[Study of bone marrow in experimental Argentine Hemorrhagic Fever. Role of the megakaryocyte]

In previous morphological studies on bone marrow of guinea pigs infected with Junin virus, the coexistence of viral particles, antigens and cytopathic effects were observed in megakaryocytes. In addition, bone marrow is one of the organs where highest virus titers were obtained. However, although other myeloid cells presented intense cytopathic effect, viral antigens were observed only in reticular cells and virus particles were seen sporadically associated with immature cells. This study was designed to investigate if bone marrow infetivity was due mainly to megakaryocyte infection. Megakaryocyte obtained from infected bone marrow were concentrated in albumin gradients by gravitational sedimentation. Enriched fractions were studied by immunofluorescense /IF) and virus titration. Results showed that fractions containing 8, 6.4 or 15 % of megakaryocytes had titers of 3.81, 4.23 and 2.7 LD50/mñ respectively. On the contrary in depleted fractions (0 % megakaryocytes), titers were 0,5 to 1 log lower (Fig. 1, Table 1). By IF, Junin antigens were located in the cytoplasm of 70 % of megakaryocytes and also in reticular cells, but not in other cell types. These results suggest that megakaryocytes suffer a productive infection that may well account for the thrombocytopenia observed in this experimental infection. However, the detection of infectivity in other cells, in absence of viral antigens and particles remains to be explained.