This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Hallett, A. F. Articles by Meyer, K. F. Search for Related Content PubMed PubMed Citation Articles by Hallett, A. F. Articles by Meyer, K. F.

 Previous Article  |  Next Article 

Infect Immun. 1973 December; 8(6): 876-881
Copyright © 1973 American Society for Microbiology. All Rights Reserved.

Pathogenicity and Immunogenic Efficacy of a Live Attenuated Plague Vaccine in Vervet Monkeys

Medical Ecology Centre, State Department of Health, and Department of Microbiology, South African Institute for Medical Research, Johannesburg, Republic of South Africa
The George Williams Hooper Foundation, University of California Medical Center, University of California, San Francisco, California 94143

ABSTRACT

A live attenuated Yersinia pestis (Pasteurella pestis) vaccine strain designated EV51f, which had been passaged through guinea pigs previously treated with ferrous sulfate, was shown to be pathogenic for African green vervet monkeys (Cercopithecus aethips pygerythrus), but not for guinea pigs. The bacilli multiplied in the monkeys, as shown by positive blood cultures, caused an elevation of white cell counts and rectal temperatures, and resulted in death of 26% (13/50) of animals. Postmortem findings of these animals were typical of bubonic-septicemic plague. This vaccine did not cause deaths in 50 guinea pigs even in doses up to 100 million viable bacilli inoculated subcutaneously. It is suggested that the virulence of an attenuated Y. pestis strain which does not produce pigment on a defined medium containing hemin, but possesses all other known virulence determinants, is dependent on the availability of iron in vivo. The serological response of the monkeys as determined by the hemagglutinating and mouse protective antibodies was high one month after vaccination and also in guinea pigs, as shown by virulent challenge. This antibody level declined in monkeys over a period of nearly 6 months, and a decline in immunity was confirmed by virulent challenge which resulted in the death of 30% of vaccinated monkeys. The level of immunity in monkeys did not appear to be related to the dose of vaccine.

¹ Present address: Department of Microbiology, Faculty of Medicine, University of Natal, Durban, South Africa.