Prospects for gene-based immunopharmacology in salivary glands

Gene therapeutics in Sjögren's syndrome

Sjögren's syndrome (SS) is a complex autoimmune disorder, characterised by mononuclear cell infiltration of exocrine glands, principally the lacrimal and salivary glands. Both cellular, in the form of autoreactive immune cells, and humoral factors, such as autoantibodies, contribute to the expression of the disease. SS can also occur as a systemic disease affecting several organs, and approximately 5% of the patients develop malignant lymphoproliferation. Today SS is considered uncurable. The treatment available is only palliative, and the treatment goals are to manage symptoms and prevent or limit tissue damage. This may involve both local and systemic measures. However, the existing systemic treatment of chronic inflammatory autoimmune diseases has several limitations and unwanted side effects. In recent years the possibility to treat diseases with gene therapy has gained interest and has become a subject of investigation. Given the multitude of factors contributing to the pathogenesis of SS, gene therapy is a major challenge, but may elicit great benefits if successful. Keeping this in mind, the possibility for gene therapeutics in SS in general and potential targets for gene therapy are discussed.

The National Institute of Dental and Craniofacial Research: research for the practicing dentist

BACKGROUND AND OVERVIEW

Established in 1948, the National Institute of Dental and Craniofacial Research (NIDCR) has helped transform dentistry into a profession that is based firmly in prevention and technological innovation. This article introduces the new NIDCR initiative in general dentistry practice-based research. It also highlights research supported by the NIDCR and its implications for dental practice in restorative dentistry, oral and systemic disease, stem cell research, salivary diagnostics, gene transfer therapy and pain.

CLINICAL IMPLICATIONS

The NIDCR supports research that will help guide the practitioner in the delivery of patient care and have a direct impact on the practice of dentistry.

Radiotherapy-induced salivary dysfunction

Dry mouth (xerostomia) is one of the most common complaints following radiation therapy (RT) for head and neck cancers. Notably, RT causes irreparable damage to salivary glands that increases the risk for severe and long-term oral and pharyngeal disorders. Several strategies in the treatment of head and neck cancers have been developed to prevent RT-induced salivary dysfunction while providing definitive oncologic therapy. These include salivary-sparing RT; cytoprotectants (such as amifostine); combination therapy of high-dose-rate intraoperative RT, external beam RT, plus a cytoprotectant; salivary gland surgical transfer; and gene therapy. Future research that incorporates biologic, pharmacologic, and technologic advancements that optimize therapeutic ratios and minimizes adverse oral sequelae is warranted.

Local adeno-associated virus-mediated interleukin 10 gene transfer has disease-modifying effects in a murine model of Sjögren's syndrome

Female nonobese diabetic (NOD) mice develop spontaneous autoimmune sialadenitis and loss of salivary flow, and are a widely used model of Sjögren's syndrome. We examined the feasibility of local salivary gland immunomodulatory gene delivery to alter these sequelae in NOD mice. We constructed recombinant adeno-associated virus (rAAV) vectors encoding either human interleukin 10 (rAAVhIL-10) or beta-galactosidase (rAAVLacZ, control vector). Mice received rAAVhIL-10 or rAAVLacZ by retrograde submandibular ductal instillation either at age 8 weeks (early, before onset of sialadenitis), or at 16 weeks (late, after onset of sialadenitis). As a systemic treatment control, separate mice received intramuscular delivery of rAAVhIL-10 at each time point. Both submandibular and intramuscular delivery of vector led to low circulating levels of hIL-10. After submandibular administration of rAAVhIL-10, salivary flow rates at 20 weeks for both the early and late treatment groups were significantly higher than for both rAAVLacZ-administered and untreated mice. Systemic delivery of rAAVhIL-10 led to improved salivary flow in the late treatment group. Inflammatory infiltrates in submandibular glands, however, were significantly reduced only in mice receiving rAAVhIL-10 locally in the salivary gland compared with mice receiving this vector intramuscularly, or rAAVLacZ or no treatment. In addition, after submandibular rAAVhIL-10 delivery, NOD mice exhibited significantly lower blood glucose, and higher serum insulin, levels than all other groups, indicating some systemic benefit of this treatment. These studies show that expression of hIL-10 by rAAV vectors can have disease-modifying effects in the salivary glands of NOD mice, and suggest that local immunomodulatory gene transfer may be useful for managing the salivary gland pathology in Sjögren's syndrome.

Xerostomia and the geriatric patient

Saliva is essential for the preservation of oral-pharyngeal health, and disorders of salivary physiology are associated with numerous oral and pharyngeal problems, particularly in older people. Although salivary function is remarkably intact in healthy aging, medical problems, medications, and head and neck radiotherapy can cause salivary dysfunction and complaints of xerostomia among older people. Sjögren's syndrome, an autoimmune exocrinopathy, is the most common medical disease associated with salivary dysfunction. Medications with anticholinergic side effects will impair salivary output, and head and neck radiotherapy for cancer will cause permanent destruction of salivary glands. Treatments for salivary problems are based upon establishing a diagnosis, protecting oral and pharyngeal health, stimulating remaining glands, and replacing lost salivary fluids.

Recombinant adeno-associated virus serotype 2 vectors mediate stable interleukin 10 secretion from salivary glands into the bloodstream

We have constructed a recombinant adeno-associated virus serotype 2 vector encoding human interleukin 10 (rAAVhIL10). IL-10 is a potent antiinflammatory/immune cytokine, which has received growing attention for its therapeutic potential. Human IL-10 (hIL-10) production was virus dose dependent after in vitro infection of HSG cells, a human submandibular gland cell line. The vector-derived hIL-10 produced was biologically active, as the medium from rAAVhIL10-infected HSG cells caused a dose-dependent blockade of IL-12 secretion from spleen cells of IL-10 knockout mice challenged with heat-killed Brucella abortus. Administration of rAAVhIL10 (10(10) genomes per gland) to both mouse submandibular glands led to hIL-10 secretion into the bloodstream (approximately 1-5 pg/ml), that is, in an endocrine manner, which was stable for approximately 2 months. Salivary gland administration of rAAVhIL10 under experimental conditions was more efficacious than intravenous administration (approximately 0.5-0.7 pg/ml). Also, hIL-10 was readily secreted in vitro from organ cultures of minced submandibular glands infected with rAAVhIL10, 6 or 8 weeks earlier. Consistent with these results, hIL-10 mRNA was detected by reverse transcription-polymerase chain reaction in submandibular glands of mice infected with rAAVhIL10 but not from control mice. At these doses, little to no hIL-10 was detected in mouse saliva. Using a rAAV serotype 2 vector encoding beta-galactosidase, we observed that the primary parenchymal target cells were ductal. These findings represent the first report of rAAV use to target exocrine glands for systemic secretion of a therapeutic protein, and support the notion that rAAV serotype 2 vectors may be useful in salivary glands for local (periglandular) and systemic gene-based protein therapeutics.

The impact of gene therapy on dentistry: a revisiting after six years

BACKGROUND

Gene therapy is an emerging field of biomedicine that has commanded considerable scientific and popular attention. The procedure involves the transfer of genes to patients for clinical benefit. Transferred genes can b e used for either reparative or pharmacological purposes.

OVERVIEW

In 1995, the first author and a colleague described the potential impact of gene therapy on dentistry, on the basis of initial studies of gene transfer applications to salivary glands, keratinocytes and cancer cells. Their conclusion was that gene therapy would have a significant impact on the nature of dental practice within 20 years. In this article, the authors consider research progress since 1995 and reexamine the earlier conclusion.

PRACTICE IMPLICATIONS

In the past six years, remarkable progress has been made in the field of gene therapy, including seven areas relevant to dental practice: bone repair, salivary glands, autoimmune disease, pain, DNA vaccinations, keratinocytes and cancer. While considerable problems remain, thus impeding the routine clinical use of gene transfer, gene therapy will have a pervasive and significant impact on areas of dental practice that are based in biological science. By 2015, this will translate into practitioners' having a wide range of novel biological treatment options for their patients.

Protection from experimental endotoxemia by a recombinant adeno-associated virus encoding interleukin 10

BACKGROUND

Interleukin 10 (IL-10) is a homodimeric cytokine that shows considerable clinical promise. Adeno-associated virus (AAV) vectors appear increasingly useful for in vivo gene-transfer applications.

METHODS

A recombinant AAV type 2 vector encoding human IL-10 (rAAVhIL10) was constructed by using an adenoviral-free, three-plasmid co-transfection. Cytokine production was measured by using an enzyme-linked immunosorbent assay. Endotoxic shock was induced by lipopolysaccharide (LPS) injection.

RESULTS

As media from rAAVhIL10-infected COS cells caused a dose-dependent blockade of IL-12 secretion from spleen cells of IL-10 knockout (KO) mice challenged with Brucella abortus, it was clear that vector-derived hIL-10 was biologically active in vitro. Intravenous or intramuscular administration of relatively modest levels of rAAVhIL10 (10(10) genomes) to IL-10 KO mice resulted in hIL-10 secretion into the bloodstream, which, at 8 weeks, gave median serum levels of 0.9 and 0.45 pg/ml, respectively. Acute endotoxic shock led to a 33% mortality rate, and severe morbidity, in control IL-10 KO mice, whereas no mortality and little morbidity were seen in IL-10 KO mice given rAAVhIL10 7 weeks earlier.

CONCLUSIONS

The findings demonstrate that a modest dose of rAAVhIL10 administered in vivo provides long-term protection against LPS-induced endotoxic shock in a murine model. Thus, this vector may be useful for clinical applications requiring sustained IL-10 expression, for example in the treatment of several autoimmune diseases.