Background The relationship of host immune response and viral replication with health outcomes in patients with COVID-19 remains to be defined. We aimed to characterize the medium and long-term clinical, virological, and serological outcomes after hospitalization for COVID-19, and to identify predictors of long-COVID. Methods Prospective, longitudinal study conducted in COVID-19 patients confirmed by RT-PCR. Serial blood and nasopharyngeal samples (NPS) were obtained for measuring SARS-CoV-2 RNA and S-IgG/N-IgG antibodies during hospital stay, and at 1, 2, and 6 months post-discharge. Genome sequencing was performed where appropriate. Patients filled out a COVID-19 symptom questionnaire (CSQ) at 2-month and 6-month visits, and those with highest scores were characterized. Results Of 146 patients (60% male, median age 64 years) followed-up, 20.6% required hospital readmission and 5.5% died. At 2 months and 6 months, 9.6% and 7.8% patients, respectively, reported moderate/severe persistent symptoms. SARS-CoV-2 RT-PCR was positive in NPS in 11.8% (median Ct = 38) and 3% (median Ct = 36) patients at 2 months and 6 months, respectively, but no reinfections were demonstrated. Antibody titers gradually waned, with seroreversion occurring at 6 months in 27 (27.6%) patients for N-IgG and in 6 (6%) for S-IgG. Adjusted 2-month predictors of the highest CSQ scores (OR [95%CI]) were lower peak S-IgG (0.80 [0.66-0.94]) and higher WHO severity score (2.57 [1.20-5.86]); 6-month predictors were lower peak S-IgG (0.89 [0.79-0.99]) and female sex (2.41 [1.20-4.82]); no association was found with prolonged viral RNA shedding. Conclusions Long-COVID is associated with weak anti-SARS-CoV-2 antibody response, severity of illness, and female gender. Late clinical events and persistent symptoms in the medium and long term occur in a significant proportion of patients hospitalized for COVID-19.

Background The virological and immunological effects of the immunomodulatory drugs used for COVID-19 remain unknown. We evaluated the impact of interleukin (IL)-6 blockade with tocilizumab on SARS-CoV-2 viral kinetics and the antibody response in patients with COVID-19. Methods Prospective cohort study in patients admitted with COVID-19. Serial nasopharyngeal and plasma samples were measured for SARS-CoV-2 RNA and S-IgG/N-IgG titers, respectively. Findings 138 patients with confirmed infection were included; 76 (55%) underwent IL-6 blockade. Median initial SOFA ( p = 0•016) and SARS-CoV-2 viral load ( p <0•001, Mann-Whitney-Wilcoxon test) were significantly higher among anti-IL-6 users. Patients under IL-6 blockade showed delayed viral clearance in the Kaplan-Meier curves (HR 0•35 [95%CI] [0•15–0•81], log-rank p = 0•014), but an adjusted propensity score matching model did not demonstrate a significant relationship of IL-6 blockade with viral clearance (HR 1•63 [0•35–7•7]). Cox regression showed an inverse association between SARS-CoV-2 RNA clearance and the initial viral load (HR 0•35 [0•11–0•89]). Patients under the IL-6 blocker showed shorter median time to seropositivity, higher peak antibody titers, and higher cumulative proportion of seropositivity in the Kaplan Meier curves (HR 3•1 [1•9–5] for S-IgG; and HR 3•0 [1•9–4•9] for N-IgG; log-rank p <0•001 for both). However, no significant differences between groups were found in either S-IgG (HR 1•56 [0•41–6•0]) nor N-IgG (HR 0•96 [0•26–3•5]) responses in an adjusted propensity score analysis. Interpretation Our results suggest that in patients infected with SARS-CoV-2, IL-6 blockade does not impair the viral specific antibody responses. Although a delayed viral clearance was observed, it was driven by a higher initial viral load. The study supports the safety of this therapy in patients with COVID-19. Funding Instituto de salud Carlos III (Spain).

Objectives The interdependencies of viral replication and the host immune response in patients with COVID-19 remain to be defined. We investigated the viral determinants of antibody response, the predictors of non-seroconversion, and the role of antibodies on viral dynamics. Methods Prospective study in patients hospitalized with microbiologically confirmed COVID-19 by real-time polymerase-chain-reaction (RT-PCR). Serial nasopharyngeal and oropharyngeal swabs and plasma samples were obtained for measuring SARS-CoV-2 RNA and antibodies (total and S-IgG/N-IgG), respectively. Results Of 132 patients included, 99 (75%) showed positive antibody titers after a median (Q1-Q3) of 11 (8-14) days. Median (Q1-Q3) follow-up was 74.5 (63.0-87.0) days. In adjusted linear regression model, time to seropositivity was inversely associated with peak log SARS-CoV-2 viral load (p=0.009) and positively with time to viral clearance (p=0.004). Adjusted predictors of S-IgG levels were time to viral clearance (p&lt;0.001), bilateral lung infiltrates on admission (p=0.011), and the time-dependent SARS-CoV-2 RNA (p&lt;0.001) and SARS-CoV-2 RNA area under the curve (p=0.001). Thirty-three (25%) patients showed undetectable antibody titers. Patients who did not seroconvert had higher cycle threshold values of RT-PCR (38.0 vs 28.0; p&lt;0.001), shorter time to viral clearance (3.0 vs 41.0; p&lt;0.001) and were more likely to have SARS-CoV-2 only detected on fecal samples (p&lt;0.001). Non-seroconvertors had also lower levels of blood inflammatory biomarkers on admission and lower disease severity. Conclusions Viral replication determines the magnitude of antibody response to SARS-CoV-2 that, in turn, contributes to viral clearance. COVID-19 patients who do not seroconvert exhibit a differential virological and clinical profile.

Excessive interleukin-6 signaling is a key factor contributing to the cytokine release syndrome implicated in clinical manifestations of COVID-19. Preliminary results suggest that tocilizumab, a humanized monoclonal anti-interleukin-6 receptor antibody, may be beneficial in severely ill patients, but no data are available on earlier stages of disease. An anticipated blockade of interleukin-6 might hypothetically prevent the catastrophic consequences of the overt cytokine storm. We evaluated early-given tocilizumab in patients hospitalized with COVID-19, and identified outcome predictors. Consecutive patients with initial Sequential-Organ-Failure-Assessment (SOFA) score < 3 fulfilling pre-defined criteria were treated with tocilizumab. Serial plasma biomarkers and nasopharyngeal swabs were collected. Of 193 patients admitted with COVID-19, 64 met the inclusion criteria. After tocilizumab, 49 (76.6%) had an early favorable response. Adjusted predictors of response were gender, SOFA score, neutrophil/lymphocyte ratio, Charlson comorbidity index and systolic blood pressure. At week-4, 56.1% of responders and 30% of non-responders had cleared the SARS-CoV-2 from nasopharynx. Temporal profiles of interleukin-6, C-reactive protein, neutrophil/lymphocyte ratio, NT-ProBNP, D-dimer, and cardiac-troponin-I differed according to tocilizumab response and discriminated final in-hospital outcome. No deaths or disease recurrences were observed. Preemptive therapy with tocilizumab was safe and associated with favorable outcomes in most patients. Biological and clinical markers predicted outcomes.

Objectives Durability of the humoral immune response to SARS-CoV-2 has yet to be defined. We longitudinally evaluated during a 12-month period the antibody responses to SARS-CoV-2, and analysed predictors of antibody titres decline and seroreversion. Methods Prospective study conducted in a cohort of patients hospitalized for microbiologically-confirmed COVID-19. Blood and nasopharyngeal samples were sequentially obtained during hospital stay and at 1, 2, 6 and 12 months after patients’ discharge for measuring anti-spike (S) and anti-nucleocapsid (N) IgG antibody levels and SARS-CoV-2 RNA, respectively. Results 80 non-vaccinated patients were analysed. At month 12 after discharge, 73 (91.2%) patients exhibited detectable S-IgG and 35 (43.8%) N-IgG antibody titres. A gradual wane was observed in S-IgG and N-IgG antibody titres. Linear regression showed that S-IgG decline was positively associated with peak antibody titres (coefficient [95% CI] 0.059 [0.05–0.067], p < 0.001), inversely with WHO severity score (coefficient [95% CI] −0.042 [-0.079/-0.004], p = 0.033), and there was a trivial positive association with age (coefficient [95% CI] 0.002 [0–0.005], p = 0.10); N-IgG decline was positively associated with peak antibody titres (coefficient [95% CI] 0.091 [0.078–0.105], p < 0.001). Logistic regression showed that seroreversion for S-IgG was inversely associated with peak S-IgG (OR 0.19; 95% CI, 0.04-0.45; p = 0.004); seroreversion for N-IgG was inversely associated with peak N-IgG (OR 0.71; 95% 0.53–0.90; p = 0.009) and positively with cycle threshold of RT-PCR (OR 1.14; 95% CI, 1.00–1.33; p = 0.062). Conclusion Anti-spike IgG antibodies remain detectable one year after hospitalization for COVID-19. Higher peak antibody titres and disease severity were associated with increased durability of detectable antibodies.