Oral administration with attenuated Salmonella encoding a Trichinella cystatin-like protein elicited host immunity

Alendronate repositioning as potential anti-parasitic agent targeting Trichinella spiralis inorganic pyrophosphatase, in vitro supported molecular docking and molecular dynamics simulation study

Trichinellosis represents great public health and economic problems worldwide. Moreover, the development of parasitic resistance against conventional anthelminthic treatment led to the urgent search for new therapeutic strategies, including drug repurposing. Bisphosphonates have been used to inhibit the growth of many parasites and have also emerged as promising candidates for the treatment of cryptosporidiosis and amoebic liver abscess. Alendronate is a second-generation bisphosphonate that is widely used for the treatment and prevention of osteoporosis. Till date, there is not enough data on the effect of this drug on Trichinella spiralis and it is unknown whether the regular use of this drug in osteoporotic patients may alter the course of the infection. ALN showed a significant lethal effect on both adult worms and juveniles, with severe tegumental damage in the form of fissures in the cuticle, widening of the hypodermal gland, and flattening of the cuticular annulation, ending with the appearance of multiple vesicles and large cauliflower masses. Molecular docking outcomes unveiled the potential inhibition of ALN against T. spiralis surface proteins (i.e., Ts-SP, Ts-PPase, Ts-MAPRC2, Ts-TS, Ts-MIF, etc.), with promising results confirmed its ability to defeat T. spiralis via targeting its surface proteins. Moreover, molecular dynamics simulation, through the analysis of RMSD, RMSF, RG, SASA and cluster analysis, proved the prolonged effective inhibition of ALN on T. spiralis inorganic pyrophosphatase, as an essential surface protein required for molting and developmental process of intestinal larval stages. Thus, ALN might be a valuable drug candidate for the treatment of trichinellosis and warrant further investigation in animal models of disease.

Quantitative label-free proteomic analysis of excretory-secretory proteins in different developmental stages of Trichinella spiralis

Trichinella spiralis (T. spiralis) is a zoonotic parasitic nematode with a unique life cycle, as all developmental stages are contained within a single host. Excretory-secretory (ES) proteins are the main targets of the interactions between T. spiralis and the host at different stages of development and are essential for parasite survival. However, the ES protein profiles of T. spiralis at different developmental stages have not been characterized. The proteomes of ES proteins from different developmental stages, namely, muscle larvae (ML), intestinal infective larvae (IIL), preadult (PA) 6 h, PA 30 h, adult (Ad) 3 days post-infection (dpi) and Ad 6 dpi, were characterized via label-free mass spectrometry analysis in combination with bioinformatics. A total of 1217 proteins were identified from 9341 unique peptides in all developmental stages, 590 of which were quantified and differentially expressed. GO classification and KEGG pathway analysis revealed that these proteins were important for the growth of the larvae and involved in energy metabolism. Moreover, the heat shock cognate 71 kDa protein was the centre of protein interactions at different developmental stages. The results of this study provide comprehensive proteomic data on ES proteins and reveal that these ES proteins were differentially expressed at different developmental stages. Differential proteins are associated with parasite survival and the host immune response and may be potential early diagnostic antigen or antiparasitic vaccine candidates.

Immunomodulatory and biological properties of helminth-derived small molecules: Potential applications in diagnostics and therapeutics

Parasitic helminths secrete and excrete a vast array of molecules known to help skew or suppress the host's immune response, thereby establishing a niche for sustained parasite maintenance. Indeed, the immunomodulatory potency of helminths is attributed mainly to excretory/secretory products (ESPs). The ESPs of helminths and the identified small molecules (SM) are reported to have diverse biological and pharmacological properties. The available literature reports only limited metabolites, and the identity of many metabolites remains unknown due to limitations in the identification protocols and helminth-specific compound libraries. Many metabolites are known to be involved in host-parasite interactions and pathogenicity. For example, fatty acids (e.g., stearic acid) detected in the infective stages of helminths are known to have a role in host interaction through facilitating successful penetration and migration inside the host. Moreover, excreted/secreted SM detected in helminth species are found to possess various biological properties, including anti-inflammatory activities, suggesting their potential in developing immunomodulatory drugs. For example, helminths-derived somatic tissue extracts and whole crude ESPs showed anti-inflammatory properties by inhibiting the secretion of proinflammatory cytokines from human peripheral blood mononuclear cells and suppressing the pathology in chemically-induced experimental mice model of colitis. Unlike bigger molecules like proteins, SM are ideal candidates for drug development since they are small structures, malleable, and lack immunogenicity. Future studies should strive toward identifying unknown SM and isolating the under-explored niche of helminth metabolites using the latest metabolomics technologies and associated software, which hold potential keys for finding new diagnostics and novel therapeutics.

Vaccines as a Strategy to Control Trichinellosis

Trichinellosis caused by Trichinella spiralis is a worldwide food-borne parasitic zoonosis. Several approaches have been performed to control T. spiralis infection, including veterinary vaccines, which contribute to improving animal health and increasing public health by preventing the transmission of trichinellosis from animals to humans. In the past several decades, many vaccine studies have been performed in effort to control T. spiralis infection by reducing the muscle larvae and adult worms burden. Various candidate antigens, selected from excretory-secretory (ES) products and different functional proteins involved in the process of establishing infection have been investigated in rodent or swine models to explore their protective effect against T. spiralis infection. Moreover, different types of vaccines have been developed to improve the protective effect against T. spiralis infection in rodent or swine models, such as live attenuated vaccines, natural antigen vaccines, recombinant protein vaccines, DNA vaccines, and synthesized epitope vaccines. However, few studies of T. spiralis vaccines have been performed in pigs, and future research should focus on exploring the protective effect of different types of vaccines in swine models. Here, we present an overview of the strategies for the development of effective T. spiralis vaccines and summarize the factors of influencing the effectiveness of vaccines. We also discuss several propositions in improving the effectiveness of vaccines and may provide a route map for future T. spiralis vaccines development.

Oral vaccination with attenuated Salmonella encoding the Trichinella spiralis 43-kDa protein elicits protective immunity in BALB/c mice

A vaccine against Trichinella spiralis infection is urgently needed to interrupt its transmission from domestic animals to humans. However, no vaccine against T. spiralis is currently available. Our previous study demonstrated that the use of the 43-kDa glycoprotein present in excretory-secretory (ES) proteins of muscle larvae (ML) as an intramuscular DNA vaccine led to a 52.1% protection rate against T. spiralis infection. Attenuated Salmonella strains have the advantage of eliciting mucosal immunity, which is important for controlling T. spiralis infections at the intestinal stage and can be provided as vaccines via oral or intranasal routes. Therefore, in this study, complete 43-kDa glycoprotein (Ts43) sequences of T. spiralis were cloned into the vector pYA3681, and the recombinant plasmid pYA3681-Ts43 was transformed into the attenuated Salmonella typhimurium strain χ11802. The results showed that oral vaccination of mice with attenuated Salmonella carrying the recombinant plasmid pYA3681-Ts43 induced an evident elevation of the local intestinal mucosal sIgA and serum IgG antibody responses. The flow cytometry results showed that the percentages of CD4⁺ T cells and secreted IFN-γ, IL-4, and IL-17A in CD4⁺ T cells were significantly increased in the spleen and mesenteric lymph node (MLN) lymphocytes of the vaccinated groups. In addition, increased levels of the IFN-γ, IL-4, and IL-17A cytokines were also observed in the serum of the immunized groups. The above immune response results in the immunized groups demonstrated that protective immunity was elicited in this study. Finally, vaccinated mice demonstrated a significant 45.9% reduction in ML burden after infection with T. spiralis. This study demonstrated that oral vaccination with Ts43 delivered by attenuated Salmonella elicited local and systemic concurrent Th1/Th2/Th17 immune responses and provided partial protection against T. spiralis infection in BALB/c mice. This is a prospective strategy for the prevention and control of trichinellosis.

Immunomics-Guided Antigen Discovery for Praziquantel-Induced Vaccination in Urogenital Human Schistosomiasis

Despite the enormous morbidity attributed to schistosomiasis, there is still no vaccine to combat the disease for the hundreds of millions of infected people. The anthelmintic drug, praziquantel, is the mainstay treatment option, although its molecular mechanism of action remains poorly defined. Praziquantel treatment damages the outermost surface of the parasite, the tegument, liberating surface antigens from dying worms that invoke a robust immune response which in some subjects results in immunologic resistance to reinfection. Herein we term this phenomenon Drug-Induced Vaccination (DIV). To identify the antigenic targets of DIV antibodies in urogenital schistosomiasis, we constructed a recombinant proteome array consisting of approximately 1,000 proteins informed by various secretome datasets including validated proteomes and bioinformatic predictions. Arrays were screened with sera from human subjects treated with praziquantel and shown 18 months later to be either reinfected (chronically infected subjects, CI) or resistant to reinfection (DIV). IgG responses to numerous antigens were significantly elevated in DIV compared to CI subjects, and indeed IgG responses to some antigens were completely undetectable in CI subjects but robustly recognized by DIV subjects. One antigen in particular, a cystatin cysteine protease inhibitor stood out as a unique target of DIV IgG, so recombinant cystatin was produced, and its vaccine efficacy assessed in a heterologous Schistosoma mansoni mouse challenge model. While there was no significant impact of vaccination with adjuvanted cystatin on adult worm numbers, highly significant reductions in liver egg burdens (45-55%, P<0.0001) and intestinal egg burdens (50-54%, P<0.0003) were achieved in mice vaccinated with cystatin in two independent trials. This study has revealed numerous antigens that are targets of DIV antibodies in urogenital schistosomiasis and offer promise as subunit vaccine targets for a drug-linked vaccination approach to controlling schistosomiasis.

Trichinella spiralis: inflammation modulator

The hygiene hypothesis posits that the decreased incidence of parasitic infection in developed countries may underlie an increased prevalence of allergic and autoimmune diseases in these countries. As unique inflammation modulator of intracellular parasitism, Trichinella spiralis, or its excretory-secretory (ES) product, shows improved responses to allergies, autoimmune diseases, inflammatory bowel disease, type 1 diabetes, rheumatic arthritis and autoimmune encephalomyelitis by exerting immunomodulatory effects on both innate and adaptive immune cells in animal models. Research has shown that T. spiralis differs from other helminths in manipulation of the host immune response not only by well-known characteristics of its life cycle, but also by its inflammation modulation pathway. How the parasite achieves inflammation modulation has not been fully elucidated yet. This review will generalize the mechanism and focuses on ES immunomodulatory molecules of T. spiralis that may be important for developing new therapeutics for inflammatory disorders.

Cystatin C regulates major histocompatibility complex-II-peptide presentation and extracellular signal-regulated kinase-dependent polarizing cytokine production by bone marrow-derived dendritic cells

Cystatin C is a ubiquitously expressed cysteine protease inhibitor that protects cells from either improper hydrolysis by endogenous proteases or pathogen growth/virulence by exogenous proteases. Although commonly used as a serum biomarker for evaluating renal function, cystatin C is associated with many immunological disorders under various pathophysiological conditions. How cystatin C affects immune cells, especially dendritic cells (DCs), however, is far from clear. In this study, we found that pharmacological treatment with or genetic overexpression of cystatin C in bone marrow-derived DCs (BMDCs) reduced their capacity to stimulate CD4⁺ T-cell proliferation, despite increased antigen uptake. This reduced capacity corresponded with reduced major histocompatibility complex-II presentation owing to diminished levels of the chaperon H2-DM in BMDCs. Instead of promoting proliferation, cystatin C promoted skewing of T cells toward proinflammatory T-helper (Th)1/Th17 differentiation. This was mediated by augmented extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase phosphorylation in BMDCs, leading to secretion of polarizing cytokines, which in turn led to the Th deviation. Collectively, our study explained the cellular and molecular basis of how this protease inhibitor can regulate immune responses, namely by affecting BMDCs and their cytokine pathway. Our results might open up an avenue for the development of therapeutic agents for the treatment of cystatin C-related immunological diseases.

Oral vaccination with Trichinella spiralis DNase II DNA vaccine delivered by attenuated Salmonella induces a protective immunity in BALB/c mice

Trichinellosis is one of the most serious foodborne parasitic zoonosis with worldwide distribution, and it is necessary to develop a vaccine to interrupt transmission from animals to humans. Trichinella spiralis adult-specific DNase II-1 (TsDNase II) were identified by immunoproteomics in surface or excretory/secretory proteins of adult worms (AW) and intestinal infective larvae (IIL). The aim of this study was to investigate the systemic, mucosal responses and immune protection elicited by oral vaccination with TsDNase II DNA vaccine delivered by attenuated Salmonella typhimurium strain⊿cyaSL1344. Oral vaccination with TsDNase II DNA vaccine triggered an obvious mucosal sIgA response and a systemic IgG response in mice, and IgG1 was predominant. Th1 (IFN-γ) and Th2 (IL-4, 10) cytokines were distinctly increased in the spleen and mesenteric lymph node (MLN) cells of vaccinated mice. An indirect immunofluorescent test revealed that native TsDNase II is present at the cuticle of this nematode after the 2^nd molting, further confirming that TsDNase II is adult-specific and expressed at AW and pre-adult stages. Oral immunization of mice with TsDNase II exhibited a 53.85% reduction in AW and a 59.26% reduction in ML after larval challenge. The in vitro NBL production of adult females from TsDNase II-vaccinated mice was also reduced in comparison with pcDNA3.1 or the PBS control group (P < 0.01). Our results show that oral immunization of mice with TsDNase II produced an intestinal and systematic concurrent Th1/Th2 immune response, and a significant immune protection against challenge.

Protective immunity against Trichinella spiralis in mice elicited by oral vaccination with attenuated Salmonella-delivered TsSP1.2 DNA

Trichinellosis is a worldwide important food-borne zoonosis caused mainly by ingesting raw or undercooked pork infected with Trichinella spiralis larvae. The development of vaccine is needed for preventing swine from Trichinella infection to ensure pork safety. Previous studies showed that T. spiralis serine protease 1.2 (TsSP1.2) is a vaccine candidate against Trichinella infection. In this study, the complete TsSP1.2 cDNA sequences were cloned into pcDNA3.1, and the rTsSP1.2 DNA was transformed into attenuated Salmonella typhimurium strain ΔcyaSL1344. Oral vaccination of mice with Salmonella-delivered rTsSP1.2 DNA vaccine induced an obvious intestinal mucosal IgA response and a systemic Th1/Th2 immune response; the vaccinated mice showed a 33.45% reduction of intestinal adult worms and 71.84% reduction of muscle larvae after T. spiralis larval challenge. The protection might be due to the rTsSP1.2-induced production of specific anti-TsSP1.2 sIgA, IgG, IgG1/IgG2a, and secretion of IFN-γ, IL-4 and IL-10, which protected intestinal mucosa from the parasite invasion, inhibited worm development and reduced female fecundity. The results indicate that the attenuated Salmonella-delivered rTsSP1.2 DNA vaccine offers a prospective strategy for the prevention and control of animal Trichinella infection.

Vaccines against Trichinella spiralis: Progress, challenges and future prospects

Trichinella spiralis, the causative agent of trichinellosis, is able to infect a wide range of carnivores and omnivores including human beings. In the past 30 years, a mass of vaccination efforts has been performed to control T. spiralis infection with the purpose of reduction in worm fecundity or decrease in muscle larval and adult burdens. Here, we summarize the development of veterinary vaccines against T. spiralis infection. During recent years, increasing numbers of new vaccine candidates have been developed on the protective immunity against T. spiralis infection in murine model. The vaccine candidates were not only selected from excretory-secretory (ES) antigens, but also from the recombinant functional proteins, such as proteases and some other antigens participated in T. spiralis intracellular processes. However, immunization with a single antigen generally revealed lower protective effects against T. spiralis infection in mice compared to that with the inactivated whole worms or crude extraction and ES productions. Future study of T. spiralis vaccines should focus on evaluation of the protective efficacy of antigens and/or ligands delivered by nanoparticles that could elicit Th2-type immune response on experimental pigs.

Current Research of Trichinellosis in China

Trichinellosis, caused by Trichinella, is an emerging or re-emerging zoonotic parasitic disease, which is distributed worldwide with major socio-economic importance in some developing countries. In particular, it has been calculated that more than 40 million people are at risk of Trichinella infection in China. This review summarizes the current information on the epidemiology, laboratory diagnosis and vaccines of trichinellosis in China. Moreover, study of the treatment potential of using Trichinella for immune-related diseases and cancer, as well as the transcription and post-transcription modification of Trichinella were also collected, providing viewpoints for future investigations. Current advances in research will help us to develop new strategies for the prevention and control of trichinellosis and may potentially yield biological agents for treating other diseases.

Proteomic analysis of Trichinella spiralis adult worm excretory-secretory proteins recognized by early infection sera

At the intestinal stage of a Trichinella spiralis (T. spiralis) infection, the excretory-secretory (ES) antigens produced by adult worms (AWs) result in an early exposure to the host's immune system and elicit the production of specific antibodies; the AW ES proteins might provide early diagnostic markers of trichinellosis. The aim of this study was to identify early serodiagnostic markers from T. spiralis AW ES antigens. T. spiralis AWs were collected at 72h post infection, and their ES antigens were analysed by SDS-PAGE and Western blot. Then, the immunoreactive bands were subjected to shotgun LC-MS/MS and bioinformatics analyses. Our results showed that only one protein band (33kDa) was recognized by the sera of mice infected with T. spiralis at 8 days after infection. The shotgun LC-MS/MS analysis identified 23 proteins that were then clustered into 10 types; these proteins had molecular weights of 28.13-71.62kDa and pI 5.05-9.20. Certain enzymes (e.g., serine protease, adult-specific deoxyribonuclease [DNase] II, peptidase S1A subfamily, and multi cystatin-like domain protein) were found to be highly represented. The functions of the 10 proteins were further analysed: of the 6 annotated proteins, 3 had serine hydrolase activity and 2 had DNase II activity. These results provide a valuable basis for identifying early diagnostic antigens and vaccine candidates for trichinellosis.

Evaluation of protective efficacy induced by virus-like particles containing a Trichinella spiralis excretory-secretory (ES) protein in mice

BACKGROUND

The frequent outbreaks of human trichinellosis globally underscore the need to develop effective vaccine. We hypothesized that a novel vaccine could improve vaccine efficacy against Trichinella spiralis.

METHODS

In this study, we developed virus-like particles (VLPs) containing the 53 KDa excretory/secretory (ES) protein of T. spiralis and the influenza matrix protein 1 (M1) as a core protein, and investigated the protective efficacy of the VLPs alone or with cholera toxin (CT) in a mouse model.

RESULTS

Intramuscular immunization induced T. spiralis-specific IgG, IgG1 and IgG2a antibody responses before and after challenge infections in the sera. These antibody responses were significantly enhanced in mice immunized with adjuvanted VLPs. Upon challenge infection, vaccinated mice showed significantly reduced worm burden in the diaphragm. Protective immune responses and efficacy of protection were significantly improved by immunization with VLPs together with CT adjuvant.

CONCLUSIONS

Our results are informative for a better understanding of the protective immunity induced by T. spiralis VLPs, and will provide insight into designing safe and effective vaccines.

Salmonella Typhimurium strain expressing OprF-OprI protects mice against fatal infection by Pseudomonas aeruginosa

Pseudomonas aeruginosa poses a major threat to human health and to the mink industry. Thus, development of vaccines that elicit robust humoral and cellular immunity against P. aeruginosa is greatly needed. In this study, a recombinant attenuated Salmonella vaccine (RASV) that expresses the outer membrane proteins fusion OprF190-342 -OprI21-83 (F1I2) from P. aeruginosa was constructed and the potency of this vaccine candidate assessed by measuring F1I2-specific humoral immune responses upon vaccination through s.c. or oral routes. S.C. administration achieved higher serum IgG titers and IgA titers in the intestine and induced stronger F1I2-specific IgG and IgA titers in lung homogenate than did oral administration, which resulted in low IgG titers and no local IgA production. High titers of IFN-γ, IL-4, and T-lymphocyte subsets induced a mixed Th1/Th2 response in mice immunized s.c., indicating elicitation of cellular immunity. Importantly, when immunized mice were challenged with P. aeruginosa by the intranasal route 30 days after the initial immunization, s.c. vaccination achieved 77.78% protection, in contrast to 41.18% via oral administration and 66.67% via Escherichia coli-expressed F1I2 (His-F1I2) vaccination. These results indicate that s.c. vaccination provides a better protective response against P. aeruginosa infection than do oral administration and the His-F1I2 vaccine.

Comparative proteomic analysis of surface proteins of Trichinella spiralis muscle larvae and intestinal infective larvae

The critical step for Trichinella spiralis infection is that muscle larvae (ML) are activated to intestinal infective larvae (IIL) and invade intestinal epithelium to further develop. The IIL is its first invasive stage, surface proteins are directly exposed to host environment and are crucial for larval invasion and development. In this study, shotgun LC-MS/MS was used to analyze surface protein profiles of ML and IIL. Totally, 41 proteins common to both larvae, and 85 ML biased and 113 IIL biased proteins. Some proteins (e.g., putative scavenger receptor cysteine-rich domain protein and putative onchocystatin) were involved in host-parasite interactions. Gene ontology analysis revealed that proteins involved in generation of precursor metabolites and energy; and nucleobase, nucleoside, nucleotide and nucleic acid metabolic process were enriched in IIL at level 4. Some IIL biased proteins might play important role in larval invasion and development. qPCR results confirmed the high expression of some genes in IIL. Our study provides new insights into larval invasion, host-Trichinella interaction and for screening vaccine candidate antigens.

Oral vaccination of mice with Trichinella spiralis nudix hydrolase DNA vaccine delivered by attenuated Salmonella elicited protective immunity

We have previously reported that Trichinella spiralis Nudix hydrolase (TsNd) bound to intestinal epithelial cells (IECs), and the vaccination of mice with recombinant TsNd protein (rTsNd) produced a partial protective immunity against challenge infection in mice. In this study, the full-length cDNA sequence of TsNd gene was cloned into the eukaryotic expression plasmid pcDNA3.1, and the recombinant TsNd DNA was transformed into attenuated Salmonella typhimurium strain ⊿cyaSL1344. Oral immunization of mice with TsNd/S. typhimurium elicited a significant local mucosal IgA response and a systemic Th1/Th2 immune response. Cytokine profiling also showed a significant increase in the Th1 (IFN-γ, IL-2) and Th2 (IL-4, 10) responses in splenocytes of immunized mice upon stimulation with the rTsNd. The oral immunization of mice with TsNd/S. typhimurium displayed a statistically significant 73.32% reduction in adult worm burden and a 49.5% reduction in muscle larvae after challenge with T. spiralis muscle larvae, compared with PBS control group. Our results demonstrated that TsNd DNA delivered by attenuated live S. typhimurium elicited a local IgA response and a mixed Th1/Th2 immune response, and produced a partial protection against T. spiralis infection in mice.

Protective immunity against Trichinella spiralis infection induced by TsNd vaccine in mice

Background

We have previously reported that Trichinella spiralis Nudix hydrolase (TsNd) bound to intestinal epithelial cells (IECs), and vaccination of mice with recombinant TsNd protein (rTsNd) produced a partial protective immunity. The aim of this study was to investigate the immune protection induced by TsNd DNA vaccine.

Methods

The full-length cDNA sequence of TsNd gene was cloned into pcDNA3.1 and used to immunize BALB/c mice by intramuscular injection. Transcription and expression of TsNd were detected by RT-PCR and IFT. The levels of specific IgA, IgG, IgG1 and IgG2a, and cytokines were assayed by ELISA at weeks 0, 6 and 8 post-immunization. The immune protection of TsNd DNA vaccine against challenge infection was investigated.

Results

Immunization of mice with TsNd DNA elicited a systemic Th1/Th2 immune response and a local mucosal IgA response. The in vitro transcription and expression of TsNd gene was observed at all developmental stages of T. spiralis (ML, IIL, AW and NBL). Anti-rTsNd IgG levels were increased after immunization and levels of IgG1 were obviously higher than that of IgG2a. Intestinal specific IgA levels of immunized mice were significantly higher than those of vector and PBS control mice. Cytokine profiling also showed a significant increase in Th1 (IFN-γ, IL-2) and Th2 (IL-4, 10) responses in splenocytes of immunized mice on stimulation with rTsNd. Vaccination of mice with pcDNA3.1-TsNd displayed a 40.44% reduction in adult worms and a 53.9% reduction in larval burden.

Conclusions

TsNd DNA induced a mixed Th1/Th2 immune response and partial protection against T. spiralis infection in mice.

Induction of protection in murine experimental models againstTrichinella spiralis: an up-to-date review

The parasitic nematodeTrichinella spiralis, an aetiological agent of the disease known as trichinellosis, infects wild and domestic animals through contaminated pig meat, which is the major source forTrichinellatransmission. Prevention of this disease by interrupting parasite transmission includes vaccine development for livestock; however, major challenges to this strategy are the complexity of theT. spiralislife cycle, diversity of stage-specific antigens, immune-evasion strategies and the modulatory effect of host responses. Different approaches have been taken to induce protective immune responses byT. spiralisimmunogens. These include the use of whole extracts or excretory–secretory antigens, as well as recombinant proteins or synthesized epitopes, using murine experimental models for trichinellosis. Here these schemes are reviewed and discussed, and new proposals envisioned to block the zoonotic transmission of this parasite.

Global burden, distribution, and interventions for infectious diseases of poverty

Infectious diseases of poverty (IDoP) disproportionately affect the poorest population in the world and contribute to a cycle of poverty as a result of decreased productivity ensuing from long-term illness, disability, and social stigma. In 2010, the global deaths from HIV/AIDS have increased to 1.5 million and malaria mortality rose to 1.17 million. Mortality from neglected tropical diseases rose to 152,000, while tuberculosis killed 1.2 million people that same year. Substantial regional variations exist in the distribution of these diseases as they are primarily concentrated in rural areas of Sub-Saharan Africa, Asia, and Latin America, with geographic overlap and high levels of co-infection. Evidence-based interventions exist to prevent and control these diseases, however, the coverage still remains low with an emerging challenge of antimicrobial resistance. Therefore, community-based delivery platforms are increasingly being advocated to ensure sustainability and combat co-infections. Because of the high morbidity and mortality burden of these diseases, especially in resource-poor settings, it is imperative to conduct a systematic review to identify strategies to prevent and control these diseases. Therefore, we attempted to evaluate the effectiveness of one of these strategies, that is community-based delivery for the prevention and treatment of IDoP. In this paper, we describe the burden, epidemiology, and potential interventions for IDoP. In subsequent papers of this series, we describe the analytical framework and the methodology used to guide the systematic reviews, and report the findings and interpretations of our analyses of the impact of community-based strategies on individual IDoPs.