Reyes-Ruiz, A. | Search bioRxiv

bioRxiv2023

Temperature sensitivity of bat antibodies links metabolic state with antigen-recognition diversity

Bat immune system features multiple unique properties such as dampened inflammatory responses and increased tissue protection, explaining their long lifespan and tolerance to viral infections. Here, we demonstrated that body temperature fluctuations corresponding to different physiological states in bats exert a dramatic impact on their antibody repertoires. At elevated temperatures typical for flight, IgG from Myotis myotis and Nyctalus noctula showed elevated antigen binding strength and diversity, recognizing both pathogen-derived antigens and autoantigens. The opposite was observed at temperatures reflecting inactive physiological states. This behavior was not observed for IgG antibodies of human and other mammals, or antibodies of birds. Importantly, diversification of bat antibody specificities resulted in preferential recognition of damaged endothelial and epithelial cells, indicating an anti-inflammatory function. The temperature-sensitivity of bat antibodies was mediated by the variable regions of immunoglobulin molecules. Additionally, we revealed specific molecular features of bat IgG such as low thermodynamic stability and implication of hydrophobic interactions in antigen binding as well as high prevalence of polyreactivity. Overall, our results extend the understanding of bat tolerance to disease and inflammation and highlight the link between metabolism and immunity. This might have important repercussions for human health in the future.

immunology↗

bioRxiv2022

Evolutionary trajectory of the physicochemical mechanism of interaction of SARS-CoV-2 spike protein with ACE2

SARS-CoV-2 infects cells by attachment to its receptor - the angiotensin converting enzyme 2 (ACE2). Regardless of the wealth of structural data, little is known about the physicochemical mechanism of interactions of the viral spike (S) protein with ACE2 and how this mechanism has evolved during the pandemic. Here, we applied experimental and computational approaches to characterize the molecular interaction of S proteins from SARS-CoV-2 variants of concern (VOC). Data on kinetics, activation- and equilibrium thermodynamics of binding of the receptor binding domain (RBD) from VOC with ACE2 as well as data from computational protein electrostatics revealed a profound remodeling of the physicochemical characteristics of the interaction during the evolution. Thus, as compared to RBDs from Wuhan strain and other VOC, Omicron RBD presented as a unique protein in terms of conformational dynamics and types of non-covalent forces driving the complex formation with ACE2. Viral evolution resulted in a restriction of the RBD structural dynamics, and a shift to a major role of polar forces for ACE2 binding. Further, we investigated how the reshaping of the physicochemical characteristics of interaction affect the binding specificity of S proteins. Data from various binding assays revealed that SARS-CoV-2 Wuhan and Omicron RBDs manifest capacity for promiscuous recognition of unrelated human proteins, but they harbor distinct reactivity patterns. These findings might contribute for mechanistic understanding of the viral tropism, and capacity to evade immune responses during evolution.

biochemistry↗