Value of immunological markers in predicting responsiveness to influenza vaccination in elderly individuals

Elderly individuals are at high risk for morbidity and mortality when infec ted with influenza virus. Vaccinations with inactivated virus are less effe ctive in the elderly due to the declining competency of the aging immune sy stem. We have explored whether immunological parameters predict poor anti-i nfluenza virus vaccine responses and can be used as biological markers of i mmunosenescence. One hundred fifty-three residents of community-based retir ement facilities aged 65 to 98 years received a trivalent influenza vaccine . Vaccine-induced antibody responses were determined by comparing hemagglut ination inhibition titers before and 28 days after immunization. The compos ition of the T-cell compartment was analyzed by flow cytometry and the size s of three T-cell subsets, CD4(+) CD45RO(+) cells, CD4(+) CD28(null) cells, and CD8(+) CD28(null) cells, were determined. Only 17% of the vaccine reci pients were able to generate an increase in titers of antibody to all three vaccine components, and 46% of the immunized individuals failed to respond to any of the three hemagglutinins. The likelihood of successful vaccinati on declined with age and was independently correlated with the expansion of a particular T-cell subset, CD8(+) CD28(null) T cells. The sizes of the CD 4(+) CD45RO(+) memory T-cell and CD4(+) CD28(null) T-cell subsets had no ef fect on the ability to mount anti-influenza virus antibody responses. Frequ encies of CD8(+) CD28(null) T cells are useful biological markers of compro mised immunocompetence, identifying individuals at risk for insufficient an tibody responses.