Sharvan Sehrawat

• Ph.D
• Faculty Member at Indian Institute of Science Education and Research Mohali

To alleviate the contribution of antibody dependent enhancement in DenV pathogenesis, we obtain a DenV neutralizing single domain antibody (sdAb) from an in-house constructed phage display library of camelid VHH. The anti-DenV sdAb specifically reacts with the envelope (E) protein of DenV with a Kd value of 2x10⁸. Molecular dynamic simulations and...

Age-related alterations of the immune system compromise the host’s ability to respond to pathogens, but how immune aging is regulated is still poorly understood. Here, we identify via transcriptomic analysis of splenic DCs and bone marrow derived dendritic cells (BMDC) of young and aged mice, the small GTPase Rab8a as a regulator of dendritic cell...

We demonstrate the role of signaling via the glucocorticoid receptor, NR3C1, in differentiation of CD8+ T cell memory. Pharmacological inhibition as well as the short hairpin RNA–mediated knockdown of the receptor hindered memory transition and limited the homeostatic turnover of the activated CD8+ T cells. Dexamethasone exposure of CD8+ T cells ex...

Peste des petits ruminants virus (PPRV) is known to induce transient immunosuppression in infected small ruminants by modulating several cellular pathways involved in the antiviral immune response. Our study shows that the PPRV-coded non-structural proteins C and V can interact with the cellular NF-κB p65 subunit. The PPRV-C protein interacts with...

Morphine is a potent analgesic opiate used to treat chronic pain, mostly in cancer patients. In addition, it is widely used as a drug of abuse. Due to the continuous rise of morphine-associated addiction, there is an urgent need to develop pre-clinical animal models to understand the behavioural pattern of drug dependence and its withdrawal. Recent...

Autophagy is an essential and highly conserved catabolic process in cells, which is important in the battle against intracellular pathogens. Viruses have evolved several ways to alter the host defense mechanisms. PPRV infection is known to modulate the components of a host cell’s defense system, resulting in enhanced autophagy. In this study, we de...

In this review, we discuss a variety of immune modulating approaches that could be used to counteract tissue-damaging viral immunoinflammatory lesions which typify many chronic viral infections. We make the point that in several viral infections the lesions can be largely the result of one or more aspects of the host response mediating the cell and...

The protocol is designed to investigate the influence of an anti-cleavage site intrabody in modulating the output of LV(CoV-2 S), a lentivirus-based pseudovirus expressing CoV-2 S protein using HEK293T cells. We clone the single-domain antibody sequence into a lentiviral vector (pLenti-GFP) for intracellular expression and assess not only the viral...

The unprecedented success of mRNA vaccines in managing the COVID-19 pandemic raises the prospect of applying the mRNA platform to other viral diseases of humans and domesticated animals, which may lead to more efficacious vaccines for some agents. We briefly discuss reasons why mRNA vaccines achieved such success against COVID-19 and indicate what...

Novel vaccination strategies are crucial to efficiently control tuberculosis, as proposed by WHO under its flagship program 'End TB Strategy'. However, the emergence of drug-resistant strains of Mycobacterium tuberculosis (Mtb), particularly in those co-infected with HIV-AIDS, constitutes a major impediment to achieving this goal. We report here a...

We provide evidence on the TRM potentiation by glucocorticoids in stimulated CD8+ T cells. Signaling via glucocorticoid receptor reciprocally regulated short-lived effector cells and memory precursor effector cells. Influenza A virus infected mice treated transiently with dexamethasone preferentially generated multipotent TRM cells that efficiently...

We report robust SARS-CoV2 neutralizing sdAbs targeting the viral peptides encompassing the polybasic cleavage site (CSP) and in the receptor binding domain (RBD) of the spike (S) protein. Both the sdAbs inhibited infectivity of the CoV2 S protein expressing pseudoviruses (LV-CoV2S). Both anti-CSP and RBD intrabodies (IB) inhibited the output of LV...

The DF4nanoGrouping framework endorsed by the European Centre for Ecotoxicology and Toxicology of Chemicals employs acellular assays, in vitro and in vivo animal testing to perform hierarchical toxicity screening and...

Here, we describe a combinatorial approach in reverse vaccinology to identify immunogenic class I major histocompatibility complex (MHC) displayed epitopes derived from a morbillivirus named pestes des petits ruminants (PPRV). The protocol describes an in silico prediction of immunogenic epitopes using an IEDB tool. The predicted peptides were furt...

The study was aimed at developing an accessible laboratory animal model to elucidate protective and pathological roles of immune mediators during Peste des petits ruminants virus (PPRV) infection. It is because of the critical roles of type I IFNs in anti-viral defense, we assessed the susceptibility of IFN receptor knock out (IFNR KO) mice to PPRV...

We selected SARS-CoV2 specific single domain antibodies (sdAbs) from a previously constructed phage display library using synthetic immunogenic peptides of the virus spike (S) protein as bait. The sdAbs targeting the cleavage site (CS) and the receptor binding domain (RBD) in S protein efficiently neutralised the infectivity of a pseudovirus expres...

The COVID-19 pandemic has raised many issues not the least of which is the reason for its high variability in consequences to the infected person. In this opinion letter, we advocate that the dose and presentation of the infecting virus is a major factor that affects whether the outcome is subclinical, tissue damaging or even lethal following infec...

We demonstrate a rapid induction of type I IFN response in PPRV stimulated cells and the susceptibility of mice, genetically ablated of interferon response, to PPRV infection. Following PPRV infection, IFNR KO mice gradually reduced their body weights and succumbed to the infection within 10 days. While the infecting inoculum size did not alter the...

COVID-19 has become difficult to contain in our interconnected world. In this article, we discuss some approaches that could reduce the consequences of COVID-19. We elaborate upon the utility of camelid single-domain antibodies (sdAbs), also referred to as nanobodies, which are naturally poised to neutralize viruses without enhancing its infectivit...

In this commentary we argue that the hygiene hypothesis may apply to COVID-19 susceptibility and also that residence in low hygienic conditions acts to train innate immune defenses to minimize the severity of infection. We advocate that approaches, which elevate innate immune functions, should be used to minimize the consequences of COVID-19 infect...

Myeloid derived suppressor cells (MDSCs) are heterogeneous subsets of immature myeloid cells. Phenotypically such cells are identified as CD11b+Gr1lo-int cells in mice and CD33+CD11+LIN−HLA-DR− cells in humans. That MDSCs expand and modify the disease outcome in cancers and some infections is known. In this study, we investigated the role of MDSCs...

Myeloid derived suppressor cells (MDSCs) are heterogeneous subsets of immature myeloid cells. Phenotypically such cells are identified as CD11b+Gr1lo-int cells in mice and CD33+CD11+LIN−HLA-DR− cells in humans. That MDSCs expand and modify the disease outcome in cancers and some infections is known. In this study, we investigated the role of MDSCs...

Galectins play diverse roles in pathophysiology of infectious diseases and cancers. Galectin-3 is one of the most studied family member and the only chimeric type lectin. Many aspects of its biogenesis, range of activities and the disease modifying potential particularly during microbial infections are yet to be known. We review our current underst...

Despite continued destruction of human lives by snakebites, appreciable improvements in immunotherapies have not been made. We selected and characterized venom-specific single domain antibodies (sdAbs) from a constructed phage display library of camelid variable region of heavy chain of the heavy chain antibodies (VHHs). Secretory phospholipase A2-...

In this study, we investigated the response of myeloid-derived suppressor cells (MDSCs) during the pathogenesis of an immunoblinding disease of the cornea caused by HSV type 1 infection. We also measured the anti-inflammatory potential of in vitro-differentiated MDSCs in dampening herpetic stromal keratitis resulting from primary ocular HSV1 infect...

We investigated the influence of a transient treatment of corticosteroid on CD8⁺ T cells during herpesvirus infection. Dexamethasone, a synthetic corticosteroid, induced apoptosis of naïve and memory CD8⁺ T cells but virus-specific effector cells were spared. CD8⁺ T cell susceptibility was directly correlated with the expression of nr3c1. Both α-(H...

Table S3 Biological Processes That Are Affected by Downregulated Transcripts in Activated CD8+ TN Cells (as Analyzed by DAVID Gene Ontogeny Biological Processes), Related to Figures 1 and S1

Table S1 Differential Transcriptome of Naive and MHV68-Expanded CD8+ TN Cells, Related to Figures 1 and 2

Table S2 Biological Processes That Are Affected by Upregulated Transcripts in Activated CD8+ TN cells (as Analyzed by DAVID Gene Ontogeny Biological Processes; Percentage of Enrichment of Genes >1.0% and p Value > 0.05), Related to Figures 1 and 2

To gain insights into the molecular mechanisms and pathways involved in the activation of γ-herpesvirus (MHV68)-specific T cell receptor transnuclear (TN) CD8+ T cells, we performed a comprehensive transcriptomic analysis. Upon viral infection, we observed differential expression of several thousand transcripts encompassing various networks and pat...

Most vertebrates are infected with one or more herpesviruses and remain so for the rest of their lives. The relationship of immunocompetent healthy host with herpesviruses may sometime be considered as harmonious. However, clinically severe diseases can occur when host immunity is compromised due to aging, during some stress response, co-infections...

Understanding how different pathogens are sensed and recognised by the immune system and an appropriate response generated is critical for devising control strategies. Innate immunity is deployed immediately after the infection, while it takes several days before adaptive immunity effectively kicks in. Key differentiating features of two types of r...

It is now clear that the outcome of an inflammatory process caused by infections depends on the balance of responses by several components of the immune system. Of particular relevance is the interplay between regulatory T cells (Tregs) and CD4⁺ T cells that produce IL-17 (Th17 cells) during immunoinflammatory events. In addition to discussing stud...

Long-term treatment with the fungal metabolite drug FTY720 (Fingolimod) was shown to be highly effective in controlling viral immunopathological lesions. However, in this report we show that the anti-inflammatory effect of FTY720 in herpes simplex virus-1 (HSV-1) induced ocular inflammation is lost upon the discontinuation of treatment and lesions...

The host response to viruses includes multiple cell types that have regulatory function. Most information focuses on CD4(+) regulatory T cells that express the transcription factor Foxp3(+) (Tregs), which are the topic of this review. We explain how viruses through specific and non-specific means can trigger the response of thymus-derived natural T...

A monoclonal antibody against the C-type lectin DEC205 (αDEC205) is an effective vehicle for delivery of antigens to dendritic cells through creation of covalent αDEC205-antigen adducts. These adducts can induce antigen-specific T-cell immune responses or tolerance. We exploit the transpeptidase activity of sortase to install modified peptides and...

Key Points Antigen cross-presentation is regulated by the activity of deubiquitylase YOD1 that influences the control of viral infections. The enhanced cross-presentation depends on the proteasomal activity and the acidification status of APCs but is independent of functional TAP1.

To study the CD8(+) T cell response against a mouse γ-herpes virus, we generated K(b)-MHV-68-ORF8(604-612)RAG(-/-) CD8(+) T cell receptor transnuclear (TN) mice as a source of virus-specific CD8(+) T cells. K(b)-ORF8-Tet(+) CD8(+) T cells, expanded in the course of a resolving MHV-68 infection, served as a source of nucleus donors. Various in vivo...

Studies conducted in mice and humans have shown that IFN-γ+ CD8 T cell are the key effectors against liver-stage (LS) malaria; however, owing to complexities associated with the development of Plasmodia parasites, specificities of CD8 T cell effectors have been difficult to establish. Direct detection of Ag-specific CD8 T cells in high-throughput m...

In this report we show that the anti-inflammatory effect of FTY720 is lost on the discontinuation of treatment in Herpes Simplex Virus (HSV-I) induced ocular inflammation. The lesions developed after FTY720 treatment withdrawals were characterized by the predominance of Th17 cells over Th1 cells. Th17 but not Th1 cells expressed higher levels of su...

Stromal keratitis is a chronic immunopathological lesion of the eye caused by HSV-1 infection that can result in blindness. Because the inflammatory lesions are primarily orchestrated by Th1 cells, and to a lesser extent by Th17 cells, inhibiting their activity represents a useful form of therapy. In this study we evaluated the therapeutic potentia...

Stromal keratitis is a chronic immunopathological lesion of the eye caused by HSV-1 infection that can result in blindness. Because the inflammatory lesions are primarily orchestrated by Th1 cells, and to a lesser extent by Th17 cells, inhibiting their activity represents a useful form of therapy. In this study we evaluated the therapeutic potentia...

After HSV-1 infection, CD8(+) T cells accumulate in the trigeminal ganglion (TG) and participate in the maintenance of latency. However, the mechanisms underlying intermittent virus reactivation are poorly understood. In this study, we demonstrate the role of an inhibitory interaction between T cell Ig and mucin domain-containing molecule 3 (Tim-3)...

CD4(+) T cells, which express a master transcription factor, Foxp3, have been recognized as bona fide Tregs. These cells are essential to maintain immune homeostasis in healthy as well as infected mice and humans. Extensive investigations in the last decade have provided ways to manipulate the Foxp3(+) Treg response therapeutically so the role of s...

HSV-1 infection of the cornea leads to a blinding immunoinflammatory lesion of the eye termed stromal keratitis (SK). Recently, IL-17-producing CD4(+) T cells (Th17 cells) were shown to play a prominent role in many autoimmune conditions, but the role of IL-17 and/or of Th17 cells in virus immunopathology is unclear. In this study, we show that, af...

After HSV-1 infection, CD8(+) T cells accumulate in the trigeminal ganglion (TG) and participate in the maintenance of latency. However, the mechanisms underlying intermittent virus reactivation are poorly understood. In this study, we demonstrate the role of an inhibitory interaction between T cell Ig and mucin domain-containing molecule 3 (Tim-3)...

The normal cornea is transparent, which is essential for normal vision, and although the angiogenic factor vascular endothelial growth factor A (VEGF-A) is present in the cornea, its angiogenic activity is impeded by being bound to a soluble form of the VEGF receptor-1 (sVR-1). This report investigates the effect on the balance between VEGF-A and s...

Many viruses infect humans and most are controlled satisfactorily by the immune system with limited damage to host tissues. Some viruses, however, do cause overt damage to the host, either in isolated cases or as a reaction that commonly occurs after infection. The outcome is influenced by properties of the infecting virus, the circumstances of inf...

Comparison of antigen-specific CD8+ T cell responses (measured by ICCS assay) in Gal-9 KO and WT mice at different times after HSV infection. Age and gender matched WT and Gal-9 KO animals were infected in footpad with 2.5x105 PFU of HSV KOS. At indicated time points, three animals were sacrificed and the SSIEFERAL specific IFN-γ producing cell num...

C57BL/6 animals were infected in each hind footpad with 2.5x105 PFU of HSV. At different time points after infection, splenocytes isolated from three animals at each time point were analyzed flow cytometrically for TIM-3 and IFN-γ expression. A. Representative FACS plots show the frequencies of TIM-3+ and IFN-γ+ in CD8+ T cell gated populations. B....

C57BL/6 animals were infected in each hind footpad with 2.5x105 PFU of HSV and the concentration of Gal-9 in the PLN samples of infected animals was measured by sandwich ELISA using anti-Gal-9 (108A2) mAb. (0.18 MB TIF)

C57BL/6 WT and Gal-9 KO animals were infected in each hind footpad with 2.5x105 PFU of HSV and cytokine producing CD8+ T cells were quantified using ICCS assays at 5.5dpi. The FACS plots (A) and bar diagram (B) show the frequencies of SSIEFARL peptide stimulated IL-2 and IFN-γ producing CD8+ T cells. (0.27 MB TIF)

Author Summary Adaptive immune responses to foreign antigens require precise regulation, otherwise excessive bystander damage to host tissues may occur and responses to other antigens could be compromised. Some galectin proteins binding to receptors on cells of the immune system form part of the regulatory system, although this topic has received s...

We demonstrate that galectin-9 (Gal-9) acts to constrain CD8+ T cell immunity to Herpes Simplex Virus (HSV) infection. In support of this, we show that animals unable to produce Gal-9, because of gene knockout, develop acute and memory responses to HSV that are of greater magnitude and better quality than those that occur in normal infected animals...

Controlling chronic immunoinflammatory diseases such as lesions in the eye caused by infection with HSV represents a therapeutic challenge. Since CD4(+) T cells are the primary orchestrators of lesions, targeting activated CD4(+) T cell subsets and increasing the representation of cells that express regulatory function would be a logical therapeuti...

TIM-3 (T cells immunoglobulin and mucin -3) is a surface protein expressed differentially on terminally differentiated Th1 but not Th2 cells. Ligation of galectin-9 with TIM-3 on Th1 cells induces a lethal signal leading to apoptosis of these cells. We report here that same molecule i.e. TIM-3, when expressed on Foxp3+ Tregs, instead of delivering...

FTY720 has been used to control inflammatory lesions, but the mechanisms by which the drug acts in vivo are poorly understood. Such mechanisms may result primarily from effects on lymphocyte and dendritic cell homing to lymphoid and inflammatory sites. We demonstrate that FTY720 may also act by causing the conversion of TCR-stimulated nonregulatory...

Two prominent anti-inflammatory mechanisms involved in controlling HSV-1-induced corneal immunopathology (stromal keratitis or SK) are the production of the cytokine IL-10 and the activity of natural regulatory T cells (nTregs). It is not known whether, under in vivo conditions, IL-10 and nTregs influence the corneal pathology independently or in c...

Generating and using regulatory T cells (Tregs) to modulate inflammatory disease represents a valuable approach to therapy but has not yet been applied as a means to control virus-induced immunopathological reactions. In this report, we developed a simplified technique that used unfractionated splenocytes as a precursor population and showed that s...

A previous model of stromal keratitis (SK) developed in our laboratory was established in which several TCR transgenic (Tg) mice back crossed to SCID or RAG KO were shown to develop typical SK lesions upon ocular infection with HSV. The lesions were judged to be the consequence of a bystander activation of T cells that in turn orchestrated tissue d...

Our past studies have shown a protective role for both CD4+CD25+Foxp3+ natural regulatory T cells (nTregs) as well as IL-10 in Herpes Simplex Virus (HSV) induced Stromal Keratitis (SK). Among several other mechanisms, IL-10 has been shown to be involved in the nTreg mediated suppression. We have shown in vitro that blocking of IL-10 could partially...

Increasing age is associated with the lesser ability of T and B cells to mount an effective immune response against the microbial antigens. Numerous reports have documented the malfunctioning of the different components of immune system with aging but a more detailed mechanistic understanding of the age associated immunological changes in the elder...

Various cell types that express regulatory function may influence the pathogenesis of most and perhaps all infections. Some regulatory cells are present at the time of infection whereas others are induced or activated in response to infection. The actual mechanisms by which different types of infections signal regulatory cell responses remain poorl...

Heavy chain antibodies (HCAbs) of IgG2 and IgG3 subtypes were purified from the sera of Indian desert camel (Camelus dromedarius L.) by ammonium sulphate precipitation, followed by ion-exchange chromatography on DEAE-cellulose and affinity chromatography on protein A-sepharose and protein G-sepharose, and characterized by SDS-polyacrylamide gel ele...