was presented for both categories, but there was not enough time to cover the entire range of available or potential approaches. Two presentations addressed current and future opportunities for vaccine development. One presentation addressed the role and effectiveness of behavior change and another addressed vector-control strategies.
Jere W. McBride, Ph.D., M.S., Center for Biodefense and Emerging Infectious Diseases, University of Texas Medical Branch at Galveston
Currently, no tick-borne disease vaccines for humans are licensed in the United States. The U.S. Food and Drug Administration licensed a vaccine for Lyme disease in 1998 and it was withdrawn from the market in 2002. While the vaccine—based on outer surface protein A (OspA) emulsified in aluminum hydroxide adjuvant—prevented transmission of Borrelia burgdorferi from ticks to humans by killing spirochetes in ticks, three doses were needed to provide 80 percent protection against infection. A number of problems contributed to the withdrawal of the vaccine. The antibody titers did not persist for long time periods, which required individuals to receive multiple boosters to maintain protective immunity. Furthermore, a number of autoimmune-related side effects, including arthritis and neuropathology, were reported to possibly be associated with the vaccine (Schuijt et al., 2011). A short stretch of amino acids in OspA with the potential for molecular mimicry with human LFA-1 (lymphocyte function associated antigen) was identified as a possible cause for the autoimmune-related responses, but this finding remains controversial (Steere et al., 2001; Ball et al., 2009). In Europe, current efforts are focused on developing vaccines with a modified OspA that does not contain the sequence linked to autoimmune responses. Other vaccines for Borrelia are in varying stages of development as either single- or multiple-antigen vaccines that include OspB, OspC, or DNA-binding protein HU-alpha.
Experimental veterinary vaccines for bovine anaplasmosis and infection and treatment strategies for heartwater—an ehrlichiosis of ruminants—demonstrate that vaccines for human rickettsial diseases are feasible. To develop such vaccines, however, some basic research on these emerging infectious diseases needs to be done, including:
Defining immunoprotective pathogen proteins;
Understanding and defining pathogen antigenic variation;
Understanding variations in pathogenicity;
Understanding protective immune mechanisms;