Nucleoprotein, virus-specific IgM and IgG detection by ELISA in G-1442, normal, and contact G-1446 sera. An Ag capture ELISA was used to detect LASV NP in patient sera (A). LASV NP Ag was not detected in normal sera from Sierra Leonean origin, or in contact G-1446. The level of LASV NP Ag [blue diamond] in G-1442 dropped significantly during the first 3 days of ribavirin administration, and was undetectable by day 10. LASV-specific IgM (B) and IgG (C) were assayed in a recombinant ELISA plate format, with individually coated NP, GP1 (sGP1), GP2 (GPCΔTM), or Z proteins. One Sierra Leonean serum registered a high IgG titer to NP (NHS015), whereas the other had moderate IgM titers to NP (NHS023), but both were negative for IgG and IgM to Z and glycoproteins. NP-specific IgM and IgG levels in G-1442 rose throughout the course of the illness, through day 20. Contact G-1446 did not have measurable IgG titers, and only registered a low IgM titer to Z. Data are plotted as mean A450 ± SD, N = -2. The line between day 18 and 20 is dotted to reflect discontinuity on day 19.