Immunohistological analysis of Tannerella forsythia-induced lesions in a murine model

The intriguing strategies of Tannerella forsythia's host interaction

Tannerella forsythia, a member of the "red complex" bacteria implicated in severe periodontitis, employs various survival strategies and virulence factors to interact with the host. It thrives as a late colonizer in the oral biofilm, relying on its unique adaptation mechanisms for persistence. Essential to its survival are the type 9 protein secretion system and O-glycosylation of proteins, crucial for host interaction and immune evasion. Virulence factors of T. forsythia, including sialidase and proteases, facilitate its pathogenicity by degrading host glycoproteins and proteins, respectively. Moreover, cell surface glycoproteins like the S-layer and BspA modulate host responses and bacterial adherence, influencing colonization and tissue invasion. Outer membrane vesicles and lipopolysaccharides further induce inflammatory responses, contributing to periodontal tissue destruction. Interactions with specific host cell types, including epithelial cells, polymorphonuclear leukocytes macrophages, and mesenchymal stromal cells, highlight the multifaceted nature of T. forsythia's pathogenicity. Notably, it can invade epithelial cells and impair PMN function, promoting dysregulated inflammation and bacterial survival. Comparative studies with periodontitis-associated Porphyromonas gingivalis reveal differences in protease activity and immune modulation, suggesting distinct roles in disease progression. T. forsythia's potential to influence oral antimicrobial defense through protease-mediated degradation and interactions with other bacteria underscores its significance in periodontal disease pathogenesis. However, understanding T. forsythia's precise role in host-microbiome interactions and its classification as a keystone pathogen requires further investigation. Challenges in translating research data stem from the complexity of the oral microbiome and biofilm dynamics, necessitating comprehensive studies to elucidate its clinical relevance and therapeutic implications in periodontitis management.

Uncovering the Oral Dysbiotic Microbiota as Masters of Neutrophil Responses in the Pathobiology of Periodontitis

Numerous bacterial species participate in the shift of the oral microbiome from beneficial to dysbiotic. The biggest challenge lying ahead of microbiologists, immunologists and dentists is the fact that the bacterial species act differently, although usually synergistically, on the host immune cells, including neutrophils, and on the surrounding tissues, making the investigation of single factors challenging. As biofilm is a complex community, the members interact with each other, which can be a key issue in future studies designed to develop effective treatments. To understand how a patient gets to the stage of the late-onset (previously termed chronic) periodontitis or develops other, in some cases life-threatening, diseases, it is crucial to identify the microbial composition of the biofilm and the mechanisms behind its pathogenicity. The members of the red complex (Porphyromonas gingivalis, Treponema denticola, and Tannerella forsythia) have long been associated as the cause of periodontitis and stayed in the focus of research. However, novel techniques, such as 16S clonal analysis, demonstrated that the oral microbiome diversity is greater than ever expected and it opened a new era in periodontal research. This review aims to summarize the current knowledge concerning bacterial participation beyond P. gingivalis and the red complex in periodontal inflammation mediated by neutrophils and to spread awareness about the associated diseases and pathological conditions.

Periodontal Pathogens' strategies disarm neutrophils to promote dysregulated inflammation

Periodontitis is an irreversible, chronic inflammatory disease where inflammophilic pathogenic microbial communities accumulate in the gingival crevice. Neutrophils are a major component of the innate host response against bacterial challenge, and under homeostatic conditions, their microbicidal functions typically protect the host against periodontitis. However, a number of periodontal pathogens developed survival strategies to evade neutrophil microbicidal functions while promoting inflammation, which provides a source of nutrients for bacterial growth. Research on periodontal pathogens has largely focused on a few established species: Tannerella forsythia, Treponema denticola, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans, and Porphyromonas gingivalis. However, advances in culture-independent techniques have facilitated the identification of new bacterial species in periodontal lesions, such as the two Gram-positive anaerobes, Filifactor alocis and Peptoanaerobacter stomatis, whose characterization of pathogenic potential has not been fully described. Additionally, there is not a full understanding of the pathogenic mechanisms used against neutrophils by organisms that are abundant in periodontal lesions. This presents a substantial barrier to the development of new approaches to prevent or ameliorate the disease. In this review, we first summarize the neutrophil functions affected by the established periodontal pathogens listed above, denoting unknown areas that still merit a closer look. Then, we review the literature on neutrophil functions and the emerging periodontal pathogens, F. alocis and P. stomatis, comparing the effects of the emerging microbes to that of established pathogens, and speculate on the contribution of these putative pathogens to the progression of periodontal disease.

Polymicrobial periodontal disease triggers a wide radius of effect and unique virome

Periodontal disease is a microbially-mediated inflammatory disease of tooth-supporting tissues that leads to bone and tissue loss around teeth. Although bacterially-mediated mechanisms of alveolar bone destruction have been widely studied, the effects of a polymicrobial infection on the periodontal ligament and microbiome/virome have not been well explored. Therefore, the current investigation introduced a new mouse model of periodontal disease to examine the effects of a polymicrobial infection on periodontal ligament (PDL) properties, changes in bone loss, the host immune response, and the microbiome/virome using shotgun sequencing. Periodontal pathogens, namely Porphyromonas gingivalis, Treponema denticola, Tannerella forsythia, and Fusobacterium nucleatum were used as the polymicrobial oral inoculum in BALB/cByJ mice. The polymicrobial infection triggered significant alveolar bone loss, a heightened antibody response, an elevated cytokine immune response, a significant shift in viral diversity and virome composition, and a widening of the PDL space; the latter two findings have not been previously reported in periodontal disease models. Changes in the PDL space were present at sites far away from the site of insult, indicating that the polymicrobial radius of effect extends beyond the bone loss areas and site of initial infection and wider than previously appreciated. Associations were found between bone loss, specific viral and bacterial species, immune genes, and PDL space changes. These findings may have significant implications for the pathogenesis of periodontal disease and biomechanical properties of the periodontium. This new polymicrobial mouse model of periodontal disease in a common mouse strain is useful for evaluating the features of periodontal disease.

Human neutrophils and oral microbiota: a constant tug-of-war between a harmonious and a discordant coexistence

Neutrophils are a major component of the innate host response, and the outcome of the interaction between the oral microbiota and neutrophils is a key determinant of oral health status. The composition of the oral microbiome is very complex and different in health and disease. Neutrophils are constantly recruited to the oral cavity, and their protective role is highlighted in cases where their number or functional responses are impeded, resulting in different forms of periodontal disease. Periodontitis, one of the more severe and irreversible forms of periodontal disease, is a microbial-induced chronic inflammatory disease that affects the gingival tissues supporting the tooth. This chronic inflammatory disease is the result of a shift of the oral bacterial symbiotic community to a dysbiotic more complex community. Chronic inflammatory infectious diseases such as periodontitis can occur because the pathogens are able to evade or disable the innate immune system. In this review, we discuss how human neutrophils interact with both the symbiotic and the dysbiotic oral community; an understanding of which is essential to increase our knowledge of the periodontal disease process.

Filifactor alocis infection and inflammatory responses in the mouse subcutaneous chamber model

Recent microbiome studies have implicated a role for Filifactor alocis in periodontal disease. In this study, we investigated the colonization and survival properties of F. alocis in a mouse subcutaneous chamber model of infection and characterized host innate immune responses. An infection of 10(9) F. alocis successfully colonized all chambers; however, the infection was cleared after 72 h. F. alocis elicited a local inflammatory response with neutrophils recruited into the chambers at 2 h postinfection along with an increase in levels of the proinflammatory cytokines interleukin 1β (IL-1β), IL-6, and tumor necrosis factor (TNF). F. alocis also induced apoptosis in chamber epithelial cells and neutrophils. Consistent with resolution of infection, neutrophil numbers and cytokine levels returned to baseline by 72 h. Fluorescent in situ hybridization (FISH) and quantitative PCR demonstrated that F. alocis exited the chambers and spread to the spleen, liver, lung, and kidney. Massive neutrophil infiltration was observed in the spleen and lungs, and the recruited neutrophils were in close proximity to the infecting bacteria. Significant epithelial injury was observed in the kidneys. Infection of all tissues was resolved after 7 days. This first in vivo study of the pathogenicity of F. alocis shows that in the chamber model the organism can establish a proinflammatory, proapoptotic local infection which is rapidly resolved by the host concordant with neutrophil influx. Moreover, F. alocis can spread to, and transiently infect, remote tissues where neutrophils can also be recruited.

TLR2 signaling and Th2 responses drive Tannerella forsythia-induced periodontal bone loss

Periodontal disease (PD) is a chronic inflammation of the tooth-supporting soft tissue and alveolar bone due to infection by a select group of gram-negative microbes, which leads to tooth loss if untreated. Because mice deficient in CD4(+) cells are resistant to infection-induced alveolar bone loss, Th cells have been implicated in bone-destructive processes during PD. However, the extent to which different Th cell subtypes play roles in pathogenesis or host protection remains to be defined and is likely to vary depending on the dominant microorganism involved. By far, Porphyromonas gingivalis is the best-studied periodontal microbe in PD. Although the gram-negative anaerobe Tannerella forsythia is also a vital contributor to periodontal bone loss, almost nothing is known about immune responses to this organism. Previous studies from our laboratory revealed that T. forsythia induces periodontal bone loss in mice and that this bone loss depends on the bacterially expressed BspA protein. In this study, we showed that T. forsythia activates murine APCs primarily through TLR2-dependent signaling via BspA. Furthermore, T. forsythia infection causes a pronounced Th2 bias, evidenced by T cell expression of IL-5, but not IFN-γ or IL-17, in draining lymph nodes. Consistently, deficiencies in TLR2 or STAT6 result in resistance to T. forsythia-induced alveolar bone loss. Thus, TLR2 signaling and Th2 cells play pathogenic roles in T. forsythia-induced alveolar bone destruction.

Predominant bacteria recovered from a periodontitis site in a hamster model raised by silk-ligature with Porphyromonas gingivalis infection

We isolated oral bacteria that coexisted with Porphyromonas gingivalis in a hamster periodontitis model. As predominant bacteria in the periodontitis site, Collinsella-reltaed strains, Eubacterium-reltaed strains, Streptococcus suis-related strains, and Veillonella parvula-reltaed strains were detected. In addition, Actinomyces, Bacteroides, and P. gingivalis were also isolated predominantly. The results suggest that the bacterial composition of the periodontitis site in hamsters is complex, as in human periodontitis.

Acute leukemia immunohistochemistry: a systematic diagnostic approach

CONTEXT

The diagnosis and classification of leukemia is becoming increasingly complex. Current classification schemes incorporate morphologic features, immunophenotype, molecular genetics, and clinical data to specifically categorize leukemias into various subtypes. Although sophisticated methodologies are frequently used to detect characteristic features conferring diagnostic, prognostic, or therapeutic implications, a thorough microscopic examination remains essential to the pathologic evaluation. Detailed blast immunophenotyping can be performed with lineage- and maturation-specific markers. Although no one marker is pathognomonic for one malignancy, a well-chosen panel of antibodies can efficiently aid the diagnosis and classification of acute leukemias.

OBJECTIVE

To review important developments from recent and historical literature. General immunohistochemical staining patterns of the most commonly encountered lymphoid and myeloid leukemias are emphasized. The goal is to discuss the immunostaining of acute leukemias when flow cytometry and genetic studies are not available.

DATA SOURCES

A comprehensive review was performed of the relevant literature indexed in PubMed (National Library of Medicine) and referenced medical texts. Additional references were identified in the reviewed manuscripts.

CONCLUSIONS

Immunophenotyping of blasts using an immunohistochemical approach to lymphoid and myeloid malignancies is presented. Initial and subsequent additional antibody panels are suggested to confirm or exclude each possibility in the differential diagnosis and a general strategy for diagnostic evaluation is discussed. Although the use of immunohistochemistry alone is limited and evaluation by flow cytometry and genetic studies is highly recommended, unavoidable situations requiring analysis of formalin-fixed tissue specimens arise. When performed in an optimized laboratory and combined with a careful morphologic examination, the immunohistochemical approach represents a useful laboratory tool for classifying various leukemias.