Circulating natural killer and γδ T cells decrease soon after infection of rhesus macaques with lymphocytic choriomeningitis virus

Rhesus macaques infected with the WE strain of lymphocytic choriomeningitis virus (LCMV-WE) serve as a model for human infection with Lassa fever virus. To identify the earliest events of acute infection, rhesus macaques were monitored immediately after lethal infection for changes in peripheral blood mononuclear cells (PBMCs). Changes in CD3, CD4, CD8 and CD20 subsets did not vary outside the normal fluctuations of these blood cell populations; however, natural killer (NK) and γδ T cells increased slightly on day 1 and then decreased significantly after two days. The NK subsets responsible for the decrease were primarily CD3-CD8+ or CD3-CD16+ and not the NKT (primarily CD3+CD56+) subset. Macaques infected with a non-virulent arenavirus, LCMV-Armstrong, showed a similar drop in circulating NK and γδ T cells, indicating that this is not a pathogenic event. V³9 T cells, representing the majority of circulating γδ T cells in rhesus macaques, displayed significant apoptosis when incubated with LCMV in cell culture; however, the low amount of cell death for virus-co-cultured NK cells was insufficient to account for the observed disappearance of this subset. Our observations in primates are similar to those seen in LCMV-infected mice, where decreased circulating NK cells were attributed to margination and cell death. Thus, the disappearance of these cells during acute hemorrhagic fever in rhesus macaques may be a cytokine-induced lymphopenia common to many virus infections.

Tales of mice and men: Natural History of Arenaviruses

Nowadays, Arenaviruses are among  the most feared viruses due to their potential as weapons for bioterrorism purposes. This potential is based on their increasing diversity and the fact that they are carried by rodentswhose biologic success compares only wit insects and humans. The prototype of this family is  Lymphocytic Choriomeningitis Virus which has been and excellent tool for a myriad of discoveries in immunology. Arenaviruses have been known for over 70 years but the number of members of the family is growing thanks to their insidious subsistence in third world countries and to the nature of their   genome, that makes of them sorts of skilful machines for evolution This review collects some of the work of the authors about the best-known features described for this group of viruses, among the many still-to-be discovered characteristics of this puzzling, and hard-to-study, group of zoonotic viruses.