Infection of bone marrow macrophages by equine infectious anemia virus.

Objective: To characterize infection of bone marrow-derived macrophages (BMDM) with equine infectious anemia virus (EIAV) by determining virus production, effects on viability, and induction of cytokines.

Sample Population: BMDM obtained from bone marrow of 6 clinically normal adult horses.

Procedure: BMDM were infected with EIAV at a multiplicity of infection of 8. Cell viability, percentage of cells with detectable viral protein, reverse transcriptase activity, and concentrations of infective virus (focus-forming units/ml), interleukin 6, and tumor necrosis factor-alpha were measured in culture supernatant samples obtained at various days after infection.

Results: Cell viability was decreased on day 4 and was maximally decreased on day 8. The number of cells with detectable viral protein and supernatant reverse transcriptase activity increased significantly on day 4 and increased until day 6. Virus concentration (focus-forming units per milliliter) peaked on day 4 after infection and was constant thereafter. Infection with EIAV caused significant induction of interleukin 6 production by BMDM. The maximal difference was seen on day 4 after infection. Control and infected BMDM produced only negligible amounts of tumor necrosis factor-alpha.

Conclusions: BMDM are useful, as a cell population, to study the effects of infection with EIAV, including cell death and induction of interleukin 6 but not tumor necrosis factor-alpha production.