A human monoclonal antibody potently pan-neutralizes SARS-CoV-2 VOCs by targeting RBD invariant sites (preprint)

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a global pandemic of novel corona virus disease (COVID-19). The neutralizing monoclonal antibodies (mAbs) targeting the receptor binding domain (RBD) of SARS-CoV-2 are among the most promising strategies to prevent and treat COVID-19. However, SARS-CoV-2 variants of concern (VOCs) profoundly reduced the efficacies of most of mAbs and vaccines approved for clinical use. Herein, we demonstrated mAb 35B5 efficiently neutralizes both wild-type (WT) SARS-CoV-2 and VOCs, including B.1.617.2 (delta) variant, in vitro and in vivo. Cryo-electron microscopy (cryo-EM) revealed that 35B5 neutralizes SARS-CoV-2 by targeting a unique epitope that avoids the prevailing mutation sites on RBD identified in circulating VOCs, providing the molecular basis for its pan-neutralizing efficacy. The 35B5-binding epitope could also be exploited for the rational design of a universal SARS-CoV-2 vaccine.

Acquisition of the L452R mutation in the ACE2-binding interface of Spike protein triggers recent massive expansion of SARS-Cov-2 variants (preprint)

The recent rise in mutational variants of SARS-CoV-2, especially with changes in the Spike protein, is of significant concern due to the potential ability for these mutations to increase viral infectivity, virulence and/or ability to escape protective antibodies. Here, we investigated genetic variations in a 414-583 amino acid region of the Spike protein, partially encompassing the ACE2 receptor-binding domain (RBD), across a subset of 570 nasopharyngeal samples isolated between April 2020 and February 2021, from Washington, California, Arizona, Colorado, Minnesota and Illinois. We found that samples isolated since November have an increased number of amino acid mutations in the region, with L452R being the dominant mutation. This mutation is associated with a recently discovered CAL.20C viral variant from clade 20C, lineage B.1.429, that since November-December 2020 is associated with multiple outbreaks and is undergoing massive expansion across California. In some samples, however, we found a distinct L452R-carrying variant of the virus that, upon detailed analysis of the GISAID database genomes, is also circulating primarily in California, but emerged even more recently. The newly identified variant derives from the clade 20A (lineage B.1.232) and is named CAL.20A. We also found that the SARS-CoV-2 strain that caused the only recorded case of infection in an ape - gorillas in the San Diego Zoo, reported in January 2021 - is CAL.20A. In contrast to CAL.20C that carries two additional to L452R mutations in the Spike protein, L452R is the only mutation found in CAL.20A. According to the phylogenetic analysis, however, emergence of CAL.20C was also specifically triggered by acquisition of the L452R mutation. Further analysis of GISAID-deposited genomes revealed that several independent L452R-carrying lineages have recently emerged across the globe, with over 90% of the isolates reported between December 2020 -February 2021. Taken together, these results indicate that the L452R mutation alone is of significant adaptive value to SARS-CoV-2 and, apparently, the positive selection for this mutation became particularly strong only recently, possibly reflecting viral adaptation to the containment measures or increasing population immunity. While the functional impact of L452R has not yet been extensively evaluated, leucine-452 is positioned in the receptor-binding motif of RBD, in the interface of direct contact with the ACE2 receptor. Its replacement with arginine is predicted to result in both a much stronger binding to the receptor and escape from neutralizing antibodies. If true, this in turn might lead to significantly increased infectivity of the L452R variants, warranting their close surveillance and in-depth functional studies.

Environmental monitoring shows SARS-CoV-2 contamination of surfaces in food plants (preprint)

The SARS-CoV-2 pandemic has presented new challenges to food manufacturers. In addition to preventing the spread of microbial contamination of food, with SARS-CoV-2, there is an additional focus on preventing SARS-CoV-2 infections in food plant personnel. During the early phase of the pandemic, several large outbreaks of Covid-19 occurred in food manufacturing plants resulting in deaths and economic loss. In March of 2020, we assisted in implementation of environmental monitoring programs for SARS-CoV-2 in 116 food production facilities. All participating facilities had already implemented measures to prevent symptomatic personnel from coming to work. During the study period, from March 17, 2020 to September 3, 2020, 1.23% of the 22,643 environmental samples tested positive for SARS-CoV-2, suggesting that infected individuals are actively shedding virus. Virus contamination was commonly found on frequently touched surfaces. Most plants managed to control their environmental contamination when they became aware of the positive findings. Comparisons of the personnel test results to environmental contamination in one plant showed a good correlation between the two. Our work illustrates that environmental monitoring for SARS-CoV-2 can be used as a surrogate for identifying the presence of asymptomatic and pre-symptomatic personnel in workplaces and may aid in controlling infection spread. HighlightsO_LIEnvironmental contamination by SARS-CoV-2 virus was detected in food plants C_LIO_LIOut of 22,643 environmental swabs, 278 (1.23%) were positive for SARS-CoV-2 C_LIO_LIFrequently touched surfaces had the most contamination C_LIO_LISurface testing for SARS-CoV-2 may indicate presence of asymptomatic carriers C_LI

Disease severity dictates SARS-CoV-2-specific neutralizing antibody responses in COVID-19 (preprint)

COVID-19 patients exhibit differential disease severity after SARS-CoV-2 infection. It is currently unknown as to the correlation between the magnitude of neutralizing antibody (NAb) responses and the disease severity in COVID-19 patients. In a cohort of 59 recovered patients with disease severity including severe, moderate, mild and asymptomatic, we observed the positive correlation between serum neutralizing capacity and disease severity, in particular, the highest NAb capacity in sera from the patients with severe disease, while a lack of ability of asymptomatic patients to mount competent NAbs. Furthermore, the compositions of NAb subtypes were also different between recovered patients with severe symptoms and with mild-to-moderate symptoms. These results reveal the tremendous heterogeneity of SARS-CoV-2-specific NAb responses and their correlations to disease severity, highlighting the needs of future vaccination in COVID-19 patients recovered from asymptomatic or mild illness.

Human monoclonal antibodies block the binding of SARS-CoV-2 spike protein to angiotensin converting enzyme 2 receptor (preprint)

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a global pandemic of novel corona virus disease (COVID-19). To date, no prophylactic vaccines or approved therapeutic agents are available for preventing and treating this highly transmittable disease. Here we report two monoclonal antibodies (mAbs) cloned from memory B cells of patients recently recovered from COVID-19, and both mAbs specifically bind to the spike (S) protein of SARS-CoV-2, block the binding of receptor binding domain (RBD) of SARS-CoV-2 to human angiotensin converting enzyme 2 (hACE2), and effectively neutralize S protein-pseudotyped virus infection. These human mAbs hold the promise for the prevention and treatment of the ongoing pandemic of COVID-19.

Precautions are Needed for COVID-19 Patients with Coinfection of Common Respiratory Pathogens (preprint)

Background: With the ongoing outbreak of Coronavirus Disease 2019 (COVID-19), infected patients within and beyond the epidemic area, Wuhan, China, showed different epidemiological and clinical characteristics. There is a paucity of data concerning coinfection with other common respiratory pathogens in COVID-19 patients outside of Wuhan. Methods: We conducted a double-centre study recruiting 68 patients with severe acute respiratory coronavirus 2 (SARS-CoV-2) infection confirmed by nucleic acid testing in Qingdao and Wuhan from January 17 to February 16, 2020. Indirect immunofluorescence was performed to detect the specific IgM antibody against common respiratory pathogens in collected acute phase serum. Results: Of the 68 patients with SARS-CoV-2 infection, 30 (44.12%) were from Qingdao. The median age of Qingdao and Wuhan patients were 50 (IQR: 37-59) and 31 (IQR: 28-38) years, respectively, and the majority of patients were female in Qingdao (60.00%) and Wuhan (55.26%). Among COVID-19 patients in Qingdao, 24 (80.00%) of them had IgM antibodies against at least one respiratory pathogen, whereas only one (2.63%) of the patients in Wuhan had positive results for serum IgM antibody detection (P<0.0001). The most common respiratory pathogens detected in Qingdao COVID-19 patients were influenza virus A (60.00%) and influenza virus B (53.33%), followed by mycoplasma pneumoniae (23.33%) and legionella pneumophila (20.00%). While the pattern for coinfection in patients with community-acquired pneumonia in Qingdao was quite different, with a positive rate of only 20.90%. Interpretation: We reported a large proportion of COVID-19 patients with coinfection of seasonal respiratory pathogens in Qingdao, northeast China, which differed greatly from the patients in Wuhan, central China. Precautions are needed when dealing with COVID-19 patients beyond the epidemic centre who have coinfection with other respiratory pathogens. We highly recommend adding SARS-CoV-2 to routine diagnostic testing in capable hospitals to prevent misdetection of the virus.