Radioimmunoassay for quantitation of antibodies to alphaviruses with staphylococcal protein A.

The research article describes a method for measuring antibodies to alphaviruses in various mammals using a radioimmunoassay procedure.

Radioimmunoassay Procedure

The radioimmunoassay procedure is a laboratory method used to measure very small amounts of substances in the blood, such as hormones and drugs, depending on the specific antibodies they contain. In this particular study, the focus was on using the procedure for measuring antibodies to alphaviruses.

• This test utilized protein A-bearing Staphylococcus aureus as a solid-phase immunoadsorbent for radioactive-labelled viruses complexed with immunoglobulin G.
• Immunoglobulin G (IgG) is the most common type of antibody found in blood circulation, and it helps protect the body from infection.
• The researchers used antibodies produced in humans and guinea pigs for the radioimmunoassay procedure.

Antibody Differentiation

The procedure was successful in differentiating between antibodies to Venezuelan, western, and eastern equine encephalomyelitis viruses which are types of alphaviruses.

• The sensitivity of the assay depends on the concentrations of labeled viruses used in the test.
• The investigation noted that the serum dilution which effected 50% binding of the radioactive virus was consistently higher than the inherent neutralizing antibody titer – a measurement of how much neutralizing antibody an organism has produced.

Seroconversion Screening

Following this, sera from 73 individuals were screened for seroconversion, which refers to the time period during an infection when antibodies develop and become detectable in the blood, after being inoculated with a live attenuated Venezuelan equine encephalomyelitis virus vaccine.

• The researchers used a single serum dilution level (1:80) in the radioimmunoassay.
• The results using the radioimmunoassay were identical with the results achieved via the conventional plaque reduction neutralization test, confirming the effectiveness of the radioimmunoassay procedure.

Applications Across Mammalian Species

The researchers managed to successfully titrate – or determine the concentration of – hyperimmune Venezuelan equine encephalomyelitis virus sera from a variety of mammalian species.

• The species tested included humans, guinea pigs, white rats, rabbits, burros, dogs, monkeys, sheep, and cotton rats.

A Promising Serological Tool

This study suggests that the protein A-mediated radioimmunoassay is a speedy, sensitive, specific, and precise serological tool to measure antibodies to the surface antigens of alphaviruses.

• Antigens are substances which prompt the production of antibodies by the immune system.
• This method could pave the way for the development of a competitive binding radioimmunoassay to measure the antigenic potency of inactivated alphavirus vaccines.