Evaluation of SARS-CoV-2-Neutralizing Nanobody Using Virus Receptor Binding Domain-Administered Model Mice.

Due to the rapid spread of coronavirus disease 2019 (COVID-19), there is an urgent requirement for the development of additional diagnostic tools for further analysis of the disease. The isolated nanobody Nb11-59 binds to the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) receptor-binding domain (RBD) with high affinity to neutralize the virus and block the angiotensin-converting enzyme 2- (ACE2-) RBD interaction. Here, we introduce a novel nanobody-based radiotracer named 68Ga-Nb1159. The radiotracer retained high affinity for the RBD and showed reliable radiochemical characteristics both in vitro and in vivo. Preclinical positron emission tomography (PET) studies of 68Ga-Nb1159 in mice revealed its rapid clearance from circulation and robust uptake into the renal and urinary systems. Fortunately, 68Ga-Nb1159 could specifically reveal the distribution of the RBD in mice. This study also helped to evaluate the pharmacodynamic effects of the neutralizing nanobody. Moreover, 68Ga-Nb1159 may be a promising tool to explore the distribution of the RBD and improve the understanding of the virus. In particular, this study identified a novel molecular radioagent and established a reliable evaluation method for specifically investigating the RBD through noninvasive and visual PET technology.

Peptidomic analysis of mycobacterial secreted proteins enables species identification

Pulmonary disease arising from slow‐growing mycobacterial infections has emerged as an increasingly prevalent clinical concern over the past two to three decades. Proteins belonging to the family of ESAT‐6 secretion (Esx) systems play critical roles in the virulence of most pathogenic mycobacterial species and are associated with drug resistance. However, no clinical applications can detect and discriminate the expression of species‐specific variants of these proteins in clinical samples, such as early growth cultures, for rapid diagnosis of specific mycobacterial infections, which may require distinct interventions. Conventional immunoassay approaches are not suitable for this purpose due to the significant degree of conservation of Esx proteins among species. Herein we describe the development of a novel immunoprecipitation‐coupled mass spectrometry assay that can distinguish Esx proteins that are expressed by slow‐growing mycobacterial species commonly detected in clinical isolates. This approach uses custom antibodies raised against single semi‐conserved peptide regions in M. tuberculosis (Mtb) EsxB and EsxN to capture corresponding peptides from protein orthologs of mycobacteria associated with human respiratory infections, including Mtb, M. avium, M. intracellulare, M. kansasii, M. gordonae, and M. marinum, to detect these species in standard clinical cultures at the first sign mycobacterial growth to allow rapid disease diagnosis.