ENDOTOXIN TREATMENT OF EQUINE INFECTIOUS-ANEMIA VIRUS-INFECTED HORSE MACROPHAGE CULTURES DECREASES PRODUCTION OF INFECTIOUS VIRUS

Lentiviruses replicate in cells of the immune system, and activation o f immune cells has been shown to modulate virus replication, To determ ine the effects of macrophage activation on replication of equine infe ctious anaemia virus (EIAV), primary horse macrophage cultures (HMCs) were established from 20 different horses, infected with an avirulent strain of EIAV, and stimulated with 5 mu g/ml of bacterial endotoxin. Supernatants collected from HMCs were assayed for the presence of tumo ur necrosis factor (TNF-alpha) and for production of infectious virus, Results indicated that EIAV replication in vitro varied significantly (P less than or equal to 0.0001) from horse to horse, regardless of t he treatment of HMCs, Also, EIAV replication was significantly (P less than or equal to 0.0001) decreased in HMCs stimulated with bacterial endotoxin as compared to untreated HMCs, No significant correlation wa s found between virus replication and production of TNF-alpha followin g treatment of virus-infected cells with bacterial endotoxin, However, when HMCs were treated with endotoxin prior to virus infection, inhib ition of EIAV replication was proportional to increasing levels of end otoxin, PCR and RT-PCR were used to amplify EIAV proviral DNA and mRNA sequences, respectively, at various time-points following infection, The results indicated that the early events of EIAV replication, up to and including transcription of multiple-spliced mRNAs, were not inhib ited by treatment of EIAV-infected macrophages with bacterial endotoxi n, This suggests that endotoxin treatment inhibits a post-transcriptio nal step in the virus replication cycle.