Peptide-based subunit vaccine against hookworm infection.

Mariusz Skwarczynski,Alex Loukas,Mark S Pearson,Annette M Dougall,Istvan Toth,Makan Khoshnejad,Saranya Chandrudu,David Joseph Diemert

doi:10.1371/journal.pone.0046870

Abstract

Hookworms infect more people than HIV and malaria combined, predominantly in third world countries. Treatment of infection with chemotherapy can have limited efficacy and re-infections after treatment are common. Heavy infection often leads to debilitating diseases. All these factors suggest an urgent need for development of vaccine. In an attempt to develop a vaccine targeting the major human hookworm, Necator americanus, a B-cell peptide epitope was chosen from the apical enzyme in the hemoglobin digestion cascade, the aspartic protease Na-APR-1. The A291Y alpha helical epitope is known to induce neutralizing antibodies that inhibit the enzymatic activity of Na-APR-1, thus reducing the capacity for hookworms to digest hemoglobin and obtain nutrients. A291Y was engineered such that it was flanked on both termini by a coil-promoting sequence to maintain native conformation, and subsequently incorporated into a Lipid Core Peptide (LCP) self-adjuvanting system. While A291Y alone or the chimeric epitope with or without Freund’s adjuvants induced negligible IgG responses, the LCP construct incorporating the chimeric peptide induced a strong IgG response in mice. Antibodies produced were able to bind to and completely inhibit the enzymatic activity of Na-APR-1. The results presented show that the new chimeric LCP construct can induce effective enzyme-neutralising antibodies in mice, without the help of any additional toxic adjuvants. This approach offers promise for the development of vaccines against helminth parasites of humans and their livestock and companion animals.

Highlights

Hookworm infection causes one of the world’s most debilitating neglected tropical diseases
There are numerous obstacles facing the production and safe use of a vaccine based on an active protease, so we identified an epitope from NaAPR-1, A291Y, that was capable of inducing antibodies that neutralized the catalytic activity of the recombinant enzyme [11]
We describe a self-adjuvanting approach to produce A291Y fused to GCN4 and Lipid Core Peptide (LCP), and show that antibodies generated to the construct can neutralize the enzymatic activity of the native enzyme, highlighting the utility of this approach for the development of vaccines for neglected tropical diseases of humans

Summary

Introduction

Hookworm infection causes one of the world’s most debilitating neglected tropical diseases. Heavy infection leads to irondeficiency anemia and can manifest as impaired neurological and intellectual functioning in children, reduced work capacity in adults, and severe adverse outcomes in pregnancy [2]. Those most vulnerable to the harmful effects of hookworm include children and pregnant women, who are unable to tolerate the chronic blood loss and iron deficiency anemia due to their lower iron reserves [3]. These factors have significant influence on current and future productivity and economic well being of infected populations. There is no human hookworm vaccine on the market or in advanced clinical trials

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Results

Conclusion