PROTECTION OF IMMUNIZED AND PREVIOUSLY INFECTED CHIMPANZEES CHALLENGED WITH MYCOPLASMA-PNEUMONIAE

Following immunization, peak geometric mean serum metabolism inhibitio n antibody (MIT) titres were 1.13 and 1.16 for groups of three chimpan zees each that received either the formalin-inactivated OSU-1A or expe rimental acellular extract vaccine, respectively. Following challenge, the mean titres for chimpanzees given the acellular vaccine peaked at 1:256 in 4 weeks and was 1.48 at 10 weeks. Chimpanzees given the OSU- 1A vaccine peaked at 1.80 in 4 weeks and remained at 1:80 at 10 weeks. There was no direct correlation between the serum MIT response and th e severity of disease or colonization, and thus the MIT response was n ot a reliable measurement of protection. The two non-immunized chimpan zees showed significant signs of disease, including cough, pharyngitis , rhinitis, fever and abnormal X-ray findings, for about 5 weeks. The chimpanzees immunized with either vaccine were less colonized and show ed far less disease than non-immunized controls. Protection afforded t he chimpanzees was similar to that of vaccinees in the human clinical trial given the same OSU-1A vaccine (Wenzel et al., 1977). The two pre viously infected chimpanzees were most protected against colonization and disease on challenge.