High frequencies of polyfunctional CD8+ NK cells in chronic HIV-1 infection are associated with slower disease progression.

UNLABELLED: Natural killer (NK) cells are effector and regulatory innate immune cells and play a critical role in the first line of defense against various viral infections. Although previous reports have indicated the vital contributions of NK cells to HIV-1 immune control, nongenetic NK cell parameters directly associated with slower disease progression have not been defined yet. In a longitudinal, retrospective study of 117 untreated HIV-infected subjects, we show that higher frequencies as well as the absolute numbers of CD8(+) CD3(-) lymphocytes are linked to delayed HIV-1 disease progression. We show that the majority of these cells are well-described blood NK cells. In a subsequent cross-sectional study, we demonstrate a significant loss of CD8(+) NK cells in untreated HIV-infected individuals, which correlated with HIV loads and inversely correlated with CD4(+) T cell counts. CD8(+) NK cells had modestly higher frequencies of CD57-expressing cells than CD8(-) cells, but CD8(+) and CD8(-) NK cells showed no differences in the expression of a number of activating and inhibiting NK cell receptors. However, CD8(+) NK cells exhibited a more functional profile, as detected by cytokine production and degranulation. IMPORTANCE: We demonstrate that the frequency of highly functional CD8(+) NK cells is inversely associated with HIV-related disease markers and linked with delayed disease progression. These results thus indicate that CD8(+) NK cells represent a novel NK cell-derived, innate immune correlate with an improved clinical outcome in HIV infection.

Loss of CCR7 expression on CD56(bright) NK cells is associated with a CD56(dim)CD16⁺ NK cell-like phenotype and correlates with HIV viral load.

NK cells are pivotal sentinels of the innate immune system and distinct subpopulations in peripheral blood have been described. A number of studies addressed HIV-induced alterations of NK cell phenotype and functionality mainly focusing on CD56(dim)CD16⁺ and CD56⁻CD16⁺ NK cells. However, the impact of HIV-infection on CD56(bright) NK cells is less well understood. Here we report a rise of CD56(bright) NK cells in HIV-infected individuals, which lack CCR7-expression and strongly correlate with HIV viral load. CCR7⁻CD56(bright) NK cells were characterized by increased cytolytic potential, higher activation states and a more differentiated phenotype. These cells thus acquired a number of features of CD56(dim)CD16⁺ NK cells. Furthermore, CD56(bright) NK cells from HIV patients exhibited higher degranulation levels compared to uninfected individuals. Thus, chronic HIV-infection is associated with a phenotypic and functional shift of CD56(bright) NK cells, which provides a novel aspect of HIV-associated pathogenesis within the NK cell compartment.

Phenotypically and functionally distinct subsets contribute to the expansion of CD56-/CD16+ natural killer cells in HIV infection.

OBJECTIVE: Chronic HIV infection has been associated with activation and increased turnover of natural killer (NK) cells as well as with disturbed homeostasis of the NK cell compartment, including loss of CD56(+) NK cells and accumulation of dysfunctional CD56(-)/CD16(+) NK cells. We performed a comprehensive phenotypical and functional characterization of this population. DESIGN: A cross-sectional study was performed to analyze CD56(-)/CD16(+) NK cells from 34 untreated HIV-infected and 15 seronegative individuals. METHODS: NK cells were analyzed by flow cytometry. Degranulation was assessed by measuring their expression of CD107a after stimulation with K562 cells, interleukin-12 and interleukin-15. RESULTS: CD56(-)/CD16(+) NK cells are heterogeneous and composed of two populations, namely CD122(-)/CCR7(+) cells and CD122(-)/CCR7(+) cells. We show that expanded CD122(+) but not CCR7(+) cells in HIV-seropositive individuals are characterized by expression of senescence marker CD57 similarly to CD56(dim)/CD16(+) NK cells along with expression of KIRs, CD8, perforin and granzyme B. Despite expression of perforin and granzyme B, CD57 expressing cells exhibited less numbers of degranulating cells as measured by CD107a, indicating their functional impairment. However, there was no correlation between expansion of total CD56(-)/CD16(+) NK cells or the distinct subpopulations and viral load or CD4 cell count. CONCLUSION: These data indicate that expansion of CD56(-)/CD16(+) cells in HIV infection is driven by a distinct subset within this population with high expression of terminal differentiation marker with a phenotype resembling CD56(-)/CD16(+) NK cells.

HIV infection is associated with a preferential decline in less-differentiated CD56dim CD16+ NK cells.

HIV-1 infection is characterized by loss of CD56(dim) CD16(+) NK cells and increased terminal differentiation on various lymphocyte subsets. We identified a decrease of CD57(-) and CD57(dim) cells but not of CD57(bright) cells on CD56(dim) CD16(+) NK cells in chronic HIV infection. Increasing CD57 expression was strongly associated with increasing frequencies of killer immunoglobulin-like receptors (KIRs) and granzyme B-expressing cells but decreasing percentages of cells expressing CD27(+), HLA-DR(+), Ki-67(+), and CD107a. Our data indicate that HIV leads to a decline of less-differentiated cells and suggest that CD57 is a useful marker for terminal differentiation on NK cells.

CD26 expression determines lung metastasis in mutant F344 rats: involvement of NK cell function and soluble CD26.

The association between CD26 expression, tumor cell adhesion, metastasis, and natural killer (NK) cell function was investigated in a CD26 mutant Fischer 344 (F344/DuCrj) substrain from Japanese breeders (F344JAP) in comparison with wild-type F344 substrains from US (F344/Crl) and Hannover (HAN; F344/Ztm) breeders. F344JAP rats lack the dipeptidyl peptidase IV activity of CD26 and show a reduced cell surface expression of the mutated CD26 glycoprotein. In vivo adhesion of vital dye-labeled MADB106 tumor cells, tumor colonization, CD26 enzymatic activity, and CD26 immunoreactivity in lungs and soluble CD26-like protein expression in serum were markedly reduced in F344JAP rats. These findings demonstrate that CD26 protein expression exerts a key role in lung metastasis. In addition, NK cell cytotoxicity against MADB106 cells was diminished in the mutant F344 substrain, suggesting that CD26 enzymatic activity sustains NK cytotoxicity. Interestingly, tumor cells lacked CD26 immunoreactivity in vitro, but displayed CD26 immunoreactivity in situ after in vivo inoculation as well as after incubation with rat serum, indicating that soluble CD26-like protein assembles in tumor cells during in vivo passage, which may interact with the process of tumor adhesion and metastasis. Overall, these findings indicate that altered expression and function of a single enzyme-the CD26 protein--can drastically change the outcome of metastatic disease.

Modulation of Ly49 D expression after allogeneic bone marrow transplantation and functional consequences.

Ly49 antigens, interacting with MHC class I molecules, enable NK cells to distinguish "self" from "non-self". Here, we investigated the activating receptor Ly49 D after allogeneic bone marrow transplantation (BMT). After transplantation of B6 bone marrow (BM) into BALB/c recipients we observed a significant reduction of Ly49 D+ NK cells and a decreased density of expression. We found a nonstochastic distribution of Ly49 D with Ly49 G2. In contrast to reduced coexpression with Ly49 A, a constant rate of Ly49 G2 on Ly49 D+ NK cells was observed in allogeneic chimeras. Cytotoxicity was reduced during the first two months after BMT After this time allogeneic chimeras showed tolerance against host-specific targets. We conclude that NK cells are able to shape their Lys49 repertoire fitting to a new environment after allogeneic BMT. This alteration seems to depend on the presence of new corresponding MHC class I molecules resulting in downregulation of respective receptors on donor cells. Analysing coexpression of Ly49 D and Ly49 G2, we found a relationship between these two receptors, showing a distinct effect after allogeneic BMT. Functional data indicate that a time of reduced NK cell cytotoxicity after BMT is followed by in vitro tolerance of allogeneic chimeras.

Kinetics of the early recruitment of leukocyte subsets at the sites of tumor cells in the lungs: natural killer (NK) cells rapidly attract monocytes but not lymphocytes in the surveillance of micrometastasis.

Early host defense mechanisms play a critical role for the outcome of metastatic disease but most of the initial steps of such responses against tumor cells are still unknown. Here, the specificity and kinetics of leukocyte subsets in response to intravenous inoculation of vital dye labeled Fischer 344 rat syngeneic MADB106 tumor cells were monitored in lungs in situ by immunohistochemistry and image analysis over a time-period of 6 hr. In comparison with sham injections, tumor cell inoculation induces a dynamic sequence of rapidly increasing granulocyte (+40% at 5 min), NK and T cell (+60% at 15 min) as well as monocyte (+100% at 30 min) numbers in lung tissue. Already within the first minutes frequent colocalizations of granulocytes and NK cells with tumor targets were found in situ. Within the first hour NK cells selectively kill tumor targets, because depletion of NK cells in vivo drastically increases both the number of MADB106 cells retained in lungs and the emerging numbers of lung tumor colonies. In addition, the tumor-cell-induced increase of monocytes strictly depends on the presence of NK cells because NK-depletion completely abrogates the time specific response of monocytes. Under NK depleted conditions the tumor-induced recruitment of CD4(+) T cells is more pronounced suggesting a compensatory mechanism. In contrast, B cell numbers progressively decrease within hours after cell inoculation. These findings demonstrate that NK and T cells mediate the initial steps in the surveillance of lung metastasis. NK cells rapidly kill tumor cells and subsequently recruit monocytes in vivo.