Virus-like display of a neo-self antigen reverses B cell anergy in a B cell receptor transgenic mouse model

The ability to distinguish between self and foreign Ags is a central feature of immune recognition. For B cells, however, immune tolerance is not absolute, and factors that include Ag valency, the availability of T help, and polyclonal B cell stimuli can influence the induction of autoantibody responses. Here, we evaluated whether multivalent virus-like particle (VLP)-based immunogens could induce autoantibody responses in well-characterized transgenic (Tg) mice that express a soluble form of hen egg lysozyme (HEL) and in which B cell tolerance to HEL is maintained by anergy. Immunization with multivalent VLP-arrayed HEL, but not a trivalent form of HEL, induced high-titer Ab responses against HEL in both soluble HEL Tg mice and double Tg mice that also express a monoclonal HEL-specific BCR. Induction of autoantibodies against HEL was not dependent on coadministration of strong adjuvants, such as CFA. In contrast to previous data showing the T-independent induction of Abs to foreign epitopes on VLPs, the ability of HEL-conjugated VLPs to induce anti-HEL Abs in tolerant mice was dependent on the presence of CD4(+) Th cells, and could be enhanced by the presence of pre-existing cognate T cells. In in vitro studies, VLP-conjugated HEL was more potent than trivalent HEL in up-regulating surface activation markers on purified anergic B cells. Moreover, immunization with VLP-HEL reversed B cell anergy in vivo in an adoptive transfer model. Thus, Ag multivalency and T help cooperate to reverse B cell anergy, a major mechanism of B cell tolerance.