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Kaushal, J.

Publications and source records attributed to Kaushal, J..

2 recordsLinked to original sources
bioRxiv2026

MAIT cell responses to S. aureus and sensitivity to HlgAB are modulated by activation and tissue-dependent virulence effects

Mucosa-associated invariant T (MAIT) cells are unconventional T cells with innate-like rapid antimicrobial effector functions and serve as resident sentinels at mucosal and non-mucosal barriers. However, their role in immune defense against Staphylococcus aureus and the impact of bacterial immune evasion mechanisms are incompletely understood. Here, we have investigated MAIT cell responses to S. aureus and the impact of its broadly expressed leukocidin toxin HlgAB on MAIT cell responses in different human tissue sites. MAIT cells respond to S. aureus with a complex polyfunctional profile spanning pro-inflammatory IL-17, TNF, and IFN{gamma}, anti-inflammatory IL-10, plus granzymes A, B, and K, perforin, and granulysin. The quality of responses was influenced by microbial dose and time of exposure and was dependent on both MR1-presented antigen and cytokine co-activation. CD56 MAIT cells displayed stronger effector responses and higher HlgAB sensitivity compared to CD56- cells. MAIT cells were partially resistant to HlgAB-toxicity compared to monocytes; blood-derived MAIT cells remained susceptible, whereas tonsillar MAIT cells showed minimal sensitivity. Notably, activation reduced the MAIT cell susceptibility to HlgAB, and such activation also afforded indirect protection to monocytes in co-cultures. The reduced susceptibility of tonsillar MAIT cells correlated with lower CCR2 and CXCR1 expression, a pattern shared with barrier tissues such as the lung and intestines. In conclusion, these findings indicate that MAIT cells exhibit tissue- and context-dependent responses to S. aureus and sensitivity to HlgAB-mediated immune evasion. ImportanceMAIT cells are an evolutionarily conserved unconventional T cell subset that responds to riboflavin pathway-derived antigens from a range of microbes. Here, we found that the human MAIT cell response to the pathogen S. aureus is robust with a polyfunctional complexity influenced by bacterial concentration and response kinetics. The ubiquitously expressed S. aureus immune-evasive toxin HlgAB attacks MAIT cells via CCR2. However, the sensitivity of MAIT cells to HlgAB varies depending on tissue localization, where in particular tissue-resident MAIT cells in tonsils are resistant. Antigen-specific activation of MAIT cells reduces HlgAB sensitivity, with protection also afforded to monocytes in the vicinity. These findings uncover the complex and dynamic interaction between an evolutionarily conserved arm of immunity, and immune evasion mechanisms of the important pathogen S. aureus.

immunology↗
bioRxiv2022

MiR-1253 Potentiates Cisplatin Response in Pediatric Group 3 Medulloblastoma by Regulating Ferroptosis

Medulloblastomas (MB) are the most common malignant pediatric brain tumor and a leading cause of childhood mortality. Aggressive tumors belonging to group 3 (G3MB) are distinguished by a marked reduction in programmed cell death by ferroptosis. These aggressive tumors also enrich iron transport and glutathione metabolism. A highly enriched pathway in these tumors is iron-sulfur (Fe-S) cluster binding corresponding to significant upregulation of ABCB7, a poor prognostic feature linked with accelerated mortality. This study elucidated whether repressing ABCB7 activates ferroptosis to mitigate G3MB aggressiveness and whether this pathway is pharmacologically targetable. In silico and in vitro analyses confirmed upregulation of ABCB7 and GPX4, the central regulator of ferroptosis, in G3MB cell lines and tumors. Repressing ABCB7 (miR-1253OE, siABCB7, sh-ABCB7) induced iron overload, elicited oxidative stress, and triggered lipid peroxidation, leading to an abrogation of medullosphere formation and cell death by ferroptosis. Intriguingly, fractionation studies revealed that ABCB7 repression abrogated GPX4 expression, most likely by GSH depletion. Repressing ABCB7 induced mitochondrial dysfunction and reduced oxidative phosphorylation. Cisplatin, a chemotherapeutic mainstay of G3MB, induces cell death by DNA crosslinking. In ABCB7 repressed cell lines, the IC50 of cisplatin was halved, resulting in augmented oxidative stress and lipid peroxidation, culminating in a higher index of ferroptosis. Artesunate, an anti-malarial drug capable of triggering ferroptosis, was shown to synergize with cisplatin, reducing tumor burden and significantly prolonging survival. Taken together, the current study illustrates how targeting iron transport can augment ferroptosis in G3MBs. It further identifies an FDA-approved drug capable of recapitulating these effects and potentiating mainstay chemotherapy.

cancer biology↗