Isolation of Rift Valley fever virus from human peripheral blood mononuclear cells: Mauritanian epidemic

During the Mauritanian Rift Valley fever (RVF) epidemic of 1987, peripheral blood mononuclear cells (PBMC) were studied from 78 sick patients. RVF virus (RVFV) was isolated in 5 cases, on Aedes pseudoscutellaris AP61, from both PBMC and serum. Among the 78 cases studied, RVF was proven in 19 cases (24.3%) by specific IgM detection, and in 12 cases (15.3%) by virus isolation from serum, of which 3 also exhibited anti-RVF IgM. Among the 5 PBMC-positive RVFV cases, 2 strains were isolated in the presence of specific IgM from patients presenting with neurologic signs. These observations raised the question as to the role of specific IgM in cellular infection, and suggest that, in certain cases, mononuclear cells may promote RVFV dissemination into brain cells. Further investigations need to be undertaken to determine the RVFV receptor expressed on PBMC membranes.