Objective: HIV-positive individuals have lower antibody titers to influenza viruses than HIV-negative individuals, and the benefits of the annual vaccinations are controversially discussed. Also, there is no information about the breadth of the antibody response in HIV-infected individuals.
Design: The binding and neutralizing antibody titers to various human and nonhuman influenza A virus strain were determined in sera from 146 HIV-infected volunteers: They were compared with those found in 305 randomly selected HIV-negative donors, and put in relation to HIV-specific parameters. Uni and multivariable regression was used to identify HIV-specific parameters associated with the measured binding and neutralizing activity.
Methods: Enzyme-linked immunosorbent assays and in-vitro neutralization assays were used to determine the binding and neutralizing antibodiy titers to homo and heterosubtypic influenza A subtypes.
Results: We found that both homo and heterosubtypic antibody titers are lower in HIV-positive individuals. Vaccination promoted higher binding and neutralizing antibody titers to human but not to nonhuman isolates. HIV-induced immune damage (high viral load, low CD4+ T cell counts, and long untreated disease progression) is associated with impaired homosubtypic responses, but can have beneficial effects on the development of heterosubtypic antibodies, and an improved ratio of binding to neutralizing antibody titers to homosubtypic isolates.
Conclusions: Our results indicate that repetitive vaccinations in HIV-positive individuals enhance antibody titers to human isolates. Interestingly, development of antibody titers to conserved heterosubtypic epitopes paradoxically appeared to profit from HIV-induced immune damage, as did the ratio of binding to neutralizing antibodies.