Hookworm burden reductions in BALB/c mice vaccinated with recombinant Ancylostoma secreted proteins (ASPs) from Ancylostoma duodenale, Ancylostoma caninum and Necator americanus

Vaccination of mice with alum-precipitated recombinant Ancylostoma secreted protein-1 from the canine hookworm Ancylostoma caninum (Ac-ASP-1) results in protection against A. caninum larval challenge. Vaccine protection is manifested by host reductions in hookworm burden compared to control mice. The goal of this study was to determine whether ASP antigens cloned and expressed from different hookworm species will cross protect against A. caninum larval challenge. Cross-species protection against A. caninum challenge infections was observed with immunizations using recombinant ASP-1 from the human hookworms Ancylostoma duodenale and Necator americanus. However, the degree of protection was proportional to the extent of amino acid sequence homology between the ASP immunogen used for vaccination and the Ac-ASP-1 produced by the challenge larval strain. Vaccine protection was noted to decrease significantly as amino acid sequence homologies diverged 10% or more. It was also determined that Ac-ASP-2, a molecule cloned from A. caninum having 55% amino acid sequence homology to the C-terminus of Ac-ASP-1, did not elicit vaccine protection. These observations were partly reflected in the titer of antibodies that recognize Ac-ASP-1. The studies reported here will help to design immunogenic peptide vaccines based on the sequence divergence of hookworm ASPs.