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Abstract

The monocyte subsets classical (CD14++CD16-) intermediate (CD14++CD16+), and pro-inflammatory (CD14+CD16++) have both overlapping and independent roles in inflammation and immune regulation. Aging is associated with increased chronic low-grade inflammation, which may be influenced by both exercise and latent cytomegalovirus (CMV) infection. The PURPOSE of this study was to determine if serum CMV status affects monocyte mobilization in response to acute cardiorespiratory (CRE) versus resistance exercise (RE) in older adults. We hypothesized that CMV seropositive participants would have greater mobilization of CD16+ (inflammatory and intermediate) monocyte subsets after each exercise. METHODS Twenty-four healthy older adults (56–75 years) from a variety of fitness backgrounds completed this randomized complete crossover study. Participants were healthy and did not report symptoms of active infection. On two separate visits, participants performed a single ~30-minute bout of CRE (70% heart rate reserve) or RE (70% 1-repetition maximum). Blood was collected pre-exercise (PRE), immediately post-exercise (POST), and 1-hour post-exercise (RECOV). Monocyte subsets were identified using flow cytometry based on CD14 and CD16 cell-surface expression. CMV serostatus was determined via a commercial ELISA kit. Data are presented as mean ± SE. RESULTS CMV serostatus did not significantly affect subset monocyte counts at rest or immediately post-exercise for either exercise mode. However, at RECOV, CMV+ individuals had higher intermediate monocyte counts compared to CMV- (CMV-: -12.9 ± 4.68 cells/µL vs. CMV+: -0.86 ± 1.95 cells/µL, p=0.0312). A similar pattern was observed for intermediate monocyte percentages (CMV-: -5.70 ± 2.17% vs. CMV+: -0.26 ± 0.72%, p = 0.0341). Following resistance exercise (RE), CMV+ individuals had higher absolute intermediate monocyte counts at RECOV compared to CMV- (CMV-: 13.9 ± 2.82 cells/µL vs. CMV+: 27.7 ± 6.34 cells/µL, p = 0.0396). No differences were observed for classical or pro-inflammatory monocytes at any timepoint. In CONCLUSION, CMV seropositivity did not influence monocyte mobilization immediately post-exercise, but CMV+ individuals exhibited sustained elevations of intermediate monocytes at 1-hour recovery following both CRE and RE. CMV serostatus and exercise mode should be considered when interpreting exercise immunology research.

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