Serological diagnosis of human influenza infections by immunoprecipitin techniques

In immunodiffusion tests employing disrupted influenza virus (A2/Hong King/68, X-31 strain) as antigen, precipitin lines corresponding to three virus antigens can be distinguished-namely, the ribonucleoprotein, the haemagglutinin, and the neuraminidase. In the present study a comparison was made of such immunodiffusion tests and conventional diagnostic methods (complement-fixation and haemagglutination-inhibition tests) for serological diagnosis of A2/Hong Kong/68 infections in man. Precipitin tests in which the acquisition or reinforcement of precipitins for A2/Hong Kong/68 virus were detected, were found to be as sensitive as conventional methods for the serological diagnosis of influenza. In convalescent human sera precipitin lines corresponding to influenza A ribonucleoprotein were frequently detected, lines corresponding to A2 neuraminidase were less frequent, and those corresponding to haemagglutinin were least frequent. Precipitin tests had considerable advantages over other methods of serological diagnosis of influenza. They were rapid and simple to perform and were not susceptible to the effects of nonspecific reactions. In addition the antibody response to each of three antigens of the influenza virus could be detected in a single test system.