Ruiz Silva, M. | bioRxiv Science

bioRxiv2023

TMPRSS2 activation of Omicron lineage Spike glycoproteins is regulated by TMPRSS2 cleavage of ACE2

Continued high-level spread of SARS-CoV-2 has enabled an accumulation of changes within the Spike glycoprotein, leading to resistance to neutralising antibodies and concomitant changes to entry requirements that increased viral transmission fitness. Herein, we demonstrate a significant change in angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) dependent entry by primary SARS-CoV-2 isolates that occurred upon arrival of Omicron lineages. Mechanistically we show this shift to be a function of two distinct ACE2 pools based on TMPRS22 association with the ACE2 Collectrin-Like Domain (CLD). In engineered cells overexpressing ACE2 and TMPRSS2, ACE2/TMPRSS2 complexes led to either augmentation or attenuation of viral infectivity of pre-Omicron and Omicron lineages, respectively. Mutagenesis of the ACE2-CLD TMPRSS2 cleavage site in ACE2 restored infectivity across all Omicron lineages through enabling ACE2 binding that facilitated TMPRSS2 activation of viral fusion. Our data supports the evolution of Omicron lineages towards the use of ACE2 unable to form complexes with TMPRSS2 and consistent with ACE2 structure and function as a chaperone for many tissue specific amino acid transport proteins. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=95 SRC="FIGDIR/small/558930v4_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@1c86cf0org.highwire.dtl.DTLVardef@16815feorg.highwire.dtl.DTLVardef@7be9e1org.highwire.dtl.DTLVardef@137de1c_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical Abstract:C_FLOATNO ACE2-TMPRSS2 pool model and evolution of SARS-CoV-2 tropism.A. &-B. ACE2-TMPRSS2 pool model to reconcile the evolving entry requirements of SARS-CoV-2 and changes in viral tropism in vivo. A. Both SARS-CoV-1 and early SARS-CoV-2 (pre-Omicron) lineages have molecular dual tropism, with efficient entry when ACE2 (blue protein) can form complexes with TMPRSS2 (green protein) and in settings where TMPRSS2 is excluded from ACE2 (C4-ACE2 CLD). In both settings ACE2 initially engages SARS-CoV-2 spike and fusion is then triggered through TMPRSS2 cleavage of the Spike S2 domain B. Over time, the dual tropism for two distinct pools of ACE2 (with and without TMPRSS2) has been lost, with consolidation towards ACE2 where TMPRSS2 is no longer in a complex. With the arrival of Omicron lineages, ACE2-TMPRSS2 complexes could no longer enable efficient Spike S2 cleavage and fusogenic activation (TMPRSS2 "off" confirmation"). Rather, only TMPRSS2 uncoupled from ACE2 could facilitate the latter cleavage of S2. C. Over time this has further consolidated over generations of omicron lineages from 2022 lineages (BA.1, BA.2 and BA.5) through to 2023 lineages (XBB.1.5) and now in 2024 JN.1 lineages such as KP.3. Overall, this supports the initial molecular tropism of early SARS-CoV-2 clades to be similar to that observed for SARS-CoV-1, with dual tropism across both ACE2 pools and replication proceeding in tissues where ACE2-TMPRSS2 complexes would be prevalent (e.g. Lung). The evolution away from ACE2-TMPRSS2 complexes towards ACE2 where TMPRSS2 is structurally uncoupled (e.g. ACE2 as a chaperone for solute carriers SLCA619 or SLCA620) is consistent selection of this ACE2 pool in a manner that has sustained transmission fitness within the human population. C_FIG

microbiology↗

bioRxiv2020

Rewiring PBMC responses to prevent CHIKV infection-specific monocyte subset redistribution and cytokine responses

Infection with the mosquito-borne Chikungunya virus (CHIKV) causes acute or chronic arthritis in humans. Inflammatory responses mediated by monocytes, the primary target cells of CHIKV infection in the blood, are considered to play an important role in CHIKV pathogenesis. A recent study revealed that the acute phase of CHIKV infection is characterized by a monocyte-driven response, with an expansion of the intermediate monocyte (IM) subset. In this study, we adopted a previously established in vitro model of CHIKV infection in peripheral blood mononuclear cells, to elucidate the mechanism and relevance of IM expansion in CHIKV replication and associated inflammatory responses. Our data show that infectious but not replication-incompetent CHIKV increases the frequency of IM and to a lesser extent, non-classical (NM) monocytes while reducing the number of classical monocytes (CM). The increase of IM or NM frequency coincided with the activation of inflammatory response and occurred in the absence of lymphocytes implying that monocyte-derived cues are sufficient to drive this effect. Importantly, priming of monocytes with LPS prevented expansion of IM and NM but had no effect on viral replication. It did however alter CHIKV-induced cytokine signature. Taken together, our data delineate the role of IM in CHIKV infection-specific innate immune responses and provide insight for the development of therapeutic strategies that may focus on rewiring monocyte immune responses to prevent CHIKV-mediated arthralgia and arthritis.

immunology↗