Distribution of the natural killer-related receptor for HLA-C during highly active antiretroviral therapy for human immunodeficiency virus infection

Editorial to the Special Issue "Clinical Immunology in Italy, with Special Emphasis to Primary and Acquired Immunodeficiencies: A Commemorative Issue in Honor of Prof. Fernando Aiuti"

Fernando Aiuti (Figure 1), born in Urbino on 8 June 1935, suddenly died on 9 January 2019, leaving a great void not only among his family members and those who knew him and appreciated his great humanity and acute intelligence, but in the entire immunological scientific community [...].

Natural killer cells in HIV-1 infection and therapy

: Natural killer (NK) cells are important effectors of innate immunity playing a key role in the eradication and clearance of viral infections. Over the recent years, several studies have shown that HIV-1 pathologically changes NK cell homeostasis and hampers their antiviral effector functions. Moreover, high levels of chronic HIV-1 viremia markedly impair those NK cell regulatory features that normally regulate the cross talks between innate and adaptive immune responses. These pathogenic events take place early in the infection and are associated with a pathologic redistribution of NK cell subsets that includes the expansion of anergic CD56/CD16 NK cells with an aberrant repertoire of activating and inhibitory receptors. Nevertheless, the presence of specific haplotypes for NK cell receptors and the engagement of NK cell antibody-dependent cell cytotocity have been reported to control HIV-1 infection. This dichotomy can be extremely useful to both predict the clinical outcome of the infection and to develop alternative antiviral pharmacological approaches. Indeed, the administration of antiretroviral therapy in HIV-1-infected patients restores NK cell phenotype and functions to normal levels. Thus, antiretroviral therapy can help to develop NK cell-directed therapeutic strategies that include the use of broadly neutralizing antibodies and toll-like receptor agonists. The present review discusses how our current knowledge of NK cell pathophysiology in HIV-1 infection is being translated both in experimental and clinical trials aimed at controlling the infection and disease.

Human Leukocyte Antigen (HLA) and Immune Regulation: How Do Classical and Non-Classical HLA Alleles Modulate Immune Response to Human Immunodeficiency Virus and Hepatitis C Virus Infections?

The genetic factors associated with susceptibility or resistance to viral infections are likely to involve a sophisticated array of immune response. These genetic elements may modulate other biological factors that account for significant influence on the gene expression and/or protein function in the host. Among them, the role of the major histocompatibility complex in viral pathogenesis in particular human immunodeficiency virus (HIV) and hepatitis C virus (HCV), is very well documented. We, recently, added a novel insight into the field by identifying the molecular mechanism associated with the protective role of human leukocyte antigen (HLA)-B27/B57 CD8+ T cells in the context of HIV-1 infection and why these alleles act as a double-edged sword protecting against viral infections but predisposing the host to autoimmune diseases. The focus of this review will be reexamining the role of classical and non-classical HLA alleles, including class Ia (HLA-A, -B, -C), class Ib (HLA-E, -F, -G, -H), and class II (HLA-DR, -DQ, -DM, and -DP) in immune regulation and viral pathogenesis (e.g., HIV and HCV). To our knowledge, this is the very first review of its kind to comprehensively analyze the role of these molecules in immune regulation associated with chronic viral infections.

Natural killer cell responses to HIV-1 peptides are associated with more activating KIR genes and HLA-C genes of the C1 allotype

BACKGROUND

What characterizes individuals whose natural killer (NK) cells are able to respond to HIV-1 peptides is not known.

METHODS

The association between NK cell responses and KIR gene profiles and HLA-B and HLA-C alleles was investigated among 76 HIV-1-infected women in South Africa previously categorized as responders (n = 39) or nonresponders (n = 37) to HIV-1 peptide pools in a whole blood intracellular cytokine assay. Viral load was significantly lower and CD4 T-cell counts higher among responders compared with nonresponders (P = 0.023 and P = 0.030, respectively).

RESULTS

Possession of one HLA-C1 allele associated with increased magnitude of NK cell responses to Env (P = 0.031) and significantly decreased viral load (P = 0.027) compared with its absence. There was a trend to increased possession of KIR2DL3+HLA-C1 in responders (71.8% vs 51.4%, P = 0.098) and decreased possession of KIR2DL3/2DL3+C2C2 (2.6% vs 16.2%, P = 0.053). A total of 64.1% of responders versus 32.4% of nonresponders had 13 or more KIR genes (P = 0.0067). Notably, the 13-KIR gene containing the Bx21 genotype (has eight inhibitory and three activating genes KIR2DS2, 2DS4, 2DS5) showed substantially higher representation among the responders (28.2% vs 2.6%, P = 0.001). A significantly higher proportion of responders had both KIR2DS2 and KIR2DS5 compared with either gene alone (72.4% vs 37%; P = 0.015). At least one HLA-C1 allele together with 13 or more KIR genes was associated with NK cell responsiveness (48.7% vs 13.5%; P = 0.001).

CONCLUSION

NK cell responses to HIV-1 peptides are more likely to occur among individuals with a genotype supporting a more activating NK cell phenotype and who possess at least one HLA-C1 allele.

Natural killer cells that respond to human immunodeficiency virus type 1 (HIV‐1) peptides are associated with control of HIV‐1 infection

Human immunodeficiency virus (HIV)-specific natural killer (CD3- cells), CD4, and CD8 T cellular responses were determined in 79 HIV‐1-infected women in response to HIV‐1 peptide pools (Gag, Pol, Nef, Reg, and Env) with use of a whole‐blood intracellular cytokine staining assay that measures interferon-γ and/or interleukin-2. HIV‐specific CD3- cell responses to any region (Env and Reg predominantly targeted) were associated with lower viral load (P = .031) and higher CD4 T cell count (P = .015). Env‐specific CD3- cell responses were stronger in women who had both Gag CD4 and CD8 T cell responses and, in turn, was associated with lower viral load (P = .005). CD3- cell responders had significantly higher representation of CD4 T cell responses to Env and Reg (P = .012 and P = .015, respectively) and higher magnitudes of CD4 T cell responses (P = .017 and P = .037, respectively) than did nonresponders. Peptide‐specific natural killer cells are associated with markers of less severe disease progression among HIV‐1-infected women (lower viral load and higher CD4 T cell count) and with stronger HIV‐specific T cell responses.

T-cell dysfunction in HIV-1 infection: targeting the inhibitors

Since AIDS emerged almost three decades ago, there have been considerable advances in the field of antiretroviral chemotherapy for those chronically infected with HIV-1. However, this therapy is noncurative and as our understanding of HIV-1 immunopathogenesis increases, it is becoming apparent that further therapeutic interventions are required to reverse the devastating effects of HIV-1 infection worldwide. While viral clearance remains the principle goal of HIV-1 treatment, this article describes immunotherapeutic options that target the immunological effects of the virus, to reduce its presence in the body and counteract viral-induced T-cell dysfunction and inhibition. Such approaches may augment existing antiretroviral therapy to overturn virus-induced T-cell anergy in the infected host, improving levels of immune control that reduce viremia and decrease the rate of transmission.

Matrix metalloprotease inhibitors restore impaired NK cell-mediated antibody-dependent cellular cytotoxicity in human immunodeficiency virus type 1 infection

Increasing evidence suggests that NK cells not only are critical in the initial host defense against pathogens but also may contribute to continued protection from human immunodeficiency virus type 1 (HIV-1) disease progression. NK cell cytolysis can be induced directly through diverse receptor families or can be induced indirectly through Fc receptors by antibodies mediating antibody-dependent cellular cytotoxicity (ADCC). ADCC has been implicated in both protection from simian immunodeficiency virus infection and slower progression of HIV-1 disease. ADCC activity declines with advancing infection, and yet the underlying mechanism for this dysfunction has not been defined, nor has it been determined whether the activity can be reconstituted. Here we demonstrate that NK cell-mediated ADCC is severely compromised in chronic HIV infection. The potency of ADCC function was directly correlated with baseline Fc gammaRIIIa receptor (CD16) expression on NK cells. CD16 expression was negatively influenced by elevated expression of a group of enzymes, the matrix metalloproteinases (MMPs), normally involved in tissue/receptor remodeling. Inhibition of MMPs resulted in increased CD16 expression and augmented ADCC activity in response to antibody-coated target cells. These data suggest that MMP inhibitors may improve NK cell-mediated ADCC, which may provide subjects with an opportunity to harness the cytolytic power of NK cells through naturally occurring nonneutralizing HIV-specific antibodies.

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.

Detection of KIR3DS1 on the Cell Surface of Peripheral Blood NK Cells Facilitates Identification of a Novel Null Allele and Assessment of KIR3DS1 Expression during HIV-1 Infection

KIR3DL1 is a highly polymorphic killer cell Ig-like receptor gene with at least 23 alleles described, including its activating counterpart, KIR3DS1. Recently, the KIR3DS1 allele has been shown to slow progression to AIDS in individuals expressing HLA-Bw4 with isoleucine at position 80. However, due to the lack of a specific Ab, KIR3DS1 expression and function is not well characterized. In this study, we demonstrate KIR3DS1 expression on a substantial subset of peripheral natural killer cells through its recognition by the mAb Z27. The fidelity of this detection method was confirmed by analysis of KIR3DS1 transfectants and the identification of a novel KIR3DS1 null allele. Interestingly, KIR3DS1 is also expressed by a small proportion of CD56(+) T cells. We show that ligation of KIR3DS1 by Z27 leads to NK cell IFN-gamma production and degranulation as assessed by expression of CD107a. Furthermore, we document the persistence of KIR3DS1(+) NK cells in HIV-1 viremic patients. The high frequency of KIR3DS1 expression, along with its ability to activate NK cells, and its maintenance during HIV-1 viremia are consistent with the epidemiological data suggesting a critical role for this receptor in controlling HIV-1 pathogenesis.

Control of human herpes virus type 8-associated diseases by NK cells

The "natural killer" (NK) cells preferentially kill targets lacking surface major histocompatibility complex class I (MHC-I) molecule expression. NK cells recognize these targets through membrane receptors, which can trigger activating or inhibitory signals for killing. Several tumors or virus-infected cells downregulate MHC-I expression as a mechanism to evade recognition and killing by cytotoxic T lymphocytes (CTL). They, however, become targets for NK cells cytotoxic activity. NK cell activity is reduced during disease progression in human immunodeficiency virus (HIV) infection, and in individuals with AIDS-associated tumors linked with infection by the oncogenic human herpes virus type-8 (HHV8), including Kaposi's sarcoma (KS) and primary effusion lymphomas (PEL). We have demonstrated that AIDS-related KS (AIDS-KS) is characterized by an increased expression of inhibitory receptors by T lymphocytes, and that HIV-non-infected patients with KS (classic KS, C-KS) have a substantial number of NK cells bearing these same receptors. NK cells from patients with C-KS are normally equipped with cytolytic molecules including granzyme A and perforin. However, the cytotoxic activity of NK cells is reduced in patients with C-KS, AIDS-KS, or PEL patients, who are all infected by the HHV8, and this correlates with disease severity. Moreover, we have found that HHV8-infected cell lines established from PELs have a reduced surface expression of MHC-I molecules and are sensitive to the lysis mediated by NK cells. Since PEL cells express the same HHV8 latency program as KS cells, these data point to MHC-I downregulation by HHV8 as a primary immune evasion mechanism against CTL responses, further reinforced by upregulation of inhibitory receptors on T and NK cells in the setting of HIV and/or HHV8 infection. Thus, studies on killing receptor regulation and signaling in T and NK cells may shed light on the pathogenesis of HHV8-associated tumors both in HIV-infected or -noninfected patients.

Distinctive NK-cell receptor repertoires sustain high-level constitutive NK-cell activation in HIV-exposed uninfected individuals

We have previously associated high natural killer (NK)–cell activity and protection against HIV-1 infection in Vietnamese exposed uninfected intravascular drug users (EUs). Considering that activating and inhibitory signals sensed by NK-cell receptors regulate NK-cell activation, we performed phenotypic and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) transcript analyses of the NK-cell receptor (NKR) repertoire in 25 EUs, 19 HIV+ intravenous drug users, and 26 uninfected blood donors. Although NK-cell activation was not linked to a unique NKR repertoire in EUs, various patterns consistent with NK-cell activation were detected in EUs: high KIR3DS1/KIR3DL1 ratio associated with down-regulated KIR3DL1 transcript levels, KIR2DL3+ low-affinity receptor expansion associated to group HLA-C1 ligand in 2DS2−/2DL2− EUs, enhanced NKG2C/NKG2A ratio, and increased CD69 expression. Remarkably, EUs exhibited high constitutive degranulation activity in the absence of exogenous stimulation, as shown by the CD107a assay. Furthermore, CD161 expression was increased within the CD107a+ NK-cell compartment. Our results suggest that in response to viral exposition, particular genetic or regulated features of the NKR repertoire of EUs contribute to their high constitutive NK-cell potential. This might allow NK cells to generate a more rapid and effective immune response to HIV-1, thereby contributing to prevention toward infection.

The CD160+ CD8high cytotoxic T cell subset correlates with response to HAART in HIV-1+ patients

We investigated the circulating cytotoxic CD160+ CD8(high) subset in correlation to antiviral immunity and response to highly active antiretroviral therapy (HAART) in HIV+ subjects. The study included 45 treatment-naive patients receiving HAART for 18 months, retrospectively defined as good (n=29) and transient (n=16) responders. HIV-specific CD8 T lymphocyte levels were measured by IFNgamma production in response to p17 Gag, in the presence of immobilized anti-CD160 mAb. We report a significantly increased baseline level of CD160+ CD8(high) subset in good therapy responders. CD160+ CD8(high) subset correlates with CD4+ T cell count, immune activation, and viral load. CD160+ CD8(high) lymphocytes contain a high amount of Granzyme B and include virus-specific T lymphocytes in HIV-1+ subjects. Co-stimulation through CD160 molecules enhances IFNgamma production in response to p17 Gag. Therefore, the CD160+ CD8(high) subset may be useful for monitoring of virus-specific cellular immunity and predicting response to antiretroviral therapy in chronic HIV-1 infection.

NK cells in HIV infection: Paradigm for protection or targets for ambush

Natural killer cells are a crucial component of the innate immune response to certain tumours and to various viruses, fungi, parasites and bacteria. HIV has infected more than 60 million people worldwide and has led to more than 23 million deaths. At present, there are approximately 40 million people who are living with HIV infection, and there were 5 million new infections in 2004. As part of the innate immune system, natural killer cells might have an important role in host defence against HIV infection, as well as in the control of HIV replication in vivo. In this regard, it is important to understand how natural killer cells and HIV interact. This Review focuses on the role of natural killer cells in controlling HIV infection and on the impact of HIV and HIV-viraemia-induced immune activation on natural-killer-cell function.

Expression of CD158b on Peripheral Blood Lymphocytic Cell After Kidney Transplantation

OBJECTIVE

To investigate the expression of CD158b on peripheral blood lymphocytes after kidney transplantation.

METHODS

Sixty two kidney transplant patients were divided into two groups (normal group and rejection group) according to pathologic results and clinical situation. Blood samples were assessed for percentage of CD3+; CD19+; CD3-CD16/56+; CD3+CD158b+; CD19+CD158b+, and CD3-CD16/56+CD158b+ subsets.

RESULTS

The percentages of CD3+ cells preop as well as at 1 and 7 postoperative and the day acute rejection happened were 60.06 +/- 4.67, 40.43 +/- 4.11, 31.67 +/- 4.04, and 39.21 +/- 5.20, respectively. The percentages of CD3-CD16/56+ were 21.65 +/- 1.79, 33.84 +/- 5.45, 38.10 +/- 4.86, and 39.53 +/- 4.80, respectively. The percentages of CD3+CD158b+ were 1.46 +/- 0.31, 1.88 +/- 0.70, 2.03 +/- 1.04, and 0.65 +/- 0.12, respectively. The percentages of CD3-CD16/56+CD158b+ were 5.87 +/- 1.24, 3.57 +/- 0.57, 2.82 +/- 0.45, and 1.60 +/- 0.33, respectively.

CONCLUSIONS

The percentage of CD3+ cells in the normal and the rejection groups decreased significantly. The percentages of CD158b+T cells decreased significantly after acute rejection. The percentage of CD158b+NK cells decreased significantly after kidney transplantation, decreasing gradually after acute rejection. The percentage of CD158b+ total T cells decreased significantly following acute rejection. The percentage of CD3-CD16/56+CD158b+ of total NK cells decreased significantly after kidney transplantation and after acute rejection. Because few factors interfere with the expression of CD158b on NK cells, monitoring of this marker may be accurate and sensitive.

Loss of the CD56hiCD16- NK cell subset and NK cell interferon-gamma production during antiretroviral therapy for HIV-1: partial recovery by human growth hormone

Previous studies have shown that human natural killer (NK) cells are lost from the periphery and are functionally suppressed during HIV-1 infection, and that the administration of highly active antiretroviral therapy (HAART) results in a recovery of NK cell numbers in HIV-1-infected individuals. However, despite this recovery, interleukin (IL)-2 + IL-12-driven interferon (IFN)-gamma production by NK cells has been shown to remain suppressed after HAART. Here we show that the innate immune factor IL-15 in combination with IL-12 is also unable to recover NK cell IFN-gamma production in HAART-treated individuals. Furthermore, we also demonstrate an imbalance in the distribution of CD56loCD16hi and CD56hiCD16- NK subsets after successful HAART, CD56hiCD16- cells being reduced substantially in HIV-1 patients on HAART. Treatment of patients with combined human growth hormone and antiretroviral therapy resulted in further enhancement in the absolute numbers and the proportion of NK cells in some individuals in the absence of parallel effects on CD4+ T cells. Furthermore, in these individuals HAART with growth hormone resulted in an enhancement of cytokine-driven NK cell activation and IFN-gamma production compared to the HAART-only baseline.

Use of HIV protease inhibitors to block Kaposi's sarcoma and tumour growth

HIV protease inhibitors are antiretroviral drugs that block the enzyme required for production of infectious viral particles. Although these agents have been designed to selectively bind to the catalytic site of HIV protease, evidence indicates that other cellular and microbial enzymes and pathways are also affected. It has been reported that patients treated with highly active anti-retroviral therapy (HAART) containing a protease inhibitor may be at reduced risk of Kaposi's sarcoma (KS) and some types of non-Hodgkin lymphomas; some disease regressions have also been described. Here we review recent data showing that several widely used protease inhibitors, including indinavir, saquinavir, ritonavir, and nelfinavir, can affect important cellular and tissue processes such as angiogenesis, tumour growth and invasion, inflammation, antigen processing and presentation, cell survival, and tissue remodelling. Most of these non-HIV-related effects of protease inhibitors are due to inhibition of cell invasion and matrix metalloprotease activity, or modulation of the cell proteasome and NFkappaB. These elements are required for development of most tumours. Thus, by direct and indirect activities, protease inhibitors can simultaneously block several pathways involved in tumour growth, invasion, and metastasis. These findings indicate that protease inhibitors can be exploited for the therapy of KS and other tumours that occur in both HIV-infected and non-infected individuals. A multicentre phase II clinical trial with indinavir in non-HIV-associated KS is about to start in Italy.

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.