Uday Kumaraguru

CD4+CD25+ T Cells Regulate Virus-specific Primary and Memory CD8+ T Cell Responses

Naturally occurring CD4+CD25+ regulatory T cells appear important to prevent activation of autoreactive T cells. This article demonstrates that the magnitude of a CD8+ T cell–mediated immune response to an acute viral infection is also subject to control by CD4+CD25+ T regulatory cells (Treg). Accordingly, if natural Treg were depleted with specific anti-CD25 antibody before infection with HSV, the resultant CD8+ T cell response to the immunodominant peptide SSIEFARL was significantly enhanced. This was shown by several in vitro measures of CD8+ T cell reactivity and by assays that directly determine CD8+ T cell function, such as proliferation and cytotoxicity in vivo. The enhanced responsiveness in CD25-depleted animals was between three- and fourfold with the effect evident both in the acute and memory phases of the immune response. Surprisingly, HSV infection resulted in enhanced Treg function with such cells able to suppress CD8+ T cell responses to both viral and unrelated antigens. Our results are discussed both in term of how viral infection might temporarily diminish immunity to other infectious agents and their application to vaccines. Thus, controlling suppressor effects at the time of vaccination could result in more effective immunity.

CD4+CD25+ Regulatory T Cells Control the Severity of Viral Immunoinflammatory Lesions

CD4+CD25+ regulatory T cells (Treg) can inhibit a variety of autoimmune and inflammatory diseases, but their involvement in regulating virus-induced immunopathology is not known. We have evaluated the role of Treg in viral immunopathological lesion stromal keratitis. This frequent cause of human blindness results from a T cell-mediated immunoinflammatory response to HSV in the corneal stroma. The results show that lesions were significantly more severe if mice were depleted of Treg before infection. The Treg was also shown to modulate lesion expression induced by adoptive transfer of pathogenic CD4+ T cells in infected SCID recipients. The mechanism of Treg control of stromal keratitis involved suppressed antiviral immunity and impaired expression of the molecule required for T cell migration to lesion sites. Interestingly, Treg isolated from ocular lesions in nondepleted mice showed in vitro inhibitory effects involving IL-10, but were not very effective in established lesions. Our results decipher the in vivo role of Treg in a virus-induced immunopathology and imply that manipulation of regulatory cell function represents a useful approach to control viral-induced immunoinflammatory disease.

Control of Stromal Keratitis by Inhibition of Neovascularization

Stromal keratitis resulting from ocular infection with herpes simplex virus is a common cause of blindness. This report investigates the role of neovascularization in the pathogenesis of stromal keratitis by measuring the outcome of treatment with the potent anti-angiogenesis cytokine endothelial monocyte-activating polypeptide II (EMAP II). We show that systemic and topical administration of EMAP II from the outset of infection resulted in markedly diminished levels of herpes simplex virus-induced angiogenesis and significantly reduced the severity of stromal keratitis lesions. EMAP II treatment had no demonstrable pro-inflammatory or toxic effects and failed to express antiviral activity. The mechanism of action of EMAP II was shown to proceed by causing apoptosis in vascular endothelial cells. Our data document for the first time the essential role of angiogenesis in the pathogenesis of stromal keratitis and also indicate that the therapy of herpetic stromal keratitis could benefit by procedures that diminish angiogenesis.

Induction of CD8 T-cell-specific systemic and mucosal immunity against herpes simplex virus with CPG-peptide complexes

ABSTRACT Oligodeoxynucleotides (ODN) containing unmethylated CpG motifs exert powerful adjuvant activity in vivo and in vitro. Administered with antigen they induce a population of antigen-specific CD8+ T cells. In this study we immunized C57BL/6 mice with bioactive CpG ODN combined with an immunodominant epitope derived from herpes simplex virus (HSV) glycoprotein B (amino acids 498 to 505; SSIEFARL) and analyzed the magnitude and durability of the peptide-specific response. The effectiveness of the CD8+ T-cell response as measured by peptide-specific tetramers, peptide-induced intracellular gamma interferon expression, and resistance to systemic and mucosal challenge during the acute and memory phases was compared with the response induced by immunization with recombinant vaccinia virus encoding SSIEFARL as a minigene (VvgB498-505). Confirming the reports of others, our results demonstrate that the CpG ODN-peptide approach generates an antigen-specific CD8+ T-cell population, but the frequency of CD8+ T cells is lower than that induced by VvgB498-505. Nevertheless, the protection level was comparable when mice were systemically and mucosally challenged during the acute phase. However, such responses by both groups waned with time and were functionally less effective. Still, our results indicate that the CpG ODN-peptide immunization system holds promise as a means of selectively inducing a CD8+ T-cell response against HSV.

Natural Killer Cells as Novel Helpers in Anti-Herpes Simplex Virus Immune Response

ABSTRACT Innate defenses help to eliminate infection, but some of them also play a major role in shaping the magnitude and efficacy of the adaptive immune response. With regard to influencing subsequent adaptive immunity, NK cells aided by dendritic cells may be the most relevant components of the innate reaction to herpes simplex virus (HSV) infection. We confirm that mice lacking or depleted of NK cells are susceptible to HSV-induced lesions. The quantity and quality of CD8+ cytotoxic T lymphocytes generated in the absence of NK cells were diminished, thereby contributing to susceptibility to HSV-induced encephalitis. We demonstrate a novel helper role for NK cells, in that NK cells compensate for the loss of CD4 helper T cells and NK cell supplementation enhances the function of wild type anti-HSV CD8 T cells. In addition, NK cells were able to partially rescue the dysfunctional CD8+ T cells generated in the absence of CD4 T helper cells, thereby performing a novel rescue function. Hence, NK cells may well be exploited for enhancing and rescuing the T-cell response in situations where the CD4 helper response is affected.

PD-1 modulates regulatory T cells and suppresses T-cell responses in HCV-associated lymphoma

T regulatory (TR) cells suppress T‐cell responses that are critical in the development of chronic viral infection and associated malignancies. Programmed death‐1 (PD‐1) also has a pivotal role in regulation of T‐cell functions during chronic viral infection. To examine the role of PD‐1 pathway in regulating TR‐cell functions that inhibit T‐cell responses during virus‐associated malignancy, TR cells were investigated in the setting of hepatitis C virus‐associated lymphoma (HCV‐L), non‐HCV‐associated lymphoma (non‐HCV‐L), HCV infection alone and healthy subjects (HS). Relatively high numbers of CD4+CD25+ and CD8+CD25+ TR cells, as well as high levels of PD‐1 expressions on these TR cells were found in the peripheral blood of subjects with HCV‐L compared with those from non‐HCV‐L or HCV alone or HS. TR cells from the HCV‐L subjects were capable of suppressing the autogeneic lymphocyte response, and depletion of TR cells in peripheral blood mononuclear cells from HCV‐L improved T‐cell proliferation. Additionally, the suppressed T‐cell activation and proliferation in HCV‐L was partially restored by blocking the PD‐1 pathway ex vivo, resulting in both a reduction in TR‐cell number and the ability of TR to suppress the activity of effector T cells. This study suggests that the PD‐1 pathway is involved in regulating TR cells that suppress T‐cell functions in the setting of HCV‐associated B‐cell lymphoma.

Pre-Term Exposure Patterns in Neonatal Intensive Care Unit Alters Immunological Outcome in Neonates

Advances in technology have lowered the limits of viability in premature births to 24 weeks of gestation. This brought forth a new population of children, who are born 3-4 months early and spent considerable amounts of time in neonatal intensive care unit (NICU), instead of sterile environment of mother’s womb. Besides, other problems associated with prematurity, these children often undergo invasive procedures resulting in mucosal inflammation and/ or injury by feeding tubes, endotracheal tubes, and prolonged IV catheter. To test whether “ex-preemie-infants” were different than “term-infants” with regard to their immunity, preterm infants (< 32 weeks) and term infants (control) at the corrected age of 9-12 months were analyzed for their resting and stimulated immune responses. Preterm infants had a significant Th1 skewed response, higher number of activated and functionally competent T cells compared to term infants. The critical role of neonatal environmental exposure on immune system development is imminent; nevertheless detailed mechanistic studies on pathways are warranted.

Viral Vaccines and CTL Response

Immune induction by successful vaccine formulations seems to involve stimulation of both humoral and cellular arms of immunity. Nevertheless, CD8+ CTLs are of critical relevance in the context of intracellular infection and tumor for many reasons. The task of exerting antipathogen activity by CD8+ T cells, which principally function to control and eradicate intracellular pathogens, is enabled by constitutive expression of MHC class-I molecules on all tissue types. CTL induction offers hope for vaccines against pathogens that are resistant to neutralizing activity. This review discusses the mechanism of immune induction by some successful vaccines and based on the accrued evidence suggests ideas for improved design of CTL-inducing vaccines.

Herpes Simplex Virus Induces the Early Activation of NK Cell via MyD88- Dependent Signal~!2009-12-24~!2010-05-14~!2010-06-22~!

In the course of a Herpes Simples Virus type-1 (HSV-1) infection, the bidirectional cross-talk between Natural Killer (NK) cells and Dendritic Cells (DCs) is imperative in mounting an efficient immunological response. Enhanced DC maturation by Toll-Like Receptor (TLR) ligands is considered as a pivotal link between innate and adaptive immune responses, yet the impact of direct TLR signaling on NK:DC interaction during an HSV infection has yet to be examined. We demonstrate that HSV mediates the activation of NK cells and the induction of the cooperative relationship between NK cells and DCs via TLR. During the course of an HSV infection, the initial response required both types of innate cells and demonstrated phenotypic and functional activation much like that of TLR-stimulated cells. Using a MyD88 knock-out system diminished the early interaction between DCs and NK after HSV exposure. Our results indicate that HSV TLR- ligands modulate the early NK: DC interaction and may be a mechanism used by these innate immune cells to overcome virus mediated immune evasion and the initiation of a potent acquired immune response.