Complement fixation tests were done on 296 sera taken up to 15 months after illness from 94 serologically confirmed cases of Bolivian hemorrhagic fever. One hundred seventy-two sera were tested against Machupo, Junín and Tacaribe virus antigens; most of the others were tested only against Machupo virus antigen. Highest titers usually appeared between 40 and 60 days after onset of illness. Tacaribe virus antigen was the least effective in the detection of complement-fixing antibody to Machupo virus.
The sera of some persons reacted only to low titers six months or more after illness. Certain sera from presumed negative controls were also found to react at low dilutions, possibly as a result of subliminal anticomplementary activity of reagents. However, it appears that the complement fixation test can be of value in the study of specific illnesses or, in certain circumstances, of epidemics caused by Machupo virus, and that antigens prepared from Machupo or Junín viruses are about equally effective.
Department of Health, Education, and Welfare, U. S. Public Health Service, National Institutes of Health, National Institute of Allergy and Infectious Diseases.
Present address: Yale Arbovirus Research Unit, Yale University School of Medicine, New Haven, Conn.