Trichuris muris whey acidic protein induces type 2 protective immunity against whipworm

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.

Immunological characterization of human hosts to Ascaris lumbricoides and Trichuris trichiura infection in a population living in the rural municipality of Colomoncagua, Honduras (MPF6P.654)

Soil-transmitted helminth (STH) infections, specifically Ascaris, Trichuris, and Hookworm, compose three of the most prevalent Neglected Tropical Diseases, infecting over a billion people worldwide. Recurrent childhood STH infections have been shown to cause stunted physical growth, reduced physical fitness, and decreased school performance. Ascaris and Trichuris are of notable interest, given their abrupt decline from a peak prevalence and intensity in pre-adolescence to adulthood, with no known published works evaluating the possible underlying immunological mechanism. We used modern molecular techniques to (a) determine the burden of disease and (b) evaluate the immune profile of 30 adolescents and 51 adults between the ages 13-45, in rural Honduras, endemic for Ascaris and Trichuris. Using quantitative PCR of DNA extracted from stool we quantified the burden of disease of both Ascaris and Trichuris. Positive samples were stratified into groups based on the degree of infection, and controlled for with samples positive for 6 other common gastrointestinal parasites. Each group was immunologically characterized for serum Th1, Th2, and Th17 cytokines and associated antibodies. Results from this pilot study identify the basic serum immune profile associated with protection against Ascaris and Trichuris and serve as the foundation for a second, more comprehensive study that will guide vaccine antigen selection against each parasite by mimicking endemic host protective responses.

The Human Hookworm Vaccine

Hookworm infection is one of the world's most common neglected tropical diseases and a leading cause of iron deficiency anemia in low- and middle-income countries. A Human Hookworm Vaccine is currently being developed by the Sabin Vaccine Institute and is in phase 1 clinical testing. The candidate vaccine is comprised of two recombinant antigens known as Na-GST-1 and Na-APR-1, each of which is an important parasite enzyme required for hookworms to successfully utilize host blood as a source of energy. The recombinant proteins are formulated on Alhydrogel^® and are being tested in combination with a synthetic Toll-like receptor 4 agonist. The aim of the vaccine is to induce anti-enzyme antibodies that will reduce both host blood loss and the number of hookworms attached to the gut. Transfer of the manufacturing technology to the Oswaldo Cruz Foundation (FIOCRUZ)/Bio-Manguinhos (a Brazilian public sector developing country vaccine manufacturer) is planned, with a clinical development plan that could lead to registration of the vaccine in Brazil. The vaccine would also need to be introduced in the poorest regions of Africa and Asia, where hookworm infection is highly endemic. Ultimately, the vaccine could become an essential tool for achieving hookworm control and elimination, a key target in the 2012 London Declaration on Neglected Tropical Diseases.