Microbial oncogenesis

Parallels between pathogens and gluten peptides in celiac sprue

Pathogens are exogenous agents capable of causing disease in susceptible organisms. In celiac sprue, a disease triggered by partially hydrolyzed gluten peptides in the small intestine, the offending immunotoxins cannot replicate, but otherwise have many hallmarks of classical pathogens. First, dietary gluten and its peptide metabolites are ubiquitous components of the modern diet, yet only a small, genetically susceptible fraction of the human population contracts celiac sprue. Second, immunotoxic gluten peptides have certain unusual structural features that allow them to survive the harsh proteolytic conditions of the gastrointestinal tract and thereby interact extensively with the mucosal lining of the small intestine. Third, they invade across epithelial barriers intact to access the underlying gut-associated lymphoid tissue. Fourth, they possess recognition sequences for selective modification by an endogenous enzyme, transglutaminase 2, allowing for in situ activation to a more immunotoxic form via host subversion. Fifth, they precipitate a T cell–mediated immune reaction comprising both innate and adaptive responses that causes chronic inflammation of the small intestine. Sixth, complete elimination of immunotoxic gluten peptides from the celiac diet results in remission, whereas reintroduction of gluten in the diet causes relapse. Therefore, in analogy with antibiotics, orally administered proteases that reduce the host's exposure to the immunotoxin by accelerating gluten peptide destruction have considerable therapeutic potential. Last but not least, notwithstanding the power of in vitro methods to reconstitute the essence of the immune response to gluten in a celiac patient, animal models for the disease, while elusive, are likely to yield fundamentally new systems-level insights.

Does cytomegalovirus play a causative role in the development of various inflammatory diseases and cancer?

Human cytomegalovirus (HCMV) is a herpes virus that infects and is carried by 70-100% of the world's population. During its evolution, this virus has developed mechanisms that allow it to survive in an immunocompetent host. For many years, HCMV was not considered to be a major human pathogen, as it appeared to cause only rare cases of HCMV inclusion disease in neonates. However, HCMV is poorly adapted for survival in the immunosuppressed host and has emerged as an important human pathogen in AIDS patients and in patients undergoing immunosuppressive therapy following organ or bone marrow transplantation. HCMV-mediated disease in such patients has highlighted the possible role of this virus in the development of other diseases, in particular inflammatory diseases such as vascular diseases, autoimmune diseases and, more recently, with certain forms of cancers. Current research is focused on determining whether HCMV plays a causative role in these diseases or is merely an epiphenomenon of inflammation. Inflammation plays a central role in the pathogenesis of HCMV. This virus has developed a number of mechanisms that enable it to hide from the cells of the immune system and, at the same time, reactivation of a latent infection requires immune activation. Numerous products of the HCMV genome are devoted to control central functions of the innate and adaptive immune responses. By influencing the regulation of various cellular processes including the cell cycle, apoptosis and migration as well as tumour invasiveness and angiogenesis, HCMV may participate in disease development. Thus, the various drugs now available for treatment of HCMV disease (e.g. ganciclovir, acyclovir and foscarnet), may also prove to be useful in the treatment of other, more widespread diseases.

A retrospective evaluation of 193 patients with oral lichen planus

One hundred and ninety-three patients with oral lichen planus were evaluated retrospectively. Women outnumbered men by more than two to one. The mean age at lesion discovery was in the sixth decade. The buccal mucosa was the most common site of occurrence. There were concomitant systemic diseases in many of the patients. The ulcerative form was the most prevalent referred form. Therapies included observation and treatment with topical and systemic corticosteroids with and without anti-fungals and immunosuppressants. Areas of discussion include lesion location, chronicity, therapeutic modalities, malignant transformation, age, gender, symptomatology and systemic disease.

Immediate biopsy versus a therapeutic trial in the diagnosis and treatment of vesiculobullous/vesiculoerosive oral lesions. Opposing viewpoints presented

There are at least two treatment strategies in the diagnosis and treatment of oral vesiculobullous/vesiculoerosive disease. The relative merits of immediate biopsy and initial therapeutic trial regimens are debated.

Environmental causes of cancer

The development of cancer in an individual is the result of multiple genetic and epigenetic steps. Carcinogens and tumor promoters can act by a variety of molecular mechanisms, and repeated exposure to numerous agents is frequently necessary for the formation of cancer. The estimate of cancer risk in a population is performed via a formal quantitative risk assessment. The estimated risk in an individual is more complex because of both inherited predispositions and lifestyle. Although information is available, it is essential to understand the goals, attributes, and limitations of the experimental methods underlying our current understanding of the environmental causes of cancer.

Acute effects of a superoxide radical-generating system on DNA double-strand stability in Chinese hamster ovary cells. Determination by a modified fluorometric procedure

The rate of oxyradical generation by a xanthine oxidase-xanthine system to acutely cause DNA strand breakage in Chinese hamster ovary cells was studied in a phosphate-buffered saline system. DNA strand breakage, measured by a fluorometric procedure, was found to increase curvilinearly as a function of oxyradical generation. Results of studying the ability of 5 mM mannitol, 10 mM dimethylthiourea, 300 micrograms superoxide dismutase/ml, or 1 mg catalase/ml to interfere with DNA damage at a high rate of oxyradical production best supported a hydrogen peroxide-promoted mechanism for DNA breakage.

Immune suppression at high altitude

This paper is a review and interpretation of prior studies that have investigated the effects of hypoxia on immune function. A summary of current methods used to assess immune effector cell function in human beings is presented using in vitro models of mononuclear cell activation. Animal studies indicate that impaired host defenses against bacterial pathogens may be compromised, but that resistance to virus infections may remain intact. Data from human studies and animal models indicate that active immunization and B cell function are unimpaired, whereas T cell function is blunted following exposure to hypoxia. Mechanisms that may be responsible for alterations in normal immunoregulation are presented. The implications of altered immune function in subjects exposed to high altitude are discussed.