HLA-class I-specific inhibitory receptors in HIV-1 infection

Persons who inject drugs (PWID) retain functional NK cells, dendritic cell stimulation, and adaptive immune recall responses despite prolonged opioid use

Previous literature suggests that acute opioid use results in the functional impairment of the immune response, thereby decreasing resistance to viral infection. Here, we assessed if innate and adaptive immune responses are compromised ex vivo in persons who inject drugs (PWID) and whether long-term injection drug use may impact host susceptibility to in vitro HIV infection. We measured the frequency, activation state, and functional profile of NK cells, dendritic cells, and CD4+ and CD8+ T cells in low-risk PWID who do not share needles, high-risk needle-sharing PWID, and control donors who did not inject drugs. We also assessed plasma levels of inflammatory markers and CD4+ T cell susceptibility to HIV infection. We observed a significant increase in the amount of sCD14 (P = 0.0023, n = 16) and sCD163 (P = 0.0001, n = 16) in the plasma of PWID compared to controls. Evidence of constitutive activation was noted in PWID as compared to controls with increased CD69 expression in CD56dim NK cells (P = 0.0103, n = 26) and increased CD38 and HLA-DR expression in CD4+ T cells (P = 0.0355, n = 23). However, no innate or adaptive functional differences were detected between PWID and controls, including: NK cell direct or antibody-dependent cellular cytotoxicity poly-functional response, TLR-stimulated dendritic cell/NK crosstalk, CD8+ T cell response to Staphylococcal enterotoxin B or CMV/EBV/FLU peptides, or constitutive or anti-CD3/CD28-stimulated CD4+ T cell infectivity with CCR5-tropic or CXCR4-tropic HIV-1 isolates. Our data indicate that PWID who utilize opioids over as prolonged time frame can retain a functional ex vivo immune response without a measurable increase in CD4+ T cell infectivity suggesting that leukocytes from PWID are not intrinsically more susceptibility to infection with HIV than non-PWID controls.

Parameters predicting COVID-19-induced myocardial injury and mortality

Clinical manifestations of COVID-19 affect many organs, including the heart. Cardiovascular disease is a dominant comorbidity and prognostic factors predicting risk for critical courses are highly needed. Moreover, immunomechanisms underlying COVID-induced myocardial damage are poorly understood.

OBJECTIVE

To elucidate prognostic markers to identify patients at risk.

RESULTS

Only patients with pericardial effusion (PE) developed a severe disease course, and those who died could be identified by a high CD8/Treg/monocyte ratio. Ten out of 19 COVID-19 patients presented with PE, 7 (78%) of these had elevated APACHE-II mortality risk-score, requiring mechanical ventilation. At admission, PE patients showed signs of systemic and cardiac inflammation in NMR and impaired cardiac function as detected by transthoracic echocardiography (TTE), whereas parameters of myocardial injury e.g. high sensitive troponin-t (hs-TnT) were not yet increased. During the course of disease, hs-TnT rose in 8 of the PE-patients above 16 ng/l, 7 had to undergo ventilatory therapy and 4 of them died. FACS at admission showed in PE patients elevated frequencies of CD3⁺CD8⁺ T cells among all CD3+ T-cells, and lower frequencies of Tregs and CD14⁺HLA^-DR⁺-monocytes. A high CD8/Treg/monocyte ratio predicted a severe disease course in PE patients, and was associated with high serum levels of antiviral cytokines. By contrast, patients without PE and PE patients with a low CD8/Treg/monocyte ratio neither had to be intubated, nor died.

CONCLUSIONS

PE predicts cardiac injury in COVID-19 patients. Therefore, TTE should be performed at admission. Immunological parameters for dysfunctional antiviral immunity, such as the CD8/Treg/monocyte ratio used here, supports risk assessment by predicting poor prognosis.

Effect of recombinant cytokines on the expression of natural killer cell receptors from patients with TB or/and HIV infection

BACKGROUND

NK cells express several specialized receptors through which they recognize and discriminate virally-infected/tumor cells efficiently from healthy cells and kill them. This ability to lyse is regulated by an array of inhibitory or activating receptors. The present study investigated the frequency of various NK receptors expressed by NK cell subsets from HIV-infected TB patients. The effect of IL-15+IL-12 stimulation on the expression of NK receptors was also studied.

METHODOLOGY/PRINCIPAL FINDINGS

The study included 15 individuals each from normal healthy subjects, pulmonary tuberculosis patients, HIV-infected individuals and patients with HIV and tuberculosis co-infection. The expression of NK cell receptors was analyzed on two NK cell subsets within the peripheral blood: CD16+CD3- and CD56+CD3- using flow cytometry. The expression of inhibitory receptors (CD158a, CD158b, KIRp70, CD85j and NKG2A) on NK subsets was increased in HIV, when compared to NHS. But the response in HIV-TB was not uniform. Stimulation with IL-15+IL-12 dropped (p<0.05) the expression of CD85j and NKG2A in HIV. The basal expression of natural cytotoxicity receptors (NKp30 and NKp46) on NK cell subsets was lowered (p<0.05) in HIV and HIV-TB as compared to NHS. However, the expression of NKp44 and NKG2D was elevated in HIV. Enhanced NKp46 and NKG2D expression was observed in HIV with IL-15+IL-12 stimulation. The coreceptor NKp80 was found to be expressed in higher numbers on NK subsets from HIV compared to NHS, which elevated with IL-15+IL-12 stimulation. The expression of NK receptors and response to stimulation was primarily on CD56+CD3- subset.

CONCLUSIONS/SIGNIFICANCE

IL-15+IL-12 has an immunomodulatory effect on NK cell subsets from HIV-infected individuals viz down-regulation of iNKRs, elevation of activatory receptors NKp46 and NKG2D, and induction of coreceptor NKp80. IL-15+IL-12 is not likely to be of value when co-infected with TB probably due to the influence of tuberculosis.

HLA associations with nasopharyngeal carcinoma

Several associations have been described between the frequency of human leukocyte antigen (HLA) class I genes in certain populations and the risk of developing nasopharyngeal carcinoma (NPC). Associations between ethnic background and geographic distribution, and relative disease incidence have been reported. Populations in geographical areas at higher risk of developing NPC display HLA distribution patterns different and sometimes opposite from areas of low incidence, whereas populations in areas with intermediate incidence display a totally independent pattern. Two main reasons may explain this association between HLA phenotype distribution and the risk of developing NPC in various populations. First, given the fact that expression of Epstein-Barr Virus (EBV) proteins by cancer cells is tightly linked with NPC development, HLA may influence the development of NPC by modulating the expression of EBV proteins. This explanation is, however, based primarily on theoretical assumptions given that no clear definition of HLA binding pattern of EBV epitopes has been directly shown to significantly alter the recognition of EBV proteins and the risk of developing the disease. Alternatively, HLA may represent a genetic marker flagging the presence of a NPC predisposition locus in close linkage disequilibrium with the HLA class I region. A critical review of known HLA associations in various geographical areas and their interpretation will be presented in this review.

Antiviral NK cell responses in HIV infection: II. viral strategies for evasion and lessons for immunotherapy and vaccination

As is the case in other viral infections, humans respond to HIV infection by activating their NK cells. However, the virus uses several strategies to neutralize and evade the host's NK cell responses. Consequently, it is not surprising that NK cell functions become compromised in HIV-infected individuals in early stages of the infection. The compromised NK cell functions also adversely affect several aspects of the host's antiviral adaptive immune responses. Researchers have made significant progress in understanding how HIV counters NK cell responses of the host. This knowledge has opened new avenues for immunotherapy and vaccination against this infection. In the first part of this review article, we gave an overview of our current knowledge of NK cell biology and discussed how the genes encoding NK cell receptors and their ligands determine innate genetic resistance/susceptibilty of humans against HIV infections and AIDS. In this second part, we discuss NK cell responses, viral strategies to counter these responses, and finally, their implications for anti-HIV immunotherapy and vaccination.

Expression and function of NKG2D in CD4+ T cells specific for human cytomegalovirus

The human NKG2D killer lectin-like receptor (KLR) is coupled by the DAP10 adapter to phosphoinositide 3-kinase (PI3 K) and specifically interacts with different stress-inducible molecules (i.e. MICA, MICB, ULBP) displayed by some tumour and virus-infected cells. This KLR is commonly expressed by human NK cells as well as TCRgammadelta(+) and TCRalphabeta(+)CD8(+) T lymphocytes, but it has been also detected in CD4(+) T cells from rheumatoid arthritis and cancer patients. In the present study, we analysed NKG2D expression in human cytomegalovirus (HCMV)-specific CD4(+) T lymphocytes. In vitro stimulation of peripheral blood mononuclear cells (PBMC) from healthy seropositive individuals with HCMV promoted variable expansion of CD4(+)NKG2D(+) T lymphocytes that coexpressed perforin. NKG2D was detected in CD28(-) and CD28(dull )subsets and was not systematically associated with the expression of other NK cell receptors (i.e. KIR, CD94/NKG2 and ILT2). Engagement of NKG2D with specific mAb synergized with TCR-dependent activation of CD4(+) T cells, triggering proliferation and cytokine production (i.e. IFN-gamma and TNF-alpha). Altogether, the data support the notion that NKG2D functions as a prototypic costimulatory receptor in a subset of HCMV-specific CD4(+) T lymphocytes and thus may have a role in the response against infected HLA class II(+) cells displaying NKG2D ligands.

Virus fitness: concept, quantification, and application to HIV population dynamics

Viral fitness has been broadly studied during the past three decades, mainly to test evolutionary models and population theories difficult to analyze and interpret with more complex organisms. More recent studies, however, are focused in the role of fitness on viral transmission, pathogenesis, and drug resistance. Here, we used human immunodeficiency virus (HIV) as one of the most relevant models to evaluate the importance of viral quasispecies and fitness in HIV evolution, population dynamics, disease progression, and potential clinical implications.

The impact of variation at the KIR gene cluster on human disease

Leukocyte behavior is controlled by a balance of inhibitory and stimulatory signals generated on ligand binding to a complex set of receptors located on the cell surface. The killer cell immunoglobulin-like receptor (KIR) genes encode one such, family of receptors expressed by natural killer (NK) cells, key components of the innate immune system that participate in early responses against infected or transformed cells through production of cytokines and direct cytotoxicity. KIRs are also expressed on a subset of T cells, where they contribute to the intensity of acquired immune responses. Recognition of self HLA class I ligands by inhibitory KIR allows NK cells to identify normal cells, preventing an NK cell-mediated response against healthy autologous cells. Activation of NK cells through stimulatory receptors is directed toward cells with altered expression of class I, a situation characteristic of some virally infected cells and tumor cells. The "missing self" model for NK cell activation was proposed to explain killing of cells that express little or no class I, while cells expressing normal levels of class I are spared. Studies performed over the last several years have revealed extensive diversity at the KIR gene locus, which stems from both its polygenic (variable numbers of genes depending on KIR haplotype) and multiallelic polymorphism. Given the role of KIR in both arms of the immune response, their specificity for HLA class I allotypes, and their extensive genomic diversity, it is reasonable to imagine that KIR gene variation affects resistance and susceptibility to the pathogenesis of numerous diseases. Consequently, the evolution of KIR locus diversity within and across populations may be a function of disease morbidity and mortality. Here we review a growing body of evidence purporting the influence of KIR polymorphism in human disease.

CD8 T cells expressing NK associated receptors are increased in melanoma patients and display an effector phenotype

CD8+ T cells can express NK-associated receptors (NKRs) that may regulate their cytolytic function. We have characterized the expression of several NKRs on peripheral blood CD8+ T cells from melanoma patients and compared them to age-matched healthy donors. The analysis performed includes HLA class I specific receptors (KIRs, LILRB1 and CD94/NKG2) and other NK receptors like CD57, CD56 and CD16. Melanoma patients showed a higher variability in the expression of NKRs on circulating CD8+ T cells than age-matched healthy donors. NKR expression on CD8+ T cells from melanoma patients showed a significant increase of KIR2DL2/L3/S2 (mAb gl183), CD244, CD57, CD56 and CD16. We have also found an increase of CD8+ CD28- CD27- T cells in melanoma patients. This subset represents terminally differentiated effector cells expressing CD244 and high levels of perforin. The expression of NKRs was also mainly restricted to this T cell subset. Altogether, circulating CD8+ T cells from melanoma patients display a distinct phenotype characterized by downregulation of costimulatory molecules and higher expression of NKRs. We suggest that the increased expression of NKRs on T cells may contribute to the final outcome of the immune response against melanoma both stimulating or inhibiting activation and differentiation to effector cells. Blocking inhibitory receptor function and enhancing activating receptors may represent new strategies with therapeutic potential against melanoma.

The CD94/NKG2C killer lectin-like receptor constitutes an alternative activation pathway for a subset of CD8+ T cells

The CD94/NKG2C killer lectin-like receptor (KLR) specific for HLA-E is coupled to the KARAP/DAP12 adapter in a subset of NK cells, triggering their effector functions. We have studied the distribution and function of this KLR in T lymphocytes. Like other NK cell receptors (NKR), CD94/NKG2C was predominantly expressed by a CD8(+) T cell subset, though TCRgammadelta(+) NKG2C(+) and rare CD4(+) NKG2C(+) cells were also detected in some individuals. Coculture with the 721.221 HLA class I-deficient lymphoma cell line transfected with HLA-E (.221-AEH) induced IL-2Ralpha expression in CD94/NKG2C+ NK cells and a minor subset of CD94/NKG2C(+) T cells, promoting their proliferation; moreover, a similar response was triggered upon selective engagement of CD94/NKG2C with a specific mAb. CD8(+) TCRalphabeta CD94/NKG2C(+) T cell clones, that displayed different combinations of KIR and CD85j receptors, expressed KARAP/DAP12 which was co-precipitated by an anti-CD94 mAb. Specific engagement of the KLR triggered cytotoxicity and cytokine production in CD94/NKG2C(+) T cell clones, inducing as well IL-2Ralpha expression and a proliferative response. Altogether these results support that CD94/NKG2C may constitute an alternative T cell activation pathway capable of driving the expansion and triggering the effector functions of a CTL subset.

Imprint of human cytomegalovirus infection on the NK cell receptor repertoire

Expression of the activating CD94/NKG2C killer lectin-like receptor (KLR) specific for HLA-E was analyzed in peripheral blood lymphocytes (PBLs) from healthy adult blood donors; the expression of other natural killer (NK) cell receptors (ie, CD94/NKG2A, KIR, CD85j, CD161, NKp46, NKp30, and NKG2D) was also studied. Human cytomegalovirus (HCMV) infection as well as the HLA-E and killer immunoglobulin-like receptor (KIR) genotypes were considered as potentially relevant variables associated with CD94/NKG2C expression. The proportion of NKG2C(+) lymphocytes varied within a wide range (<0.1% to 22.1%), and a significant correlation (r = 0.83; P < .001) between NKG2C(+) NK and T cells was noticed. The HLA-E genotype and the number of activating KIR genes of the donors were not significantly related to the percentage of NKG2C(+) lymphocytes. By contrast, a positive serology for HCMV, but not for other herpesviruses (ie, Epstein-Barr and herpes simplex), turned out to be strongly associated (P < .001) with increased proportions of NKG2C(+) NK and T cells. Remarkably, the CD94/NKG2C(+) population expressed lower levels of natural cytotoxicity receptors (NCRs) (ie, NKp30, NKp46) and included higher proportions of KIR(+) and CD85j(+) cells than CD94/NKG2A(+) cells. Altogether, these data support that HCMV infection selectively shapes the natural killer cell receptor (NKR) repertoire of NK and T cells from healthy carrier individuals.

Association between HLA classⅡgenes and severity of chronic hepatitis B

AIM: To investigate the association between the polymorphism of HLA -DRB1, -DQA1 and -DQB1 alleles and severity of chronic hepatitis B.

METHODS: HLA-DRB1, -DQA1 and -DQB1 alleles in 54 patients with chronic hepatitis B and 32 patients with chronic severe hepatitis B were analyzed by using polymerase chain reaction/sequence specific primer (PCR/SSP) technique.

RESULTS: The frequency of HLA-DRB1*1 001 allele in the chronic severe hepatitis B group was markedly higher than that in the chronic hepatitis B group (14.1% vs 1.9%, x² = 19.2997, Pc = 0.0281, RR = 9.78). No significant different allele frequencies of HLA-DQA1 and HLA-DQB1 alleles were observed between the chronic severe hepatitis B group and the chronic hepatitis B group.

CONCLUSION: HLA-DRB1*1 001 is closely associated with the severity of chronic hepatitis B, and may be a valuble marker of evaluating the prognosis of patients with chronic hepatitis B.

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.

Interleukin-10 induces the upregulation of the inhibitory receptor ILT4 in monocytes from HIV positive individuals

A characteristic of human immunodeficiency virus infected individuals is an impairment of immune responses, which can result in opportunistic infections. Elevated levels of interleukin-10 (IL-10), produced by virally infected monocytes, are found in the sera of HIV infected individuals. Such elevated levels have been associated with the impaired function of CD4(+) and CD8(+) T cells, and antigen presenting cells (APC), such as monocytes. IL-10 has been reported to upregulate the cell surface expression of the inhibitory receptors ILT3 and ILT4 on monocytes and dendritic cells. This study demonstrates that the decreased antigen presenting ability of monocytes in HIV(+) individuals is in part due to the upregulation of ILT4 on the monocytes caused by the elevated serum IL-10 levels seen in these individuals.

The gp49B1 inhibitory receptor regulates the IFN-gamma responses of T cells and NK cells

The magnitude and diversity of Ag-specific T cell effector activity have been proposed to be controlled by an integration of positive signals transduced by the TCR and negative signals originating from inhibitory cell surface molecules. Although the lectin family of NK cell-associated inhibitory receptors has been reported to regulate the function of murine CTLs, gp49B1, the Ig superfamily member is not known to be expressed on T cells. Moreover, the consequences of the lack of an endogenously expressed NK cell-associated inhibitory receptor on T cell functions are not known. We report that gp49B1 is expressed by nearly all activated CD8 and CD4 T cells in addition to NK cells during an immune response to viral, bacterial, or tumor challenge. Kinetics of gp49B1 expression parallel functional capability and subside in the memory phase. Following vaccinia viral infection, IFN-gamma production by both subsets of T cells and NK cells is enhanced in gp49B1-deficient mice compared with gp49B1(+/+) mice. The stimulation threshold for IFN-gamma production is also lower in gp49B1-deficient T cells. In contrast, no significant differences were observed in the cytotoxic responses. We conclude that gp49B1 is a unique inhibitory receptor that is induced in multiple lineages of innate and adaptive immune cells during an infection and controls their IFN-gamma, but not cytotoxic responses.

NK cell receptors in antiviral immunity

An array of inhibitory and activating receptors initially identified on NK cells are also expressed by conventional CD8+ alphabeta T cells. New evidence strongly implicates these 'NK cell receptors' in modulating NK cell and virus-specific CD8+ T cell responses against a variety of viral infections. Precise regulation of NK cell and T cell responses by these receptors optimizes antiviral immunity while preventing immunological bystander pathology and autoimmunity.

Structure and function of major histocompatibility complex (MHC) class I specific receptors expressed on human natural killer (NK) cells

Natural killer (NK) cells express receptors that are specific for MHC class I molecules. These receptors play a crucial role in regulating the lytic and cytokine expression capabilities of NK cells. In humans, three distinct families of genes have been defined that encode for receptors of HLA class I molecules. The first family identified consists of type I transmembrane molecules belonging to the immunoglobulin (Ig) superfamily and are called killer cell Ig-like receptors (KIR). A second group of receptors belonging to the Ig superfamily, named ILT (for immunoglobulin like transcripts), has more recently been described. ILTs are expressed mainly on B, T and myeloid cells, but some members of this group are also expressed on NK cells. They are also referred to as LIRs (for leukocyte Ig-like receptor) and MIRs (for macrophage Ig-like receptor). The ligands for the KIR and some of the ILT receptors include classical (class Ia) HLA class I molecules, as well as the nonclassical (class Ib) HLA-G molecule. The third family of HLA class I receptors are C-type lectin family members and are composed of heterodimers of CD94 covalently associated with a member of the NKG2 family of molecules. The ligand for most members is the nonclassical class I molecule HLA-E. NKG2D, a member of the NKG2 family, is expressed as a homodimer, along with the adaptor molecule DAP10. The ligands of NKG2D include the human class I like molecules MICA and MICB, and the recently described ULBPs. Each of these three families of receptors has individual members that can recognize identical or similar ligands yet signal for activation or inhibition of cellular functions. This dichotomy correlates with particular structural features present in the transmembrane and intracytoplasmic portions of these molecules. In this review we will discuss the molecular structure, specificity, cellular expression patterns, and function of these HLA class I receptors, as well as the chromosomal location and genetic organization.

NK-associated receptors on CD8 T cells from treatment-naive HIV-infected individuals: defective expression of CD56

OBJECTIVES

This study addresses the detailed expression of natural killer (NK)- associated receptors on CD8 T lymphocytes in treatment-naive HIV-infected individuals.

DESIGN

Experimental study analysing the expression of NK-associated receptors on peripheral blood T lymphocytes from HIV-infected individuals compared with healthy controls.

METHODS

Flow cytometry was used to analyse the expression of CD56, CD16, CD94, NKG2A, NKB1, CD161, CD244, and perforin, according to the CD28 phenotype, on CD8(bright) T cells obtained from treatment-naive HIV-infected individuals and from healthy controls.

RESULTS

The results showed that CD8(bright) T cells from treatment-naive HIV-infected individuals had a decreased expression of CD56 and that CD8(bright)CD56 cell numbers correlated with CD4 cell counts. NK-associated markers were preferentially expressed on CD8(bright)CD28 negative T cells, both in healthy controls and HIV-infected individuals. An increased expression of CD94, CD244, and perforin, which was the consequence of the expansion of the CD8(bright)CD28 negative T-cell subset, was also observed in HIV infection.

CONCLUSIONS

As the CD8(bright)CD56 T cells are the mature cytolytic effector cells, the defective expression of CD56 on CD8(bright) T cells shown in HIV-infected individuals could be involved in the decreased peripheral blood T-cell cytotoxicity found in HIV infection.

Allogeneic MHC class I ligands and their role in positive and negative regulation of human cytotoxic effector cells

The allogeneic mixed lymphocyte culture (MLC) has served as an important experimental system for elucidating the cellular and molecular basis of human lymphocyte responses. Complex mixtures of lymphocytes are stimulated by disparate alloantigens, inducing cellular activation and generating a cytokine milieu that is an excellent breeding ground for the proliferation and differentiation of many distinct lymphocyte subsets. Cloning of individual lymphocytes following alloactivation has allowed various cytotoxic lymphocytes to be isolated and characterized with respect to phenotype and specificity. These analyses have revealed that all types of cytotoxic effector cells are regulated by interactions with MHC-peptide ligands, however, the consequences of these interactions can result in opposite functional outcomes. In this review we summarize how allogeneic MHC class I-peptide ligands positively or negatively regulate the activities of four distinct groups of cytotoxic lymphocytes and how this information might be transferred into clinical use.

Identification of human immunodeficiency virus type 1 subtype C Gag-, Tat-, Rev-, and Nef-specific elispot-based cytotoxic T-lymphocyte responses for AIDS vaccine design

The most severe human immunodeficiency virus type 1 (HIV-1) epidemic is occurring in southern Africa. It is caused by HIV-1 subtype C (HIV-1C). In this study we present the identification and analysis of cumulative cytotoxic T-lymphocyte (CTL) responses in the southern African country of Botswana. CTLs were shown to be an important component of the immune response to control HIV-1 infection. The definition of optimal and dominant epitopes across the HIV-1C genome that are targeted by CTL is critical for vaccine design. The characteristics of the predominant virus that causes the HIV-1 epidemic in a certain geographic area and also the genetic background of the population, through the distribution of common HLA class I alleles, might impact dominant CTL responses in the vaccinee and in the general population. The enzyme-linked immunospot (Elispot) gamma interferon assay has recently been shown to be a reliable tool to map optimal CTL epitopes, correlating well with other methods, such as intracellular staining, tetramer staining, and the classical chromium release assay. Using Elispot with overlapping synthetic peptides across Gag, Tat, Rev, and Nef, we analyzed HIV-1C-specific CTL responses of HIV-1-infected blood donors. Profiles of cumulative Elispot-based CTL responses combined with diversity and sequence consensus data provide an additional characterization of immunodominant regions across the HIV-1C genome. Results of the study suggest that the construction of a poly-epitope subtype-specific HIV-1 vaccine that includes multiple copies of immunodominant CTL epitopes across the viral genome, derived from predominant HIV-1 viruses, might be a logical approach to the design of a vaccine against AIDS.

Dressed to kill? A review of why antiviral CD8 T lymphocytes fail to prevent progressive immunodeficiency in HIV-1 infection

CD8 T cells play an important role in protection and control of HIV-1 by direct cytolysis of infected cells and by suppression of viral replication by secreted factors. However, although HIV-1-infected individuals have a high frequency of HIV-1-specific CD8 T cells, viral reservoirs persist and progressive immunodeficiency generally ensues in the absence of continuous potent antiviral drugs. Freshly isolated HIV-specific CD8 T cells are often unable to lyse HIV-1-infected cells. Maturation into competent cytotoxic T lymphocytes may be blocked during the initial encounter with antigen because of defects in antigen presentation by interdigitating dendritic cells or HIV-infected macrophages. The molecular basis for impaired function is multifactorial, due to incomplete T-cell signaling and activation (in part related to CD3zeta and CD28 down-modulation), reduced perforin expression, and inefficient trafficking of HIV-specific CD8 T cells to lymphoid sites of infection. CD8 T-cell dysfunction can partially be corrected in vitro with short-term exposure to interleukin 2, suggesting that impaired HIV-specific CD4 T helper function may play a significant causal or exacerbating role. Functional defects are qualitatively different and more severe with advanced disease, when interferon gamma production also becomes compromised.

Expression and function of NK cell receptors in CD8+ T cells

A wide variety of inhibitory and stimulatory NK cell receptors are expressed by some CD8+ cytotoxic T lymphocytes in mice and humans. Recent data address the induction of these receptors on activated or memory CD8+ T cells and have led to hypotheses addressing their function in the CD8+ T cell response.

Differential disappearance of inhibitory natural killer cell receptors during HAART and possible impairment of HIV-1-specific CD8 cytotoxic T lymphocytes

BACKGROUND

Highly active antiretroviral therapy (HAART) is associated with a decrease in viral replication to undetectable levels and with an increase in CD4 T lymphocytes. Residual HIV-1 replication occurs together with incomplete recovery of cytotoxic CD8 T lymphocyte (CTL) numbers and function. We sought to determine whether expression of HLA class I-specific inhibitory natural killer receptors (iNKR) on the CTL of patients who had been treated successfully with HAART for 24 months could be involved, at least in part, in residual CTL functional inhibition.

METHODS

Two-colour cytofluorometry was used to analyse the expression of six different iNKR including p58.1, p58.2, p70, p140, CD94/NKG2A and LIR1/ILT2 on the CD3, CD8 lymphocytes of eight patients with successful long-term suppression of viral replication before and after 3, 6 and 24 months of HAART. Healthy subjects were analysed as controls. HIV-1-specific cytotoxic activity was determined after 24 months of HAART in the presence and absence of iNKR-masking.

RESULTS

No significant reduction of iNKR expression on CD8 T cells was observed by 6 months. Expression of p70 and p140 was inversely correlated with the increasing CD4 numbers. After 24 months CD8 T-lymphocytes expressing p58.1, p58.2, p70, p140 and CD94/NKG2A returned to levels indistinguishable from those of the healthy controls. A significantly increased proportion of CD8 CTL still expressed LIR1/ILT2, a receptor with broad HLA-class I specificity. Functional analysis of freshly separated cells revealed that the disruption of the interaction between LIR1/ILT2 and HLA-class I could partly restore HIV-1-specific lysis.

CONCLUSIONS

A decrease in CD3CD8iNKR cells is observed beyond 6 months of HAART. In some patients functional impairment due to LIR1/ILT2 expression may persist even after 24 months of successful HAART.