Amiran Dzutsev

Shared modes of protection against poxvirus infection by attenuated and conventional smallpox vaccine viruses

The concern about bioterrorism with smallpox has raised the possibility of widespread vaccination, but the greater prevalence of immunocompromised individuals today requires a safer vaccine, and the mechanisms of protection are not well understood. Here we show that, at sufficient doses, the protection provided by both modified vaccinia Ankara and NYVAC replication-deficient vaccinia viruses, safe in immunocompromised animals, was equivalent to that of the licensed Wyeth vaccine strain against a pathogenic vaccinia virus intranasal challenge of mice. A similar variety and pattern of immune responses were involved in protection induced by modified vaccinia Ankara and Wyeth viruses. For both, antibody was essential to protect against disease, whereas neither effector CD4+ nor CD8+ T cells were necessary or sufficient. However, in the absence of antibody, T cells were necessary and sufficient for survival and recovery. Also, T cells played a greater role in control of sublethal infection in unimmunized animals. These properties, shared with the existing smallpox vaccine, provide a basis for further evaluation of these replication-deficient vaccinia viruses as safer vaccines against smallpox or against complications from vaccinia virus.

Protection against Lethal Vaccinia Virus Challenge in HLA-A2 Transgenic Mice by Immunization with a Single CD8+ T-Cell Peptide Epitope of Vaccinia and Variola Viruses

ABSTRACT CD8+ T lymphocytes have been shown to be involved in controlling poxvirus infection, but no protective cytotoxic T-lymphocyte (CTL) epitopes are defined for variola virus, the causative agent of smallpox, or for vaccinia virus. Of several peptides in vaccinia virus predicted to bind HLA-A2.1, three, VETFsm(498-506), A26L(6-14), and HRP2(74-82), were found to bind HLA-A2.1. Splenocytes from HLA-A2.1 transgenic mice immunized with vaccinia virus responded only to HRP2(74-82) at 1 week and to all three epitopes by ex vivo enzyme-linked immunosorbent spot (ELISPOT) assay at 4 weeks postimmunization. To determine if these epitopes could elicit a protective CD8+ T-cell response, we challenged peptide-immunized HLA-A2.1 transgenic mice intranasally with a lethal dose of the WR strain of vaccinia virus. HRP2(74-82) peptide-immunized mice recovered from infection, while naïve mice died. Depletion of CD8+ T cells eliminated protection. Protection of HHD-2 mice, lacking mouse class I major histocompatibility complex molecules, implicates CTLs restricted by human HLA-A2.1 as mediators of protection. These results suggest that HRP2(74-82), which is shared between vaccinia and variola viruses, may be a CD8+ T-cell epitope of vaccinia virus that will provide cross-protection against smallpox in HLA-A2.1-positive individuals, representing almost half the population.

A Novel Functional CTL Avidity/Activity Compartmentalization to the Site of Mucosal Immunization Contributes to Protection of Macaques against Simian/Human Immunodeficiency Viral Depletion of Mucosal CD4+ T Cells

The presence of high-avidity CTLs in the right compartment can greatly affect clearance of a virus infection (for example, AIDS viral infection of and dissemination from mucosa). Comparing mucosal vs systemic immunization, we observed a novel compartmentalization of CTL avidity and proportion of functionally active Ag-specific CD8+ T cells to tissues proximal to sites of immunization. Whereas both s.c. and intrarectal routes of immunization induced tetramer+ cells in the spleen and gut, the mucosal vaccine induced a higher percentage of functioning IFN-γ+ Ag-specific CD8+ T cells in the gut mucosa in mice. Translating to the CD8+ CTL avidity distribution in rhesus macaques, intrarectal vaccination induced more high-avidity mucosal CTL than s.c. vaccination and protection of mucosal CD4+ T cells from AIDS viral depletion, whereas systemic immunization induced higher avidity IFN-γ-secreting cells in the draining lymph nodes but no protection of mucosal CD4+ T cells, after mucosal challenge with pathogenic simian/human immunodeficiency virus. Mucosal CD4+ T cell loss is an early critical step in AIDS pathogenesis. The preservation of CD4+ T cells in colonic lamina propria and the reduction of virus in the intestine correlated better with high-avidity mucosal CTL induced by the mucosal AIDS vaccine. This preferential localization of high-avidity CTL may explain previous differences in vaccination results and may guide future vaccination strategy.

Innate and adaptive immune correlates of vaccine and adjuvant-induced control of mucosal transmission of SIV in macaques

Adjuvant effects on innate as well as adaptive immunity may be critical for inducing protection against mucosal HIV and simian immunodeficiency virus (SIV) exposure. We therefore studied effects of Toll-like receptor agonists and IL-15 as mucosal adjuvants on both innate and adaptive immunity in a peptide/poxvirus HIV/SIV mucosal vaccine in macaques, and made three critical observations regarding both innate and adaptive correlates of protection: (i) adjuvant-alone without vaccine antigen impacted the intrarectal SIVmac251 challenge outcome, correlating with surprisingly long-lived APOBEC3G (A3G)-mediated innate immunity; in addition, even among animals receiving vaccine with adjuvants, viral load correlated inversely with A3G levels; (ii) a surprising threshold-like effect existed for vaccine-induced adaptive immunity control of viral load, and only antigen-specific polyfunctional CD8+ T cells correlated with protection, not tetramer+ T cells, demonstrating the importance of T-cell quality; (iii) synergy was observed between Toll-like receptor agonists and IL-15 for driving adaptive responses through the up-regulation of IL-15Rα, which can present IL-15 in trans, as well as for driving the innate A3G response. Thus, strategic use of molecular adjuvants can provide better mucosal protection through induction of both innate and adaptive immunity.

Enhancement of CD8+ T Cell Immunity in the Lung by CpG Oligodeoxynucleotides Increases Protective Efficacy of a Modified Vaccinia Ankara Vaccine against Lethal Poxvirus Infection Even in a CD4-Deficient Host

Immunostimulatory CpG oligodeoxynucleotides (ODN) have proven effective as adjuvants for protein-based vaccines, but their impact on immune responses induced by live viral vectors is not known. We found that addition of CpG ODN to modified vaccinia Ankara (MVA) markedly improved the induction of longer-lasting adaptive protective immunity in BALB/c mice against intranasal pathogenic vaccinia virus (Western Reserve; WR). Protection was mediated primarily by CD8+ T cells in the lung, as determined by CD8-depletion studies, protection in B cell-deficient mice, and greater protection correlating with CD8+ IFN-γ-producing cells in the lung but not with those in the spleen. Intranasal immunization was more effective at inducing CD8+ T cell immunity in the lung, and protection, than i.m. immunization. Addition of CpG ODN increased the CD8+ response but not the Ab response. Depletion of CD4 T cells before vaccination with MVA significantly diminished protection against pathogenic WR virus. However, CpG ODN delivered with MVA was able to substitute for CD4 help and protected CD4-depleted mice against WR vaccinia challenge. This study demonstrates for the first time a protective adjuvant effect of CpG ODN for a live viral vector vaccine that may overcome CD4 deficiency in the induction of protective CD8+ T cell-mediated immunity.

Cell Depletion in Mice That Express Diphtheria Toxin Receptor under the Control of SiglecH Encompasses More Than Plasmacytoid Dendritic Cells

Plasmacytoid dendritic cells (pDC) produce IFN-I in response to viruses and are routinely identified in mice by SiglecH expression. SiglecH is a sialic acid–binding Ig-like lectin that has an immunomodulatory role during viral infections. In this study, we evaluated the impact of SiglecH deficiency on cytokine responses in the presence and absence of pDC. We found that lack of SiglecH enhanced IFN-I responses to viral infection, regardless of whether pDC were depleted. We also examined the expression pattern of SiglecH and observed that it was expressed by specialized macrophages and progenitors of classical dendritic cells and pDC. Accordingly, marginal zone macrophages and pDC precursors were eliminated in newly generated SiglecH–diphtheria toxin receptor (DTR)–transgenic (Tg) mice but not in CLEC4C-DTR–Tg mice after diphtheria toxin (DT) treatment. Using two bacterial models, we found that SiglecH-DTR–Tg mice injected with DT had altered bacterial uptake and were more susceptible to lethal Listeria monocytogenes infection than were DT-treated CLEC4C-DTR–Tg mice. Taken together, our findings suggest that lack of SiglecH may affect cytokine responses by cell types other than pDC during viral infections, perhaps by altering viral distribution or burden, and that cell depletion in SiglecH-DTR–Tg mice encompasses more than pDC.

Microbes and Cancer

Commensal microorganisms (the microbiota) live on all the surface barriers of our body and are particularly abundant and diverse in the distal gut. The microbiota and its larger host represent a metaorganism in which the cross talk between microbes and host cells is necessary for health, survival, and regulation of physiological functions locally, at the barrier level, and systemically. The ancestral molecular and cellular mechanisms stemming from the earliest interactions between prokaryotes and eukaryotes have evolved to mediate microbe-dependent host physiology and tissue homeostasis, including innate and adaptive resistance to infections and tissue repair. Mostly because of its effects on metabolism, cellular proliferation, inflammation, and immunity, the microbiota regulates cancer at the level of predisposing conditions, initiation, genetic instability, susceptibility to host immune response, progression, comorbidity, and response to therapy. Here, we review the mechanisms underlying the interaction of the microbiota with cancer and the evidence suggesting that the microbiota could be targeted to improve therapy while attenuating adverse reactions.

White Adipose Tissue Is a Reservoir for Memory T Cells and Promotes Protective Memory Responses to Infection

Summary White adipose tissue bridges body organs and plays a fundamental role in host metabolism. To what extent adipose tissue also contributes to immune surveillance and long‐term protective defense remains largely unknown. Here, we have shown that at steady state, white adipose tissue contained abundant memory lymphocyte populations. After infection, white adipose tissue accumulated large numbers of pathogen‐specific memory T cells, including tissue‐resident cells. Memory T cells in white adipose tissue expressed a distinct metabolic profile, and white adipose tissue from previously infected mice was sufficient to protect uninfected mice from lethal pathogen challenge. Induction of recall responses within white adipose tissue was associated with the collapse of lipid metabolism in favor of antimicrobial responses. Our results suggest that white adipose tissue represents a memory T cell reservoir that provides potent and rapid effector memory responses, positioning this compartment as a potential major contributor to immunological memory. Graphical Abstract Figure. No caption available. HighlightsWhite adipose tissue serves as a reservoir for memory T cellsWhite adipose tissue memory T cells have a distinct functional and metabolic profileMemory T cells from white adipose tissue can protect against lethal infectious challengeReactivation of white adipose tissue memory T cells alters adipose tissue physiology &NA; The role of adipose tissue in protective immunity is largely unknown. Han et al. reveal that white adipose tissue is a reservoir for memory T cells endowed with a distinct functional and metabolic profile. These memory T cells are able to protect against infection while inducing physiological remodeling of adipose tissue.

TLR agonists and/or IL-15 adjuvanted mucosal SIV-vaccine reduced gut CD4+ memory T cell loss in SIVmac251-challenged rhesus macaques

Adjuvant plays an important role in increasing and directing vaccine-induced immune responses. In a previous study, we found that a mucosal SIV vaccine using a combination of IL-15 and TLR agonists as adjuvant mediated partial protection against SIVmac251 rectal challenge, whereas neither IL-15 nor TLR agonists alone as an adjuvant impacted the plasma viral loads. In this study, dissociation of CD4(+) T cell preservation with viral loads was observed in the animals vaccinated with adjuvants. Significantly higher levels of memory CD4(+) T cell numbers were preserved after SIVmac251 infection in the colons of the animals vaccinated with vaccine containing any of these adjuvants compared to no adjuvant. When we measured the viral-specific CD8(+) tetramer responses in the colon lamina propria, we found significantly higher levels of gag, tat, and pol epitope tetramer(+) T cell responses in these animals compared to ones without adjuvant, even if some of the animals had similarly high viral loads. Furthermore, this CD4(+) T preservation was positively correlated with increased levels of gag and Tat, but not pol tetramer(+) T cell responses, and inversely correlated with beta-chemokine expression. The pre-challenged APOBEC3G expression level, which has previously been shown inversely associated with viral loads, was further found positively correlated with CD4(+) T cell number preservation. Overall, these data highlight one unrecognized role of adjuvant in HIV vaccine development, and show that vaccines can produce a surprising discordance between CD4(+) T cell levels and SIV viral load.

IL-15 ex vivo overcomes CD4+ T cell deficiency for the induction of human antigen-specific CD8+ T cell responses

CD4+ Th cells are important for the induction and maintenance of antigen‐specific CD8+ T cell function, so their loss or dysfunction in HIV‐infected or cancer patients could reduce the patientsˈ ability to control viral infection. Previous work in murine systems indicated that IL‐15 codelivered with vaccines could overcome CD4+ Th cell deficiency for induction of functionally efficient CD8+ T cells and maintenance of viral‐specific CTLs, but its efficacy in helping primary human CD8+ T cell responses is unknown. In the present study, a peptide‐pulsed, DC‐based human coculture ex vivo system was used to study the role of IL‐15 in overcoming CD4+ Th deficiency to elicit CD8+ T cell responses in CD4‐depleted PBMCs from healthy individuals and PBMCs from HIV‐1‐infected patients. We found that IL‐15 could overcome CD4+ Th deficiency to induce primary and recall memory CD8+ T cell responses in healthy individuals. Moreover, in CD4‐deficient, HIV‐1‐infected patients with diminished CD8+ T cell responses, IL‐15 greatly enhanced CD8+ T cell responses to alloantigen. These results suggest that IL‐15 may be useful in the development of therapeutic and preventive vaccines against cancers and viral infections in patients defective in CD4+ Th cell.