Influence of CMV/EBV serostatus on respiratory infection incidence during 4 months of winter training in a student cohort of endurance athletes

Abstract

The purpose of this study was to examine the influence of previous infection with cytomegalovirus (CMV) or Epstein Barr virus (EBV) on the incidence, severity and duration of upper respiratory tract illness (URTI) episodes in endurance athletes during a 4-month winter training period. Blood samples were obtained from 236 healthy subjects (186 males, 70 females) who were engaged in regular sports training (predominantly endurance-based activities such as running, cycling, swimming, triathlon, team games and racquet sports) at the start of the study period for CMV and EBV serostatus analysis. Their baseline characteristics were (mean ± SD) age: 21 ± 2 years, body mass: 73.5 ± 11.2 kg, height: 176.5 ± 9.3 cm, body mass index 23.6 ± 2.2 kg/m 2 . Weekly training and daily illness logs were kept. Self-reported weekly training duration averaged 9.6 ± 5.2 h/week and 4.0 ± 1.6% of the cohort experienced a URTI episode each week. Twenty-five percent of the subject cohort were CMV positive with a similar proportion in males (24%) and females (26%) whereas 84% of the subject cohort were EBV positive with a similar proportion in males (84%) and females (83%). In addition, 21% of the subject cohort were both CMV and EBV positive (CMV+EBV+) whereas 13% of the subject cohort had no prior CMV or EBV infection (CMV-EBV-). With regard to CMV/EBV serostatus, the results indicated that there was no difference in the proportion of subjects who presented with symptoms of infection between CMV/EBV positive and negative groups. Athletes with previous CMV infection had fewer URTI symptom days during the study period than those with no previous infection [mean and interquartile range (IQR), positives 2 (0-7) days, negatives 4 (1-9) days, P = 0.033] and EBV serostatus had no influence on URTI episode incidence, severity or duration. Moreover, we found that athletes with prior infection of both CMV and EBV had fewer URTI episodes and symptom days than athletes who were seronegative for both CMV and EBV [mean (IQR), URTI episodes: positives 0 (0-1), negatives 1 (0-2), P = 0.04; symptom days: positives 2 (0-7), negatives 8 (2-12), P = 0.01]. The reasons for this are still unclear but could be related to the previously reported elevated T cytotoxic cell response to exercise in individuals with positive CMV serostatus. Previous coinfection with CMV and EBV might promote protective immune surveillance to lower the risk of URTI.

The Effect of Fish Oil, Vitamin D and Protein on URTI Incidence in Young Active People

“…There is currently very little information on the effects of EPA, DHA, protein or vitamin D on sIgA levels and as the current study did not find any changes in URTI incidence, duration or severity perhaps the lack of change in sIgA is not surprising. It has previously been shown that sIgA secretion rate does decrease from "optimal" to "inadequate" vitamin D status [15], although to our knowledge there have been no previous supplementation studies. With regard protein supplementation one study has demonstrated that glutamine supplementation is unable to attenuate the acute exercise induced decrease in sIgA levels [18].…”

“…For example, Vitamin D has been demonstrated to promote antibacterial responses in monocytes/macrophages, altering T helper cell function and viral inactivation [24]. Consequently, the potential role of vitamin D in URTI incidence has been proposed due to the immune role of vitamin D. On this basis He and colleagues [15] investigated the incidence of URTI compared to plasma vitamin D levels. This study demonstrated that participants who were deficient in vitamin D (<30nmol/L 25(O)HD) had an increased number of symptom days and symptom severity score, with no significant effect on URTI incidence or duration.…”

Immunological aspects of sport nutrition

“…Unlike the other vitamins that are obtained through the diet, vitamin D is unique since it is mostly produced via endogenous synthesis from a cholesterol precursor (7-dehydrocholesteol) in the skin following sunlight (ultraviolet B radiation) exposure with usually less than 20% of the body's needs coming from the diet. Although controversy exists over what represents optimal vitamin D status, there is accumulating evidence to suggest that many athletes are vitamin D deficient 15,16 , especially in the winter months, largely as a consequence of inadequate sun exposure, combined with poor dietary practices. The health and performance consequences of such deficiencies are still somewhat unclear in athletic populations but some studies have reported impaired muscle function, reduced regenerative capacity and increased bone fracture risk 15 , together with impaired immune function and increased respiratory infection risk 16 with low Vitamin D status in athletes.…”

“…Although controversy exists over what represents optimal vitamin D status, there is accumulating evidence to suggest that many athletes are vitamin D deficient 15,16 , especially in the winter months, largely as a consequence of inadequate sun exposure, combined with poor dietary practices. The health and performance consequences of such deficiencies are still somewhat unclear in athletic populations but some studies have reported impaired muscle function, reduced regenerative capacity and increased bone fracture risk 15 , together with impaired immune function and increased respiratory infection risk 16 with low Vitamin D status in athletes. Vitamin D is important in inducing production of antimicrobial proteins, upregulating genes for junction proteins in epithelial cells, enhancing NK cell cytolytic activity, increasing the generation of reactive oxygen species and the expression of inducible nitric oxide synthase in phagocytic cells as well as augmenting interleukin-1 secretion and upregulating the expression of CD14, the lipopolysaccharide receptor.…”

“…Vitamin D is important in inducing production of antimicrobial proteins, upregulating genes for junction proteins in epithelial cells, enhancing NK cell cytolytic activity, increasing the generation of reactive oxygen species and the expression of inducible nitric oxide synthase in phagocytic cells as well as augmenting interleukin-1 secretion and upregulating the expression of CD14, the lipopolysaccharide receptor. Low vitamin D status in athletes low vitamin D status is associated with low saliva IgA secretion, low pro-inflammatory cytokine production by antigen-stimulated blood mononuclear cells and increased respiratory infection risk with longer lasting illness symptoms 16 . Oral vitamin D3 supplements of around 4 000 IU per day can elevate vitamin D status from deficient levels to adequate or high levels within a matter of weeks and can significantly elevate saliva IgA and defensin secretion rates in athletes 31 .…”