Krey, K. | Search bioRxiv

bioRxiv2026

A chimeric, half-life extended lysin with a unique mode of action

Anti-staphylococcal lytic agents, such as lysostaphin (LSN), a glycyl-glycyl (Gly-Gly) peptidase, have long been considered for the management of chronic and complicated bacterial infections typically resistant to conventional antibiotics, but their use is restricted by poor pharmacokinetic properties. We generated half-life extended lysostaphin constructs by fusing the lysin - either alone or chimerized with an additional enzymatic cysteine, histidine-dependent amidohydrolases/peptidase (CHAP) domain - to the human IgG1 Fc fragment. The Fc-CHAP-LSN constructs retain high potency against Staphylococcus aureus and coagulase negative staphylococcal strains in vitro and are efficacious in S. aureus ex vivo biofilm models and in vivo sepsis models. A detailed investigation of the Fc-CHAP-LSN mode of action revealed that upon binding to the bacterial cell, but not in solution, LSN mediates its own release by cleaving the Gly-Gly CHAP-LSN linker. The bactericidal activity of Fc-CHAP-LSN is driven by the LSN-catalyzed and target cell-dependent release of free LSN. The half-life extended lysin acts as a pro-drug, unveiling a novel mechanism of targeted release and an alternative approach to half-life extension.

bioengineering↗

bioRxiv2020

FOXO1 promotes HIV Latency by suppressing ER stress in T cells

Quiescence is a hallmark of CD4+ T cells latently infected with HIV-1. While reversing this quiescence is an effective approach to reactivate latent HIV from T cells in culture, it can cause deleterious cytokine dysregulation in patients. Here we report that FOXO1, a key regulator of T-cell quiescence, promotes latency and suppresses productive HIV infection. In resting T cells, FOXO1 inhibition induces ER stress and activates two associated transcription factors: activating transcription factor 4 (ATF4) and nuclear factor of activated T cells (NFAT). Both factors associate with HIV chromatin and are necessary for HIV reactivation. Indeed, inhibition of PKR-like endoplasmic reticulum kinase (PERK), a known link between ER stress and ATF4, and calcineurin, a calcium-dependent regulator of NFAT, synergistically suppress HIV reactivation induced by FOXO1 inhibition. Thus, our studies uncover a novel link between FOXO1, ER stress, and HIV infection that could be therapeutically exploited to selectively reverse T-cell quiescence and reduce the size of the latent viral reservoir.

immunology↗