Human monoclonal antibody inhibits Porphyromonas gingivalis hemagglutinin activity

Future Drug Targets in Periodontal Personalised Medicine-A Narrative Review

Periodontal disease is an infection-driven inflammatory disease characterized by the destruction of tooth-supporting tissues. The establishment of chronic inflammation will result in progressive destruction of bone and soft tissue changes. Severe periodontitis can lead to tooth loss. The disease has complex pathogenesis with an interplay between genetic, environmental, and host factors and pathogens. Effective management consists of plaque control and non-surgical interventions, along with adjuvant strategies to control inflammation and disrupt the pathogenic subgingival biofilms. Recent studies have examined novel approaches for managing periodontal diseases such as modulating microbial signaling mechanisms, tissue engineering, and molecular targeting of host inflammatory substances. Mounting evidence suggests the need to integrate omics-based approaches with traditional therapy to address the disease. This article discusses the various evolving and future drug targets, including proteomics, gene therapeutics, vaccines, and nanotechnology in personalized periodontal medicine for the effective management of periodontal diseases.

Quercetin inhibits virulence properties of Porphyromas gingivalis in periodontal disease

Porphyromonas gingivalis is a causative agent in the onset and progression of periodontal disease. This study aims to investigate the effects of quercetin, a natural plant product, on P. gingivalis virulence properties including gingipain, haemagglutinin and biofilm formation. Antimicrobial effects and morphological changes of quercetin on P. gingivalis were detected. The effects of quercetin on gingipains activities and hemolytic, hemagglutination activities were evaluated using chromogenic peptides and sheep erythrocytes. The biofilm biomass and metabolism with different concentrations of quercetin were assessed by the crystal violet and MTT assay. The structures and thickness of the biofilms were observed by confocal laser scanning microscopy. Bacterial cell surface properties including cell surface hydrophobicity and aggregation were also evaluated. The mRNA expression of virulence and iron/heme utilization was assessed using real time-PCR. Quercetin exhibited antimicrobial effects and damaged the cell structure. Quercetin can inhibit gingipains, hemolytic, hemagglutination activities and biofilm formation at sub-MIC concentrations. Molecular docking analysis further indicated that quercetin can interact with gingipains. The biofilm became sparser and thinner after quercetin treatment. Quercetin also modulate cell surface hydrophobicity and aggregation. Expression of the genes tested was down-regulated in the presence of quercetin. In conclusion, our study demonstrated that quercetin inhibited various virulence factors of P. gingivalis.

Monoclonal Antibodies as an Antibacterial Approach Against Bacterial Pathogens

In the beginning of the 21st century, the frequency of antimicrobial resistance (AMR) has reached an apex, where even 4th and 5th generation antibiotics are becoming useless in clinical settings. In turn, patients are suffering from once-curable infections, with increases in morbidity and mortality. The root cause of many of these infections are the ESKAPEE pathogens (Enterococcus species, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, Enterobacter species, and Escherichia coli), which thrive in the nosocomial environment and are the bacterial species that have seen the largest rise in the acquisition of antibiotic resistance genes. While traditional small-molecule development still dominates the antibacterial landscape for solutions to AMR, some researchers are now turning to biological approaches as potential game changers. Monoclonal antibodies (mAbs)—more specifically, human monoclonal antibodies (Hu-mAbs)—have been highly pursued in the anti-cancer, autoimmune, and antiviral fields with many success stories, but antibody development for bacterial infection is still just scratching the surface. The untapped potential for Hu-mAbs to be used as a prophylactic or therapeutic treatment for bacterial infection is exciting, as these biologics do not have the same toxicity hurdles of small molecules, could have less resistance as they often target virulence proteins rather than proteins required for survival, and are narrow spectrum (targeting just one pathogenic species), therefore avoiding the disruption of the microbiome. This mini-review will highlight the current antibacterial mAbs approved for patient use, the success stories for mAb development, and new Hu-mAb products in the antibacterial pipeline.

Recognition of Porphyromonas gingivalis gingipain epitopes by natural IgM binding to malondialdehyde modified low-density lipoprotein

Objective

Increased risk for atherosclerosis is associated with infectious diseases including periodontitis. Natural IgM antibodies recognize pathogen-associated molecular patterns on bacteria, and oxidized lipid and protein epitopes on low-density lipoprotein (LDL) and apoptotic cells. We aimed to identify epitopes on periodontal pathogen Porphyromonas gingivalis recognized by natural IgM binding to malondialdehyde (MDA) modified LDL.

Methods and Results

Mouse monoclonal IgM (MDmAb) specific for MDA-LDL recognized epitopes on P. gingivalis on flow cytometry and chemiluminescence immunoassays. Immunization of C57BL/6 mice with P. gingivalis induced IgM, but not IgG, immune response to MDA-LDL and apoptotic cells. Immunization of LDLR^−/− mice with P. gingivalis induced IgM, but not IgG, immune response to MDA-LDL and diminished aortic lipid deposition. On Western blot MDmAb bound to P. gingivalis fragments identified as arginine-specific gingipain (Rgp) by mass spectrometry. Recombinant domains of Rgp produced in E. coli were devoid of phosphocholine epitopes but contained epitopes recognized by MDmAb and human serum IgM. Serum IgM levels to P. gingivalis were associated with anti-MDA-LDL levels in humans.

Conclusion

Gingipain of P. gingivalis is recognized by natural IgM and shares molecular identity with epitopes on MDA-LDL. These findings suggest a role for natural antibodies in the pathogenesis of two related inflammatory diseases, atherosclerosis and periodontitis.

Vaccines against periodontitis: a forward-looking review

Periodontal disease, as a polymicrobial disease, is globally endemic as well as being a global epidemic. It is the leading cause for tooth loss in the adult population and has been positively related to life-threatening systemic diseases such as atherosclerosis and diabetes. As a result, it is clear that more sophisticated therapeutic modalities need to be developed, which may include vaccines. Up to now, however, no periodontal vaccine trial has been successful in satisfying all the requirements; to prevent the colonization of a multiple pathogenic biofilm in the subgingival area, to elicit a high level of effector molecules such as immunoglobulin sufficient to opsonize and phagocytose the invading organisms, to suppress the induced alveolar bone loss, or to stimulate helper T-cell polarization that exerts cytokine functions optimal for protection against bacteria and tissue destruction. This article reviews all the vaccine trials so as to construct a more sophisticated strategy which may be relevant in the future. As an innovative strategy to circumvent these barriers, vaccine trials to stimulate antigen-specific T-cells polarized toward helper T-cells with a regulatory phenotype (Tregs, CD4+, CD25+, FoxP3+) have also been introduced. Targeting not only a single pathogen, but polymicrobial organisms, and targeting not only periodontal disease, but also periodontal disease-triggered systemic disease could be a feasible goal.

Porphyromonas gingivalis fimbriae-dependent interleukin-6 autocrine regulation by increase of gp130 in endothelial cells

BACKGROUND AND OBJECTIVE

Local persistent infection by Porphyromonas gingivalis leads to inflammatory systemic diseases, such as atherosclerosis. We have reported previously that avirulent P. gingivalis fimbriae-dependent invasion into endothelial cells might be involved in progression of atherosclerosis. Although interleukin-6 (IL-6) regulates progression of atherosclerosis, little is known about the relationship of P. gingivalis fimbriae-dependent invasion to IL-6 regulation in endothelial cells.

MATERIAL AND METHODS

We examined the secretion of IL-6 and the expression of the IL-6 signal transducer gp130 in human umbilical vein endothelial cells (HUVEC) infected with the wild-type FDC381 strain of P. gingivalisand a fimbriae-deficient mutant (fimA) by enzyme-linked immunosorbent assay, quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and flow cytometry (fluorescence-activated cell sorting, FACS) analysis.

RESULTS

Coculture of HUVEC with P. gingivalis resulted in increase of IL-6 secretion at 24 h postinfection. Interestingly, the increase was inhibited significantly in HUVEC infected with the P. gingivalis fimA mutant. In addition, the increase of IL-6 secretion induced by P. gingivalis infection was significantly impaired by the meiosis specific kinase 1 inhibitor, PD98059, or the nuclear factor kappaB inhibitor, Bay11-7082. Furthermore, we demonstrated that gp130 expression increased with P. gingivalis infection. Importantly, gp130 expression was significantly impaired by P gingivalis fimA mutant infection compared with wild-type P. gingivalis infection, as assessed by both quantitative RT-PCR and FACS analysis.

CONCLUSION

Our findings indicate that P. gingivalis fimbriae are important factors in the autocrine regulation of IL-6, by increasing gp130 in endothelial cells.

Vaccination against periodontitis: the saga continues

Periodontal disease can be considered to be one of the most common chronic inflammatory diseases inflicting humans. With the advent of advanced molecular diagnostic techniques, a better understanding of the role of specific pathogens and the contributory role of the host immune response in the initiation and progression of periodontal disease has been possible - although not completely. However, successful vaccine development that fully utilizes the current level of understanding has not yet occurred for human use. This paper reviews various in vitro, animal studies and human trials undertaken to develop a vaccine against periodontal disease, with emphases on the shortfalls of these efforts and future prospects of developing a successful vaccine against periodontal disease.

Protective and destructive immunity in the periodontium: Part 1--innate and humoral immunity and the periodontium

Based on the results of recent research in the field, the present paper will discuss the protective and destructive aspects of the innate vs. adaptive (humoral and cell-mediated) immunity associated with the bacterial virulent factors or antigenic determinants during periodontal pathogenesis. Attention will be focused on: (i) the Toll-like receptors (TLR), the innate immune repertoire for recognizing the unique molecular patterns of microbial components that trigger innate and adaptive immunity for effective host defenses, in some general non-oral vs. periodontal microbial infections; (ii) T-cell-mediated immunity, Th-cytokines, and osteoclastogenesis in periodontal disease progression; and (iii) some molecular techniques developed and used to identify critical microbial virulence factors or antigens associated with host immunity (using Actinobacillus actinomycetemcomitans and Porphyromonas gingivalis as the model species). Therefore, further understanding of the molecular interactions and mechanisms associated with the host's innate and adaptive immune responses will facilitate the development of new and innovative therapeutics for future periodontal treatments.

Antibody responses to Porphyromonas gingivalis hemagglutinin A and outer membrane protein in chronic periodontitis

BACKGROUND

Hemagglutinin and outer membrane protein (OMP) are major virulence factors associated with colonization of Porphyromonas gingivalis in the gingival crevice. The genes for the 200-kDa antigenic protein (200-kDa AP) and 40-kDa OMP of P. gingivalis have been successfully cloned. Additionally, the 200-kDa AP gene has been shown to constitute the hemagglutinin A (hagA) gene of P. gingivalis. Therefore, this study was constructed to evaluate the distributions and serum levels of immnoglobulin G (IgG) antibodies specific for 200-kDa AP and 40-kDa OMP in periodontitis patients.

METHODS

Fifty patients with chronic periodontitis and 59 controls without periodontal destruction were enrolled in this study. We cloned the genes for 200-kDa AP and 40-kDa OMP from P. gingivalis and constructed the purified recombinant proteins. Serum levels of IgG subclass antibodies specific for both recombinant 200-kDa and 40-kDa OMP were determined in patients and controls by an enzyme-linked immunosorbent assay (ELISA).

RESULTS

The serum IgG subclass distribution for patients and controls was IgG1>IgG4>IgG2>IgG3 in the anti-200-kDa AP response, which was almost identical to that in the anti-40-kDa OMP response. The patient group showed significantly higher serum IgG responses to the 40-kDa OMP than the control group (P<0.01). In contrast, IgG subclass responses to the 200-kDa AP were not different between the patients and controls. Serum levels of antibodies reactive with both 200-kDa and 40-kDa proteins did not have a significant association with mean probing depth.

CONCLUSION

These results suggested that serum IgG responses against P. gingivalis OMP rather than the hagA may be more active in chronic periodontitis.

Immune responses and vaccination against periodontal infections

BACKGROUND

The infectious aetiology of periodontitis is complex and no curative treatment modality exists. Palliative therapy is available.

AIMS

To review the evidence that active or passive immunization against periodontitis provides immune protection.

MATERIAL AND METHODS

PubMed (Medline), the National Institutes of Health, the Food and Drug Administration, and the Center for Disease Control electronic databases were searched to extrapolate information on immune responses to immunization against periodontitis.

RESULTS

Studies in non-human primate models using ligature-induced experimental periodontitis suggest that antibody responses by active immunization against Porphyromonas gingivalis can safely be induced, enhanced, and obtained over time. Immune responses to whole bacterial cell and purified protein preparations considered as vaccine candidates have been evaluated in different animal models demonstrating that there are several valid vaccine candidates. Data suggest that immunization reduces the rate and severity of bone loss. It is also, temporarily, possible to alter the composition of the subgingival microflora. Natural active immunization by therapeutic interventions results in antibody titre enhancement and potentially improves treatment outcomes. Passive immunization of humans using P. gingivalis monoclonal antibodies temporarily prevents colonization of P. gingivalis. Probiotic therapy may be an alternative approach. Regulatory and safety issues for human periodontal vaccine trials must be considered. Shared infectious aetiology between periodontitis and systemic diseases may enhance vaccine effort developments.

CONCLUSIONS

Proof of principle that active and passive immunization can induce protective antibody responses is given. The impact of natural immunization and passive immunization in humans should be explored and may, presently, be more feasible than active immunization studies.

Targeting of Porphyromonas gingivalis with a bispecific antibody directed to FcalphaRI (CD89) improves in vitro clearance by gingival crevicular neutrophils

Phagocytosis and killing of pathogens by polymorphonuclear neutrophils (PMN) from gingival crevicular fluid (GCF) is diminished in chronic periodontitis patients. As an approach to improve targeting of PMN toward a periodontopathogen, Porphyromonas gingivalis, the efficacy of a bispecific antibody (BsAb) directed against both recombinant 130 kDa hemagglutinin domain (r130k-HMGD) of P. gingivalis, and PMN Fc receptor (FcR) was evaluated. GCF PMN exhibited higher IgA FcR (FcalphaRI) levels, and lower IgG FcR (FcgammaRIIa and FcgammaRIIIb) levels than PB PMN. Functional studies revealed that GCF PMN exhibited a higher capacity to phagocytose and kill P. gingivalis opsonized with a BsAb targeting P. gingivalis r130k-HMGD to FcalphaRI as compared to an anti-r130k-HMGD antibody. However, phagocytosis and killing activity of PB PMN that were incubated with the two antibodies proved comparable. These data support targeting of pathogens toward FcalphaRI as an option to improve antibacterial immunity in chronic periodontitis patients.

Construction of novel human monoclonal antibodies neutralizing Porphyromonas gingivalis hemagglutination activity using transgenic mice expressing human Ig loci

Porphyromonas gingivalis has been implicated as an important pathogen in the development of adult periodontitis, and its colonization of subgingival sites is critical in the pathogenic process. One potential virulence factor, hemagglutinin, may mediate bacteria attachment onto and penetration into host cells, as well as agglutinate and lyses erythrocytes to intake heme, an absolute requirement for growth. Toward the development of passive immunotherapy, the construction of a human type monoclonal antibody, which is capable of inhibiting the hemagglutinating ability, will be significant and important. The human mAbs, both exhibiting a high degree of specificity and affinity against the recombinant 130 kDa hemagglutinin domain protein have been prepared using XenoMouse technology. The constructed Xeno-mAbs, IgG2 subclass, significantly inhibited hemagglutination of P. gingivalis and its vesicles. The newly constructed Xeno-mAbs may prove to be useful for the development of passive immunization against periodontal diseases caused by P. gingivalis infection, pending the results of fertility study in disease mode.

Subcloning of the 200-kDa Porphyromonas gingivalis antigen gene and inhibition of hemagglutination by an antibody against the recombinant protein

Porphyromonas gingivalis is a major etiologic agent of periodontitis and exhibits hemagglutinating and adherence activities. We previously succeeded in molecular cloning the 200-kDa cell-surface antigenic protein (200-k AP), designated pMD101, that is recognized in sera from periodontitis patients, and identified the 200-k AP as a hemagglutinin A (HagA) derivative. HagA is one of the hemagglutinins known to be a useful vaccine against periodontitis. HagA has four large, contiguous, direct repeats and the repeat unit is believed to contain the hemagglutinin domain. Because production of 200-k AP was low in the Escherichia coli host, it was difficult to obtain large amounts of recombinant protein. In this study, we attempt to subclone the gene encoding the useful antigen from pMD101 in an effort to obtain large quantities. A subclone, designated pMD160, encoding a fusion protein of 80-kDa HagA and maltose-binding protein was successfully constructed, and the novel clone produced relatively large amounts of recombinant protein. DNA nucleotide sequences of the pMD160 insert demonstrated that the 80-kDa protein contained a short hemagglutinin motif and a direct repeat unit region. The recombinant protein was purified to homogeneity and rabbit antiserum was raised. The antibody was capable of inhibiting the hemagglutinating activity of P. gingivalis. These findings suggest that novel 80-kDa HagA derivative proteins can be produced efficiently from E. coli hosts and these may be useful in developing immunotherapy against periodontitis infected by P. gingivalis.