Latent Virus Infection (PCS3, Subsample)

Latent herpesvirus infection and reactivation was assessed by measuring antibody to cytomegalovirus (CMV) in plasma.  CMV serostatus identifies those who previously have been infected with the virus, whereas CMV antibody titers provide an approximation of virus reactivation.  Because reactivation and replication of latent viruses is prevented by activities of the cellular immune system, circulating levels of CMV antibody titers might be used as an indirect measure of cellular immunity.  CMV antibody data are available for 140 participants.

Sample Collection and Preparation

CMV antibodies were assayed using stored sera that had been collected to measure pre-exposure specific antibody titers to the challenge virus (RV39).  Blood samples were collected by standard venipuncture into serum separator tubes on Quarantine Day 0, prior to the challenge procedure.  Samples were then placed in a VWR Clinical 100 centrifuge (VWR International, LLC) and spun for 10 minutes at 3500 rpm.  Following centrifugation, serum was removed by sterile pipette, placed into labeled 2-ml microcentrifuge tubes, and then stored at -70°C until shipped on dry ice to the University of Birmingham School of Sport and Exercise Sciences (Birmingham, United Kingdom) for CMV antibody assay.

Assay Procedures

Plasma from baseline blood samples was assayed for immunoglogulin G (IgG) antibodies to CMV using a commercially available enzyme-linked immunosorbent assay (ELISA) (Biocheck, Inc., CA, USA) according to manufacturer instructions.  Assay results were used to derive a CMV index, which provides a relative measure of CMV antibody levels that is proportional to but not a direct measure of CMV titers.  Index values of 0.90 and lower indicate negative CMV serostatus; values of 1.00 or greater indicate seropositivity for the virus; values ranging from 0.91 to 0.99 are considered to be equivocal.

Reference

Turner, J. E., Aldred, S., Witard, O. C., Drayson, M. T., Moss, P. M., & Bosch, J. A. (2010). Latent cytomegalovirus infection amplifies CD8 T-lymphocyte mobilisation and egress in response to exercise.  Brain, Behavior, and Immunity, 24, 1362-1370.