Biology subjects

Szczerba, M.

Publications and source records attributed to Szczerba, M..

3 recordsLinked to original sources

bioRxiv2026

Dual NLRC4 and non-canonical inflammasome signaling drives human GSDMD-mediated killing of Shigella flexneri independently of bacterial cardiolipin.

Macrophages internalize and kill bacteria and thus are crucial for clearing bacterial infections. Although macrophage killing of some intracellular bacteria requires inflammasomes, the specific mechanisms of inflammasome-dependent killing are incompletely understood. Here we show that, upon infection with an intracellular pathogen Shigella flexneri, human macrophages activate a robust NLRC4-caspase-1 inflammasome response that restricts intracellular bacterial replication independently of pyroptosis. Gasdermin D (GSDMD) cleavage is required for bactericidal activity, revealing a GSDMD-dependent mechanism of bacterial killing independent of host cell death. We find that GSDMD-mediated killing of S. flexneri does not require bacterial cardiolipin, identifying a cardiolipin-independent mode of bacterial targeting. Priming macrophages with interferon (IFN)-{gamma} enhances killing of intracellular S. flexneri by promoting involvement of caspase-4, which cooperates with caspase-1 to potentiate GSDMD function. These results identify a dual engagement of canonical and non-canonical inflammasomes that leads to macrophage killing S. flexneri while preserving host cell integrity. Furthermore, these findings uncover a previously unrecognized cardiolipin-independent mechanism of GSDMD-mediated bacterial killing with broad implications for immune cell control of cytosolic bacterial pathogens.

immunology↗

bioRxiv2024

NLRP11 is required for canonical NLRP3 and non-canonical inflammasome activation during human macrophage infection with mycobacteria

The NLRP11 protein is only expressed in primates and participates in the activation of the canonical NLRP3 and non-canonical NLRP3 inflammasome activation after infection with gram-negative bacteria. Here, we generated a series of defined NLRP11 deletion mutants to further analyze the role of NLRP11 in NLRP3 inflammasome activation. Like the complete NLRP11 deletion mutant (NLRP11-/-), the NLRP11 mutant lacking the NACHT and LRR domains (NLRP11{Delta}N_LRR) showed reduced activation of the canonical NLRP3 inflammasome, whereas a pyrin domain mutant (NLRP11{Delta}PYD) had no effect on NLRP3 activation. The NLRP11-/- and NLRP11{Delta}N_LRR mutants but not the NLRP11{Delta}PYD mutant also displayed reduced activation of caspase-4 during infection with the intracytosolic, gram-negative pathogen Shigella flexneri. We found that the human adapted, acid-fast pathogen Mycobacterium tuberculosis and the opportunistic pathogen M. kansasii both activate the non-canonical NLRP11 inflammasome in a caspase-4/5-dependent pathway. In conclusion, we show that NLRP11 functions in the non-canonical caspase-4/5 inflammasome activation pathway and the canonical NRLP3 inflammasome pathway, and that NLRP11 is required for full recognition of mycobacteria by each of these pathways. Our work extends the spectrum of bacterial pathogen recognition by the non-canonical NLRP11-caspase4/5 pathway beyond gram-negative bacteria. IMPORTANCEThe activation of inflammasome complexes plays a crucial role in intracellular pathogen detection. NLRP11 and caspase-4 are essential for recognizing lipopolysaccharide (LPS), a molecule found in gram-negative bacteria such as the human pathogens Shigella spp., which activate both canonical NLRP3 and non-canonical inflammasome pathways. Through a series of deletion mutants, we demonstrate that the NACHT and LRR domains of NLRP11, but not its pyrin domain, are critical for detection of S. flexneri. Notably, our research reveals that the acid-fast bacterium M. tuberculosis is also detected by NLRP11 and caspase-4, despite not producing LPS. These findings significantly expand the range of pathogens recognized by NLRP11 and caspase-4 to now include acid - fast bacteria that do not contain LPS and underscore the versatility of these innate immune components in pathogen detection.

immunology↗

bioRxiv2021

Intranasal immunization with a vaccinia virus vaccine vector expressing pre-fusion stabilized SARS-CoV-2 spike fully protected mice against lethal challenge with the heavily mutated mouse-adapted SARS2-N501YMA30 strain of SARS-CoV-2

The Omicron SARS-CoV-2 variant has been designated a variant of concern because its spike protein is heavily mutated. In particular, Omicron spike is mutated at 5 positions (K417, N440, E484, Q493 and N501) that have been associated with escape from neutralizing antibodies induced by either infection with or immunization against the early Washington strain of SARS-CoV-2. The mouse-adapted strain of SARS-CoV-2, SARS2-N501YMA30, contains a spike that is also heavily mutated, with mutations at 4 of the 5 positions in Omicron spike associated with neutralizing antibody escape (K417, E484, Q493 and N501). In this manuscript we show that intranasal immunization with a pre-fusion stabilized Washington strain spike, expressed from a highly attenuated, replication-competent vaccinia virus construct, NYVAC-KC, fully protected mice against disease and death from SARS2-N501YMA30. Similarly, immunization by scarification on the skin fully protected against death, but not from mild disease. This data demonstrates that Washington strain spike, when expressed from a highly attenuated, replication-competent poxvirus, administered without parenteral injection can fully protect against the heavily mutated mouse-adapted SARS2-N501YMA30.

microbiology↗