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.

Photoactivated gamma-secretase inhibitors directed to the active site covalently label presenilin 1

Cleavage of amyloid precursor protein (APP) by the beta- and gamma-secretases generates the amino and carboxy termini, respectively, of the A beta amyloidogenic peptides A beta40 and A beta42--the major constituents of the amyloid plaques in the brain parenchyma of Alzheimer's disease patients. There is evidence that the polytopic membrane-spanning proteins, presenilin 1 and 2 (PS1 and PS2), are important determinants of gamma-secretase activity: mutations in PS1 and PS2 that are associated with early-onset familial Alzheimer's disease increase the production of A beta42 (refs 4-6), the more amyloidogenic peptide; gamma-secretase activity is reduced in neuronal cultures derived from PS1-deficient mouse embryos; and directed mutagenesis of two conserved aspartates in transmembrane segments of PS1 inactivates the ability of gamma-secretase to catalyse processing of APP within its transmembrane domain. It is unknown, however, whether PS1 (which has little or no homology to any known aspartyl protease) is itself a transmembrane aspartyl protease or a gamma-secretase cofactor, or helps to colocalize gamma-secretase and APP. Here we report photoaffinity labelling of PS1 (and PS2) by potent gamma-secretase inhibitors that were designed to function as transition state analogue inhibitors directed to the active site of an aspartyl protease. This observation indicates that PS1 (and PS2) may contain the active site of gamma-secretase. Interestingly, the intact, single-chain form of wild-type PS1 is not labelled by an active-site-directed photoaffinity probe, suggesting that intact wild-type PS1 may be an aspartyl protease zymogen.

Angiographic and clinical follow-up of percutaneous revascularization for transplant coronary artery disease

BACKGROUND

There are limited data on the use of percutaneous revascularization techniques for transplant coronary artery disease (CAD).

METHODS

Medical records and angiographic results for cardiac transplant patients undergoing percutaneous revascularization at Emory University Hospital were reviewed. Procedural results, results of angiography 4Eth 6 months after intervention, and clinical follow-up were recorded.

RESULTS

Nineteen patients underwent 51 interventions. Thirty-eight lesions (75%) were de novo and 13 (25%) were restenotic. All patients had hypertension, 37% had diabetes, 79% had elevated lipid levels, and 53% had at least one episode of moderate to severe allograft rejection (grade 3A or greater). The primary procedural success rate was 100% with no major complications. Six-month restenosis rate (defined as > 50%) was 49%. At 23+/-17 months follow-up, 6 patients were dead or retransplanted (31%). Thirteen patients were alive without retransplantation (9 New York Heart Association class I, 3 class II, 1 class III).

CONCLUSION

Percutaneous revascularization is safe and has a high initial procedural success rate in patients with transplant CAD. However, the restenosis rate in this population remains higher than reported for atherosclerotic coronary disease and the long-term prognosis remains poor.

Some recent thinking on personhood

This essay surveys four recent theological works on the issue of personhood: John F. Crosby's The Selfhood of the Human Person, Stanley Rudman's Concepts of Person and Christian Ethics, Metropolitan Hierotheos Vlachos' The Person in the Orthodox Tradition, and James Walter's What is a Person? An Ethical Exploration.

Diagnosis of Wilson's disease: an experience over three decades

BACKGROUND

Wilson's disease is a rare but treatable condition that often presents diagnostic dilemmas. These dilemmas have for the most part not been resolved by the identification and cloning of the Wilson's disease gene.

AIMS

To report our experience over three decades with patients with Wilson's disease in order to illustrate the diverse patterns of presentation and thereby broaden the approach to diagnosis.

METHODS

Clinical and laboratory findings of 30 patients with Wilson's disease were reviewed.

RESULTS

Twenty two patients presented with liver manifestations (eight with fulminant hepatic failure and 14 with chronic liver disease), three with neurological disease, and one with haemolysis; four were asymptomatic siblings of patients with Wilson's disease. Seventy per cent were diagnosed within six months of the onset of symptoms, but diagnosis was delayed for up to nine years. Age range at diagnosis was wide (7-58 years) and five patients were over 40. In patients presenting with non-fulminant disease, 18% had neither Kayser-Fleischer rings nor low caeruloplasmin concentrations. Increased liver copper concentrations were found in all but one patient who had undergone six years of penicillamine treatment. In fulminant hepatic failure (n=8) additional features helpful in the diagnosis included evidence of haemolysis, increased urinary copper (range 844-9375 microg/24 h), and a high non-caeruloplasmin copper (range 325-1743 microg/l).

CONCLUSIONS

The diagnosis of Wilson's disease still depends primarily on the evaluation of clinical and laboratory evidence of abnormal copper metabolism. No one feature is reliable, but the diagnosis can usually be made provided that it is suspected. Wilson's disease should be considered in patients of any age with obscure hepatic or neurological abnormalities.

Enterobacter cloacae bloodstream infections traced to contaminated human albumin

In August 1996, a patient in Kansas developed an Enterobacter cloacae bloodstream infection (BSI) shortly after receiving Albuminar, a brand of human albumin. Albuminar contamination was suspected. A case-control study of patients with primary gram-negative bacterial BSIs showed that patients with E. cloacae BSIs were significantly more likely than patients with non-E. cloacae gram-negative BSIs to have received Albuminar within 3 days of developing their BSIs (3 of 5 vs. 0 of 9; OR, undefined; P=.03). The E. cloacae isolate from the Kansas patient was found by pulsed-field gel electrophoresis to be identical to the isolate from the patient's Albuminar vial, to isolates from 2 previously unopened Albuminar vials, and to an isolate from a Wisconsin patient who had received Albuminar. A worldwide recall of approximately 116,000 Albuminar vials took place. This multistate outbreak was detected because of clinical astuteness and prompt reporting. Combined epidemiological and laboratory approaches are valuable when investigating potentially contaminated blood components and plasma derivatives.

Purification and characterization of a recombinant Haemophilus influenzae outer membrane phosphomonoesterase e (P4)

Haemophilus influenzae is a common inhabitant of the upper respiratory tract and can cause serious infections of mucosal surfaces. Results from recent studies indicate that this pathogen possesses copious amounts of surface-localized phosphomonoesterase activity mediated by the bacterial lipoprotein e (P4). While the enzyme has previously been purified to apparent homogeneity, purification of large amounts of protein has been prevented by presence of N-terminal lipid modification. Recombinant DNA technology was employed to simultaneously replace the N-terminal lipid modification signal sequence with one for protein secretion without such modification and to place expression of the protein under the control of the T7-inducible promoter. Results from this work show that high levels of phosphomonoesterase activity were achieved after IPTG induction and purified to apparent homogeneity after two chromatography steps. Consistent with loss of the N-terminal lipid modification, the recombinant enzyme was easily extracted from the bacterial membrane and partitioned within the matrix of gel filtration chromatography resin while retaining a denatured molecular weight similar to that of wild-type e (P4). Results from physicochemical characterization suggest that the recombinant protein was similar to wild-type protein in SDS-PAGE-derived molecular weight, primary structure, substrate specificity, pH optimum, and sensitivity or resistance to various inhibitors. Acquisition of sufficient amounts of recombinant P4 was a prelude for studies to elucidate the structure and function of this unusual phosphomonoesterase.

Carboxyfluorescein diacetate succinimidyl ester and the virgin lymphocyte: a marriage made in heaven

Carboxyfluorescein diacetate succinimidyl ester (CFSE) labelling of naïve lymphocyte populations provides unique insights into the immune response. The clonal nature of immune responses, necessitating clonal expansion to achieve a sufficiently large number of Ag-reactive effector cells, combined with the dependence of lymphocyte differentiation on cell division, underlie the usefulness of CFSE in understanding the factors that regulate responses both in vitro and in vivo. We have combined CFSE labelling with Ag receptor transgenic models, using seven channel flow cytometry to track the correlation between cell division and a number of other parameters, such as surface expression of activation markers, cytokine receptors and homing receptors, cytokine production, cytotoxic activity and indicators of apoptosis. Our data have allowed us to classify and understand immune responses in novel ways, suggesting many further avenues of enquiry and indicating previously unrecognized relationships between cell division and eventual cell fate.

Acid phosphatase activity as a measure of Haemophilus influenzae adherence to mucin

Haemophilus influenzae is an important respiratory tract pathogen. Toward understanding the progression of H. influenzae from commensal to pathogen, we need to understand the steps of colonization and infection, processes which must involve overcoming the normal host mucociliary clearance mechanism. A reliable method for the screening and quantitation of mucin-H. influenzae binding to allow for the assessment of the physiological variables significant to H. influenzae-mucin interactions in the normal and diseased conditions, will provide insight on how to intervene to prevent, inhibit, or treat infection. The current methods for enumeration of mucin-bound H. influenzae are labor intensive and rely on viable organisms. In this report, we present a new detection method, which reduces the number of variables, processing steps, and time involved, providing an economical, rapid, and reliable means to screen for and quantitate mucin-bound H. influenzae. Organisms are applied to mucin-coated microtiter wells for a set time; nonadherent organisms are removed with gentle rinses; wells are incubated with the phosphomonoesterase substrate p-nitrophenyl phosphate; and the absorbance, reflecting phosphatase activity of the mucin-bound organisms, is read at 410 nm in a microtiter plate reader against enzymatic activity calibration curves. All nonencapsulated and encapsulated H. influenzae tested exhibited significant acid phosphate activity within 20 min, which provided linear relationships with the numbers of organisms present. H. influenzae mucin binding characteristics obtained by this method were generally comparable to published data, and ranged from 10(3) to 10(6) organisms per well, depending on both strain of organism and type of mucin employed. This convenient, rapid and economical mucin adherence assay, will enable more extensive and comprehensive studies of the interactions of H. influenzae adhesins and specific ligands on mucin macromolecules, as well as the nonspecific means by which mucins function in preventing bacterial infection.

Night blindness precipitated by isotretinoin in the setting of hypovitaminosis A

A 16-year-old male developed night blindness 2 weeks after starting isotretinoin at a dose of 20 mg per day for cystic acne. He also had cystic fibrosis, complicated by hepatic cirrhosis. Despite long-term oral vitamin A supplementation, serum vitamin A levels were found to be 0.3 mumol/L (normal range 0.9-2.5 mumol/L). Oral vitamin A replacement was instituted with resolution of his visual symptoms in 6 months. Isotretinoin therapy was successfully continued with no deterioration in liver function. Isotretinoin has been reported to cause deterioration in night vision. In vitro evidence suggests isotretinoin may interfere with the processing of endogenous vitamin A in the retina. This case highlights the need for careful monitoring of serum vitamin A status in patients with malabsorptive states on isotretinoin therapy.