Pseudorabies (also known as Aujeszky's disease) is a viral disease caused by pseudorabies virus (PRV). First isolated in 1902, classical PRV has circulated globally since the 1980s, especially in l...

SARS-CoV-2, the causative agent of COVID-19¹, features a receptor-binding domain (RBD) for binding to the host cell ACE2 protein^1–6. Neutralizing antibodies that block RBD-ACE2 interaction are candidates for the development of targeted therapeutics^7–17. Llama-derived single-domain antibodies (nanobodies, ~15 kDa) offer advantages in bioavailability, amenability, and production and storage owing to their small sizes and high stability. Here, we report the rapid selection of 99 synthetic nanobodies (sybodies) against RBD by in vitro selection using three libraries. The best sybody, MR3 binds to RBD with high affinity (K_D = 1.0 nM) and displays high neutralization activity against SARS-CoV-2 pseudoviruses (IC₅₀ = 0.42 μg mL⁻¹). Structural, biochemical, and biological characterization suggests a common neutralizing mechanism, in which the RBD-ACE2 interaction is competitively inhibited by sybodies. Various forms of sybodies with improved potency have been generated by structure-based design, biparatopic construction, and divalent engineering. Two divalent forms of MR3 protect hamsters from clinical signs after live virus challenge and a single dose of the Fc-fusion construct of MR3 reduces viral RNA load by 6 Log₁₀. Our results pave the way for the development of therapeutic nanobodies against COVID-19 and present a strategy for rapid development of targeted medical interventions during an outbreak.

The ongoing pandemic of coronavirus disease 2019 (COVID-19), caused by infection with human coronavirus 2019 (HCoV-19 / SARS-CoV-2 / 2019-nCoV), is a global threat to the human population. Here, we briefly summarize the available data for the zoonotic origins of HCoV-19, with reference to the other two epidemics of highly virulent coronaviruses, SARS-CoV and MERS-CoV, which cause severe pneumonia in humans. We propose to intensify future efforts for tracing the origins of HCoV-19, which is a very important scientific question for the control and prevention of the pandemic.

Monkeypox is a zoonotic disease caused by monkeypox virus (MPXV), in which outbreaks mainly occurred in West and Central Africa, with only sporadic spillovers to countries outside Africa due to international travel or close contact with wildlife. During May 2022, multiple countries in Europe, North and South America, Australia, Asia, and Africa reported near-simultaneous outbreaks of MPXV, the first time that patient clusters were reported over such a large geographical area. Cases have no known epidemiological links to MPXV-endemic countries in West or Central Africa. Real-time PCR is currently the gold standard for MPXV diagnostics, but it requires trained laboratory personnel and specialized equipment, and results can only be obtained after several hours. A rapid and simple-to-operate point-of-care diagnostic test for MPXV is crucial for limiting its spread and controlling outbreaks. Here, three recombinase-based isothermal amplification assays (RPA/RAA) for the rapid detection of MPXV isolates were developed. These three assays target the MPXV G2R gene, and the limit of detection for these systems is approximately 10⁰ copies of DNA per reaction. The assays were found to be specific and non-cross reactive against other pox viruses, such as vaccinia virus, and the results can be visualized within 20–30 min. The assays were validated with DNA extracted from 19 clinical samples from suspected or confirmed MPXV patients from Central Africa, and found to be consistent with findings from traditional qPCR. These results provide a solid platform for the early diagnosis of potential MPXV cases, and will help with the control and prevention of current and future outbreaks.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has spread rapidly worldwide since it was confirmed as the causative agent of COVID-19. Molecular diagnosis of the disease is typically performed via nucleic acid-based detection of the virus from swabs, sputum or bronchoalveolar lavage fluid (BALF). However, the positive rate from the commonly used specimens (swabs or sputum) was less than 75%. Immunological assays for SARS-CoV-2 are needed to accurately diagnose COVID-19. Sera were collected from patients or healthy people in a local hospital in Xiangyang, Hubei Province, China. The SARS-CoV-2 specific IgM antibodies were then detected using a SARS-CoV-2 IgM colloidal gold immunochromatographic assay (GICA). Results were analysed in combination with sera collection date and clinical information. The GICA was found to be positive with the detected 82.2% (37/45) of RT-qPCR confirmed COVID-19 cases, as well as 32.0% (8/25) of clinically confirmed, RT-qPCR negative patients (4–14 days after symptom onset). Investigation of IgM-negative, RT-qPCR-positive COVID-19 patients showed that half of them developed severe disease. The GICA was found to be a useful test to complement existing PCR-based assays for confirmation of COVID-19, and a delayed specific IgM antibody response was observed among COVID-19 patients with severe progression.

Nipah virus (NiV) is a zoonotic pathogen with airborne transmission and high case fatality rates in humans. There is currently no treatment or vaccine against NiV infection approved for humans or animals, therefore early diagnosis is the key to control any potential outbreaks. In this study, we developed an optimized one-pot assay using recombinase polymerase amplification (RPA) coupled to CRISPR/Cas13a for the molecular detection of NiV. The one-pot RPA-CRISPR/Cas13a assay for NiV detection was specific and did not cross-react against other selected (re)-emerging pathogens. The sensitivity of the one-pot RPA-CRISPR/Cas13a assay for NiV detection can detect as little as 10³ cp/μL of total synthetic NiV cDNA. The assay was then validated with simulated clinical samples. The results for the one-pot RPA-CRISPR/Cas13a assay could be visualized with either fluorescence or lateral flow strips for convenient clinical or field diagnostics, providing a useful supplement to the gold-standard qRT-PCR assay for detecting NiV detections.