Characterization of protection against coronavirus infection by noninternal image antiidiotypic antibody

Previously, we have reported protective vaccination of mice against a coron avirus infection using rabbit polyclonal noninternal image Ab2(gamma) anti- idiotypic (anti-Id) antibody specific for a virus-neutralizing and protecti ve monoclonal antibody (mAb) 7-10A against the viral surface S glycoprotein , To characterize further the mechanisms involved in the induction of prote ctive immunity by this noninternal image anti-Id, plasma and splenocytes fr om Ab2(gamma)-immunized BALB/c mice were passively transferred to naive BAL B/c mice, followed by viral challenge. A reproducible significant delay in mortality observed in mice to which plasma was passively transferred, toget her with the presence of specific in vitro neutralizing antiviral Ab3 ident ified the humoral immune response as the major element responsible for prot ection. The activation of specific and cross-reactive T lymphocytes by both virus and anti-Id in immunized mice and the absence of adoptive transfer o f protection by splenocytes suggested the participation of T helper activit y in the induction of protective virus-neutralizing Ab3, To obtain more def ined monoclonal reagents for a better understanding of anti-Id-induced prot ection, mAb2, were generated against the same mAb1 7-10A and characterized. We report the successful generation of mAb2 of the gamma type. However, un like the polyclonal Ab2(gamma), they were not capable of inducing a protect ive immune response.