Hookworm excretory/secretory products modulate immune responses to heterologous and species-specific antigens

Hookworms dynamically respond to loss of Type 2 immune pressure

The impact of the host immune environment on parasite transcription and fitness is currently unknown. It is widely held that hookworm infections have an immunomodulatory impact on the host, but whether the converse is true remains unclear. Immunity against adult-stage hookworms is largely mediated by Type 2 immune responses driven by the transcription factor Signal Transducer and Activator of Transcription 6 (STAT6). This study investigated whether serial passage of the rodent hookworm Nippostrongylus brasiliensis in STAT6-deficient mice (STAT6 KO) caused changes in parasites over time. After adaptation to STAT6 KO hosts, N. brasiliensis increased their reproductive output, feeding capacity, energy content, and body size. Using an improved N. brasiliensis genome, we found that these physiological changes corresponded with a dramatic shift in the transcriptional landscape, including increased expression of gene pathways associated with egg production, but a decrease in genes encoding neuropeptides, proteases, SCP/TAPS proteins, and transthyretin-like proteins; the latter three categories have been repeatedly observed in hookworm excreted/secreted proteins (ESPs) implicated in immunosuppression. Although transcriptional changes started to appear in the first generation of passage in STAT6 KO hosts for both immature and mature adult stages, downregulation of the genes putatively involved in immunosuppression was only observed after multiple generations in this immunodeficient environment. When STAT6 KO-adapted N. brasiliensis were reintroduced to a naive WT host after up to 26 generations, this progressive change in host-adaptation corresponded to increased production of inflammatory cytokines by the WT host. Surprisingly, however, this single exposure of STAT6 KO-adapted N. brasiliensis to WT hosts resulted in worms that were morphologically and transcriptionally indistinguishable from WT-adapted parasites. This work uncovers remarkable plasticity in the ability of hookworms to adapt to their hosts, which may present a general feature of parasitic nematodes.

Hepatocellular carcinoma-associated antigen 59 and ADP-ribosylation factor 1 with poly (lactic-co-glycolic acid): A promising candidate as nanovaccine against haemonchosis

Haemonchus contortus (H. contortus) ADP-ribosylation factor 1 (Hc-ARF1) and Hepatocellular carcinoma-associated antigen 59 (Hc-HCA59) are recognized to largely regulate the immune responses of host cells. However, studies about the protective efficacy of the two molecules are poorly unknown. In this research, combinations of recombinant Hc-HCA59 (rHc-HCA59) and Hc-ARF1 (rHc-ARF1) proteins were amalgamated with poly (lactic-co-glycolic acid) (PLGA) nanoparticles adjuvant in order to investigate their protection potential against H. contortus in goats. The results demonstrated that the levels of IgG, IgA, IgE, and IL-4 were noticeably enhanced in the rHc-HCA59 and rHc-ARF1 (rHc-HCA59+rHc-ARF1) group before H. contortus third-stage larvae (L3) challenge. After the L3 challenge, the levels of IL-17, IL-9, and TGF-β were considerably upregulated in the rHc-HCA59+rHc-ARF1 group. In the meantime, the abomasal worm burdens and the fecal eggs were reduced by 63.2% and 69.4% respectively in the rHc-HCA59+rHc-ARF1 group. According to the studies, PLGA nanoparticles immobilized with rHc-HCA59 and rHc-ARF1 proteins conferred partial protection and were expected to be a potential candidate for developing nano vaccines to combat goat haemonchosis.

Developing Immune Profiles of Endangered Australian Sea Lion (Neophoca cinerea) Pups Within the Context of Endemic Hookworm (Uncinaria sanguinis) Infection

As a top predator, the endangered Australian sea lion (Neophoca cinerea) is a sentinel of ecosystem change, where population trends can reflect broader shifts in the marine environment. The population of this endemic pinniped was historically diminished by commercial sealing, and recovery has been slowed by fishery interactions, disease and, potentially, pollutants. Hookworm infects 100% of neonatal pups and has been identified as a contributor to population decline. Here, a multivariable approach using traditional serological and novel molecular tools such as qPCR and ddPCR was used to examine immune phenotypes of developing Australian sea lion pups infected with the endemic hookworm (Uncinaria sanguinis) from two South Australian colonies. Results show changing immunophenotypes throughout the patent period of infection represented by pro-inflammatory cytokines (IL-6), IgG and acute-phase proteins. Although cytokines may prove useful as markers of resistance, in this study, IL-6 is determined to be an early biomarker of inflammation in Australian sea lion pups, excluding the alternative hypothesis. Additionally, immunological differences between animals from high- and low-intensity hookworm seasons, as well as ivermectin-treated animals, indicate hookworm infection modulation of the host immune response, as evidenced by a lower IL-6 mRNA expression in the non-treated groups. This study of the Australian sea lion is an example of an ecoimmunological approach to disease investigation, which can be applied to evaluate the impact of environmental and anthropogenic factors on susceptibility to infectious diseases in free-ranging species

Comparison of percutaneous vs oral infection of hamsters with the hookworm Ancylostoma ceylanicum: Parasite development, pathology and primary immune response

BACKGROUND

Hundreds of millions of people in poor countries continue to suffer from disease caused by bloodfeeding hookworms. While mice and rats are not reliably permissive hosts for any human hookworm species, adult Golden Syrian hamsters are fully permissive for the human and animal pathogen Ancylostoma ceylanicum. Similar to humans, hamsters may be infected with A. ceylanicum third-stage larvae orally or percutaneously. Oral infection typically leads to consistent worm yields in hamsters but may not accurately reflect the clinical and immunological manifestations of human infection resulting from skin penetration.

METHODOLOGY/PRINCIPAL FINDINGS

In this study we compared host responses following percutaneous infection to those utilizing an established oral infection protocol. Infected hamsters exhibited a dose-dependent pathology, with 1000 percutaneous larvae (L3) causing anemia and adult worm recovery comparable to that of 50 orally administered L3. A delayed arrival and maturity of worms in the intestine was observed, as was variation in measured cellular immune responses. A long-term study found that the decline in blood hemoglobin was more gradual and did not reach levels as low, with the nadir of disease coming later in percutaneously infected hamsters. Both groups exhibited moderate growth delay, an effect that was more persistent in the percutaneously infected group. Fecal egg output also peaked later and at lower levels in the percutaneously infected animals. In contrast to orally infected hamsters, antibody titers to larval antigens continued to increase throughout the course of the experiment in the percutaneous group.

CONCLUSIONS/SIGNIFICANCE

These results demonstrate that the route of infection with A. ceylanicum impacts disease pathogenesis, as well as humoral and cellular immune responses in an experimental setting. These data further validate the utility of the Golden Syrian hamster as a model of both oral and percutaneous infection with human hookworms.

Profiles of CD4+, CD8+, and regulatory T cells and circulating cytokines in hookworm-infected children in southern Thailand

Hookworm infection is the most common human helminthic infection in the rural areas of southern Thailand. There is little information on the induced cellular immune responses in hookworm-infected children. The present study aimed to investigate the cellular immune responses, regulatory T cells (Tregs), Th1-type cytokines (interleukin (IL)-2 and interferon (IFN)-γ), a Th2-type cytokine (IL-5) and IL-10, which is one of the cytokines secreted by Tregs in hookworm-infected children. Twenty-nine schoolchildren diagnosed with hookworm infections and 28 healthy controls were enrolled in the study. CD4+ and CD8+ T cells and Tregs in whole blood were analyzed using flow cytometry. Plasma IL-2, IL-5, IL-10 and IFN-γ concentrations were quantified by enzyme-linked immunosorbent assay (ELISA). The median CD4+ T cell frequency was significantly higher in hookworm-infected children than healthy controls. Compared to healthy controls, hookworm-infected children had a significantly increased absolute number of Tregs. No differences in circulating CD8+ T cell median frequency or absolute numbers were observed among hookworm-infected children or healthy controls. Elevated IL-2 and IL-10 concentrations were found in hookworm-infected children. Moreover, the absolute number of Tregs was significantly positively correlated with the plasma IL-10 concentration (r_s = 0.406, P = 0.029). This study showed that hookworm-infected schoolchildren had significantly different immune responses than healthy controls, including an increase in the CD4+ T cell number, a significant induction of Tregs and significantly elevated circulating IL-10 levels. These alterations could be the mechanism underlying the immunomodulation that alleviates allergic diseases among hookworm-infected individuals.

Cysticercus cellulosae Regulates T-Cell Responses and Interacts With the Host Immune System by Excreting and Secreting Antigens

Cysticercus cellulosae (C. cellulosae) excretes and secretes antigens during the parasitic process to regulate the host immune response; however, resulting immune response and cytokine production in the host during infection still remains unclear. We used C. cellulosae crude antigens (CAs) as controls to explore the effect of excretory secretory antigens (ESAs) on T-cell immune responses in piglets. C. cellulosae ESAs induced imbalanced CD4⁺/CD8⁺ T-cell proportions, increased the CD4⁺Foxp3⁺ and CD8⁺Foxp3⁺ T-cell frequencies, and induced lymphocytes to produce interleukin-10, which was mainly attributed to CD4⁺ and CD4⁻CD8⁻ T cells. The ESAs also induced Th2-type immune responses. The results showed that the ability of C. cellulosae to escape the host immune attacks and establish a persistent infection may be related to host immune response regulation by the ESAs.

Modulatory functions of recombinant electron transfer flavoprotein α subunit protein from Haemonchus contortus on goat immune cells in vitro

Suppression and modulation of the host immune response to parasitic nematodes have been extensively studied. In the present study, we cloned and produced recombinant electron transfer flavoprotein α subunit (ETFα) protein from Haemonchus contortus (rHCETFα), a parasitic nematode of small ruminants, and studied the effect of this protein on modulating the immune response of goat peripheral blood mononuclear cells (PBMCs) and monocytes. Immunohistochemical tests verified that the HCETFα protein was localized mainly in the intestinal wall and on the body surface of worms. Immunoblot analysis revealed that rHCETFα was recognized by the serum of goats artificially infected with H. contortus. Immunofluorescence analysis indicated that rHCETFα bound to the surface of PBMCs. rHCETFα was co-incubated with goat PBMCs to observe the immunomodulatory effects exerted by HCETFα on proliferation, apoptosis, cytokine secretion and nitric oxide (NO) production. The results showed that rHCETFα suppressed the proliferation of goat PBMCs stimulated by concanavalin A and induced apoptosis in goat PBMCs. After rHCETFα exposure, IL-2, IL-4, IL-17A and TNF-α expression was markedly reduced, whereas secretion of TGF-β1 was significantly elevated, in goat PBMCs. Moreover, rHCETFα up-regulated NO production in a dose-dependent manner. FITC-dextran internalization assays showed that rHCETFα inhibited phagocytosis of goat monocytes. These results elucidate the interaction between parasites and hosts at the molecular level, suggest a possible immunomodulatory target and contribute to the search for innovative proteins that may be candidate targets for drugs and vaccines.

Characterization of a rhodanese homologue from Haemonchus contortus and its immune-modulatory effects on goat immune cells in vitro

BACKGROUND

Modulation of the host immune response by nematode parasites has been widely reported. Rhodaneses (thiosulfate: cyanide sulfurtransferases) are present in a wide range of organisms, such as archaea, bacteria, fungi, plants and animals. Previously, it was reported that a rhodanese homologue could be bound by goat peripheral blood mononuclear cells (PBMCs) in vivo.

METHODS

In the present study, we cloned and produced a recombinant rhodanese protein originating from Haemonchus contortus (rHCRD), a parasitic nematode of small ruminants. rHCRD was co-incubated with goat PBMCs to assess its immunomodulatory effects on proliferation, apoptosis and cytokine secretion.

RESULTS

We verified that the natural HCRD protein localized predominantly to the bowel wall and body surface of the parasite. We further demonstrated that serum produced by goats artificially infected with H. contortus successfully recognized rHCRD, which bound to goat PBMCs. rHCRD suppressed proliferation of goat PBMCs stimulated by concanavalin A but did not induce apoptosis in goat PBMCs. The production of TNF-α and IFN-γ decreased significantly, whereas secretion of IL-10 and TGF-β1 increased, in goat PBMCs after exposure to rHCRD. rHCRD also inhibited phagocytosis by goat monocytes. Moreover, rHCRD downregulated the expression of major histocompatibility complex (MHC)-II on goat monocytes in a dose-dependent manner, but did not alter MHC-I expression.

CONCLUSIONS

These results propose a possible immunomodulatory target that may help illuminate the interactions between parasites and their hosts at the molecular level and reveal innovative protein species as candidate drug and vaccine targets.

Characterization of a phosphotyrosyl phosphatase activator homologue of the parasitic nematode Haemonchus contortus and its immunomodulatory effect on goat peripheral blood mononuclear cells in vitro

Suppression and modulation of the host immune response to parasitic nematodes have been extensively studied. In the present study, we cloned and produced recombinant phosphotyrosyl phosphatase activator protein from Haemonchus contortus (rHCPTPA), a parasitic nematode of small ruminants, and studied the effect of this protein on modulating the immune response of goat peripheral blood mononuclear cells. Enzymatic assays revealed that rHCPTPA enhanced the p-nitrophenylphosphate phosphatase activity of bovine PP2A₁. Immunohistochemical tests verified that the HCPTPA protein was localised mainly in the bowel wall and on the body surface of worms. It was also shown that serum produced by goats artificially infected with H. contortus successfully recognised rHCPTPA, which conjugated with goat peripheral blood mononuclear cells. The rHCPTPA was then co-incubated with goat peripheral blood mononuclear cells to assess its immunomodulatory effects on proliferation, apoptosis, cytokine secretion, migration and nitric oxide production. Our results showed that rHCPTPA suppressed the proliferation of goat peripheral blood mononuclear cells stimulated by concanavalin A and induced apoptosis in goat peripheral blood mononuclear cells. After rHCPTPA exposure, IFN-γ and IL-2 expression was markedly reduced, whereas secretion of IL-10 and IL-4 was significantly elevated, in goat peripheral blood mononuclear cells. Moreover, rHCPTPA down-regulated nitric oxide production and migration of goat peripheral blood mononuclear cells in a dose-dependent manner. These results illuminate the interaction between parasites and hosts at the molecular level, suggest a possible immunomodulatory target and contribute to the search for innovative proteins that might be candidate targets for drugs and vaccines.

The excretory/secretory products of fifth-stage larval Angiostrongylus cantonensis induces autophagy via the Sonic hedgehog pathway in mouse brain astrocytes

Angiostrongyliasis is induced by the nematode Angiostrongylus cantonensis and leads to eosinophilic meningitis and meningoencephalitis in humans. Excretory-secretory products (ESPs) are important investigation targets for studying the relationship between hosts and nematodes. These products assist worms in penetrating the blood-brain barrier and avoiding the host immune response. Autophagy is a catabolic process that is responsible for digesting cytoplasmic organelles, proteins, and lipids and removing them through lysosomes. This process is essential to cell survival and homeostasis during nutritional deficiency, cell injury and stress. In this study, we investigated autophagy induction upon treatment with the ESPs of the fifth-stage larvae (L5) of A. cantonensis and observed the relationship between autophagy and the Shh pathway. First, the results showed that A. cantonensis infection induced blood-brain barrier dysfunction and pathological changes in the brain. Moreover, A. cantonensis L5 ESPs stimulated autophagosome formation and the expression of autophagy molecules, such as LC3B, Beclin, and p62. The data showed that upon ESPs treatment, rapamycin elevated cell viability through the activation of the autophagy mechanism in astrocytes. Finally, we found that ESPs induced the activation of the Sonic hedgehog (Shh) signaling pathway and that the expression of autophagy molecules was increased through the Shh signaling pathway. Collectively, these results suggest that A. cantonensis L5 ESPs stimulate autophagy through the Shh signaling pathway and that autophagy has a protective effect in astrocytes.

In helminthes, Excretory-secretory products (ESPs) contains a wide range of molecules, including proteins, lipids, glycans, and nucleic acids, that assist in the penetration of host defensive barriers, reduction of oxidative stress, and avoid the host immune attack. It has been known as a key factor for parasite development, including feeding, invasion and molting. Therefore, ESPs is a valuable target for the investigation of the host-parasite relationships. However, only a few researches about the function of Angiostrongyliasis cantonensis ESPs have been verified to date. Angiostrongyliasis cantonensis, a blood-feeding nematode, and it is an important causative agent of eosinophilic meningitis and meningoencephalitis in human. Recent our studies have demonstrated that the A. cantonensis ESPs can induce oxidative stress, apoptosis, and immune response. In this study, we will use a mouse astrocytes as a model to investigate the signaling mechanisms of autophagy induction by ESPs treatment. First, the Microarray, Western blotting, and Transmission electron microscopy data demonstrated that A. cantonensis ESPs can induce autophagy generation in astrocytes. Next, ESPs-induced autophagy was activated via Sonic hedgehog (Shh) signaling, and it has a protective potential for astrocytes. These finding will provide new insights into the mechanisms and effects of the A. cantonensis ESPs.

Schistosomiasis and hookworm infection in humans: Disease burden, pathobiology and anthelmintic vaccines

Helminth diseases are the ancient scourges of humans and their damages are 'silent and insidious'. Of the helminth infections, schistosomiasis and hookworm infection have a great impact. This review covers information regarding vaccine candidates against schistosomiasis and hookworms that reached at least up to the phase-1 trial and literatures regarding other vaccine candidates have been excluded. For clinical manifestations, all available literatures were included, and for epidemiology and global burden of the diseases (GBD), literatures only within 2000-2019 were included. Literatures were searched surfing various databases including PubMED, Google Scholar, and Science Direct and overall over 150 literatures were identified. Globally ~250 million people are suffering from schistosomiasis, resulting 1430 thousand DALY (disability adjusted life year) per year. On the other hand, about 1.3 billion people are infected with hookworm (HW), and according to WHO, ~878 million school-age children (SAC) are at risk. HW is estimated to cause 65,000 deaths annually, accounts for 845 thousand DALYs as well as to cause 6-35.3% loss in productivity. Despite tremendous efforts, very few anthelmintic vaccine candidates such as Na-GST-1, Na-APR-1 and Na-ASP-2 against HW, and Sm28GST/Sh28GST, Sm-p80, Sm14 and Sm-TSP-1/SmTSP-2 against schistosomiasis reached up to the clinical trials. More efforts are needed to achieve the WHO targets taken against the maladies.