Asialoglycoprotein receptor 1 promotes SARS-CoV-2 infection of human normal hepatocytes

Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)causes multi-organ damage,which includes hepatic dysfunction,as observed in over 50%of COVID-19 patients.Angiotensin I converting enzyme(peptidyl-dipeptidase A)2(ACE2)is the primary receptor for SARS-CoV-2 entry into host cells,and studies have shown the presence of intracellular virus particles in human hepatocytes that express ACE2,but at extremely low levels.Consequently,we asked if hepatocytes might express receptors other than ACE2 capable of promoting the entry of SARS-CoV-2 into cells.To address this question,we performed a genome-wide CRISPR-Cas9 activation library screening and found that Asialoglycoprotein receptor 1(ASGR1)promoted SARS-CoV-2 pseudovirus infection of HeLa cells.In Huh-7 cells,simultaneous knockout of ACE2 and ASGR1 prevented SARS-CoV-2 pseudovirus infection.In the immortalized THLE-2 hepatocyte cell line and primary hepatic parenchymal cells,both of which barely expressed ACE2,SARSCoV-2 pseudovirus could successfully establish an infection.However,after treatment with ASGR1 antibody or siRNA targeting ASGR1,the infection rate significantly dropped,suggesting that SARS-CoV-2 pseudovirus infects hepatic parenchymal cells mainly through an ASGR1-dependent mechanism.We confirmed that ASGR1 could interact with Spike protein,which depends on receptor binding domain(RBD)and N-terminal domain(NTD).Finally,we also used Immunohistochemistry and electron microscopy to verify that SARS-CoV-2 could infect primary hepatic parenchymal cells.After inhibiting ASGR1 in primary hepatic parenchymal cells by siRNA,the infection efficiency of the live virus decreased significantly.Collectively,these findings indicate that ASGR1 is a candidate receptor for SARS-CoV-2 that promotes infection of hepatic parenchymal cells.

Human IFN-k Inhibited Respiratory RNA Virus Replication Dependent on Cell-to-Cell Interaction in the Early Phase

Background:Interferon kappa(IFN-k)is a type I interferon(IFN-I)that inhibits virus replication by evoking interferon-stimulated genes(ISGs).However,as an evolutionarily ancient interferon,IFN-k may function differently from the later emerged interferon-a and b.Methods:Conventional molecular biology methods were used to determine the localization of IFN-k and its structure and function.In addition,we employed RT-PCR,western blot,and RNA-Seq technologies to characterize the ISGs expression profile and antiviral activities exerted by IFN-k or IFN-a2.Results:Human IFN-k exists in two forms upon ectopic expression,one located on the cell membrane and the other secreted outside the cells.The membrane-anchored IFN-k showed the ability to induce ISGs and curtail RNA virus replication,whereas the secreted IFN-k failed to do so.Structural analyses indicated that 1-27aa at the N-terminus was the signal peptide,and 28-37aa was predicted as the transmembrane region.However,our data demonstrated that both of them were not associated with membrane localization of IFN-k;the former influenced the expression and secretion of IFN-k,and the latter had an impact on the induction of ISGs.In addition,prokaryotic purified soluble mature human IFN-k was also capable of inducing ISGs and inhibiting RNA virus replication.Importantly,human IFN-k induced a faster ISG response but with a lower intensity and a shorter half-life than the response of IFN-a2.In contrast,IFN-a2 started to function later but was stronger and more durable than IFN-k.Conclusions:Human IFN-k-induced ISG response and inhibited respiratory RNA virus replication dependent on cell-to-cell interactions.In addition,compared with IFN-a2,IFN-k exerted effects more rapidly in the early phase,with less intensity and a shorter half-life.Therefore,IFN-k may constitute the first line of IFN-I against respiratory virus infections.

Neutralization of five SARS-CoV-2 variants of concern by convalescent and BBIBP-CorV vaccinee serum

The prevalence of SARS-CoV-2 variants of concern(VOCs) is still escalating throughout the world. However, the level of neutralization of the inactivated viral vaccine recipients’ sera and convalescent sera against all VOCs,including B.1.1.7(Alpha), B.1.351(Beta), P.1(Gamma), B.1.617.2(Delta), and B.1.1.529(Omicron) remains to be lack of comparative analysis. Therefore, we constructed pseudoviruses of five VOCs using a lentiviral-based system and analyzed their viral infectivity and neutralization resistance to convalescent and BBIBP-CorV vaccinee serum at different times. Our results show that, compared with the wild-type strain(WT), five VOC pseudoviruses showed higher infection, of which B.1.617.2 and B.1.1.529 variant pseudoviruses exhibited higher infection rates than wild-type or other VOC strains, respectively. Sera from 10 vaccinated individuals at the 1, 3and 5-month post second dose or from 10 convalescent at 14 and 200 days after discharge retained neutralizing activity against all strains but exhibited decreased neutralization activity significantly against the five VOC variant pseudoviruses over time compared to WT. Notably, 100%(30/30) of the vaccinee serum samples showed more than a 2.5-fold reduction in neutralizing activity against B.1.1.529, and 90%(18/20) of the convalescent serum samples showed more than 2.5-fold reduction in neutralization against B.1.1.529. These findings demonstrate the reduced protection against the VOCs in vaccinated and convalescent individuals over time, indicating that it is necessary to have a booster shot and develop new vaccines capable of eliciting broad neutralization antibodies.