Yang Yang

An important limitation that has emerged in the use of adenoviruses for gene therapy has been loss of recombinant gene expression that occurs concurrent with the development of pathology in the organ expressing the transgene. We have used liver-directed approaches to gene therapy in mice to study mechanisms that underlie the problems with transient expression and pathology that have characterized in vivo applications of first-generation recombinant adenoviruses (i.e., those deleted of E1a and E1b). Our data are consistent with the following hypothesis. Cells harboring the recombinant viral genome express the transgene as desired; however, low-level expression of viral genes also occurs. A virus-specific cellular immune response is stimulated that leads to destruction of the genetically modified hepatocytes, massive hepatitis, and repopulation of the liver with nontransgene-containing hepatocytes. These findings suggest approaches for improving recombinant adenoviruses that are based on further crippling the virus to limit expression of nondeleted viral genes.

Neutralizing antibodies could potentially be used as antivirals against the coronavirus disease 2019 (COVID-19) pandemic. Here, we report isolation of four human-origin monoclonal antibodies from a convalescent patient, all of which display neutralization abilities. The antibodies B38 and H4 block binding between the spike glycoprotein receptor binding domain (RBD) of the virus and the cellular receptor angiotensin-converting enzyme 2 (ACE2). A competition assay indicated different epitopes on the RBD for these two antibodies, making them a potentially promising virus-targeting monoclonal antibody pair for avoiding immune escape in future clinical applications. Moreover, a therapeutic study in a mouse model validated that these antibodies can reduce virus titers in infected lungs. The RBD-B38 complex structure revealed that most residues on the epitope overlap with the RBD-ACE2 binding interface, explaining the blocking effect and neutralizing capacity. Our results highlight the promise of antibody-based therapeutics and provide a structural basis for rational vaccine design.

Quantitative real time PCR (RT-PCR) is widely used as the gold standard for clinical detection of SARS-CoV-2. However, due to the low viral load specimens and the limitations of RT-PCR, significant numbers of false negative reports are inevitable, which results in failure to timely diagnose, cut off transmission, and assess discharge criteria. To improve this situation, an optimized droplet digital PCR (ddPCR) was used for detection of SARS-CoV-2, which showed that the limit of detection of ddPCR is significantly lower than that of RT-PCR. We further explored the feasibility of ddPCR to detect SARS-CoV-2 RNA from 77 patients, and compared with RT-PCR in terms of the diagnostic accuracy based on the results of follow-up survey. 26 patients of COVID-19 with negative RT-PCR reports were reported as positive by ddPCR. The sensitivity, specificity, PPV, NPV, negative likelihood ratio (NLR) and accuracy were improved from 40% (95% CI: 27-55%), 100% (95% CI: 54-100%), 100%, 16% (95% CI: 13-19%), 0.6 (95% CI: 0.48-0.75) and 47% (95% CI: 33-60%) for RT-PCR to 94% (95% CI: 83-99%), 100% (95% CI: 48-100%), 100%, 63% (95% CI: 36-83%), 0.06 (95% CI: 0.02-0.18), and 95% (95% CI: 84-99%) for ddPCR, respectively. Moreover, 6/14 (42.9%) convalescents were detected as positive by ddPCR at 5-12 days post discharge. Overall, ddPCR shows superiority for clinical diagnosis of SARS-CoV-2 to reduce the false negative reports, which could be a powerful complement to the RT-PCR.

According to the World Health Organization (WHO) newly updated situation report on March 18th, 2020, the coronavirus disease 2019 (COVID-19) pandemic has confirmed 191,127 cases and claimed 7807 deaths worldwide. 1 6] Currently, there are no approved prophylactic vaccines or therapeutic drugs that are specific to COVID-19. Blocking monoclonal antibodies (mAbs), due to their extraordinary antigen specificity, are one of the best candidates for neutralizing virus infection. Therefore, identifying and cloning blocking mAbs that can specifically target surface viral proteins to block the viral entry to host cells is a very attractive approach for preventing and treating COVID-19, in particular when effective vaccines and therapeutics are unavailable in the outbreak of the COVID-19 pandemic. We then sought to identify and clone blocking mAbs from the memory B cell repertoire of recently recovered COVID-19 patients to prevent the entry of COVID-19 virus to the host cells.

INTRODUCTION: The continual Middle East respiratory syndrome (MERS) threat highlights the importance of developing effective antiviral therapeutics to prevent and treat MERS coronavirus (MERS-CoV) infection. A surface spike (S) protein guides MERS-CoV entry into host cells by binding to cellular receptor dipeptidyl peptidase-4 (DPP4), followed by fusion between virus and host cell membranes. MERS-CoV S protein represents a key target for developing therapeutics to block viral entry and inhibit membrane fusion. Areas covered: This review illustrates MERS-CoV S protein's structure and function, particularly S1 receptor-binding domain (RBD) and S2 heptad repeat 1 (HR1) as therapeutic targets, and summarizes current advancement on developing anti-MERS-CoV therapeutics, focusing on neutralizing monoclonal antibodies (mAbs) and antiviral peptides. Expert opinion: No anti-MERS-CoV therapeutic is approved for human use. Several S-targeting neutralizing mAbs and peptides have demonstrated efficacy against MERS-CoV infection, providing feasibility for development. Generally, human neutralizing mAbs targeting RBD are more potent than those targeting other regions of S protein. However, emergence of escape mutant viruses and mAb's limitations make it necessary for combining neutralizing mAbs recognizing different neutralizing epitopes and engineering them with improved efficacy and reduced cost. Optimization of the peptide sequences is expected to produce next-generation anti-MERS-CoV peptides with improved potency.