DEVELOPMENT OF THE PIG AS A SECOND SPECIES MODEL FOR TESTING VACCINES AND ADJUVANTS
Animal Parasitic Diseases
2010 Annual Report
1a.Objectives (from AD-416)
Identify functional genetic variations that modulate the immune responses to swine mucosal pathogens; and determine the genetic profiles of ”good responders” to swine vaccines.
1b.Approach (from AD-416)
Out-bred commercial breeds of swine will be vaccinated with recombinant products from bacterial and viral pathogens by various routes including mucosal exposure with novel and conventional adjuvants and vaccine platforms. Local and systemic responses to vaccination will be evaluated by measuring antigen specific antibody isotype responses in the serum, and eye, lung, and intestinal fluids, and local and whole blood changes in cytokine and chemokine biomarkers by gene expression. This information will be used by both ARS and the COOPERATOR to jointly develop novel adaptive and acquired immune readout systems to evaluate vaccine efficacy as it applies to swine directly and as a second species for testing important new vaccine constructs.
Bacillus anthracis (Anthrax) is a potentially lethal disease of humans and other mammals (primarily herbivores) that is caused by the spore-forming bacterium, B. anthracis. Upon initial exposure to macrophages, B. anthracis rapidly geminates and disseminates throughout the host often resulting in septicemia. The principal virulence factor of B. anthracis is a multi-component toxin secreted by the pathogen that consists of three separate gene products designated protective antigen (PA), lethal factor (LF) and edema factor (EF). PA is the central molecule in the development of toxicity as cleaved PA binds to human capillary morphogenesis protein 2 or tumor endothelial marker 8 where it provides binding sites for EF and LF. Protection against anthrax is associated with a humoral antibody immune response directed against PA and possibly EF and LF. Pigs were immunized intramuscularly with purified PA in alum and boosted three times with similar injections over a period of 3 months. Antibody levels were compared between PA-immunized and sham-immunized pigs by direct ELISA using PA antigen coated plates and the Anthrax toxin neutralization assay used as an indicator of protection against infection. The assays indicated strong IgG1 and IgG2 antibody responses to PA and high levels of neutralizing antibody compared to low background levels in the control pigs. These results provided a proof of principle that pigs can be used to evaluate protective responses and determine vaccine efficacy against anthrax as a model for human infection.
Information between the collaborating laboratories was conveyed by periodic e-mails and conference calls, and a once a year visit to discuss the data accumulated and plans for future research.