Compromised B cell responses to influenza vaccination in HIV-infected individuals.

Background: Yearly influenza vaccination, although recommended for human immunodeficiency virus (HIV)-infected individuals, has not received thorough evaluation in the era of antiretroviral therapy. We assessed the impact of HIV disease on B cell responses to influenza vaccination.

Methods: Sixty-four HIV-infected and 17 HIV-negative individuals received the 2003-2004 trivalent inactivated influenza vaccine. Frequencies of influenza-specific antibody-secreting cells (ASCs) were measured by enzyme-linked immunospot (ELISPOT) assay, and antibody responses were measured by hemagglutination-inhibition (HI) assay. Memory responses to influenza were measured by ELISPOT assay after polyclonal activation of B cells in vitro.

Results: Prevaccination HI titers were significantly higher in HIV-negative than in HIV-infected individuals. Peak HI titers and influenza-specific ASC frequencies were directly correlated with CD4+ T cell counts in HIV-infected individuals. Influenza-specific memory B cell responses were significantly lower in HIV-infected than in HIV-negative individuals and were directly correlated with CD4+ T cell counts.

Conclusions: HIV infection is associated with a weak antibody response to influenza vaccination that is compounded by a poor memory B cell response. CD4+ T cell count is a critical determinant of responsiveness to influenza vaccination, and the contribution of plasma HIV RNA level is suggestive and warrants further investigation.