ABSTRACT
The effectiveness of SARS-CoV-2 vaccines and therapeutic antibodies has been limited by the continuous emergence of viral variants, and by the restricted diffusion of antibodies from circulation into the sites of respiratory virus infection. Here, we report the identification of two highly conserved regions on Omicron variant RBD recognized by broadly neutralizing antibodies. Based on this finding, we generated a bispecific single-domain antibody that was able to simultaneously and synergistically bind these two regions on a single Omicron variant RBD as revealed by Cryo-EM structures. This inhalable antibody exhibited exquisite neutralization breadth and therapeutic efficacy in mouse models of SARS-CoV-2 infections. The structures also deciphered an uncommon cryptic epitope within the spike trimeric interface that may have implications for the design of broadly protective SARS-CoV-2 vaccines and therapeutics.
ABSTRACT
The global spread of SARS-CoV-2 is posing major public health challenges. One unique feature of SARS-CoV-2 spike protein is the insertion of multi-basic residues at the S1/S2 subunit cleavage site, the function of which remains uncertain. We found that the virus with intact spike (Sfull) preferentially enters cells via fusion at the plasma membrane, whereas a clone (Sdel) with deletion disrupting the multi-basic S1/S2 site instead utilizes a less efficient endosomal entry pathway. This idea was supported by the identification of a suite of endosomal entry factors specific to Sdel virus by a genome-wide CRISPR-Cas9 screen. A panel of host factors regulating the surface expression of ACE2 was identified for both viruses. Using a hamster model, animal-to-animal transmission with the Sdel virus was almost completely abrogated, unlike with Sfull. These findings highlight the critical role of the S1/S2 boundary of the SARS-CoV-2 spike protein in modulating virus entry and transmission.
ABSTRACT
The SARS-CoV-2 infection is spreading rapidly worldwide. Efficacious antiviral therapeutics against SARS-CoV-2 is urgently needed. Here, we discovered that protoporphyrin IX (PpIX) and verteporfin, two FDA-approved drugs, completely inhibited the cytopathic effect produced by SARS-CoV-2 infection at 1.25 M and 0.31 M respectively, and their EC50 values of reduction of viral RNA were at nanomolar concentrations. The selectivity indices of PpIX and verteporfin were 952.74 and 368.93, respectively, suggesting broad margin of safety. Importantly, PpIX and verteporfin prevented SARS-CoV-2 infection in mice adenovirally transduced with human ACE2. The compounds, sharing a porphyrin ring structure, were shown to bind viral receptor ACE2 and interfere with the interaction between ACE2 and the receptor-binding domain of viral S protein. Our study suggests that PpIX and verteporfin are potent antiviral agents against SARS-CoV-2 infection and sheds new light on developing novel chemoprophylaxis and chemotherapy against SARS-CoV-2.
ABSTRACT
The pandemic of Coronavirus Disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a major global health threat. Epidemiological studies suggest that bats are the natural zoonotic reservoir for SARS-CoV-2. However, the host range of SARS-CoV-2 and intermediate hosts that facilitate its transmission to humans remain unknown. The interaction of coronavirus with its host receptor is a key genetic determinant of host range and cross-species transmission. SARS-CoV-2 uses angiotensin-converting enzyme 2 (ACE2) as the receptor to enter host cells in a species-dependent manner. It has been shown that human, palm civet, pig and bat ACE2 can support virus entry, while the murine ortholog cannot. In this study, we characterized the ability of ACE2 from diverse species to support viral entry. We found that ACE2 is expressed in a wide range of species, with especially high conservation in mammals. By analyzing amino acid residues of ACE2 critical for virus entry, based on structure of SARS-CoV spike protein interaction with human, bat, palm civet, pig and ferret ACE2, we identified approximately eighty ACE2 proteins from mammals that could potentially mediate SARS-CoV-2 entry. We chose 48 representative ACE2 orthologs among eighty orthologs for functional analysis and it showed that 44 of these mammalian ACE2 orthologs, including those of domestic animals, pets, livestock, and animals commonly found in zoos and aquaria, could bind SARS-CoV-2 spike protein and support viral entry. In contrast, New World monkey ACE2 orthologs could not bind SARS-CoV-2 spike protein and support viral entry. We further identified the genetic determinant of New World monkey ACE2 that restricts viral entry using genetic and functional analyses. In summary, our study demonstrates that ACE2 from a remarkably broad range of species can facilitate SARS-CoV-2 entry. These findings highlight a potentially broad host tropism of SARS-CoV-2 and suggest that SARS-CoV-2 might be distributed much more widely than previously recognized, underscoring the necessity to monitor susceptible hosts to prevent future outbreaks.
ABSTRACT
Chronic hepatitis B virus (HBV) infection remains a major public health threat worldwide. Current antiviral drugs can effectively inhibit the replication of HBV, but they fail to achieve a complete cure. As the original template for HBV replication, covalently closed circular DNA (cccDNA) is intrinsically stable in vivo and is regarded as the molecular basis for persistent HBV infection and the key target for the cure of HBV infection. Studies on biosynthesis, metabolism, and regulation of HBV cccDNA have been limited by the low copy number of cccDNA within cells and the lack of sensitive and reliable detection methods. Establishment of appropriate research models of cccDNA helps to understand related biological processes. This article reviews the latest research advances in cell models and mouse models of HBV cccDNA, in order to facilitate future studies on HBV virology and development of antiviral drugs against HBV.
ABSTRACT
Objective To observe the electroretinogram (ERG) photopic negative response (PhNR) of idiopathic macular hole (IMH) in stage 2 by vitrectomy with or without internal limiting membrane peeling (ILMP).Methods Twenty-three stage 2 IMH patients (23 eyes) were enrolled in this prospective study.All patients received the best corrected visual acuity (BCVA),optical coherence tomography and flash-ERG examinations.The patients were randomly divided into group A (11 eyes,vitrectomy) and B (12 eyes,vitrectomy with ILMP).There was no significant difference in BCVA (t=0.96,P=0.350),diameter of macular hole (MH) (t=3.21,P=0.580) and the PhNR amplitude (t=0.98,P=0.353) in group A and B.All patients underwent 25G vitrectomy,ILMP was carried out in group B.The follow-up time was 3 to 6 months,with the mean follow-up time of 4.3 months.BCVA,MH closure rate and PhNR amplitude in group A and B were analyzed before and after surgery.Results Three months after surgery,10 eyes (90.9％) gained MH closure but 1 eye (9.1％) failed in group A.In group B,12 eyes (100.0％) gained MH closure.There was no significant difference in MH closure rate between the two groups (P=0.462).The mean BCVA of group A and B was 0.69 ± 0.24 and 0.65 ± 0.22,there was no significant difference between the two groups (t=0.49,P=0.722).The amplitude of PhNR in group A was (36.647.4) μtV,which was lower than the pre-surgery PhNR,but the difference was not significant (t=0.73,P=0.472).The amplitude of PhNR in group B was (27.1 ± 12.4) μV,which was lower than that the presurgery PhNR,and the difference was significant (t =3.56,P =0.002).The difference of PhNR amplitude in group A and B was statistically significant (t=2.17,P=0.042).Conclusion Compared with non-ILMP,vitrectomy combined with ILMP will significantly reduce the PhNR amplitude ofIMH in stage 2.
