Molecular mimicry between Fc receptors and viral antigens.

Molecular mimicry has been characterized as the presence of common epitopes, either linear or conformational, shared by host and microbial determinants. Such cross-reactivity may lead to an autoimmune disease. On the other hand molecular mimicry between certain viral proteins and host determinant may protect invading virus to be eliminated by immune system and may promote persistence. In this mini-review I discuss the molecular mimicry of S peplomer protein of mouse hepatitis virus, strain JHM (MHV-JHM) to the host Fc gamma receptor (Fc gamma R). MHV-JHM induces in rodents acute encephalomyelitis and surviving animals develop demyelinating disease with concomitant persistent infection. We have demonstrated that rabbit IgG, but not is F(ab')2 fragments, monoclonal rat and mouse IgG and the rat 2.4G2 anti-Fc gamma R mab immunoprecipitated natural and recombinant S peplomer protein of several strains of MHV. Furthermore, MHV-JHM infected cells formed rosettes with anti-sheep red blood cell (SRBC) - antibody coated SRBC. The 2.4G2 anti-Fc gamma R mab are able to neutralize several strains of MHV, presumably by binding to S peplomer protein. Therefore, the Fc binding site of S is present on the surface of MHV-infected cells. This molecular mimicry between S peplomer protein of MHV-JHM and Fc gamma R has been extended to other members of Coronaviridae, namely bovine coronavirus and transmissible gastroenteritis virus but not to infectious bronchitis virus. The molecular mimicry of viral antigens to Fc receptors has been described also for members of Herpesviridae, namely Herpes simplex, cytomegalovirus and Varicella zoster.(ABSTRACT TRUNCATED AT 250 WORDS)