Optimization and qualification of a memory B-cell ELISpot for the detection of vaccine-induced memory responses in HIV vaccine trials

Various aspects of the human immune system can be analyzed to determine the efficacy of a vaccine. We have developed a B-cell ELISpot to measure HIV-specific antibody-secreting B cells in the peripheral blood as a result of vaccination or natural infection. Our method includes stimulating peripheral blood mononuclear cells with interleukin-2 and a polyclonal activator, R848, to induce memory B cells to differentiate into antibody-secreting cells. Total immunoglobulin-secreting as well as antigen-specific B cells are then quantified. We have tested several HIV Env gp120 and gp140 proteins from different HIV subtypes, as well as a sensitive consensus group M Env gp140. Our findings indicate that the B-cell ELISpot provides a sensitive and specific tool to detect antigen-specific memory B-cell responses, and it is equally suited to detect antibody-secreting plasmablasts present in the circulation shortly after infection or vaccination.