Phorbol ester stimulation of equine macrophage cultures alters expression of equine infectious anemia virus

Endotoxin treatment of equine infectious anaemia virus-infected horse macrophage cultures decreases production of infectious virus.

“…Results from our experiments indicate that the early events of EIAV replication, up to and including transcription of multiplespliced mRNAs, are not inhibited by treatment of EIAVinfected macrophages with bacterial endotoxin. This is consistent with the previous findings of Sellon et al (1996), who found no differences in inhibition of EIAV replication among molecularly cloned EIAVs with LTRs predicted to differ in transcriptional response to PMA activation. Interestingly, our studies indicate that the predominant effect of endotoxin treatment on EIAV replication occurred post-transcriptionally and appeared to be associated with a delayed appearance of single-spliced mRNA.…”

“…Similar inhibition of virus replication following macrophage activation was found following treatment of EIAV-infected macrophages with phorbol myristate acetate (PMA) (Sellon et al, 1996) or HIV-infected monocytes with bacterial LPS (Kornbluth et al, 1989). Activated macrophages may exert indirect antiviral effects mediated by IFN.…”

“…It is possible that a cytokine-mediated intracellular antiviral process is activated by endotoxin treatment of HMCs. Elevated levels of TNF-α were found in endotoxin-stimulated HMCs, and Sellon et al (1996) reported similar increases in TNF-α in PMA-stimulated macrophages. We observed no direct correlation between the level of TNF-α and virus titre, suggesting that TNF-α is not the direct or sole inhibitor of EIAV replication.…”

“…However, phorbol ester stimulation of primary equine macrophages was shown to decrease production of EIAV reverse transcriptase activity (Sellon et al, 1996). To characterize the cellular factors important in regulation of EIAV replication, we examined the effect of macrophage variability and activation on EIAV replication in primary horse macrophage cultures (HMCs) in vitro.…”

Regulation of Equine Infectious Anemia Virus Expression

“…In contrast to the potential enhancing effect of PMA on EIAV LTR/CAT activity, treatment of EIAV-infected macrophages with PMA or bacterial lipopolysaccharides (LPS) suppressed levels of supernatant reverse transcriptase activity [107] and virus infectivity [111]. These findings are surprising in light of the stimulatory effect these agents can have on HIV expression [34, 77,81].…”