclonal antibodies. Monoclonal antibodies are artificially produced molecules that can mimic the immune system’s response to pathogens.
• Similarly, they discovered twenty epitopes divided into six antigenic sites on the E2 glycoprotein.

Identification of Protective Epitopes

• The research also identified protective epitopes. Out of all the epitopes on glycoproteins E1 and E2, monoclonal antibodies reacting with four specific sites protect animals against lethal infection with a particularly virulent strain of the VEEV called the Trinidad donkey.
• Thirteen epitopes were identified as being responsible for antiviral immunity, with three undergoing changes in the TC-83 strain, and another six belonging to two sites in the 230 strain.

Implications for Vaccine Development

• The team concludes that the findings signal the need for continuous improvement of vaccines against VEEV. Such improvements could address the observed changes in antigenic sites within the TC-83 strain to increase the effectiveness of vaccines against this dangerous infectious disease.