ASSESSMENT OF MARKERS OF THE CELL-MEDIATED IMMUNE-RESPONSE AFTER INFLUENZA-VIRUS INFECTION IN FRAIL OLDER ADULTS

The purpose of this study was to determine whether measures of the cel l-mediated immune response to influenza virus could be used as markers of influenza virus infection. We studied 23 subjects who developed up per respiratory, lower respiratory, or systemic symptoms during a smal l outbreak of influenza in a nursing home population. Influenza virus culture from nasopharyngeal swabs yielded influenza virus isolates fro m 7 of the 23 subjects. only three of the subjects had a fourfold rise in antibody titer to the influenza virus antigen positivity after the infection, Granzyme B and cytokine levels were measured in peripheral blood mononuclear cells (PBMC) obtained from all subjects and stimula ted with live influenza virus. Elevated granzyme B levels in virus-sti mulated PBMC in combination with lower respiratory tract or systemic s ymptoms in study subjects was a significant predictor of culture-confi rmed influenza virus infection compared to those from whom influenza v irus could not be identified. Cytokine levels did not distinguish betw een the two groups in a similar type of analysis. Granzyme B in combin ation with the clinical profile of symptoms may be a useful retrospect ive marker for influenza virus infection.