Levels of immunoglobulins and antibodies to haemaglutinin and neuraminidase of influenza virus in nasal secretions after natural infection.

Nasal washings (NW) from 16 influenza patients in the course of an epidemic in November and December, 1974 were examined for the presence of influenza virus, immunoglobulins (Ig) and titres of haemagglutination inhibiting (HI) and neuraminidase inhibiting (NI) antibodies. Influenza virus identical with A/Port Chalmers/1/73 (H3N2), increased levels of IgA and occasionally IgG, and specific antibodies were detected in the NW. The dynamics of HI and NI antibody formation did not differ substantially, but there were individual differences in titres and persistence of antibodies. Convalescent sera always contained increased levels of HI and NI antibodies. In some cases, the titres of antibody to viral ribonucleoprotein did not increase.