Persistence of IgG COVID-19 antibodies: A longitudinal analysis.

Background and aim: The kinetics of antibody production in response to coronavirus disease 2019 (COVID-19) infection is not well-defined yet. This study aimed to evaluate the antibody responses to SARS-CoV-2 and its dynamics during 9-months in a cohort of patients infected during the first phase of the pandemic. As a secondary aim, it was intended to evaluate the factors associated with different concentrations of IgG antibodies. Methods: A prospective cohort study was conducted from June 2020 to January 2021. This study recruited a convenience sample of adult individuals who where recently diagnosed with COVID-19 and were living in mainland Portugal. A total of 1,695 blood samples were collected from 585 recovered COVID-19 patients up to 9 months after SARS-CoV-2 acute infection. A blood sample was collected at baseline and three, 6 and 9 months after SARS-CoV-2 acute infection to assess the concentration of IgG antibody against SARS-CoV-2. Results: The positivity rate of IgG reached 77.7% in the first 3 months after symptom onset. The IgG persists at all subsequent follow-up time-points, which was 87.7 and 89.2% in the 6th and 9th months after symptom onset, respectively. Three distinct kinetics of antibody response were found within the 9 months after infection. Kinetic 1 (K1) was characterized by a constant low IgG antibody concentration kinetic (group size: 65.2%); kinetic 2 (K2), composed by constant moderate IgG kinetic (group size: 27.5%) and kinetic 3 (K3) characterized by higher IgG kinetic (group size: 7.3%). People with ≥56 years old (OR: 3.33; CI 95%: [1.64; 6.67]; p-value: 0.001) and symptomatic COVID-19 (OR: 2.08; CI 95%: [1.08; 4.00]; p-value: 0.031) had higher odds of a "Moderate IgG kinetic." No significant association were found regarding the "Higher IgG kinetic." Conclusion: Our results demonstrate a lasting anti-spike (anti-S) IgG antibody response at least 9 months after infection in the majority of patients with COVID-19. Younger participants with asymptomatic disease have lower IgG antibody positivity and possibly more susceptible to reinfection. This information contributes to expanding knowledge of SARS-CoV-2 immune response and has direct implications in the adoption of preventive strategies and public health policies.

Results of Comparative Serological Studies of Post-Infection and Post-Vaccination Immunity Characteristics to SARS-CoV-2 in Kidney and Liver Recipients

Introduction. Immunocompromised individuals, such as kidney and liver recipients, are at high risk for a severe course of COVID-19, which explains the special interest in this category of patients in conditions of high incidence of this infection and mass vaccination with available vaccines. Purpose. To study the characteristics of humoral post-infection and post-vaccination immunity to SARS-CoV-2 in kidney and liver recipients based on qualitative and quantitative serotesting. Materials and methods. The study of characteristics of post-infection immunity was carried out in the group of immunocompromised individuals (n=213) including kidney (n=177) and liver (n=26) recipients with PCR confirmed COVID-19, while the study of post-vaccination immunity was carried out in the group of kidney (n=56) and liver (n=12) recipients immunized with Sputnik V (Russia) or Vero Cell (China). In comparative studies, a simple randomized sample was used of immunocompetent patients who recovered from COVID-19 (n=163), corresponding in age and gender to that of the recipients examined, as well as a convenient sample of immunocompetent individuals vaccinated with Sputnik V (n=257) and Vero Cell (n=160). Serotesting for the detection of IgG to S and N proteins of SARS-CoV-2 was carried out by ELISA. Reliable intervals for proportions were calculated using the Wald method. The significance of the detected differences was assessed by the χ2 (chi-square) method. Results. The paper presents data on comparative serological testing of kidney and liver recipients recovered from COVID-19. The detection rate of post-infectious IgG to N and S proteins of SARS-CoV-2 was found to be 88.1% in the group of kidney recipients, 91.3% in the group of liver recipients, and 91.7% in the group of immunocompetent individuals. At the same time, the proportion of N protein seropositive subjects in all groups of observation was lower in comparison with that to S protein, with a significant difference in the group of kidney recipients (59.9% and 86.4%, respectively, p<0.001). The overall dynamics of the decrease in proportion of seropositive individuals during the observation period up to 12 months from the onset of clinical manifestations of infection in both groups of recipients and in the group of immunocompetent individuals had common patterns, however, seroprevalence rates for IgG to N protein significantly differed over time (9–12 months from the onset of the disease) and were much higher in the group of immunocompetent individuals (p<0.001). Despite the presence of general patterns of post-infection antibody response formation, seroprevalence rates to SARS-CoV-2 and the duration of post-infection antibody persistence were slightly lower in the group of kidney recipients than in the group of liver recipients and in immunocompetent individuals. The immunological efficacy of vaccination (the proportion of individuals with post-vaccination antibodies) in the group of kidney recipients was significantly lower (p<0.001) than in the group of immunocompetent patients after both Sputnik V (68.0% and 98.8%, respectively) and Vero Cell (58.1% and 95.0%, respectively) immunization. In liver transplant recipients, there were no significant differences with immunocompetent individuals in terms of post-vaccination response. Conclusion. The data obtained indicate certain differences in characteristics of post-infection and post-vaccination antibody response due to patients' immune status. © 2022, Professionalnye Izdaniya. All rights reserved.

Durable antibody response one year after hospitalization for COVID-19: A longitudinal cohort study.

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.