Financial difficulities

The purpose of the study is to determine vitamin D (VD) levels and upper respiratory tract infections (URTI) morbidity among elite athletes engaged in water sports in Uzbekistan. Serum levels of 25(OH) VD and TNF-α, IFN-γ, IL-4 and IL-6 will be detected by ELISA technique among elite athletes and control population in spring and autumn.

Study center The prospective diagnostic study will be conducted on the basis of Uzbek State University of Physical Education and Sport and Research Institute of Epidemiology, Microbiology and Infectious Diseases, Tashkent, Uzbekistan during the period from January 2017 till January 2019.

Both informed and written consents will be obtained from the athletes and healthy individuals.

Study participants Aproximately 40 elite athletes engaged in water sport and 60 healthy individuals will be included to the study.

All the participants will be residents of Uzbekistan.

Serological tests Five milliliters of peripheral venous blood will be taken (after 8-12 hours of fasting) from each participant and will be collected into Human Tube Serum Gel - C/A for ELISA. All blood samples will be collected in August and January.

Serum levels of 25(OH) VD and TNF-α, IFN-γ, IL-4 and IL-6 will be detected by ELISA technique.

Enzyme immunoassay for the quantitative measurement of total 25-OH-Vitamin D (Vitamin D2 and D3) in human serum.

Solid phase enzyme-linked immunosorbent assay (ELISA) based on the competition principle. An unknown amount of antigen present in the sample and a fixed amount of enzyme labelled antigen compete for the binding sites of the antibodies coated onto the wells. After incubation the wells are washed to stop the competition reaction. After the substrate reaction the intensity of the developed colour is inversely proportional to the amount of the antigen in the sample. Results of samples can be determined directly using the standard curve.

A sandwich enzyme immunoassay for in vitro quantitative measurement of TNFa The microplate provided in this kit has been pre-coated with an antibody specific to TNFa. Standards or samples are then added to the appropriate microplate wells with a biotin-conjugated antibody specific to TNFa. Next, Avidin conjugated to Horseradish Peroxidase (HRP) is added to each microplate well and incubated. After TMB substrate solution is added, only those wells that contain TNFa, biotin-conjugated antibody and enzyme-conjugated Avidin will exhibit a change in color. The enzyme-substrate reaction is terminated by the addition of sulphuric acid solution and the color change is measured spectrophotometrically at a wavelength of 450nm ± 10nm. The concentration of TNFa in the samples is then determined by comparing the O.D. of the samples to the standard curve.

IFN-γ, IL-4 and IL-6 will be detected and measured by the same enzyme immunoassay method presented above.

Data analysis will be performed with the program Origin 6.1 (OriginLab, Northampton, MA).

Inclusion Criteria:

• Healthy individuals
• Swimmers to distance
• Synchronized swimmers

Exclusion Criteria:

• chronic infectious and noninfectious diseases
• acute infectious and noninfectious diseases
• history of using VD supplements within six months or drugs usage within three months.

Healthy individuals Swimmers to distance Synchronized swimmers