The impact of cytomegalovirus on naive lymphocytes in a novel non-human primate model.

Abstract Immunosenescence causes changes in the immune system, such as losses of naïve T-cells, which can lead to immune impairment in the elderly. Cytomegalovirus (CMV) is a common chronic herpesvirus that has been implicated in immunosenescence, although its direct effects have remained unclear. Therefore, we wanted to test the impact of CMV on immunosenescence in a recently validated baboon model. To assess the effects of CMV on the immune system over time, we determined lymphocyte populations and CMV load in age-matched baboon groups representing variable CMV exposure and shedding pressures: specific pathogen free (SPF; CMV−); small-group conventionally housed (SMConv; CMV+); and large-group conventionally housed (LGConv; CMV+) baboons (7animals/group). All baboon groups showed a decrease in naïve cells over time (P≤0.5). However at Year 1, between-group comparisons revealed 50% fewer CD8+ naïve cells in LGConv animals compared to SPF and SMConv. In Year 2, the number of naïve cells in SMConv was intermediate to that of SPF and LGConv; and by Year 3, CD8+ naïve cells were decreased in both Conv groups compared to SPF (P≤0.5). Preliminary results also revealed that a greater proportion of LGConv baboons shed CMV compared to SMConv. These data indicate that all baboons, independent of pathogen status and environmental conditions, show signs of immunosenescence at this age (9.6–11.6 years); however, LGConv baboons appear to be aging more quickly. Ongoing work includes the addition of more animals, further characterization of viral shedding and load, and infection of SPF baboons with CMV to help verify these differences. Results of this project will lead to a better understanding of the role of CMV in immunosenescence.