Immunization against Brucella infection. 8. The response of Cynomolgus philippinensis, guinea-pigs and pregnant goats to injection by the Rev I strain of Brucella melitensis.

Experiments have been carried out on monkeys, goats and guinea-pigs to define as closely as possible the degree of attenuation of the Rev I strain of B. melitensis. Earlier studies had conclusively demonstrated the effectiveness of the strain as an immunizing agent of the three animal species and had suggested that the degree of attenuation was such as to warrant limited study in humans. Results of such a limited study suggested more intensive measurement of the virulence of the strain in other stocks of animals as well as in individual animals rendered increasingly susceptible. A comparison of Rev I with B. abortus, strain 19-BA, and with a fully virulent strain of B. melitensis in guinea-pigs confirmed that the BA strain was more attenuated than Rev I. Cynomolgus monkeys were effectively immunized by Rev I and showed temporary signs of generalized infection. Human isolates of the Rev I strain were striking in the temporary infectivity possessed by rough colony types.