Immune Response to Marburg Virus Angola Infection in Nonhuman Primates

Background. The 2005 outbreak of Marburg virus (MARV) infection in Angola was the most lethal MARV infection outbreak in history, with acase-fatality rate (90%) similar to that for Zaire ebolavirus (EBOV) infection. However, very little is known about the pathogenicity of MARV Angola, as few studies have been conducted to date. Therefore, the immune response was examined in MARVAngola–infected nonhuman primates. Methods. Cynomolgus macaques were infected with MARVAngola and monitored for survival. The effect of MARVAngola on the immune system was examined by immunophenotyping whole-blood and by analyzing cytokine and chemokine levels in plasma and spleen specimens, using flow cytometry. Results. The prominent clinical findings were rapid onset of disease and death (mean time after infection, 6.7 days), fever, depression, anorexia, petechial rash, and lymphopenia. Specifically, T, B, and natural killer cells were severely depleted in the blood by day 6. The typical cytokine storm was present, with levels of interferon γ, tumor necrosis factor, interleukin 6, and CCL2 rising in the blood early during infection. Conclusions. MARV Angola displayed the same virulence and disease pathology as EBOV. MARV Angola appears to cause a more rapid onset and severe outcome of infection than other MARV strains.