Human gamma delta T lymphocytes in HIV disease: effector functions and control by natural killer cell receptors

Interleukin-18 activates Vγ9Vδ2+ T cells from HIV-positive individuals: recovering the response to phosphoantigen

The study aimed to identify an immunoregulatory factor that restores the phosphoantigen response of Vγ9Vδ2⁺ T cells from HIV-positive individuals on antiretroviral therapy. It was designed to characterize the effects of interleukin-18 (IL-18) on proliferation and effector function in Vγ9Vδ2 T cells from HIV-negative individuals and test whether exogenous IL-18 reconstitutes the Vγ9Vδ2 T-cell response to phosphoantigen from HIV-positive donors. Vγ9Vδ2 T cells from HIV-negative individuals responded strongly to phosphoantigen or aminobisphosphonate stimulation of peripheral blood mononuclear cells (PBMC), whereas cells with similar T-cell receptor profiles from HIV-positive individuals only responded to aminobisphosphonate. Interleukin-18 was higher after aminobisphosphonate stimulation due to activation of the inflammasome pathway. Both IL-18 and IL-18 receptor levels were measured and the activity of exogenous IL-18 on HIV-negative and HIV-positive PBMC was evaluated in terms of Vγ9Vδ2 T-cell proliferation, memory subsets, cytokine expression and CD107a expression. Interleukin-18 stimulation increased proliferation, enhanced the accumulation of effector memory cells, and increased expression of cytotoxic markers in HIV-negative controls. When Vγ9Vδ2 T cells from HIV-positive individuals were stimulated with isopentenyl pyrophosphate in the presence of IL-18, there was increased proliferation, accumulation of memory cells, and higher expression of CD56, NKG2D and CD107a (markers of cytotoxic effector phenotype). Interleukin-18 stimulation specifically expanded the Vγ9-JγP⁺ subset of Vγ9Vδ2 T cells, as was expected for normal responses to phosphoantigen. Interleukin-18 is a potent stimulator of Vγ9Vδ2 T-cell proliferation and effector function. Therapies directed at reconstituting Vγ9Vδ2 T-cell activity in HIV-positive individuals should include stimulators of IL-18 or direct cytokine supplementation.

High levels of X-linked Inhibitor-of-Apoptosis Protein (XIAP) are indicative of radio chemotherapy resistance in rectal cancer

BACKGROUND

The mainstay of treatment in rectal cancer is neoadjuvant radio chemotherapy prior to surgery, in an attempt to downstage the tumour, allowing for more complete removal during surgery. In 40 % of cases however, this neoadjuvant radio chemotherapy fails to achieve tumour regression, partly due insufficient apoptosis signaling. X-linked Inhibitor of Apoptosis Protein (XIAP) is an anti-apoptotic protein that has been reported to contribute to disease progression and chemotherapy resistance.

METHODS

We obtained rectal biopsy normal and matched tumour tissue from 29 rectal cancer patients with varying degrees of tumour regression, and using Western blot, examined anti-apoptotic XIAP and pro-apoptotic Smac protein levels in these tissues, with the aim to examine whether disturbed XIAP/Smac levels may be an indicator of neoadjuvant radio chemotherapy resistance. Expression of inhibitor of apoptosis proteins cIAP-1 and cIAP-2 was also examined.

RESULTS

We found that levels of XIAP increased in accordance with the degree of radio chemotherapy resistance of the tissue. Levels of this protein were also significantly higher in tumour tissue, compared to matched normal tissue in highly resistant tissue. In contrast, Smac protein levels did not increase with radio chemotherapy resistance, and the protein was similarly expressed in normal and tumour tissue, indicating a shift in the balance of these proteins. Post treatment surgical resection tissue was available for 8 patients. When we compared matched tissue pre- and post- radio chemotherapy we found that XIAP levels increased significantly during treatment in both normal and tumour tissue, while Smac levels did not change. cIAP-1 and cIAP-2 levels were not differentially expressed in varying degrees of radio chemotherapy resistance, and neoadjuvant therapy did not alter expression of these proteins.

CONCLUSION

These data indicate that disturbance of the XIAP/Smac balance may be a driver of radio chemotherapy resistance, and hence high levels of XIAP may be a useful indicator of neoadjuvant radio chemotherapy resistance in rectal cancer. Moreover, as XIAP levels increase with radio chemotherapy it is possible that a subset of more resistant tumour cells survive this treatment and may be resistant to further adjuvant treatment. Patients with resistant tumours highly expressing XIAP may benefit from alternative treatment strategies, such as Smac mimetics post neoadjuvant radio chemotherapy.

HIV Gag-specific immune response mediated by double negative (CD3(+)CD4(-)CD8(-)) T cells in HIV-exposed seronegative individuals

Double negative (DN) T cells are CD3(+), CD4(-), CD8(-) cells with either T-cell receptors (TCR) αβ or TCR γδ whose importance on protection against HIV infection is unknown. Since HIV-exposed seronegative individuals correspond to an ideal group in whom correlates of protection are expected, the role of these cells was studied in 13 HIV-serodiscordant couples in a stable relationship and reporting unprotected sexual intercourses. HIV-specific immune responses mediated by DN T-cells were evaluated by measuring intracellular IFNγ and MIP1β (CCL4) production in response to HIV-Gag peptides. Thirty-five healthy controls not exposed to HIV were tested similarly and used to define a threshold for positive responses. Interestingly, Gag-specific DN T-cell responses were found in 3/13 (23%) HIV-exposed seronegative individuals (Group A), involving both DN/αβ(+) and DN/γδ(+) T-cells through MIP1β and IFNγ production. 4/13 (30%) of partners infected with HIV (Group B) also showed Gag-specific responses but were mediated exclusively by DN/γδ(+) T-cells, mainly through IFNγ production. DN T-cells in Group A individuals can display differential HIV-specific immune responses, which might contribute to the low susceptibility to infection with HIV shown by individuals in Group A.

Natural viral suppressors of HIV-1 have a unique capacity to maintain gammadelta T cells

OBJECTIVE

To evaluate Vgamma2Vdelta2 T cells in a group of HIV-infected patients who suppress HIV replication without antiretroviral therapy (natural viral suppressors, NVSs).

DESIGN

: It is a cross-sectional study.

METHODS

We compared Vgamma2Vdelta2 T-cell frequency, T-cell repertoire, and responses to isopentenyl pyrophosphate stimulation between NVSs (n = 21) and HIV-uninfected controls (n = 27) and between NVSs and HIV-infected patients taking HAART with suppressed viral replication (HIV-P; n = 25).

RESULTS

NVSs had a mean frequency of 1.06 +/- 0.82% CD3Vdelta2+ cells among total lymphocytes, which was significantly higher than both control groups (HIV-negative: 0.50 +/- 0.53%, P = 0.042; HIV-P: 0.34 +/- 0.37%, P = 0.002). The proportion of Vgamma2 chains correlating with the Vgamma2-Jgamma1.2 rearrangement was reduced among NVSs compared with HIV-negative controls (0.57 +/- 0.06 vs. 0.32 +/- 0.04; P = 0.016) but was increased compared with HIV-P patients (0.32 +/- 0.04 vs. 0.22 +/- 0.03; P = 0.03). NVSs had a similar baseline frequency of CD27/CD45RA effector cells (19.6 +/- 4.2%) compared with HIV-negative controls (20.8 +/- 12.9%; P = 0.35).

CONCLUSION

The altered gammadelta T-cell receptor repertoire among NVS was consistent with the known effect of HIV-1 on these cells. Uniquely among all HIV-infected groups, NVS reconstituted the gammadelta T-cell population, eventually reaching levels significantly above controls. This capacity to recover gammadelta T-cell numbers and function distinguishes individuals who control HIV-1 with and without HAART.

Ligand-independent exhaustion of killer immunoglobulin-like receptor-positive CD8+ T cells in human immunodeficiency virus type 1 infection

Virus-specific CD8(+) T cells play a central role in the control of viral infections, including human immunodeficiency virus type 1 (HIV-1) infection. However, despite the presence of strong and broad HIV-specific CD8(+) T-cell responses in chronic HIV-1 infection, these cells progressively lose critical effector functions and fail to clear the infection. Mounting evidence suggests that the upregulation of several inhibitory regulatory receptors on the surface of CD8(+) T cells during HIV-1 infection may contribute directly to the impairment of T-cell function. Here, we investigated the role of killer immunoglobulin receptors (KIR), which are expressed on NK cells and on CD8(+) T cells, in regulating CD8(+) T-cell function in HIV-1 infection. KIR expression was progressively upregulated on CD8(+) T cells during HIV-1 infection and correlated with the level of viral replication. Expression of KIR was associated with a profound inhibition of cytokine secretion, degranulation, proliferation, and activation by CD8(+) T cells following stimulation with T-cell receptor (TCR)-dependent stimuli. In contrast, KIR(+) CD8(+) T cells responded potently to TCR-independent stimulation, demonstrating that these cells are functionally competent. KIR-associated suppression of CD8(+) T-cell function was independent of ligand engagement, suggesting that these regulatory receptors may constitutively repress TCR activation. This ligand-independent repression of TCR activation of KIR(+) CD8(+) T cells may represent a significant barrier to therapeutic interventions aimed at improving the quality of the HIV-specific CD8(+) T-cell response in infected individuals.

Development of Vgamma2Vdelta2+ T cell responses during active mycobacterial coinfection of simian immunodeficiency virus-infected macaques requires control of viral infection and immune competence of CD4+ T cells

Vgamma2Vdelta2+ T cells play a role in antimicrobial responses. It is unknown whether adaptive Vgamma2Vdelta2+ T cell responses during active mycobacterial coinfection of human immunodeficiency virus-infected humans can be generated during effective antiretroviral treatment. Here, simian immunodeficiency virus (SIV)mac-infected macaques previously exposed to bacille Calmette-Guerin (BCG) were reinfected with BCG, were treated either with tenofovir or tenofovir plus indinavir, and were assessed for the development of Vgamma2Vdelta2+ T cell responses during active BCG coinfection. A restored capacity of Vgamma2Vdelta2+ T cells to undergo major expansions and pulmonary migration during active BCG coinfection was detected after simultaneous BCG reinfection and treatment with tenofovir of the SIVmac-infected macaques. Interestingly, a restored expansion of Vgamma2Vdelta2+ T cells in the SIVmac/BCG-coinfected macaques was detectable, even though antiretroviral treatment was initiated 1 month after BCG reinfection. Importantly, the restored expansion of Vgamma2Vdelta2+ T cells coincided with increases in numbers of purified protein derivative-specific interferon- gamma -producing CD4+ T cells and increases in the magnitude of their proliferative responses. In contrast, the SIVmac-infected control macaques exhibited diminished responses of Vgamma2Vdelta2+ T cells and mycobacterium-specific CD4+ T cells during active BCG coinfection. Our results suggest that the development of adaptive immune responses of phosphoantigen-specific Vgamma2Vdelta2+ T cells during active mycobacterium/HIV coinfection requires control of viral infection and immune competence of peptide-specific CD4+ T cells.

Differential expression of natural killer receptors on Vdelta1 gammadelta T cells in HIV-1-infected individuals

gammadelta T cells expressing the Vdelta1 T-cell receptor are increased in HIV-1-infected individuals. Since T-cell activation is modulated by inhibitory and activating natural killer receptors (NKRs), we investigated the expression of NKRs on Vdelta1 T cells in 22 HIV-1 infected patients by 2-color flow cytometry. We observed a strongly increased expression of several NKRs on ex vivo analyzed Vdelta1 T cells from HIV+ patients. Furthermore, we show that the in vitro stimulation of CD94- Vdelta1 T cells induced strong expression of inhibitory NKR CD94/CD159A (NKG2A). Our results suggest that the increased expression of NKRs might result from chronic activation of Vdelta1 T cells in HIV-1-infected persons.

Vgamma2Vdelta2+ T cells and anti-microbial immune responses

Vgamma2Vdelta2(+) T cells exist only in primates and constitute the majority of circulating human gammadelta T cells. Recent studies have demonstrated that this unique gammadelta T cell subpopulation can be a component of adaptive immune responses and contribute to anti-microbial immunity to infections.

Inhibition of adaptive Vgamma2Vdelta2+ T-cell responses during active mycobacterial coinfection of simian immunodeficiency virus SIVmac-infected monkeys

Adaptive immune responses of gammadelta T cells during active mycobacterial coinfection of human immunodeficiency virus-infected humans have not been studied. Macaques infected with the simian immunodeficiency virus (SIV) SIVmac were employed to determine the extent to which a coincident AIDS virus infection might compromise immune responses of mycobacterium-specific Vgamma2Vdelta2(+) T cells during active mycobacterial infection. Control SIVmac-negative macaques developed primary and recall expansions of phosphoantigen-specific Vgamma2Vdelta2(+) T cells after Mycobacterium bovis BCG infection and BCG reinfection, respectively. In contrast, SIVmac-infected macaques did not exhibit sound primary and recall expansions of Vgamma2Vdelta2(+) T cells in the blood and pulmonary alveoli following BCG infection and reinfection. The absence of adaptive Vgamma2Vdelta2(+) T-cell responses was associated with profound CD4(+) T-cell deficiency and subsequent development of SIVmac-related tuberculosis-like disease in the coinfected monkeys. Consistently, Vgamma2Vdelta2(+) T cells from coinfected monkeys displayed a reduced capacity to expand in vitro following stimulation with phosphoantigen. The reduced ability of Vgamma2Vdelta2(+) peripheral blood lymphocytes (PBL) to expand could be restored to some extent by coculture of these cells with CD4(+) T cells purified from PBL of SIV-negative monkeys. Furthermore, naïve monkeys inoculated simultaneously with SIVmac and BCG were unable to sustain expansion of Vgamma2Vdelta2(+) T cells at the time that the coinfected monkeys developed lymphoid depletion and a fatal tuberculosis-like disease. Nevertheless, no deletion in Vdelta2 T-cell receptor repertoire was identified in SIVmac-BCG-coinfected macaques, implicating an SIVmac-induced down-regulation rather than a clonal exhaustion of these cells. Thus, an SIVmac-induced compromise of the adaptive Vgamma2Vdelta2(+) T-cell responses may contribute to the immunopathogenesis of the SIV-related tuberculosis-like disease in macaques.

Mechanistic perspectives on sulfonamide-induced cutaneous drug reactions

PURPOSE OF REVIEW

Idiosyncratic drug reactions continue to limit the therapeutic utility of sulfonamide drugs because of their associated morbidity and mortality. Cutaneous reactions are the predominant reasons for withdrawal of such drugs from use in patients. As a consequence of the recognized metabolic and immunologic capability of the skin, an understanding of the pathogenic role of this tissue in the development of sulfonamide-induced cutaneous drug reactions may provide insight into the mechanisms and risk factors for these and other adverse drug events.

RECENT FINDINGS

In the present review we discuss currently available mechanistic information, including issues related to drug bioactivation and adduct formation, immunoresponsiveness, and immune dysregulation, for the development of sulfonamide-induced (delayed-type) cutaneous drug reactions. The potential application of findings from several related areas of research are also discussed within the context of the pathogenesis of these cutaneous reactions.

SUMMARY

Despite progress, numerous unresolved issues support the testing of novel hypotheses, the search for additional risk factors, and the need for a global approach, including links between laboratory and clinical paradigms. These issues must be addressed if we are to gain an understanding of the mechanistic bases for these cutaneous drug reactions.

Reciprocal alterations of Th1/Th2 function in gammadelta T-cell subsets of human immunodeficiency virus-1-infected patients

While T cells that express Vgamma9 as a variable T-cell receptor chain dominate among peripheral blood gammadelta T cells in healthy adults, Vdelta1 cells are the major subpopulation of gammadelta T cells in human immunodeficiency virus (HIV)-infected patients. We used intracellular cytokine staining and flow cytometry to analyse whether an imbalance of T helper 1 (Th1)/T helper 2 (Th2) cytokine patterns, as observed in alphabeta T cells, also occurs in gammadelta T cells. When compared with healthy HIV-negative subjects, HIV+ patients had a decreased number of interferon-gamma (IFN-gamma)+gammadelta T cells, which showed a linear relation to the CD4+ cell count but not to the plasma viral load. Similar results were obtained when Vgamma9 cells were analysed. In contrast, in the Vdelta1 subpopulation, the number of IFN-gamma+ cells was increased in HIV+ donors when compared with healthy subjects. Even though less impressive, the number of interleukin 4 (IL-4)- and IL-10-producing cells was uniformly inversely correlated with the number of tumour necrosis factor-alpha+ and IFN-gamma+ cells. The increased IFN-gamma-producing capacity of Vdelta1 cells might represent a compensatory mechanism for the progressive loss of Vgamma9 gammadelta T cells during the course of HIV infection.

Innate T cell immunity to HIV-infection. Immunotherapy with phosphocarbohydrates, a novel strategy of immune intervention?

Natural T (NT) lymphocytes recognize infected cells or microbial compounds without the classical genetic restriction of polymorphic major histocompatibility complex (MHC) molecules. NT cells are mainly composed of alphabeta and gammadelta T lymphocytes that express natural killer (NK) receptors and recognize preferentially various nonpeptidic antigens. Similar to NK cells, NT lymphocytes can see and kill target cells deficient in the expression of one or more MHC class I molecules. NT cells expressing the alphabeta TCR can recognize lipid and lipoglycan antigens presented in the context of nonpolymorphic CD1 molecules, whereas phosphocarbohydrates and alkylamines induce constitutive response of Vgamma9Vdelta2 T cells. The stimulation of Vgamma9Vdelta2 T cells with phosphocarbohydrates induces the production of cytokines (IFNgamma and TNFalpha) and the release of chemokines with suppressive activity on HIV replication. In addition, stimulated Vgamma9Vdelta2 T cells exert a cytolytic activity against HIV-infected targets. In HIV-infected patients, a quantitative and qualitative alteration is observed early during the infection. Vgamma9Vdelta2 T cells are deleted and the remaining gammadelta cells are anergic. Th1 cytokines (IL-12 and IL-15) positively regulate cytokine production by Vgamma9Vdelta2 T cells but they are inefficient in restoring normal functions in patients' gammadelta T cells. Interestingly, partial restoration of the immune system under highly active antiretroviral therapies (HAART) is associated to the recovery of functional Vgamma9Vdelta2 T cells. A large panel of phosphocarbohydrates able to selectively stimulate Vgamma9Vdelta2 T cells is currently available, and preliminary experiments in monkeys suggest their in vivo efficacy in helping to control SIV replication. These observations prompt the question of new immune intervention involving molecules that stimulate NT cells.

Comparative biology of gamma delta T cells

Accumulative evidence suggests that resident gamma delta T cells in epithelia are biologically distinct from systemic gamma delta T cells in the circulation. Murine resident gamma delta T cells have innate immune characteristics and play an important role in tissue homeostasis after damages. In contrast, a unique subset of circulating gamma delta T cells in primates, like alpha beta T cells, can mount adaptive immune responses in infections. This article compares biological features between resident and circulating gamma delta T cells.

Differentiation of resting human peripheral blood gamma delta T cells toward Th1- or Th2-phenotype

Depending on the microenvironment, murine gamma delta T cells differentiate into either Th1 (IFN-gamma-producing) or Th2 (IL-4-producing) cells. It is unclear, however, whether circulating human peripheral blood gamma delta T cells can be driven into Th1 or Th2 cells by modulation of the priming cytokine milieu. In this study, peripheral blood gamma delta T cells were stimulated by phosphoantigen (isopentenyl pyrophosphate) or Daudi lymphoma cells in the presence of Th1-priming (rIL-12, anti-IL-4 Ab) or Th2-priming (rIL-4, anti-IL-12 Ab) conditions. Single-cell analysis of cytokine secretion (IFN-gamma and IL-4) was performed by flow cytometry after 18 h and after restimulation of expanded gamma delta T cells. The early activation of resting gamma delta T cells was characterized by the induction of IFN-gamma. Priming under Th1 conditions induced a Th1 profile characterized by increased secretion of IFN-gamma and TNF-alpha, while Th2 conditions caused increased production of IL-4 (Th2 profile) by the gamma delta T cells. These results indicate that the major subset of human gamma delta T cells can be polarized into either Th1 or Th2 cytokine pattern depending on the cytokine milieu in which contact with antigen occurs.