Cellular and humoral responses to influenza in Gabonese children living in rural and semi-urban areas

Background. With the current attention to the pandemic threat of avian influenza viruses, it is recognized that there is little information on influenza in Africa. In addition, the effects of influenza vaccination in African countries could be very different from the effects in regions with less exposure to microorganisms and parasites. Methods. To monitor the presence of influenza viruses and investigate the immunological responses to influenza vaccination, schoolchildren in semi-urban and rural regions of Gabon were studied. Influenza-specific antibody responses to the 3 strains represented in the vaccine were determined in the serum. Furthermore, cytokine responses were measured after in vitro stimulation of whole blood by influenza antigens, before and after vaccination. Results. Prevaccination titers of antibody against H3N2 were high. At vaccination, the titers of antibody against the 3 influenza strains increased significantly. The anti-H1N1 and anti-B responses after vaccination were weaker in rural schoolchildren than in semi-urban schoolchildren. Influenza-specific cytokine responses were induced within a week, showing significantly lower interferon-gamma and significantly higher interleukin-5 in the children from rural areas. Conclusions. Prevaccination antibody levels indicated that influenza viruses circulate in Gabon. Altogether, influenza vaccination induces weaker immune responses in a rural population than in a semi-urban population of Gabonese schoolchildren.