Long-term persistence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein-specific and neutralizing antibodies in recovered COVID-19 patients.

Understanding antibody responses after natural severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection can guide the coronavirus disease 2019 (COVID-19) vaccine schedule, especially in resource-limited settings. This study aimed to assess the dynamics of SARS-CoV-2 antibodies, including anti-spike protein 1 (S1) immunoglobulin (Ig)G, anti-receptor-binding domain (RBD) total Ig, anti-S1 IgA, and neutralizing antibody against wild-type SARS-CoV-2 over time in a cohort of patients who were previously infected with the wild-type SARS-CoV-2. Between March and May 2020, 531 individuals with virologically confirmed cases of wild-type SARS-CoV-2 infection were enrolled in our immunological study. Blood samples were collected at 3-, 6-, 9-, and 12-months post symptom onset or detection of SARS-CoV-2 by RT-PCR (in asymptomatic individuals). The neutralizing titers against SARS-CoV-2 were detected in 95.2%, 86.7%, 85.0%, and 85.4% of recovered COVID-19 patients at 3, 6, 9, and 12 months after symptom onset, respectively. The seropositivity rate of anti-S1 IgG, anti-RBD total Ig, anti-S1 IgA, and neutralizing titers remained at 68.6%, 89.6%, 77.1%, and 85.4%, respectively, at 12 months after symptom onset. We observed a high level of correlation between neutralizing and SARS-CoV-2 spike protein-specific antibody titers. The half-life of neutralizing titers was estimated at 100.7 days (95% confidence interval = 44.5-327.4 days, R2 = 0.106). These results support that the decline in serum antibody levels over time in both participants with severe disease and mild disease were depended on the symptom severity, and the individuals with high IgG antibody titers experienced a significantly longer persistence of SARS-CoV-2-specific antibody responses than those with lower titers.

Long-term specific IgG response to SARS-CoV-2 nucleocapsid protein in recovered COVID-19 patients.

This study monitored the long-term immune response to severe acute respiratory syndrome coronavirus (SARS-CoV)-2 infection in patients who had recovered from coronavirus disease (COVID)-19. Anti-nucleocapsid immunoglobulin G (anti-N IgG) titer in serum samples collected at a single (N = 302) or multiple time points (N = 229) 3-12 months after COVID-19 symptom onset or SARS-CoV-2 detection in respiratory specimens was measured by semiquantitative chemiluminescent microparticle immunoassay. The 531 patients (966 specimens) were classified according to the presence or absence of pneumonia symptoms. Anti N IgG was detected in 87.5% of patients (328/375) at 3 months, 38.6% (93/241) at 6 months, 23.7% (49/207) at 9 months, and 26.6% (38/143) at 12 months. The anti-N IgG seropositivity rate was significantly lower at 6, 9, and 12 months than at 3 months (P < 0.01) and was higher in the pneumonia group than in the non-pneumonia/asymptomatic group at 6 months (P < 0.01), 9 months (P = 0.04), and 12 months (P = 0.04). The rate started to decline 6-12 months after symptom onset. Anti-N IgG sample/cutoff index was positively correlated with age (r = 0.192, P < 0.01) but negatively correlated with interval between symptom onset and blood sampling (r = - 0.567, P < 0.01). These findings can guide vaccine strategies in recovered COVID-19 patients.

SARS-CoV-2 RNA shedding in recovered COVID-19 cases and the presence of antibodies against SARS-CoV-2 in recovered COVID-19 cases and close contacts, Thailand, April-June 2020.

Coronavirus disease 2019 (COVID-19) is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Although Thailand has been fairly effective at controlling the spread of COVID-19, continued disease surveillance and information on antibody response in recovered patients and their close contacts remain necessary in the absence of approved vaccines and antivirals. Here, we examined 217 recovered COVID-19 patients to assess their viral RNA shedding and residual antibodies against SARS-CoV-2. We also evaluated antibodies in blood samples from 308 close contacts of recovered COVID-19 patients. We found that viral RNA remained detectable in 6.6% of recovered COVID-19 cases and up to 105 days. IgM, IgG, and IgA antibodies against SARS-CoV-2 were detected in 13.8%, 88.5%, and 83.4% of the recovered cases 4-12 weeks after disease onset, respectively. Higher levels of antibodies detected were associated with severe illness patients experienced while hospitalized. Fifteen of the 308 contacts (4.9%) of COVID-19 cases tested positive for IgG antibodies, suggesting probable exposure. Viral clearance and the pattern of antibody responses in infected individuals are both crucial for effectively combating SARS-CoV-2. Our study provides additional information on the natural history of this newly emerging disease related to both natural host defenses and antibody duration.

Clinical features and outcomes of Bacille Calmette-Guérin (BCG)-induced diseases following neonatal BCG Tokyo-172 strain immunization.

BACKGROUND: Bacille Calmette-Guérin (BCG) vaccination at birth may cause mild and benign local adverse effects (AE). More serious AE are rarely reported. OBJECTIVE: To describe clinical features and outcomes of BCG (Tokyo-172 strain)-induce diseases (BCG-ID) that required medical attention at a tertiary care center in Bangkok, Thailand. METHOD: We retrospectively reviewed medical records from January 2007 to December 2016 that were selected by ICD-10 codes. The inclusion criteria were the patients under 3 years of age who developed lymphadenitis, osteitis, or disseminated infections of which BCG was a possible pathogen. Cases were classified into suspected (clinically compatible without laboratory confirmation), probable (suspected cases with M. tuberculosis complex identified), and confirmed BCG-ID (probable cases with molecular confirmation of M. bovis BCG strain). RESULTS: 95 children were identified; 57 (60.0%) were male, and the median age at presenting symptom was 3.5 (range: 0.6-28.7) months. Of these, 25 (26.3%) were suspected, 49 (51.6%) were probable, and 21 (22.1%) were confirmed BCG-ID. Overall, 87 (92%) children had regional lymphadenitis corresponding to the BCG site, 5 (5%) had osteitis, and 3 (3%) had disseminated BCG. Of those with lymphadenitis, average size was 2.2 (range 0.7-5) cm. in diameter and 53% (46/87) had pulmonary involvement. Five children with immunodeficiency; three had disseminated BCG and two had lymphadenitis. Eight (9.2%) patients with lymphadenitis underwent needle aspiration; 57 (65.5%) had surgical excision. All children with BCG osteitis underwent surgical intervention in combination with anti-tuberculosis treatment. One patient with osteitis experienced long-term leg length discrepancy. CONCLUSION: Regional lymphadenitis was the most common feature of BCG-ID requiring medical attention. That none of the BCG osteitis were immunocompromised hosts suggested the potential virulence of BCG in neonates. A systematic national surveillance and reporting system is needed to develop accurate estimates of population incidence and support development of effective vaccine policy.