Induction of a protective immune response to murine coronavirus with non-internal image anti-idiotypic antibodies

Neurotropic murine coronaviruses (MHV) provide an excellent animal model to study experimental modulation of the immune response to a viral pathogen with anti-idiotypic antibodies. It is known that among the various types of anti-idiotypic antibodies (anti-Id), those designated beta (beta) or internal image can molecularly mimic the antigen and induce biological activities such as anti-viral protection and neutralization. We have recently shown that polyclonal non-internal image anti-idiotypic antibodies of the gamma-type could induce protective anti-coronavirus immunity. In the present study, a polyclonal anti-Id (Ab2) was induced against a neutralizing murine monoclonal antibody (MAb1), designated 5B170.11. Mice immunized with this affinity-purified rabbit Ab2 alpha, a non-internal image antibody, were partially protected against lethal infection by the JHM strain of MHV. However, other polyclonal and monoclonal non-internal image Ab2 induced against another neutralizing Mab1, designated 4-11G.6, were not able to protect mice against lethal infection with the A59 strain of MHV. These results demonstrate that anti-viral protection by altering the idiotypic network with non-internal image-bearing anti-idiotype reagents can be achieved even with some anti-Id of the alpha-type.