Myelopoiesis in vitro is suppressed by hepatitis A virus

Perturbations of hematopoietic regulation ranging from transient granulocytopenia to rare cases of bone marrow failure are associated with infections due to hepatitis A virus (HAV). In an attempt to elucidate the pathogenetic mechanisms we had previously established that HAV has a direct suppressive effect on human bone marrow progenitors (CFU-GM, -GEMM, BFU-E). These studies were extended to long-term bone marrow cultures (LTBMC): Inoculation of bone marrow mononuclear cells with HAV did not interfere with the establishment of an adherent stromal layer, nor did the inoculation of already established layers cause any morphologically recognizable changes to the stroma. In contrast, a significant and progressive decline of the CFU-GM content in the culture supernatants was demonstrated. HAV antigen was detected by APAAP stain in a subpopulation of stromal cells, and sequential estimations of virus titers in the supernatants provided evidence for viral replication in primary bone marrow cultures. Interferon-gamma and tumor necrosis factor-alpha levels of infected cultures did not differ from those of uninfected controls. These findings argue for a direct suppression of (pre-) CFU-GM by HAV in a model system (LTBMC) lacking an immune defense which would limit viral replication.