No abstract

SARS-CoV-2 emerged in late 2019 and has since spread around the world, causing a pandemic of the respiratory disease COVID-19. Detecting antibodies against the virus is an essential tool for tracking infections and developing vaccines. Such tests, primarily utilizing the enzyme-linked immunosorbent assay (ELISA) principle, can be either qualitative (reporting positive/negative results) or quantitative (reporting a value representing the quantity of specific antibodies). Quantitation is vital for determining stability or decline of antibody titers in convalescence, efficacy of different vaccination regimens, and detection of asymptomatic infections. Quantitation typically requires two-step ELISA testing, in which samples are first screened in a qualitative assay and positive samples are subsequently analyzed as a dilution series. To overcome the throughput limitations of this approach, we developed a simpler and faster system that is highly automatable and achieves quantitation in a single-dilution screening format with sensitivity and specificity comparable to those of ELISA.

Invasive Aspergillosis (I.A.) resulting from infection by Aspergillus fumagatus (A.f.) is a leading cause of death in immunosuppressed populations. There are limited therapeutic options for this disease and currently no vaccine. There is evidence some anti-A.f. monoclonal antibodies can provide protection against I.A. However, vaccine development has been impeded by a paucity of immunological targets on this organism demonstrated to provide protective responses. Sialylated oligosaccharide epitopes found on a variety of pathogens including fungi and Group B Streptococci (GBS) are thought to be major virulence factors of these organisms facilitating pathogen attachment to host cells and modulating complement activation and phagocytosis. As some of these oligosaccharide structures are conserved across kingdoms, we screened a panel monoclonal antibodies raised against GBS serotypes for reactivity to A.f. This approach revealed that SMB19, a GBSIb type-specific mAb, reacts with A.f. conidia and hyphae. The presence of this antibody in mice, as a result of passive or active immunization, or by enforced expression of the SMB19 heavy chain as a transgene, results in significant protection in both intravenous and airway-induced models of I.A. This study demonstrates that some antibodies generated against bacterial polysaccharides engage fungal pathogens and promote their clearance in vivo and thus provide rationale of alternative strategies for the development of vaccines or therapeutic monoclonal antibodies against these organisms.

The need for high-affinity, SARS-CoV-2-specific monoclonal antibodies (mAbs) is critical in the face of the global COVID-19 pandemic, as such reagents can have important diagnostic, research, and therapeutic applications. Of greatest interest is the ~ 300 amino acid receptor binding domain (RBD) within the S1 subunit of the spike protein because of its key interaction with the human angiotensin converting enzyme 2 (hACE2) receptor present on many cell types, especially lung epithelial cells. We report here the development and functional characterization of 29 nM-affinity mouse SARS-CoV-2 mAbs created by an accelerated immunization and hybridoma screening process. Differing functions, including binding of diverse protein epitopes, viral neutralization, impact on RBD-hACE2 binding, and immunohistochemical staining of infected lung tissue, were correlated with variable gene usage and sequence.