Alison Hogg

IL-1 enhances expansion, effector function, tissue localization, and memory response of antigen-specific CD8 T cells

Here, we show that interleukin-1 (IL-1) enhances antigen-driven CD8 T cell responses. When administered to recipients of OT-I T cell receptor transgenic CD8 T cells specific for an ovalbumin (OVA) peptide, IL-1 results in an increase in the numbers of wild-type but not IL1R1−/− OT-I cells, particularly in spleen, liver, and lung, upon immunization with OVA and lipopolysaccharide. IL-1 administration also results in an enhancement in the frequency of antigen-specific cells that are granzyme B+, have cytotoxic activity, and/ or produce interferon γ (IFN-γ). Cells primed in the presence of IL-1 display enhanced expression of granzyme B and increased capacity to produce IFN-γ when rechallenged 2 mo after priming. In three in vivo models, IL-1 enhances the protective value of weak immunogens. Thus, IL-1 has a marked enhancing effect on antigen-specific CD8 T cell expansion, differentiation, migration to the periphery, and memory.

Distinct Roles for MyD88 and Toll-Like Receptor 2 during Leishmania braziliensis Infection in Mice

ABSTRACT We have previously reported that Leishmania braziliensis infection can activate murine dendritic cells (DCs) and upregulate signaling pathways that are essential for the initiation of innate immunity. However, it remains unclear whether Toll-like receptors (TLRs) are involved in L. braziliensis-mediated DC activation. To address this issue, we generated bone marrow-derived DCs from MyD88−/− and TLR2−/− mice and examined their responsiveness to parasite infection. While wild-type DCs were efficiently activated to produce cytokines and prime naïve CD4+ T cells, L. braziliensis-infected MyD88−/− DCs exhibited less activation and decreased production of interleukin-12 (IL-12) p40. Furthermore, MyD88−/− mice were more susceptible to infection in that they developed larger and prolonged lesions compared to those in control mice. In sharp contrast, the lack of TLR2 resulted in an enhanced DC activation and increased IL-12 p40 production after infection. As such, L. braziliensis-infected TLR2−/− DCs were more competent in priming naïve CD4+ T cells in vitro than were their controls, findings which correlated with an increased gamma interferon production in vivo and enhanced resistance to infection. Our results suggest that while MyD88 is indispensable for the generation of protective immunity to L. braziliensis, TLR2 seems to have a regulatory role during infection.

Induction of granulysin in CD8+ T cells by IL-21 and IL-15 is suppressed by human immunodeficiency virus-1

Immunosuppression following infection with HIV‐1 predisposes patients to a myriad of opportunistic pathogens, one of the most important of which is Mtb. Granulysin, expressed by NK cells and CTL, exhibits potent antimicrobial activity against Mtb and several other opportunistic pathogens associated with HIV‐1 infection. The immune signals that promote granulysin expression in human CTL are not fully understood. Using primary human CD8+ T cells, in this study, we identify IL‐21 as a strong inducer of granulysin, demonstrate that IL‐21 and IL‐15 activate granulysin expression within CD8+ CD45RO+ T cells, and establish a role for Jak/STAT signaling in the regulation of granulysin within CD8+ T cells. We show that infection of PBMC from healthy donors in vitro with HIV‐1 suppresses granulysin expression by CD8+ T cells, concomitant with reduced p‐STAT3 and p‐STAT5, following activation with IL‐15 and IL‐21. Of note, simultaneous signaling through IL‐15 and IL‐21 could partially overcome the immunosuppressive effects of HIV‐1 on granulysin expression by CD8+ T cells. These results suggest that HIV‐1 infection of PBMC may reduce the antimicrobial profile of activated CD8+ T cells by disrupting signaling events that are critical for the induction of granulysin. Understanding the effects of HIV‐1 on CD8+ T cell activation is essential to understanding the physiological basis for inadequate cytotoxic lymphocyte activity in HIV+ patients and for informed guidance of cytokine‐based therapy to restore T cell function.

CXCL10 production by human monocytes in response to Leishmania braziliensis infection.

ABSTRACT Leishmania (subgenus Viannia) braziliensis is the causative agent of mucocutaneous leishmaniasis (ML) in South America, and ML is characterized by excessive T- and B-cell responses to the parasite. We speculate that the unbalanced production of inflammatory mediators in response to L. braziliensis infection contributes to cell recruitment and disease severity. To test this hypothesis, we first examined the response of peripheral blood mononuclear cells (PBMCs) from healthy volunteers to L. braziliensis infection. We observed that while L. braziliensis infection induced the production of chemokine (C-X-C motif) ligand 10 (CXCL10) and interleukin-10 (IL-10) in human PBMCs and macrophages (MΦs), enhanced expression of CXCL10 and its receptor, chemokine CXC receptor (CXCR3), was predominantly detected in CD14+ monocytes. The chemoattractant factors secreted by L. braziliensis-infected cells were highly efficient in recruiting uninfected PBMCs (predominantly CD14+ cells) through Transwell membranes. Serum samples from American tegumentary leishmaniasis (ATL) patients (especially the ML cases) had significantly higher levels of CXCL10, CCL4, and soluble tumor necrosis factor (TNF) receptor II (sTNFRII) than did those of control subjects. Our results suggest that, following L. braziliensis infection, the production of multiple inflammatory mediators by the host may contribute to disease severity by increasing cellular recruitment.

Vaccine-induced myeloid cell population dampens protective immunity to SIV

Vaccines are largely evaluated for their ability to promote adaptive immunity, with little focus on the induction of negative immune regulators. Adjuvants facilitate and enhance vaccine-induced immune responses and have been explored for mediating protection against HIV. Using a regimen of peptide priming followed by a modified vaccinia Ankara (MVA) boost in a nonhuman primate model, we found that an SIV vaccine incorporating molecular adjuvants mediated partial protection against rectal SIVmac251 challenges. Animals treated with vaccine and multiple adjuvants exhibited a reduced viral load (VL) compared with those treated with vaccine only. Surprisingly, animals treated with adjuvant alone had reduced VLs that were comparable to or better than those of the vaccine-treated group. VL reduction was greatest in animals with the MHC class I allele Mamu-A*01 that were treated with adjuvant only and was largely dependent on CD8+ T cells. Early VLs correlated with Ki67+CCR5+CD4+ T cell frequency, while set-point VL was associated with expansion of a myeloid cell population that was phenotypically similar to myeloid-derived suppressor cells (MDSCs) and that suppressed T cell responses in vitro. MDSC expansion occurred in animals receiving vaccine and was not observed in the adjuvant-only group. Collectively, these results indicate that vaccine-induced MDSCs inhibit protective cellular immunity and suggest that preventing MDSC induction may be critical for effective AIDS vaccination.

The calf model of immunity for development of a vaccine against tuberculosis.

Tuberculosis (TB) remains a major threat to public health. The identification of safe TB vaccine candidates beyond Mycobacterium bovis BCG, is an exciting prospect for control of human TB and necessary in the context of the human immunodeficiency virus (HIV) pandemic. Selection of vaccine candidates for human trials which are ultimately targeted for use in children less than 5 years of age or in newborns will require an animal model that closely approximates immune function and disease. We propose that the bovine neonate and adolescent is a robust animal model for preclinical safety and efficacy evaluation of TB candidate vaccines targeting this special human population. Parallel studies conducted in bovine neonates and non-human primates with a leading auxotrophic mutant with demonstrated efficacy/safety in a rodent TB model of TB demonstrated similar findings with respect to gross pathology scoring relative to BCG. The findings indicated more numerous and severe lesions in the lung in addition to higher levels of IFN-gamma producing cells. BCG vaccinates demonstrated higher levels of FoxP3 transcripts and lower levels of IL-4 mRNA.

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.

Comparative analysis of SIV-specific cellular immune responses induced by different vaccine platforms in rhesus macaques

To identify the most promising vaccine candidates for combinatorial strategies, we compared five SIV vaccine platforms including recombinant canary pox virus ALVAC, replication-competent adenovirus type 5 host range mutant RepAd, DNA, modified vaccinia Ankara (MVA), peptides and protein in distinct combinations. Three regimens used viral vectors (prime or boost) and two regimens used plasmid DNA. Analysis at necropsy showed that the DNA-based vaccine regimens elicited significantly higher cellular responses against Gag and Env than any of the other vaccine platforms. The T cell responses induced by most vaccine regimens disseminated systemically into secondary lymphoid tissues (lymph nodes, spleen) and effector anatomical sites (including liver, vaginal tissue), indicative of their role in viral containment at the portal of entry. The cellular and reported humoral immune response data suggest that combination of DNA and viral vectors elicits a balanced immunity with strong and durable responses able to disseminate into relevant mucosal sites.

Analysis of the Differential Host Cell Nuclear Proteome Induced by Attenuated and Virulent Hemorrhagic Arenavirus Infection

ABSTRACT Arenaviruses are important emerging pathogens and include a number of hemorrhagic fever viruses classified as NIAID category A priority pathogens and CDC potential biothreat agents. Infection of guinea pigs with the New World arenavirus Pichindé virus (PICV) has been used as a biosafety level 2 model for the Lassa virus. Despite continuing research, little is known about the molecular basis of pathogenesis, and this has hindered the design of novel antiviral therapeutics. Modulation of the host response is a potential strategy for the treatment of infectious diseases. We have previously investigated the global host response to attenuated and lethal arenavirus infections by using high-throughput immunoblotting and kinomics approaches. In this report, we describe the differential nuclear proteomes of a murine cell line induced by mock infection and infection with attenuated and lethal variants of PICV, investigated by using two-dimensional gel electrophoresis. Spot identification using tandem mass spectrometry revealed the involvement of a number of proteins that regulate inflammation via potential modulation of NF-κB activity and of several heterogeneous nuclear ribonuclear proteins. Pathway analysis revealed a potential role for transcription factor XBP-1, a transcription factor involved in major histocompatibility complex II (MHC-II) expression; differential DNA-binding activity was revealed by electrophoretic mobility shift assay, and differences in surface MHC-II expression were seen following PICV infection. These data are consistent with the results of several previous studies and highlight potential differences between transcriptional and translational regulation. This study provides a number of differentially expressed targets for further research and suggests that key events in pathogenesis may be established early in infection.

Humoral immunity induced by mucosal and/or systemic SIV-specific vaccine platforms suggests novel combinatorial approaches for enhancing responses.

Combinatorial HIV/SIV vaccine approaches targeting multiple arms of the immune system might improve protective efficacy. We compared SIV-specific humoral immunity induced in rhesus macaques by five vaccine regimens. Systemic regimens included ALVAC-SIVenv priming and Env boosting (ALVAC/Env); DNA immunization; and DNA plus Env co-immunization (DNA&Env). RepAd/Env combined mucosal replication-competent Ad-env priming with systemic Env boosting. A Peptide/Env regimen, given solely intrarectally, included HIV/SIV peptides followed by MVA-env and Env boosts. Serum antibodies mediating neutralizing, phagocytic and ADCC activities were induced by ALVAC/Env, RepAd/Env and DNA&Env vaccines. Memory B cells and plasma cells were maintained in the bone marrow. RepAd/Env vaccination induced early SIV-specific IgA in rectal secretions before Env boosting, although mucosal IgA and IgG responses were readily detected at necropsy in ALVAC/Env, RepAd/Env, DNA&Env and DNA vaccinated animals. Our results suggest that combined RepAd priming with ALVAC/Env or DNA&Env regimen boosting might induce potent, functional, long-lasting systemic and mucosal SIV-specific antibodies.