Demonstration of type-specific influenza antibody in mammalian and avian sera by immunodiffusion.

The detection of antibody against the ribonucleoprotein antigen of influenza virus is useful because its type-specificity allows the use of serological surveys to detect evidence of recent infections. Antigenic differences between strains limit the usefulness of the techniques, such as the haemagglutination-inhibition test, that detect antibody against surface antigens.This paper describes an agar-gel precipitation (AGP) test that will detect type-specific antibody in avian or mammalian sera. Convalescent levels of antibody against either type A or B influenza virus were demonstrated in human sera. Positive but inconsistent results were obtained with swine sera. The antigens used in the AGP test are non-infectious and stable. The test is easy and economical to perform. Its sensitivity compares favourably with that of the complement-fixation test using human and equine sera.While not a replacement for any of the serological tests at present in current use, the AGP test should prove useful in a variety of diagnostic and research situations.