TNF-α levels in respiratory samples are associated with SARS-CoV-2 infection.

ABSTRACT Purpose Increased serum levels of IL-6 and TNF-α have been proposed as biomarkers for COVID-19 progression. However, the role and the implication of these cytokines in SARS-CoV-2 infection remain controversial. The aim of this study was to measure levels of IL-6 and TNF-α in swab samples from individuals with symptoms compatible with COVID-19 and analyze their association with SARS-CoV-2 presence. Methods SARS-CoV-2 detection was performed using the CDC (USA) real-time RT-PCR primers, probes and protocols. Cytokine concentrations were measured using commercial reagents based on enzyme linked immunosorbent assay (ELISA). Results TNF-α median levels were greater in COVID19 (+) symptomatic group (5.88 (1.36 - 172.1) pg/ml) compared to COVID19 (−) symptomatic individuals (2.87 (1.45 – 69.9) pg/ml) (p=0.0003). No significant differences were shown in IL-6 median values between COVID-19 (+) and (−) symptomatic patients (5.40 (1.7 - 467) pg/ml and 6.07 (1.57 – 466.6) pg/ml respectively). In addition, increased TNF-α levels (greater than 10 pg/ml), but not IL-6, were associated with SARS-CoV-2 presence (OR= 5.7; p=0.006; 95% CI= 1,551 to 19,11). Conclusions IL-6 concentration showed high levels in swabs from some symptomatic patients, suggesting the presence of immune response at viral entry site. However, IL-6 levels were independent from SARS-CoV-2 presence and viral load, individual’s age and gender. On the contrary, TNF-α evaluation confirmed the presence of inflammatory response but mostly related to COVID-19. More studies are required in order to characterize the cytokine profile expressed at the site of infection of SARS-CoV-2 and its implications in disease outcomes.