Regulation of Herpetic Stromal Keratitis: Role of Regulatory T Cells

Herpetic stromal keratitis (HSK) is an immunoinflammatory corneal lesion caused by herpes simplex virus (HSV) infection. One of the dire consequences of which is blindness resulting from tissue destructive immunopathological reaction in corneal stroma. The lesion is considered to be orchestrated mainly by CD4+ T cells of Th1 phenotype. Studies on two animal models viz. immunocompetent and immunodeficient, shed light on the issues on specificity of the cells which at least in immunocomprised TCR transgenic animals were shown to be activated in a bystander manner. However, initial infiltration by innate immune cells in response to replicating virus set the stage for the chronic inflammation in the corneal stroma. Paradoxically, these cells are also critical in the control of virus in the cornea. The first part (Part I) of this dissertation focuses on the understanding of HSV-1 induced immunoinflammatory processes in the cornea and trigeminal ganglia including the secondary lymphoid tissues and the involvement of regulatory mechanisms. The next three parts (Part II-IV) focus on the control of the inflammatory lesion and anti-inflammatory mechanisms that are activated following virus infection in the lymphoid organs and cornea. Results in Part II evaluate the immunotherapeutic potential of regulatory T cells in controlling the progression of the inflammatory lesions after ocular HSV infection. Results of the third section show that sequestration of T effector cells in the lymphoid organs and limited access to site of inflammation using a drug FTY720 after HSV infection resulted in diminished severity of SK and expansion of antigen-specific regulatory T cells that could contribute to the diminution of lesion severity. The fourth section describes the role of a previously unexplored inhibitory interaction between a Th1 specific cell surface marker, TIM-3 and its ligand galectin-9 in the causation of the viral induced corneal immunopathology. The administration of galectin-9 seemed to be an effective approach to terminate Th1 responses and promote regulatory cells activity thereby controlling the severity of lesions. In this study, experiments were designed to control the progression of the ongoing inflammatory reaction in the cornea in order to evaluate some of the therapeutic strategies for HSK

Controlling viral inflammatory lesions by rebalancing immune response patterns

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 tissue damage rather than the virus itself being directly responsible. However, within the reactive inflammatory lesions along with the pro-inflammatory participants there are also other aspects of the host response that may be acting to constrain the activity of the damaging components and are contributing to resolution. This scenario should provide the prospect of rebalancing the contributions of different host responses and hence diminish or even fully control the virus-induced lesions. We identify several aspects of the host reactions that influence the pattern of immune responsiveness and describe approaches that have been used successfully, mainly in model systems, to modulate the activity of damaging participants and which has led to lesion control. We emphasize examples where such therapies are, or could be, translated for practical use in the clinic to control inflammatory lesions caused by viral infections

Galectin-9/TIM-3 Interaction Regulates Virus-Specific Primary and Memory CD8+ T Cell Response

In this communication, we demonstrate that galectin (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. Interestingly, infusion of normal infected mice with α-lactose, the sugar that binds to the carbohydrate-binding domain of Gal-9 limiting its engagement of T cell immunoglobulin and mucin (TIM-3) receptors, also caused a more elevated and higher quality CD8+ T cell response to HSV particularly in the acute phase. Such sugar treated infected mice also had expanded populations of effector as well as memory CD8+ T cells. The increased effector T cell responses led to significantly more efficient virus control. The mechanisms responsible for the outcome of the Gal-9/TIM-3 interaction in normal infected mice involved direct inhibitory effects on TIM-3+ CD8+ T effector cells as well as the promotion of Foxp3+ regulatory T cell activity. Our results indicate that manipulating galectin signals, as can be achieved using appropriate sugars, may represent a convenient and inexpensive approach to enhance acute and memory responses to a virus infection

<span style="mso-bidi-language:HI">Physico-chemical and antigenic characterization of unconventional heavy chain antibodies of Indian desert camel (<i>Camelus dromedarius </i>L.) </span>

299-304Heavy 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 SOS-polyacrylamide gel electrophoresis, agar gel immunodiffusion (AGIO), counter-immunoelectrophoresis (CIEP), immunoelectrophoresis (IEP), ELISA and immunoblotting. IgG2 and IgG3 were found to have molecular mass 46.77 kDa and 43.65 kDa, respectively by SOS-PAGE under reducing conditions. They migrated in β-region in IEP and could be detected in CIEP, because of being more negatively charged and smaller size. Anti-camel IgG3 cross-reacted in AGIO, ELISA and immunoblotting with IgGs of pig and ruminants (cattle, buffalo, sheep and goat), but not with immunoglobulins from horse, dog, guinea pigs, mice, fish, poultry and human. The present findings suggest close antigenic relationship of camels with pigs and ruminants. </span

Herpesviruses: Harmonious Pathogens but Relevant Cofactors in Other Diseases?

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 or during neoplastic disease conditions. Discord can also occur during iatrogenic immunosuppression used for controlling graft rejection, in some primary genetic immunodeficiencies as well as when the virus infects a non-native host. In this review, we discuss such issues and their influence on host-herpesvirus interaction

In Vitro-Generated Antigen-Specific CD4+ CD25+ Foxp3+ Regulatory T Cells Control the Severity of Herpes Simplex Virus-Induced Ocular Immunoinflammatory Lesions▿

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 stimulation under optimized conditions for 5 days with solid-phase anti-CD3 monoclonal antibody in the presence of transforming growth factor β (TGF-β) and interleukin-2 could induce up to 90% of CD4+ T cells to become Foxp3+ and able to mediate suppression in vitro. CD11c+ dendritic cells were intricately involved in the conversion process and, once modified in the presence of TGF-β, could convert Foxp3− CD4+ cells into Foxp3+ CD4+cells by producing TGF-β. The converted cells had undergone cell division, and the majority of them expressed activation markers along with surface molecules that would facilitate their migration into tissue sites. The primary reason for our study was to determine if such in vitro-converted Tregs could be used in vivo to influence the outcome of a virus-induced immunoinflammatory lesion in the eye caused by herpes simplex virus infection. We could show in three separate models of herpetic stromal keratitis that adoptive transfers of in vitro-converted Tregs effectively diminished lesion severity, especially when given in the initial phases of infection. The suppression effect in vivo appeared to be polyspecific. The protocol we have developed could provide a useful additional approach to control virus-induced inflammatory disease