The complement of family M1 aminopeptidases of Haemonchus contortus--Biotechnological implications

H11-induced immunoprotection is predominantly linked to N-glycan moieties during Haemonchus contortus infection

Nematodes are one of the largest groups of animals on the planet. Many of them are major pathogens of humans, animals and plants, and cause destructive diseases and socioeconomic losses worldwide. Despite their adverse impacts on human health and agriculture, nematodes can be challenging to control, because anthelmintic treatments do not prevent re-infection, and excessive treatment has led to widespread drug resistance in nematode populations. Indeed, many nematode species of livestock animals have become resistant to almost all classes of anthelmintics used. Most efforts to develop commercial anti-nematode vaccines (native or recombinant) for use in animals and humans have not succeeded, although one effective (dead) vaccine (Barbervax) has been developed to protect animals against one of the most pathogenic parasites of livestock animals – Haemonchus contortus (the barber’s pole worm). This vaccine contains native molecules, called H11 and H-Gal-GP, derived from the intestine of this blood-feeding worm. In its native form, H11 alone consistently induces high levels (75-95%) of immunoprotection in animals against disease (haemonchosis), but recombinant forms thereof do not. Here, to test the hypothesis that post-translational modification (glycosylation) of H11 plays a crucial role in achieving such high immunoprotection, we explored the N-glycoproteome and N-glycome of H11 using the high-resolution mass spectrometry and assessed the roles of N-glycosylation in protective immunity against H. contortus. Our results showed conclusively that N-glycan moieties on H11 are the dominant immunogens, which induce high IgG serum antibody levels in immunised animals, and that anti-H11 IgG antibodies can confer specific, passive immunity in naïve animals. This work provides the first detailed account of the relevance and role of protein glycosylation in protective immunity against a parasitic nematode, with important implications for the design of vaccines against metazoan parasites.

The developmental phosphoproteome of Haemonchus contortus

Protein phosphorylation plays essential roles in many cellular processes. Despite recent progress in the genomics, transcriptomics and proteomics of socioeconomically important parasitic nematodes, there is scant phosphoproteomic data to underpin molecular biological discovery. Here, using the phosphopeptide enrichment-based LC-MS/MS and data-independent acquisition (DIA) quantitation, we characterised the first developmental phosphoproteome of the parasitic nematode Haemonchus contortus - one of the most pathogenic parasites of ruminant livestock. Totally, 1804 phosphorylated proteins with 4406 phosphorylation sites ('phosphosites') from different developmental stages/sexes were identified. Bioinformatic analyses of quantified 'phosphosites' exhibited distinctive stage- and sex-specific patterns during development, and identified a subset of phosphoproteins proposed to play crucial roles in processes such as spindle positioning, signal transduction and kinase activity. A sequence-based comparison of the phosphoproteome of H. contortus with those of two free-living nematode species (Caenorhabditis elegans and Pristionchus pacificus) suggested a limited number of common protein phosphorylation events among these species. Our findings infer active roles for protein phosphorylation in the adaptation of a parasitic nematode to a constantly changing external environment. The phosphoproteomic data set for H. contortus provides a basis to better understand phosphorylation and associated biological processes (e.g., regulation of signal transduction), and might enable the discovery of novel anthelmintic targets. SIGNIFICANCE: Here, we report the first phosphoproteome for a socioeconomically parasitic nematode (Haemonchus contortus). This phosphoproteome exhibits distinctive patterns during development, suggesting active roles of post-translational modification in the parasite's adaptation to changing environments within and outside of the host animal. This work sheds a light on the developmental phosphorylation in a parasitic nematode, and could enable the discovery of novel interventions against major pathogens.

Somatic proteome of Haemonchus contortus

Currently, there is a dearth of proteomic data to underpin fundamental investigations of parasites and parasitism at the molecular level. Here, using a high throughput LC-MS/MS-based approach, we undertook the first reported comprehensive, large-scale proteomic investigation of the barber's pole worm (Haemonchus contortus) - one of the most important parasitic nematodes of livestock animals worldwide. In total, 2487 unique H. contortus proteins representing different developmental stages/sexes (i.e. eggs, L3s and L4s, female (Af) and male (Am) adults) were identified and quantified with high confidence. Bioinformatic analyses of this proteome revealed substantial alterations in protein profiles during the life cycle, particularly in the transition from the free-living to the parasitic phase, and key groups of proteins involved specifically in feeding, digestion, metabolism, development, parasite-host interactions (including immunomodulation), structural remodelling of the body wall and adaptive processes during parasitism. This proteomic data set will facilitate future molecular, biochemical and physiological investigations of H. contortus and related nematodes, and the discovery of novel intervention targets against haemonchosis.

Transcriptomic profiling of nematode parasites surviving vaccine exposure

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Surviving Haemonchus contortus from vaccinated sheep were compared with control worms.

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There is no evidence for changes in expression of genes encoding Barbervax® antigens.

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There was increased expression of other proteases and regulators of lysosome trafficking.

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Surviving worms displayed up-regulated lipid storage and defecation abilities.

Some nematode species are economically important parasites of livestock, while others are important human pathogens causing some of the most important neglected tropical diseases. In both humans and animals, anthelmintic drug administration is the main control strategy, but the emergence of drug-resistant worms has stimulated the development of alternative control approaches. Among these, vaccination is considered to be a sustainable and cost effective strategy. Currently, Barbervax® for the ruminant strongylid Haemonchus contortus is the only registered subunit vaccine for a nematode parasite, although a vaccine for the human hookworm Necator americanus is undergoing clinical trials (HOOKVAC consortium). As both these vaccines comprise a limited number of proteins, there is potential for selection of nematodes with altered sequences or expression of the vaccine antigens. Here we compared the transcriptome of H. contortus populations from sheep vaccinated with Barbervax® with worms from control animals. Barbervax® antigens are native integral membrane proteins isolated from the brush border of the intestinal cells of the adult parasite and many of those are proteases. Our findings provide no evidence for changes in expression of genes encoding Barbervax® antigens in the surviving parasite populations. However, surviving parasites from vaccinated animals showed increased expression of other proteases and regulators of lysosome trafficking, and displayed up-regulated lipid storage and defecation abilities that may have circumvented the effect of the vaccine. Implications for other potential vaccines for human and veterinary nematodes are discussed.

Recent Research Progress in China on Haemonchus contortus

Haemonchus contortus is one of the most important parasites of ruminants with worldwide distribution that can bring huge economic losses to the breeding industry of cattle, sheep, and goats. In recent 20 years, studies on H. contortus in China mainly focused on the epidemiology, population genetics, anthelmintic resistance, structural and functional studies of important genes regulating the development of this parasite, interaction between parasite molecules and host cells and vaccine development against haemonchosis, and achieved good progress. However, there is no systematic review about the studies by Chinese researchers on H. contortus in China. The purpose of this review is to bring together the findings from the studies on H. contortus in China in order to obtain the knowledge gained from the recent studies in China and provide foundation for identifying future research directions to establish novel diagnostic methods, discover new drug targets and vaccine candidates for use in preventing and controlling H. contortus in China.