[Changes in antigenic determinant H3 in type A influenza virus]

Area of Science:

• Virology
• Immunology
• Molecular Biology

Background:

• Influenza A viruses, particularly the Hong Kong variety, possess a common H3 antigenic determinant in their hemagglutinins.
• Monitoring antigenic drift in circulating influenza strains is crucial for vaccine development and public health.

Purpose of the Study:

• To analyze the expression of the H3 antigenic determinant in 1975 influenza A virus isolates.
• To investigate the immune response to the H3 antigen in rabbits using immune and hyperimmune sera.

Main Methods:

• Analysis of immune and hyperimmune rabbit sera against influenza A/USSR/0249/75, A/Victoria/3/75, and A/Tokyo/1/75.
• Adsorption tests using anti-H3 monoreceptor sera to quantify H3 antigen levels.

Main Results:

• The H3 antigenic determinant was poorly expressed in 1975 influenza A virus isolates compared to previous years.
• Antibodies to H3 were generally absent in immune sera and only detected in hyperimmune sera after re-immunization.
• Quantitative decrease of H3 antigen in 1975 viruses was confirmed through adsorption assays.

Conclusions:

• 1975 influenza A virus isolates exhibited reduced H3 antigenicity.
• This diminished antigenicity may necessitate adjustments in influenza surveillance and vaccine strain selection.