Balhuizen MD, Versluis CM, van Harten RM, de Jonge EF, Brouwers JF, van de Lest CH, Veldhuizen EJ, Tommassen J, Haagsman HP. PMAP-36 reduces the innate immune response induced by Bordetella bronchiseptica-derived outer membrane vesicles.
CURRENT RESEARCH IN MICROBIAL SCIENCES 2021;
2:100010. [PMID:
34841304 PMCID:
PMC8610334 DOI:
10.1016/j.crmicr.2020.100010]
[Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 09/08/2020] [Accepted: 09/08/2020] [Indexed: 12/16/2022] Open
Abstract
Sub-lethal PMAP-36 treatment of bacteria increases outer membrane vesicle release.
Lipidomic analysis revealed the OMV lipidome upon PMAP-36 or heat treatment.
Supplementation with PMAP-36 attenuated undesirable OMV-induced immune responses.
Host defense peptides (HDPs), such as cathelicidins, are small, cationic, amphipathic peptides and represent an important part of the innate immune system. Most cathelicidins, including the porcine PMAP-36, are membrane active and disrupt the bacterial membrane. For example, a chicken cathelicidin, CATH-2, has been previously shown to disrupt both Escherichia coli membranes and to release, at sub-lethal concentrations, outer membrane vesicles (OMVs). Since OMVs are considered promising vaccine candidates, we sought to investigate the effect of sub-bactericidal concentrations of PMAP-36 on both OMV release by a porcine strain of Bordetella bronchiseptica and on the modulation of immune responses to OMVs. PMAP-36 treatment of bacteria resulted in a slight increase in OMV release. The characteristics of PMAP-36-induced OMVs were compared with those of spontaneously released OMVs and OMVs induced by heat treatment. The stability of both PMAP-36- and heat-induced OMVs was decreased compared to spontaneous OMVs, as shown by dynamic light scattering. Furthermore, treatment of bacteria with PMAP-36 or heat resulted in an increase in negatively charged phospholipids in the resulting OMVs. A large increase in lysophospholipid content was observed in heat-induced OMVs, which was at least partially due to the activity of the outer-membrane phospholipase A (OMPLA). Although PMAP-36 was detected in OMVs isolated from PMAP-36-treated bacteria, the immune response of porcine bone-marrow-derived macrophages to these OMVs was similar as those against spontaneous or heat-induced OMVs. Therefore, the effect of PMAP-36 addition after OMV isolation was investigated. This did decrease cytokine expression of OMV-stimulated macrophages. These results indicate that PMAP-36 is a promising molecule to attenuate undesirable immune responses, for instance in vaccines.
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