A literature review of different pressure ulcer models from 1942-2005 and the development of an ideal animal model

The literature from 1942-2005 was reviewed in order to determine an inexpensive animal model which can closely mimic pressure ulcers seen in humans of varying ages, without the need for surgical procedures. Two animal models for producing pressure ulcers were found to be inexpensive: pigs to mimic pressure ulcers in young humans due to their fixed skin, and rats to mimic pressure ulcers in the elderly due to their loose skin. The methods which were found to be inexpensive, reproducible, non-invasive and easy to carry out without the need of a surgeon or specialist were the use of magnets for rat models and the use of a cast placed over a bony prominence for pig models.

Differentiation of sympatric populations of the band-rumped storm-petrel in the Galapagos Islands: an examination of genetics, morphology, and vocalizations

In each of at least two locations within the Galapagos Islands, breeding band-rumped storm-petrels (Oceanodroma castro) form two distinct populations that use the same colony site at separate times of the year for reproduction. Temporal segregation of these populations raises the possibility that they are reproductively isolated and represent cryptic species. We examined variation in mitochondrial DNA, morphology, and vocalizations of storm-petrel populations nesting 6 months apart on the islet of Plaza Norte in the Galapagos. Seasonal populations displayed low but significant levels of differentiation in the mitochondrial control region, five morphological variables, and one feature of male vocalizations. Breeding populations appear to have been separated for approximately 1700 years. Given the recent divergence date and relatively high effective population sizes (4000-5600 females each), seasonal populations are unlikely to be in genetic equilibrium. As a result, the low divergence estimate probably reflects historical association and not contemporary genetic exchange. These populations are not sufficiently differentiated to be considered cryptic species. However, they are probably in the early stages of divergence. Consequently, we recommend that cool- and hot season populations on Plaza Norte be recognized as separate management units.

Cross-reactive cellular and humoral immune responses to Salmonella enterica serovars Typhimurium and Enteritidis are associated with protection to heterologous re-challenge

Chickens infected with Salmonella enterica serovars Typhimurium (ST) and Enteritidis (SE) still represent a major source of human food poisoning via consumption of contaminated meat and eggs. Vaccination represents a sustainable approach to control Salmonella in the chicken and the serovar specificity of immunity has the potential to impact on the need for multivalent vaccines. The issue of cross-reactive immune responses and cross-serovar protection was examined in these experiments. Cellular and humoral immune responses were measured by antigen-specific ELISA and splenocyte proliferation assays during primary infections (with ST and SE) and during a second challenge with homologous or heterologous serovars. Primary infection with ST or SE induced strong lymphocyte proliferation and high levels of specific antibody (IgM, IgG and IgA) responses with substantial serovar cross-reactivity. The occurrence of high levels of splenocyte proliferation and strong antibody responses corresponded to the initiation of clearance with both ST and SE. Re-challenge of ST and SE infection-primed chickens with either serovar resulted in significant levels of protection (assessed by bacterial numbers and rate of clearance) with little difference between homologous or heterologous challenge schedules. Relatively low levels of antigen-specific splenocyte proliferation were detected during secondary infection, which may be caused by splenic T cells exiting to the gut. In contrast, the more rapid specific antibody responses (compared with primary infection controls) indicate the development of a secondary antigen-specific adaptive response. The substantial level of cross-protection between serovars and the level of antigenic cross-reactivity indicates the potential for single serovar live vaccines to protect against both group B and D salmonellae.

Mouse allergen-specific immunoglobulin G4 and risk of mouse skin test sensitivity

BACKGROUND

High serum levels of cat-specific IgG and IgG4 are associated with protection against allergic sensitization to cat, but whether this association applies to other animal allergens remains unclear.

OBJECTIVE

To determine if high levels of mouse-specific IgG and IgG4 are associated with a decreased risk of mouse skin test sensitivity.

METHODS

Two hundred and sixty workers of a mouse facility underwent skin prick testing and completed a questionnaire. Serum levels of mouse-specific IgG and IgG4 were quantified by solid-phase antigen binding assays. Room air samples were collected and airborne Mus m 1 was quantified by ELISA.

RESULTS

Forty-nine participants had a positive skin prick test to mouse. Mouse-specific IgG was detected in 219 (84%) participants and IgG4 was detected in 72 (28%) participants. A detectable mouse-specific IgG4 level was associated with an increased risk of mouse skin test sensitivity (odds ratios (OR) 6.4, 95% confidence intervals (CI) 3.3-12.4). Mouse-specific IgG and IgG4 were both positively correlated with mouse allergen exposure (r(s)=0.31, P=0.0001, and r(s)=0.27, P=0.0006, respectively). The odds of skin test sensitivity peaked at moderate levels of IgG4, but decreased at the highest levels of mouse-specific IgG4. In contrast, the odds of skin test sensitivity increased monotonically with IgG levels.

CONCLUSIONS

A detectable level of mouse-specific IgG4 is associated with an increased risk of skin test sensitivity to mouse. However, the highest IgG4 levels appear to be associated with an attenuated risk of mouse skin test sensitivity, suggesting that induction of high levels of IgG4 through natural exposure may protect against the development of allergic sensitization.

Genetic identification of antigens protective against coccidia

The Eimeria species, causative agents of the disease coccidiosis, are genetically complex protozoan parasites endemic in livestock. Drug resistance remains commonplace among the Eimeria, and alternatives to chemotherapeutic control are being sought. Vaccines based upon live formulations of parasites are effective, but production costs are high, stimulating demand for a recombinant subunit vaccine. The identity of antigens suitable for inclusion in such vaccines remains elusive. Selection of immunoprotective antigens of the Eimeria species as vaccine candidates based upon recognition by the host immune system has been unsuccessful, obscured by the considerable number of molecules that are immunogenic but not immunoprotective. This is a common problem which characterizes work with most eukaryotic parasites. The identification of a selective criterion to directly access genetic loci that encode immunoprotective antigens of Eimeria maxima using a mapping strategy based upon parasite genetics, immune selection and DNA fingerprinting promises to revolutionize the process of antigen discovery. Linkage analyses of DNA markers amplified from populations of recombinant parasites defined by an ability to escape parent-specific deleterious selection by strain-specific immunity and chemotherapy has revealed four discrete regions within the E. maxima genome linked to escape from a protective immune response. These regions now form the basis of detailed study to identify antigens as candidates for inclusion in future vaccination strategies.

Mouse allergen-specific immunoglobulin G and immunoglobulin G4 and allergic symptoms in immunoglobulin E-sensitized laboratory animal workers

BACKGROUND

High levels of allergen-specific IgG have been associated with clinical efficacy in immunotherapy studies, but whether this antibody isotype is associated with clinical tolerance in the setting of environmental exposure remains unclear.

OBJECTIVE

To determine if mouse allergen-specific IgG (mIgG) and IgG4 (mIgG4) levels are associated with mouse-related symptoms among IgE-sensitized laboratory workers.

METHODS

Fifty-eight workers with either skin test or serologic evidence of IgE-mediated mouse sensitization were studied. Symptom data were obtained by a questionnaire. Serum levels of mouse-specific IgG, IgG4, and IgE were quantified by a solid-phase antigen-binding assay (IgG) and RAST (IgG4 and IgE), and the relationships between mouse-specific serologic responses and mouse-related symptoms were analysed.

RESULTS

Twenty-three (39.7%) participants reported mouse-related symptoms. Mouse-specific IgG and IgG4 levels were not associated with mouse-related symptoms among the study population as a whole. Among the 29 (50%) participants with detectable mouse-specific IgE (mIgE), higher mouse-specific IgG and IgG4 levels were associated with a decreased risk of symptoms, after adjusting for mIgE level (odds ratio (OR) 0.3, 95% confidence interval (CI): 0.1-1.4, and OR 0.3, 95% CI: 0.04-2.6, respectively). Higher levels of mIgG and mIgG4 remained associated with a decreased risk of symptoms after additional adjustment for sex and handling of mice (OR 0.1, 95% CI: 0.02-0.7, and OR 0.2, 95% CI: 0.02-2.1, respectively). Higher mIgG : IgE and mIgG4 : IgE ratios were also associated with a decreased risk of symptoms after adjusting for these confounders (OR 0.1, 95% CI: 0.02-0.7, and OR 0.2, 95% CI: 0.02-0.92, respectively).

CONCLUSION

Among workers with detectable mIgE, higher mIgG and mIgG4 levels are associated with a decreased risk of mouse-related symptoms. High serum levels of mIgG or mIgG4 may be markers for clinical tolerance among laboratory mouse workers with detectable mIgE, but these findings need to be confirmed in larger, prospective studies.

Mild one-pot preparation of glycosyl bromides

Mild one-pot protocols for the preparation of glycosyl bromides and alkyl bromides via in situ generation of HBr is reported here.

Integrating genetics and genomics to identify new leads for the control ofEimeriaspp

Eimerian parasites display a biologically interesting range of phenotypic variation. In addition to a wide spectrum of drug-resistance phenotypes that are expressed similarly by many other parasites, theEimeriaspp. present some unique phenotypes. For example, unique lines ofEimeriaspp. include those selected for growth in the chorioallantoic membrane of the embryonating hens egg or for faster growth (precocious development) in the mature host. The many laboratory-derived egg-adapted or precocious lines also share a phenotype of a marked attenuation of virulence, the basis of which is different as a consequence of thein ovoorin vivoselection procedures used. Of current interest is the fact that some wild-type populations ofEimeria maximaare characterized by an ability to induce protective immunity that is strain-specific. The molecular basis of phenotypes that defineEimeriaspp. is now increasingly amenable to investigation, both through technical improvements in genetic linkage studies and the availability of a comprehensive genome sequence for the caecal parasiteE. tenella. The most exciting phenotype in the context of vaccination and the development of new vaccines is the trait of strain-specific immunity associated withE. maxima. Recent work in this laboratory has shown that infection of two inbred lines of White Leghorn chickens with the W strain ofE. maximaleads to complete protection to challenge with the homologous parasite, but to complete escape of the heterologous H strain, i.e. the W strain induces an exquisitely strain-specific protective immune response with respect to the H strain. This dichotomy of survival in the face of immune-mediated killing has been examined further and, notably, mating between a drug-resistant W strain and a drug-sensitive H strain leads to recombination between the genetic loci responsible for the specificity of protective immunity and resistance to the anticoccidial drug robenidine. Such a finding opens the way forward for genetic mapping of the loci responsible for the induction of protective immunity and integration with the genome sequencing efforts.

QCM/HCC as a platform for detecting the binding of warfarin to an immobilized film of human serum albumin

Quartz crystal microbalance/heat conduction calorimetry (QCM/HCC) is a new measurement technology that has been used to monitor simultaneously the mass and motional resistance of a thin film in conjunction with the heat flow produced by a chemical change in the film initiated by reaction with a gas. In this work we examine the applicability of the QCM/HCC in detecting chemical changes at the solution/thin film interface. Human serum albumin (HSA) was bound to the gold electrode of a 5 MHz AT-cut quartz resonator using three types of linkers and then exposed to buffered solutions of the anticoagulant drug warfarin. Changes in resonator frequency and motional resistance as well as changes in heat flow produced by warfarin binding to HSA were monitored as a function of the warfarin concentration. Differences in frequency and motional resistance changes depend upon the linker and vary both in magnitude and sign, whereas the integrated heat signal is proportional to the concentration of warfarin and independent of the linker chemistry. Quartz crystal microbalance/heat conduction calorimetry can thus be a useful tool for studying protein-ligand interactions at the solution-surface interface, even though the quartz resonator does not behave as a microbalance.

Age at primary infection with Salmonella enterica serovar Typhimurium in the chicken influences persistence of infection and subsequent immunity to re-challenge

Salmonella enterica remains one of the most important food-borne pathogens of humans and is often acquired through consumption of infected poultry meat or eggs. Control of Salmonella infections in chicken is therefore an important public health issue. Infection with S. enterica serovar Typhimurium results in a persistent enteric infection without clinical disease in chickens of more than 3 days of age, and represents a source for contamination of carcass at slaughter and entry into the human food chain. Data presented indicate a profound effect of age at initial exposure on the persistence of infection and a lesser effect on the development of effective immunity to re-challenge. The percentage of birds positive for Salmonella was high until 8-9 weeks of age, regardless of the age at which the birds were infected (1, 3 or 6 weeks). The birds infected at 3 and 6 weeks of age produced a more rapid and higher antibody response (IgY and IgA) than those infected at 1 week of age, but in all cases infection persisted for a considerable period despite the presence of high antibody levels. Following a re-challenge infection with S. Typhimurium, all three previously-infected groups had fewer bacteria in the gut, spleen and liver compared with age-matched birds receiving a parallel primary infection. However, the birds primary infected at 3 and 6 weeks of age cleared infection more rapidly than those infected at a younger age. Interestingly older-primed birds had higher specific T lymphocyte proliferative responses and specific circulating levels of IgY antibody at time of re-challenge. Although birds initially infected at 1 week of age and those that were previously uninfected produced a stronger antibody response following re-challenge, they were slower to clear Salmonella from the gut than the older-primed groups which expressed a stronger T lymphocyte response. The data presented indicate that clearance of Salmonella from the gut is age-dependent and we propose that this relates to the increased competence of the enteric T cell response. The findings that Salmonella persists beyond 8-9 weeks, irrespective of age at exposure, has implications for the broiler sector and indicates the need to remain Salmonella free throughout the rearing period. Moreover, the re-challenge data demonstrates that infection at a young age is less effective in producing protective immunity than in older chickens. This feature of the development of protective immunity needs to be considered when developing vaccines for the broiler sector of the poultry industry.

Persistent Seoul virus infection in Lewis rats

Mechanistic studies of hantavirus persistence in rodent reservoirs have been limited by the lack of a versatile animal model. This report describes findings from experimental infection of inbred Lewis rats with Seoul virus strain 80-39. Rats inoculated with virus intraperitoneally at 6 days of age became persistently infected without clinical signs. Tissues from Seoul virus-inoculated 6-day-old rats were assessed at 6, 9, and 12 weeks post-inoculation for viral RNA by RT-PCR and in situ hybridization (ISH) and for infectious virus by inoculation of Vero E6 cells. Virus was isolated from lung and kidney of infected rats at 6 weeks and viral RNA was detected in lung, kidney, pancreas, salivary gland, brain, spleen, liver and skin at 6, 9 and 12 weeks. Rats inoculated with Seoul virus intraperitoneally at 10 or 21 days of age became infected without clinical signs but had low to undetectable levels of viral RNA in tissues at 6 weeks post-inoculation. ISH identified vascular smooth muscle and endothelial cells as common sites of persistent infection. Cultured rat smooth muscle cells and to a lesser extent cultured endothelial cells also were susceptible to Seoul virus infection. Pancreatic infection resulted in insulitis with associated hyperglycemia. These studies demonstrate that infant Lewis rats are uniformly susceptible to asymptomatic persistent Seoul virus infection. Additionally, they offer opportunities for correlative in vivo and in vitro study of Seoul virus interactions in host cell types that support persistent infection.

Temporal dynamics of the cellular, humoral and cytokine responses in chickens during primary and secondary infection withSalmonella entericaserovar Typhimurium

Salmonella enterica serovar Typhimurium (S. Typhimurium) infections cause systemic disease in the young chick, whereas in the older chicken the infection is mainly restricted to the intestine. Chickens infected orally with S. Typhimurium (F98) at 6 weeks of age and re-infected 10 weeks later were monitored for antibody production, T-cell proliferation and production of selected cytokines (interferon-gamma, interleukin-1beta and transforming growth factor-beta(4)). A strong coordinated antigen-specific humoral and cellular immune response was temporally linked to resolution of the primary infection. Enhanced levels of mRNA encoding the cytokines, interleukin-1beta, transforming growth factor-beta(4) and interferon-gamma were also evident during early phases of primary infection. Secondary infection was restricted to the intestine and of shorter duration than primary infection. Splenic immune responses were not further enhanced by secondary infection; indeed, antigen-specific proliferation was significantly reduced at 1 day after secondary infection, which may be interpreted as the trafficking of reactive T cells from the spleen to the gut.

Amplified fragment length polymorphism analyses of Eimeria spp.: an improved process for genetic studies of recombinant parasites

Application of the amplified fragment length polymorphism (AFLP) technique to genetic mapping studies requires high quality DNA as a template. In the case of Eimeria spp., this has previously been in the form of chromosomal DNA obtained from purified sporozoites recovered from large numbers of oocysts (generally up to 2 x 10(8)). In order for the AFLP technique to be more easily applied to studies on the genetics of Eimeria maxima, for which only smaller numbers of oocysts are available, a simplified, more efficient method for the recovery of genomic DNA from small numbers of oocysts was developed. Our new method should also be useful for genetic analyses of other coccidial parasites and for the recovery of AFLP-quality DNA from other pathogens.

Chloramphenicol succinate kinetics in infants and young children

We sought to estimate the serum and urine pharmacokinetics of chloramphenicol succinate (CmS) and the effects of variation of these parameters on chloramphenicol (Cm) kinetics in 24 infants and young children ages two weeks to seven years. The mean T(1/2) of CmS was 0.40 hours; the mean body clearance was 0.72 liter/KG/hour; the mean apparent volume of distribution was 0.42 liter/kg. Variation in CmS T(1/2) did not correlate with significant variation in Cm T(1/2) (r2 = 0.002, P = 0.84). Urine collected during the dosing interval in nine patients contained 35% (mean) of the administered dose. Adjusting the infusion duration to 5 minutes or 120 minutes had no effect on the amount of CmS lost in the urine. The quantity of CmS lost in the urine affects the amount bioavailable, and secondarily the calculated volume of distribution and body clearance of Cm. We conclude that variation in urinary prodrug excretion affects the amount of Cm bioavailable to the patient, but variation in CmS T(1/2) has little effect on Cm T(1/2).

Ecological basis for fertility control in the house mouse (Mus domesticus) using immunocontraceptive vaccines

Laboratory studies confirm the potential for fertility control in the house mouse Mus domesticus using mouse cytomegalovirus (MCMV) as a vector for an immunocontraceptive vaccine. This article presents an overview of key results from research in Australia on enclosed and field populations of mice and the associated epidemiology of MCMV. The virus is geographically widespread in Australia. It also persists in low population densities of mice, although if population densities are low for at least a year, transmission of the virus is sporadic until a population threshold of approximately 40 mice ha(-1) is reached. The serological prevalence of MCMV was high early in the breeding season of four field populations. Enclosure studies confirm that MCMV has minimal impact on the survival and breeding performance of mice and that it can be transmitted to most adults within 10-12 weeks. Other enclosure studies indicate that about two-thirds of females would need to be sterilized to provide effective control of the rate of growth of mouse populations. If this level is not maintained for 20-25 weeks after the commencement of breeding, the mouse population can compensate through increased recruitment per breeding female. The findings from this series of descriptive and manipulative population studies of mice support the contention that MCMV would be a good carrier for an immunocontraceptive vaccine required to sustain female sterility levels at or above 65%.

Inhaled antibiotic therapy: What drug? What dose? What regimen? What formulation?

Early studies of the use of antibiotics in patients with cystic fibrosis suggested that they would be of benefit in preventing or reducing infection by Pseudomonas aeruginosa. In seeking to optimize treatment, factors such as the drug used, the dose, the regimen and the formulation must be considered. Aminoglycosides are ideal for aerosolization because they have a long post-antibiotic effect and have an acceptable taste. Tobramycin is one of the aminoglycosides with the lowest systemic toxicity, which enables the aerosol delivery of doses high enough to overcome the antagonistic effects of the sputum. The most dramatic benefits from inhaled tobramycin have been shown to occur in the first 2-4 weeks of administration. Continual administration for longer periods can result in the development of resistance and loss of the improvement in lung function. However, this resistance is transient, and susceptibility to tobramycin returns after a short drug holiday. Optimal drug administration therefore consists of a 4-week on, 4-week off cycle. Such a cycle also helps to maintain patient compliance. Successful drug delivery also depends upon a formulation that does not provoke bronchoconstriction, which demands a formulation that is both preservative free, and osmotically and pH balanced. This research has enabled the development of a novel formulation of tobramycin optimized for use as an inhalation therapy in cystic fibrosis.

Paediatric liver transplantation [corrected] in Melbourne: the first 50 patients

To report the outcomes of the first 50 paediatric patients who have undergone liver transplantation (LT) at the Victorian Liver Transplant Unit, a retrospective review of case records was carried out. From December 1988 to December 2000, 108 patients 18 years or younger were referred for LT; 50 of these underwent a total of 53 transplants. The most common indications were biliary atresia (32%), metabolic disease (26%), and acute hepatic necrosis (26%). The majority of deaths (6/7) occurred in the 1st week after LT. The actuarial survival at 1 year was 88% (95% CI 75% to 94%) and at 10 years 85% (95% CI 71% to 93%). Survival rates were highest for children aged 3 to 14 years (95%) and lowest in those weighing less than 8 kg at the time of LT (66%). All 43 survivors are attending age-appropriate activities including kindergarten, school, and employment. The survival of patients undergoing LT in this unit compares favourably with those recorded by the Australia and New Zealand Transplant Registry and is commensurate with that reported by larger paediatric transplant programs overseas.

AMPA receptor subunit RNA transcripts and [(3)H]AMPA binding in the cerebellum of normal and pcd mutant mice: an in situ hybridization study combined with receptor autoradiography

The expression of AMPA receptor subunit mRNAs and the binding of [(3)H]AMPA were studied in the cerebellum of normal and "Purkinje cell degeneration" ( pcd) mutant mouse. In the pcd cerebellum, [(3)H]AMPA binding was decreased significantly in both the molecular and granule cell layers by 63% and 36%, respectively. In those mutants, GluRA, GluRB and GluRC mRNAs were not detected in the Purkinje cell layer, and the levels of GluRB and GluRD mRNAs were significantly decreased in the granule cell layer by 16% and 57%, respectively. Cerebellar grafts transplanted into the pcd cerebellum expressed only GluRB and GluRC mRNAs, suggesting that donor cells express the appropriate subunits normally expressed by Purkinje neurons. Our results, firstly, support the idea that the expression of the GluRA subunit in Golgi epithelial cells may depend upon the sustained interaction with adjacent Purkinje cells, and secondly, suggest that granule cells which are more resistant to transsynaptic death may express higher levels of GluRB mRNA.

Blastocyst culture in human IVF: the final destination or a stop along the way?

In the field of human IVF, culturing embryos to the blastocyst stage has gained popularity within the past few years. The impetus to transfer blastocysts has been spurred by several factors: 1) the desire to improve implantation rates in infertility patients, 2) a desire to reduce the multiple pregnancy rate by transferring fewer embryos, 3) the desire to perform pre-implantation genetic diagnosis, and 4) the advent of sequential media. Although culturing human embryos to the Hastocyst stage has improved implantation rates and reduced the incidence of multiple pregnancies in some patient populations, it has not worked for all populations of infertility patients. Factors that may affect the ability of a human embryo to reach the blastocyst stage include the patient's age, cohort of ova retrieved, the use of intracytoplasmic sperm injection of blastomere biopsy, culture conditions, or intrinsic factors within the embryo itself. Culture of human embryos to the blastocyst stage can be an effective method for improving implantation rates and reducing the high order multiple pregnancy rates seen in human IVF clinics when more than three embryos are transferred.

Design and construction of a Haemophilus influenzae conjugal expression system

Haemophilus influenzae is a fastidious Gram-negative coccobacilli that is a common commensal in the human upper respiratory tract. However, certain strains of this bacterium, including those considered to be nontypeable (NTHi), can cause human diseases ranging from otitis media to meningitis. Although naturally competent, NTHi take up plasmids by transformation very inefficiently, if at all. Many clinical isolates have also proven refractory to the introduction of currently available shuttle vectors via electroporation. Further, it has been difficult to determine protein expression from these vectors, unless specific antisera has been raised or a phenotype conferred. To address these problems, we have designed and constructed a set of broad host range vectors that are transferable via intergeneric conjugation with an Escherichia coli strain carrying chromosomally-encoded transfer functions. These vectors provide a site for cloning promoter::MCS regions and carry genes encoding resistance to one of two different antibiotics. This conjugal system allows the expression of marker genes in NTHi strains, enabling researchers to track the microbe's progress either in vivo using the infant rat model of infection, or in vitro through invasions of human tissue culture cell lines.

Salmonella enterica serovar Pullorum persists in splenic macrophages and in the reproductive tract during persistent, disease-free carriage in chickens

Salmonella enterica serovar Pullorum is worldwide a poultry pathogen of considerable economic importance, particularly in those countries with a developing poultry industry. In addition to the characteristic high mortality rates among young chicks, one of the features of Salmonella serovar Pullorum infection is that it persists for long periods in convalescent chicks in the absence of clinical disease. This can lead to colonization of the reproductive tract of chickens and at sexual maturity can result in infected progeny through transovarian transmission to eggs. The sites of Salmonella serovar Pullorum persistence in convalescent birds are not known, and the mechanisms of persistence are not understood. Here we show that Salmonella serovar Pullorum can persist in both the spleen and the reproductive tract for over 40 weeks following experimental infection in chickens. During the period of sexual maturity, Salmonella serovar Pullorum colonized both the ovary and the oviduct of hens and led to 6% of laid eggs being infected by Salmonella serovar Pullorum. The colonization of several different sites of the reproductive tract suggests that Salmonella serovar Pullorum may employ more than one mechanism of egg infection. Persistence occurred despite a strong humoral response, suggesting an intracellular site of infection. By use of a Salmonella serovar Pullorum strain containing a plasmid stably expressing green fluorescent protein, we demonstrated that the main site of carriage in the spleen is within macrophages. This raises interesting questions about the biology of Salmonella serovar Pullorum, including why there is an increase in bacterial numbers when birds become sexually mature and in particular how Salmonella serovar Pullorum avoids clearance by macrophages and whether it modulates the immune system in other ways.

Long-term outcome of autoimmune hepatitis in children

BACKGROUND AND AIM

Autoimmune hepatitis (AIH) is a chronic disease of unknown etiology, which usually progresses to cirrhosis if not diagnosed and treated promptly. Data on long-term follow up in children with AIH are scant. The aim of this study is to assess the long-term outcome of autoimmune hepatitis in children with respect to clinical and laboratory features at presentation.

METHODS

Data were extracted from the medical records of patients presenting over a 28-year period (1972-2000) to the Royal Children's Hospital, Melbourne, Australia. Additional information was obtained by interviewing patients, and their current physicians. Of the 30 patients (22 females, mean age 9 years) identified, 18 had type I, three had type II, four had autoimmune-polyendocrinopathy syndrome type 1, one had infantile giant-cell hepatitis associated with Coomb's-positive hemolytic anemia, and four were seronegative (antinuclear antibody (ANA), smooth muscle antibody (SMA) and liver-kidney microsomal antibody (LKM)).

RESULTS

Clinical features at presentation included hepatomegaly (86%), jaundice (66%) and splenomegaly (50%). Initial investigations revealed a median serum bilirubin level of 55 micromol/L (range 6-425), median aspartate aminotransferase level of 678 IU (range 70-2548), and abnormal clotting in 33% of patients. Liver biopsies were performed on all patients at presentation and 11 showed cirrhosis (36%). The mean follow-up period was 10.0 +/- 7.8 years with 43% being followed for > 10 years. Only two patients died and one required transplantation. Fourteen (50%) patients continue to be on low dose prednisolone with azathioprine, two (7%) are on prednisolone alone, and six (21%) are on no therapy. When the cirrhotic and non-cirrhotic patients were compared, the albumin level at presentation was significantly lower in the cirrhotic group (P=0.01). Of the patients who were cirrhotic at presentation, six (54%) remain compensated with a mean follow-up period of 8 years. All 24 patients currently under follow up are engaged in age-appropriate activities including school, part- or full-time work.

CONCLUSION

Autoimmune hepatitis has a favorable long-term outcome with a transplant-free survival rate of 90% over a mean period of 10.0 +/- 7.8 years (range: 0.5-23), and a normal or near-normal lifestyle irrespective of presenting clinical, laboratory or histological features.

Changes in AMPA receptor binding and subunit messenger RNA expression in hippocampus and cortex in the pentylenetetrazole-induced 'kindling' model of epilepsy

'Kindling' is a phenomenon of epileptogenesis, which has been widely used as an experimental model of temporal lobe epilepsy. In the present study, we have examined the contribution of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) glutamate receptors and their subunits (GluR-A, -B, -C and -D) to the acquisition and maintenance of the kindled state in the pentylenetetrazole (PTZ)-induced 'kindling' mouse model, by using quantitative autoradiography and in situ hybridization. Region-specific increases in [3H]AMPA binding were seen in kindled animals in the CA3 region of hippocampus and in the temporal cortex 1 week after the last PTZ injection. At the same time, a significant decrease in the level of transcripts encoding the GluR-B and -C subunits was detected in the hippocampal CA1 region and dentate gyrus, suggestive of a higher proportion of Ca(2+)-permeable AMPA receptors in these neurons. These changes did not persist 1 month after establishment of kindling, indicating a transient role of AMPA receptors in the acquisition of the kindled state. At 1 month after the last PTZ injection, an upregulation in [3H]AMPA binding appeared in the motor cortex and the basal ganglia of kindled animals, which is consistent with electrophysiological data showing hyperexcitability in the cortex of the PTZ-kindled animals at that time. Interestingly, an increase in mRNA for the GluR-B subunit appeared in the outer layers of motor and somatosensory cortices of the kindled animals 1 month after acquisition of the kindled state, possibly as part of a gene-regulated, compensatory mechanism against seizure susceptibility, since this change should give rise to a higher proportion of Ca(2+)-impermeable AMPA receptors. These results support the evidence of a transient role of hippocampal AMPA receptors in the acquisition of the 'kindling' phenomenon and they also suggest an involvement of AMPA receptors in the maintenance of kindled state at least in two brain areas, cortex and basal ganglia.

Warfarin therapy does not increase bleeding in patients undergoing heart transplantation

BACKGROUND

Historically, warfarin has been discontinued or rapidly reversed with fresh frozen plasma in patients awaiting heart transplantation because of concerns regarding excessive bleeding. Because preoperative warfarin may have effects on bleeding after cardiac operations, we reviewed our experience to determine the risks in patients undergoing heart transplantation while maintained on warfarin.

METHODS

The records of consecutive adult patients undergoing heart transplantation from January 1996 to December 1998 were reviewed. Preoperative and 24-hour postoperative data were obtained, including patient demographics; hematologic laboratory values; medication use; repeat or primary sternotomy data; allogeneic blood product administration; and chest tube drainage. Multivariate linear and logistic regression analyses were performed using these variables to determine risk factors for bleeding after heart transplantation.

RESULTS

Ninety adult patients, mean age 50 years, underwent orthotopic heart transplantation during the 36-month period. No relationships existed between preoperative international normalized ratio (INR, mean = 1.83 +/- 0.1, p = 0.84) or postoperative INR (mean = 2.2 +/- 0.9, p = 0.63) and chest tube drainage (mean = 721 +/- 63 mL). Relationships were observed between total blood product administration and preoperative INR (partial r = 0.30, p = 0.01) and postoperative INR (partial r = -0.37, p = 0.002); however, preoperative INR did not correlate (p = 0.29) when perioperative use of fresh frozen plasma was factored as a covariate. Inverse relationships were evident between postoperative INR and total blood product exposures, as well as transfusions of platelets (partial r = -0.26, p = 0.03), fresh frozen plasma (partial r = -0.28, p = 0.02), and red cells (partial r = -0.25, p = 0.04).

CONCLUSIONS

Although we noted no correlations between INR and chest tube output, inverse relationships were observed with transfusion requirements in the first 24 hours after transplantation. Preoperative warfarin may be safely continued in patients awaiting heart transplantation.

Modelling host cell availability and the crowding effect in Eimeria infections

Within-host mathematical models of Eimeria maxima and Eimeria praecox infections of the chicken are presented and used to investigate the role of host cell availability as a possible determinant of the so-called 'crowding effect'; whereby the fecundity of the parasites decreases as infectious dose increases. Assumptions about the number of available host cells, the average lifespan of these cells and the age structure within the host-cell population were made and mathematical models were constructed and combined with experimental data to test whether these conditions could reproduce the crowding effect in the two species. Experimental data demonstrated that crowding during in vivo infections was apparent following very low infectious doses, but none of the models could adequately reproduce crowding at the same doses while maintaining realistic estimates of the dynamics of the enterocyte pool. However, both the size and lifespan of the enterocyte pool were demonstrated to have substantial effects on the fecundity of the infections, particularly at higher doses. These data indicate that host cell availability cannot be solely responsible for the crowding effect. Alternative factors such as the influence of the primary immune response to the parasite may also be explored using within-host models and other applications of these models are discussed.

Evolution of an autotransporter: domain shuffling and lateral transfer from pathogenic Haemophilus to Neisseria

The genomes of pathogenic Haemophilus influenzae strains are larger than that of Rd KW20 (Rd), the nonpathogenic laboratory strain whose genome has been sequenced. To identify potential virulence genes, we examined genes possessed by Int1, an invasive nonencapsulated isolate from a meningitis patient, but absent from Rd. Int1 was found to have a novel gene termed lav, predicted to encode a member of the AIDA-I/VirG/PerT family of virulence-associated autotransporters (ATs). Associated with lav are multiple repeats of the tetranucleotide GCAA, implicated in translational phase variation of surface molecules. Laterally acquired by H. influenzae, lav is restricted in distribution to a few pathogenic strains, including H. influenzae biotype aegyptius and Brazilian purpuric fever isolates. The DNA sequence of lav is surprisingly similar to that of a gene previously described for Neisseria meningitidis. Sequence comparisons suggest that lav was transferred relatively recently from Haemophilus to Neisseria, shortly before the divergence of N. meningitidis and Neisseria gonorrhoeae. Segments of lav predicted to encode passenger and beta-domains differ sharply in G+C base content, supporting the idea that AT genes have evolved by fusing domains which originated in different genomes. Homology and base sequence comparisons suggest that a novel biotype aegyptius AT arose by swapping an unrelated sequence for the passenger domain of lav. The unusually mobile lav locus joins a growing list of genes transferred from H. influenzae to Neisseria. Frequent gene exchange suggests a common pool of hypervariable contingency genes and may help to explain the origin of invasiveness in certain respiratory pathogens.

Possible roxithromycin-induced fulminant hepatic failure in a child

A pediatric formulation of roxithromycin is a relatively new addition to the antibiotic market in Australia. A previously healthy 5-year-old boy with no significant medical history was treated with roxithromycin 50 mg twice/day for cough, fever, and anorexia. After completing a 5-day course of the agent, he developed a nonpruritic, nonurticarial, erythematous, maculopapular, generalized rash and occasional vomiting. Three days later his symptoms included jaundice, dark urine, and pale stools. Laboratory results revealed acute hepatitis, and the patient was admitted to the hospital. His hepatic function continued to deteriorate, so the boy was transferred to a tertiary pediatric hospital. His condition continued to worsen, and 6 days after transfer, he underwent liver transplantation. Clinicians should be aware of potential hepatic complications associated with the use of roxithromycin.

Fatal hemolysis after high-dose etoposide: is benzyl alcohol to blame?

A 53-year-old African-American man with relapsed non-Hodgkin's lymphoma developed seizures and respiratory arrest 2 hours after an infusion of high-dose etoposide in preparation for an autologous bone marrow transplant. Laboratory tests revealed both rapid hemolysis and severe metabolic acidosis. The patient died the following day. Based on toxicities observed, we suspect that our patient possessed an ethnic polymorphism of the enzyme alcohol dehydrogenase. Further research is required to determine the relationship between the benzyl alcohol metabolic rate and toxicity and genetic polymorphisms of alcohol dehydrogenase in African-Americans.

Routine surveillance endomyocardial biopsy continues to detect significant rejection late after heart transplantation

BACKGROUND

The need for continued surveillance endomyocardial biopsies beyond the first year after cardiac transplantation is controversial. We evaluated the incidence of rejections requiring treatment (International Society Heart and Lung Transplantation grade 3A or greater) in patients 5 years or more after heart transplantation.

METHODS

We conducted a retrospective chart review of all patients who underwent at least 1 endomyocardial biopsy at our center 5 years or more after heart transplantation.

RESULTS

A total of 461 biopsies were performed in 77 patients 5 or more years after heart transplantation. Nine episodes of grade 3A or greater rejection were identified in 8 of 77 patients (10%). During the first year, 7.6% of biopsies were grade 3A or greater. Grade 3A rejection occurred in approximately 3.5% to 4% of biopsies during years 2 to 7. The overall incidence of procedural related complications at our institution was < 0.5%.

CONCLUSION

Endomyocardial biopsies continue to detect clinically significant rejection beyond 5 years after cardiac transplantation. The overall incidence of procedural related complications requiring treatment was low and none was life threatening. The absence of early rejection does not predict freedom from late rejection. Therefore, we continue to recommend surveillance biopsies in cardiac transplant recipients late after transplantation.

CYP3A inductive potential of the rifamycins, rifabutin and rifampin, in the rabbit

Rifabutin is effective in the treatment and prevention of Mycobacterium avium infection in people with HIV infection. Rifabutin is structurally related to another rifamycin, rifampin, a well-known inducer of the human P-450 isoform 3A. The rabbit isoform CYP3A6 and the human isoform CYP3A4 have similar P-450 predominance and substrate specificity and are both induced by rifampin. Our goal was to predict the CYP3A induction capacity of rifabutin and to determine if ex vivo CYP3A induction potential of rifamycins is predictive of that obtained in vivo. We determined the in vivo and ex vivo CYP3A6 induction by 4 days of treatment with rifabutin (100 mg/kg), rifampin (100 mg/kg), or vehicle (DMSO) in the rabbit. The ex vivo measures were CYP3A6 activity (N-demethylation of erythromycin and hydroxylation of triazolam) and CYP3A content in rabbit hepatic microsomes preparations. The in vivo measures were oral clearance of triazolam and its formation clearance to its hydroxylated metabolites, alpha-hydroxytriazolam and 4-hydroxytriazolam. Rifampin increased CYP3A6 activity by 2- to 3-fold in hepatic microsomes compared to vehicle. Rifabutin increased CYP3A content 1.7-fold, but did not significantly increase microsomal CYP3A6 activity. Oral triazolam clearance and formation clearances to the two hydroxylated metabolites were 2- to 3-fold greater in rabbits treated with rifampin. These clearances were unaffected by rifabutin administration. Ex vivo enzyme activities correlated with in vivo changes in clearance of triazolam and the formation clearance to its hydroxylated metabolites. Rifabutin is a weaker inducer of CYP3A6 than rifampin. These data suggest that ex vivo enzyme activity is a viable approach to predict in vivo inductive potential of CYP3A inducers.

Contribution of the DDDD motif of H. influenzae e (P4) to phosphomonoesterase activity and heme transport

Haemophilus influenzae lipoprotein e (P4) is a member of the DDDD phosphohydrolase superfamily and mediates heme transport. Each of the aspartate residues of the signature motif is required for phosphomonoesterase activity, as none of the e (P4) single D mutants (D64A, D66A, D181N, and D185A) possessed detectable phosphomonoesterase activity. These results suggest that the signature motif is essential to the phosphomonoesterase activity of lipoprotein e (P4). When assessed for phosphomonoesterase-dependent heme transport activity in Escherichia coli hemA strains, plasmids containing D181N and D185A retained heme transport as indicated by aerobic growth while D64A and D66A did not. We conclude that phosphomonoesterase activity is not required for heme transport.

Longitudinal assessment of Pseudomonas aeruginosa in young children with cystic fibrosis

Pseudomonas aeruginosa lung infection is an important cause of morbidity and mortality in cystic fibrosis (CF). Longitudinal assessment of the phenotypic changes in P. aeruginosa isolated from young children with CF is lacking. This study investigated genotypic and phenotypic changes in P. aeruginosa from oropharynx (OP) and bronchoalveolar lavage fluid (BALF) in a cohort of 40 CF patients during the first 3 years of life; antibody response was also examined. A high degree of genotypic variability was identified, and each patient had unique genotypes. Early isolates had a phenotype distinct from those of usual CF isolates: generally nonmucoid and antibiotic susceptible. Genotype and phenotype correlated between OP and BALF isolates. As determined by culture, 72.5% of patients demonstrated P. aeruginosa during their first 3 years. On the basis of combined culture and serologic results, 97.5% of patients had evidence of infection by age 3 years, which suggests that P. aeruginosa infection occurs early in CF and may be intermittent or undetectable by culture.

Serum resistance in an invasive, nontypeable Haemophilus influenzae strain

A common feature of many different organisms causing bacteremia is the ability to avoid the bactericidal effects of normal human serum. In Haemophilus influenzae encapsulated strains are particularly serum resistant; however, we found that a nonencapsulated strain (R2866) isolated from the blood of an immunocompetent child with meningitis who had been successfully immunized with H. influenzae type b conjugate vaccine was serum resistant. Since serum resistance usually involves circumventing the action of the complement system, we defined the deposition of various complement components on the surfaces of this H. influenzae strain (R2866), a nonencapsulated avirulent laboratory strain (Rd), and a virulent type b encapsulated strain (Eagan). Membrane attack complex (MAC) accumulation correlated with the loss of bacterial viability; correspondingly, the rates of MAC deposition on the serum-sensitive strain Rd and the serum-resistant strains differed. Analysis of cell-associated immunoglobulin G (IgG), C1q, C3b, and C5b indicated that serum-resistant H. influenzae prevents MAC accumulation by delaying the synthesis of C3b through the classical pathway. Among the initiators of the classical pathway, IgG deposition contributes most of the C3 convertase activity necessary to start the cascade ending with MAC deposition. Despite similar IgG binding, strain R2866 delays C3 convertase activity compared to strain Rd. We conclude that strain R2866 can persist in the bloodstream, in part by inhibiting or delaying C3 deposition on the cell surface, escaping complement mediated killing.

Solid-phase synthesis of 2,3-disubstituted indoles: discovery of a novel, high-affinity, selective h5-HT2A antagonist

The application of a novel solid-phase synthesis of 2,3-disubstituted indoles utilizing a carbamate indole linker is described resulting in the identification of the novel, high-affinity, selective h5-HT2A antagonist 19.

2-Aryl tryptamines: selective high-affinity antagonists for the h5-HT2A receptor

A series of 2-aryl tryptamines have been identified as high-affinity h5-HT2A antagonists. Structure-activity relationship studies have shown that h5-HT2A affinity can be attained via modifications to the tryptamine side chain and that selectivity over h5-HT2C and hD2 receptors can be controlled by suitable C-2 aryl groups.

Modification of immunologic and hematologic variables by method of CO2 euthanasia

BACKGROUND AND PURPOSE

The major goal was to determine whether variations in the method of CO2 euthanasia would induce significant immunologic differences.

METHODS

Young adult C57BL/6 mice (n = 40) were euthanized, using four regimens: 70% CO2/30% O2; 70% CO2/30% O2-->100% CO2; 100% CO2-naïve chamber; and 100% CO2 pre-charged chamber. Time to recumbency and euthanasia and body, liver, lung, spleen, and thymus masses were determined. Blood and spleen were further evaluated for leukocyte, lymphocyte, and thrombocyte counts, erythrocyte characteristics, distribution of lymphocyte subpopulations, spontaneous and mitogen-induced blastogenesis, complement activity, and cytokine production.

RESULTS

Time to euthanasia was five- to eightfold longer in mice exposed to 70% CO2/30% O2 than that for any other group. There were slight increases in mean erythrocyte volume (MCV) and mean erythrocyte hemoglobin (MCH) for all groups, compared with those for the 100% CO2 pre-charged group. Circulating cytotoxic T (CD8+) lymphocyte percentages and numbers, and spontaneous blastogenesis of leukocytes in blood and spleen, also were affected by euthanasia method.

CONCLUSIONS

The method of CO2 euthanasia can result in significant differences in immunologic/hematologic variables. Thus, consistency in euthanasia procedures may be important in accurate interpretation of research data.

The prevalence of viral antibodies during a large population fluctuation of house mice in Australia

We studied the seroprevalence of three viruses (mouse cytomegalovirus (MCMV), minute virus of mice (MVM), and mouse parvovirus (MPV)) in house mice (Mus domesticus) in 1995 7. In the first year average mouse density was less than 1 mouse/ha. From November 1995 to May 1996 the population increased at an average rate of 7% per week, a doubling time of about 10 weeks. From August 1996 to May 1997 the population increased at an average rate of 10% per week, a doubling time of about 7.5 weeks. From a peak around 250 mice/ha in May 1997, the mouse population fell 19% per week to 5 mice/ha in October 1997. The seroprevalence for all three viruses varied dramatically over time. MCMV had the highest seroprevalence (61.7%), followed by MVM (8.5%) and MPV (18.4%). Time series data indicated that MCMV spread rapidly through the population of mice once trap success was greater than 14% (40-100 mice/ha). By contrast MVM and MPV seroprevalence occurred with a 2-3 month and 3-4 month time lag, respectively. The current study supports the contention that MCMV would be a good carrier for an immunocontraceptive vaccine for controlling field populations of mice.

Visualizing T cell competition for peptide/MHC complexes: a specific mechanism to minimize the effect of precursor frequency

In vivo antigenic competition of naive CD4+ TCR transgenic T cells was visualized by tracking cell division. Competition reduced both recruitment into cell division and burst size per recruited precursor cell, minimizing the effect of differences in precursorfrequency while maintaining the dose-response relationship with antigen. Competition was restricted to T cells of the same specificity, indicating that cells were competing for access to Ag-MHC complexes rather than for Ag nonspecific factors. Moreover, the qualitative distinction between the responses to i.v. peptide and s.c. peptide/CFA was unaffected by precursor frequency. These data explain the paradoxical ability of the immune system to tailor responses to the type and dose of Ag even in individuals with large differences in initial precursor frequency.

An alphabeta T-cell-independent immunoprotective response towards gut coccidia is supported by gammadelta cells

Although gammadelta cells are commonly hypothesized to provide a 'first line of defence', gammadelta-cell-deficient mice are generally only marginally more susceptible to pathogens. Because gammadelta cells are enriched within epithelia, it is important to resolve whether immunoprotective capacity towards epithelial-tropic pathogens is absent from the gammadelta-cell compartment, or whether such activity is present but simply redundant with that of alphabeta T cells. In this work, following infection of the intestinal epithelium of alphabeta T-cell-deficient mice with the coccidian parasite, Eimeria vermiformis, gammadelta cells were shown to support the rapid activation of other lymphoid cells and to confer a transferable antipathogen effect that could be eradicated by neutralization of interferon-gamma. However, unlike alphabeta T cells, these effects of gammadelta cells showed no evidence of functional immunological memory. These results are directly relevant to coccidiosis, an economically significant disease of livestock, and should have general relevance to infections involving alphabeta T-cell deficiencies, e.g. cryptosporidiosis in patients with acquired immune deficiency syndrome (AIDS).

Genetic dissection of primary and secondary responses to a widespread natural pathogen of the gut, Eimeria vermiformis

Because most pathogens initially challenge the body at epithelial surfaces, it is important to dissect the mechanisms that underlie T-cell responses to infected epithelial cells in vivo. The coccidian parasites of the genus Eimeria are protozoan gut pathogens that elicit a potent, protective immune response in a wide range of host species. CD4+ alpha beta T cells and gamma interferon (IFN-gamma) are centrally implicated in the primary immunoprotective response. To define any additional requirements for the primary response and to develop a comparison between the primary and the secondary response, we have studied Eimeria infections of a broad range of genetically altered mice. We find that a full-strength primary response depends on beta(2)-microglobulin (class I major histocompatibility complex [MHC] and class II MHC and on IFN-gamma and interleukin-6 (IL-6) but not on TAP1, perforin, IL-4, Fas ligand, or inducible nitric oxide synthetase. Indeed, MHC class II-deficient and IFN-gamma-deficient mice are as susceptible to primary infection as mice deficient in all alpha beta T cells. Strikingly, the requirements for a highly effective alpha beta-T-cell-driven memory response are less stringent, requiring neither IFN-gamma nor IL-6 nor class I MHC. The class II MHC dependence was also reduced, with adoptively transferable immunity developing in MHC class II(-/-) mice. Besides the improved depiction of an immune response to a natural gut pathogen, the finding that effective memory can be elicited in the absence of primary effector responses appears to create latitude in the design of vaccine strategies.

Flow cytometric detection of HLA-specific antibodies as a predictor of heart allograft rejection

BACKGROUND

Historically, panel reactive antibody (PRA) analysis to detect HLA antibodies has been performed using cell-based complement-dependent cytotoxicity (CDC) techniques. Recently, a flow cytometric procedure (FlowPRA) was introduced as an alternative approach to detect HLA antibodies. The flow methodology, using a solid phase matrix to which soluble HLA class I or class II antigens are attached is significantly more sensitive than CDC assays. However, the clinical relevance of antibodies detected exclusively by FlowPRAhas not been established. In this study of cardiac allograft recipients, FlowPRA was performed on pretransplant sera with no detectable PRA activity as assessed by CDC assays. FlowPRA antibody activity was then correlated with clinical outcome.

METHODS

PRA analysis by anti-human globulin enhanced (AHG) CDC and FlowPRA was performed on sera corresponding to final cross-match specimens from 219 cardiac allograft recipients. In addition, sera collected 3-6 months posttransplant from 91 patients were evaluated. The presence or absence of antibodies was correlated with episodes of rejection and patient survival. A rejection episode was considered to have occurred based on treatment with antirejection medication and/or histology.

RESULTS

By CDC, 12 patients (5.5%) had pretransplant PRA >10%. In contrast, 72 patients (32.9%) had pretransplant anti-HLA antibodies detectable by FlowPRA (34 patients with only class I antibodies; 7 patients with only class II antibodies; 31 patients with both class I and class II antibodies). A highly significant association (P<0.001) was observed between pretransplant HLA antibodies detected by FlowPRA and episodes of rejection that occurred during the first posttransplant year. Fifteen patients died within the first year posttransplant. Of nine retrospective flow cytometric cross-matches that were performed, two were in recipients who had no pretransplant antibodies detectable by FlowPRA. Both of these cross-matches were negative. In contrast, five of seven cross-matches were positive among recipients who had FlowPRA detectable pretransplant antibodies. Posttransplant serum specimens from 91 patients were also assessed for antibodies by FlowPRA. Among this group, 58 patients had FlowPRA antibodies and there was a trend (although not statistically significant) for a biopsy documented episode of rejection to have occurred among patients with these antibodies.

CONCLUSIONS

Collectively, our data suggest that pre- and posttransplant HLA antibodies detectable by FlowPRA and not AHG-CDC identify cardiac allograft recipients at risk for rejection. Furthermore, a positive donor reactive flow cytometric cross-match is significantly associated with graft loss. Thus, we believe that detection and identification of HLA-specific antibodies can be used to stratify patients into high and low risk categories. An important observation of this study is that in the majority of donor:recipient pairs, pretransplant HLA antibodies were not directed against donor antigens. We speculate that these non-donor-directed antibodies are surrogate markers that correspond to previous T cell activation. Thus, the rejection episodes that occur in these patients are in response to donor-derived MHC peptides that share cryptic determinants with the HLA antigens that initially sensitized the patient.

Hepatitis C infection in children: a Melbourne perspective

OBJECTIVE

To examine the clinical spectrum of hepatitis C virus (HCV) infected children in our care by determining presentation, mode of acquisition, degree of co-infection, biochemical evidence of persisting hepatitis and treatment outcome.

METHODOLOGY

A retrospective review of the medical records of all children attending the Royal Children's Hospital, Melbourne, between 1990 and 1998, who had antibodies to HCV infection detected. Detailed clinical information, investigations and the results of treatment were extracted from the clinical notes.

RESULTS

A total of 94 children (age range 2 weeks to 19.7 years) were identified, of whom nine had passive transfer of maternal antibodies from HCV-positive mothers and were excluded from analysis. Sixty-seven children (79%) were infected by transfusion of blood or blood products. Perinatal transmission occurred in 11 children (13%), and six children (7%) had a history of i.v. drug abuse. The majority of children were asymptomatic at presentation. Of the 65 patients tested for HCV-ribonucleic acid, 43 (66%) were positive. Fifty-seven cases had serial alanine aminotransaminase (ALT) measurements over a mean of 28 months. Of these, 38 (67%) had an abnormal ALT. Ten cases (12%) were co-infected with hepatitis B virus, HIV or both. Of 12 patients treated with interferon, four responded with normalisation of ALT from 3 to 12 months post-commencement of therapy.

CONCLUSIONS

Although HCV was largely an asymptomatic condition in our clinic population, more than half the patients had biochemical evidence of ongoing liver damage. Given the chronicity of this infection in the majority of patients and the long-term risks of cirrhosis and hepatocellular carcinoma, children with HCV infection represent a high-risk group worthy of regular follow up.

L-685,458, an aspartyl protease transition state mimic, is a potent inhibitor of amyloid beta-protein precursor gamma-secretase activity

Progressive cerebral amyloid beta-protein (A beta) deposition is believed to play a central role in the pathogenesis of Alzheimer's disease (AD). Elevated levels of A beta(42) peptide formation have been linked to early-onset familial AD-causing gene mutations in the amyloid beta-protein precursor (A beta PP) and the presenilins. Sequential cleavage of A beta PP by the beta- and gamma-secretases generates the N- and C-termini of the A beta peptide, making both the beta- and gamma-secretase enzymes potential therapeutic targets for AD. The identity of the A beta PP gamma-secretase and the mechanism by which the C-termini of A beta are formed remain uncertain, although it has been suggested that the presenilins themselves are novel intramembrane-cleaving gamma-secretases of the aspartyl protease class [Wolfe, M. S., Xia, W., Ostaszewski, B. L., Diehl, T. S., Kimberly, W. T., and Selkoe, D. J. (1999) Nature 398, 513-517]. In this study we report the identification of L-685,458 as a structurally novel inhibitor of A beta PP gamma-secretase activity, with a similar potency for inhibition of A beta(42) and A beta(40) peptides. This compound contains an hydroxyethylene dipeptide isostere which suggests that it could function as a transition state analogue mimic of an aspartyl protease. The preferred stereochemistry of the hydroxyethylene dipeptide isostere was found to be the opposite to that required for inhibition of the HIV-1 aspartyl protease, a factor which may contribute to the observed specificity of this compound. Specific and potent inhibitors of A beta PP gamma-secretase activity such as L-685,458 will enable important advances toward the identification and elucidation of the mechanism of action of this enigmatic protease.