Construction of pseudotyped human coronaviruses and detection of pre-existing antibodies in the human population

In order to clarify the pre-exist immunity background of different human coronaviruses(HCoV),this study investigated the positive rate of spike(S)protein antibodies of HCoV,including HCoV-severe acute respiratory syndrome(SARS)-associated coronavirus(SARS-CoV-1),severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),Middle East respiratory syndrome coronavirus(MERS-CoV),HCoV-229E,HCoV-NL63,HCoV-HKU1 and HCoV-OC43,before and after the Coronavirus Disease 2019(COVID-19)outbreak.We utilized pseu-dotyped virus-based neutralization assays(PBNA)or enzyme-linked immunosorbent assays(ELISA)to detect antibody levels against HCoV in serum samples collected in 2009-2010 and 2023.The PBNA results showed that neutralizing antibodies against SARS-CoV-1 and the MERS-CoV were negative.In the serum samples from 2009 to 2010,neutralizing antibodies against SARS-CoV-2(D614G)were negative,whereas in the serum sam-ples from 2023,73 samples(73%)showed neutralizing reactions with the SARS-CoV-2 D614G strain,96 sam-ples(96%)with the BA.5 strain,and 91 samples(91%)with the BF.7 strain.Among pre-COVID-19 samples,33%(33/100)showed neutralizing reactions with HCoV-229E and 63%(63/100)with HCoV-NL63.Among post-COVID-19 samples,50%(50/100)showed neutralizing reactions with HCoV-229E and 49%(49/100)with HCoV-NL63.Due to the different receptors of alpha coronavirus genus compared to other beta coron-avirus genus,neutralizing antibodies against HCoV-OC43 and HCoV-HKU1 virus cannot be detected by con-structing corresponding pseudotyped virus.Binding antibodies against HCoV-OC43 and HCoV-HKU1 virus were detected using ELISA.The results revealed that among pre-COVID-19 samples,83%(83/100)and 45%(45/100)had binding activity with HCoV-OC43 and HCoV-HKU1,respectively.Among post-COVID-19 samples,100%(100/100)and 81%(81/100)had binding activity with HCoV-0C43 and HCoV-HKU1,respectively.

Omicron variants breakthrough infection elicited higher specific memory immunity than third dose booster in healthy vaccinees

Homologous booster,heterologous booster,and Omicron variants breakthrough infection(OBI)could improve the humoral immunity against Omicron variants.Questions concerning about memory B cells(MBCs)and T cells immunity against Omicron variants,features of long-term immunity,after booster and OBI,needs to be explored.Here,comparative analysis demonstrate antibody and T cell immunity against ancestral strain,Delta and Omicron variants in Omicron breakthrough infected patients(OBIPs)are comparable to that in Ad5-nCoV boosted healthy volunteers(HVs),higher than that in inactivated vaccine(InV)boosted HVs.However,memory B cells(MBCs)immunity against Omicron variants was highest in OBIPs,followed by Ad5-nCoV boosted and InV boosted HVs.OBIPs and Ad5-nCoV boosted HVs have higher classical MBCs and activated MBCs,and lower naïve MBCs and atypical MBCs relative to both vaccine boosted HVs.Collectively,these data indicate Omicron breakthrough infection elicit higher MBCs and T cells against SARS-CoV-2 especially Omicron variants relative to homologous InV booster and heterologous Ad5-nCoV booster.