HealthDay News — Individuals with shortened telomeres had an increased risk of contracting colds after laboratory exposure to a rhinovirus, researchers found.
For each standard deviation below the average telomere length in a group of healthy adults, the risk for becoming infected after snorting a standardized dose of rhinovirus 39 was increased by 22% to 38% (P≤0.02), Sheldon Cohen, PhD, from Carnegie Mellon University in Pittsburgh, and colleagues reported in the Journal of the American Medical Association.
The association between telomere length was not as strong for developing clinical illness, the researchers noted, and was only significant for one out of four cell types analyzed. “Because these data are preliminary, their clinical implications are unknown,” they wrote.
Cohen and colleagues examined the correlation between shorter telomeres in leukocytes and resistance to upper respiratory infection and clinical illness in a cohort of 152 healthy 18- to 55-year-old Pittsburgh residents. They measured telomere length on four types of immune cells — peripheral blood mononuclear cells, CD4-positive cells, CD8 cells positive for CD28, and CD8 cells negative for CD28.
Participants were then quarantined for 24 hours, given nasal drops containing 100 tissue culture infectious doses of rhinovirus 39, and monitored for five days. The primary endpoint of infection was defined as isolation of rhinovirus 39 strain in post-exposure nasal lavage samples, or as a four-fold or greater rise in antibody titers specific for the rhinovirus strain measured 28 days after exposure.
The rate overall of infection was 69% and the rate of clinical illness was 22%, the researchers found. Shorter telomeres increased the odds of infection, independent of prechallenge virus-specific antibody, demographics, contraceptive use, season or BMI.
For clinical illness, each standard deviation decrease in telomere length was associated with a significant increase in risk only for measurements on CD8/CD28-negative cells (RR=1.57; 95% CI: 1.01-2.35). For the other three cell types, relative risks ranged from 1.11 to 1.29, but did not approach statistical significance.
Similar associations were noted when the researchers analyzed the relationship between telomere length and risk for infection by tertiles.
For all cell types, 80% of individuals with telomere lengths in the shortest tertile developed infection vs. 60% of individuals with telomere lengths in the longest tertile. But the association was only significant in terms of clinical illness for telomere lengths in CD8/CD28-negative cells — about 25% of those in the shortest tertile developed colds vs. about 13% in the longest tertile.
Because CD28 is known to mediate upregulation of the telomerase enzyme, the researchers hypothesized that loss of CD28 may contribute to more rapid cellular aging, which in turn could be expected to “impair the host’s ability to fight infection.”