T cell activation and human immunodeficiency virus replication after influenza immunization of infected children

Background. T cell activation plays a major role in the ability of HIV to remain latent or to establish a productive infection. It has been hypothesized that vaccination-mediated immune stimulation can activate T cells and enhance HIV replication. Our study was designed to determine whether influenza immunization would induce T cell activation and increase HIV burdens in HIV-infected children. Methods. Blood samples from 16 HIV- infected children ages 6 months to 14 years were obtained immediately before and 2 and 6 to 8 weeks after the administration of influenza vaccine. The percentage of activated (CD25⁺) T cells was determined by flow cytometry, and HIV viral load was measured by quantitative cultures of peripheral blood mononuclear cells and plasma HIV RNA. Results. The administration of influenza vaccine was associated with significant increases in HIV viral load in 5 of 16 children evaluated. These increases in HIV burden were transient, and in four of five patients the plasma HIV RNA copy number returned to baseline 6 to 8 weeks after immunization. There was no correlation between the patient's immunologic or clinical category according to the CDC classification and either the initial viral load or the likelihood of having a significant increase after immunization. Four of the five patients who experienced increases in viral load after influenza immunization were not receiving antiretroviral therapy. Conclusions. Our results emphasize the need for additional studies that examine the effect of routine immunizations on T cell activation and HIV replication in HIV- infected children.