A small heat shock protein is essential for thermotolerance and intracellular survival of Leishmania donovani

Leishmania parasites must survive and proliferate in two vastly different environments – the guts of poikilothermic sandflies and the antigen-presenting cells of homeothermic mammals. The change of temperature during the transmission from sandflies to mammals is both a key trigger for the progression of their life cycle and for elevated synthesis of heat shock proteins, which have been implicated in their survival at higher temperatures. Although the functions of the main heat shock protein families in the Leishmania life cycle have been studied, nothing is known about the roles played by small heat shock proteins. Here, we present the first evidence for the pivotal role played by the Leishmania donovani 23-kDa heat shock protein (which we called HSP23), which is expressed preferentially during the mammalian stage where it assumes a perinuclear localisation. Loss of HSP23 causes increased sensitivity to chemical stressors and renders L. donovani non-viable at 37°C. Consequently, HSP23-null mutants are non-infectious to primary macrophages in vitro. All phenotypic effects could be abrogated by the introduction of a functional HSP23 transgene into the null mutant, confirming the specificity of the mutant phenotype. Thus, HSP23 expression is a prerequisite for L. donovani survival at mammalian host temperatures and a crucial virulence factor.

The Leishmania donovani chaperone cyclophilin 40 is essential for intracellular infection independent of its stage-specific phosphorylation status

During its life cycle, the protozoan pathogen Leishmania donovani is exposed to contrasting environments inside insect vector and vertebrate host, to which the parasite must adapt for extra- and intracellular survival. Combining null mutant analysis with phosphorylation site-specific mutagenesis and functional complementation we genetically tested the requirement of the L. donovani chaperone cyclophilin 40 (LdCyP40) for infection. Targeted replacement of LdCyP40 had no effect on parasite viability, axenic amastigote differentiation, and resistance to various forms of environmental stress in culture, suggesting important functional redundancy to other parasite chaperones. However, ultrastructural analyses and video microscopy of cyp40-/- promastigotes uncovered important defects in cell shape, organization of the subpellicular tubulin network and motility at stationary growth phase. More importantly, cyp40-/- parasites were unable to establish intracellular infection in murine macrophages and were eliminated during the first 24 h post infection. Surprisingly, cyp40-/- infectivity was restored in complemented parasites expressing a CyP40 mutant of the unique S274 phosphorylation site. Together our data reveal non-redundant CyP40 functions in parasite cytoskeletal remodelling relevant for the development of infectious parasites in vitro independent of its phosphorylation status, and provide a framework for the genetic analysis of Leishmania-specific phosphorylation sites and their role in regulating parasite protein function.

Pasteurella multocida infected total knee arthroplasty: a case report and review of the literature

Pasteurella multocida is a rare cause of prosthetic joint infection. This infection generally follows significant animal contact, usually licks and scratches. We report a case of P multocida infection that was treated with linezolid with salvage of the implant. Linezolid is generally active against Gram-positive organisms only with the exception of Pasteurella, which is Gram-negative. We extensively review the previous reported cases of implant infection with P multocida.

Dietary practices in pyridoxine non-responsive homocystinuria: a European survey

BACKGROUND

Within Europe, the management of pyridoxine (B6) non-responsive homocystinuria (HCU) may vary but there is limited knowledge about treatment practice.

AIM

A comparison of dietetic management practices of patients with B6 non-responsive HCU in European centres.

METHODS

A cross-sectional audit by questionnaire was completed by 29 inherited metabolic disorder (IMD) centres: (14 UK, 5 Germany, 3 Netherlands, 2 Switzerland, 2 Portugal, 1 France, 1 Norway, 1 Belgium).

RESULTS

181 patients (73% >16 years of age) with HCU were identified. The majority (66%; n=119) were on dietary treatment (1-10 years, 90%; 11-16 years, 82%; and >16 years, 58%) with or without betaine and 34% (n=62) were on betaine alone. The median natural protein intake (g/day) on diet only was, by age: 1-10 years, 12 g; 11-16 years, 11 g; and >16 years, 45 g. With diet and betaine, median natural protein intake (g/day) by age was: 1-10 years, 13 g; 11-16 years, 20 g; and >16 years, 38 g. Fifty-two percent (n=15) of centres allocated natural protein by calculating methionine rather than a protein exchange system. A methionine-free l-amino acid supplement was prescribed for 86% of diet treated patients. Fifty-two percent of centres recommended cystine supplements for low plasma concentrations. Target treatment concentrations for homocystine/homocysteine (free/total) and frequency of biochemical monitoring varied.

CONCLUSION

In B6 non-responsive HCU the prescription of dietary restriction by IMD centres declined with age, potentially associated with poor adherence in older patients. Inconsistencies in biochemical monitoring and treatment indicate the need for international consensus guidelines.

Possible Kondo physics near a metal-insulator crossover in the a-site ordered perovskite CaCu3Ir4O12

The A-site ordered perovskite (AA(3)')B(4)O(12) can accommodate transition metals on both A' and B sites in the crystal structure. Because of this structural feature, it is possible to have narrow-band electrons interacting with broadband electrons from different sublattices. Here we report a new A-site ordered perovskite (CaCu(3))Ir(4)O(12) synthesized under high pressure. The coupling between localized spins on Cu(2+) and itinerant electrons from the Ir-O sublattice makes Kondo-like physics take place at a temperature as high as 80 K. Results from the local density approximation calculation have confirmed the relevant band structure. The magnetization anomaly found at 80 K can be well rationalized by the two-fluid model.

Body mass index in adult patients with diet-treated phenylketonuria

BACKGROUND

There is an increasing number of adults with phenylketonuria (PKU) on a low phenylalanine diet. In the general population, an increasing body mass index (BMI) in the UK is a major problem with associated co-morbidities. The present study aimed to identify whether patients with diet-treated PKU have obesity rates comparable to those in the general population.

METHODS

Two hundred and thirty-six PKU subjects (49% male, 51% female), aged >16 years, who were diagnosed by newborn screening and were receiving a low phenylalanine diet, were identified from seven metabolic centres in the UK. Retrospective data were collated on age, sex, BMI and mean phenylalanine concentration over the previous 12 months.

RESULTS

Mean (SD) phenylalanine concentration for all 236 subjects was 789 (311) μm; mean (SD) BMI was 26 (5.4) kg m(-2) [males 25 (4.3) kg m(-2) , females 27 (6.2) kg m(-2) ]; mean (SD) age was 26 (7) years; and 55% had a BMI > 25 kg m(-2) . The percentage of subjects with a BMI >25 kg m(-2) and >30 kg m(-2) , as well as increasing obesity with age, was similar to the UK population. A correlation was observed between increasing BMI and a higher phenylalanine concentration (r = 0.243, P = 0.001).

CONCLUSIONS

The number of overweight and obese patients with diet-treated PKU in the UK is a concern. This could lead to other obesity-related complications increasing the complexity of diet and the cost of their care. There is a need to educate patients with respect to adopting a healthy, low phenylalanine diet and lifestyle to prevent further rises in BMI.

Use of sapropterin in the management of phenylketonuria: seven case reports

Sapropterin treatment, with or without dietary treatment, improves blood phenylalanine control, increases phenylalanine tolerance, and may reduce the day-to-day dietary treatment burden in a subset of patients with phenylketonuria (PKU). Balancing the need for maintained control of blood phenylalanine with diet relaxation is complex when administering sapropterin. We present a series of seven patient cases with PKU that illustrate important aspects of using sapropterin with diet in the management of the disorder.

Main issues in micronutrient supplementation in phenylketonuria

For almost all patients with PKU, a low phenylalanine diet is the basis of the treatment despite a widely varying natural protein tolerance. A vitamin and mineral supplement is essential and it is commonly added to a phenylalanine-free (phe-free) source of L-amino acids. In PKU, many phe-free L-amino acid supplements have age-specific vitamin and mineral profiles to meet individual requirements. The main micronutrient sources are chemically derived and their delivery dosage is usually advised in three or more doses throughout the day. Within the EU, the composition of VM (vitamin and mineral) phe-free L-amino acid supplements is governed by the Foods for Special Medical Purposes (FSMP) directive (European Commission Directive number 1999/21/EC and amended by Directive 2006/141/EC). However the micronutrient composition of the majority fails to remain within FSMP micronutrient maximum limits per 100 kcal due to their low energy content and so compositional exceptions to the FSMP directive have to be granted for each supplement. All patients with PKU require an annual nutritional follow-up, until it has been proven that they are not at risk of any vitamin and mineral imbalances. When non-dietary treatments are used to either replace or act as an adjunct to diet therapy, the quality of micronutrient intake should still be considered important and monitored systematically. European guidelines are required about which micronutrients should be measured and the conditions (fasting status) for monitoring.

Micronutrient status in phenylketonuria

Patients with phenylketonuria (PKU) encompass an 'at risk' group for micronutrient imbalances. Optimal nutrient status is challenging particularly when a substantial proportion of nutrient intake is from non-natural sources. In PKU patients following dietary treatment, supplementation with micronutrients is a necessity and vitamins and minerals should either be added to supplement phenylalanine-free l-amino acids or given separately. In this literature review of papers published since 1990, the prevalence of vitamin and mineral deficiency is described, with reference to age of treatment commencement, type of treatment, dietary compliance, and dietary practices. Biological micronutrient inadequacies have been mainly reported for zinc, selenium, iron, vitamin B12 and folate. The aetiology of these results and possible clinical and biological implications are discussed. In PKU there is not a simple relationship between the dietary intake and nutritional status, and there are many independent and interrelated complex factors that should be considered other than quantitative nutritional intake.

Home enteral tube feeding in children with inherited metabolic disorders: a review of long-term carer knowledge and technique

BACKGROUND

Home enteral tube feeding (HETF) is commonly used in children with inherited metabolic disorders (IMD). It is unclear how caregiver knowledge and their safety in using tube feeding techniques changes over time.

METHODS

Caregivers of children with IMD on HETF from one UK IMD centre had annual interviews over 3 years using a structured questionnaire and observation to assess HETF knowledge and safety techniques.

RESULTS

Thirty-two caregivers of IMD children (median age 5.3 years; range 0.3-13.6 years) were studied. Seventy-eight percent (n = 25) of subjects had been on HETF for >5 years. Over 3 years, many caregivers' HETF techniques deteriorated: accurate feed ingredient measurement decreased from 36% to 11%; correct flushing of tubes decreased from 56% to 44%; checking tube position as recommended decreased from 72% to 56%; and correct hand washing decreased from 38% to 25%. Despite improvements, knowledge of some aspects remained poorly understood: dangers of incorrect tube placement increased from 41% to 56%; correct position for night feeding increased from 38% to 56%; and feed ingredient storage decreased from 87% to 38%.

CONCLUSIONS

The HETF techniques of caregivers of children with IMD declined over time. Caregivers need to understand that HETF, particularly in IMD, is a serious procedure associated with life-threatening risks. Poor HETF practices may cause feed contamination, incorrect feed concentration, feed intolerance, aspiration, peritonitis and even metabolic decompensation. HETF skills should be reassessed annually, with compulsory retraining if basic 'core' HETF competencies are not demonstrated.

Dietary management of urea cycle disorders: UK practice

BACKGROUND

There is no published data describing UK dietary management of urea cycle disorders (UCD). The present study describes dietary practices in UK inherited metabolic disorder (IMD) centres.

METHODS

Cross-sectional data from 16 IMD centres were collected by a questionnaire describing the management of UCD patients on prescribed protein-restricted diets.

RESULTS

One hundred and seventy-five patients [N-acetylglutamate synthase deficiency, n = 3; carbamoyl phosphate synthase deficiency (CPS), n = 8; ornithine transcarbamoylase deficiency (OTC), n = 75; citrullinaemia, n = 41; argininosuccinic aciduria (ASA), n = 36; arginase deficiency, n = 12] were reported; 70% (n = 123) aged 0-16 years; 30% (n = 52) >16 years. Prescribed median protein intake decreased with age (0-6 months: 2 g kg(-1) day(-1); 7-12 months: 1.6 g kg(-1) day(-1); 1-10 years: 1.3 g kg(-1) day(-1); 11-16 years: 0.9 g kg(-1) day(-1) and >16 years: 0.8 g kg(-1) day(-1)) with little variation between disorders. Adult protein prescription ranged 0.4-1.2 g kg(-1) day(-1) (40-60 g day(-1)). In the previous 2 years, 30% (n = 53) were given essential amino acid supplements (EAAs) (CPS, n = 2; OTC, n = 20; citrullinaemia, n = 15; ASA, n = 7; arginase deficiency, n = 9). EAAs were prescribed for low plasma quantitative essential amino acids (n = 13 centres); inadequate natural protein intake (n = 11) and poor metabolic control (n = 9). From diagnosis, one centre prescribed EAAs for all patients and one centre for severe defects only. Only 3% (n = 6) were given branch chain amino acid supplements. Enteral feeding tubes were used by 25% (n = 44) for feeds and 3% (n = 6) for medications. Oral energy supplements were prescribed in 17% (n = 30) of cases.

CONCLUSIONS

In the UK, protein restriction based on World Health Organization 'safe intakes of protein', is the principle dietary treatment for UCD. EAA supplements are prescribed mainly on clinical need. Multicentre collaborative research is required to define optimal dietary treatments.

Diet in phenylketonuria: a snapshot of special dietary costs and reimbursement systems in 10 international centers

BACKGROUND AND AIMS

To gather exploratory data on the costs and reimbursement of special dietary foods used in the management of phenylketonuria (PKU) from ten international specialist PKU centers.

METHODS

Experts from each center provided data on retail costs of the three most frequently used phenylalanine-free protein substitutes and low-protein foods at their center; reimbursement of protein substitutes and low-protein foods; and state monetary benefits provided to PKU patients.

RESULTS

The mean annual cost of protein substitutes across 4 age groups (2 y, 8 y, 15 y and adults) ranged from €4273 to €21,590 per patient. The cost of low-protein products also differed; the mean cost of low-protein bread varied from €0.04 to €1.60 per 100 kcal. All protein substitutes were either fully reimbursed or covered by health insurance. However, reimbursement for low-protein products varied and state benefits differed between centers.

CONCLUSIONS

The variation in the cost and reimbursement of diet therapy and the level of additional state benefits for PKU patients demonstrates the large difference in expenditure on and access to PKU dietary products. This highlights the inequality between healthcare systems and access to special dietary products for people with PKU, ultimately leading to patients in some countries receiving better care than others.

Diurnal variation of phenylalanine concentrations in tyrosinaemia type 1: should we be concerned?

BACKGROUND

Tyrosinaemia type 1 (HT1) is treated with a tyrosine and phenylalanine-restricted diet, amino acids free of phenylalanine and tyrosine, and nitisinone (NTBC). Treatment guidelines recommend plasma tyrosine between 200-400 μm and phenylalanine at least >30 μm. There is little information on the diurnal variation of plasma tyrosine or phenylalanine in HT1. Low plasma phenylalanine <30 μm may be associated with poor growth and cognitive delay. The present study aimed to document diurnal variation of tyrosine and phenylalanine plasma concentrations and growth in children with HT1.

METHODS

Median tyrosine and phenylalanine plasma concentrations were reviewed retrospectively over 3 years in 11 subjects (median age 4 years) with HT1. Subjects routinely collected morning fasting blood samples but afternoon nonfasted samples were taken in the clinic (<10% of samples). Growth Z-scores were calculated.

RESULTS

The percentage of all plasma phenylalanine concentrations <30 μm was 8.6% and <40 μm was 13.6%. Only 2% of fasting morning phenylalanine concentrations were <30 μm, compared to 83% of nonfasting afternoon samples. All but one child had a height Z-score <0.

CONCLUSIONS

Blood phenylalanine concentrations were consistently lower in the afternoon. Taking blood samples at variable time points in the day may lead to variation in interpreting dietary control. A detailed study is necessary to examine the 24-h diurnal variation of plasma phenylalanine and tyrosine in HT1. It is possible that phenylalanine concentrations may be very low for a substantive time over 24 h and the potential impact that this may have on cognitive development and growth in children is unknown.