Troponin 1 of human filarial parasite Brugia malayi: cDNA cloning, expression, purification, and its immunoprophylactic potential

In-silico development of multi-epitope subunit vaccine against lymphatic filariasis

The World Health Organization in 2022 reported that more than 863 million people in 50 countries are at risk of developing lymphatic filariasis (LF), a disease caused by parasitic infection. Immune responses to parasites suggest that the development of a prophylactic vaccine against LF is possible. Using a reverse vaccinology approach, the current study identified Trehalose-6-phosphatase (TPP) as a potential vaccine candidate among 15 reported vaccine antigens for B. malayi. High-ranking B and T-cell epitopes in the Trehalose-6-phosphatase (TPP) were shortlisted using online servers for subsequent analysis. We selected these peptides to construct a vaccine model using I-TASSER and GalaxyRefine server. The vaccine construct showed favorable physicochemical properties, high antigenicity, no allergenicity, no toxicity, and high stability. Structural validation using the Ramachandran plot showed that 98% of the residues were in favorable or mostly allowed regions. Molecular docking and simulation showed a strong binding affinity and stability of the subunit vaccine with toll-like receptor 4 (TLR4). Furthermore, the subunit vaccine showed a strong IgG/IgM response, with the disappearance of the antigen. We propose that our vaccine construct should be further evaluated using cellular and animal models to develop a vaccine that is safe and effective against LF.Communicated by Ramaswamy H. Sarma.

Immune Response Profiling of Cocktails of Brugia malayi Vaccine Candidates DIM-1, Calponin and Troponin 1 in BALB/c Mice

PURPOSE

In search of a vaccine for the control of human lymphatic filariasis (LF) caused by Wuchereria bancrofti, Brugia malayi and B. timori, we identified three parasite-specific potential candidates: the disorganized muscle protein-1 (D), calponin (C) and troponin 1 (T) in B. malayi adult worm. In the present study, we investigated the immune response profile of the cocktails of the recombinant D, T and C proteins.

METHODS

Groups of BALB/c mice were immunized with individual rproteins or their cocktails DT, TC, DC and DTC, and the immunogen-specific IgG and its subclasses and IgE were determined. Cells from the immunized animals were challenged in vitro with the respective rproteins and cocktails and the release of nitric oxide (NO) from macrophages and Th1 and Th2 cytokines from splenocytes were determined.

RESULTS

Among the immunized groups, DTC elicited comparatively a stronger response which included augmented release of NO, Th1 (IL-1β, IL-2, IFN-γ and TNF-α) and Th2 (IL-4, IL-6, IL-10 and TGF-β) cytokines, and increased levels of immunogen-specific IgG, IgG1 and IgG2b and low levels of immunogen-specific IgG2a and IgE and the Th2 cytokine IL-13.

CONCLUSION

Immune responses that play important role in host protection were elicited strongly by DTC cocktail compared to the individual rproteins or DT, TC and DC cocktails. The findings provide a sound rationale for further studies on DTC cocktail as a vaccine candidate for the control of LF.

Evaluation of immunomodulatory potential of recombinant histidyl-tRNA synthetase (rLdHisRS) protein of Leishmania donovani as a vaccine candidate against visceral leishmaniasis

Visceral leishmaniasis is neglected tropical protozoan disease caused by Leishmania donovani and are associated with high fatality rate in developing countries since prophylactic vaccines are not available. In the present study, we evaluated the immunomodulatory potential of L. donovani histidyl-tRNA synthetase (LdHisRS) and predicted the epitopes using immunoinformatic tools. Histidyl-tRNA synthetase (HisRS) is a class IIa aminoacyl t-RNA synthetase enzyme (aaRS) required for histidine incorporation into proteins during protein synthesis. The recombinant LdHisRS protein (rLdHisRS) was expressed in E coli BL-21cells, and its immunomodulatory role was assessed in J774A.1 murine macrophage and in BALB/c mice, respectively. LdHisRS specifically stimulated and triggered enhance cell proliferation, nitric oxide release and IFN-γ (70%; P < 0.001), and IL-12 (55.37%; P < 0.05) cytokine release in vitro, whereas BALB/c mice immunized with rLdHisRS show higher NO release (80.95%; P<0.001), higher levels of Th1 cytokines IFN-γ (14%; P < 0.05), TNF-α (34.93%; P < 0.001), and IL-12 (28.49%; P < 0.001) and robust IgG (p<0.001) and IgG2a (p<0.001) production. We also identified 20 Helper T-lymphocytes (HTLs), 30 cytotoxic T lymphocytes (CTLs), and 18 B-cell epitopes from HisRS protein of L. donovani. All these epitopes can be further used to make a multiepitope vaccine against L. donovani.

Multi-stage transcriptome profiling of the neglected food-borne echinostome Artyfechinostomum sufrartyfex reveal potential diagnostic and drug targets

Lack of effective surveillance and control methods for neglected helminth diseases particularly in context of rural areas in India is a serious concern in terms of public health. With regard to the emerging food-borne echinostomid Artyfechinostomum sufrartyfex infection in the country, the current study is an in silico attempt to screen for plausible diagnostic and drug targets against the trematode. Transcriptome of adult, encysted and excysted metacercaria stages of the parasite was generated using Illumina sequencing platform. A de-novo assembly strategy utilizing transcriptome data generated from the three lifecycle stages was followed to generate the representative transcripts. Longest open reading frames identified for the transcripts were further conceptually translated into their respective protein sequences. Detailed analysis of this dataset through various bioinformatics pipelines and tools eventually identified 14 credible diagnostic and 10 drug targets along with their FDA-approved and ZINC molecules. Some of the important diagnostic candidates include thioredoxin peroxidase, haemoglobinase, cathepsin L, cathepsin L-like and B-like cysteine proteases. Among the drug targets, uncharacterized sodium dependent transporter and bifunctional protein Aas were identified as top targets exhibiting significant interaction with Rifamycin and ZINC02820058 molecule, respectively. Further, B-cell epitope analysis of the diagnostic targets revealed unique epitopes for 10 of them thus indicating their potential role in specific diagnosis of the parasite. The diagnostic candidates along with a number of lesser known drug targets and their ligand molecules identified in this study provides a reasonable basis for evaluation and development of future intervention strategies against A. sufrartyfex.

Immunoreactivity of Brugia malayi Calreticulin and Its Domains with Sera of Different Categories of Bancroftian Filarial Patients

PURPOSE

We identified calreticulin in human filaria Brugia malayi (BmCRT) that shares 97% homology with Wuchereria bancrofti calreticulin (WbCRT), but only 56% with human calreticulin. We found that BmCRT binds C1q and prevents complement-mediated parasite death; immunization with BmCRT leads to parasite death in a rodent model of the infection. BmCRT could, therefore, be a potential vaccine candidate. In the present study, we determined the levels of BmCRT-reactive IgG and its isotype in bancroftian filarial subjects.

METHODS

Recombinant BmCRT (rBmCRT) was prepared, and the sera of endemic normal subjects (EN), microfilaraemics (Mf+) and chronic amicrofilaraemics (ChMf-) from a bancroftian filaria-endemic area and normal subjects from filaria-non-endemic area (NEN) were probed for IgG and its isotypes reacting with rBmCRT and its domains rN, rP and rC.

RESULTS

rBmCRT and its rN domain-reactive IgG levels were high in EN and Mf+ groups; rC domain and rP domain showed moderate and very little reactivity, respectively. NEN sera were non-reactive. Moderate levels of rBmCRT-reactive IgG1, IgG3 and IgG4 in EN and Mf+ groups and low levels of IgG2 in Mf+ were found; IgG1 and IgG3 reactivity was found for rBmCRT and its rN domain only, while IgG4 reactivity was moderate for rN domain and low for rP and rC domains. While IgG reactivity was seen in all the endemic subjects, IgG isotype reactivity was found mostly in EN and Mf+ subjects.

CONCLUSIONS

Moderate levels of rBmCRT (and its rN domain)-reactive IgG and its isotypes are present in bancroftian subjects. Preponderance of IgG1 and IgG3 isotypes which bind and activate complement has relevance to vaccine potential of BmCRT.

Spatial transcriptomics reveals antiparasitic targets associated with essential behaviors in the human parasite Brugia malayi

Lymphatic filariasis (LF) is a chronic debilitating neglected tropical disease (NTD) caused by mosquito-transmitted nematodes that afflicts over 60 million people. Control of LF relies on routine mass drug administration with antiparasitics that clear circulating larval parasites but are ineffective against adults. The development of effective adulticides is hampered by a poor understanding of the processes and tissues driving parasite survival in the host. The adult filariae head region contains essential tissues that control parasite feeding, sensory, secretory, and reproductive behaviors, which express promising molecular substrates for the development of antifilarial drugs, vaccines, and diagnostics. We have adapted spatial transcriptomic approaches to map gene expression patterns across these prioritized but historically intractable head tissues. Spatial and tissue-resolved data reveal distinct biases in the origins of known drug targets and secreted antigens. These data were used to identify potential new drug and vaccine targets, including putative hidden antigens expressed in the alimentary canal, and to spatially associate receptor subunits belonging to druggable families. Spatial transcriptomic approaches provide a powerful resource to aid gene function inference and seed antiparasitic discovery pipelines across helminths of relevance to human and animal health.

Lymphatic filariasis and visceral leishmaniasis coinfection: A review on their epidemiology, therapeutic, and immune responses

Coinfection is less commonly observed in individuals around the world, yet it is more common than the single infection. Around 800 million people worldwide are infected with helminths as a result of various diseases. Lymphatic filariasis (LF) and visceral leishmaniasis (VL) are chronic, deadly, crippling, and debilitating neglected tropical diseases (NTDs) that are endemic in tropical and subtropical regions of the world. Due to poor hygienic conditions, poverty, and genetic predisposition, those living in endemic areas are more likely to develop both leishmaniasis and filariasis. One of the key challenges in the management of LF/VL coinfection is the development of an effective therapeutic strategy that not only treats the first episode of VL but also prevents LF. However, there is a scarcity of knowledge and data on the relationship between LF and VL coinfection. While reviewing it was apparent that only a few studies relevant to LF/VL coinfections have been reported from southeastern Spain, Sudan, and the Indian subcontinents, highlighting the need for greater research in the most affected areas. We also looked at LF and VL as a single disease and also as a coinfection. Some features of the immune response evolved in mammalian hosts against LF and VL alone or against coinfection are also discussed, including epidemiology, therapeutic regimens, and vaccines. In addition to being potentially useful in clinical research, our findings imply the need for improved diagnostic methodology and therapeutics, which could accelerate the deployment of more specific and effective diagnosis for treatments to lessen the impact of VL/LF coinfections in the population.

Lymphatic filariasis vaccine development: neglected for how long?

INTRODUCTION

Lymphatic filariasis (LF), also known as elephantiasis, has been recognized by the world health organization and the centers for disease control and prevention as one of the neglected tropical diseases. The huge prevalence and risk of manifestation to date reflect the poor management of this disease. The disease poses vast public health and socio-economic burdens and generates a dire need for the development of a prophylactic solution for mass administration.

AREAS COVERED

Vaccination has been a sought-out strategy for dealing with ever-evolving infectious diseases and can be duly tuned to become a cost effective means of disease control and eventual eradication. In this review, we highlight the epidemiology of LF with the current diagnosis and treatment modules. The need for the development of a potential vaccine candidates, and challenges are discussed. The evidence presented in this review aims to enlighten the readers regarding the essential factors governing LF and its management using prophylactic measures.

EXPERT OPINION

The complex nature of filarial parasites is evident from the absence of a single vaccine for LF. The development and selection of an appropriate preclinical model and its translation into clinical practice is deemed to be a major task needing in-depth evaluation to formulate an effective vaccine. Explorations of the existing vaccine platforms would serve to be an apt strategy in this direction.

Immunolocalization of Disorganized Muscle Protein-1 in Different Life Stages of Human Lymphatic Filariid, Brugia malayi

Purpose

We recently identified disorganized muscle protein-1 of Brugia malayi (DIM-1bm) as a vaccine candidate for human lymphatic filariasis. The present study was aimed at investigating the localization of DIM-1bm in the life-stages of B. malayi to identify the tissue target of vaccine action.

Methods

Recombinant DIM-1bm (rDIM-1bm) was prepared and antibodies were raised in BALB/c mice. Immunoblots of SDS-PAGE resolved B. malayi infective 3rd stage larvae (L₃) and adult worm antigens and rDIM-1bm were prepared and reacted with anti-rDIM-1bm sera. Sections of adult female worms and whole-mount preparations of L₃ and microfilariae (mf) were stained by immunofluorescence using rDIM-1bm antibodies and Alexa Fluor 488 labeled secondary antibodies, and examined under a confocal microscope.

Results

Immunofluorescence staining showed that DIM-1bm is localized mainly in the subcuticular muscle layer in the L₃ and the adult worms; no fluorescent signal could be detected in mf.

Conclusion

The localization of DIM-1bm in the parasites’ muscle layer suggests that the immunoprophylactic efficacy of DIM-1 is evidently due to immobilization of the parasite and its subsequent immune elimination.

Advances in Vaccine Development for Human Lymphatic Filariasis

According to the World Health Organization, over 880 million people are currently at risk of acquiring lymphatic filariasis (LF) in over 52 countries worldwide. Current approaches to control LF by 2020 are short of the anticipated goal. Several studies suggest the existence of protective immunity against LF in humans. Thus, it is possible to develop a prophylactic vaccine against LF in humans. Several potential vaccine candidates were identified and tested for their potential against LF. To date, preclinical studies suggest that it is possible to develop a prophylactic vaccine against LF. Much work needs to be done, but it is clear that a prophylactic vaccine, combined with targeted chemotherapy, is critically required for eliminating LF worldwide.