A web-based psychological support program for caregivers of children with rare chronic diseases: a randomized controlled trial.

BACKGROUND: Approximately 50% of rare diseases have symptom onset during childhood. A high level of nursing care and an often uncertain prognosis put caregivers of the affected children at high risk for psychological distress. At the same time, their caregivers have limited access to appropriate psychological care. The aim of this study was to evaluate a web-based psychological support program for caregivers of children with chronic rare diseases (WEP-CARE). METHODS: German-speaking parents (recruited between May 2016 and March 2018) caring for children aged 0-25 years with a rare disease showing clinically relevant anxiety symptoms, were assigned to either the WEP-CARE (n = 38) or treatment as usual (n = 36) condition within a randomized controlled trial. The primary outcome measure was parental anxiety, assessed with the Generalized Anxiety Disorder Questionnaire (GAD-7). Secondary outcomes were fear of disease progression, depression, coping, quality of life and user satisfaction. The group differences were tested through repeated-measures analyses of variance. The WEP-CARE group was additionally followed up three months after the treatment. RESULTS: A significant time-group interaction was found for anxiety (F (1,35) = 6.13, p = .016), fear of disease progression (F (1,331) = 18.23, p < .001), depression (F (1,74) = 10.79, p = .002) and coping (F (1,233) = 7.02, p = .010), suggesting superiority of the WEP-CARE group. Sustainability of the treatment gains regarding anxiety, fear of disease progression and coping was confirmed at the 6-month follow-up assessment (p < .01). A significant interaction effect could not be found for quality of life (F(1,2) = 0.016; p = .899). Both participating parents and therapists were satisfied with WEP-CARE. CONCLUSIONS: Our results underline the efficacy and feasibility of WEP-CARE for parents of children with various rare diseases.

Effects of elexacaftor/tezacaftor/ivacaftor therapy on mental health of patients with cystic fibrosis.

Introduction: The CFTR modulator drug elexacaftor/tezacaftor/ivacaftor (ETI) was shown to improve CFTR function and clinical symptoms in patients with cystic fibrosis (CF) with at least one F508del allele. Recently, some case reports suggested potential side effects of ETI on mental health with an increase in depressive symptoms and even suicide attempts in patients with CF. However, the general effects of this triple combination therapy on the mental health status of patients with CF remain largely unknown. Methods: We, therefore, performed a prospective, observational study in a real-life setting and investigated the relationship between initiation of ETI therapy and changes in mental health in adult patients with CF. We assessed Cystic Fibrosis Questionnaire-Revised (CFQ-R), Patient Health Questionnaire-9 (PHQ-9), Beck's Depression Inventory - Fast Screen (BDI-FS) and Generalized Anxiety Disorder 7-item Scale (GAD-7) at baseline and 8-16 weeks after initiation of ETI. Results: In total, 70 adult patients with CF with at least one F508del allele and a median age of 27.9 years were recruited. After initiation of ETI, the CFQ-R respiratory domain score improved by 27.9 (IQR 5.6 to 47.2; p < 0.001). The PHQ-9 score of depressive symptoms decreased by 1.0 (IQR -3.0 to 0.3; p < 0.05) with an increase of 16.9% in the group with a minimal score after initiation of ETI and a decrease in the groups of mild (-11.3%) or moderate (-5.7%) scores compared to baseline. The BDI-FS score of depressive symptoms decreased from 1.0 (IQR 0.0-2.0) at baseline to 0.0 (IQR 0.0 to 2.0; p < 0.05) after initiation of ETI. The group with a minimal BDI-FS score increased by 8.0% after initiation of ETI, whereas the groups with mild (-4.9%), moderate (-1.6%) or severe (-1.6%) scores decreased compared to baseline. The GAD-7 score of anxiety symptoms did not change after initiation of ETI compared to baseline (0.0; IQR -2.0. to 0.0; p = 0.112). Conclusion: Initiation of ETI improves symptoms of depression in adult patients with CF with at least one F508del allele. However, symptoms of anxiety do not change after short-term therapy with ETI.

Cross-reactivity of human monoclonal antibodies with canine peripheral blood mononuclear cells.

In drug development, the dog is often used as a model for non-rodent preclinical safety studies. In particular, immunophenotyping in dogs can be important to characterize the toxicological profile of a test item. A wide range of antibodies specific to surface antigens is needed, however, commercially available antibodies to dog are scarce. To date, numerous studies have reported the cross-reactivity of human monoclonal antibodies with canine peripheral blood mononuclear cells (PBMC). In this study, we aimed to increase the number of canine-specific antibodies and took a rather novel approach to further determine cross-reactivity of 378 human recombinant antibodies lacking Fc regions to surface antigens on canine PBMC. The screening resulted in 30 human monoclonal antibodies well reactive to canine PBMC. Sequence homology of the targeted human and canine antigens was analyzed with Basic Local Alignment Search Tool. Thirteen human cross-reactive antibodies of interest were analyzed with cells from canine whole blood in combination with lineage markers. Finally, ten antibodies were identified as useful markers for the application in dog. Except for CD27, the remaining nine antibodies are already commercially available human cross-reactive antibodies. This study provides a new source for all ten antibodies described here.

Development and evaluation of a patient education programme for children, adolescents, and young adults with differences of sex development (DSD) and their parents: study protocol of Empower-DSD.

BACKGROUND: Differences in sexual development (DSD) are rare diseases, which affect the chromosomal, anatomical or gonadal sex differentiation. Although patient education is recommended as essential in a holistic care approach, standardised programmes are still lacking. The present protocol describes the aims, study design and methods of the Empower-DSD project, which developed an age-adapted multidisciplinary education programme to improve the diagnosis-specific knowledge, skills and empowerment of patients and their parents. METHODS: The new patient education programme was developed for children, adolescents and young adults with congenital adrenal hyperplasia, Turner syndrome, Klinefelter syndrome or XX-/or XY-DSD and their parents. The quantitative and qualitative evaluation methods include standardised questionnaires, semi-structured interviews, and participatory observation. The main outcomes (assessed three and six months after the end of the programme) are health-related quality of life, disease burden, coping, and diagnosis-specific knowledge. The qualitative evaluation examines individual expectations and perceptions of the programme. The results of the quantitative and qualitative evaluation will be triangulated. DISCUSSION: The study Empower-DSD was designed to reduce knowledge gaps regarding the feasibility, acceptance and effects of standardised patient education programmes for children and youth with DSD and their parents. A modular structured patient education programme with four generic and three diagnosis-specific modules based on the ModuS concept previously established for other chronic diseases was developed. The topics, learning objectives and recommended teaching methods are summarised in the structured curricula, one for each diagnosis and age group. At five study centres, 56 trainers were qualified for the implementation of the training programmes. A total of 336 subjects have been already enrolled in the study. The recruitment will go on until August 2022, the last follow-up survey is scheduled for February 2023. The results will help improve multidisciplinary and integrated care for children and youth with DSD and their families. TRIAL REGISTRATION: German Clinical Trials Register, DRKS00023096 . Registered 8 October 2020 - Retrospectively registered.

Identification of Plasmodium dipeptidyl aminopeptidase allosteric inhibitors by high throughput screening.

Dipeptidyl aminopeptidases (DPAPs) are cysteine proteases that cleave dipeptides from the N-terminus of protein substrates and have been shown to play important roles in many pathologies including parasitic diseases such as malaria, toxoplasmosis and Chagas's disease. Inhibitors of the mammalian homologue cathepsin C have been used in clinical trials as potential drugs to treat chronic inflammatory disorders, thus proving that these enzymes are druggable. In Plasmodium species, DPAPs play important functions at different stages of parasite development, thus making them potential antimalarial targets. Most DPAP inhibitors developed to date are peptide-based or peptidomimetic competitive inhibitors. Here, we used a high throughput screening approach to identify novel inhibitor scaffolds that block the activity of Plasmodium falciparum DPAP1. Most of the hits identified in this screen also inhibit Plasmodium falciparum DPAP3, cathepsin C, and to a lesser extent other malarial clan CA proteases, indicating that these might be general DPAP inhibitors. Interestingly, our mechanism of inhibition studies indicate that most hits are allosteric inhibitors, which opens a completely new strategy to inhibit these enzymes, study their biological function, and potentially develop new inhibitors as starting points for drug development.

Characterization of P. falciparum dipeptidyl aminopeptidase 3 specificity identifies differences in amino acid preferences between peptide-based substrates and covalent inhibitors.

Malarial dipeptidyl aminopeptidases (DPAPs) are cysteine proteases important for parasite development thus making them attractive drug targets. In order to develop inhibitors specific to the parasite enzymes, it is necessary to map the determinants of substrate specificity of the parasite enzymes and its mammalian homologue cathepsin C (CatC). Here, we screened peptide-based libraries of substrates and covalent inhibitors to characterize the differences in specificity between parasite DPAPs and CatC, and used this information to develop highly selective DPAP1 and DPAP3 inhibitors. Interestingly, while the primary amino acid specificity of a protease is often used to develop potent inhibitors, we show that equally potent and highly specific inhibitors can be developed based on the sequences of nonoptimal peptide substrates. Finally, our homology modelling and docking studies provide potential structural explanations of the differences in specificity between DPAP1, DPAP3, and CatC, and between substrates and inhibitors in the case of DPAP3. Overall, this study illustrates that focusing the development of protease inhibitors solely on substrate specificity might overlook important structural features that can be exploited to develop highly potent and selective compounds.

Plasmodium falciparum dipeptidyl aminopeptidase 3 activity is important for efficient erythrocyte invasion by the malaria parasite.

Parasite egress from infected erythrocytes and invasion of new red blood cells are essential processes for the exponential asexual replication of the malaria parasite. These two tightly coordinated events take place in less than a minute and are in part regulated and mediated by proteases. Dipeptidyl aminopeptidases (DPAPs) are papain-fold cysteine proteases that cleave dipeptides from the N-terminus of protein substrates. DPAP3 was previously suggested to play an essential role in parasite egress. However, little is known about its enzymatic activity, intracellular localization, or biological function. In this study, we recombinantly expressed DPAP3 and demonstrate that it has indeed dipeptidyl aminopeptidase activity, but contrary to previously studied DPAPs, removal of its internal prodomain is not required for activation. By combining super resolution microscopy, time-lapse fluorescence microscopy, and immunoelectron microscopy, we show that Plasmodium falciparum DPAP3 localizes to apical organelles that are closely associated with the neck of the rhoptries, and from which DPAP3 is secreted immediately before parasite egress. Using a conditional knockout approach coupled to complementation studies with wild type or mutant DPAP3, we show that DPAP3 activity is important for parasite proliferation and critical for efficient red blood cell invasion. We also demonstrate that DPAP3 does not play a role in parasite egress, and that the block in egress phenotype previously reported for DPAP3 inhibitors is due to off target or toxicity effects. Finally, using a flow cytometry assay to differentiate intracellular parasites from extracellular parasites attached to the erythrocyte surface, we show that DPAP3 is involved in the initial attachment of parasites to the red blood cell surface. Overall, this study establishes the presence of a DPAP3-dependent invasion pathway in malaria parasites.

[How are Effects of Patient Education Programs Influenced by Psychosocial Risk Factors in Pediatrics?] / Wie beeinflussen psychosoziale Risiken den Erfolg von Patientenschulungen in der Pädiatrie?

BACKGROUND: Modular patient education programs are effective in children with chronic conditions and their families. Little is known about the influence of socioeconomic status (SES), migration background (MB) and children's mental-health problems on the programs' effects. OBJECTIVES: Do SES, MB or mental-health problems influence the success of education programs (disease-specific knowledge, children's health-related quality of life (HRQoL) and life satisfaction and parents' condition-specific burden)? MATERIALS AND METHODS: Children with different chronic conditions and their parents participated in modular patient education programs. Before and 6 weeks after the participation SES, MB, children's mental-health problems, parents' und children's disease-specific knowledge, children's HRQoL and life satisfaction and parents' condition-specific burden were assessed by standardized questionnaires. The influence on the programs' effects of SoS, MH and mental-health problems were examined with variance and correlation analyses. RESULTS: 398 children (mean age 10.2 yrs) and their parents participated. Irrespective of SoS, MH and mental-health problems the programs were associated with improved disease-specific knowledge, children's HRQoL and life satisfaction and parents' disease-specific burden. At follow-up SoS, MH and mental-health problems were associated with reduced knowledge, reduced children's' HRQoL and life satisfaction and increased parents' disease-specific burden. CONCLUSIONS: Disadvantaged families and children with mental-health problems benefit from education programs, but have an increased need of education due to special challenges.

Deletion of the rodent malaria ortholog for falcipain-1 highlights differences between hepatic and blood stage merozoites.

Proteases have been implicated in a variety of developmental processes during the malaria parasite lifecycle. In particular, invasion and egress of the parasite from the infected hepatocyte and erythrocyte, critically depend on protease activity. Although falcipain-1 was the first cysteine protease to be characterized in P. falciparum, its role in the lifecycle of the parasite has been the subject of some controversy. While an inhibitor of falcipain-1 blocked erythrocyte invasion by merozoites, two independent studies showed that falcipain-1 disruption did not affect growth of blood stage parasites. To shed light on the role of this protease over the entire Plasmodium lifecycle, we disrupted berghepain-1, its ortholog in the rodent parasite P. berghei. We found that this mutant parasite displays a pronounced delay in blood stage infection after inoculation of sporozoites. Experiments designed to pinpoint the defect of berghepain-1 knockout parasites found that it was not due to alterations in gliding motility, hepatocyte invasion or liver stage development and that injection of berghepain-1 knockout merosomes replicated the phenotype of delayed blood stage growth after sporozoite inoculation. We identified an additional role for berghepain-1 in preparing blood stage merozoites for infection of erythrocytes and observed that berghepain-1 knockout parasites exhibit a reticulocyte restriction, suggesting that berghepain-1 activity broadens the erythrocyte repertoire of the parasite. The lack of berghepain-1 expression resulted in a greater reduction in erythrocyte infectivity in hepatocyte-derived merozoites than it did in erythrocyte-derived merozoites. These observations indicate a role for berghepain-1 in processing ligands important for merozoite infectivity and provide evidence supporting the notion that hepatic and erythrocytic merozoites, though structurally similar, are not identical.

Improved management of childhood atopic dermatitis after individually tailored nurse consultations: A pilot study.

BACKGROUND: For optimal therapy of atopic dermatitis (AD) in children, parent education for treatment strategies that consider the episodic course and multiple triggers is essential. Regular consultations with doctors often cannot appropriately provide this. Therefore, supplemental patient education tools have been established. We evaluate single nurse consultations, assessing their global benefit, parents' self-confidence, and children's symptoms and sleep disturbance. METHODS: Parents of children with AD were invited for an individually tailored nurse consultation by the doctor initially consulted in cases where difficulties in implementing care recommendations were detected and established therapeutic patient education (TPE) group programmes were impracticable. Parents' estimation of their own self-confidence, current disease severity and its treatment was assessed by a questionnaire at the consultation and by telephone 14 days later. RESULTS: Parents of 1628 children (mean age 1.7 yr) attended consultations in 22 centres (317-6 patients; median 38). At follow-up parents indicated a significantly increased self-confidence to handle the recommendations and >90% rated the consultation highly supportive. The frequency of severe symptoms was significantly lower (20% of initial cases), as of moderate symptoms (50%). Median scores for sleep disruption and pruritus decreased by >50%. CONCLUSIONS: Individually tailored single nurse consultations for AD are associated with a significant benefit for the families after 14 days. We recommend these in addition to the usual medical care in cases where participation in TPE programmes is impossible or a short-time follow-up is required. To substantiate their effect, studies with a long-term follow-up and a control group are warranted.

A web-based psychological support program for caregivers of children with cystic fibrosis: a pilot study.

BACKGROUND: Parents caring for a child with Cystic Fibrosis (CF) are at high risk for psychological distress and have limited access to psychological care. Therefore, a web-based psychological support program for severely distressed parents of children with CF (WEP-CARE) was developed and evaluated for its feasibility and efficacy. METHODS: A clinical expert panel developed WEP-CARE based on principles of cognitive-behavioral therapy. This web-based writing therapy comprises nine sessions, tailored for the specific needs of caregivers. The pilot study was conducted as a single-group intervention with pre-post-follow-up design. Out of 31 participants, 23 parents completed the intervention (21 female; mean age 37 years; SD = 6.2 years, range 25 - 48 years). Psychological symptoms and quality of life were assessed online by self-report measures at pre- and post-treatment and were followed up three months later. RESULTS: On average, the caregivers' symptoms of anxiety decreased statistically significant and clinical relevant about five points from an elevated (M = 11.4; SD =2.6) to a normal level (M = 6.7; SD = 2.6; p < .001) between pre and post treatment. Fear of disease progression (p < .001) and symptoms of depression (p = .02) significantly decreased as well. Quality of life significantly improved (p = .01). The effects were maintained at the 3-months follow-up assessment. CONCLUSIONS: WEP-CARE is feasible and promising regarding its efficacy to improve parental mental health and quality of life.

A cysteine protease inhibitor of plasmodium berghei is essential for exo-erythrocytic development.

Plasmodium parasites express a potent inhibitor of cysteine proteases (ICP) throughout their life cycle. To analyze the role of ICP in different life cycle stages, we generated a stage-specific knockout of the Plasmodium berghei ICP (PbICP). Excision of the pbicb gene occurred in infective sporozoites and resulted in impaired sporozoite invasion of hepatocytes, despite residual PbICP protein being detectable in sporozoites. The vast majority of these parasites invading a cultured hepatocyte cell line did not develop to mature liver stages, but the few that successfully developed hepatic merozoites were able to initiate a blood stage infection in mice. These blood stage parasites, now completely lacking PbICP, exhibited an attenuated phenotype but were able to infect mosquitoes and develop to the oocyst stage. However, PbICP-negative sporozoites liberated from oocysts exhibited defective motility and invaded mosquito salivary glands in low numbers. They were also unable to invade hepatocytes, confirming that control of cysteine protease activity is of critical importance for sporozoites. Importantly, transfection of PbICP-knockout parasites with a pbicp-gfp construct fully reversed these defects. Taken together, in P. berghei this inhibitor of the ICP family is essential for sporozoite motility but also appears to play a role during parasite development in hepatocytes and erythrocytes.

Absorptive chemistry based extraction for LC-MS/MS analysis of small molecule analytes from biological fluids - an application for 25-hydroxyvitamin D.

BACKGROUND: Already available sample preparation technologies for liquid chromatography-tandem mass spectrometry have substantial shortcomings with respect to automation. A novel approach is based on gel-like polymeric material with defined absorption chemistry, which is immobilized in micro-plate wells. It is referred to as Tecan Immobilized Coating Extraction™ (TICE™) technology and it enables easy automation on liquid handling systems. We aimed to study the performance of Tecan AC Extraction Plate™ based on this principle by addressing 25-hydroxyvitamin D (25OHD) as an exemplary analyte. METHODS: A protocol for extraction of 25OHD from serum samples based on TICE™ technology was implemented on a robotic liquid handling system Freedom EVO® (Tecan). An isotope-dilution ultra-performance liquid chromatography-tandem mass spectrometry method was used for quantification. Performance was tested according to a comprehensive protocol. RESULTS: Linearity was found over a range from 4.3 to 65.8 ng/mL for 25OHD3. The coefficients of variation for the intra-day and inter-day precision were <6% and accuracy ranged between 96.9% and 99.8% for 25OHD3. Recovery was 84% and efficient control of matrix effects was verified. High sample throughput could be observed with 96 samples prepared in <60 min. Close agreement of results was found for clinical samples analyzed with a second tandem mass spectrometry method based on protein precipitation and two-dimensional ultra-performance liquid chromatography for sample preparation (r=0.988, n=73). CONCLUSIONS: The new TICE™ technology was found to be a useful process for sample preparation in clinical mass spectrometry. Full automation suited for routine analysis was achieved.

Evolution and architecture of the inner membrane complex in asexual and sexual stages of the malaria parasite.

The inner membrane complex (IMC) is a unifying morphological feature of all alveolate organisms. It consists of flattened vesicles underlying the plasma membrane and is interconnected with the cytoskeleton. Depending on the ecological niche of the organisms, the function of the IMC ranges from a fundamental role as reinforcement system to more specialized roles in motility and cytokinesis. In this article, we present a comprehensive evolutionary analysis of IMC components, which exemplifies the adaptive nature of the IMCs' protein composition. Focusing on eight structurally distinct proteins in the most prominent "genus" of the Alveolata-the malaria parasite Plasmodium-we demonstrate that the level of conservation is reflected in phenotypic characteristics, accentuated in differential spatial-temporal patterns of these proteins in the motile stages of the parasite's life cycle. Colocalization studies with the centromere and the spindle apparatus reveal their discriminative biogenesis. We also reveal that the IMC is an essential structural compartment for the development of the sexual stages of Plasmodium, as it seems to drive the morphological changes of the parasite during the long and multistaged process of sexual differentiation. We further found a Plasmodium-specific IMC membrane matrix protein that highlights transversal structures in gametocytes, which could represent a genus-specific structural innovation required by Plasmodium. We conclude that the IMC has an additional role during sexual development supporting morphogenesis of the cell, which in addition to its functions in the asexual stages highlights the multifunctional nature of the IMC in the Plasmodium life cycle.

Somatoform respiratory disorders in children and adolescents-proposals for a practical approach to definition and classification.

Somatoform respiratory disorders represent conditions with dysfunctional breathing unexplained by structural abnormalities. This heterogeneous group includes disorders with neural dysregulation of respiration (vocal cord dysfunction) or with dysregulation of the respiratory pattern (hyperventilation, sighing dyspnea), psychogenic disorders such as unjustified anxiety of suffocation, and stereotype conditions such as throat clearing or habit cough. Many symptoms are nonspecific and largely overlap with respiratory disease symptoms of somatic etiology. Most patients will present in a nonspecialized clinical setting. This article provides symptom-based criteria for the definition of somatoform respiratory disorders and their differentiation from somatic disease. Emphasis is put on clinical criteria which can be easily integrated in a routine setting. Owing to the multifaceted etiology of somatoform respiratory disorders therapeutic approaches integrating somatic medicine, respiratory therapy and psychology are crucial. The introduction of defined clinical criteria may facilitate the discrimination of somatoform respiratory disorders from somatic disorders in routine patient encounters and avoid therapeutic detours.

Hostile takeover by Plasmodium: reorganization of parasite and host cell membranes during liver stage egress.

The protozoan parasite Plasmodium is transmitted by female Anopheles mosquitoes and undergoes obligatory development within a parasitophorous vacuole in hepatocytes before it is released into the bloodstream. The transition to the blood stage was previously shown to involve the packaging of exoerythrocytic merozoites into membrane-surrounded vesicles, called merosomes, which are delivered directly into liver sinusoids. However, it was unclear whether the membrane of these merosomes was derived from the parasite membrane, the parasitophorous vacuole membrane or the host cell membrane. This knowledge is required to determine how phagocytes will be directed against merosomes. Here, we fluorescently label the candidate membranes and use live cell imaging to show that the merosome membrane derives from the host cell membrane. We also demonstrate that proteins in the host cell membrane are lost during merozoite liberation from the parasitophorous vacuole. Immediately after the breakdown of the parasitophorous vacuole membrane, the host cell mitochondria begin to degenerate and protein biosynthesis arrests. The intact host cell plasma membrane surrounding merosomes allows Plasmodium to mask itself from the host immune system and bypass the numerous Kupffer cells on its way into the bloodstream. This represents an effective strategy for evading host defenses before establishing a blood stage infection.

Identification and characterization of a liver stage-specific promoter region of the malaria parasite Plasmodium.

During the blood meal of a Plasmodium-infected mosquito, 10 to 100 parasites are inoculated into the skin and a proportion of these migrate via the bloodstream to the liver where they infect hepatocytes. The Plasmodium liver stage, despite its clinical silence, represents a highly promising target for antimalarial drug and vaccine approaches. Successfully invaded parasites undergo a massive proliferation in hepatocytes, producing thousands of merozoites that are transported into a blood vessel to infect red blood cells. To successfully develop from the liver stage into infective merozoites, a tight regulation of gene expression is needed. Although this is a very interesting aspect in the biology of Plasmodium, little is known about gene regulation in Plasmodium parasites in general and in the liver stage in particular. We have functionally analyzed a novel promoter region of the rodent parasite Plasmodium berghei that is exclusively active during the liver stage of the parasite. To prove stage-specific activity of the promoter, GFP and luciferase reporter assays have been successfully established, allowing both qualitative and accurate quantitative analysis. To further characterize the promoter region, the transcription start site was mapped by rapid amplification of cDNA ends (5'-RACE). Using promoter truncation experiments and site-directed mutagenesis within potential transcription factor binding sites, we suggest that the minimal promoter contains more than one binding site for the recently identified parasite-specific ApiAP2 transcription factors. The identification of a liver stage-specific promoter in P. berghei confirms that the parasite is able to tightly regulate gene expression during its life cycle. The identified promoter region might now be used to study the biology of the Plasmodium liver stage, which has thus far proven problematic on a molecular level. Stage-specific expression of dominant-negative mutant proteins and overexpression of proteins normally active in other life cycle stages will help to understand the function of the proteins investigated.

Exoerythrocytic Plasmodium parasites secrete a cysteine protease inhibitor involved in sporozoite invasion and capable of blocking cell death of host hepatocytes.

Plasmodium parasites must control cysteine protease activity that is critical for hepatocyte invasion by sporozoites, liver stage development, host cell survival and merozoite liberation. Here we show that exoerythrocytic P. berghei parasites express a potent cysteine protease inhibitor (PbICP, P. berghei inhibitor of cysteine proteases). We provide evidence that it has an important function in sporozoite invasion and is capable of blocking hepatocyte cell death. Pre-incubation with specific anti-PbICP antiserum significantly decreased the ability of sporozoites to infect hepatocytes and expression of PbICP in mammalian cells protects them against peroxide- and camptothecin-induced cell death. PbICP is secreted by sporozoites prior to and after hepatocyte invasion, localizes to the parasitophorous vacuole as well as to the parasite cytoplasm in the schizont stage and is released into the host cell cytoplasm at the end of the liver stage. Like its homolog falstatin/PfICP in P. falciparum, PbICP consists of a classical N-terminal signal peptide, a long N-terminal extension region and a chagasin-like C-terminal domain. In exoerythrocytic parasites, PbICP is posttranslationally processed, leading to liberation of the C-terminal chagasin-like domain. Biochemical analysis has revealed that both full-length PbICP and the truncated C-terminal domain are very potent inhibitors of cathepsin L-like host and parasite cysteine proteases. The results presented in this study suggest that the inhibitor plays an important role in sporozoite invasion of host cells and in parasite survival during liver stage development by inhibiting host cell proteases involved in programmed cell death.