SARS-CoV-2 antibody kinetics in blood donors with a previously positive SARS-CoV-2 antibody test within a seroprevalence survey.

The persistence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies is a matter of importance regarding the coronavirus disease 19 (COVID-19) pandemic. To observe antibody dynamics, 105 blood donors, positive for SARS-CoV-2 antibodies by a lateral flow test within a seroprevalence study, were included in this study. Thirty-nine (37%) of 105 the donors were confirmed positive by a total Ig Wantai enzyme-linked immunosorbent assay (ELISA). Three (8%) in this group of 39 reported severe and 26/39 (67%) mild to moderate COVID-19 symptoms. By further ELISA-testing, 33/39 (85%) donors were initially positive for IgG antibodies, 31/39 (79%) for IgA, and 32/39 (82%) for IgM, while 27/39 (69%) were positive for all three isotypes. Persistence of IgG, IgA, and IgM was observed in 73%, 79%, and 32% of donors, respectively, after 6-9 months of observation. For IgM antibodies, the decline in the proportion of positive donors was statistically significant (p = 0.002) during 12 months observation, for IgG only the decline at 3 months was statistically significant (p = 0.042). Four donors exhibited notable increases in antibody levels. In conclusion, persistent SARS-CoV-2 IgA antibodies and IgG antibodies at 6-9 months are present in approximately three of four individuals with previous mild to moderate COVID-19.

Levring MB ，Holm DK ，Nilsson AC ，Bauer JM ，Jensen IS ，Davidsen JR ，Rasmussen LD ，Sprogøe U ，Lillevang ST ... -  《-》

SARS-CoV-2 antibodies: IgA correlates with severity of disease in early COVID-19 infection.

Timing of detection of immunoglobulin G (IgG), immunoglobulin A (IgA), and immunoglobulin M (IgM) antibodies against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and their use to support the diagnosis are of increasing interest. We used the Gold Standard Diagnostics ELISA to evaluate the kinetics of SARS-CoV-2 IgG, IgA, and IgM antibodies in sera of 82 hospitalized patients with polymerase chain reaction (PCR)-confirmed coronavirus disease 2019 (COVID-19). Serum samples were collected 1-59 days post-onset of symptoms (PoS) and we examined the association of age, sex, disease severity, and symptoms' duration with antibody levels. We also tested sera of 100 ambulatory hospital employees with PCR-confirmed COVID-19 and samples collected during convalescence, 35-57 days PoS. All but four of the admitted patients (95.1%) developed antibodies to SARS-CoV-2. Antibodies were detected within 7 days PoS; IgA in 60.0%, IgM in 53.3%, and IgG in 46.7% of samples. IgG positivity increased to 100% on Day 21. We did not observe significant differences in the rate of antibody development in regard to age and sex. IgA levels were highest in patients with a severe and critical illness. In multiple regression analyses, only IgA levels were statistically significantly correlated with critical disease (p = .05) regardless of age, sex, and duration of symptoms. Among 100 ambulatory hospital employees who had antibody testing after 4 weeks PoS only 10% had positive IgA antibodies. The most frequently isolated isotype in sera of employees after 30 days PoS was IgG (88%). IgA was the predominant immunoglobulin in early disease and correlated independently with a critical illness. IgG antibodies remained detectable in almost 90% of samples collected up to two months after infection.

Zervou FN ，Louie P ，Stachel A ，Zacharioudakis IM ，Ortiz-Mendez Y ，Thomas K ，Aguero-Rosenfeld ME ... -  《-》

Assessment of the COVID-19 pandemic progression in Ecuador through seroprevalence analysis of anti-SARS-CoV-2 IgG/IgM antibodies in blood donors.

Coronavirus Disease 2019 (COVID-19) is a severe respiratory illness caused by the RNA virus SARS-CoV-2. Globally, there have been over 759.4 million cases and 6.74 million deaths, while Ecuador has reported more than 1.06 million cases and 35.9 thousand deaths. To describe the COVID-19 pandemic impact and the vaccinations effectiveness in a low-income country like Ecuador, we aim to assess the seroprevalence of IgG and IgM antibodies against SARS-CoV-2 in a sample from healthy blood donors at the Cruz Roja Ecuatoriana. The present seroprevalence study used a lateral flow immunoassay (LFIA) to detect anti-SARS-CoV-2 IgG and IgM antibodies in months with the highest confirmed case rates (May 2020; January, April 2021; January, February, June, July 2022) and months with the highest vaccination rates (May, June, July, August, December 2021) in Quito, Ecuador. The IgG and IgM seroprevalence were also assessed based on sex, age range, blood type and RhD antigen type. The sample size was 8,159, and sampling was performed based on the availability of each blood type. The results showed an overall IgG and IgM seroprevalence of 47.76% and 3.44%, respectively. There were no differences in IgG and IgM seroprevalences between blood groups and sex, whereas statistical differences were found based on months, age range groups, and RhD antigen type. For instance, the highest IgG seroprevalence was observed in February 2022 and within the 17-26 years age range group, while the highest IgM seroprevalence was in April 2021 and within the 47-56 years age range group. Lastly, only IgG seroprevalence was higher in RhD+ individuals while IgM seroprevalence was similar across RhD types. This project contributes to limited data on IgG and IgM antibodies against SARS-CoV-2 in Ecuador. It suggests that herd immunity may have been achieved in the last evaluated months, and highlights a potential link between the RhD antigen type and COVID-19 susceptibility. These findings have implications for public health strategies and vaccine distribution not only in Ecuador but also in regions with similar characteristics.

Gaviria A ，Tamayo-Trujillo R ，Paz-Cruz E ，Cadena-Ullauri S ，Guevara-Ramírez P ，Ruiz-Pozo VA ，Cevallos F ，Aguirre-Tello V ，Risueño K ，Yánez MP ，Cabrera-Andrade A ，Zambrano AK ... -  《Frontiers in Cellular and Infection Microbiology》

Analytical and clinical validation of an ELISA for specific SARS-CoV-2 IgG, IgA, and IgM antibodies.

The development of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) serological tests is massive. The external validation of their performance is needed before use in clinical routine practice. Our study aims at assessing the analytical and clinical performance of two enzyme-linked immunosorbent assay tests detecting antibodies directed against the virus nucleocapsid protein: The NovaLisa SARS-CoV-2 immunoglobulin G (IgG), immunoglobulin A (IgA), and immunoglobulin M (IgM) test (NovaTec) allowing a separate detection of each antibody and the Platelia SARS-CoV-2 Total Ab test (Bio-Rad) detecting total antibodies (IgM, IgA, and IgG). Two-hundred and eight coronavirus disease 2019 samples from 48 quantitative reverse transcription-polymerase chain reaction (RT-qPCR) confirmed patients were used to perform the sensitivity analysis. Non-SARS-CoV-2 sera (n = 79) with a potential cross-reaction to SARS-CoV-2 immunoassays were included in the specificity analysis. In addition, using receiver operator characteristic curves, adapted cut-off for improvement of the performances were proposed. The kinetics of these antibodies was also assessed over 8 weeks. Two weeks after the RT-qPCR positive detection, the NovaLisa test shows a sensitivity and specificity of 94.9% (95% confidence interval [CI]: 83.1%-98.6%) and 96.2% (95% CI: 89.4%-98.7%) for IgG, of 89.7% (95% CI: 76.4%-95.9%) and 98.7% (95% CI: 93.2%-98.8%) for IgA, and of 48.7% (95% CI: 33.9%-63.8%) and 98.7% (95% CI: 93.2%-99.8%) for IgM. With the Platelia system, the specificity and sensitivity were 97.4% (95% CI: 92.1%-99.7%) and 94.9% (95% CI: 87.7%-98.0%) for total antibodies using the adapted cut-offs. The NovaLisa and the Platelia tests have satisfactory analytical performances. The clinical performances are excellent for IgG, IgA, and total antibodies especially if the cut-off is optimized.

Tré-Hardy M ，Wilmet A ，Beukinga I ，Favresse J ，Dogné JM ，Douxfils J ，Blairon L ... -  《-》

Low prevalence of antibodies against SARS-CoV-2 among voluntary blood donors in Guangzhou, China.

Since the first case of COVID-19 reported in late December of 2019 in Wuhan, China, the SARS-CoV-2 virus has caused approximately 20 million infections and 732 thousand deaths around the world by 11 August 2020. Although the pathogen generally infects the respiratory system, whether it is present in the bloodstream and whether it poses a threat to the blood supply during the period of the outbreak is of serious public concern. In this study, we used enzyme-linked immunosorbent assay (ELISA) to screen total antibodies against SARS-CoV-2 in 2199 blood donors, who had donated blood at the Guangzhou Blood Center during the epidemic. The Ig-reactive samples were further characterized for IgA, IgG, and IgM subtypes by ELISA and viral nucleic acid by real-time polymerase chain reaction. Among the 2199 plasma samples, seven were reactive under total antibodies' screening. Further testing revealed that none of them had detectable viral nucleic acid or IgM antibody, but two samples contained IgA and IgG. The IgG antibody titers of both positive samples were 1:16 and 1:4, respectively. Our results indicated a low prevalence of past SARS-CoV-2 infection in our blood donors, as none of the tests were positive for viral nucleic acid and only 2 out of 2199 (0.09%) of samples were positive for IgG and IgA. There would be a limited necessity for the implementation of such testing in blood screening in a COVID-19 low-risk area.

Xu R ，Huang J ，Duan C ，Liao Q ，Shan Z ，Wang M ，Rong X ，Li C ，Fu Y ，Wang H ... -  《-》