Background: Lassa virus (LAV) isolates obtained from Sierra Leone, Ivory Coast and Nigeria show a high degree of amino acid difference [Gunther S, Weisner B, Roth A, Grewing T, Asper M, Drosten C, et al. Lassa fever encephalopathy: Lassa virus in cerebrospinal fluid but not in serum. J Infect Dis 2001;184:345-9]. Therefore, three LAV strains from Sierra Leone, Ivory Coast and Nigeria were used as antigens to study the anti-LAV antibody response in 960 serum samples obtained from different regions of west Africa.
Study design: The antibody response to LAV was studied both by a standard indirect immunofluorescence assay (IFA) and by a highly sensitive reverse ELISA [Emmerich P, Thome-Bolduan C, Drosten C, Gunther S, Ban E, Sawinsky I, et al. Reverse ELISA for IgG and IgM antibodies to detect Lassa virus infections in Africa. J Clin Virol 2006;37:227-81].
Results: In 88 of the 960 subjects from west African countries (Guinea, Liberia, Ivory Coast, Ghana, Benin, and Nigeria) anti-Lassa antibodies were detected with both assays. Significant titer differences and clustering analysis revealed strain-specific antibodies in 64 of the 88 positive samples. Depending on the geographic origin of the samples, up to 32% of anti-LAV antibody positive samples would not have been detected, if only the IFA had been run with LAV prototype strain Josiah. In 20 patients with acute Lassa fever differences in antibody titer between the three LAV antigens were not observed.
Conclusions: Our data suggest that antigens prepared of regional LAV strains should be applied when seroprevalence studies are conducted in various parts of west Africa.