Poster Session PO137: HIV impairs avidity maturation to EPI vaccines in children

Purpose/Objective:

HIV-infected adults and children have reduced quantities of antibodies and memory B cells to non-HIV antigens. On the other hand, avidity of antibodies to vaccine antigens is not affected by HIV in adults, probably because they have already experienced avidity maturation to most routine vaccine antigens prior to infection. Little is known regarding avidity maturation in children infected with HIV. Here, we analysed the avidity of antibodies against tetanus toxoid and diphtheria toxoid in children who acquired HIV vertically. We also measured the quantities of circulating antibodies and frequencies of memory B cells to vaccine antigens.

Materials and methods:

Memory B-cell frequencies were determined using cultured B-cell ELISpot. ELISA was used to determine the antibody levels while a modified ELISA was used to determine the antibody avidities. In the modified ELISA, Guanidine Hydrochloride was used to elute the antibodies after incubating the plasma (sample)with the antigen-coated plates. The ratio of the remaining antibody levels in the eluted wells to that in the control (PBS eluted) wells was taken as the avidity index. The children were then classified based on their viral loads and compared with community controls.

Results:

HIV-infected children, regardless of level of viremia, had significantly lower avidity indices when compared with the community controls. As previously reported, they also had lower titres of circulating antibodies as well as lower frequencies of antigen specific memory B cells.

Conclusions:

HIV affects not only the magnitude but also the quality of antibody response to vaccine antigens in vertically infected children.