OX40 ligation of CD4+ T cells enhances virus-specific CD8+ T cell memory responses independently of IL-2 and CD4+ T regulatory cell inhibition

Impaired tolerance to the autoantigen LL-37 in acute coronary syndrome

Background

LL-37 is the only member of the cathelicidin family of antimicrobial peptides in humans and is an autoantigen in several autoimmune diseases and in acute coronary syndrome (ACS). In this report, we profiled the specific T cell response to the autoimmune self-antigen LL-37 and investigated the factors modulating the response in peripheral blood mononuclear cells (PBMCs) of healthy subjects and ACS patients.

Methods and results

The activation induced marker (AIM) assay demonstrated differential T cell profiles characterized by the persistence of CD134 and CD137, markers that impair tolerance and promote immune effector and memory response, in ACS compared to Controls. Specifically, CD8+CD69+CD137+ T cells were significantly increased by LL-37 stimulation in ACS PBMCs. T effector cell response to LL-37 were either HLA dependent or independent as determined by blocking with monoclonal antibody to either Class-I HLA or Class-II HLA. Blocking of immune checkpoints PD-1 and CTLA-4 demonstrated the control of self-reactive T cell response to LL-37 was modulated predominantly by CTLA-4. Platelets from healthy controls down-modulated CD8+CD69+CD137+ T cell response to LL-37 in autologous PBMCs. CD8+CD69+CD137+ T cell AIM profile negatively correlated with platelet count in ACS patients.

Conclusions

Our report demonstrates that the immune response to the autoantigen LL-37 in ACS patients is characterized specifically by CD8+CD69+CD137+ T cell AIM profile with persistent T cell activation and the generation of immunologic memory. The results provide potentially novel insight into mechanistic pathways of antigen-specific immune signaling in ACS.

Quantitative contributions of TNF receptor superfamily members to CD8+ T-cell responses

T-cell responses to infections and cancers are regulated by co-signalling receptors grouped into the binary categories of co-stimulation or co-inhibition. The co-stimulation TNF receptor superfamily (TNFRSF) members 4-1BB, CD27, GITR and OX40 have similar signalling mechanisms raising the question of whether they have similar impacts on T-cell responses. Here, we screened for the quantitative impact of these TNFRSFs on primary human CD8+ T-cell cytokine production. Although both 4-1BB and CD27 increased production, only 4-1BB was able to prolong the duration over which cytokine was produced, and both had only modest effects on antigen sensitivity. An operational model explained these different phenotypes using shared signalling based on the surface expression of 4-1BB being regulated through signalling feedback. The model predicted and experiments confirmed that CD27 co-stimulation increases 4-1BB expression and subsequent 4-1BB co-stimulation. GITR and OX40 displayed only minor effects on their own but, like 4-1BB, CD27 could enhance GITR expression and subsequent GITR co-stimulation. Thus, different co-stimulation receptors can have different quantitative effects allowing for synergy and fine-tuning of T-cell responses.

Resiquimod-Mediated Activation of Plasmacytoid Dendritic Cells Is Amplified in Multiple Sclerosis

Background: Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease of the central nervous system. The cause of multiple sclerosis is unknown but there are several evidences that associate the genetic basis of the disease with environmental causes. An important association between viral infection and development of MS is clearly demonstrated. Viruses have a strong impact on innate immune cells. In particular, myeloid dendritic cells (mDCs) and plasmacytoid dendritic cells (pDCs), are able to respond to viruses and to activate the adaptive immune response. Methods: In this study we mimic viral infection using synthetic single-strand RNA, Resiquimod, and we compared the response of both DC subsets derived from healthy donors and MS patients by characterizing the expression of costimulatory molecules on the DC surface. Results: We found that pDCs from MS patients express higher levels of OX40-L, HLA-DR, and CD86 than healthy donors. Moreover, we found that blood cells from MS patients and healthy donors upon Resiquimod-stimulation are enriched in a subpopulation of pDCs, characterized by a high amount of costimulatory molecules. Conclusion: Overall, these results indicate that activation of pDCs is enhanced in MS, likely due to a latent viral infection, and that costimulatory molecules expressed on pDCs could mediate a protective response against the viral trigger of autoimmunity.

Costimulatory and Coinhibitory Receptor Pathways in Infectious Disease

Costimulatory and inhibitory receptors play a key role in regulating immune responses to infections. Recent translation of knowledge about inhibitory receptors such as CTLA-4 and PD-1 into the cancer clinic highlights the opportunities to manipulate these pathways to treat human disease. Studies in infectious disease have provided key insights into the specific roles of these pathways and the effects of their manipulation. Here, recent studies are discussed that have addressed how major inhibitory and costimulatory pathways play a role in regulating immune responses during acute and chronic infections. Mechanistic insights from studies of infectious disease provide opportunities to further expand our toolkit to treat cancer and chronic infections in the clinic.

Oncolytic VSV Primes Differential Responses to Immuno-oncology Therapy

Vesicular stomatitis virus encoding the IFNβ transgene (VSV-IFNβ) is a mediator of potent oncolytic activity and is undergoing clinical evaluation for the treatment of solid tumors. Emerging preclinical and clinical data suggest treatment of tumors with oncolytic viruses may sensitize tumors to checkpoint inhibitors and increase the anti-tumor immune response. New generations of immuno-oncology molecules including T cell agonists are entering clinical development and could be hypothesized to enhance the activity of oncolytic viruses, including VSV-IFNβ. Here, we show that VSV-IFNβ exhibits multiple mechanisms of action, including direct cell killing, stimulation of an innate immune response, recruitment of CD8 T cells, and depletion of T regulatory cells. Moreover, VSV-IFNβ promotes the establishment of a CD8 T cell response to endogenous tumor antigens. Our data demonstrate a significant enhancement of anti-tumor function for VSV-IFNβ when combined with checkpoint inhibitors, but not OX40 agonists. While the addition of checkpoint inhibitors to VSV-IFNβ generated robust tumor growth inhibition, it resulted in no increase in viral replication, transgene expression, or immunophenotypic changes beyond treatment with VSV-IFNβ alone. We hypothesize that tumor-specific T cells generated by VSV-IFNβ retain activity due to a lack of immune exhaustion when checkpoint inhibitors were used.

TNFRs and Control of Chronic LCMV Infection: Implications for Therapy

The control of persistent viral infections requires the immune system to limit the spread of the virus while avoiding immunopathology. Recent studies have revealed that members of the tumor necrosis factor receptor (TNFR) superfamily play unique and pivotal roles in control of chronic lymphocytic choriomeningitis virus (LCMV) infection and in some settings can tip the balance between immune control and immune pathology. We review these findings and discuss how our understanding of the role of TNFRs in the immune response to chronic LCMV infection may shed light on what happens during HIV infection in humans. We discuss preclinical models of TNF/TNFR family-targeted immunotherapy of chronic LCMV infection and evaluate which TNFRs present the most promising targets for immune intervention.

TB-IRIS, T-cell activation, and remodeling of the T-cell compartment in highly immunosuppressed HIV-infected patients with TB

OBJECTIVE

To investigate the impact of tuberculosis-associated immune reconstitution inflammatory syndrome (TB-IRIS) upon immunological recovery and the T-cell compartment after initiation of TB and antiretroviral therapy (ART).

DESIGN AND METHODS

We prospectively evaluated T-cell immunophenotypes by flow cytometry and cytokines by Luminex assays in a subset (n = 154) of highly immunosuppressed HIV-infected patients with TB from the Cambodian Early versus Late Introduction of Antiretrovirals randomized clinical trial. We compared findings from patients who developed TB-IRIS with findings from patients who did not develop TB-IRIS. Data were evaluated with mixed-effect linear regression, Kaplan-Meier estimates, and Wilcoxon rank-sum tests, and q-values were calculated to control for multiple comparisons.

RESULTS

Development of TB-IRIS was associated with significantly greater pre-ART frequencies of HLA-DRCD45ROCD4, CCR5CD4, OX40CD4, and Fas effector memory CD8 T cells, and significantly elevated levels of plasma interleukin (IL)-6, IL-1β, IL-8, and IL-10, and viral load. Post-ART initiation, effector memory CD4 and Fas effector memory CD4 T-cell frequencies significantly expanded, and central memory CD4 T-cell frequencies significantly contracted in patients who experienced TB-IRIS. By week 34 post-TB treatment initiation, effector memory/central memory CD4 T-cell ratios were markedly higher in TB-IRIS versus non-TB-IRIS patients.

CONCLUSIONS

A distinct pattern of pre-ART T-cell and cytokine markers appear to poise the immune response of certain patients to develop TB-IRIS. Experience of TB-IRIS is then associated with long-term remodeling of the CD4 T-cell memory compartment towards an effector memory-dominated phenotype. We speculate that these pre and post-ART TB-IRIS-associated immune parameters may contribute to superior immune control of TB/HIV co-infection and better clinical outcome.

TNF and TNF receptor superfamily members in HIV infection: new cellular targets for therapy?

Tumor necrosis factor (TNF) and TNF receptors (TNFR) superfamily members are engaged in diverse cellular phenomena such as cellular proliferation, morphogenesis, apoptosis, inflammation, and immune regulation. Their role in regulating viral infections has been well documented. Viruses have evolved with numerous strategies to interfere with TNF-mediated signaling indicating the importance of TNF and TNFR superfamily in viral pathogenesis. Recent research reports suggest that TNF and TNFRs play an important role in the pathogenesis of HIV. TNFR signaling modulates HIV replication and HIV proteins interfere with TNF/TNFR pathways. Since immune activation and inflammation are the hallmark of HIV infection, the use of TNF inhibitors can have significant impact on HIV disease progression. In this review, we will describe how HIV infection is modulated by signaling mediated through members of TNF and TNFR superfamily and in turn how these latter could be targeted by HIV proteins. Finally, we will discuss the emerging therapeutics options based on modulation of TNF activity that could ultimately lead to the cure of HIV-infected patients.

Upregulation of OX40 ligand on monocytes contributes to early virological control in patients with chronic hepatitis C

Dysfunctional hepatitis C virus (HCV) specific CD4(+) T cells are known to contribute to inadequate adaptive immunity in chronic hepatitis C (CHC), although the underlying mechanisms remain largely undefined. In this study, OX40 ligand (OX40L) expression was investigated in 41 treatment-naïve CHC patients, 20 sustained virological responders and 36 healthy subjects. We observed that OX40L expression was significantly upregulated in peripheral monocytes in CHC patients compared with sustained virological responders and healthy subjects. OX40L upregulation correlated significantly with plasma viral load rather than serum alanine aminotransaminase levels. Furthermore, longitudinal analyses indicated that upregulated OX40L expression on monocytes is closely associated with rapid or early virological responses in patients receiving pegylated IFN-α/ribavirin treatment. In vitro, HCV core antigen strongly stimulated monocyte expression of OX40L and blockade of TLR2 signaling significantly downregulated OX40L expression. More importantly, elevated OX40L expression was also shown to be closely associated with elevation of the HCV-specific CD4(+) T-cell response and in vitro blockade of OX40L expressed on monocytes led to impaired CD4(+) T-cell function. These findings, therefore, implicate OX40L expression can be used as a marker to evaluate antiviral treatment efficacy and extend the notion that enhancement of OX40L expression could be a good way for immunotherapy in CHC patients.

Association of Neisseria gonorrhoeae Opa(CEA) with dendritic cells suppresses their ability to elicit an HIV-1-specific T cell memory response

Infection with Neisseria gonorrhoeae (N. gonorrhoeae) can trigger an intense local inflammatory response at the site of infection, yet there is little specific immune response or development of immune memory. Gonococcal surface epitopes are known to undergo antigenic variation; however, this is unlikely to explain the weak immune response to infection since individuals can be re-infected by the same serotype. Previous studies have demonstrated that the colony opacity-associated (Opa) proteins on the N. gonorrhoeae surface can bind human carcinoembryonic antigen-related cellular adhesion molecule 1 (CEACAM1) on CD4⁺ T cells to suppress T cell activation and proliferation. Interesting in this regard, N. gonorrhoeae infection is associated with impaired HIV-1 (human immunodeficiency virus type 1)-specific cytotoxic T-lymphocyte (CTL) responses and with transient increases in plasma viremia in HIV-1-infected patients, suggesting that N. gonorrhoeae may also subvert immune responses to co-pathogens. Since dendritic cells (DCs) are professional antigen presenting cells (APCs) that play a key role in the induction of an adaptive immune response, we investigated the effects of N. gonorrhoeae Opa proteins on human DC activation and function. While morphological changes reminiscent of DC maturation were evident upon N. gonorrhoeae infection, we observed a marked downregulation of DC maturation marker CD83 when the gonococci expressing CEACAM1-specific Opa(CEA), but not other Opa variants. Consistent with a gonococcal-induced defect in maturation, Opa(CEA) binding to CEACAM1 reduced the DCs' capacity to stimulate an allogeneic T cell proliferative response. Moreover, Opa(CEA)-expressing N. gonorrhoeae showed the potential to impair DC-dependent development of specific adaptive immunity, since infection with Opa(CEA)-positive gonococci suppressed the ability of DCs to stimulate HIV-1-specific memory CTL responses. These results reveal a novel mechanism to explain why infection of N. gonorrhoeae fails to trigger an effective specific immune response or develop immune memory, and may affect the potent synergy between gonorrhea and HIV-1 infection.

Soluble multi-trimeric TNF superfamily ligand adjuvants enhance immune responses to a HIV-1 Gag DNA vaccine

BACKGROUND

DNA vaccines remain an important component of HIV vaccination strategies, typically as part of a prime/boost vaccination strategy with viral vector or protein boost. A number of DNA prime/viral vector boost vaccines are currently being evaluated for both preclinical studies and in Phase I and Phase II clinical trials. These vaccines would benefit from molecular adjuvants that increase correlates of immunity during the DNA prime. While HIV vaccine immune correlates are still not well defined, there are a number of immune assays that have been shown to correlate with protection from viral challenge including CD8+ T cell avidity, antigen-specific proliferation, and polyfunctional cytokine secretion.

METHODOLOGY AND PRINCIPAL FINDINGS

Recombinant DNA vaccine adjuvants composed of a fusion between Surfactant Protein D (SP-D) and either CD40 Ligand (CD40L) or GITR Ligand (GITRL) were previously shown to enhance HIV-1 Gag DNA vaccines. Here we show that similar fusion constructs composed of the TNF superfamily ligands (TNFSFL) 4-1BBL, OX40L, RANKL, LIGHT, CD70, and BAFF can also enhanced immune responses to a HIV-1 Gag DNA vaccine. BALB/c mice were vaccinated intramuscularly with plasmids expressing secreted Gag and SP-D-TNFSFL fusions. Initially, mice were analyzed 2 weeks or 7 weeks following vaccination to evaluate the relative efficacy of each SP-D-TNFSFL construct. All SP-D-TNFSFL constructs enhanced at least one Gag-specific immune response compared to the parent vaccine. Importantly, the constructs SP-D-4-1BBL, SP-D-OX40L, and SP-D-LIGHT enhanced CD8+ T cell avidity and CD8+/CD4+ T cell proliferation 7 weeks post vaccination. These avidity and proliferation data suggest that 4-1BBL, OX40L, and LIGHT fusion constructs may be particularly effective as vaccine adjuvants. Constructs SP-D-OX40L, SP-D-LIGHT, and SP-D-BAFF enhanced Gag-specific IL-2 secretion in memory T cells, suggesting these adjuvants can increase the number of self-renewing Gag-specific CD8+ and/or CD4+ T cells. Finally adjuvants SP-D-OX40L and SP-D-CD70 increased T(H)1 (IgG2a) but not T(H)2 (IgG1) antibody responses in the vaccinated animals. Surprisingly, the B cell-activating protein BAFF did not enhance anti-Gag antibody responses when given as an SP-D fusion adjuvant, but nonetheless enhanced CD4+ and CD8+ T cell responses.

CONCLUSIONS

We present evidence that various SP-D-TNFSFL fusion constructs can enhance immune responses following DNA vaccination with HIV-1 Gag expression plasmid. These data support the continued evaluation of SP-D-TNFSFL fusion proteins as molecular adjuvants for DNA and/or viral vector vaccines. Constructs of particular interest included SP-D-OX40L, SP-D-4-1BBL, SP-D-LIGHT, and SP-D-CD70. SP-D-BAFF was surprisingly effective at enhancing T cell responses, despite its inability to enhance anti-Gag antibody secretion.

Targeting OX40 promotes lung-resident memory CD8 T cell populations that protect against respiratory poxvirus infection

One goal of vaccination is to promote development of mucosal effector cells that can immediately respond to peripheral infection. This is especially important for protection against viruses that enter the host through the respiratory tract. We show that targeting the OX40 costimulatory receptor (CD134) strongly promotes mucosal memory in the CD8 T cell compartment. Systemic injection of an agonist antibody to OX40 strongly enhanced development of polyfunctional effector CD8 T cells that were induced after intraperitoneal infection with a highly virulent strain of vaccinia virus. These cells were located in lymphoid organs and also the lung, and importantly, long-term memory CD8 T cells were maintained in the lung over 1 year. Anti-OX40 also boosted memory development when mice were vaccinated subcutaneously with viral peptide. These CD8 T cells were sufficient to provide protection from lethal respiratory infection with live vaccinia virus independent of CD4 T cells and antibody. Again, the CD8 T cell populations that were induced after secondary infection displayed polyfunctionality and were maintained in the lung for over a year. These data suggest that agonists to the OX40 costimulatory receptor represent potential candidates for incorporation into vaccines for respiratory viruses.

Surface expression patterns of negative regulatory molecules identify determinants of virus-specific CD8+ T-cell exhaustion in HIV infection

A highly complex network of coinhibitory and costimulatory receptors regulates the outcome of virus-specific CD8(+) T-cell responses. Here, we report on the expression patterns of multiple inhibitory receptors on HIV-specific, cytomegalovirus-specific, and bulk CD8(+) T-cell memory populations. In contrast to cytomegalovirus-specific CD8(+) T cells, the majority of HIV-specific CD8(+) T cells exhibited an immature phenotype and expressed Programmed Death-1, CD160 and 2B4 but not lymphocyte activation gene-3. Notably, before antiretroviral therapy, simultaneous expression of these negative regulators correlated strongly with both HIV load and impaired cytokine production. Suppression of HIV replication by antiretroviral therapy was associated with reduced surface expression of inhibitory molecules on HIV-specific CD8(+) T cells. Furthermore, in vitro manipulation of Programmed Death-1 and 2B4 inhibitory pathways increased the proliferative capacity of HIV-specific CD8(+) T cells. Thus, multiple coinhibitory receptors can affect the development of HIV-specific CD8(+) T-cell responses and, by extension, represent potential targets for new immune-based interventions in HIV-infected persons.

Signaling through OX40 enhances antitumor immunity

The existence of tumor-specific T cells, as well as their ability to be primed in cancer patients, confirms that the immune response can be deployed to combat cancer. However, there are obstacles that must be overcome to convert the ineffective immune response commonly found in the tumor environment to one that leads to sustained destruction of tumor. Members of the tumor necrosis factor (TNF) superfamily direct diverse immune functions. OX40 and its ligand, OX40L, are key TNF members that augment T-cell expansion, cytokine production, and survival. OX40 signaling also controls regulatory T-cell differentiation and suppressive function. Studies over the past decade have demonstrated that OX40 agonists enhance antitumor immunity in preclinical models using immunogenic tumors; however, treatment of poorly immunogenic tumors has been less successful. Combining strategies that prime tumor-specific T cells together with OX40 signaling could generate and maintain a therapeutic antitumor immune response.

Suppression of CCR5-tropic HIV type 1 infection by OX40 stimulation via enhanced production of β-chemokines

To elucidate the immunological role for the costimulatory molecule OX40 against the early stage of HIV-1 infection, fresh peripheral blood mononuclear cells (PBMCs) from normal donors were stimulated with immobilized anti-CD3 monoclonal antibody (mAb) together with soluble anti-CD28 mAb for 24 h, infected with CCR5-tropic (R5) HIV-1, and then cocultured in the presence or absence of OX40 ligand (OX40L). Results of these studied showed that OX40 stimulation led to a marked reduction in levels of p24, the frequency of intracellular p24(+) cells, as well as HIV-1-mediated syncytium formation. The suppression was reversed by anti-OX40L mAb. The mechanism underlying the R5 HIV-1 suppression was shown to be mediated in part by the CCR5-binding β-chemokines RANTES, MIP-1α, and MIP-1β, since the effect of the OX40 stimulation was reversed by a neutralizing antibody mixture against these three β-chemokines. Thus, OX40 stimulation enhanced the production of these CCR5-binding β-chemokines by the activated PBMCs and subsequently down-modulated CCR5 expression on the activated CD4(+) T cells. Taken together, the present data revealed a new role for OX40 in HIV-1 infection and documents the fact that OX40 stimulation suppresses the infection of primary activated PBMCs with R5 HIV-1 via enhanced production of R5 HIV-1 suppressing β-chemokines.

Tumor necrosis factor receptor/tumor necrosis factor family members in antiviral CD8 T-cell immunity

CD8 memory T cells can play a critical role in protection against repeated exposure to infectious agents such as viruses, yet can also contribute to the immunopathology associated with these pathogens. Understanding the mechanisms that control effective memory responses has important ramifications for vaccine design and in the management of adverse immune reactions. Recent studies have implicated several members of the tumor necrosis factor receptor (TNFR) family as key stimulatory and inhibitory molecules involved in the regulation of CD8 T cells. In this review, we discuss their control of the generation, persistence, and reactivation of CD8 T cells during virus infection.

Control of immunity by the TNFR-related molecule OX40 (CD134)

TNFR/TNF superfamily members can control diverse aspects of immune function. Research over the past 10 years has shown that one of the most important and prominent interactions in this family is that between OX40 (CD134) and its partner OX40L (CD252). These molecules strongly regulate conventional CD4 and CD8 T cells, and more recent data are highlighting their ability to modulate NKT cell and NK cell function as well as to mediate cross-talk with professional antigen-presenting cells and diverse cell types such as mast cells, smooth muscle cells, and endothelial cells. Additionally, OX40-OX40L interactions alter the differentiation and activity of regulatory T cells. Blocking OX40L has produced strong therapeutic effects in multiple animal models of autoimmune and inflammatory disease, and, in line with a prospective clinical future, reagents that stimulate OX40 signaling are showing promise as adjuvants for vaccination as well as for treatment of cancer.

IL-7, but not thymic stromal lymphopoietin (TSLP), during priming enhances the generation of memory CD4+ T cells

Multiple activation signals (including antigen, co-stimulation, and cytokines) during T-cell priming affect the subsequent generation of memory T cells, whose survival is maintained by IL-7 and IL-15. Since the IL-7 receptor is highly expressed not only on the surface of memory T cells but also on naïve T cells, we propose that early exposure to IL-7 during priming of naïve T cells may promote their survival, and thus enhances the generation of memory cells. To test this hypothesis, TCR transgenic OT-II CD4(+) T cells were stimulated in vitro with OVA(323-339) peptide presented by syngeneic antigen-presenting cells (APCs). IL-7 or an IL-7 like cytokine, thymic stromal lymphopoietin (TSLP), was added at the initial 2-day cultivation stage. We found that a short exposure to IL-7 or TSLP during priming did not affect activation, proliferation, and glucose uptake by CD4(+) T cells compared to controls when examined on culture day 6. However, the same 6-day cultures showed that IL-7 (but not TSLP) significantly decreased the frequency of apoptotic CD4(+) T cells compared to controls. More importantly, an adoptive transfer of the 6-day primed OT-II T cells into CD45.1(+) congenic mice demonstrated that IL-7 (but not TSLP) elevated by 3- and 4-fold the number of transferred CD4(+) T cells in spleen (p<0.05) and lymph nodes (p<0.05), respectively, compared to controls. Almost all transferred CD4(+) T populations displayed phenotypes of effector (CD44(+)CD62L(-)) or central (CD44(+)CD62L(+)) memory T cells. We thus conclude that exposure of CD4(+) T cells to IL-7 during priming results in an increased frequency of CD4(+) memory T cells.

The adjuvancy of OX40 ligand (CD252) on an HIV-1 canarypox vaccine

The immunogenicity of current human immunodeficiency virus-1 (HIV-1) canarypox vaccines is weak and needs to be improved. Ligation of OX40 (CD134), a member of tumor necrosis factor receptor superfamily (TNFRSF), by its ligand OX40L (CD252), a tumor necrosis factor superfamily (TNFSF) molecule, has been demonstrated to provide a pivotal costimulatory signal to enhance CD4(+) T cell help of humoral and cytotoxic T cell immune responses. The present study examined whether an OX40L-expressing vector could boost the immunogenicity of the HIV-1 canarypox vaccine, vCP1452, in mice. Co-immunization of mice with OX40L-expressing canarypox and vCP1452 augmented HIV-1 specific CD8(+) T cell responses in terms of frequency and cytokine expression. OX40L-expressing canarypox enhanced the frequency of antigen specific CD8(+) T cells with an effector (CD127(-)CD62L(-)) phenotype, which was associated with an ex vivo expansion of HIV-1 specific CD4(+) T cells. This was in contrast to our previous work in which a CD40L-expressing construct preferentially enhanced antigen specific memory responses [Liu J, Yu Q, Stone GW, Yue FY, Ngai N, Jones RB, et al. CD40L expressed from the canarypox vector, ALVAC, can boost immunogenicity of HIV-1 canarypox vaccine in mice and enhance the in vitro expansion of viral specific CD8+ T cell memory responses from HIV-1-infected and HIV-1-uninfected individuals. Vaccine 2008;26(32):4062-72]. Surprisingly, OX40L did not enhance antibody responses elicited by the HIV-1 canarypox vaccine. We saw no added benefit by combining OX40L and CD40L vectors as an adjuvant strategy for vCP1452. Our results indicate that, similar to CD40L, canarypox vectors expressing OX40L can enhance the cellular but not humoral immunogenicity of HIV-1 canarypox vaccines. In summary, our findings show that OX40L can be used as a molecular adjuvant to enhance T cell immune responses.

Decreased 4-1BB expression on HIV-specific CD4+ T cells is associated with sustained viral replication and reduced IL-2 production

CD4+ T cell dysfunction in subjects with chronic HIV infection is in part due to an imbalance of costimulatory and coinhibitory receptors. We report that virus-specific CD4+ T cells expressing 4-1BB (CD137) or OX40 (CD134) produced more IL-2 than cells lacking these costimulatory receptors (P<0.05) and that 4-1BB was expressed at a lower level on HIV- than CMV-specific IFN-gamma and IL-2 producing CD4+ T cells (P<0.0001 and P<0.01, respectively). Suppression of viral replication with antiretroviral therapy was associated with increased 4-1BB expression on HIV- and CMV-specific IL-2 producing CD4+ T cells (P<0.05 and P<0.01, respectively) and the percentage of IL-2 producing HIV-specific CD4+ T cells that expressed 4-1BB was inversely correlated with HIV plasma viral load (r=-0.75, P=0.007). These findings indicate that the loss of 4-1BB on HIV-specific CD4+ T cells is associated with viral replication and that it may contribute to reduced IL-2 production observed during chronic infection.

Cross-regulation between herpesviruses and the TNF superfamily members

Herpesviruses have evolved numerous strategies to subvert host immune responses so they can coexist with their host species. These viruses 'co-opt' host genes for entry into host cells and then express immunomodulatory genes, including mimics of members of the tumour-necrosis factor (TNF) superfamily, that initiate and alter host-cell signalling pathways. TNF superfamily members have crucial roles in controlling herpesvirus infection by mediating the direct killing of infected cells and by enhancing immune responses. Despite these strong immune responses, herpesviruses persist in a latent form, which suggests a dynamic relationship between the host immune system and the virus that results in a balance between host survival and viral control.

Programmed death-1 expression is associated with the disease status in hepatitis B virus infection

AIM: To define the potential role of programmed death-1/programmed death-ligand (PD-1/PD-L) pathway in different hepatitis B virus (HBV) infection disease status; we examined the expression of PD-1 on antigen specific CD8+ T cells in peripheral blood of patients with chronic hepatitis B (CHB) and acute exacerbation of hepatitis B (AEHB) infection.

METHODS: The PD-1 level on CD8+ T lymphocytes and the number of HBV specific CD8+ T lymphocytes in patients and healthy controls (HCs) were analyzed by staining with pentameric peptide-human leukocyte antigen2 (HLA2) complexes combined with flow cytometry. Real-time quantitative polymerase chain reaction (PCR) was used to measure the serum HBV-DNA levels.

RESULTS: The level of PD-1 expression on total CD8+ T cells in CHB patients (13.86% ± 3.38%) was significantly higher than that in AEHB patients (6.80% ± 2.19%, P < 0.01) and healthy individuals (4.63% ± 1.23%, P < 0.01). Compared to AEHB patients (0.81% ± 0.73%), lower frequency of HBV-specific CD8+ T cells was detected in chronic hepatitis B patients (0.37% ± 0.43%, P < 0.05). There was an inverse correlation between the strength of HBV-specific CD8+ T-cell response and the level of PD-1 expression. Besides, there was a significant positive correlation between HBV viral load and the percentage of PD-1 expression on CD8+ T cells in CHB and AEHB subjects (R = 0.541, P < 0.01). However, PD-1 expression was not associated with disease flare-ups as indicated by alanine aminotransferase (ALT) levels (R = 0.066, P > 0.05).

CONCLUSION: Our results confirm previous reports that HBV specific CD8+ T-cell response in the peripheral blood is more intense in patients with AEHB than in chronic hepatitis B with persistent viral infection. Moreover, there is a negative correlation between the level of PD-1 and the intensity of virus specific CD8+ T cell response.

CD40L expressed from the canarypox vector, ALVAC, can boost immunogenicity of HIV-1 canarypox vaccine in mice and enhance the in vitro expansion of viral specific CD8+ T cell memory responses from HIV-1-infected and HIV-1-uninfected individuals

Human immunodeficiency virus type 1 (HIV-1) canarypox vaccines are safe but poorly immunogenic. CD40 ligand (CD40L), a member of the tumor necrosis factor superfamily (TNFSF), is a pivotal costimulatory molecule for immune responses. To explore whether CD40L can be used as an adjuvant for HIV-1 canarypox vaccine, we constructed recombinant canarypox viruses expressing CD40L. Co-immunization of mice with CD40L expressing canarypox and the canarypox vaccine expressing HIV-1 proteins, vCP1452, augmented HIV-1 specific cytotoxic T lymphocyte (CTL) responses in terms of frequency, polyfunctionality and interleukin (IL)-7 receptor alpha chain (IL-7Ralpha, CD127) expression. In addition, CD40L expressed from canarypox virus could significantly augment CD4+ T cell responses against HIV-1 in mice. CD40L expressed from canarypox virus matured human monocyte-derived dendritic cells (MDDCs) in a tumor necrosis factor-alpha (TNF-alpha) independent manner, which underwent less apoptosis, and could expand ex vivo Epstein-Barr virus (EBV)-specific CTL responses from healthy human individuals and ex vivo HIV-1-specific CTL responses from HIV-1-infected individuals in the presence or absence of CD4+ T cells. Taken together, our results suggest that CD40L incorporation into poxvirus vectors could be used as a strategy to enhance their immunogenicity.

OX40 signaling directly triggers the antitumor effects of NKT cells

Pathways involving the costimulatory molecule OX40 and OX40 ligand (OX40L) enhance tumor rejection. It was presumed that this effect was mediated by changes in DCs and/or T cells. In this issue of the JCI, Zaini et al. report that, in mice, intratumoral injection of DCs genetically modified to express OX40L suppressed the growth of a preexisting melanoma by directly triggering an antitumor NKT cell response (see the related article beginning on page 3330). This work suggests that the intratumoral NKT cell population may be harnessed for cancer immunotherapy and that OX40 costimulation may be used as a unique trigger of the antitumor activity of these cells.

Novel strategies to eliminate persistent viral infections

Infection with viruses that have the capacity to modulate or evade the immune response can result in persistence, which can lead to a variety of chronic problems including neoplasia, immunosuppression, autoimmune-like syndromes, and selective organ failure. Recently, two promising new treatment approaches that target either the inhibitory receptor programmed cell death 1 (PD-1) or neutralize interleukin-10 (IL-10) during chronic viral infection have been described. We discuss how future combination therapies can be used to inhibit viral synthesis as well as strengthen the antiviral response without increasing immunopathology or the development of autoimmune disease.

Glucocorticoid-induced tumor necrosis factor receptor family-related protein triggering enhances HIV-specific CD4+ T cell cytokine secretion and protects HIV-specific CD4+ T cells from apoptosis

Human immunodeficiency virus (HIV)-specific CD4(+) T cell cytokine secretion is characteristically weak during HIV infection, in part because HIV-specific CD4(+) T cells undergo massive apoptotic deletion. Glucocorticoid-induced tumor necrosis factor (TNF) receptor family-related (GITR) protein triggering enhances murine antigen-specific T cell cytokine secretion by protecting T cells from apoptosis. Therefore, we investigated the impact of GITR triggering on HIV-specific CD4(+) T cell cytokine secretion and on apoptosis of HIV-specific CD4(+) T cells. In HIV-infected subjects, CD4(+) T cell surface expression of GITR was greater than that in uninfected control subjects, and phytohemagglutinin induction of additional GITR expression was impaired. However, antibody triggering of GITR significantly increased HIV-specific CD4(+) T cell expression of TNF- alpha and interferon (IFN)- gamma . The percentage increase in HIV-specific CD4(+) T cell expression of TNF- alpha correlated directly with the absolute peripheral CD4(+) T cell count. Furthermore, GITR triggering reduced the expression of intracellular activated caspase-3 in HIV-specific CD4(+) T cells. Taken together, these data suggest that, despite abnormal GITR expression during HIV infection, GITR triggering enhances HIV-specific CD4(+) T cell cytokine expression and protects HIV-specific CD4(+) T cells from apoptosis.

Rapid memory CD8+ T-lymphocyte induction through priming with recombinant Mycobacterium smegmatis

The most promising vaccine strategies for the induction of cytotoxic-T-lymphocyte responses have been heterologous prime/boost regimens employing a plasmid DNA prime and a live recombinant-vector boost. The priming immunogen in these regimens must elicit antigen-specific memory CD8+ T lymphocytes that will expand following the boosting immunization. Because plasmid DNA immunogens are expensive and their immunogenicity has proven disappointing in human clinical trials, we have been exploring novel priming immunogens that might be used in heterologous immunization regimens. Here we show that priming with a prototype recombinant Mycobacterium smegmatis strain expressing human immunodeficiency virus type 1 (HIV-1) gp120-elicited CD4+ T lymphocytes with a functional profile of helper cells as well as a CD8+ T-lymphocyte population. These CD8+ T lymphocytes rapidly differentiated to memory cells, defined on the basis of their cytokine profile and expression of CD62L and CD27. Moreover, these recombinant-mycobacterium-induced T lymphocytes rapidly expanded following boosting with a recombinant adenovirus expressing HIV-1 Env to gp120-specific CD8+ T lymphocytes. This work demonstrates a remarkable skewing of recombinant-mycobacterium-induced T lymphocytes to durable antigen-specific memory CD8+ T cells and suggests that such immunogens might be used as priming vectors in prime/boost vaccination regimens for the induction of cellular immune responses.

Why can't the immune system control HIV-1? Defining HIV-1-specific CD4+ T cell immunity in order to develop strategies to enhance viral immunity

Globally, at least 60 million people have been infected with the human immunodeficiency virus type 1 (HIV-1), the majority of whom will develop the acquired immunodeficiency syndrome (AIDS) leading to tremendous morbidity and the mortality. Understanding the immunopathogenesis of AIDS and the immune correlates of viral protection are necessary to develop effective vaccines and immunotherapies. A major focus of our laboratory has been to understand the CD4+ T cell immune response directed against HIV- 1, and to determine mechanisms of T cell dysfunction that lead to viral escape. In addition, we are interested in evaluating the TNF-TNFR family members as potential molecular adjuvants that could be incorporated into vaccines which could be used to further boost T cell immunogenicity in healthy or HIV-1-infected individuals, as many of these molecules have been shown to replace the functions of CD4+ T cell help.

PD-1 is a regulator of virus-specific CD8+ T cell survival in HIV infection

Here, we report on the expression of programmed death (PD)-1 on human virus-specific CD8⁺ T cells and the effect of manipulating signaling through PD-1 on the survival, proliferation, and cytokine function of these cells. PD-1 expression was found to be low on naive CD8⁺ T cells and increased on memory CD8⁺ T cells according to antigen specificity. Memory CD8⁺ T cells specific for poorly controlled chronic persistent virus (HIV) more frequently expressed PD-1 than memory CD8⁺ T cells specific for well-controlled persistent virus (cytomegalovirus) or acute (vaccinia) viruses. PD-1 expression was independent of maturational markers on memory CD8⁺ T cells and was not directly associated with an inability to produce cytokines. Importantly, the level of PD-1 surface expression was the primary determinant of apoptosis sensitivity of virus-specific CD8⁺ T cells. Manipulation of PD-1 led to changes in the ability of the cells to survive and expand, which, over several days, affected the number of cells expressing cytokines. Therefore, PD-1 is a major regulator of apoptosis that can impact the frequency of antiviral T cells in chronic infections such as HIV, and could be manipulated to improve HIV-specific CD8⁺ T cell numbers, but possibly not all functions in vivo.