Autopathogenic T helper cell type 1 (Th1) and protective Th2 clones differ in their recognition of the autoantigenic peptide of myelin proteolipid protein

We previously generated a panel of T helper cell 1 (Th1) clones specific for an encephalitogenic peptide of myelin proteolipid protein (PLP) peptide 139-151 (HSLGKWLGHPDKF) that induces experimental autoimmune encephalomyelitis (EAE) upon adoptive transfer. In spite of the differences in their T cell receptor (TCR) gene usage, all these Th1 clones required W144 as the primary and most critical TCR contact residue for the activation. In this study, we determined the TCR contact residues of a panel of Th2/Th0 clones specific for the PLP peptide 139-151 generated either by immunization with the PLP 139-151 peptide with anti-B7-1 antibody or by immunization with an altered peptide Q144. Using alanine-substituted peptide analogues of the native PLP peptide, we show that the Th2 clones have shifted their primary contact residue to the NH2-terminal end of the peptide. These Th2 cells do not show any dependence on the W144, but show a critical requirement for L141/G142 as their major TCR contact residue. Thus, in contrast with the Th1 clones that did not proliferate to A144-substituted peptide, the Th2 clones tolerated a substitution at position 144 and proliferated to A144 peptide. This alternative A144 reactive repertoire appears to have a critical role in the regulation of autoimmune response to PLP 139-151 because preimmunization with A144 to expand the L141/G142-reactive repertoire protects mice from developing EAE induced with the native PLP 139-151 peptide. These data suggest that a balance between two different T cell repertoires specific for same autoantigenic epitope can determine disease phenotype, i.e., resistance or susceptibility to an autoimmune disease.

Molecular and cellular biology of pre-malignancy in the gastrointestinal tract

Important pathogenic alterations within established cancers are acquired during the premalignant stage. These genetic alterations can be grouped into specific neoplastic pathways that differ within and between anatomical sites. By understanding the mechanisms that determine the initiation and progression of each pathway, it will be possible to develop novel approaches to the diagnosis, prevention and treatment of cancer. This chapter outlines the principles underlying the molecular characterization of pre-malignant lesions, taking colorectal neoplasia as the main model.

Altered mucin expression in the gastrointestinal tract: a review

Early studies of changes in mucin expression in disorders of the gastrointestinal tract focused on alterations in the carbohydrate chain. This review briefly considers the various mechanisms by which such alterations may come about: (a) normal variation, (b) sialic acid alterations, (c) defective assembly of carbohydrate side-chains, (d) changed expression of core proteins and (e) epithelial metaplasia. The availability of monoclonal antibodies to mucin core proteins adds a new dimension to mucin histochemistry. It is now possible to offer explanations for traditional mucin histochemical findings on the basis of lineage-specific patterns of mucin core protein expression. Changes in core protein expression are described in inflammatory, metaplastic and neoplastic disorders of the gastrointestinal tract. The possibility that mucin change could be important in the aetiology of some diseases such as ulcerative colitis and H. pylori gastritis is considered. It is more probable, however, that changes in mucin expression are secondary to reprogramming of cellular differentiation and altered cell turnover. As such they may serve as markers to explain pathogenesis and provide novel diagnostic and prognostic information.

Timely topic: Premalignant lesions associated with adenocarcinoma of the upper gastrointestinal tract

The changing incidence of adenocarcinomas, particularly in the oesophagus and gastric cardia, has led to the rapid expansion of screening programmes aimed at detecting the precursor lesion of dysplasia before adenocarcinoma develops. The pathologist now has an important role in first diagnosing patients at risk for developing dysplasia, and then correctly classifying dysplasia when it occurs. Barrett's oesophagus has had different diagnostic criteria in previous years but is currently diagnosed by the presence of intestinal metaplasia of any length in the true oesophagus. Intestinal metaplasia confined only to the gastro-oesophageal junction or cardia is of uncertain significance but is probably common, with less risk of progressing to dysplasia or malignancy. In the stomach, patients with autoimmune atrophic gastritis and Helicobacter-associated multifocal atrophic gastritis have an increased risk of adenocarcinoma, but screening protocols are not well-developed compared with those used for Barrett's oesophagus. Dysplasia of glandular epithelium can be classified using well-described criteria. Low grade dysplasia is the most common type and regresses or remains stable in the majority of patients. High grade dysplasia is more ominous clinically, with a propensity to coexist with or progress to adenocarcinoma.

Gastrointestinal worm infections. The prevalence and treatment in Australia

BACKGROUND:Intestinal worm (helminth) infections occur in a large proportion of the world's population, often constituting public health problems, and are occasionally encountered by practitioners in urban Australia. Prevalence levels in some remote Australian Aboriginal communities compare with those in developing countries. OBJECTIVE: To provide general practitioners with a brief outline of the most common human intestinal helminthiases, their usual clinical presentations and how they are diagnosed and managed. DISCUSSION: The pinworm, Enteroblus vermicularis, occurs in all populations, and is the most common species of nematode encountered in suburbia. Eradication is impossible, but its numbers can be kept low in those children who seem predisposed to heavy, symptomatic infections. The other nematodes are prevalent in some remote Australian Aboriginal communities, and are encountered occasionally in travellers from overseas. These infections are often asymptomatic, they cannot spread directly to other people and so do not pose any public health threat to the general community under suburban living conditions. The tapeworms are encountered even less frequently, except for Hymenolepis, the dwarf tapeworm, which is prevalent in some Aboriginal communities.

Further studies on an intermediate host murine model showing that a primary Echinococcus granulosus infection is protective against subsequent oncospheral challenge

We describe the use of a murine model to evaluate resistance against subsequent challenge following a primary infection with oncospheres of Echinococcus granulosus. Mice (Kunming strain) were infected with hatched oncospheres of Echinococcus granulosus; 21 days later a second challenge was given by a different route of infection. A primary infection by intraperitoneal (i.p.) injection stimulated 100 and 90.5% protection in terms of reduced cyst numbers against a secondary infection given subcutaneously (s.c.) or intravenously (i.v.) respectively. A primary infection given s.c. followed by i.p. or i.v. challenge resulted in 84.0 and 100% protection, respectively. Intravenous infection followed by i.p. or s.c. challenge resulted in 98.5 and 69.4% protection, respectively. With the i.v. route of infection, almost all resultant cysts were present in the lungs. The data show that a primary infection with oncospheres can induce total or a high degree of protection against a subsequent challenge and confirms that natural (concomitant) immunity can be stimulated in the intermediate host as the result of a primary infection. This may explain the decline in hydatid infection in sheep older than 2 years in hyper-endemic areas such as those found in Xingjiang, China. These older sheep may have been earlier infected and have subsequently self-cured, with the primary infection stimulating an immune response that protects the intermediate host animals from further infection. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.

Recent dioxin contamination from Agent Orange in residents of a southern Vietnam city

Marked elevation of dioxin associated with the herbicide Agent Orange was recently found in 19 of 20 blood samples from persons living in Bien Hoa, a large city in southern Vietnam. This city is located near an air base that was used for Agent Orange spray missions between 1962 and 1970. A spill of Agent Orange occurred at this air base more than 30 years before blood samples were collected in 1999. Samples were collected, frozen, and sent to a World Health Organization-certified dioxin laboratory fm congener-specific analysis as part of a Vietnam Red Cross project. Previous analyses of more than 2200 pooled blood samples collected in the 1990s identified Bien Hoa as one of several southern Vietnam areas with persons having elevated blood dioxin levels from exposure to Agent Orange. In sharp contrast to this study, our previous research showed decreasing tissue dioxin levels over time since 1970. Only the dioxin that contaminated Agent Orange, 2,3, 7, 8-tetrachlmodibenzo-p-dioxin (TCDD), was elevated in the blood of 19 of 20 persons sampled from Bien Hoa. A comparison pooled sample from 100 residents of Hanoi, where Agent Orange was not used, measured blood TCDD levels of 2 parts per trillion (ppt). TCDD levels of up to 271 ppt, a 135-fold increase, were found in Bien Hoa residents. TCDD contamination was also found in some nearby soil and sediment samples. Persons new to this region and children born after Agent Orange spraying ended also had elevated TCDD levels. This TCDD uptake was recent and occurred decades after spraying ended. We hypothesize that a major route of current and past exposures is from the movement of dioxin from soil into river sediment, then into fish, and from fish consumption into people.

Development of disabled, replication-defective gene transfer vectors from the Jembrana disease virus, a new infectious agent of cattle

Jembrana disease virus (JDV) is a newly isolated and characterised bovine lentivirus. It causes an acute disease in Ball cattle (Bos javanicus). which can be readily transmitted to susceptible cattle with 17% mortality. There is as yet no treatment or preventive vaccine. We have developed a gene transfer vector system based on JDV that has three components. The first of the components is a bicistronic transfer vector plasmid that was constructed to contain cis-sequences from the JDV genome, including 5 '- and 3 ' -long terminal repeats (LTRs), 0.4 kb of truncated gag and 1.1 kb of 3 ' -env, a multiple cloning site to accommodate the gene(s) of interest for transfer, and an internal ribosome entry site plus the neomycin phosphotransferase (Neo) gene cassette for antibiotic selection. The second element is a packaging plasmid that contains trans-sequences. including gag, pol. vif, tar and rev: but without the env and packaging signals. The third is a plasmid encoding the G glycoprotein of vesicular stomatitis virus (VSV-G) to supply the vector an envelope for pseudotyping. Cotransfection of 293T cells with these three plasmid components produced VSV-G pseudotyped. disabled, replication defective, bicistronic JDV vectors encoding the green fluorescent protein (EGFP) and the Neo resistance selection maker simultaneously with a titre range of (0.4-1.2) x 10(6) CFU/ml. Transduction of several replicating primary and transformed cells from cattle, primate and human sources and importantly growth-arrested cells with the JDV vectors showed high efficiency of EGFP gene transfer at 35-75%, which was stable and the expression of EGFP was long term. Furthermore, these JDV vectors were designed to suit the inclusion and expression of genes corresponding to JDV specific proteins, such as gag or env, for the development of vaccines for Jembrana disease. This strategy should also be applicable to other bovine diseases as wall. The design and construction of the JDV vector system should facilitate the study of the lentivirology and pathogenesis of the diseases associated with JDV or other bovine virus infections. To our knowledge, this is the first such vector system developed from a cattle virus. (C) 2001 Elsevier Science B.V. All rights reserved.

Cloning and gastrointestinal expression of rat hephaestin: relationship to other iron transport proteins

The membrane-bound ceruloplasmin homolog hephaestin plays a critical role in intestinal iron absorption. The aims of this study were to clone the rat hephaestin gene and to examine its expression in the gastrointestinal tract in relation to other genes encoding iron transport proteins. The rat hephaestin gene was isolated from intestinal mRNA and was found to encode a protein 96% identical to mouse hephaestin. Analysis by ribonuclease protection assay and Western blotting showed that hephaestin was expressed at high levels throughout the small intestine and colon. Immunofluorescence localized the hephaestin protein to the mature villus enterocytes with little or no expression in the crypts. Variations in iron status had a small but nonsignificant effect on hephaestin expression in the duodenum. The high sequence conservation between rat and mouse hephaestin is consistent with this protein playing a central role in intestinal iron absorption, although its precise function remains to be determined.

Effects of gall damage by the introduced biocontrol agent Epiblema strenuana (Lep., Tortricidae) on the weed Parthenium hysterophorus (Asteraceae)

Effects of gall damage by the introduced moth Epiblema stremiana on different growth stages of the weed Parathenium hysterophorus was evaluated in a field cage using potted plants with no competition and in naturally regenerated populations with intraspecific competition. Gall damage at early stages of plant growth reduced the plant height, main stem height, flower production, lear production, and shoot and root biomass. All galled, potted plants with no competition produced flowers irrespective of the growth stage at which the plants were affected by galling, but lesser than in ungalled plants. Gall induction during early growth stages in field plants experiencing competition prevented 30% of the plants reaching flowering. However, 6% of the field plants escaped from gall damage, as their main stems were less vigorous to sustain the development of galls. Flower production per unit total plant biomass was lower in galled plants than in ungalled plants, and the reduction was more intense when gall damage was initiated at early stages of plant growth. In potted plants with no competition, the number of galls increased with the plant vigour, as the gall insects preferred more vigorous plants. But in field plants there were no relationship between gall abundance and plant vigour, as intraspecific competition enhanced the negative effects of galling by reducing the vigour of the weed.

Delayed emergence of bovine leukemia virus after vaccination with a protective cytotoxic T cell-based vaccine

In a previous study eight MHC class I-matched sheep were vaccinated with a minimal cytotoxic T lymphocyte (CTL) peptide epitope vaccine and were challenged with the retrovirus, bovine leukemia virus (BLV). Half the vaccinated animals remained PCR negative after challenge, whereas the remaining half and the placebo group became PCR positive within 4 weeks postchallenge (Hislop AD, Good MF, Mateo L, Gardner J, Gatei MH, Daniel RCW, Meyers BV, Lavin MF, and Suhrbier A: Nat Med 1998; 4: 1193). Here we show that neither epitope mutations nor processing differences explained why half the peptide-vaccinated animals failed to resist the BLV challenge. However, in these animals the development of BLV-induced lymphosarcomas was significantly delayed compared with the placebo group, suggesting a role for CTLs in preventing retrovirus-induced cancers. Importantly, two of the initially protected animals become PCR positive after similar to1.5 years, indicating extended suppression but not elimination of challenge virus by vaccine-induced CTLs. The late emergence of virus could not be explained by epitope escape mutations or the loss of memory CTL responses. We speculate that high levels of effector CTL may be needed to protect animals from a postchallenge viremia and maintenance of such effector CTLs, rather than memory CTLs, may be required to prevent subsequent emergence of virus from latent pools.

Immune responses in hookworm infections

Hookworms infect perhaps one-fifth of the entire human population, yet little is known about their interaction with our immune system. The two major species are Necator americanus, which is adapted to tropical conditions, and Ancylostoma duodenale, which predominates in more temperate zones. While having many common features, they also differ in several key aspects of their biology. Host immune responses are triggered by larval invasion of the skin, larval migration through the circulation and lungs, and worm establishment in the intestine, where adult worms feed on blood and mucosa while injecting various molecules that facilitate feeding and modulate host protective responses. Despite repeated exposure, protective immunity does not seem to develop in humans, so that infections occur in all age groups (depending on exposure patterns) and tend to be prolonged. Responses to both larval and adult worms have a characteristic T-helper type 2 profile, with activated mast cells in the gut mucosa, elevated levels of circulating immunoglobulin E, and eosinoophilia in the peripheral blood and local tissues, features also characteristic of type I hypersensitivity reactions. The longevity of adult hookworms is determined probably more by parasite genetics than by host immunity. However, many of the proteins released by the parasites seem to have immunomodulatory activity, presumably for self-protection. Advances in molecular biotechnology enable the identification and characterization of increasing numbers of these parasite molecules and should enhance our detailed understanding of the protective and pathogenetic mechanisms in hookworm infections.

Drug targets and mechanisms of resistance in the anaerobic protozoa

The anaerobic protozoa Giardia duodenalis, Trichomonas vaginalis, and Entamoeba histolytica infect up to a billion people each year. G. duodenalis and E. histolytica are primarily pathogens of the intestinal tract, although E. histolytica can form abscesses and invade other organs, where it can be fatal if left untreated. T. vaginalis infection is a sexually transmitted infection causing vaginitis and acute inflammatory disease of the genital mucosa. T. vaginalis has also been reported in the urinary tract fallopian tubes, and pelvis and can cause pneumonia, bronchitis, and oral lesions. Respiratory infections can be acquired perinatally. T. vaginalis infections have been associated with preterm delivery, low birth weight, and increased mortality as well as predisposing to human immunodeficiency virus infection, AIDS, and cervical cancer. All three organisms lack mitochondria and are susceptible to the nitroimidazole metronidazole because of similar low-redox-potential anaerobic metabolic pathways. Resistance to metronidazole and other drugs has been observed clinically and in the laboratory. Laboratory studies have identified the enzyme that activates metronidazole, pyruvate:ferredoxin oxidoreductase, to its nitroso form and distinct mechanisms of decreasing drug susceptibility that are induced in each organism. Although the nitroimidazoles have been the drug family of choice for treating the anaerobic protozoa, G. duodenalis is less susceptible to other antiparasitic drugs, such as furazolidone, albendazole, and quinacrine. Resistance has been demonstrated for each agent and the mechanism of resistance has been investigated. Metronidazole resistance in T. vaginalis is well documented, and the principal mechanisms have been defined Bypass metabolism, such as alternative oxidoreductases, have been discovered in both organisms. Aerobic versus anaerobic resistance in T. vaginalis is discussed. Mechanisms of metronidazole resistance in E. histolytica have recently been investigated ruing laboratory-induced resistant isolates. Instead of downregulation of the pyruvate:ferredoxin oxidoreductase and ferredoxin pathway as seen in G. duodenalis and T. vaginalis, E. histolytica induces oxidative stress mechanisms, including superoxide dismutase and peroxiredoxin. The review examines the value of investigating both clinical and laboratory-induced syngeneic drug-resistant isolates and dissection of the complementary data obtained. Comparison of resistance mechanisms in anaerobic bacteria and the parasitic protozoa is discussed as well as the value of studies of the epidemiology of resistance.

A spongin-boring alpha-proteobacterium is the etiological agent of disease in the Great Barrier Reef sponge Rhopaloeides odorabile

High levels of mortality in the Mediterranean bath sponge industry have raised concerns for the future of sponge farms. Healthy sponges feed predominantly on bacteria, and many harbour a wide diversity of inter- and extra-cellular symbiotic bacteria. Here we describe the first isolation and description of a pathogenic bacterium from an infected marine sponge. Microbiological examination of tissue necrosis in the Great Barrier Reef sponge Rhopaloeides odorabile resulted in isolation of the bacterial strain NW4327. Sponges infected with strain NW4327 exhibited high levels of external tissue necrosis, and the strain was re-isolated from infected sponges. A single morphotype, which had burrowed through the collagenous spongin fibres causing severe necrosis, was observed microscopically. Strain NW4327 was capable of degrading commercial preparations of azo-collagen, providing further evidence of its involvement in spongin fibre necrosis, Strain NW4327 disrupted the microbial community associated with R. odorabile and was able to infect and kill healthy sponge tissue. 16S rRNA sequence analysis revealed that strain NW4327 is a novel member of the alpha-proteobacteria.