Lymphoproliferative responses after infection with human parvovirus B19

Immunity after infection with the parvovirus B19 is assumed to be conferred by a humoral immune response with development of neutralizing antibody. In contrast, little is known about the nature of T-cell-mediated responses to parvovirus B19 infection in humans. We used recombinant proteins VP1, VP2, and NS1, as well as a recombinant VP1-specific amino-terminal sequence, to test the proliferative responses of peripheral blood mononuclear cells after infection of otherwise healthy individuals with parvovirus B19. These proteins were used as antigens for the stimulation of freshly isolated cells. The results show that a B19 virus-specific cellular immunity develops that is directed against the capsid proteins VP1 and VP2. We also demonstrate that viral determinants are presented to CD4+ T cells by HLA class II molecules.