|Knowles Jr, Donald|
Submitted to: Infection and Immunity
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/27/1999
Publication Date: N/A
Interpretive Summary: This manuscript describes the first report of a successful stimulation of immune responses in cattle with a gene from Anaplasma marginale. The significance of this discovery is the confirmation of the possibility of a DNA based vaccine for this important disease of cattle. One of the significant advantages of delivering a vaccine through DNA is safety. This method avoids the possibility of disease and the possibility of contamination with other pathogens (modified live vaccine preparations).
Technical Abstract: Immunization with the native major surface protein 1 (MSP1) (a heterodimer containing disulfide and non-covalently bonded polypeptides designated MSP1a and MSP1b) of the erythrocytic stage of A. marginale conferred protection against homologous challenge (G. H. Palmer, A. F. Barbet, W. C. Davis, and T. C. McGuire, Science, 231:1299-1302). The MSP1a polypeptide possesses a conserved neutralization-sensitive epitope. In the present study, the immune response to DNA mediated immunization using msp1a was studied. The plasmid pVCL/MSP1a, which encodes the complete msp1a gene of A. marginale under the control of human cytomegalovirus immediate early enhancer/promoter and intron A, was constructed. The immune responses elicited by immunization with pVCL/MSP1a into cardiotoxin- induced regenerating muscle were evaluated in mice and cattle. Antibody reactive with native MSP1a was detected in pooled sera of immunized Balb/c mice 3 weeks following primary immunization. Two calves seronegative for A. marginale were immunized four times at weeks 0, 3, 7 and 13 with pVCL/MSP1a. By eight weeks, both calves responded to MSP1a with an antibody titer of 1:100, which peaked at 1:1600 and 1:800 by 16 weeks after the initial immunization. Interestingly, immunoblotting with anti-IgG1 and -IgG2 specific monoclonal antibodies revealed a restricted IgG1 anti-MSP1a response in both animals. T-lymphocyte lines, established after the fourth immunization, proliferated specifically against A. marginale homogenate and purified MSP1 in a dose-dependent manner. These data provide a basis for an immunization strategy.