INDUCTION OF ANTIBODIES TO THE BLUETONGUE VIRUS CORE POLYPEPTIDE VP7 IN SHEEP BY INTERNAL IMAGE RABBIT ANTIIDIOTYPIC ANTIBODIES

We previously generated rabbit polyclonal antiidiotypic antibody (anti -Id) to a murine monoclonal antibody (M1875) specific for the bluetong ue virus core protein VP7, and demonstrated that this anti-Id (designa ted RAb2-A) had the characteristics of an internal image anti-Id (Ab2 beta), In this communication, RAb2-A was used to induce immune respons es in sheep and the responses were compared to immunization with VP7, The immune sera were tested for the presence of anti-VP7 antibodies an d the expression of the Id of M1875, Animals immunized with RAb2-A wer e able to produce M1875-like antibody responses, i.e., they recognized the same or a similar epitope as M1875 and possessed the M1875 Id, wi thout subsequent exposure to the original antigen. This was demonstrat ed by showing that antibodies induced by RAb2-A (i) reacted specifical ly with the immunizing anti-Id, (ii) were capable of binding VP7, (iii ) inhibited M1875 from binding to VP7, and (iv) inhibited M1875 from b inding to RAb2-A, Animals immunized with purified VP7 produced antibod ies that possessed the epitope and idiotope specificity of M1875, No a ntibody responses to VP7 were detected in control animals immunized wi th either rabbit anti-Id to the pseudorabies virus glycoprotein gIII o r BHK-21 cell proteins. We conclude that rabbit anti-Id RAb2-A serolog ically mimics an M1875-defined VP7 epitope sufficiently to function as a surrogate antigen for inducing anti-bluetongue virus VP7 responses.