C.M.T. T cell response intensities. Conclusions These data suggest that rapid virus clearance mediated by SARS-CoV-2-specific T cells prevents severe symptoms of COVID-19. Keywords: SARS-CoV-2, T cells, antibody, immune response, symptoms Introduction SARS-CoV-2 induces highly variable clinical manifestations of COVID-19, ranging from asymptomatic infections or mild disease characteristics to severe and even life-threatening courses LG-100064 of disease (Garca,?2020). Infected individuals present with a variety of different disease symptoms, comprising fever, fatigue, loss of smell and taste, cough, headache, and/or dyspnea (Li?et?al., 2020). On the basis of the manifestations of these symptoms, patients are categorized into different disease severity groups (Son?et?al., 2021) with most patients experiencing mild symptoms that do not require medical intervention or hospitalization (Nakamichi?et?al., 2021). After relief of symptoms, patients are considered to be protected from reinfection for several months, mediated by the immunological memory of the humoral and cellular immune system (Tan?et?al., 2020). The humoral immune response (ie, SARS-CoV-2-specific antibodies) detected in convalescent individuals has led to the approval of immune therapeutics like the REGN-COV2 antibody cocktail (Weinreich?et?al., 2021) and prophylactic vaccines, which aim to induce a protective immune response (Polack?et?al., 2020). Although most infected individuals remain asymptomatic or show mild symptoms and mount a potent immune response, others suffer LG-100064 from a severe course of disease with a dysregulated immune reaction (Kowalik?et?al., Rabbit Polyclonal to EPHA7 (phospho-Tyr791) 2020; Kr?mer?et?al., 2021; Qin?et?al., 2020). A plethora of data are available regarding the characteristics of humoral and cellular immune responses in SARS-CoV-2-infected individuals (Altmann?and Boyton,?2020; Bilich?et?al., 2021a; Bilich?et?al., 2021b; Brunk?et?al., 2021; Jarjour?et?al., 2021; Kared?et?al., 2021; Karlsson?et?al., 2020; Nelde?et?al., 2021; Sekine?et?al., 2020; Woldemeskel?et?al., 2020; Woodruff?et?al., 2020). Although antibody titers have been reported to be increased in patients with more severe COVID-19 (Woodruff?et?al., 2020), so far, little is known about the correlation of T cell responses with clinical symptoms. T cells are not only central for immune modulation and for guiding B cells to produce antibodies, but they also play an important role in virus clearance by direct killing LG-100064 of SARS-CoV-2-infected cells (Grifoni?et?al., 2020; Kared?et?al., 2021). Here, we studied the COVID-19 course of 193 individuals during asymptomatic to moderate SARS-CoV-2 infection and their association with SARS-CoV-2-specific antibody and T cell responses up to 59 days after acute infection. The documented differences in symptom severity and immune response provide insights into the role of T LG-100064 cell immunity against SARS-CoV-2 for the occurrence and severity of clinical symptoms. Methods Convalescents and blood samples Blood and serum samples as well as questionnaire-based assessment of donor characteristics and disease symptoms from convalescent volunteers after asymptomatic to moderate symptomatic SARS-CoV-2 infection (n?=?193) were collected at the University Hospital Tbingen from April to July 2020. Informed consent was obtained in accordance with the Declaration of Helsinki protocol. The study was approved by and performed according to the guidelines of the local ethics committees (179/2020/BO2). SARS-CoV-2 infection was confirmed by polymerase chain reaction (PCR) test after nasopharyngeal swab. Donor recruitment was performed by online and paper-based advertising (homepage, flyer). Sample collection in terms of peripheral blood mononuclear cells (PBMCs) and serum was performed approximately 3C8 weeks after the end of symptoms and/or negative virus smear. Symptom categories were determined by subjective disease symptoms (no, mild, LG-100064 moderate, and severe; reported by questionnaire) of individual donors. Detailed donor characteristics and distribution of symptom severity are provided in Tables?1 and ?and22 . Table 1 Donor characteristics of COVID-19 convalescent donors. test or.