Humoral immune response characteristics of the susceptible populations after the infection of SARS-CoV-2 BA.5 strain (preprint)

This study compared the humoral immune characteristics of children, elderly people, pregnant women, and adults infected with BA.5 and XBB strains in Guangzhou, China. It was found that binding and neutralizing antibodies the titers against distinct SARS-CoV-2 strains were low in the acute-phase sera of BA.5 infected patients, while the corresponding titers were significantly increased in the convalescent phase, the antibody titers against the Wuhan strain were the highest. Regardless of whether they were vaccinated, BA.5 infection did not induce high neutralizing antibodies against XBB. During the recovery phase, the titers of antiviral antibodies in the vaccinated population are more robust than those in the unvaccinated population. For BA.5 infections, the specific binding and neutralizing antibody titers in the children group were lower compared to other population groups. In the convalescence period of the disease, the titers of neutralizing antibodies against Wuhan, BA.5 and XBB strains induced by BA.5 infections are significantly correlated in pairs. XBB can induce a broader and balanced antiviral humoral immune response than BA.5 as a first-time infected strain. This finding can provide a reference for the judgment of the future epidemic law of SARS-CoV-2, and provide a scientific basis for developing novel COVID-19 vaccines, especially for discovering customized vaccines and immune strategies for different populations.

High-Specificity Targets in SARS-CoV-2 N Protein for Serological Antibody Detection (preprint)

Background The current coronavirus disease (COVID-19) pandemic has created a pressing need to diagnose and screen a large number of close contacts of confirmed and suspected cases. Numerous nucleic acid detection kits are being rapidly developed and approved for viral etiological diagnosis; however, these are limited by the number of false negatives produced in clinical practice. Therefore, there is an urgent need to establish serological detection methods to serve as supplementary diagnostics.Methods We (1) performed a conservation and specificity analysis of the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid (N) protein, which is the main target of serological diagnosis; (2) integrated various B-cell epitope prediction methods to obtain possible dominant epitope regions for the N protein; (3) applied ELISA to analyze differences in the serological antibody levels for different epitopes; and (4) identified N protein epitopes for IgG and IgM with high specificity.Results SARS-CoV-2 strains showed low mutation rates for the N protein, and the construction of a phylogeny was a good characterization of its molecular evolutionary lineage in relation to other coronaviruses. SARS-CoV-2 showed the closest genetic relationship with SARS-CoV, which showed multiple consecutive long conserved regions at the amino acid level, but differed substantially from other coronaviruses. Tests targeting the SARS-CoV-2 N protein produced strong positive results in SARS-CoV patients in recovery. Of the five epitope dominant regions, using N18-39 and N183-197 for IgG and IgM detection, respectively, can effectively overcome the limitations of cross-reactivity.Conclusions The patients infected with both SARS viruses may exhibit cross-reactivity when using the N protein for antibody detection. However, there are regions of the N protein that can be used for antibody detection and some of these regions showed good specificity even between SARS-CoV-2 and SARS-CoV, and the antibody levels detected were consistent with those detected by the complete N protein. These findings provide a basis for serological diagnosis of SARS-CoV-2 patients, and research ideas for developing vaccines.

SARS-CoV-2: characteristics and current advances in research.

Coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 infection has spread rapidly across the world and become an international public health emergency. Both SARS-CoV-2 and SARS-CoV belong to subfamily Coronavirinae in the family Coronaviridae of the order Nidovirales and they are classified as the SARS-like species while belong to different cluster. Besides, viral structure, epidemiology characteristics and pathological characteristics are also different. We present a comprehensive survey of the latest coronavirus-SARS-CoV-2-from investigating its origin and evolution alongside SARS-CoV. Meanwhile, pathogenesis, cardiovascular disease in COVID-19 patients, myocardial injury and venous thromboembolism induced by SARS-CoV-2 as well as the treatment methods are summarized in this review.