Exercise has been shown to influence the immune system and, for example, improve anti-viral immune response. However, knowledge of how exercise impacts the immune system is still lacking. Therefore, the goal of this clinical study is to perform a comprehensive multi-parameter analysis of immunological parameters in healthy participants before and after one bout of high-intensity aerobic exercise. The primary endpoint of this study is to determine the exercise-induced changes of anti-viral T cell immunity in peripheral blood against common and recurrent viruses.

Up to 70 healthy participants in the age between 18 and 75 will be recruited. The first visit will be for prescreening the health status, answering questionnaires and providing a capillary blood sample for HLA screening. HLA-A2 positive participants will continue on the trial with a VO2 max test for Visit 2 and the supervised aerobic medium- to high-intensity (90% VO2 max) exercise session for Visit 3. Peripheral blood samples will be taken pre-exercise, within 2 minutes post-exercise and 60 minutes post-exercise.

These findings may pave the way to define serum markers or cellular immunological traits that provide new insight into how exercise promotes powerful and sustained cellular immune responses.

Numerous physiological parameters are influenced by exercise, including marked changes on numerous markers of the immune system. It has been shown that exercise lowers systemic low-grade inflammation, and there are indications that exercise improves the ability to combat infections and vaccination-induced immune responses.

Exercise has been repeatedly shown to mobilize immune cells into peripheral blood - most pronouncedly prototype killer cells of both the innate and adaptive immune system namely Natural Killer (NK) and T cells. Both cell types are critical in immune responses against viral infections and are also key effector cells in anti-cancer immune responses. Even more so, previously activated NK and T cells are selectively mobilized, potentially providing the background for exercise-mediated stronger anti-viral immunity.

In this study, the blood samples will be used to study global viral T cell reactivity against chronic [Cytomegalovirus (CMV) and Ebstein-Barr virus (EBV)] and recurrent [Influenza (flu) and SARS-CoV-2] viruses and detect their exact frequencies in peripheral blood. Since the technique is optimized for HLA*A2:01 positive individuals, this study will include a prescreening to match this tissue type. Adding more complexity to the acquired data, further analyses include but are not limited to phenotyping by CyTOF and flow cytometry as well as Luminex immune assays.

The current study will provide important insight into how the immune system is influenced by acute medium-to high-intensity exercise. These findings may have important implications for vaccine development, prevention in frail and at-risk populations, cancer prevention and cancer therapy.

Inclusion Criteria:

• Have the ability to speak and read English and/or Danish.
• Agree to avoid alcohol, nonprescription drugs, and strenuous exercise for 24 hours prior VO2 max test and exercise intervention.
• Signed informed consent.

Exclusion Criteria:

• Autoimmune disease requiring active treatment.
• A condition requiring systemic treatment with either corticosteroids (> 10 mg daily prednisone equivalents) or other immunosuppressive medications. Inhaled or topical steroids and adrenal replacement doses ≤ 10 mg daily prednisone equivalents are permitted
• Use of medication known to affect the immune system (regular use of ibuprofen/aspirin or beta-blockers).
• Any systemic infections with fever within the last 4 weeks before the exercise intervention.
• Use of any illegal drugs (e.g., cocaine, amphetamine).
• Conditions with high risk for complications during exercise: Unstable medical disease, condition, or history of serious or concurrent illness; any medical condition that might be aggravated by exercise training or that cannot be controlled, including, but not restricted to congestive heart failure (NYHA class III-IV), unstable angina pectoris, implantable cardioverter defibrillator (ICD), or myocardial infarction within 6 months.