Propionibacterium acnes induces an adjuvant effect in B-1 cells and affects their phagocyte differentiation via a TLR2-mediated mechanism

The Forgotten Brother: The Innate-like B1 Cell in Multiple Sclerosis

Multiple sclerosis (MS) is a neurodegenerative disease of the central nervous system (CNS), traditionally considered a chronic autoimmune attack against the insulating myelin sheaths around axons. However, the exact etiology has not been identified and is likely multi-factorial. Recently, evidence has been accumulating that implies that autoimmune processes underlying MS may, in fact, be triggered by pathological processes initiated within the CNS. This review focuses on a relatively unexplored immune cell-the "innate-like" B1 lymphocyte. The B1 cell is a primary-natural-antibody- and anti-inflammatory-cytokine-producing cell present in the healthy brain. It has been recently shown that its frequency and function may differ between MS patients and healthy controls, but its exact involvement in the MS pathogenic process remains obscure. In this review, we propose that this enigmatic cell may play a more prominent role in MS pathology than ever imagined. We aim to shed light on the human B1 cell in health and disease, and how dysregulation in its delicate homeostatic role could impact MS. Furthermore, novel therapeutic avenues to restore B1 cells' beneficial functions will be proposed.

Toll-like receptors 2 expression in mediastinal lymph node of patients with sarcoidosis

Background

Toll-like receptors (TLRs) play a vital role as a first defense mechanism linking the innate with the adaptive immune system. Prior studies showed that TLR2 participated in immune responses of sarcoidosis. However, the role of TLR2 in the progression of mediastinal lymph nodes associated with sarcoidosis is still unknown. The current study aims to investigate the expression of Toll-like receptors 2 (TLR2) in mediastinal lymph nodes of patients with sarcoidosis.

Methods

Mediastinal lymph nodes biopsy specimens were collected from 10 patients with sarcoidosis and 11 normal controls. The expression of TLR2 in mediastinal lymph nodes was detected by immunohistochemistry.

Results

In mediastinal lymph nodes specimens, immunohistochemical examination revealed that expression of TLR2 could be detected in sarcoidosis patients, while it was scarcely detected in the mediastinal lymph nodes of control. The mean optical density of TLR2 in mediastinal lymph nodes of sarcoidosis was significantly higher than controls (124.9±24.3 vs. 92.6±35.2, P=0.026). Among patients with sarcoidosis, correlation analysis showed that the mean optical density of TLR2 in mediastinal lymph nodes positively correlated with the level of 24-hour urinary calcium (R=0.781, P=0.038).

Conclusions

The expression of TLR2 was upregulated in mediastinal lymph nodes of sarcoidosis patients. The expression of TLR2 in mediastinal lymph nodes was associated with the level of 24-hour urinary calcium, suggesting that TLR2 might become another predictor of disease activity.

Leishmania amazonensis Promastigotes or Extracellular Vesicles Modulate B-1 Cell Activation and Differentiation

B-1 cells are considered an innate-like B cell population that participates in effective innate and adaptive responses to pathogens. B-1 cells produce immunoglobulins, cytokines, chemokines, migrate to inflammatory sites, and differentiate into mononuclear phagocyte-like cells. Murine B-1 cells phagocytosed Leishmaniain vitro and in vivo and participate in immunity against Leishmania. Our group showed that B-1 cells or their extracellular vesicles (EVs) led to a resistance to experimental infection by L. amazonensis. However, the B-1 cells’ responses to Leishmania or EVs isolated from parasites are still poorly characterized. Studying the activation and differentiation of B-1 cells in vivo can contribute to a better understanding of how these cells participate in immunity to L. amazonensis. Thus, we evaluated the expression of myeloid (M-csfr, G-csfr, Spi-1) and lymphoid (EBF, E2A, IL-7R) lineage commitment factors, Toll-like receptors (TLRs), activation cell surface markers, nitric oxide (NO) and reactive oxygen species (ROS) production in murine peritoneal B-1 cells collected after 24 or 48 h post-infection with Leishmania (Leishmania) amazonensis promastigotes or EVs released by the parasites. Our results demonstrated that L. amazonensis infection did not stimulate the expression of CD40, CD80, CD86, F4/80, and MHC II in B-1 cells, but a significant decrease in the production of NO and ROS was observed. The infection induced a significantly higher arginase expression in B-1 cells, but the stimulation with EVs led to a decrease in this gene expression. TLR-2 and TLR-6 had significantly higher expression in B-1 cells from mice intraperitoneally stimulated with the parasite. The TLR-9 expression was higher in animals infected or stimulated for 48 h with EVs. Interestingly, in B-1 cells the stimulus with L. amazonensis led to a substantial increase in the expression of myeloid restricted transcription factors. Thus, our study suggests that the parasites or EVs differently modulated the activation and differentiation of B-1 cells.

The long-standing history of Corynebacterium parvum, immunity, and viruses

We report a review of all the experimental and clinical studies performed in the last 60 years on the antiviral activity of inactivated Corynebacterium parvum (Cutibacterium acnes). This bacterium has been originally investigated and used for its oncolytic properties linked to immunomodulating activity, but the interest to successfully prevent and treat bacterial, fungal, and viral infections and lethality, uprising the innate immunity barriers produced many experimental models and very few clinical studies. The dramatic defenseless situation due to impending CoViD‐19 pandemic claims to exhume and highlight this aspecific strategy in preventive and therapeutic settings; as a matter of fact, no new or mutated virus can potentially escape to this strong innate immune surveillance strengthened by adequate C. parvum protocols.

B-1 Cells May Drive Macrophages Susceptibility to Trypanosoma cruzi Infection

B-1 cells can directly and indirectly influence the immune response. These cells are known to be excellent producers of natural antibodies and can secrete a variety of immunomodulatory molecules. They are also able to differentiate into B-1 cell-derived phagocytes (B-1CDP). B-1 cells can modulate macrophages to become less effective, and B-1CDP cells are more susceptible in infection models. In this work, we investigated the microbicidal ability of these cells in Trypanosoma cruzi infection in vitro. The results show that macrophages from BALB/c mice are more susceptible to infection than macrophages from XID mice. The resistance observed in macrophages from XID mice was abolished in the presence of B-1 cells, and this event seems to be associated with IL-10 production by B-1 cells, which may have contributed to the decrease of NO production. Additionally, B-1CDP cells were more permissive to intracellular T. cruzi infection than peritoneal macrophages. These findings strongly suggest that B-1 cells and B-1CDP cells have a potential role in the persistence of the parasite in host cells.

Assessment of seven protocols to prepare Cutibacterium acnes bacterial lysates to measure its immunogenic potential and review of the literature

Seven protocols were tested to prepare cell wall extracts from live Cutibacterium acnes. Different parameters were modified: thawing/freezing and sonication/freezing cycles, to impact on mechanical degradation of the bacteria. Finally, the immunogenic potential of the extracts generated was evaluated by measuring IL-8 releases using an in vitro skin explants system. The aim of this article was to compare the existing protocols from the scientific literature, and also propose a standardized method developed in our facilities.

B-1 cell response in immunity against parasites

The peritoneal cavity has a microenvironment capable of promoting proliferation, differentiation, and activation of the resident cells and recruitment of blood cells through the capillary network involved in the peritoneum. Among the cells found in the peritoneal cavity, B-1 cells are a particular cell type that contains features that are not very well defined. These cells differ from conventional B lymphocytes (B-2) by phenotypic, functional, and molecular characteristics. B-1 cells can produce natural antibodies, migrate to the inflammatory focus, and have the ability to phagocytose pathogens. However, the role of B-1 cells in immunity against parasites is still not completely understood. Several experimental models have demonstrated that B-1 cells can affect the susceptibility or resistance to parasite infections depending on the model and species. Here, we review the literature to provide information on the peculiarities of B-1 lymphocytes as well as their interaction with parasites.

Improvement of Mesenchymal Stem Cell Immunomodulatory Properties by Heat-Killed Propionibacterium acnes via TLR2

Mesenchymal stem cells (MSCs) are an essential tool for regenerative medicine, which aims to develop new technologies to improve their effects to obtain useful transplantation results. MSC immunomodulatory role has been just demonstrated; however, how they react when they are stimulated by an adjuvant is poorly understood. Our group showed the adjuvant effect of killed Propionibacterium acnes (P. acnes) on hematopoietic stem cells. As these cells share the same MSCs bone marrow (BM) site and interact with each other, here we evaluated the P. acnes and its soluble polysaccharide (PS) effect on MSCs and their immunomodulatory role in a murine model of traumatic brain injury (TBI). The bacteria increased the absolute number of MSCs, including MSC subpopulations, and maintained MSC plasticity. P. acnes and PS enhanced MSC proliferation and improved their immunomodulatory effect. P. acnes-MSC and PS-MSC transplantation increased anti-inflammatory cytokine expression and diminished pro-inflammatory cytokine expression after injury. This effect seemed to be mediated via TLR2 since P. acnes-KOTLR2-MSC transplantation decreased TGF-β and IL-10 expression. Increasing in neural stem cells and neuroblasts after PS-MSC transplantation was also observed. The adjuvant effect of P. acnes is an alternative means of expanding MSCs and important to identify their subpopulations to know better their role under exogenous stimuli including inflammation resolution in an experimental model.

Killed Propionibacterium acnes enhances immunogenicity and tumor growth control of a dendritic-tumor cell hybrid vaccine in a murine melanoma model

Hybrid vaccines have been investigated in clinical and experimental studies once expresses total antigens of a tumor cell combined with the ability of a dendritic cell (DC) to stimulate immune responses. However, the response triggered by these vaccines is often weak, requiring the use of adjuvants to increase vaccine immunogenicity. Killed Propionibacterium acnes (P. acnes) exerts immunomodulatory effects by increasing the phagocytic and tumoricidal activities of macrophages, promoting DC maturation, inducing pro-inflammatory cytokines production and increasing the humoral response to different antigens. Here, we evaluated the effect of P. acnes on a specific antitumor immune response elicited by a hybrid vaccine in a mouse melanoma model. Hybrid vaccine associated with P. acnes increased the absolute number of memory T cells, the IFN-γ secretion by these cells and the IgG-specific titers to B16F10 antigens, polarizing the immune response to a T helper 1 pattern. Furthermore, the addition of P. acnes to a hybrid vaccine increased the cytotoxic activity of splenocytes toward B16F10 in vitro and avoided late tumor progression in a pulmonary colonization model. These results revealed the adjuvant effect of a killed P. acnes suspension, as it improved specific humoral and cellular immune responses elicited by DC-tumor cell hybrid vaccines.

The therapeutic effect of tanshinone IIA on Propionibacterium acnes-induced inflammation in vitro

Acne vulgaris, a chronic inflammatory skin disease, affects many adolescents. New therapeutic agents for acne allow for a higher therapeutic activity, but fewer side effects. Tanshinone IIA, a natural product, has been proved to exhibit antibacterial and anti-inflammatory abilities in many diseases. However, its antibacterial and anti-inflammatory activities against Propionibacterium acnes have not been described. In the present study, the broth microdilution method was used to evaluate the antibacterial activity of tanshinone IIA and it had an inhibitory effect on the growth of P. acnes. Enzyme-linked immunosorbent assay and quantitative real-time PCR were used to investigate the effect of tanshinone IIA on IL-1β, IL-8, and TNF-α expression, and western blot was used to examine TLR2, NF-κB, and intercellular cell adhesion molecule-1 (ICAM-1) protein level induced by P. acnes in THP-1 cells. Results showed that the expression of inflammatory cytokines and TLR2, NF-κB, ICAM-1 protein levels were inhibited by Tanshinone IIA, suggesting that tanshinone IIA appeared to suppress P. acnes-induced inflammation by blockade of TLR2/NF-κB signaling pathway. In conclusion, the present study revealed the inhibitory effect of tanshinone IIA on P. acnes-induced inflammation, providing an evidence to support the mechanism of anti-acne properties of tanshinone IIA.

Comparative Effects of Schisandrin A, B, and C on Acne-Related Inflammation

Inflammatory responses induced by Propionibacterium acnes are a major etiological factor in the pathogenesis of acne vulgaris. Schisandrin A, schisandrin B, and schisandrin C are the representative lignans of Schisandra chinensis (Turcz.) Baill. extract. Although anti-inflammatory effects of the lignans have been shown, their effects on acne-related inflammation caused by P. acnes have not been investigated and compared. We pretreated THP-1 human monocytic cells with 5, 10, and 20 μM schisandrin A, B, and C, and stimulated the cells with P. acnes. Schisandrin B and C inhibited the release of inflammatory cytokines at a concentration of 5 μM, while schisandrin A required a concentration of 10 μM to exert the effects. All of the schisandrins decreased the levels of toll-like receptor 2, and schisandrin B and C reduced the intracellular mRNA expression of the receptor gene. We also studied the influence of schisandrins on the MAPK signaling pathway. Schisandrin A suppressed the P. acnes-induced activation of JNK, while exerting only a weak effect on ERK and p38. Schisandrin B exerted a strong effect on p38, a lesser effect on ERK, and almost no effect on JNK. Schisandrin C inhibited the phosphorylation of all three proteins, especially ERK. Furthermore, the three lignans also prevented the nuclear translocation of NF-κB. These results contribute to our understanding of the mechanisms underlying the effects of the three lignans on P. acnes-induced inflammation and suggest that schisandrins might be developed as pharmacological agents for acne therapy.

Intranasal administration of inactivated avian influenza virus of H5N1 subtype vaccine-induced systemic immune response in chicken and mice

Aim

The need for non-parenteral administration of inactivated avian influenza virus of H5N1 subtype (AIV-H5N1) vaccine is paramount. Here, we provide preliminary data on the immune response of chicken and mice after intranasal administration of AIV-H5N1-inactivated vaccine with ISCOMS, Inmunair (INM), and combined ISCOMS and INM as an adjuvant.

Materials and Methods

The AIV isolate of A/Chicken/Denpasar/01/2004 (H5N1) was cultivated in specific pathogen-free chicken eggs and inactivated with formaldehyde. The vaccine preparation was added with those adjuvants for intranasal administration and aluminum hydroxide for subcutaneous injection. The chicken and mouse were vaccinated at the age of 3 weeks or 1 month and repeated 2 weeks thereafter. In one experiment, chicken was injected with Newcastle disease virus (NDV) at the same time with AIV vaccine. The sera were collected at one (serum 1) and 2 w (serum 2) after booster vaccination. The anti-AIV-H5 and NDV antibodies in chicken sera were detected using hemagglutination inhibition (HI) assay. Mouse IgG anti-AIV-H5N1 antibody was detected using ELISA.

Results

The result shows that the geometric mean titers (GMTs) of chicken sera of intranasal vaccinated with inactivated AIV-H5N1 vaccine with mixed ISCOM- INM as adjuvant were <2^0.0 and 2^2.7 unit HI-unit (HIU) in serum 1 and serum 2, respectively. The GMTs of the positive control group were 2^3.7 and 2^5.7 HIU in serum 1 and serum 2, respectively. The result of the second experiment shows that IgG anti-AIV-H5N1 was detected in mouse sera. In the third experiment, the GMTs of anti-NDV in chicken vaccinated subsequently with inactivated NDV vaccine and AIV-H5N1 with mixed ISCOMS-INM administrated intranasally and aluminum hydroxide adjuvant administrated through subcutaneous injection as well as positive control group receiving NDV vaccine only were 2^8.0, 2^8.0, and 2^7.4 HIU in serum 1 while were 2^9.6, 2^9.2, and 2^8.2 HIU in serum 2, respectively.

Conclusion

Intranasal administration of inactivated AIV-H5N1 vaccine-induced a systemic immune response in chicken and mice after adding ISCOMS and/or INM as adjuvants. The adjuvant and the intranasal administration caused no immunosuppressive effect on the chicken immune response to NDV vaccine.

Propionibacterium acnes Enhances the Immunogenicity of HIVBr18 Human Immunodeficiency Virus-1 Vaccine

Immunization of BALB/c mice with HIVBr18, a DNA vaccine containing 18 CD4⁺ T cell epitopes from human immunodeficiency virus (HIV), induced specific CD4⁺ and CD8⁺ T cell responses in a broad, polyfunctional and persistent manner. With the aim of increasing the immunogenicity of this vaccine, the effect of Propionibacterium acnes as an adjuvant was evaluated. The adjuvant effects of this bacterium have been extensively demonstrated in both experimental and clinical settings. Herein, administration of two doses of HIVBr18, in the presence of P. acnes, increased the proliferation of HIV-1-specific CD4⁺ and CD8⁺ T lymphocytes, the polyfunctional profile of CD4⁺ T cells, the production of IFN-γ, and the number of recognized vaccine-encoded peptides. One of the bacterial components responsible for most of the adjuvant effects observed was a soluble polysaccharide extracted from the P. acnes cell wall. Furthermore, within 10 weeks after immunization, the proliferation of specific T cells and production of IFN-γ were maintained when the whole bacterium was administered, demonstrating a greater effect on the longevity of the immune response by P. acnes. Even with fewer immunization doses, P. acnes was found to be a potent adjuvant capable of potentiating the effects of the HIVBr18 vaccine. Therefore, P. acnes may be a potential adjuvant to aid this vaccine in inducing immunity or for therapeutic use.

An anti-Propionibacterium acnes antibody shows heterologous resistance to an Actinobacillus pleuropneumoniae infection independent of neutrophils in mice

Porcine contagious pleuropneumonia is a highly fatal respiratory disease that is caused by Actinobacillus pleuropneumoniae (APP) and results in tremendous economic losses for the pig breeding industry worldwide. Previous studies have demonstrated that Propionibacterium acnes (PA) could effectively prevent APP infection in mice and pigs. The humoral immune response played a primary role during this process and anti-PA antibody could mediate macrophages to kill the bacteria. However, the role of neutrophils in this process is currently unknown. In this study, mice were injected with cyclophosphamide to deplete neutrophils and then passively immunized with anti-PA serum or negative serum. Mice were subsequently challenged with APP serotype 1. The results showed that the mice exhibited less bacterial colonization, less lung damage, and a high survival rate, which were immunized with the anti-PA antibody whether neutrophils were depleted or not. Worse still, the presence of neutrophils increased the damage to the mice after challenge. These results suggest that the activity of the anti-PA antibody against APP infection was independent of neutrophils. These findings have important significance for understanding the mechanisms of humoral immunity conferred by heterologous immunization and lay a good foundation for preventing APP infection.

B-1 cells modulate the murine macrophage response to Leishmania major infection

AIM

To investigate the modulatory effect of B-1 cells on murine peritoneal macrophages infected with Leishmania major (L. major) in vitro.

METHODS

Peritoneal macrophages obtained from BALB/c and BALB/c XID mice were infected with L. major and cultured in the presence or absence of B-1 cells obtained from wild-type BALB/c mice. Intracellular amastigotes were counted, and interleukin-10 (IL-10) production was quantified in the cellular supernatants using an enzyme-linked immunosorbent assay. The levels of the lipid mediator prostaglandin E2 (PGE₂) were determined using a PGE₂ enzyme immunoassay kit (Cayman Chemical, Ann Arbor, MI), and the number of lipid bodies was quantified in the cytoplasm of infected macrophages in the presence and absence of B-1 cells. Culturing the cells with selective PGE₂-neutralizing drugs inhibited PGE₂ production and confirmed the role of this lipid mediator in IL-10 production. In contrast, we demonstrated that B-1 cells derived from IL-10 KO mice did not favor the intracellular growth of L. major.

RESULTS

We report that B-1 cells promote the growth of L. major amastigotes inside peritoneal murine macrophages. We demonstrated that the modulatory effect was independent of physical contact between the cells, suggesting that soluble factor(s) were released into the cultures. We demonstrated in our co-culture system that B-1 cells trigger IL-10 production by L. major-infected macrophages. Furthermore, the increased secretion of IL-10 was attributed to the presence of the lipid mediator PGE₂ in supernatants of L. major-infected macrophages. The presence of B-1 cells also favors the production of lipid bodies by infected macrophages. In contrast, we failed to obtain the same effect on parasite replication inside L. major-infected macrophages when the B-1 cells were isolated from IL-10 knockout mice.

CONCLUSION

Our results show that elevated levels of PGE₂ and IL-10 produced by B-1 cells increase L. major growth, as indicated by the number of parasites in cell cultures.

B cell cross-epitope of Propionibacterium acnes and Actinobacillus pleuropneumonia selected by phage display library can efficiently protect from Actinobacillus pleuropneumonia infection

Contagious porcine pleuropneumonia (CPP), caused by Actinobacillus pleuropneumoniae (APP), is a highly transmissible and fatal respiratory illness that causes tremendous economic losses for the pig breeding industry worldwide. Propionibacterium acnes (PA) has a strong cross-reaction with anti-APP1 and anti-APP5 serum and can efficiently prevent APP infection, which was fortuitously found in researching the differential gene between the different APP serotypes. There seems to be some natural cross-protection between PA and APP. To identify the common epitope, the phage display library of a PA whole genome was constructed, whose size is 10⁵. The DNA sequence of the positive clone was determined after three rounds of biopanning, and ten common protein types were identified and the epitope was predicted by computer software. Six peptide epitopes were selected and synthesized for further analysis. Among these epitopes, Ba1, Bb5 and C1 could bind to anti-PA serum and anti-APP1 serum and vice versa. Furthermore, the IgG and IL-4 levels and CD4⁺/CD8⁺ T cell ratios in the Ba1, Bb5 and C1 groups were significantly higher than that in the control group, indicating that the epitopes could trigger an immune response, which was mainly humoral immunity. Moreover, Ba1 and Bb5 equally protected 80% of mice from a fatal dose of APP1 infection compared with the control group. Mice could resist APP1 and APP5 challenge after being treated with the combination of Ba1 and Bb5, with survival rates of 80% and 90%, respectively. These findings suggest that the PA epitope confers antigenicity and can heterologously resist to the APP infection. This finding provides a novel strategy for preventing APP infection.