{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,1,9]],"date-time":"2026-01-09T23:28:45Z","timestamp":1768001325123,"version":"3.49.0"},"reference-count":43,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2023,3,22]],"date-time":"2023-03-22T00:00:00Z","timestamp":1679443200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100010803","name":"Department of Biotechnology, Government of West Bengal","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100010803","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Cell. Infect. Microbiol."],"abstract":"<jats:p>The <jats:italic>Oceanimonas<\/jats:italic> sp. <jats:italic>BPMS22<\/jats:italic>-derived protein protease inhibitor (PPI) has been proven to shift macrophages towards an inflammatory state and reduce <jats:italic>Leishmania donovani<\/jats:italic> infection <jats:italic>in vitro<\/jats:italic> and <jats:italic>in vivo<\/jats:italic>. The current study explored and validated the mechanistic aspects of the PPI and Toll-like receptor (TLR) interaction. The PPI exhibited the upregulation of TLR2, TLR4, and TLR6 during treatment which was proven to orchestrate parasite clearance effectively. An <jats:italic>in silico<\/jats:italic> study confirmed the high interaction with TLR4 and PPI. Immune blotting confirmed the significant upregulation of TLR4 in macrophages irrespective of <jats:italic>L. donovani<\/jats:italic> infection. Pharmacological inhibition and immune blot study confirmed the involvement of the PPI in TLR4-mediated phosphorylation of p38 MAPK and dephosphorylation of ERK1\/2, repolarizing to pro-inflammatory macrophage state against experimental visceral leishmaniasis. In addition, in TLR4 knockdown condition, PPI treatment failed to diminish M2 phenotypical markers (CD68, Fizz1, Ym1, CD206, and MSR-2) and anti-inflammatory cytokines (IL-4, IL-10, and TGF-\u03b2). Simultaneously, the PPI failed to upregulate the M1 phenotypical markers and pro-inflammatory cytokines (IL-1\u03b2, IL-6, IL-12, and IFN-\u03b3) (<jats:italic>p<\/jats:italic> &amp;lt; 0.001) during the TLR4 knockdown condition. In the absence of TLR4, the PPI also failed to reduce the parasite load and T-cell proliferation and impaired the delayed-type hypersensitivity response. The absence of pro-inflammatory cytokines was observed during a co-culture study with PPI-treated macrophages (in the TLR4 knockdown condition) with day 10 T-cell obtained from <jats:italic>L. donovani<\/jats:italic>-infected mice. This study supports the immunotherapeutic potential of the PPI as it interacted with TLR4 and promoted macrophage repolarization (M2\u2013M1) to restrict the <jats:italic>L. donovani<\/jats:italic> parasite burden and helps in the mounting immune response against experimental visceral leishmaniasis.<\/jats:p>","DOI":"10.3389\/fcimb.2023.1120888","type":"journal-article","created":{"date-parts":[[2023,3,22]],"date-time":"2023-03-22T06:07:49Z","timestamp":1679465269000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":2,"title":["Unwinding the mechanism of macrophage repolarization potential of Oceanimonas sp. 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