Comparison of Cytokines Levels Among Covid-19 Patients Living at Sea Level and High Altitude

Abstract

Purpose: The inflammatory response in COVID-19 among people living at different altitudes has not been studied. Given that chronic hypoxia promotes cytokines production in the absence of disease, the inflammatory response against SARS-CoV-2 may also be different in these populations. The aim of this study was to compare pro-inflammatory cytokine levels among healthy and COVID-19 patients living at different altitudes above sea level. Methods & Materials: A descriptive cross-sectional study was performed in two Peruvian cities at different altitudes for comparison: Lima (sea level) and Huaraz (3052 meters above sea level). Patients with COVID-19 diagnosis confirmed by reverse-transcriptase polymerase chain reaction (RT-PCR) were compared to healthy subjects, according to their residing location. Five important proinflammatory cytokines were measured including: IL-6, IL-2, IL-10, IFN-γ and TNF-α using ELISA-based assays. Cytokines levels were calculated and their mean, maximum and minimum levels were reported according to each study group. The difference between means was compared using the ANOVA and post-hoc Turkey Test, a signifiant value of p<0.05 was considered significant. Results: A total of 35 COVID-19 patients and 10 healthy subjects were recruited from each study site. The mean levels of IL-6 (p<0.03) and TNF-α (p<0.01) were significantly different among the study groups. In the case of IL-6, patients from Lima had a mean level of 16.2 pg/ml (healthy) and 48.3 pg/ml (COVID-19), meanwhile, patients from Huaraz had levels of 67.3 pg/ml (healthy) and 97.9 pg/ml (COVID-19). Regarding TNF-α, patients from Lima had a mean level of 25.9 pg/ml (healthy) and 61.6 pg/ml (COVID-19), meanwhile, patients from Huaraz had levels of 89.0 pg/ml (healthy) and 120.6 pg/ml (COVID-19). The levels of IL-2, IL-10 and IFN-γ were not significantly different in the study groups. Conclusion: Patients with COVID-19 residing in high-altitude tend to have higher levels of inflammatory cytokines, particularly IL-6 and TNF-α. Altogether, this findings demonstrates the need to perform more studies in populations residing at high altitude, given that inflammatory response may be significantly different in these populations.