T-cell redeployment and intracellular cytokine expression following exercise: effects of exercise intensity and cytomegalovirus infection

The magnitude of lymphocytosis following exercise is directly related to exercise intensity. Infection with cytomegalovirus (CMV) also augments lymphocytosis after exercise. It is not known if the enhanced T-cell response to exercise due to CMV depends on exercise intensity. Furthermore, exercise-induced changes in T-cell expression of type I and type II cytokines are thought to be intensity dependent, but direct comparisons are lacking. The aim of this experiment was to determine if CMV affects the exercise-induced redistribution of T-cell subsets at varying intensities, and determine the effect of exercise intensity on CD8⁺ T-cell cytokine expression. Seventeen cyclists (nine CMV seropositive; CMV+) completed three 30 min cycling trials at -5, +5, and +15% of blood lactate threshold (LT). T-cell subsets in blood and intracellular expression of type I (IL-2, interferon(IFN)-γ) and type II (IL-4, IL-10) cytokines by CD8⁺ T cells pre, post, and 1-h post-exercise were assessed by flow cytometry. Independently of CMV, T-cell subset redistribution was greater after +15%LT compared to -5%LT (P < 0.05). Independently of intensity, CMV- mobilized more low- (CD27⁺ CD28⁺) and medium- (CD27⁺ CD28^-) differentiated T cells than CMV+, whereas CMV+ mobilized more high (CD27^- CD28^-) differentiated T cells. The numbers of IL-2+, IFN-γ+, IL-4+, and IL-10+ CD8⁺ T cells increased after exercise above LT Only type I cytokine expression was influenced by exercise intensity (P < 0.05). In conclusion, T-cell redeployment by exercise is directly related to exercise intensity, as are changes in the number of CD8⁺ T-cells expressing type I cytokines. Although CMV+ mobilized more high-differentiated T cells than CMV-, this occurred at all intensities. Therefore, the augmenting effect of CMV on T-cell mobilization is independent of exercise intensity.

Latent cytomegalovirus infection enhances anti-tumour cytotoxicity through accumulation of NKG2C+ NK cells in healthy humans

Cytomegalovirus (CMV) infection markedly expands NKG2C+/NKG2A- NK cells, which are potent killers of infected cells expressing human leucocyte antigen (HLA)-E. As HLA-E is also over-expressed in several haematological malignancies and CMV has been linked to a reduced risk of leukaemic relapse, we determined the impact of latent CMV infection on NK cell cytotoxicity against four tumour target cell lines with varying levels of HLA-E expression. NK cell cytotoxicity against K562 (leukaemia origin) and U266 (multiple myeloma origin) target cells was strikingly greater in healthy CMV-seropositive donors than seronegative donors and was associated strongly with target cell HLA-E and NK cell NKG2C expression. NK cell cytotoxicity against HLA-E transfected lymphoma target cells (221.AEH) was ∼threefold higher with CMV, while NK cell cytotoxicity against non-transfected 721.221 cells was identical between the CMV groups. NK cell degranulation (CD107a(+) ) and interferon (IFN)-γ production to 221.AEH cells was localized almost exclusively to the NKG2C subset, and antibody blocking of NKG2C completely eliminated the effect of CMV on NK cell cytotoxicity against 221.AEH cells. Moreover, 221.AEH feeder cells and interleukin (IL)-15 were found to expand NKG2C(+) /NKG2A(-) NK cells preferentially from CMV-seronegative donors and increase NK cell cytotoxicity against HLA-E(+) tumour cell lines. We conclude that latent CMV infection enhances NK cell cytotoxicity through accumulation of NKG2C(+) NK cells, which may be beneficial in preventing the initiation and progression of haematological malignancies characterized by high HLA-E expression.

Acute exercise preferentially redeploys NK-cells with a highly-differentiated phenotype and augments cytotoxicity against lymphoma and multiple myeloma target cells. Part II: impact of latent cytomegalovirus infection and catecholamine sensitivity

We showed previously that acute exercise is associated with a preferential redeployment of highly-differentiated NK-cells and increased cytotoxicity against HLA-expressing tumor cell lines during exercise recovery. In this part II study, we retrospectively analyzed these findings in the context of latent cytomegalovirus (CMV) infection and performed additional experiments to explore potential mechanisms underpinning the marked reduction in NK-cell redeployment with exercise in CMV-seropositive individuals. We show here that latent CMV infection impairs NK-cell mobilization with exercise, only when the intensity of the exercise bout exceeds the individual blood lactate threshold (BLT). This impaired mobilization is associated with increased proportions of poorly exercise-responsive NK-cell subsets (NKG2C+/KIR-, NKG2C+/NKG2A-, and NKG2C+/CD57+) and decreased NK-cell β(2)-adrenergic receptor (AR) expression in those with CMV. As a result, NK-cell production of cyclic AMP (cAMP) in response to in vitro isoproterenol (synthetic β-agonist) stimulation was drastically lower in those with CMV (6.0 vs. 20.3pmol/mL, p<0.001) and correlated highly with the proportion of NKG2C+/CD57+ NK-cells (R(2)=0.97). Moreover, NK-cell cytotoxic activity (NKCA) against the K562 (36.6% vs. 22.7%, p<0.05), U266 (23.6% vs. 15.9%, p<0.05), and 221.AEH (41.3% vs. 13.3%, p<0.001) cell lines was increased at baseline in those infected with CMV; however, latent CMV infection abated the post-exercise increase in NKCA as a result of decreased NK-cell mobilization. Additionally, NKCA per cell against the U266 (0.24 vs. 0.12, p<0.01), RPMI-8226 (0.17 vs. 0.11, p<0.05), and 221.AEH (0.18 vs. 0.11, p<0.05) cell lines was increased 1h post-exercise (relative to baseline) in CMV-seronegative subjects, but not in those infected with CMV. Collectively, these data indicate that latent CMV infection may compromise NK-cell mediated immunosurveillance after acute exercise due to an increased proportion of "CMV-specific" NK-cell subsets with impaired β-adrenergic receptor signaling pathways.

Acute exercise preferentially redeploys NK-cells with a highly-differentiated phenotype and augments cytotoxicity against lymphoma and multiple myeloma target cells

NK-cells undergo a "licensing" process as they develop into fully-functional cells capable of efficiently killing targets. NK-cell differentiation is accompanied by an increased surface expression of inhibitory killer immunoglobulin-like receptor (KIR) molecules, which is positively associated with cytotoxicity against the HLA-deficient K562 cell line. NK-cells are rapidly redeployed between the blood and tissues in response to acute exercise, but it is not known if exercise evokes a preferential trafficking of differentiated NK-cells or impacts NK-cell cytotoxic activity (NKCA) against HLA-expressing target cells. Sixteen healthy cyclists performed three 30-min bouts of cycling exercise at -5%, +5%, and +15% of lactate threshold. Blood samples obtained before, immediately after, and 1h after exercise were used to enumerate NK-cells and their subsets, and determine NKCA and degranulating subsets (CD107+) against cell lines of multiple myeloma (U266 and RPMI-8226), lymphoma (721.221 and 221 AEH), and leukemia (K562) origin by 4 and 10-color flow cytometry, respectively. Exercise evoked a stepwise redeployment of NK-cell subsets in accordance with differentiation status [highly-differentiated (KIR+/NKG2A-) >medium-differentiated (KIR+/NKG2A+)>low-differentiated (KIR-/NKG2A+)] that was consistent across all exercise intensities. NKCA per cell increased ∼1.6-fold against U266 and 221 AEH targets 1h post-exercise and was associated with a decreased proportion of NK-cells expressing the inhibitory receptor CD158b and increased proportion of NK-cells expressing the activating receptor NKG2C, respectively. We conclude that exercise evokes a preferential redeployment of NK-cell subsets with a high differentiation phenotype and augments cytotoxicity against HLA-expressing target cells. Exercise may serve as a simple strategy to enrich the blood compartment of highly cytotoxic NK-cell subsets that can be harvested for clinical use.