Patterns of human immunodeficiency virus drug resistance mutations in people living with human immunodeficiency virus in India: A scoping review.

The human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) epidemic still exists as a major global public health burden, especially in the middle- and low-income countries. Antiretroviral therapy (ART) remains a sole option to reduce the mortality and morbidity associated with this disease as no approved vaccine candidates are available. About 67% of the people living with HIV (PLHIV) have received the ART in 2019 worldwide. As a consequence of increased ART regimes, the prevalence of drug resistance mutations (DRM) also has been escalating and it would become a significant barrier in achieving the United Nations Programme on HIV/AIDS goal of eliminating HIV by 2030. So far, nucleoside reverse transcriptase inhibitors (NRTI), non-nucleoside reverse transcriptase inhibitors (NNRTI), and protease inhibitor-(PI) associated DRM have been reported across the globe with a considerable escalation in the annual prevalence rate of pretreatment NNRTI DRM. Conversely, NRTI-associated DRM is still under 5%, with a few scattered reports of significant increase from few countries such as southern and eastern Africa. Likewise, in India, the propositions of NRTI and NNRTI-associated DRM have increased since the commencement of the nationwide ART program in 2004. In agreement to the global trend, M1841/V, a type of NNRTI, remains as a dominant DRM among PLHIV. In this review, we tried to collate various mechanisms of DRM in PLHIV. In addition, patterns of HIV DRM in India and their future challenges on drug-related mutations have been discussed.

Epitope mapping of Brugia malayi ALT-2 and the development of a multi-epitope vaccine for lymphatic filariasis.

Human lymphatic filariasis is a neglected tropical disease, causing permanent and long-term disability with severe immunopathology. Abundant larval transcript (ALT) plays a crucial role in parasite establishment in the host, due to its multi-faceted ability in host immune regulation. Although ALT protein is a key filarial target, its exact function is yet to be explored. Here, we report epitope mapping and a structural model of Brugia malayi ALT-2, leading to development of a multi-epitope vaccine. Structural analysis revealed that ALT represents unique parasitic defence proteins belonging to a toxin family that carries a 'knottin' fold. ALT-2 has been a favourite vaccine antigen and was protective in filarial models. Due to the immunological significance of ALT-2, we mapped B-cell epitopes systematically and identified two epitope clusters, 1-30 and 89-128. To explore the prophylactic potential of epitope clusters, a recombinant multi-epitopic gene comprising the epitopic domains was engineered and the protective efficacy of recombinant ALT epitope protein (AEP) was tested in the permissive model, Mastomys coucha. AEP elicited potent antibody responses with predominant IgG1 isotype and conferred significantly high protection (74.59%) compared to ALT-2 (61.95%). This proved that these epitopic domains are responsible for the protective efficacy of ALT-2 and engineering protective epitopes as a multi-epitope protein may be a novel vaccine strategy for complex parasitic infections.

Chimeric Epitope Vaccine from Multistage Antigens for Lymphatic Filariasis.

Lymphatic filariasis, a mosquito-borne parasitic disease, affects more than 120 million people worldwide. Vaccination for filariasis by targeting different stages of the parasite will be a boon to the existing MDA efforts of WHO which required repeated administration of the drug to reduce the infection level and sustained transmission. Onset of a filaria-specific immune response achieved through antigen vaccines can act synergistically with these drugs to enhance the parasite killing. Multi-epitope vaccine approach has been proved to be successful against several parasitic diseases as it overcomes the limitations associated with the whole antigen vaccines. Earlier results from our group suggested the protective efficacy of multi-epitope vaccine comprising two immunodominant epitopes from Brugia malayi antioxidant thioredoxin (TRX), several epitopes from transglutaminase (TGA) and abundant larval transcript-2 (ALT-2). In this study, the prophylactic efficacy of the filarial epitope protein (FEP), a chimera of selective epitopes identified from our earlier study, was tested in a murine model (jird) of filariasis with L3 larvae. FEP conferred a significantly (P < 0.0001) high protection (69.5%) over the control in jirds. We also observed that the multi-epitope recombinant construct (FEP) induces multiple types of protective immune responses, thus ensuring the successful elimination of the parasite; this poses FEP as a potential vaccine candidate.

Tandem antioxidant enzymes confer synergistic protective responses in experimental filariasis.

Helminth parasites use antioxidant defence strategies for survival during oxidative stress due to free radicals in the host. Accordingly, tissue-dwelling filarial parasites counteract host responses by releasing a number of antioxidants. Targeting these redox regulation proteins together, would facilitate effective parasite clearance. Here, we report the combined effect of protective immune responses trigged by recombinant Wuchereria bancrofti thioredoxin (WbTRX) and thioredoxin peroxidase (WbTPX) in an experimental filarial model. The expression of WbTRX and WbTPX in different stages of the parasite and their cross-reactivity were analysed by enzyme-linked immunosorbent assay (ELISA). The immunogenicity of recombinant proteins and their protective efficacy were studied in animal models when immunized in single or cocktail mode. The antigens showed cross-reactive epitopes and induced high humoral and cellular immune responses in mice. Further, parasite challenge against Brugia malayi L3 larvae in Mastomys coucha conferred significant protection of 57% and 62% against WbTRX and WbTPX respectively. The efficacy of L3 clearance was significantly higher (71%) (P <  0.001) when the antigens were immunized together, showing a synergistic effect in multiple-mode vaccination. Hence, the study suggests WbTRX and WbTPX to be attractive vaccine candidates when immunized together and provides a tandem block for parasite elimination in the control of lymphatic filariasis.

Dominant T-cell epitopes of filarial BmALT-2 and their cytokine profile in BALB/c mice.

Filarial nematodes down-regulate the host immune response to establish infection by inducing IL-10-mediated T-cell suppression.Abundant larval transcript (ALT) proteins are of major interest as they are expressed abundantly in the L3 stage, implicated in protective immunity and may play a role in immune evasion. The T-cell epitopes of BmALT-2 and the cytokine responses induced by these peptides were investigated in a mouse model using synthetic peptides, which could be exploited in the design of a potent epitope-based vaccine. Five regions were found to carry T-cell epitopes inducing high levels of cellular proliferation. The regions 55­68 and 73­91 of ALT-2 induced very high levels of IL-10 secretion and hence could be involved in immunomodulation in the host.

Crucial epitopes of Wuchereria bancrofti abundant larval transcript recognized in natural infection.

Lymphatic filariasis is a tropical disease, with over 40 million people seriously incapacitated due to lymphangitis and elephantiasis. Over 99% of infections are caused by the nematode Wuchereria bancrofti. Expressed sequence tag (EST) analysis of filarial genome identified novel infective larval (L3) stage-specific antigen, abundant larval transcript (ALT-2), which was shown to be highly essential for parasite establishment and survival in the host. The unique structural features and immunological characteristics of ALT-2 indicate the presence of critical motifs that needs to be explored in natural human infection for understanding and management of the disease. In order to dissect the epitopes of ALT protein recognized in humans, eight peptides spanning the entire protein sequence were selected based on in-silico epitope prediction and synthesized. Analysis of the reactivity of W. bancrofti ALT-2 synthetic peptides with clinical sera (n = 40) from endemic areas identified epitopes recognized by putatively immune sera, of which two comprise the highly variable acidic domain (21-60). Interestingly, our study also revealed crucial epitopes recognized by microfilaremic (MF) sera with significantly high IgG4 isotype (p < 0.001), implicated in immunomodulation. The epitope peptides identified were highly specific for MF sera and, thus, have the potential to be exploited as diagnostic markers.