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Updated: Jul 23, 2026

An In vitro Model to Study Immune Responses of Human Peripheral Blood Mononuclear Cells to Human Respiratory Syncytial Virus Infection
Published on: December 10, 2013
Protein S declines during winter respiratory infections
N K Kaba1, C W Francis, W J Hall
1University of Rochester School of Medicine & Dentistry, Rochester, New York 14642, USA.
Winter respiratory infections and seasonal changes significantly alter blood clotting factors, increasing thrombotic risk in older adults. This study highlights changes in total and free protein S levels, contributing to vascular disease concerns.
Area of Science:
- Hematology and Immunology
- Gerontology
- Epidemiology
Background:
- Increased cardiovascular and cerebrovascular events in older adults during winter are linked to prothrombotic changes.
- Seasonal effects and acute respiratory infections may influence these prothrombotic changes.
Purpose of the Study:
- To investigate the impact of acute winter respiratory infections on hemostatic and inflammatory markers.
- To compare these changes in younger and older adults against non-infected controls.
Main Methods:
- Prospective cohort study involving younger and older adults.
- Measurement of complement 4b-binding protein (C4-BP), functional protein S, total protein S, free protein S, and interleukin-6 (IL-6).
- Comparison of infected individuals with matched, non-infected controls, analyzing seasonal and infection-related effects.
Main Results:
- Combined analysis showed a significant increase in total protein S (83% to 98%) and a decrease in free protein S (100% to 70%) during winter infections.
- Seasonal changes significantly affected total protein S (+15%) and free protein S (-27%), independent of infection.
- Infection was significantly associated with a decrease in functional protein S (-17%) after adjusting for seasonal effects.
Conclusions:
- Seasonal and infection-related alterations in hemostatic parameters, particularly increased fibrinogen and decreased free protein S, may elevate thrombotic risk.
- These hemostatic changes could contribute to the excess vascular disease morbidity and mortality observed in older populations during winter.
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