| BackgroundCoronavirus Disease 2019(COVID-19)is a novel Coronavirus caused by Severe Acute Respiratory Syndrome Coronavirus 2(SARS-CoV-2).Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),a deadly lower respiratory tract infection and infectious disease with extrapulmonary manifestations,which was first reported in Wuhan in late 2019 and early 2020.Due to its rapid spread and serious damage,it has attracted wide attention around the world.By January 20,2023,COVID-19 has infected 663,248,631 people worldwide and caused 6,709,387 deaths.A variety of novel coronavirus vaccines have been used worldwide for mass vaccination to establish a herd of immunity barriers,inhibit the spread of SARSCoV-2 and its variants,and reduce the severity of infection.However,it is still incomplete to study the level of humoral and cellular immune responses induced by the two dose of inactivated vaccine followed by homologous and heterologous booster vaccine and Omicron variant breakthrough infection.ObjectiveTo explore the humoral and cellular immune responses of healthy volunteers who are inoculated with two doses of inactivated novel coronavirus vaccine and the third dose of homologous and heterologous booster shots and Omicron variant breakthrough infection patients at different time points,and to clarify their dynamic immunological characteristics,through the exploration,it can provide effective theoretical reference for the prevention and control of COVID-19.MethodsPlasma will be collected from healthy volunteers and patients infected by Omicron variant breakthrough infection after 0-22 days.Healthy volunteers are the ones who inject the second dose of In V after 14 days and 6 months,and the third homologous or heterologous boost dose after 14 days and 1 month.And the patients infected by Omicron variant breakthrough infection are unvaccinated,pre-vaccinated inactivated vaccine.Sars-cov-2-specific antibodies(anti-ancestral,anti-delta and anti-omicron)Receptor binding domain(RBD)-Ig G titer were detected by enzymelinked immunosorbent assay(ELISA),which was used to dynamically analyze and compare the level of humoral immune response.In addition,the levels of SARSCoV-2-specific memory B cells(MBCs)and T cell immune responses were detected by enzyme-linked immunospot(Elispot)and Flow cytometry after one-month peripheral blood mononuclear cells were isolated from the above people.Then,compare and analyze the results.ResultsThe level of humoral immune response study included a total of 73 healthy volunteers and 77 OBIPs who had received two doses of inactivated vaccine.The median mean age of HVs was 37 years(interquartile range [IQR]): 27-44.5 years old),and there was no significant difference with OBIPs(median mean age =39,IQR=29-53,p > 0.05).There was also no significant difference in gender between OBIPs and vaccinated HVs(p > 0.05).Among OBIPs,nine patients did not receive any SARS-CoV-2 vaccine(unvaccinated OBIPs),68 patients completed a two-dose In V vaccination schedule prior to infection(pre-vaccinated OBIPs),and the median interval between second dose vaccination and Omicron variant infection was 241days(IQR: 20-3900 days).There were no significant differences in age and gender between unvaccinated and pre-vaccinated OBIPs(p > 0.05).There was no difference in Ct value of nucleic acid between unvaccinated and pre-vaccinated OBIPs nasopharyngeal samples(p > 0.05).The asymptomatic infection rate of OBIPs preinoculated with In V was 36.76%(25/68),which was higher than that of noninoculated OBIPs(0%(0/9),p=0.027).In addition,OBIPs Open reading frames 1a/b(orf1ab)and Nucleocapsid protein were detected in different clinical symptoms(asymptomatic,mild and common).There was no significant difference in the Ct value of RT-PCR of NP gene(p > 0.05).The pre-vaccinated OBIPs had higher antiancestral RBD-Ig G,anti-Delta-RBD-igg,and anti-Omicron-RBD-igg titers compared to the unvaccinated OBIPs.The titers of anti-ancestral RBD-Ig G increased sharply between 0 and 5 DPI,The Geometric mean titer(GMT)of anti-Delta-RBDigg and anti-Omicron-RBD-igg were 3.3-fold and 12.0-fold lower than those of antiancestral RBD-Ig G,respectively.Between 11 and 22 DPI,the GMTS of anti-deltaRBD-igg and anti-Omicron-RBD-igg increased to 35112 and 28186,2.6-and 3.2-fold lower than the titers of anti-ancestral RBD-Ig G,respectively.The titers of antiancestral RBD-Ig G,anti-Delta-RBD-igg and anti-Omicron-RBD-igg decreased by25.2-fold,5.6-fold and 4.5-fold,respectively,at 6 months after HVs vaccination with the second dose of In V compared with those at 14 days after vaccination.The titers of anti-ancestral RBD-Ig G,anti-Delta-RBD-igg,and anti-Omicron-RBD-igg induced by the heterologous Ad5-nCoV booster were significantly higher than those induced by the homologous In V booster and were comparable to OBIPs preinoculated with In V.Homologous In V and heterologous Ad5-nCoV boosters enhance humoral immunity to Omicron variants.Among them,heterologous Ad5-nCoV enhancer is a better choice.For studying on the level of cellular immune response that recruit 33 patients received homologous In V booster,21 patients received heterologous Ad5-nCoV booster,and 10 patients received OBIPs.The median age of HVs with heterologous Ad5-nCoV enhancer was 28(IQR=25-38.5)years,which was significantly lower than that of HVs with homologous In V enhancer(median age =37,IQR=28.5-45.5)and OBIPs(median age =39,IQR=33.8-56.3),P=0.004,the difference is statistically significant.However,there is no significant difference between them in gender analysis,P=0.053,which is not statistically significant.The study analysis showed that the T-cell immunity of OBIPs against Ancestral and Delta and Omicron variants of SARS-CoV-2 was comparable to that of HVs vaccinated with heterologous Ad5-nCoV booster(P >0.05,no statistical difference),but higher than that of HVs vaccinated with homologous In V booster.P <0.05,the difference was statistically significant.However,MBCs showed the highest immunity against SARS-CoV-2 and its variants among OBIPs,followed by HVs vaccinated with heterologous Ad5-nCoV booster,homologous In V booster,P <0.05,the difference was statistically significant.In addition,OBIPs and HVs vaccinated with heterologous Ad5-nCoV booster had higher classical MBCs and activated MBCs,and lower naive MBCs and atypical MBCs compared to HVs vaccinated with inactivated vaccine,P <0.05,indicating statistically significant differences.The overall data showed that Omicron breakthrough infection elicited higher levels of memory B and T cells against SARS-CoV-2 relative to homologous In V enhancers and heterologous Ad5-nCoV enhancers.Conclusion1 The early humoral immune response induced by Omicron variant breakthrough infection helps to alleviate symptoms,but the patients unvaccinated and infected Omicron have low levels of antibodies against Omicron variant and require further vaccination.2 Compared with a homologous In V boost,a heterologous Ad5-nCoV boost induced higher levels of humoral immunity and spike-specific memory B-and Tcell immune responses in Ancestral SARS-CoV-2 strains,comparable to those in Omicron infections.3 Omicron breakthrough infection resulted in higher levels of memory B-cell immunity against Omicron variants compared with healthy individuals who received booster doses of both vaccines. |
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