Background: The intestine of hookworms contains enzymes and proteins involved in the blood-feeding process of the
parasite and is therefore a promising source of possible vaccine antigens. One such antigen, the hemoglobin-digesting
intestinal aspartic protease known as Na-APR-1 from the human hookworm Necator americanus, is currently a lead
candidate antigen in clinical trials, as is Na-GST-1 a heme-detoxifying glutathione S-transferase.
Methods: In order to discover additional hookworm vaccine antigens, messenger RNA was obtained from the
intestine of male hookworms, Ancylostoma ceylanicum, maintained in hamsters. RNA-seq was performed using Illumina
high-throughput sequencing technology. The genes expressed in the hookworm intestine were compared with
those expressed in the whole worm and those genes overexpressed in the parasite intestine transcriptome were
further analyzed.
Results: Among the lead transcripts identified were genes encoding for proteolytic enzymes including an A. ceylanicum
APR-1, but the most common proteases were cysteine-, serine-, and metallo-proteases. Also in abundance were specific
transporters of key breakdown metabolites, including amino acids, glucose, lipids, ions and water; detoxifying and
heme-binding glutathione S-transferases; a family of cysteine-rich/antigen 5/pathogenesis-related 1 proteins (CAP)
previously found in high abundance in parasitic nematodes; C-type lectins; and heat shock proteins. These candidates
will be ranked for downstream antigen target selection based on key criteria including abundance, uniqueness in the
parasite versus the vertebrate host, as well as solubility and yield of expression.
Conclusion: The intestinal transcriptome of A. ceylanicum provides useful information for the identification of proteins
involved in the blood-feeding process, representing a first step towards a reverse vaccinology approach to a human
hookworm vaccine.