ORIGINAL RESEARCH article
Front. Cell. Infect. Microbiol.
Sec. Oral Microbes and Host
Filifactor alocis FtxA blocks inflammation and apoptosis pathways in monocytic cells
Zeinab Razooqi 1
Kai Bao 2
Abdelbasset Yabrag 1
Raviprakash T. Sitaram 1
Mark Lindholm 2
Mattias Pettersson 1
Anders Johansson 1
Georgios N. Belibasakis 2
Aftab Nadeem 1
Jan Oscarsson 1
1. Umeå University, Umeå, Sweden
2. Karolinska Institutet, Stockholm, Sweden
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Abstract
Filifactor alocis is an emerging oral pathogen, and approximately 50% of known F. alocis strains encode and express a Repeats-in-Toxin (RTX) protein, FtxA. Ftx appears to be associated with both progress and severity of periodontal disease. Mechanism(s) are not yet known but could be linked to increased loads of F. alocis in ftxA-positive strains. Here, we investigated mechanistic correlations based on FtxA-activity, as present in F. alocis cells, extracellular vesicles, and as a recombinant protein, exploiting THP-1 macrophage-like cells. For this, we used the ftxA-expressing strain, ATCC 35896 (ftxA+), and F. alocis 148B-17U (ftxA-), which naturally lacks the ftxA gene. Using RNA sequencing analysis (RNA-Seq) and cytokine array analysis we have pinpointed a role of FtxA in shifting host response towards immunosuppression, also inhibiting apoptosis, immune cell recruitment, and with a potential role in downregulating mitochondrial and oxidative phosphorylation pathways. Such role(s) could provide a plausible explanation why FtxA is associated with progress and severity of periodontal disease, and further studies on FtxA-host cell interactions might reveal novel potential therapeutic targets.
Summary
Keywords
Apoptosis, extracellular vesicles, Filifactor alocis, FtxA, Inflammation, Periodontitis, RTX toxin, THP-1 cells
Received
13 November 2025
Accepted
20 February 2026
Copyright
© 2026 Razooqi, Bao, Yabrag, Sitaram, Lindholm, Pettersson, Johansson, Belibasakis, Nadeem and Oscarsson. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Jan Oscarsson
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