Balhuizen Melanie D, Versluis Chantal M, van Harten Roel M, de Jonge Eline F, Brouwers Jos F, van de Lest Chris H A, Veldhuizen Edwin J A, Tommassen Jan, Haagsman Henk P
Section of Molecular Host Defence, Division of Infectious Diseases and Immunology, Department of Biomolecular Health Sciences, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 1, 3584 CL, Utrecht, The Netherlands.
Section Molecular Microbiology, Department of Biology, Faculty of Science, Utrecht University, Utrecht, The Netherlands.
Curr Res Microb Sci. 2020 Sep 25;2:100010. doi: 10.1016/j.crmicr.2020.100010. eCollection 2021 Dec.
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 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 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.
宿主防御肽（HDPs），如cathelicidins，是小的阳离子两亲性肽，是先天免疫系统的重要组成部分。大多数cathelicidins，包括猪的PMAP - 36，具有膜活性并破坏细菌膜。例如，先前已表明鸡的cathelicidin CATH - 2既能破坏细胞膜，又能在亚致死浓度下释放外膜囊泡（OMV）。由于OMV被认为是有前景的疫苗候选物，我们试图研究亚杀菌浓度的PMAP - 36对猪源菌株释放OMV以及对OMV免疫反应调节的影响。用PMAP - 36处理细菌导致OMV释放略有增加。将PMAP - 36诱导的OMV的特性与自发释放的OMV和热处理诱导的OMV的特性进行了比较。动态光散射显示，与自发OMV相比，PMAP - 36和热诱导的OMV的稳定性均降低。此外，用PMAP - 36或热处理细菌导致所得OMV中带负电荷的磷脂增加。在热诱导的OMV中观察到溶血磷脂含量大幅增加，这至少部分归因于外膜磷脂酶A（OMPLA）的活性。尽管在从经PMAP - 36处理的细菌中分离出的OMV中检测到了PMAP - 36，但猪骨髓来源的巨噬细胞对这些OMV的免疫反应与对自发或热诱导的OMV的免疫反应相似。因此，研究了OMV分离后添加PMAP - 36的效果。这确实降低了OMV刺激的巨噬细胞的细胞因子表达。这些结果表明，PMAP - 36是一种有前景的分子，可减弱不良免疫反应，例如在疫苗中。
