Enhanced interferon-gamma by CD8+ CD28- lymphocytes from HIV+ patients

Loss of Preexisting Immunological Memory Among Human Immunodeficiency Virus-Infected Women Despite Immune Reconstitution With Antiretroviral Therapy

BACKGROUND

It is unclear whether human immunodeficiency virus (HIV) infection results in permanent loss of T-cell memory or if it affects preexisting antibodies to childhood vaccinations or infections.

METHODS

We conducted a matched cohort study involving 50 pairs of HIV-infected and HIV-uninfected women. Total memory T-cell responses were measured after anti-CD3 or vaccinia virus (VV) stimulation to measure T cells elicited after childhood smallpox vaccination. VV-specific antibodies were measured by means of enzyme-linked immunosorbent assay (ELISA).

RESULTS

There was no difference between HIV-infected and HIV-uninfected study participants in terms of CD4+ T-cell responses after anti-CD3 stimulation (P = .19) although HIV-infected participants had significantly higher CD8+ T-cell responses (P = .03). In contrast, there was a significant loss in VV-specific CD4+ T-cell memory among HIV-infected participants (P = .04) whereas antiviral CD8+ T-cell memory remained intact (P > .99). VV-specific antibodies were maintained indefinitely among HIV-uninfected participants (half-life, infinity; 95% confidence interval, 309 years to infinity) but declined rapidly among HIV-infected participants (half-life; 39 years; 24-108 years; P = .001).

CONCLUSIONS

Despite antiretroviral therapy-associated improvement in CD4+ T-cell counts (nadir, <200/μL; >350/μL after antiretroviral therapy), antigen-specific CD4+ T-cell memory to vaccinations or infections that occurred before HIV infection did not recover after immune reconstitution, and a previously unrealized decline in preexisting antibody responses was observed.

HIV-1 Tat affects the programming and functionality of human CD8⁺ T cells by modulating the expression of T-box transcription factors

OBJECTIVE

HIV infection is characterized by several immune dysfunctions of both CD8⁺ and CD4⁺ T cells as hyperactivation, impairment of functionality and expansion of memory T cells. CD8⁺ T-cell dysfunctions have been associated with increased expression of T-bet, Eomesdermin and pro-inflammatory cytokines, and with down-regulation of CD127. The HIV-1 trans-activator of transcription (Tat) protein, which is released by infected cells and detected in tissues of HIV-positive individuals, is known to contribute to the dysregulation of CD4⁺ T cells; however, its effects on CD8⁺ T cells have not been investigated. Thus, in this study, we sought to address whether Tat may affect CD8⁺ T-cell functionality and programming.

METHODS

CD8⁺ T cells were activated by T-cell receptor engagement in the presence or absence of Tat. Cytokine production, killing capacity, surface phenotype and expression of transcription factors important for T-cell programming were evaluated.

RESULTS

Tat favors the secretion of interleukin-2, interferon-γ and granzyme B in CD8⁺ T cells. Behind this functional modulation we observed that Tat increases the expression of T-bet, Eomesdermin, Blimp-1, Bcl-6 and Bcl-2 in activated but not in unstimulated CD8⁺ T lymphocytes. This effect is associated with the down-regulation of CD127 and the up-regulation of CD27.

CONCLUSION

Tat deeply alters the programming and functionality of CD8⁺ T lymphocytes.

Treatment of cachexia: melanocortin and ghrelin interventions

Cachexia is a condition typified by wasting of fat and LBM caused by anorexia and further endocrinological modulation of energy stores. Diseases known to cause cachectic symptoms include cancer, chronic kidney disease, and chronic heart failure; these conditions are associated with increased levels of proinflammatory cytokines and increased resting energy expenditure. Early studies have suggested the central melanocortin system as one of the main mediators of the symptoms of cachexia. Pharmacological and genetic antagonism of these pathways attenuates cachectic symptoms in laboratory models; effects have yet to be studied in humans. In addition, ghrelin, an endogenous orexigenic hormone with receptors on melanocortinergic neurons, has been shown to ameliorate symptoms of cachexia, at least in part, by an increase in appetite via melanocortin modulation, in addition to its anticatabolic and anti-inflammatory effects. These effects of ghrelin have been confirmed in multiple types of cachexia in both laboratory and human studies, suggesting a positive future for cachexia treatments.

Dysregulated expression of both the costimulatory CD28 and inhibitory CTLA-4 molecules in PB T cells of advanced cervical cancer patients suggests systemic immunosuppression related to disease progression

Cervical cancer (CC) occurs more frequently in women who are immunosuppressed, suggesting that both local and systemic immune abnormalities may be involved in the evolution of the disease. Costimulatory CD28 and inhibitory CTLA-4 molecules expressed in T cells play a key role in the balanced immune responses. There has been demonstrated a relation between CD28, CTLA-4, and IFN genes in susceptibility to CC, suggesting their importance in CC development. Therefore, we assessed the pattern of CD28 and CTLA-4 expression in T cells from PB of CC patients with advanced CC (stages III and IV according to FIGO) compared to controls. We also examined the ability of PBMCs to secrete IFN-gamma. We found lower frequencies of freshly isolated and ex vivo stimulated CD4 + CD28+ and CD8 + CD28+ T cells in CC patients than in controls. Loss of CD28 expression was more pronounced in the CD8+ T subset. Markedly increased proportions of CTLA-4+ T cells in CC patients before and after culture compared to controls were also observed. In addition, patients’ T cells exhibited abnormal kinetics of surface CTLA-4 expression, with the peak at 24 h of stimulation, which was in contrast to corresponding normal T cells, revealing maximum CTLA-4 expression at 72 h of stimulation. Of note, markedly higher IFN-gamma concentrations were shown in supernatants of stimulated PBMCs from CC patients. Conclusions: Our report shows the dysregulated CD28 and CTLA-4 expression in PB T cells of CC patients, which may lead to impaired function of these lymphocytes and systemic immunosuppression related to disease progression.

HIV-1 matrix protein p17: a candidate antigen for therapeutic vaccines against AIDS

The success in the development of anti-retroviral therapies (HAART) that contain human immunodeficiency virus type 1 (HIV-1) infection is challenged by the cost of this lifelong therapy and by its toxicity. Immune-based therapeutic strategies that boost the immune response against HIV-1 proteins or protein subunits have been recently proposed to control virus replication in order to provide protection from disease development, reduce virus transmission, and help limit the use of anti-retroviral treatments. HIV-1 matrix protein p17 is a structural protein that is critically involved in most stages of the life cycle of the retrovirus. Besides its well established role in the virus life cycle, increasing evidence suggests that p17 may also be active extracellularly in deregulating biological activities of many different immune cells that are directly or indirectly involved in AIDS pathogenesis. Thus, p17 might represent a promising target for developing a therapeutic vaccine as a contribution to combating AIDS. In this article we review the biological characteristics of HIV-1 matrix protein p17 and we describe why a synthetic peptide representative of the p17 functional epitope may work as a vaccine molecule capable of inducing anti-p17 neutralizing response against p17 derived from divergent HIV-1 strains.

IFN-gamma-activated monocytes weakly produce HIV-1 but induce the recruitment of HIV-sensitive T cells and enhance the viral production by these recruited T cells

The ability of macrophages to adapt to changing cytokine environments results in the dominance of a particular functional phenotype of macrophages, which would play a significant role in HIV pathogenesis. In comparison with untreated macrophages (M0), we examined the role of macrophages derived from IFN-gamma-activated monocytes (M1) in the HIV spread. We show that M0 and M1 bind with the same efficiency HIV-1 with a predominant role of C-type lectins in the R5-HIV attachment and of the heparan sulfate proteoglycans in the X4-HIV attachment. Despite similar levels of R5- and X4-HIV DNA, M1 replicates and weakly transmits the virus to activated T cells by releasing CXCR4- and CCR5-interacting chemokines. The blockade of dendritic cell-specific ICAM-3-grabbing nonintegrin expressed on M1 by mAb does not interfere with the viral transfer. Uninfected M1 recruits HIV-sensitive T cells efficiently and releases soluble factors, enhancing the viral production by these recruited cells. This study highlights the role of IFN-gamma to induce a population of macrophages that archive HIV-1 within a latent stage and cause the persistence of the virus by favoring the recruitment of T cells or enhancing the viral replication in infected CD4(+) T cells.

T Cell Modulation of Intimal Thickening After Vascular Injury

BACKGROUND

Immune deficiency results in exuberant intimal thickening after arterial injury. The mechanisms involved are not well defined. We investigated the role of T cells and IFN-gamma in the response to injury in normal and immune-deficient Rag-1KO mice.

METHODS AND RESULTS

Carotid arterial injury was induced in wild-type (WT), Rag-1KO mice, and Rag-1KO mice reconstituted with T cell-enriched splenocytes. The exuberant intimal thickening in Rag-1KO mice compared with WT mice 21 days after injury was reduced by T cell transfer (P<0.01). Exogenous IFN-gamma starting on the day of injury inhibited intimal thickening in Rag-1KO mice. However, antibody neutralization of endogenous IFN-gamma in Rag-1KO mice starting 7 days after injury decreased intimal thickening, indicating that late presence of IFN-gamma promoted intimal thickening in Rag-1KO mice. Results further suggest that the effect of late IFN-gamma in Rag-1KO mice is mediated in part by increased IRF-1 and iNOS expression, coupled with low SOCS1 expression.

CONCLUSIONS

T cells inhibit intimal thickening in the early stages of the response to injury through basal IFN-gamma secretion. In the Rag-1KO mice, late IFN-gamma expression promotes intimal thickening. These findings add novel insight to conditions of immune deficiency that affect intimal thickening.

Gamma interferon-mediated inflammation is associated with lack of protection from intravaginal simian immunodeficiency virus SIVmac239 challenge in simian-human immunodeficiency virus 89.6-immunized rhesus macaques

Although gamma interferon (IFN-gamma) is a key mediator of antiviral defenses, it is also a mediator of inflammation. As inflammation can drive lentiviral replication, we sought to determine the relationship between IFN-gamma-related host immune responses and challenge virus replication in lymphoid tissues of simian-human immunodeficiency virus 89.6 (SHIV89.6)-vaccinated and unvaccinated rhesus macaques 6 months after challenge with simian immunodeficiency virus SIVmac239. Vaccinated-protected monkeys had low tissue viral RNA (vRNA) levels, vaccinated-unprotected animals had moderate tissue vRNA levels, and unvaccinated animals had high tissue vRNA levels. The long-term challenge outcome in vaccinated monkeys was correlated with the relative balance between SIV-specific IFN-gamma T-cell responses and nonspecific IFN-gamma-driven inflammation. Vaccinated-protected monkeys had slightly increased tissue IFN-gamma mRNA levels and a high frequency of IFN-gamma-secreting T cells responding to in vitro SIVgag peptide stimulation; thus, it is likely that they could develop effective anti-SIV cytotoxic T lymphocytes in vivo. In contrast, both high tissue IFN-gamma mRNA levels and strong in vitro SIV-specific IFN-gamma T-cell responses were detected in lymphoid tissues of vaccinated-unprotected monkeys. Unvaccinated monkeys had increased tissue IFN-gamma mRNA levels but weak in vitro anti-SIV IFN-gamma T-cell responses. In addition, in lymphoid tissues of vaccinated-unprotected and unvaccinated monkeys, the increased IFN-gamma mRNA levels were associated with increased Mig/CXCL9, IP-10/CXCL10, and CXCR3 mRNA levels, suggesting that increased Mig/CXCL9 and IP-10/CXCL10 expression resulted in recruitment of CXCR3(+) activated T cells. Thus, IFN-gamma-driven inflammation promotes SIV replication in vaccinated-unprotected and unvaccinated monkeys. Unlike all unvaccinated monkeys, most monkeys vaccinated with SHIV89.6 did not develop IFN-gamma-driven inflammation, but they did develop effective antiviral CD8(+)-T-cell responses.

Lack of CD28 expression on HIV‐specific cytotoxic T lymphocytes is associated with disease progression

During HIV infection, CD8+ T cells lacking the costimulatory molecule CD28 increase in number and proportion. This accumulation is associated with disease activity and possibly with CD8+ T-cell dysfunction. In this study, CD8+CD28+ and CD8+CD28- T cells from 41 HIV-infected individuals at various stages of disease were compared in terms of HIV-specific cytotoxicity, TCR beta V repertoire diversity, and cytokine production. We found that the CD28 phenotype of anti-HIV CTL evolves in parallel with disease progression and disease activity. Absolute numbers of CD4+ T cells and CD4+/CD8+ T-cell ratios progressively decreased in 3 groups with an increasing prevalence of CD28- HIV-specific CTL. Conversely, HIV replication levels progressively increased in parallel with the prevalence of CD28- HIV-specific CTL. Repertoire diversity at the level of TCR beta V gene family expression was maintained at normal levels for both CD28+ and CD28- T cells at all stages of infection. Diversity at the level of junctional length polymorphism was more restricted in the CD8+CD28- T-cell population, but this difference remained relatively constant through different stages of infection. Both CD28+ and CD28- T cells produced IL-2 and IFN-gamma, regardless of disease stage and/or the predominant CD28 phenotype of anti-HIV CTL.

HIV infection and aging: enhanced Interferon- and Tumor Necrosis Factor-alpha production by the CD8+ CD28- T subset

BACKGROUND

T cells from HIV+ and aged individuals show parallels in terms of suppressed proliferative activity and interleukin-2 (I1-2) production and an increased number of CD8+ CD28- T cells. In order to compare cytokine production from T cells from these two states, CD4+ and CD8+ T cells from HIV+ aged, and normal young donors (controls) were monitored for cytokine production by flow cytometry, quantitative PCR and ELISA upon activation by PMA and anti-CD3. In addition, the CD8+ T cell subsets CD28+ and CD28- from the HIV+ and the aged groups were evaluated for cytokine production by flow cytometry, and compared with those from young controls.

RESULTS

Flow cytometric analysis indicated that CD8+ T cells from both HIV+ and aged donors showed an increase of approximately 2-3 fold over controls in percentage of cells producing inflammatory cytokines IFN-gamma and TNF-alpha. Similar analysis also revealed that the production of interleukins-4,6 and 10, production was very low (1-2% of cells) and unchanged in these cells. Quantitative PCR also showed a substantial increase (4-5 fold) in IFN-gamma and TNF-alpha mRNA from HIV+ and aged CD8+ T cells, as did ELISA for secreted IFN-gamma and TNF-alpha (2.3-4 fold). Flow cytometric analysis showed that the CD8+ CD28- T cell subset accounts for approximately 80-86% of the IFN-gamma and TNF-alpha production from the CD8+ subset in the aged and HIV+ states. The CD4+ T cell, while not significantly changed in the HIV+ or aged states in terms of IFN-gamma production, showed a small but significant increase in TNF-alpha production in both states.

CONCLUSIONS

Our data appear compatible with physiologic conditions existing in HIV+ and aged individuals, i.e. elevated serum levels and elevated CD8+ T cell production of IFN-gamma and TNF-alpha. Thus, the capacity for increased production of cytokines IFN-gamma and TNF-alpha in the aged individual by the dominant CD8+ CD28- subset may have a profound influence on the clinical state by aggravating inflammatory pathologies such as rheumatoid arthritis, and possibly Alzheimer's disease and Crohn's disease. In AIDS, these cytokines may contribute to wasting and cachexia. We theorize that the predominant phenotypic change to the cytotoxic CD8+ CD28- T cell subsets in both the HIV+ and the aged states may reflect a natural "endpoint" in CD8+ T cell differentiation induced after a lifetime of immune activity (toward viruses, etc) in the aged, and after a massive accelerated response to HIV in the HIV-positive individual.

CD40-CD40L interactions induce chemokine expression by human microglia: implications for human immunodeficiency virus encephalitis and multiple sclerosis

CD40 is a protein on microglia that is up-regulated with interferon (IFN)-gamma and is engaged by CD40L, found on CD4+ T cells, B cells, and monocytes. These interactions may be important in central nervous system inflammatory diseases. Microglia have been shown to be a source of chemokines, whose expression plays a key role in central nervous system pathologies. We examined the expression of CD40 on microglia in human immunodeficiency virus (HIV) encephalitic brain, and the effects of CD40-CD40L interactions on the expression of chemokines by cultured microglia. We found significantly increased numbers of CD40-positive microglia in HIV-infected brain tissue. Treatment of cultured microglia with IFN-gamma and CD40L increased expression of several chemokines. IFN-gamma- and CD40L-induced MCP-1 protein was mediated by activation of the ERK1/2 MAPK pathway, and Western blot analysis demonstrated phosphorylation of ERK1/2 upon stimulation of microglia. In contrast, IFN-gamma- and CD40L-induced IP-10 protein production was mediated by the p38 MAPK pathway. Our data suggest a mechanism whereby CD40L+ cells can induce microglia to secrete chemokines, amplifying inflammatory processes seen in HIV encephalitis and multiple sclerosis, and implicate CD40-CD40L interactions as a target for interventional strategies.