Natural killer cell-mediated lysis of autologous cells modified by gene therapy

Immunoresponse to Gene-Modified Hematopoietic Stem Cells

Gene transfer to and correction of hematopoietic stem cells (HSCs) are ideal strategies to cure a number of congenital and acquired disorders. However, transgene products may trigger immunological rejection of modified cells, limiting their therapeutic benefits. Preclinical and clinical data indicate that myeloablative total body irradiation (TBI) allows for efficient engraftment and tolerance to gene-modified HSCs. In contrast, myeloablative chemotherapy using busulfan or similar agents is only sufficient to induce tolerance to gene-modified HSCs producing no or non-immunogenic protein. If cells are modified to produce a protein that is xenogenic or congenitally absent in the patient, additional immunosuppression may be required to prevent an immunological reaction to the transduced cells. New gene editing and in vivo gene therapy techniques could pose additional immune concerns compared to ex vivo gene therapy methods. This review is intended to guide the design of conditioning and immunosuppression therapy in HSC-targeted gene therapy, as well as gene editing.

Inhibitory natural killer cell receptor KIR3DL1 with its ligand Bw4 constraints HIV-1 disease among South Indians

OBJECTIVE

To investigate the role of genotypic and phenotypic characteristics of killer cell immunoglobulin-like receptors (KIRs) and their human leukocyte antigen (HLA) class-1 ligands in HIV-1 disease progression.

STUDY DESIGN AND METHODS

This is a nested case-control study including 347 HIV seropositive (HIV-1+) individuals from South India constituting 45 long-term nonprogressors (LTNPs) and 302 disease progressors. KIR genotyping was performed by multiplex sequence-specific primer-directed PCR (SSP-PCR). Phenotypic expressions of KIR3DL1/S1 was studied using multiparametric flow cytometry assay. HLA-Bw4 and Bw6 epitopes were determined by ARMS-PCR. HLA-Bw4I80, HLA-Bw4T80, HLA-C1, HLA-C2, and HLA-Aw4 were genotyped using SSP-PCR. Serum levels of IFN-γ was quantified using ELISA method.

RESULTS

Overall, 37 different KIR genotypes were observed and the distribution of genotypes with AB-AB (OR = 2.2, P = 0.033) constellations showed significant increase among LTNPs. The frequencies of 3DL1-2DL3-2DL5 (OR = 2.2, Pc = 0.031), 3DL1-Bw4/Aw4 (OR = 2.49, Pc = 0.019), homozygous Bw4 (OR = 2.422, Pc = 0.011) were observed higher in LTNPs and 2DS1-2DS2-2DS3 (OR =  0.475, Pc = 0.03), homozygous Bw6 (OR = 0.413, Pc = 0.011) were higher in the disease progressors. Flow cytometry assay showed the increased expression and maintenance of 3DL1/S1+NK cells in LTNPs (P = 0.0001). Further the expansion of 3DS1+NK cells was higher than 3DL1+NK cells in the heterozygous 3DL1/S1 LTNPs (P = 0.001).

CONCLUSION

The inhibitory receptor 3DL1 with Bw4 and its A-haplotype defining KIR genes (2DL3/L5) confers protection against HIV-1 disease progression. An increased expression and maintenance of 3DL1/S1+ natural killer cells may contribute to the efficient activation of the natural killer cells and subsequent long-term nonprogression (LTNPn) to the disease.

Peptide-Dependent Recognition of HLA-B*57:01 by KIR3DS1

Killer cell immunoglobulin-like receptors (KIRs) play an important role in the activation of natural killer (NK) cells, which in turn contribute to the effective immune control of many viral infections. In the context of HIV infection, the closely related KIR3DL1 and KIR3DS1 molecules, in particular, have been associated with disease outcome. Inhibitory signals via KIR3DL1 are disrupted by downregulation of HLA class I ligands on the infected cell surface and can also be impacted by changes in the presented peptide repertoire. In contrast, the activatory ligands for KIR3DS1 remain obscure. We used a structure-driven approach to define the characteristics of HLA class I-restricted peptides that interact with KIR3DL1 and KIR3DS1. In the case of HLA-B*57:01, we used this knowledge to identify bona fide HIV-derived peptide epitopes with similar properties. Two such peptides facilitated productive interactions between HLA-B*57:01 and KIR3DS1. These data reveal the presence of KIR3DS1 ligands within the HIV-specific peptide repertoire presented by a protective HLA class I allotype, thereby enhancing our mechanistic understanding of the processes that enable NK cells to impact disease outcome.

IMPORTANCE Natural killer (NK) cells are implicated as determinants of immune control in many viral infections, but the precise molecular mechanisms that initiate and control these responses are unclear. The activating receptor KIR3DS1 in combination with HLA-Bw4 has been associated with better outcomes in HIV infection. However, evidence of a direct interaction between these molecules is lacking. In this study, we demonstrate that KIR3DS1 recognition of HLA-Bw4 is peptide dependent. We also identify HIV-derived peptide epitopes presented by the protective HLA-B*57:01 allotype that facilitate productive interactions with KIR3DS1. Collectively, these findings suggest a mechanism whereby changes in the peptide repertoire associated with viral infection provide a trigger for KIR3DS1 engagement and NK cell activation.

Mutational and structural analysis of KIR3DL1 reveals a lineage-defining allotypic dimorphism that impacts both HLA and peptide sensitivity

Killer Ig-like receptors (KIRs) control the activation of human NK cells via interactions with peptide-laden HLAs. KIR3DL1 is a highly polymorphic inhibitory receptor that recognizes a diverse array of HLA molecules expressing the Bw4 epitope, a group with multiple polymorphisms incorporating variants within the Bw4 motif. Genetic studies suggest that KIR3DL1 variation has functional significance in several disease states, including HIV infection. However, owing to differences across KIR3DL1 allotypes, HLA-Bw4, and associated peptides, the mechanistic link with biological outcome remains unclear. In this study, we elucidated the impact of KIR3DL1 polymorphism on peptide-laden HLA recognition. Mutational analysis revealed that KIR residues involved in water-mediated contacts with the HLA-presented peptide influence peptide binding specificity. In particular, residue 282 (glutamate) in the D2 domain underpins the lack of tolerance of negatively charged C-terminal peptide residues. Allotypic KIR3DL1 variants, defined by neighboring residue 283, displayed differential sensitivities to HLA-bound peptide, including the variable HLA-B*57:01–restricted HIV-1 Gag-derived epitope TW10. Residue 283, which has undergone positive selection during the evolution of human KIRs, also played a central role in Bw4 subtype recognition by KIR3DL1. Collectively, our findings uncover a common molecular regulator that controls HLA and peptide discrimination without participating directly in peptide-laden HLA interactions. Furthermore, they provide insight into the mechanics of interaction and generate simple, easily assessed criteria for the definition of KIR3DL1 functional groupings that will be relevant in many clinical applications, including bone marrow transplantation.

Genetic diversity of the KIR/HLA system and outcome of patients with metastatic colorectal cancer treated with chemotherapy

OBJECTIVE

To explore genes of the killer-cell immunoglobulin-like receptor (KIR) and of the HLA ligand and their relationship with the outcome of metastatic colorectal cancer (mCRC) patients treated with first-line 5-fluorouracil, leucovorin, and irinotecan (FOLFIRI).

METHODS

A total of 224 mCRC patients were screened for KIR/HLA typing. The determination of the KIR/HLA combinations was based upon the gene content and variants. Genetic associations with complete response (CR), time to progression (TTP) and overall survival (OS) were evaluated by calculating odds and hazard ratios. Multivariate modeling with prognostic covariates was also performed.

RESULTS

For CR, the presence of KIR2DL5A, 2DS5, 2DS1, 3DS1, and KIR3DS1/HLA-Bw4-I80 was associated with increased CR rates, with median ORs ranging from 2.1 to 4.3, while the absence of KIR2DS4 and 3DL1 was associated with increased CR rates (OR 3.1). After univariate analysis, patients that underwent resective surgery of tumor, absence of KIR2DS5, and presence of KIR3DL1/HLA-Bw4-I80 showed a significant better OS (HR 1.5 to 2.8). Multivariate analysis identified as parameters independently related to OS the type of treatment (surgery; HR 2.0) and KIR3DL1/HLA-Bw4-I80 genotype (HR for T-I80 2.7 and for no functional KIR/HLA interaction 1.8). For TTP, no association with KIR/HLA genes was observed.

CONCLUSION

This study, for the first time, evidences that the genotyping for KIR-HLA pairs are found predictive markers associated with complete response and improves overall survival prediction of FOLFIRI treatment response in metastatic colorectal cancer. These results suggest a role of the KIR/HLA system in patient outcome, and guide new research on the immunogenetics of mCRC through mechanistic studies and clinical validation.

The yin-yang of KIR3DL1/S1: molecular mechanisms and cellular function

Killer Immunoglobulin-like Receptors (KIR) are a family of receptors expressed on natural killer (NK) and T-cell subsets. KIR3DL1 is a highly polymorphic receptor that binds to groups of HLAA and HLA-B allotypes that express the Bw4 epitope. The variation in KIR3DL1 allotypes manifests at a number of levels. Most dramatically, a common allelic variant encodes an activating rather than an inhibitory receptor (KIR3DS1). In addition, sequence variants can affect both the frequency of expression within the NK cell population and the intensity of expression on a given cell. KIR3DL1 polymorphism also influences the interaction with HLA-Bw4 molecules, due to contacts with the HLA molecule itself and sensitivity to the presented peptide. A body of evidence from genetic association studies supports the biological significance not only of the interaction of KIR3DL1 with HLA-Bw4 but also the functional variation seen with different KIR3DL1 and HLA allotypes. In this review, we discuss our current understanding of KIR3DL1 function and our recent insights from the structure of the KIR3DL1 in complex with HLA. In addition, we will summarize our current understanding of KIR3DS1, including its ligand specificity and its role in immune responses.

KIR3DS1/L1 and HLA-Bw4-80I are associated with HIV disease progression among HIV typical progressors and long-term nonprogressors

Background

Natural killer (NK) cells have emerged as pivotal players in innate immunity, especially in the defense against viral infections and tumors. Killer immunoglobulin-like receptors (KIRs) – an important recognition receptor expressed on the surface of NK cells – regulate the inhibition and/or activation of NK cells after interacting with human leukocyte antigen (HLA) class I ligands. Various KIR genes might impact the prognosis of many different diseases. The implications of KIR-HLA interaction in HIV disease progression remains poorly understood.

Methods

Here, we studied KIR genotypes, mRNA levels, HLA genotypes, CD4⁺ T cell counts and viral loads in our cohort of Human Immunodeficiency Virus (HIV)-infected individuals, a group that includes HIV long-term nonprogressors (LTNPs) and typical progressors (TPs).

Results

We found that the frequency of KIR3DS1/L1 heterozygotes with HLA-Bw4-80I gene was much higher in LTNPs than in TPs (P = 0.001) and that the KIR3DL1 homozygotes without HLA-Bw4-80I gene had higher viral loads and lower CD4⁺ T cell counts (P = 0.014 and P = 0.021, respectively). Our study also confirmed that homozygosity for the HLA-Bw6 allele was associated with rapid disease progression. In addition to the aforementioned results on the DNA level, we observed that higher level expression of KIR3DS1 mRNA was in LTNP group, and that higher level expression of KIR3DL1 mRNA was in TP group.

Conclusions

Our data suggest that different KIR-HLA genotypes and different levels of transcripts associate with HIV disease progression.

Animal models for prenatal gene therapy: the nonhuman primate model

Intrauterine gene therapy (IUGT) potentially enables the treatment and possible cure of monogenic -diseases that cause severe fetal damage. The main benefits of this approach will be the ability to correct the disorder before the onset of irreversible pathology and inducing central immune tolerance to the vector and transgene if treatment is instituted in early gestation. Cure has been demonstrated in small animal models, but because of the significant differences in immune ontogeny and the much shorter gestation compared to humans, it is unlikely that questions of long-term efficacy and safety will be adequately addressed in rodents. The nonhuman primate (NHP) allows investigation of key issues, in particular, the different outcomes in early and late-gestation IUGT associated with different stages of immune maturity, longevity of transgene expression, and delayed-onset adverse events in treated offspring and mothers including insertional mutagenesis. Here, we describe a model based on the Macaca fascicularis using ultrasound and fetoscopic approaches to systemic vector delivery and the processes involved in vector administration and longitudinal analyses.

In vitro modulation of natural killer activity of human peripheral blood mononuclear cells against prostate tumor cell line

OBJECTIVE

Natural killer (NK) cells have long been known to be involved in the recognition and lysis of tumor cells but the mechanisms contributing to deficient NK activity in patients with cancer remains unclear. Manipulation of them is likely essential to the success of cancer immunotherapy protocols although optimal stimulation and maintenance of NK activity remains elusive. Here we studied the stimulatory effects of PHA and K562, on NK activity of human peripheral blood mononuclear cells (PBMCs).

MATERIALS AND METHODS

The NK activity of PBMCs against DU-145 was determined with 51Cr-release assay. The PBMCs were stimulated with PHA, either on one occasion or repetitively on three occasions (1-PHA-PBMC or 3-PHA-PBMC, respectively), and were incubated with irradiated K562 (iK562). The expression of CD56, NKG2D and MICA/B were detected on PBMCs and cell lines with flow cytometry.

RESULTS

PHA stimulation increased the proportion of CD56+ cells and upregulated NKG2D expression on 1-PHA-PBMC and 3-PHA-PBMC, but co-incubation with iK562 decreased NKG2D expression on 1-PHA-PBMC without change of NKG2D expression on the 3-PHA-PBMC. NK activity of 1-PHA-PBMC appeared to decrease with co-incubation with iK562 compared to a significant increase in activity of 3-PHA-PBMC. A similar increase in interferon-γ (IFN-γ) secretion from 3-PHA-PBMC was demonstrated compared to 1-PHA-PBMC.

DISCUSSION AND CONCLUSION

Our results demonstrated that varying the mitogen exposure to PBMCs affect the influence of iK562 on NK activity. This effect appeared to be unrelated to the subsequent expression of NKG2D or IFN-γ secretion. These results may be beneficial in the development of future cancer immunotherapy protocols.

Peptide antagonism as a mechanism for NK cell activation

Inhibition of natural killer (NK) cells is mediated by MHC class I receptors including the killer cell Ig-like receptor (KIR). We demonstrate that HLA-C binding peptides can function as altered peptide ligands for KIR and antagonize the inhibition mediated by KIR2DL2/KIR2DL3. Antagonistic peptides promote clustering of KIR at the interface of effector and target cells, but do not result in inhibition of NK cells. Our data show that, as for T cells, small changes in the peptide content of MHC class I can regulate NK cell activity.

Early immune response against retrovirally transduced herpes simplex virus thymidine kinase-expressing gene-modified T cells coinfused with a T cell-depleted marrow graft: an altered immune response?

Administration of herpes simplex thymidine kinase (HSV-tk)-expressing, gene-modified T cells (GMCs) with T cell-depleted bone marrow transplantation (TCD-BMT) can allow modulation of posttransplantation alloreactivity. Twelve patients received 2 x 10(5) to 2 x 10(6) CD3+ donor GMCs per kilogram with HLA-identical sibling TCD-BMT. Despite extensive T cell depletion of bone marrow, an intensive conditioning regimen, and immunosuppressive graft-versus-host disease (GvHD) prophylaxis, infusion at the time of TCD-BMT of this low number of GMCs sufficed to induce a rapid GMC-specific immune response, as detected by interferon- enzyme- linked immunospot assay in six of eight patients, preferentially targeting HSV-tk. Maximal responses were reached early (median time, 49 [35-68] days post-BMT), with a subsequent rapid and significant decrease in five of six evaluable patients. Immune responses were negatively correlated with the maximal circulating GMC counts. However, such immune response did not result in the elimination of circulating GMCs and was not associated with measurable ex vivo cytotoxic activity against GMCs. Furthermore, alloreactive GMCs still could induce GCV-sensitive GvHD in one patient despite an ongoing immune response. Overall, infusion of HSV-tk-expressing GMCs at the time of BMT results in an early immune response. Such immune response may be altered and may not prevent persistent GCV-sensitive alloreactivity.

Antiviral NK cell responses in HIV infection: I. NK cell receptor genes as determinants of HIV resistance and progression to AIDS

NK cells play an important role in controlling viral infections. They can kill virus-infected cells directly as well as indirectly via antibody-dependent, cell-mediated cytotoxicity. They need no prior sensitization and expansion for this killing. NK cells are also considered as important regulators of antiviral immune responses. They do so by secreting a multitude of soluble mediators and by directly interacting with other immune cells, e.g., dendritic cells. NK cells do not possess a single well-defined receptor to recognize antigens on target cells. Instead, they express an array of inhibitory and activating receptors and coreceptors, which bind to their cognate ligands expressed on the surface of target cells. These ligands include classical and nonclassical MHC class I antigens, MHC-like proteins, and a variety of other self- and virus-derived molecules. They may be expressed constitutively and/or de novo on the surface of virus-infected cells. NK cell receptors (NKRs) of the killer-cell Ig-like receptor (KIR) family, like their MHC class I ligands, are highly polymorphic. Several recent studies suggest that epistatic interactions between certain KIR and MHC class I genes may determine innate resistance of the host to viral infections, including HIV. In the first part of this review article, we provide an overview of the current state of knowledge of NK cell immunobiology and describe how NKR genes, alone and in combination with HLA genes, may determine genetic resistance/susceptibilty to HIV infection and the development of AIDS in humans.

Killer cell immunoglobulin-like receptors on NK cells: the how, where and why

Natural killer (NK) cells have killer cell immunoglobulin-like receptors (KIR) that recognize and interact with HLA class I antigen. The KIRs are a multigene family and its members are often highly polymorphic. Evidence is emerging from disease-association studies that KIR receptors can play beneficial roles in viral infections, such as HIV, HCV, but may also predispose to certain autoimmune diseases. Knowledge regarding expression and function of KIR on human NK cells is lagging behind the rapid expansion of sequencing and genetic data already generated. This review focuses on recent discoveries that have been made, which help bridge this gap. We now appreciate the importance of phenotypic diversity of KIR receptor expression in NK cells and are starting to unravel some of the mysteries surrounding control of their complex expression patterns. In particular, the role that HLA ligand contributes to KIR receptor expression will be discussed. It is also becoming increasingly clear that genetic factors, such as promoters and epi-genetic mechanisms such as methylation, are hugely important in controlling NK cell receptor expression and function. The relevance of phenotypic diversity of NK cell receptors will be discussed in light of these recent findings.

Functional polymorphism of the KIR3DL1/S1 receptor on human NK cells

NK cells express both inhibitory and activatory receptors that allow them to recognize target cells through HLA class I Ag expression. KIR3DL1 is a receptor that recognizes the HLA-Bw4 public epitope of HLA-B alleles. We demonstrate that polymorphism within the KIR3DL1 receptor has functional consequences in terms of NK cell recognition of target. Inhibitory alleles of KIR3DL1 differ in their ability to recognize HLA-Bw4 ligand, and a consistent hierarchy of ligand reactivity can be defined. KIR3DS1, which segregates as an allele of KIR3DL1, has a short cytoplasmic tail characteristic of activatory receptors. Because it is very similar to KIR3DL1 in the extracellular domains, it has been assumed that KIR3DS1 will recognize a HLA-Bw4 ligand. In this study, we demonstrate that KIR3DS1 is expressed as a protein at the cell surface of NK cells, where it is recognized by the Z27 Ab. Using this Ab, we found that KIR3DS1 is expressed on a higher percentage of NK cells in KIR3DS1 homozygous compared with heterozygous donors. In contrast to the inhibitory KIR3DL1 allotypes, KIR3DS1 did not recognize HLA-Bw4 on EBV-transformed cell lines.

Contribution of KIR3DL1/3DS1 to ankylosing spondylitis in human leukocyte antigen-B27 Caucasian populations

Killer cell immunoglobulin-like receptors (KIRs) and human leukocyte antigen (HLA) loci are both highly polymorphic, and some HLA class I molecules bind and trigger cell-surface receptors specified by KIR genes. We examined whether the combination of KIR3DS1/3DL1 genes in concert with HLA-B27 genotypes is associated with susceptibility to ankylosing spondylitis (AS). Two HLA-B27-positive Caucasian populations were selected, one from Spain (71 patients and 105 controls) and another from the Azores (Portugal) (55 patients and 75 controls). All were typed for HLA-B and KIR (3DS1 and 3DL1) genes. Our results show that in addition to B27, the allele 3DS1 is associated with AS compared with B27 controls (p < 0.0001 and p < 0.003 in the Spanish population and Azoreans, respectively). We also observed that the association of KIR3DS1 to AS was found in combination with HLA-B alleles carrying Bw4-I80 in trans position in the Spanish population (30.9% in AS versus 15.2% in B27 controls, p = 0.02, odds ratio (OR) = 2.49) and in Azoreans (27.2% in AS versus 8.7% in B27 controls, p = 0.01, OR = 4.4 in Azoreans). On the other hand, 3DL1 was decreased in patients compared with B27 controls (p < 0.0001 in the Spanish population and p < 0.003 in Azoreans). The presence of this allele in combination with Bw4-I80 had a protective effect against the development of AS in the Spanish population (19.7% in AS, 35.2% in B27 controls; p = 0.03, OR = 0.45). The presence of KIR3DS1 or KIR3DL1 in combination with HLA-B*27s/HLA-B Bw4-I80 genotypes may modulate the development of AS. The susceptibility to AS could be determined by the overall balance of activating and inhibitory composite KIR-HLA genotypes.

Putting the natural killer cell in its place

Natural killer (NK) cells were originally described as 'null' lymphocytes, but we have increasing evidence of their role in recognizing pathogen, and our knowledge of NK cell receptors continues to expand exponentially. Human NK cells have many receptors for human leucocyte antigen (HLA) class I. These killer immunoglobulin-like receptors (KIRs) and CD94/NKG2 receptors can signal in both positive and negative ways to regulate NK cell functions. The inhibitory receptors are the best characterized, but even in these cases much of their functional biology remains elusive. In this review, some recent advances in terms of the three-immunoglobulin (3Ig)-domain KIRs are discussed. Natural cytotoxicity receptors (NCRs) are among the activatory receptors found on NK cells. While pathogen ligands for these receptors have been described, endogenous ligands remain elusive. NCRs and NKG2D, a receptor for stress-induced antigens, appear to play complementary functional roles in terms of NK cell activation. More recently described on NK cells are the Toll-like receptors. In particular, these receptors of the innate immune system allow NK cells to directly sense pathogen, and their ligation on accessory cells indirectly activates NK cells through cytokine production. It is becoming clear that none of these receptor systems functions in isolation and that it is the sum of the signals (which will reflect the pathogenic situation), in addition to the cytokine milieu, that will direct NK cell activation. The resulting cytotoxicity, cytokine production and direct cell-cell regulatory interactions with other cells of the immune system, for example dendritic cells, ultimately determine the role of the NK cell in the context of an overall immune response.

The Decreased Susceptibility of Bcr/Abl Targets to NK Cell-Mediated Lysis in Response to Imatinib Mesylate Involves Modulation of NKG2D Ligands, GM1 Expression, and Synapse Formation

Chronic myeloid leukemia is a clonal multilineage myeloproliferative disease of stem cell origin characterized by the presence of the Bcr/Abl oncoprotein, a constitutively active tyrosine kinase. In previous studies, we have provided evidence that Bcr/Abl overexpression in leukemic cells increased their susceptibility to NK-mediated lysis by different mechanisms. In the present study, using UT-7/9 cells, a high level Bcr/Abl transfectant of UT-7 cells, we show that the treatment of Bcr/Abl target by imatinib mesylate (IM), a specific Abl tyrosine kinase inhibitor, hampers the formation of the NK/target immunological synapse. The main effect of IM involves an induction of surface GM1 ganglioside on Bcr/Abl transfectants that prevents the redistribution of MHC-related Ag molecules in lipid rafts upon interaction with NK cells. IM also affects cell surface glycosylation of targets, as assessed by binding of specific lectins resulting in the subsequent modulation of their binding to lectin type NK receptor, particularly NKG2D. In addition, we demonstrate that the tyrosine kinase activity repression results in a decrease of MHC-related Ags-A/B and UL-16-binding protein expression on Bcr/Abl transfectants UT-7/9. We show that NKG2D controls the NK-mediated lysis of UT-7/9 cells, and IM treatment inhibits this activating pathway. Taken together, our results show that the high expression of Bcr/Abl in leukemic cells controls the expression of NKG2D receptor ligands and membrane GM1 via a tyrosine kinase-dependent mechanism and that the modulation of these molecules by IM interferes with NK cell recognition and cytolysis of the transfectants.

Interaction between KIR3DL1 and HLA-B*57 supertype alleles influences the progression of HIV-1 infection in a Zambian population

KIR and HLA loci are both highly polymorphic, and some HLA class 1 products bind and trigger cell-surface receptors specified by KIR genes. We examined whether KIR genes act in concert with HLA-B locus to control HIV-1 infection in a sample of Zambian patients. DNA samples from 88 Zambian patients with HIV-1 were examined. Patients were classified as either slow progressors (SP; n = 54) or rapid progressors (RP; n = 34) to AIDS. All were typed for HLA-B and KIR genes. Our results reveal an association between B*57 supertype (B*57s, which includes B*57 and B*58 alleles) and delayed progression to AIDS (p = 0.0007 by pc = 0.015; OR = 5.25). We also observed an increase incidence of Bw4-I80 in patients with slow progression (p = 0.001 by pc = 0.003, OR = 5). This increase was found to be secondary to B*57s. The presence of both KIR3DL1 and B*57S has a significant effect on progression to AIDS (p = 0.0008; OR = 5.61). B*57s genotypes with another HLA-B allele different from those in the trans position, which also had a specificity different to Bw4-I80 (Bw4-T80 or Bw6), was also greater in the SP than in the RP group (p = 0.00003; OR = 10.11). The presence of the inhibitory allele KIR3DL1 in combination with the HLA-B*57s alleles that contain the Bw4-I80 epitope, has a highly protective effect against progression to AIDS in Zambian patients.

Induction of transgene-specific immunological tolerance in myeloablated nonhuman primates using lentivirally transduced CD34+ progenitor cells

Modeling human hematopoietic progenitor cell gene therapy in nonhuman primates allows long-term evaluation of safety, maintenance of gene expression, and potential immune response against transgene products. We transplanted autologous G-CSF/SCF-mobilized CD34+ cells transduced with lentiviral vectors expressing EGFP into myeloablated rhesus macaques. To date, more than 4 years posttransplantation, 0.5-8% EGFP expression is maintained in multiple cell lineages. The animals remain healthy with no evidence of hematopoietic abnormalities or malignancies. To assess immune functions, we actively immunized two of our transplanted animals with purified rEGFP proteins and CpG adjuvant and demonstrated stable levels of EGFP+ cell populations maintained for over 29 months despite four active immunizations. We did not detect a persistent anti-EGFP antibody response or anti-EGFP T cell response in these immunized animals. Immune response to an irrelevant antigen was normal. Taken together, our data provide formal support that transplantation of lentivirally transduced CD34+ progenitor cells in myeloablated rhesus macaques induces specific immunological tolerance toward a foreign transgene.

A point mutation in the first splice donor leads to reduced oncogenic properties of the adenovirus serotype 12 E1A gene

Cells transformed by proteins of early regions 1A (E1A) and 1B (E1B) of oncogenic adenovirus serotype 12 (Ad12) grow to tumours in syngeneic, immunocompetent rodents. To gain insight into the mechanisms of oncogenic transformation, we point mutated the first splice donor in the Ad12-E1A gene, leading to the loss of the Ad12-E1A(9.5S) and Ad12-E1A(11S/10S) proteins and to a conservative amino acid (aa) exchange at position aa 30 (valine vs. leucine) in the Ad12-E1A(13S) and Ad12-E1A(12S ) proteins. BMK cells transformed by mutant Ad12-E1A (Ad12-E1Am) plus Ad12-E1B via retrovirus-mediated gene transfer showed features comparable to wild-type Ad12-E1A (Ad12-E1Awt) plus Ad12-E1B-transformed cells: they formed foci in soft agar and produced tumours in immunodeficient nude mice, although after a prolonged latency period. These results suggest that Ad12-E1A(9.5S) and Ad12-E1A(11S/10S) are dispensable for cellular transformation. However, in contrast to Ad12-E1Awt cells, Ad12-E1Am cells failed to grow to tumours in syngeneic, immunocompetent rodents, with the exception of one cell line, which produced tumours in about 50% of the immunocompetent animals. Interestingly, the concentration of the putative tumour suppressor and co-activator p300 was elevated in cell lines expressing high levels of Ad12-E1A and Ad12-E1B due to an increased half-life. These results indicate that p300 is stabilized in Ad12-E1-transformed BMK cells, probably by a mechanism linked to high expression of Ad12-E1A/E1B.

Analysis of donor NK and T cells infused in patients undergoing MHC-matched allogeneic hematopoietic transplantation

We retrospectively analyzed the percentages and absolute numbers of T cells, natural killer (NK) cells and NK cell subsets in cryopreserved samples of either bone marrow or blood non-T cell-depleted allogeneic MHC-matched hematopoietic grafts. Using flow cytometry, we found higher numbers of NK cells in aphereses than in bone marrow collections. We further investigated the distribution of NK cell subsets, defined by the cell surface expression of MHC class I-specific receptors, in these allogeneic grafts. The distribution of NK cell subsets from the two different origins were similar, with the exception of the CD158a/h(+) NK cell subset, whose size appeared to be smaller in bone marrow. The search for relations between the numbers of infused cells and post-transplantation events demonstrated that increasing numbers of infused T cells but not NK cells are related with decreased overall survival. Our study highlights the toxicity of infused T cells but not NK cells in allogeneic MHC-matched hematopoietic grafts. These data pave the way for further trials to investigate the effect of NK cell infusion in MHC-matched allogeneic transplantation, and in particular whether ex vivo NK cell expansion and activation may enhance the anti-tumoral effect of the procedure and decrease its morbidity.

KIR: diverse, rapidly evolving receptors of innate and adaptive immunity

KIR genes have evolved in primates to generate a diverse family of receptors with unique structures that enable them to recognize MHC-class I molecules with locus and allele-specificity. Their combinatorial expression creates a repertoire of NK cells that surveys the expression of almost every MHC molecule independently, thus antagonizing the spread of pathogens and tumors that subvert innate and adaptive defense by selectively downregulating certain MHC class I molecules. The genes encoding KIR that recognize classical MHC molecules have diversified rapidly in human and primates; this contrasts with conservation of immunoglobulin- and lectin-like receptors for nonclassical MHC molecules. As a result of the variable KIR-gene content in the genome and the polymorphism of the HLA system, dissimilar numbers and qualities of KIR:HLA pairs function in different humans. This diversity likely contributes variability to the function of NK cells and T-lymphocytes by modulating innate and adaptive immune responses to specific challenges.

Induction of stable prenatal tolerance to beta-galactosidase by in utero gene transfer into preimmune sheep fetuses

The successful transduction of hematopoietic stem cells and long-term (28 months) transgene expression within the hematopoietic system following the direct injection of high-titer retroviral vectors into preimmune fetal sheep was previously demonstrated. The present studies extended these analyses for 40 months postinjection and evaluated whether the longevity of transgene expression in this model system was the result of induction of prenatal tolerance to the transgene product. The intraperitoneal injection of retroviral vectors into preimmune sheep fetuses transduces thymic epithelial cells thought to present antigen and thus define self during immune system development. To directly demonstrate induction of tolerance, postnatal sheep were boosted with purified beta-galactosidase and showed that the peripheral blood lymphocytes from in utero-transduced sheep exhibited significantly lower stimulation indices to transduced autologous cells than did control animals and that the in utero-transduced sheep had a reduced ability to mount an antibody response to the vector-encoded beta-galactosidase protein compared with control sheep. Collectively, our results provide evidence that the direct injection of retroviral vectors into preimmune sheep fetuses induces cellular and humoral tolerance to the vector/transgene products and provide an explanation for the duration and stability of transgene expression seen in this model. These results also suggest that even relatively low levels of gene transfer in utero may render the recipient tolerant to the exogenous gene and thus potentially permit the successful postnatal treatment of the recipient. (Blood. 2001;97:3417-3423)

Control of HIV-1 viremia and protection from AIDS are associated with HLA-Bw4 homozygosity

Certain HLA-B antigens have been associated with lack of progression to AIDS. HLA-B alleles can be divided into two mutually exclusive groups based on the expression of the molecular epitopes HLA-Bw4 and HLA-Bw6. Notably, in addition to its role in presenting viral peptides for immune recognition, the HLA-Bw4, but not HLA-Bw6, motif functions as a ligand for a natural killer cell inhibitory receptor (KIR). Here, we show that profound suppression of HIV-1 viremia is significantly associated with homozygosity for HLA-B alleles that share the HLA-Bw4 epitope. Furthermore, homozygosity for HLA-Bw4 alleles was also significantly associated with the ability to remain AIDS free and to maintain a normal CD4 T cell count in a second cohort of HIV-1-infected individuals with well defined dates of seroconversion. This association was independent of the presence of a mutation in CC chemokine receptor 5 (CCR5) associated with resistance to HIV-1 infection, and it was independent of the presence of HLA alleles that could potentially confound the results. We conclude that homozygosity for HLA-Bw4-bearing B alleles is associated with a significant advantage and that the HLA-Bw4 motif is important in AIDS pathogenesis.

A self-immunomodulating myoblast cell line for erythropoietin delivery

The transplantation of genetically engineered cells faces limitations associated with host immunity. Allogeneic cells are typically rejected in response to inherent histo-incompatibility. Even autologous cells can induce an immune response toward antigenic molecules expressed following transfer of foreign genes. The goal of the present study was to investigate the ability of immunomodulating molecules co-expressed with biotherapeutic factors to overcome these limitations both in syngeneic and allogeneic cell transplantation. The C(2)C(12) mouse myoblast cell line was engineered to express CTLA4Ig, a soluble factor blocking T cell costimulation, in conjunction with erythropoietin (Epo), a reporter biotherapeutic protein. In syngeneic C3H mice, myoblasts expressing only mouse Epo were mostly rejected within 2 weeks, as indicated by the transient increase in host hematocrit. In allogeneic recipients, the same cells induced only a 1-week increase in the hematocrit reflecting an acute rejection process. CTLA4Ig expression significantly extended the survival of mouse Epo-secreting myoblasts in approximately half of syngeneic hosts, whereas it led only to a 1-week improvement effect in allogeneic recipients. When combined with a transient anti-CD154 treatment, CTLA4Ig expression prevented Epo-secreting C(2)C(12)myoblasts from being rejected in allogeneic DBA/2J recipients for at least 1 month. In contrast, the same anti-CD154 treatment alone induced only a 1 week improvement. These results demonstrate that CTLA4Ig co-expression associated with a transient anti-CD154 treatment can prolong the delivery of recombinant proteins via transfer of ex vivo modified cells in allogeneic recipients.

Combination gene therapy: synergistic inhibition of human immunodeficiency virus Tat and Rev functions by a single RNA molecule

Current drug combinations can achieve long-term suppression of HIV replication in infected individuals. Unfortunately, complicated dosing schedules and high toxicity make long-term compliance with drug regimens difficult for most patients. Gene therapy may provide a permanent solution for HIV disease by generating cells genetically resistant to virus replication. As with the highly active antiretroviral therapies, genetic drugs must have strong antiviral potency and the ability to prevent the emergence of escape mutants. We have constructed antiviral genes containing unique combinations of Tat- and Rev-binding decoys. The new antiviral molecules are chimeric TAR-RRE RNAs that are expressed only in HIV infected cells in a Tat-regulated manner. One RNA molecule competes for both Tat and Rev binding, and thus blocks the activation and the expression of all viral genes. The two functional Tat- and Rev-binding domains exhibit the highest synergy at the lowest concentration. Conservative quantitative estimates of this synergistic effect were I = 0.24 at 50% inhibition, in terms of the Berenbaum "interaction index," indicating that the combined construct was approximately fourfold more potent than would be predicted on the basis of additive effects. The possibility of HIV escape from this inhibition is unlikely, because it requires simultaneous mutation of TAR and RRE in a manner in which both Tat and Rev preserve their respective functions. TAR-RRE combination decoys represent the first example of mathematically proven synergistic antiviral activity between two domains of the same molecule.