Indirect immunofluorescence, serum neutralization, and viremia responses of rhesus monkeys (Macaca mulatta) to Machupo virus.

Although indirect immunofluorescent antibody tests (IFAT) have been developed for several arenaviruses, none has been applied to the rhesus monkey model for Bolivian hemorrhagic fever (caused by the arenavirus Machupo). We infected eight rhesus monkeys with Machupo virus and bled them weekly for determination of viremia and for serum antibody detection by IFAT and serum neutralization (SN) testing. Viremia peaked day 14 post-inoculation (PI), when two of eight animals had low IFAT titers. At day 21 PI, the six surviving monkeys had elevated IFAT titers and diminished viremias. SN titers were not observed until 28 days PI, when three of four survivors had low titers. Results of the IFAT were available more rapidly than the SN, and detected increased serum antibody titers earlier than the SN. Acetone fixation did not completely inactivate BHF antigen spot slides.