Production of Monoclonal Antibodies Specific to FimA of Porphyromonas gingivalis and Their Inhibitory Activity on Bacterial Binding

Protection Against Pneumonia Induced by Vaccination with Fimbriae Subunits from Klebsiella pneumoniae

BACKGROUND

Klebsiella pneumoniae infections pose a great burden worldwide, causing high morbidity and mortality, which are worsened by the increase in multidrug-resistant strains. New therapeutic/prophylactic strategies are urgently needed to overcome antibiotic resistance and reduce the health and economic impacts of diseases caused by this pathogen. Fimbriae are important virulence factors involved in biofilm formation and adhesion to host cells. Their exposed location, conservation among clinical isolates and adjuvant properties make them interesting candidates for inclusion in protein-based vaccines. Therefore, the present work investigated the immunological potential of type 1 and 3 fimbriae subunits in a murine model of K. pneumoniae lung infection.

METHODS

MrkA and FimA were produced as recombinant proteins in E. coli, purified and used to immunize mice subcutaneously. The immune responses were characterized and protection against pneumonia was evaluated after intranasal challenge.

RESULTS

Subcutaneous immunization with recombinant FimA and MrkA induced high IgG1 production; the antibodies efficiently recognized the native proteins at the bacterial surface, promoted C3 deposition and reduced biofilm formation by K. pneumoniae in vitro. Mice vaccinated with the co-administered proteins reduced the bacterial loads in the lungs after intranasal challenge, less inflammation and reduced tissue damage.

CONCLUSION

The results suggest that both type 1 and type 3 fimbriae contribute to protection against K. pneumoniae lung infection, inducing antibodies that bind to the bacteria and favoring Complement deposition and clearance by the host, while inhibiting biofilm formation.

Development of monoclonal antibodies against P. gingivalis Mfa1 and their protective capacity in an experimental periodontitis model

Porphyromonas gingivalis (P. gingivalis), a gram-negative, black-pigmented anaerobe, is a major etiological agent and a leading cause of periodontitis. Fimbriae protein Mfa1 is a key virulence factor of P. gingivalis and plays a crucial role in bacterial adhesion, colonization, biofilm formation, and persistent inflammation, making it a promising therapeutic target. However, the role of anti-Mfa1 antibodies and the underlying protective mechanisms remain largely unexplored. Here, we developed and characterized the monoclonal antibodies (mAbs) targeting the Mfa1 protein of P. gingivalis. Function analysis showed that anti-Mfa1 mAbs mediated bacterial agglutination and inhibited P. gingivalis adhesion to saliva-coated hydroxyapatite and host cells. Notably, anti-Mfa1 mAbs significantly reduced bacterial burden and alveolar bone loss in a P. gingivalis-induced experimental periodontitis model. These results show that anti-Mfa1 mAbs can be beneficial in alleviating P. gingivalis infections, and provide important insights for the development of adequate adjuvant treatment regimens for Mfa1-targeted therapeutics.

IMPORTANCE

Fimbriae (pili) play an important role in bacterial adhesion, invasion of host cells and tissues, and formation of biofilms. Studies have shown that two types of fimbriae of Porphyromonas gingivalis, FimA and Mfa1, are important for colonization and infection through their binding to host tissues and other bacteria. While anti-FimA antibodies have been shown to improve periodontitis, the effect of anti-Mfa1 antibodies on P. gingivalis infection and periodontitis was previously unknown. In this study, we report for the first time that anti-Mfa1 monoclonal antibodies can reduce P. gingivalis infection and improve periodontitis. These findings suggest that Mfa1 represents a promising therapeutic target, and the development of anti-Mfa1 mAbs holds a potential as essential diagnostic and adjunctive therapeutic tools for managing P. gingivalis-related diseases.

Interrupting oral infection of Porphyromonas gingivalis with anti-FimA antibody attenuates bacterial dissemination to the arthritic joint and improves experimental arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that typically results in strong inflammation and bone destruction in the joints. It is generally known that the pathogenesis of RA is linked to cardiovascular and periodontal diseases. Though rheumatoid arthritis and periodontitis share many pathologic features such as a perpetual inflammation and bone destruction, the precise mechanism underlying a link between these two diseases has not been fully elucidated. Collagen-induced arthritis (CIA) mice were orally infected with Porphyromonas gingivalis (Pg) or Pg preincubated with an anti-FimA antibody (FimA Ab) specific for fimbriae that are flexible appendages on the cell surface. Pg-infected CIA mice showed oral microbiota disruption and increased alveolar bone loss and had synovitis and joint bone destruction. However, preincubation with FimA Ab led to a significant reduction in the severity of both oral disease and arthritis. Moreover, FimA Ab attenuated bacterial attachment and aggregation on human gingival and rheumatoid arthritis synovial fibroblasts. In addition, we discovered bacteria may utilize dendritic cells, macrophages and neutrophils to migrate into the joints of CIA mice. These results suggest that disrupting Pg fimbriae function by FimA Ab ameliorates RA.

Potent In Vitro and In Vivo Activity of Plantibody Specific for Porphyromonas gingivalis FimA

Fimbrial protein fimbrillin (FimA), a major structural subunit of Porphyromonas gingivalis, has been suggested as a vaccine candidate to control P. gingivalis-induced periodontal disease. Previously, cDNAs encoding IgG monoclonal antibodies (MAbs) against purified FimA from P. gingivalis 2561 have been cloned, and the MAbs have been produced in rice cell suspension. Here we examined the biological activities of the plant-produced MAb specific for FimA (anti-FimA plantibody) of P. gingivalis in vitro and in vivo. The anti-FimA plantibody recognized oligomeric/polymeric forms of native FimA in immunoblot analysis and showed high affinity for native FimA (KD = 0.11 nM). Binding of P. gingivalis (10(8) cells) to 2 mg of saliva-coated hydroxyapatite beads was reduced by 53.8% in the presence of 1 μg/ml plantibody. Anti-FimA plantibody (10 μg/ml) reduced invasion of periodontal ligament cells by P. gingivalis (multiplicity of infection, 100) by 68.3%. Intracellular killing of P. gingivalis opsonized with the anti-FimA plantibody by mouse macrophages was significantly increased (77.1%) compared to killing of bacterial cells with irrelevant IgG (36.7%). In a mouse subcutaneous chamber model, the number of recoverable P. gingivalis cells from the chamber fluid was significantly reduced when the numbers of bacterial cells opsonized with anti-FimA plantibody were compared with the numbers of bacterial cells with irrelevant IgG, 66.7% and 37.1%, respectively. These in vitro and in vivo effects of anti-FimA plantibody were comparable to those of the parental MAb. Further studies with P. gingivalis strains with different types of fimbriae are needed to investigate the usefulness of anti-FimA plantibody for passive immunization to control P. gingivalis-induced periodontal disease.

Cloning and characterization of heavy and light chain genes encoding the FimA-specific monoclonal antibodies that inhibit Porphyromonas gingivalis adhesion

FimA of Porphyromonas gingivalis, a major pathogen in periodontitis, is known to be closely related to the virulence of these bacteria and has been suggested as a candidate for development of a vaccine against periodontal disease. In order to develop a passive immunization method for inhibiting the establishment of periodontal disease, B hybridoma clones 123-123-10 and 256-265-9, which produce monoclonal antibodies (Mabs) specific to purified fimbriae, were established. Both mAbs reacted with the conformational epitopes displayed by partially dissociated oligomers of FimA, but not with the 43 kDa FimA monomer. Gene sequence analyses of full-length cDNAs encoding heavy and light chain immunoglobulins enabled classification of the genes of mAb 123-123-10 as members of the mVh II (A) and mVκ I subgroups, and those of mAb 256-265-9 as members of the mVh III (D) and mVκ I subgroups. More importantly, 50 ng/mL of antibodies purified from the culture supernatant of antibody gene-transfected CHO cells inhibited, by approximately 50%, binding of P. gingivalis to saliva-coated hydroxyapatite bead surfaces. It is expected that these mAbs could be used as a basis for passive immunization against P. gingivalis-mediated periodontitis.

Staphylococcus sciuri exfoliative toxin C (ExhC) is a necrosis-inducer for mammalian cells

Staphylococcus sciuri (S. sciuri) is a rare pathogen in humans, but it can cause a wide array of human infections. Recently a S. sciuri isolate (HBXX06) was reported to cause fatal exudative epidermitis (EE) in piglets and thus considered as a potential zoonotic agent. To investigate the pathogenicity of this bacterium, we cloned exfoliative toxin C (ExhC), a major toxin of the S. sciuri isolate and performed functional analysis of the recombinant ExhC-his (rExhC) protein using in vitro cell cultures and newborn mice as models. We found that rExhC could induce necrosis in multiple cell lines and peritoneal macrophages as well as skin lesions in newborn mice, and that the rExhC-induced necrosis in cells or skin lesions in newborn mice could be completely abolished if amino acids 79-128 of rExhC were deleted or blocked with a monoclonal antibody (3E4), indicating aa 79-128 portion as an essential necrosis-inducing domain. This information contributes to further understandings of the mechanisms underlying S. sciuri infection.