Biology subjects

Beale, R.

Publications and source records attributed to Beale, R..

2 recordsLinked to original sources

bioRxiv2020

Pre-existing and de novo humoral immunity to SARS-CoV-2 in humans

Several related human coronaviruses (HCoVs) are endemic in the human population, causing mild respiratory infections1. Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the etiologic agent of Coronavirus disease 2019 (COVID-19), is a recent zoonotic infection that has quickly reached pandemic proportions2,3. Zoonotic introduction of novel coronaviruses is thought to occur in the absence of pre-existing immunity in the target human population. Using diverse assays for detection of antibodies reactive with the SARS-CoV-2 spike (S) glycoprotein, we demonstrate the presence of pre-existing humoral immunity in uninfected and unexposed humans to the new coronavirus. SARS-CoV-2 S-reactive antibodies were readily detectable by a sensitive flow cytometry-based method in SARS-CoV-2-uninfected individuals and were particularly prevalent in children and adolescents. These were predominantly of the IgG class and targeted the S2 subunit. In contrast, SARS-CoV-2 infection induced higher titres of SARS-CoV-2 S-reactive IgG antibodies, targeting both the S1 and S2 subunits, as well as concomitant IgM and IgA antibodies, lasting throughout the observation period of 6 weeks since symptoms onset. SARS-CoV-2-uninfected donor sera also variably reacted with SARS-CoV-2 S and nucleoprotein (N), but not with the S1 subunit or the receptor binding domain (RBD) of S on standard enzyme immunoassays. Notably, SARS-CoV-2-uninfected donor sera exhibited specific neutralising activity against SARS-CoV-2 and SARS-CoV-2 S pseudotypes, according to levels of SARS-CoV-2 S-binding IgG and with efficiencies comparable to those of COVID-19 patient sera. Distinguishing pre-existing and de novo antibody responses to SARS-CoV-2 will be critical for our understanding of susceptibility to and the natural course of SARS-CoV-2 infection.

immunology↗

bioRxiv2020

Non-canonical autophagy drives alternative ATG8 conjugation to phosphatidylserine

Autophagy is a fundamental catabolic process essential for development, homeostasis and proper immune function 1. During autophagy, a cascade of ATG proteins target intracellular cargoes for lysosomal degradation and recycling 2. This pathway utilises a unique post-translational modification, the conjugation of ATG8 proteins to phosphatidylethanolamine (PE) at autophagosomes, which modulates cargo selection and maturation. ATG8 lipidation also occurs during non-canonical autophagy, a parallel pathway involving Single Membrane ATG8 Conjugation (SMAC) to endolysosomal compartments, which plays a key role in phagocytosis and other processes 3. It has been widely assumed that SMAC involves the same lipidation of ATG8 to PE, but this has yet to be formally tested. Here, we show that ATG8 undergoes alternative lipidation to phosphatidylserine (PS) during non-canonical autophagy/SMAC. Using mass spectrometry, we find that activation of SMAC, by pharmacological agents 4,5, or during non-canonical autophagy processes such as LC3-associated phagocytosis 6,7 and Influenza A virus infection 8, induces the covalent conjugation of ATG8 to PS, as well as PE. This alternative lipidation event is dependent on the ATG16L1 WD40 domain, and occurs at PS enriched endolysosomal membranes. Importantly, we find that the ATG8-PS and ATG8-PE adducts are differentially delipidated by isoforms of the ATG4 family, indicating significant molecular distinctions and mechanisms between these two species. Together, these results provide an important new insight into autophagy signalling, revealing an alternative form of the hallmark ATG8-lipidation event, so widely used to define and assay autophagy. Furthermore, ATG8-PS lipidation provides a specific molecular signature for non-canonical autophagy, uncovering a novel means of detecting and monitoring this emerging pathway.

cell biology↗