Longitudinal profile of neutralizing and binding antibodies in vaccinated and convalescent COVID-19 cohorts by chemiluminescent immunoassays.

Surrogate rapid serological assay was urgently demanded for accessibly interpretation of immunity potency and duration of neutralizing antibody against SARS-CoV-2. The longitudinal trajectory of antibody profile with a reliable large-scale assay was crucial to judge the protective immune status, avoid futile therapy and provide insight into the booster vaccination minimizing the risk of COVID-19. A total of 195 volunteers were enrolled for a two-doses procedure (0 and 28 days) of inactive vaccination, as well as ten COVID-19 convalescents. The serum was collected at six time point and detected by chemiluminescent immunoassay with SARS-CoV-2 neutralizing antibody (Nab), SARS-CoV-2 RBD immunoglobulin G (IgG) antibody (RBD IgG) and RBD total antibody. The diagnostic results and the correlation of antibody level were evaluated among three serological (Nab, RBD IgG, and RBD total antibody) assay, as well as with an authorized cPass kit (Nab). Referred to the assay-specific threshold, the seroconversion rate and dynamic titer of antibody were exhibited from 0 to 56 days since vaccination. There was no difference observed with diagnostic results between neutralizing and RBD IgG antibody (p > 0.05). Both diagnostic results of neutralizing and RBD IgG antibody testing differentiated from RBD total antibody assay (p < 0.05). The coefficient of correlation (R) was above 0.90 among the levels of those three antibodies, more than 0.60 in comparison with neutralizing antibody by cPass enzyme-linked immunoassay. The "S" varying pattern for various antibodies level was observed with time extension after vaccination. The seroconversion rate was below 11.1% in 2 weeks after the priming dose, while the value climbed to 81% in 1 week after the boosting dose. The seroconversion rate was maintained around 91%. The inactive vaccine elicited 81-fold higher antibody levels after finished the vaccination schedule than that at the basic point. Besides, the level of neutralizing antibody induced by vaccine was found with a 0.2-fold ratio by comparison with that in COVID-19 convalescents. The humoral immune response products including SARS-CoV-2 neutralizing, RBD IgG antibody and total antibody and the varying pattern of the antibody profile could be rapidly detected by CILA method. Meanwhile, the continuing and dynamic determination was attributed to evaluate the protection effect of humoral immunity against the SARS-CoV-2 infection.

Dou X ，Wang E ，Jiang R ，Li M ，Xiong D ，Sun B ，Zhang X ... -  《Immunity Inflammation and Disease》

Chemiluminescence Immunoassay Based Serological Immunoassays for Detection of SARS-CoV-2 Neutralizing Antibodies in COVID-19 Convalescent Patients and Vaccinated Population.

Yin Q ，Zhang Y ，Lian L ，Qu Y ，Wu W ，Chen Z ，Pei R ，Chen T ，Sun L ，Li C ，Li A ，Li J ，Li D ，Wang S ，Guan W ，Liang M ... -  《Viruses-Basel》

A cohort analysis of SARS-CoV-2 anti-spike protein receptor binding domain (RBD) IgG levels and neutralizing antibodies in fully vaccinated healthcare workers.

The waning of humoral immunity after COVID-19 vaccine booster (third dose) has not yet been fully evaluated. This study updates data on anti-SARS-CoV-2 spike protein receptor binding domain (S-RBD) binding antibodies (bAb) and neutralizing antibodies (NAb) levels in individuals with homologous vaccination 3-4 months after receiving the booster dose. Fifty-five healthcare workers (HCW) from Padova University-Hospital were asked to collect serum samples for determining antibodies (Ab) at 12 (t12) and 28 (t28) days, at 6 months (t6m) after their first Comirnaty/BNT162b2 inoculation, and 3-4 months after receiving the 3rd homologous booster dose. HCW were monitored weekly for SARS-CoV-2 infection. Ab titers were measured by two chemiluminescent immunoassays, one targeting the S-RBD immunoglobulin G (IgG), and one surrogate viral neutralization test (sVNT), measuring NAb. Twenty of the HCW had natural COVID-19 infection (COVID+) at different times, before either the first or the second vaccination. Median S-RBD IgG and NAb levels and their interquartile ranges 3-4 months after the 3rd dose were 1,076 (529-3,409) kBAU/L and 15.8 (11.3-38.3) mg/L, respectively, for COVID-, and 1,373 (700-1,373) kBAU/L and 21 (12.8-53.9) mg/L, respectively, for COVID+. At multivariate regression analyses, with age and gender included as covariates, S-RBD IgG bAb and sVNT NAb levels were closely associated with the time interval between serological determination and the 3rd vaccine dose (log10 βcoeff=-0.013, p=0.012 and log10 βcoeff=-0.010, p=0.025) for COVID+, whereas no such association was found in COVID- individuals. The third booster dose increases anti-SARS-CoV-2 Ab levels, elevated levels persisting for up to 3-4 months. Waning of Ab levels appears to be less pronounced for COVID+ individuals.

Padoan A ，Cosma C ，Della Rocca F ，Barbaro F ，Santarossa C ，Dall'Olmo L ，Galla L ，Cattelan A ，Cianci V ，Basso D ，Plebani M ... -  《-》

Dynamic observation of SARS-CoV-2 IgM, IgG, and neutralizing antibodies in the development of population immunity through COVID-19 vaccination.

Currently, mass vaccine inoculation against coronavirus disease-2019 (COVID-19) has been being implemented globally. Rapid and the large-scale detection of serum neutralizing antibodies (NAbs) laid a foundation for assessing the immune response against SARS-CoV-2 infection and vaccine. Additional assessments include the duration of antibodies and the optimal time for a heightened immune response. The performance of five surrogate NAbs-three chemiluminescent immunoassay (CLIA) and two enzyme-linked immunosorbent assays (ELISAs)-and specific IgM and IgG assays were compared using COVID-19-vaccinated serum (n = 164). Conventional virus neutralization test (cVNT) was used as a criterion and the diagnostic agreement and correlation of the five assays were evaluated. We studied the antibody responses after the two-dose vaccine in volunteers up to 6 months. The sensitivity and specificity of five surrogate NAb assays ranged from 84% to 100%. Our cVNT results indicated great consistency with the surrogate assays. At 28 days after primary vaccination, the seropositivities of the NAbs, IgG, and IgM were 6%, 4%, and 13%, respectively. After the booster dose, seropositivities reached 14%, 65%, and 97%, respectively. Six months after receipt of the second dose, the NAb positive rate was eventually maintained at 66%. In all COVID-19 convalescents, patients were detected with 100% NAb sat three months after discharge. COVID-19 vaccine induced a humoral immune response lasting at least six months. Rapid serological detection was used as a proxy for identifying changes in immunity levels and as a guide to whether an individual may require a booster vaccination.

Jiang R ，Dou X ，Li M ，Wang E ，Hu J ，Xiong D ，Zhang X ... -  《-》

Antibody Responses to BNT162b2 Vaccination in Japan: Monitoring Vaccine Efficacy by Measuring IgG Antibodies against the Receptor-Binding Domain of SARS-CoV-2.

Fujigaki H ，Yamamoto Y ，Koseki T ，Banno S ，Ando T ，Ito H ，Fujita T ，Naruse H ，Hata T ，Moriyama S ，Takahashi Y ，Suzuki T ，Murakami T ，Yoshida Y ，Yagura Y ，Oyamada T ，Takemura M ，Kondo M ，Iwata M ，Saito K ... -  《Microbiology Spectrum》