A horse may serve the producer of immune antiserum to Lassa virus. Spe
cific immunoglobulin with at least 1:512 titer of virus-neutralizing a
ntibodies to Lassa fever was obtained by alcohol sedimentation after C
ohn from the blood serum of immunized horses. The preparation does not
differ from heterologous commercial immunoglobulins. Preclinical stud
ies of immunoglobulin to Lassa fever demonstrated its safety and a hig
h specific activity. The agent can be injected both alone and in combi
nation with virasole.