Introducción: Es fundamental evaluar los niveles de protección inmune en infectados o tras la vacunación frente a SARS-CoV-2. La medición de la respuesta inmune celular T puede complementar la determinación de anticuerpos. Nuestro objetivo fue evaluar la viabilidad de un ensayo comercial validado de respuesta celular T. Métodos: Se incluyeron veinte trabajadores sanitarios (TS). Medimos anticuerpos contra proteínas N y S de SARS-CoV-2 en paralelo con un ensayo de liberación de interferón-gamma (IFNγ) en sangre completa (IGRA) para péptidos de la proteína S. IFNγ se determinó mediante dos métodos de detección: CLIA y ELISA. Resultados: IGRA detectó respuesta celular T en TS tanto infectados como vacunados. La correlación de los dos métodos de detección de IFNγ fue muy alta (R>0,8) y la sensibilidad y la especificidad variaron entre 100 y 86% y 100-73% respectivamente. Hubo una concordancia muy alta entre los niveles de anticuerpos específicos y el ensayo IGRA aunque la correlación cuantitativa fue relativamente baja. En el pequeño grupo de infectados, una dosis de vacuna fue suficiente para alcanzar la meseta de respuesta inmune. IGRA fue claramente positivo en un profesional vacunado inmunosuprimido que presentaba anticuerpos contra la proteína S negativos. Conclusiones: IGRA frente a péptidos de la proteína-S es susceptible de automatización y constituye una herramienta prometedora para medir la respuesta inmune celular frente a SARS-CoV-2; es aplicable a un gran número de muestras y puede servir para valorar la protección, particularmente en los grupos vulnerables en riesgo de volver a exponerse a la infección, como los TS.

Background: Clinical trials on the different vaccines to SARS-CoV-2 have demonstrated protection efficacy, but it is urgent to assess the levels of protection generated with real-world data, especially in individuals professionally exposed. Measuring T-cell responses may complement antibody tests currently in use as correlates of protection but there are not validated T-cell responses applicable to large number of samples. Objective: To assess the feasibility of using T-cell responses to SARS-CoV-2 S peptides by commercially available whole blood interferon-gamma release assays (IGRA) as a correlate of protection. Patients: Twenty health care workers before and after vaccination. Methods: Antibody test to SARS-CoV-2 N and S proteins in parallel with one IGRA assay and two detection techniques than can be automated. Results: IGRA test detected T-cell responses in naturally exposed and vaccinated HCW already after first vaccination dose. the correlation by the two detection methods, CLIA and ELISA, very high (R>0.9) and sensitivity and specificity ranged between 100 and 86% and 100-73% respectively. Even though there was a very high concordance between antibody and the IGRA assay in the ability to detect immune response to SARS-CoV-2 there was a relatively low quantitative correlation. In the small group primed by natural infection, one vaccine dose was sufficient to reach immune response plateau. IGRA was positive in one Ig (S) antibody negative vaccinated immunosuppressed HCW illustrating another advantage of the IGRA test. Conclusion: Whole blood IGRA tests amenable to automation, as the one here reported, constitute a promising additional tool for measuring the state of the immune response to SARS-CoV-2; they are applicable to large number of samples and may become valuable correlates of protection to COVID-19, particularly for vulnerable groups at risk of being re-exposed to infection, as are health care workers.

Background SARS-CoV-2 infection portends a broad range of outcomes, from a majority of asymptomatic cases to a lethal disease. Robust correlates of severe COVID-19 include old age, male sex, poverty, and co-morbidities such as obesity, diabetes, and cardiovascular disease. A precise knowledge of the molecular and biological mechanisms that may explain the association of severe disease with male sex is still lacking. Here, we analyzed the relationship of serum testosterone levels and the immune cell skewing with disease severity in male COVID-19 patients. Methods Biochemical and hematological parameters of admission samples in 497 hospitalized male and female COVID-19 patients, analyzed for associations with outcome and sex. Longitudinal (in-hospital course) analyses of a subcohort of 114 male patients were analyzed for associations with outcome. Longitudinal analyses of immune populations by flow cytometry in 24 male patients were studied for associations with outcome. Results We have found quantitative differences in biochemical predictors of disease outcome in male vs. female patients. Longitudinal analyses in a subcohort of male COVID-19 patients identified serum testosterone trajectories as the strongest predictor of survival (AUC of ROC = 92.8%, p < 0.0001) in these patients among all biochemical parameters studied, including single-point admission serum testosterone values. In lethal cases, longitudinal determinations of serum luteinizing hormone (LH) and androstenedione levels did not follow physiological feedback patterns. Failure to reinstate physiological testosterone levels was associated with evidence of impaired T helper differentiation and augmented circulating classical monocytes. Conclusions Recovery or failure to reinstate testosterone levels is strongly associated with survival or death, respectively, from COVID-19 in male patients. Our data suggest an early inhibition of the central LH-androgen biosynthesis axis in a majority of patients, followed by full recovery in survivors or a peripheral failure in lethal cases. These observations are suggestive of a significant role of testosterone status in the immune responses to COVID-19 and warrant future experimental explorations of mechanistic relationships between testosterone status and SARS-CoV-2 infection outcomes, with potential prophylactic or therapeutic implications.