Characterization of Protection Against Coronavirus Infection by Noninternal Image Antiidiotypic Antibody

Abstract

Previously, we have reported protective vaccination of mice against a coronavirus infection using rabbit polyclonal noninternal image Ab2_γ anti-idiotypic (anti-Id) antibody specific for a virus-neutralizing and protective monoclonal antibody (mAb) 7-10A against the viral surface S glycoprotein. To characterize further the mechanisms involved in the induction of protective immunity by this noninternal image anti-Id, plasma and splenocytes from Ab2_γ-immunized BALB/c mice were passively transferred to naive BALB/c mice, followed by viral challenge. A reproducible significant delay in mortality observed in mice to which plasma was passively transferred, together with the presence of specific in vitro neutralizing antiviral Ab3 identified the humoral immune response as the major element responsible for protection. The activation of specific and cross-reactive T lymphocytes by both virus and antiId in immunized mice and the absence of adoptive transfer of protection by splenocytes suggested the participation of T helper activity in the induction of protective virus-neutralizing Ab3. To obtain more defined monoclonal reagents for a better understanding of antiid-induced protection, mAb2 were generated against the same mAbl 7-10A and characterized. We report the successful generation of mAb2 of the γ type. However, unlike the polyclonal Ab2_γ, they were not capable of inducing a protective immune response.