Virus-specific, antibody-secreting cells during upper respiratory infections.

The humoral immune response of 18 army recruits with febrile upper respiratory infection (URI) was studied by enumerating virus-specific, antibody-secreting cells in the peripheral blood. Diagnosis was based on viral antigen detection in nasopharyngeal specimens, virus isolation from throat swabs, or on antibody measurement from paired serum samples. At the time of the sample collection, three viruses, including adenovirus, influenza A, and influenza B, were found mainly to cause URIs among the recruits, and ELISPOT assay for enumeration of the specific antibody-secreting cells was selected for these viruses. Of the 36 patients with febrile URI studied, viral diagnosis was made in 18 cases, which included 11 patients with adenovirus infection, three with influenza A, and four with influenza B. The first blood sample was collected at the first signs of URI and the second and third samples at 2-week intervals. The adenovirus-positive patients developed a strong IgG class antibody-secreting cell response against the homologous virus, which peaked at the first sample and decreased steeply by the second and third samples. In the influenza A and B patients, the response was similar kinetically to that seen in adenovirus-positive patients. In those cases where also IgA and IgM class antibody-secreting cells were determined, the IgG response dominated. The ELISPOT method has potential also as a diagnostic tool for respiratory infections.