Abstract
Human whipworm (Trichuris trichiura) infects approximately 1 in 15 people worldwide, representing the leading infectious cause of colitis and subsequent, inflammatory bowel disease (IBD). Current control measures focused on mass deworming have had limited success due to low drug efficacies. Vaccination would be an ideal, cost-effective strategy to induce protective immunity, leading to control of infection and transmission. Here we report the identification of whey acidic protein, a whipworm secretory protein, as a strong immunogen for inducing protective efficacy in a surrogate mouse T. muris infection model. The recombinant WAP protein (rTm-WAP49), as well as a single, highly conserved repeat within WAP (fragment 8) expressed as an Na-GST-1 fusion protein (rTm-WAP-F8+Na-GST-1), generate a strong T helper type 2 (Th2) immune response when delivered as subcutaneous vaccines formulated with Montanide ISA 720. Oral challenge with T. muris infective eggs following vaccination led to a significant reduction in worm burden of 48% by rTm-WAP49 and 33% by rTm-WAP-F8+Na-GST-1. The cellular immune correlates of protection included significant antigen-specific production of Th2 cytokines IL-4, IL-9, and IL-13 by cells isolated from the vaccine-draining inguinal lymph nodes, parasite-draining mesenteric lymph nodes, and spleen in mice vaccinated with either rTm-WAP49 or rTm-WAP-F8+Na-GST-1. The humoral immune correlates included a high antigen-specific ratio of IgG1 to IgG2a, without eliciting an IgE-mediated allergic response. Immunofluorescent staining of adult T. muris with WAP antisera identified the worm’s pathogenic stichosome organ as the site of secretion of native Tm-WAP protein into the colonic mucosa. Given the high sequence conservation for the WAP proteins from T. muris and T. trichiura, the results presented here support the WAP protein to be further evaluated as a potential human whipworm vaccine candidate.
Highlights
Portions of this chapter are based upon: A
While the expression of Tm-whey acidic protein (WAP) and the purification of the recombinant protein were in progress, we expressed the most conserved repeat of Tm-WAP, fragment 8, with a Necator americanus glutathione s-transferase-1 (Na-GST-1)-tag at the N-terminus and successfully produced a soluble recombinant fusion protein in E. coli
The resulting recombinant protein, rTmWAP-F8+Na-GST-1 was tested for immunogenicity along with recombinant Tm-CAP-1 protein in the AKR mouse model
Summary
Portions of this chapter are based upon: A. The closely related Trichuris muris parasite, specific to mice, is a well-established surrogate model for human T. trichiura disease pathophysiology and subsequent host immunity, used for evaluating the immunogenicity and efficacy of vaccine candidates [13, 14]. Using a whipworm animal model, we immunized mice with candidate antigens to evaluate immunity, as well as protection against subsequent T. muris challenge infection (Chapter III). Data from these studies identified Tm-WAP, derived from the Tm-ES, as a strong TH2 immunogen that elicits protection when administered as a recombinant near full-length (rTm-WAP49) or fragment-fusion protein (rTm-WAP-F8+Na-GST-1) co-formulated with Montanide ISA 720 adjuvant. We hypothesize this is due, at least in part, to an immune mediated mechanism of protection after multiple early exposures to the parasite
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