Interactions between viruses and lymphocytes. I. In vivo replication of lymphocytic choriomeningitis virus in mononuclear cells during both chronic and acute viral infections.

Abstract

Replicating virus was found in subpopulations of circulating blood mononuclear cells harvested from BALB/WEHI and SWR/J mice persistently infected with lymphocytic choriomeningitis virus (LCMV) either after intracerebral infection at birth or congenital in utero infection. Infectious virus was demonstrated by using an infectious center assay on Vero cell monolayers. Lymphoid cells isolated from both primary and secondary lymphoid organs also carried infectious virus. The number of infectious centers varied considerably from animal to animal, being as high as 10,000/10 6 and as low as 1 to 10/10 6 viable mononuclear cells. However, within any individual virus carrier mouse the numbers of infected peripheral blood mononuclear cells were found to be constant. Virus was not present in a fully infectious form either on the cell surface or within the cell. Mononuclear cells replicating LCMV were found in the bone marrow-derived (B) cell, thymus-derived (T) cell, and phagocytic, adherent cell populations. Infectious centers were also demonstrated in the peripheral blood and splenic mononuclear cells of adult mice acutely infected with LCMV. The levels of such cells rose to a peak of 100/10 6 mononuclear cells by day 3 to 4 after i.p. inoculation with virus and then decreased to below detectable levels ( 6 ) by day 8. These results indicate that after infection in utero or at birth, virus may replicate in cells of the immune system. Such infected lymphoid cells may act as a reservoir of infection throughout the animal9s life.