Role of natural killer T cells (NKT) cells in immunity to herpes simplex virus type 1.

Herpes simplex virus type I (HSV-I) produces acute muco-cutaneous infections, followed by spread to sensory nerve ganglia, and establishment of latency. In the peripheral nervous system, primary sensory neurons, which are found in dorsal root ganglia of the of the spinal nerves, are the target for HSV and they may undergo either productive or latent intection. Productive infection of sensory neurons generates the potential for lethal spread of virus through the nervous system but in immunocom petent hosts, viral replication is terminated by limely development of an adaptive immune response. The infection of dorsal root ganglia that follows cutaneous inoculation of the flanks of mice with HSV provides a well-characterized model of peripheral nervous system infection. The mechanisms responsible for clearance of HSV are complex. At mucosal and cutaneous sites, local innate immune mechanisms act to interrupt the initial spread of virus to the nervous system, while adaptive immunity is important in limiting replication in the ganglia and extension of the virus to adjacent dennatomes. Thus actions of both the innate and the adaptive immune systems are vital in defence against replicating HSV-1, while it is thought that latent infection in the ganglia is contained by the surveillance of the adaptive immune system. Natural killer T (NKT) cells are a conserved subpopulation of lymphocytes that recognize glycolipid antigens presented by the invariant MHC class I-like molecule CD1d. Upon activation through their semi-invariant T cell receptor, these cells rapidly release large amounts of immuno-modulating Th1 and Th2 cytokines. NKT cells have, therefore, been implicated in immune responses controlling various diseases, including infection, cancer, and autoimmunity, as well as having an involvement in allo-graft survival. Consideration of the important contributions of innate and adaptive immunity to clearance of HSV prompted this investigation of the role of CD1d and of CD1d-restricted NKT cells in the pathogenesis of HSV infection. The first part of this thesis (Chapter 3 and 4) describes investigations into the role of NKT cells in immunity to HSV-1, using a zosteriform model of infection and two gene knockout strains of C57BL/6 mice. CD1d GKO and Ja18 GKO mice, which are deficient in NKT cells, are compromised in controlling HSV-1 as evidenced by mortality, virus loads in skin and dorsal root ganglia, presence and size of skin lesions, persistence of HSV antigen, neuronal damage and extent of latency. Comparisons between wild type (NKT cell replete), Ja18 GKO (deficient in invariant Va14⁺ NKT cells) and CD1d GKO (deficient in all CD1d-dependant NKT cells) mice allowed assessment of CD1d-dependant NKT cell subsets in defence against the virus at various stages of infection. It was concluded that both subsets play important roles in controlling the virus and in preventing lethal neuro-invasive disease, that both are vital adjuncts to the adaptive immune response and that without them, low doses of neuropathogenic HSV-1 can establish quickly and cause fatal infections. The NKT-cell population appears to be quite dynamic in its response to a range of pathogens and other disease processes. The study described in Chapter 5 presents evidence suggesting that the response of NKT cells during HSV infection is no less dynamic. In the axillary lymph nodes, observations on numbers of cells expressing NK1.1 antigen and the invariant TCR suggest that NKT cells are activated in the regional lymph nodes draining the infection site. Observations on lymphocytes prepared from liver and spleen also suggested activation of NKT cells, indicating that NKT cells at these sites are also activated during the course of acute HSV infection. The role of NKT cells in the control of HSV infection was further examined by adoptive transfer studies, to investigate whether the defect in handling of HSV-1 by Ja18 GKO mice could be complemented by the adoptive transfer of lymphocytes from wt mice (Chapter 6). Finally, the relevance of activated NKT cells in the anti-HSV response was examined by observing the effects of a-GalactosylCeramide therapy on the severity of HSV-1 infection (Chapter 6). Activation of NKT cells by this compound delayed the onset of HSV disease, decreased prevalence and severity of zosteriform lesions and reduced viral titres in skin and ganglia. The beneficial effects of a-GalactosylCeramide on the outcome and severity of HSV infection in the skin were dose-dependent. Collectively, the studies described in this thesis provide insights into how NKT cells, normally a rare population of cells, has the ability to regulate the protective immune response to HSV-1. As more understanding is gained about how NKT cells become activated during HSV-1 infection, and how they mediate their antiviral effects, other ways may be developed to modulate and activate this interesting subset to the benefit of infected individuals.Thesis (Ph.D.) -- University of Adelaide, School of Molecular and Biomedical Science, 200

Emerging targets for developing T cell-mediated vaccines for human immunodeficiency virus (HIV)-1

Human immunodeficiency virus (HIV)-1 has infected >75 million individuals globally, and, according to the UN, is responsible for ~2.1 million new infections and 1.1 million deaths each year. Currently, there are ~37 million individuals with HIV infection and the epidemic has already resulted in 35 million deaths. Despite the advances of anti-retroviral therapy (ART), a cost-effective vaccine remains the best long-term solution to end the HIV-1 epidemic especially given that the vast majority of infected individuals live in poor socio-economic regions of the world such as Sub-Saharan Africa which limits their accessibility to ART. The modest efficacy of the RV144 Thai trial provides hope that a vaccine for HIV-1 is possible, but as markers for sterilizing immunity are unknown, the design of an effective vaccine is empirical, although broadly cross-reactive neutralizing antibodies (bNAb) that can neutralize various quasispecies of HIV-1 are considered crucial. Since HIV-1 transmission often occurs at the genito-rectal mucosa and is cell-associated, there is a need to develop vaccines that can elicit CD8+ T cell immunity with the capacity to kill virus infected cells at the genito-rectal mucosa and the gut. Here we discuss the recent progress made in developing T cell-mediated vaccines for HIV-1 and emphasize the need to elicit mucosal tissue-resident memory CD8+ T (CD8+ Trm) cells. CD8+ Trm cells will likely form a robust front-line defense against HIV-1 and eliminate transmitter/founder virus-infected cells which are responsible for propagating HIV-1 infections following transmission in vast majority of cases.From the National Health and Medical Research Council (NHMRC): grants APP1026293 (EG), APP525431 (CR), APP543139 (EG), and APP543143 (EG). From the Australian Centre for HIV and Hepatitis Virology Research, CR received an EOI gran

Robust and prototypical immune responses toward COVID-19 vaccine in First Nations peoples are impacted by comorbidities

High-risk groups, including Indigenous people, are at risk of severe COVID-19. Here we found that Australian First Nations peoples elicit effective immune responses to COVID-19 BNT162b2 vaccination, including neutralizing antibodies, receptor-binding domain (RBD) antibodies, SARS-CoV-2 spike-specific B cells, and CD4+ and CD8+ T cells. In First Nations participants, RBD IgG antibody titers were correlated with body mass index and negatively correlated with age. Reduced RBD antibodies, spike-specific B cells and follicular helper T cells were found in vaccinated participants with chronic conditions (diabetes, renal disease) and were strongly associated with altered glycosylation of IgG and increased interleukin-18 levels in the plasma. These immune perturbations were also found in non-Indigenous people with comorbidities, indicating that they were related to comorbidities rather than ethnicity. However, our study is of a great importance to First Nations peoples who have disproportionate rates of chronic comorbidities and provides evidence of robust immune responses after COVID-19 vaccination in Indigenous people

Importance of NKT Cells in Resistance to Herpes Simplex Virus, Fate of Virus-Infected Neurons, and Level of Latency in Mice▿ †

Herpes simplex virus type 1 (HSV-1) produces acute mucocutaneous infections, spread to sensory ganglia, and establishment of latency. In addition, neurovirulent strains have potential to invade the central nervous system (CNS), with potentially a lethal outcome. Early activation of defenses at all stages is essential to limit virus load and reduce the risk of neuronal damage, extensive zosteriform skin lesions, and catastrophic spread to the CNS. NKT cells respond rapidly, and we have shown previously that CD1d-deficient mice are compromised in controlling a neuroinvasive isolate of HSV-1. We now compare infection in Jα18 GKO and CD1d GKO mice, allowing direct assessment of the importance of invariant Vα14+ NKT cells and deduction of the role of the CD1d-restricted NKT cells with diverse T-cell receptors. The results indicate that both subsets of NKT cells contribute to virus control both in the afferent phase of infection and in determining the mortality, neuroinvasion, loss of sensory neurons, size of zosteriform, lesions and levels of latency. In particular, both are crucial determinants of clinical outcome, providing protection equivalent to a 1-log dose of virus. These NKT cells can be expected to provide protection at doses of virus that might be encountered naturally

Emerging Targets for Developing T Cell-Mediated Vaccines for Human Immunodeficiency Virus (HIV)-1

Human immunodeficiency virus (HIV)-1 has infected >75 million individuals globally, and, according to the UN, is responsible for ~2.1 million new infections and 1.1 million deaths each year. Currently, there are ~37 million individuals with HIV infection and the epidemic has already resulted in 35 million deaths. Despite the advances of anti-retroviral therapy (ART), a cost-effective vaccine remains the best long-term solution to end the HIV-1 epidemic especially given that the vast majority of infected individuals live in poor socio-economic regions of the world such as Sub-Saharan Africa which limits their accessibility to ART. The modest efficacy of the RV144 Thai trial provides hope that a vaccine for HIV-1 is possible, but as markers for sterilizing immunity are unknown, the design of an effective vaccine is empirical, although broadly cross-reactive neutralizing antibodies (bNAb) that can neutralize various quasispecies of HIV-1 are considered crucial. Since HIV-1 transmission often occurs at the genito-rectal mucosa and is cell-associated, there is a need to develop vaccines that can elicit CD8+ T cell immunity with the capacity to kill virus infected cells at the genito-rectal mucosa and the gut. Here we discuss the recent progress made in developing T cell-mediated vaccines for HIV-1 and emphasize the need to elicit mucosal tissue-resident memory CD8+ T (CD8+ Trm) cells. CD8+ Trm cells will likely form a robust front-line defense against HIV-1 and eliminate transmitter/founder virus-infected cells which are responsible for propagating HIV-1 infections following transmission in vast majority of cases

Vaccination for pregnant women: Need to address

Pregnancy is a critically important state for any women in her life time. Administration of a vaccine to a pregnant woman is not a routine event and it is generally preferred to administer vaccines either prior to conception or in the postpartum period. Currently vaccination with inactivated vaccines are recommended due to potential risk to mother and fetus with live vaccines. Multiple factors determine the administration of the vaccines for example age, life style, medical conditions (e.g., asthma, diabetes etc.), type and location of travel and status of previous vaccination. If pregnant woman is exposed to these vaccines or if pregnancy occurs soon after vaccination, the women should be counselled regarding the risks to the fetus and vaccination should not be a reason to consider termination of pregnancy. Further research in vaccination among pregnancy is warranted for the safety of the pregnant women and their newborn for a healthy living and better life

Immunological memory in imiquimod-induced murine model of psoriasiform dermatitis

Psoriasis is a common chronic inflammatory skin condition manifested by T cell responses and characterized by preferential recurrence at previously inflamed sites upon withdrawal of treatment. The site-specific disease memory in psoriasis has been linked to CD8CD103 tissue-resident memory T cells (Trm) in the epidermis which were previously thought to only provide “frontline” protection against pathogens and immunosurveillance during cancer development. In this study, we correlated the presence of a subset of the Trm cells which are also CD49a with disease severity in human psoriatic lesions with acute and chronic disease. Using an imiquimod (IMQ)-induced murine model of psoriasiform dermatitis, we also investigated the level of CD49a Trm cells in acute, chronic and resolved psoriatic lesions. Investigation of clinical human samples showed that patient disease severity highly correlated with the numbers of epidermal CD49a Trm cells. Additionally, this subset of Trm cells was shown to persist in resolved lesions of murine psoriasiform dermatitis once clinical disease features had subsided. Importantly, these CD49a Trm cells showed significantly higher levels of granzyme B (GzmB) production compared to acute disease, suggesting a potential role of CD49a Trm cells for psoriatic re-occurrence in resolved patients. Better understanding of epidermal CD49a Trm cell activity is necessary for development of advanced treatment strategies for psoriasis to permit long-term, continuous disease control

Preclinical Development and Production of Virus-Like Particles As Vaccine Candidates for Hepatitis C

Hepatitis C Virus (HCV) infects 2% of the world's population and is the leading cause of liver disease and liver transplantation. It poses a serious and growing worldwide public health problem that will only be partially addressed with the introduction of new antiviral therapies. However, these treatments will not prevent re-infection particularly in high risk populations. The introduction of a HCV vaccine has been predicted, using simulation models in a high risk population, to have a significant effect on reducing the incidence of HCV. A vaccine with 50 to 80% efficacy targeted to high-risk intravenous drug users could dramatically reduce HCV incidence in this population. Virus like particles (VLPs) are composed of viral structural proteins which self-assemble into non-infectious particles that lack genetic material and resemble native viruses. Thus, VLPs represent a safe and highly immunogenic vaccine delivery platform able to induce potent adaptive immune responses. Currently, many VLP-based vaccines have entered clinical trials, while licensed VLP vaccines for hepatitis B virus (HBV) and human papilloma virus (HPV) have been in use for many years. The HCV core, E1 and E2 proteins can self-assemble into immunogenic VLPs while inclusion of HCV antigens into heterogenous (chimeric) VLPs is also a promising approach. These VLPs are produced using different expression systems such as bacterial, yeast, mammalian, plant, or insect cells. Here, this paper will review HCV VLP-based vaccines and their immunogenicity in animal models as well as the different expression systems used in their production

Cytolytic Perforin as an Adjuvant to Enhance the Immunogenicity of DNA Vaccines.

DNA vaccines present one of the most cost-effective platforms to develop global vaccines, which have been tested for nearly three decades in preclinical and clinical settings with some success in the clinic. However, one of the major challenges for the development of DNA vaccines is their poor immunogenicity in humans, which has led to refinements in DNA delivery, dosage in prime/boost regimens and the inclusion of adjuvants to enhance their immunogenicity. In this review, we focus on adjuvants that can enhance the immunogenicity of DNA encoded antigens and highlight the development of a novel cytolytic DNA platform encoding a truncated mouse perforin. The application of this innovative DNA technology has considerable potential in the development of effective vaccines

Induction of genotype cross-reactive, hepatitis C virus-specific, cellmediated immunity in DNA-vaccinated mice

A universal hepatitis C virus (HCV) vaccine should elicit multiantigenic, multigenotypic responses, which are more likely to protect against challenge with the range of genotypes and subtypes circulating in the community. A vaccine cocktail and vaccines encoding consensus HCV sequences are attractive approaches to achieve this goal. Consequently, in a series of mouse vaccination studies, we compared the immunogenicity of a DNA vaccine encoding a consensus HCV nonstructural 5B (NS5B) protein to that of a cocktail of DNA plasmids encoding the genotype 1b (Gt1b) and Gt3a NS5B proteins. To complement this study, we assessed responses to a multiantigenic cocktail regimen by comparing a DNA vaccine cocktail encoding Gt1b and Gt3a NS3, NS4, and NS5B proteins to a single-genotype NS3/4/5B DNA vaccine. To thoroughly evaluate in vivo cytotoxic T lymphocyte (CTL) and T helper (Th) cell responses against Gt1b and Gt3a HCV peptide-pulsed target cells, we exploited a novel fluorescent-target array (FTA). FTA and enzyme-linked immunosorbent spot (ELISpot) analyses collectively indicated that the cocktail regimens elicited higher responses to Gt1b and Gt3a NS5B proteins than those with the consensus vaccine, while the multiantigenic DNA cocktail significantly increased the responses to NS3 and NS5B compared to those elicited by the single-genotype vaccines. Thus, a DNA cocktail vaccination regimen is more effective than a consensus vaccine or a monovalent vaccine at increasing the breadth of multigenotypic T cell responses, which has implications for the development of vaccines for communities where multiple HCV genotypes circulate.This work was supported by grants from The Hospital Research Foundation (THRF), the Australian Centre for Hepatitis and HIV Virology (ACH2), and the Australia-India Biotechnology Fund. Danushka K. Wijesundara is an early career fellow supported by THRF