The results show that Omicron infection induces low levels of neutralizing antibodies in immunocompetents.

In a recent study posted on medRxiv* Preprint server, researchers evaluated variant-specific leads Neutralizing antibody Severe acute respiratory syndrome of several SARS-CoV-2 strains against coronavirus 2 (SARS-CoV-2) spike (S) and nucleocapsid (N) proteins.

Omicron is highly contagious and highly antigenic, and SARS-CoV- among individuals previously infected with SARS-CoV-2 or vaccinated against the virus with a vaccine based on the ancestral strain of SARS-CoV-2. 2 Easy to cause infection. Omicron is highly contagious, but its pathogenicity is low. This suggests that the induction of strong serological immunity by Omicron may end the pandemic of coronavirus disease 2019 (COVID-19).

About research

In this study, researchers are induced by D614G, alpha, beta, gamma, delta, omicron (BA.1, BA.2, and BA.1.1 sublineage), kappa, lambda, eta, and iota strains. The Japanese antibody titer was evaluated. Individuals with a history of COVID-19 or not vaccinated. Not previously infected with SARS-CoV-2 but previously vaccinated with Pfizer or model name messenger ribonucleic acid (mRNA) vaccine (n = 8 per vaccine group) or previously delta (n = 13) or alpha (n = 13) Individuals of the same age infected with n = 13) n = 10) strains were also included in the study for comparison.

Convalescent sera were obtained from 23 participants in the Specchio-COVID-19 cohort enrolled based on the COVID-19 study in Geneva, Switzerland. Participants were diagnosed with Omicron infection, which does not require hospitalization. Serum was collected 3 to 74 days (mean 39 days) after a positive polymerase chain reaction (PCR) diagnosis of COVID-19.

Data on vaccination status, vaccine type, vaccination date, and date of COVID-19 diagnosis confirmed by PCR were obtained with the help of a questionnaire filled out by participants at the time of blood sampling. The results of the PCR test were further validated by centralized state registry data and questionnaires filled out by participants during the follow-up.

Mutations responsible for SARS-CoV-2 infection were determined based on the PCR-positive diagnosis date. Variants were considered alpha, delta, or omicron if the dates were March-May 2021, July-September 2021, or January-February 2022, respectively.

Mutant-specific neutralizing antibody titers were evaluated using a cell-free assay based on interference with S-ACE2 (angiotensin converting enzyme 2) binding. The assay used the SARS-CoV-2 strain of trimer S protein. In addition, a cell-based Omicron BA.1 live virus neutralization assay was used for further data integration. As an extended analysis, five serum samples with the highest anti-S titers from the Omicron recovery phase were examined for their neutralizing activity against live D614G, Alpha, Beta, Gamma, Delta, and Omicron BA.2 strains. ..

result

In this study, all vaccinated participants induced only anti-S titers, whereas delta and alpha convalescent patients induced anti-S and anti-N antibodies. Most serum samples during the Omicron recovery phase (17 of 20) induce anti-S and anti-N antibodies, albeit at low levels, and Omicron induces less SARS-CoV-2 neutralization than other strains. It shows that.

In the neutralization assay, most alpha convalescent patients induced neutralizing antibodies against the S and D614G, gamma, eta, and kappa strains of the same family, but with a slight decrease. Effectiveness Against Beta, Delta (and its AY4.2 sublineage), Iota, and Lambda strains. They showed an average 2 logarithmic reduction in neutralizing titers relative to the Omicron subline.

The delta convalescent period showed anti-S titers against most strains, including the Delta AY4.2 substrain, but showed a significant reduction in neutralization of the beta and omicron substrains. During the Omicron recovery period, none of the strains showed significantly lower anti-S titers.

In addition, only 4 and 9 participants elicited anti-S titers close to the median effective dose of 1:50 (ED).₅₀) Threshold for Omicron BA.1 and BA.1.1 substrains, marked reduction in anti-S titer for BA.2. The sera of vaccinated participants showed strong neutralization of most strains, but were substantially lower in beta and even lower in the Omicron substrain.

In the live virus neutralization assay, the alpha recovery agent was unable to neutralize Omicron BA.1, but the two delta recovery agents (the highest anti-Omicron S titer in the binding interference assay) were SARS-CoV-2-induced cells. Demonstrated a slight prevention of degenerative effects (CPE). Most Omicron recovery period (17 out of 23), ED₅₀ Serum dilutions from 1:10 to 1:30 showed low levels of omicron neutralization when the binding interference assay was 7.8 or higher.

Extended analysis showed low BA.2 neutralization in almost all sera. However, sera from two participants showed detectable neutralization of the D614G, Delta, and Alpha strains. The serum of study participants was unable to neutralize the virus isolates, but all isolates were neutralized by the sera of vaccinated individuals.

Conclusion

In summary, the study results show that previous SARS-CoV-2 vaccination or infection with alpha and to a lesser extent Delta induced strong neutralization of most SARS-CoV-2 strains, but less in beta. , Omicron showed even less.

In contrast, the Omicron convalescent period showed a low neutralizing titer against the cognate SARS-CoV-2 and was unable to neutralize other strains. The findings emphasize that the immunogenicity of Omicron infection is low and cannot provide the immunoprotection needed to suppress COVID-19 and should not be considered as a substitute for vaccination.

*Important Notices

medRxiv publishes unpeer-reviewed preliminary scientific reports and should not be considered definitive, guide clinical / health-related behaviors, or be treated as established information.