Saliva, a biofluid historically well-studied biochemically and physiologically, has entered the post-genomic ‘omics’ era, where its proteomic, genomic, and microbiome constituents have been comprehensively deciphered. The translational path of these salivary constituents has begun toward a variety of personalized individual medical applications, including early detection of cancer. Salivary diagnostics is a late-comer, but it is catching up where dedicated resources, like the Salivaomics Knowledge Base (SKB), now have taken center stage in the dissemination of the diagnostic potentials of salivary biomarkers and other translational and clinical utilities.
salivary biochemistry and physiology; proteome; biomarkers; early detection; genomics; microbiome
There have been significant advances in techniques for the detection of biomarker signals in the oral cavity (e.g., ELISAs for proteins, PCR for RNA and DNA) as well as the engineering and development of microfluidic approaches to make oral-based point-of-care (POC) methods for the diagnosis for both local and systemic conditions a reality. In this section, we focus on three such approaches, namely, periodontal disease management, early markers for systemic diseases, and salivary markers useful for pharmacogenomic studies. Novel approaches using non-invasive, salivary samples and user-friendly devices offer results that are as sensitive and specific as laboratory-based analyses using blood or urine.
biomarkers; saliva; cardiovascular disease; pharmacogenomics; periodontal diseases; lab-on-a-chip
Pulp regeneration is considered in cases where the dental pulp has been destroyed because of microbial irritation. Diverse oral and food-borne micro-organisms are able to invade the pulp space, form biofilm on canal walls, and infiltrate dentinal tubules. Prior to pulp regeneration procedures, the pulp space and dentinal walls need to be sufficiently disinfected to allow for and promote regeneration. The necessary level of disinfection is likely higher than that accepted for traditional endodontic therapy, because in traditional techniques the mere lowering of bacterial loads and prevention of bacterial access to periapical tissues is conducive to healing. Moreover, several of the non-specific antimicrobials used in traditional endodontic therapy may cause significant changes in remaining dentin that interfere with its inherent potential to mediate regeneration. Non-specific antimicrobials also suppress all microbial taxa, which may allow residual virulent micro-organisms to preferentially repopulate the pulp space. Therefore, it is important for endodontic pathogens to be studied by molecular methods that allow for a broad depth of coverage. It is then essential to determine the most effective protocols to disinfect the pulp space, with minimal disruption of remaining dentin. These protocols include the topical use of effective antibiotics, including newer agents that have demonstrated efficacy against endodontic pathogens.
pulp necrosis; pulp regeneration; endodontic pathogens; endodontic irrigants; topical antibiotics; microbiota
Stem cells derived from the dental pulp of extracted human third molars (DPSCs) have the potential to differentiate into odontoblasts, osteoblasts, adipocytes, and neural cells when provided with the appropriate conditions. To advance the use of DPSCs for dentin regeneration, it is important to replicate the permissive signals that drive terminal events in odontoblast differentiation during tooth development. Such a strategy is likely to restore a dentin matrix that more resembles the tubular nature of primary dentin. Due to the limitations of culture conditions, the use of ex vivo gene therapy to drive the terminal differentiation of mineralizing cells holds considerable promise. In these studies, we asked whether the forced expression of TWIST1 in DPSCs could alter the potential of these cells to differentiate into odontoblast-like cells. Since the partnership between Runx2 and Twist1 proteins is known to control the onset of osteoblast terminal differentiation, we hypothesized that these genes act to control lineage determination of DPSCs. For the first time, our results showed that Twist1 overexpression in DPSCs enhanced the expression of DSPP, a gene that marks odontoblast terminal differentiation. Furthermore, co-transfection assays showed that Twist1 stimulates Dspp promoter activity by antagonizing Runx2 function in 293FT cells. Analysis of our in vitro data, taken together, suggests that lineage specification of DPSCs can be modulated through ex vivo gene modifications.
TWIST1; RUNX2; dental stem cells; gene transfer; odontoblast; tooth development
Despite impressive worldwide improvements in oral health, inequalities in oral health status among and within countries remain a daunting public health challenge. Oral health inequalities arise from a complex web of health determinants, including social, behavioral, economic, genetic, environmental, and health system factors. Eliminating these inequalities cannot be accomplished in isolation of oral health from overall health, or without recognizing that oral health is influenced at multiple individual, family, community, and health systems levels. For several reasons, this is an opportune time for global efforts targeted at reducing oral health inequalities. Global health is increasingly viewed not just as a humanitarian obligation, but also as a vehicle for health diplomacy and part of the broader mission to reduce poverty, build stronger economies, and strengthen global security. Despite the global economic recession, there are trends that portend well for support of global health efforts: increased globalization of research and development, growing investment from private philanthropy, an absolute growth of spending in research and innovation, and an enhanced interest in global health among young people. More systematic and far-reaching efforts will be required to address oral health inequalities through the engagement of oral health funders and sponsors of research, with partners from multiple public and private sectors. The oral health community must be “at the table” with other health disciplines and create opportunities for eliminating inequalities through collaborations that can harness both the intellectual and financial resources of multiple sectors and institutions.
global; oral health; inequalities; disparities; research; funding
The IADR Global Oral Health Inequalities Task Group on Dental Caries has synthesized current evidence and opinion to identify a five-year implementation and research agenda which should lead to improvements in global oral health, with particular reference to the implementation of current best evidence as well as integrated action to reduce caries and health inequalities between and within countries. The Group determined that research should: integrate health and oral health wherever possible, using common risk factors; be able to respond to and influence international developments in health, healthcare, and health payment systems as well as dental prevention and materials; and exploit the potential for novel funding partnerships with industry and foundations. More effective communication between and among the basic science, clinical science, and health promotion/public health research communities is needed. Translation of research into policy and practice should be a priority for all. Both community and individual interventions need tailoring to achieve a more equal and person-centered preventive focus and reduce any social gradient in health. Recommendations are made for both clinical and public health implementation of existing research and for caries-related research agendas in clinical science, health promotion/public health, and basic science.
Dental caries; health inequalities; health disparities; implementation research; translational research
The challenge of controlling HIV infection involves an understanding of the heterogeneity of the virus, its wide cellular host range, its primary routes of transmission, and the immunologic and intrinsic cellular factors that can prevent its transmission and replication. Identification of HIV-infected individuals who have survived more than 10 years without signs of the infection and without therapy encourages studies examining the natural mechanisms for resistance to infection and disease. Within the immune system, emphasis should be given to the innate or natural response that appears within minutes of the infection and offers the optimal time for controlling HIV. All these parameters in HIV pathogenesis underline the information needed to develop optimal anti-HIV therapies and an effective AIDS vaccine.
HIV heterogeneity; innate immunity; intracellular antiviral activity
Oropharyngeal candidiasis (OPC), caused primarily by Candida albicans, is the most common oral infection in HIV+ persons. Although Th1-type CD4+ T cells are the predominant host defense mechanism against OPC, CD8+ T cells and epithelial cells become important when blood CD4+ T cells are reduced below a protective threshold during progression to AIDS. In an early cross-sectional study, OPC+ tissue biopsied from HIV+ persons had an accumulation of activated memory CD8+ T cells at the oral epithelial–lamina propria interface, with reduced expression of the adhesion molecule E-cadherin, suggesting a protective role for CD8+ T cells but a dysfunction in the mucosal migration of the cells. In a subsequent 1-year longitudinal study, OPC− patients with high oral Candida colonization (indicative of a preclinical OPC condition), had higher numbers of CD8+ T cells distributed throughout the tissue, with normal E-cadherin expression. In OPC+ patients, where lack of CD8+ T cell migration was associated with reduced E-cadherin, subsequent evaluations following successful treatment of infection revealed normal E-cadherin expression and cellular distribution. Regarding epithelial cell responses, intact oral epithelial cells exhibit fungistatic activity via an acid-labile protein moiety. A proteomic analysis revealed that annexin A1 is a strong candidate for the effector moiety. The current hypothesis is that under reduced CD4+ T cells, HIV+ persons protected from OPC have CD8+ T cells that migrate to the site of a preclinical infection under normal expression of E-cadherin, whereas those with OPC have a transient reduction in E-cadherin that prohibits CD8+ T cells from migrating for effector function. Oral epithelial cells concomitantly function through annexin A1 to keep Candida in a commensal state but can easily be overwhelmed, thereby contributing to susceptibility to OPC.
AIDS; Candida albicans; epithelial cells; T cells; mucosal immunity; cytokines
The AIDS pandemic continues. Little is understood about how HIV gains access to permissive cells across mucosal surfaces, yet such knowledge is crucial to the development of successful topical anti-HIV-1 agents and mucosal vaccines. HIV-1 rapidly internalizes and integrates into the mucosal keratinocyte genome, and integrated copies of HIV-1 persist upon cell passage. The virus does not appear to replicate, and the infection may become latent. Interactions between HIV-1 and oral keratinocytes have been modeled in the context of key environmental factors, including putative copathogens and saliva. In keratinocytes, HIV-1 internalizes within minutes; in saliva, an infectious fraction escapes inactivation and is harbored and transferable to permissive target cells for up to 48 hours. When incubated with the common oral pathogen Porphyromonas gingivalis, CCR5− oral keratinocytes signal through protease-activated receptors and Toll-like receptors to induce expression of CCR5, which increases selective uptake of infectious R5-tropic HIV-1 into oral keratinocytes and transfer to permissive cells. Hence, oral keratinocytes—like squamous keratinocytes of other tissues—may be targets for low-level HIV-1 internalization and subsequent dissemination by transfer to permissive cells.
HIV/AIDS; epithelia; oral epithelium; infectious disease; mucosal immunity; vaccines
In this review, the authors survey the large number of antibacterial and antiviral proteins present in human saliva. Of interest, most of these antibacterial proteins display antiviral activity, typically against specific viral pathogens. The review focuses on one protein that interacts with both bacteria and viruses—gp340, originally referred to as salivary agglutinin. In the oral cavity, soluble gp340 binds to and aggregates a variety of bacteria, and this is thought to increase bacterial clearance from the mouth. However, when bound to the tooth surface, gp340 promotes bacterial adherence. In the oral cavity, most gp340 is found soluble in saliva and can function as a specific inhibitor of infectivity of HIV-1 and influenza A. In contrast, in the female reproductive track, most gp340 is bound to the cell surface, where it can promote HIV-1 infection.
HIV; AIDS; viral; antiviral; innate immune system
The Oral HIV/AIDS Research Alliance is part of the AIDS Clinical Trials Group, the largest HIV clinical trial organization in the world, and it is funded by the National Institute of Dental and Craniofacial Research, in collaboration with the National Institute of Allergy and Infectious Diseases. The alliance’s main objective is to investigate the oral complications associated with HIV/AIDS as the epidemic is evolving—in particular, the effects of potent antiretrovirals on the development of oral mucosal lesions and associated fungal and viral pathogens. Furthermore, oral fluids are being explored for their potential monitoring and diagnostic role with respect to HIV disease and coinfections. This article presents an overview of the alliance, its scientific agenda, and an outline of the novel interventional and noninterventional clinical studies ongoing and developing within the AIDS Clinical Trials Group infrastructure in the United States and internationally.
HIV/AIDS; OHARA; infectious diseases; AIDS Clinical Trials Group; oral cavity
With the advent of treatments and diseases such as AIDS resulting in increasing numbers of patients with suppressed immune systems, fungal diseases are an escalating problem. Candida albicans is the most common of these fungal pathogens, causing infections in many of these patients. It is therefore important to understand how immunity to this fungus is regulated and how it might be manipulated. Although work has been done to identify the receptors, fungal moieties, and responses involved in anti-Candida immunity, most studies have investigated interactions with myeloid or lymphoid cells. Given that the first site of contact of C. albicans with its host is the mucosal epithelial surface, recent studies have begun to focus on interactions of C. albicans with this site. The results are startling yet in retrospect obvious, indicating that epithelial cells play an important role in these interactions, initiating responses and even providing a level of protection. These findings have obvious implications, not just for fungal pathogens, but also for identifying how host organisms can distinguish between commensal and pathogenic microbes. This review highlights some of these recent findings and discusses their importance in the wider context of infection and immunity.
HIV/AIDS; mycology; innate immunity; oral epithelium; fungal pathogens
Viral infections are often associated with salivary gland pathology. Here we review the pathogenesis of HIV-associated salivary gland disease (HIV-SGD), a hallmark of diffuse infiltrative lymphocytosis syndrome. We investigate the presence and contributions of viral diseases to the pathogenesis of salivary gland diseases, particularly HIV-SGD. We have detected BK viral shedding in the saliva of HIV-SGD patients consistent with viral infection and replication, suggesting a role for oral transmission. For further investigation of BKV pathogenesis in salivary glands, an in vitro model of BKV infection is described. Submandibular (HSG) and parotid (HSY) gland salivary cell lines were capable of permissive BKV infection, as determined by BKV gene expression and replication. Analysis of these data collectively suggests the potential for a BKV oral route of transmission and salivary gland pathogenesis within HIV-SGD.
Virus; salivary gland; HIV; DILS
Bacteria adhere to a surface and, through cell division and coordinated expression of gene products, to develop into a structurally-complex population of adherent cells. This process, known as biofilm formation, requires that intrinsic and extrinsic signals are transduced into appropriate gene expression patterns as biofilms mature. Mutational analysis has begun to reveal the complexity of systems used by Streptococcus mutans to ensure proper biofilm formation. These studies have revealed new and unique targets for the design of broadly-effective anti-caries strategies.
Unlike many pathogens are foreign invaders, oral “pathogens” such as Streptococcus mutans are part of the “normal” oral microbial flora. While they express certain pathogenic properties, the balance of synergistic and antagonistic interactions determines whether these çommensal pathogens cause damage or not. Recognition of these microbial ecology based pathogeneses argues for new strategies for disease treatment and prevention.
Probiotics, potentially beneficial live bacteria or yeasts, have been used to combat dental caries. This includes the application of S. mutans types that cannot produce acids or other bacteria that interfere with the pathogenic effects of S. mutans. While these approaches show therapeutic effects against S. mutans experimentally, the conversion into commercial products remains a challenge, due to safety and shelf life issues. New high-tech approaches, such as quorum sensing interference of pathogenic bacteria or targeted antimicrobial therapies, offer novel ways to achieve probiotic effects against dental caries.
Actinobacillus actinomycetemcomitans causes periodontitis, a costly chronic infection that affects a large number of patients. The pathogenesis of this dental infection is a multifactorial process that results in a serious degenerative disease of the periodontium. Although significant progress has been achieved after the identification of this gram-negative bacterium as the etiological agent of this infection, much remains to be done to understand in detail the bacterial factors and host-pathogen interactions involved in the pathogenesis of this disease. Classical research approaches have resulted in the identification of important virulence factors and cellular processes, although they have provided a rather narrow picture of some of steps of this complex process. In contrast, a much wider picture could be obtained with the application of tools such as bioinformatics and genomics. These tools will provide global information regarding the differential expression of genes encoding factors and processes that lead to the pathogenesis of this disease. Furthermore, comparative genomics has the potential of helping to understand the emergence and evolution of this human pathogen. This genome-wide approach should provide a more complete picture of the pathogenesis process of this disease, and will facilitate the development of efficient diagnostic, preventive, and therapeutic measures for this disease.
A. actinomycetemcomitans; dental pathogen; genomics; bioinformatics; iron metabolism