Biomedical subjects
Publications and source records attributed to T Jelinek.
In a survey among febrile European tourists in Kenya, only 68% were able to carry out immunochromatographic dipstick tests for detection of Plasmodium falciparum antigen correctly, and ten of 11 with malaria failed to diagnose themselves correctly. Rapid tests for self-diagnosis by tourists cannot be recommended without appropriate training before departure.
The 14-3-3 proteins interact with diverse cellular molecules involved in various signal transduction pathways controlling cell proliferation, transformation, and apoptosis. To aid our investigation of the biological function of 14-3-3 proteins, we have set out to identify high-affinity antagonists. By screening phage display libraries, we have identified a set of peptides which bind 14-3-3 proteins. One of these peptides, termed R18, exhibited a high affinity for different isoforms of 14-3-3 with estimated K(D) values of 7-9 x 10(-)(8) M. Recognition of multiple isoforms of 14-3-3 suggests the targeting of R18 to a structure that is common among 14-3-3 proteins, such as the conserved ligand-binding groove. Indeed, mutations that alter critical residues in the ligand-binding site of 14-3-3 drastically decreased the level of 14-3-3-R18 association. R18 efficiently blocked the binding of 14-3-3 to the kinase Raf-1, a physiological ligand of 14-3-3, and effectively abolished the protective role of 14-3-3 against phosphatase-induced inactivation of Raf-1. The cocrystal structure of R18 in complex with 14-3-3zeta revealed the occupancy of the general binding groove of 14-3-3zeta by R18, explaining the potent inhibitory effect of R18 on 14-3-3-ligand interactions. Such a well-defined peptide will be an effective tool for probing the role of 14-3-3 in various signaling pathways, and may lead to the development of 14-3-3 antagonists with pharmacological applications.
HISTORY AND CLINICAL FINDINGS: A 57-year-old patient presented with malaise and severe persistent arthralgia of the left shoulder. He reported an acute illness with fever, generalized myalgia and arthralgias of the large joints which had started one month earlier during his flight back to Germany after a two weeks trip to the South Pacific. Physical examination showed extensive pain on palpation of the glenohumeral and acromioclavicular joints with impairment of active and passive mobility. Investigation of the cervical spine was normal. INVESTIGATIONS: Apart from elevated C-reactive protein and erythrocyte sedimentation rate levels, routine laboratory investigations were normal including negative immunodiagnostic tests for autoantibodies and various global infections that may be associated with arthritis. Immunofluorescence tests showed significant levels of specific IgM- and IgG-antibodies against Ross River virus (RRV) but not against other arboviruses endemic in the South Pacific and Australia (Dengue, West Nile, Chikungunya, Sindbis, Barmah Forest). This was confirmed by a positive RRV neutralisation test. Attempts at virus isolation and detection of viral RNA by PCR were not successful. TREATMENT AND COURSE: Symptomatic treatment with high doses of diclofenac quickly led to pain relief, and arthralgias receded within 10 days after begin of treatment. However, several bouts of arthralgia of the left shoulder and left knee occurred during a period of 4 months. CONCLUSIONS: Because of the current epidemiological situation in the South Pacific and Australia, infections by arboviruses like RRV should be considered in travellers returning from these areas with severe and persistent arthralgia of unknown origin, even in the absence of fever and other symptoms of acute infection.
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A rapid immunochromatographic dipstick test has become available for the qualitative detection of total anti-Leishmania immunoglobulins using the recombinant K39 antigen. To evaluate the test, 96 serum specimens from patients with a variety of tropical infections were tested. Fourteen of the specimens derived from patients with parasitologically confirmed kala-azar, and all were strongly positive for antibodies to Leishmania donovani complex using the immunofluorescence test. Although all 82 samples negative by the immunofluorescence test were confirmed as negative by the dipstick assay, only 10 (71.4%) of the 14 positive samples were reactive. These results indicate that the test in its current form lacks sufficient sensitivity to be recommended as a screening tool, but it might be useful for indicating further diagnostic procedures in a clinical setting.
It has been proposed that polymorphisms of the Merozoite Surface Protein 1 and 2 (MSP1 and MSP2) and the Glutamate Rich Protein (GLURP) genes can be considered as genetic markers for the genotyping of field populations of Plasmodium falciparum. During a field study on in vivo drug resistance against chloroquine, sulphadoxine/pyrimethamine (S/P) and cotrimoxazole in West Uganda, sensitive and resistant isolates were collected from patients by fingerprick for genotyping. 59 (72.8%) of the 81 P. falciparum samples isolated at day 0 showed multiclonal infection with 2-7 clones. Among the isolates we investigated, presence of the allelic family MAD20 of MSP1 at day 0 was significantly (P = 0.0041) associated with decreased resistance to antimalarials. Use of this method in a field study on in vivo drug resistance demonstrates another potential application of genotyping as a tool for epidemiological investigations.
Circumsporozoite (CS) antibodies have been shown to be reliable indicators of malaria transmission in endemic areas. Their prevalence in travelers can indicate the degree of exposure to plasmodial infection. Two hundred sixty-two short-term travelers to Kenya were recruited to a prospective study to determine the incidence of CS antibody conversion. All travelers were receiving malaria chemoprophylaxis. Serum samples were drawn before departure and 4-6 weeks after their return to Germany. Sera from 310 volunteers who did not leave Germany served as controls. Serum specimens from 13 (4.96%) of the 262 travelers were found to be positive after return. None of the travelers developed symptoms of clinical malaria or antibodies against the blood stages of Plasmodium falciparum. All 310 control samples tested negative. These data demonstrate a considerable risk of malaria transmission for short-term travelers to East Africa.
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Swift diagnosis of Plasmodium falciparum malaria in areas where the disease is not endemic is frequently complicated by the lack of experience on the side of involved laboratory personal. Diagnostic tools based on the dipstick principle for the detection of plasmodial histidine-rich protein 2 (HRP-2) and parasite-specific lactate dehydrogenase (pLDH), respectively, have become available for the qualitative detection of P. falciparum malaria. In order to evaluate two of the currently available assays, specimens from 231 patients were screened during a prospective multicenter study. Among the screened specimens, samples from 53 patients (22.9%) were positive for P. falciparum malaria by microscopy and/or PCR. While the test kit based on the detection of HRP-2 performed with a sensitivity of 92.5% and a specificity of 98.3%, the kit for the detection of pLDH showed a sensitivity of 88.5% and a specificity of 99.4%. Dipstick tests have the potential of enhancing speed and accuracy of the diagnosis of P. falciparum malaria, especially if nonspecialized laboratories are involved.
In vivo testing for resistance of Plasmodium falciparum to co-trimoxazole (trimethoprim/sulfamethoxazole) was performed in Uganda in 41 children with uncomplicated malaria, and blood samples were screened before and after treatment for polymorphisms in the antifolate target genes for dihydrofolate reductase (DHFR) and dihydropteroate synthetase (DHPS). Selection towards a specific genotype at some codons of the DHFR and DHPS genes was observed in samples collected after exposure to co-trimoxazole drug pressure. The alleles 51-isoleucine, 59-arginine, and 108-serine of DHFR were significantly associated with clinical resistance, as was allele 581-alanine of DHPS. Resistance against antifolate combinations probably requires resistance-related polymorphisms in both the DHFR and the DHPS genes. In addition, it appears that the trimethoprim-resistant DHFR genotype differs from that for pyrimethamine at residue 108.
The efficacy of sulfadoxine/pyrimethamine (S/P) in treatment of uncomplicated falciparum malaria in Africa is increasingly compromised by development of resistance. The occurrence of active site mutations in the Plasmodium falciparum gene sequences coding for dihydrofolate reductase (DHFR) and dihydropteroate synthetase (DHPS) is known to confer resistance to pyrimethamine and sulfadoxine. This study investigated the occurrence of these mutations in infected blood samples taken from Ugandan children before treatment with S/P and their relationship to parasite breakthrough by day 7. The results confirm the occurrence of mutations in DHFR and DHPS that were significantly selected under S/P pressure at day 7: a combination of alleles 51-isoleucine and 108-asparagine in DHFR, and 436-serine, 437-alanine, 540-lysine and 581-alanine in DHPS, appears to play a major role in the development of in vivo resistance in P. falciparum strains against S/P. Therefore, earlier results derived from isolates from hyperendemic areas in Tanzania were confirmed by this investigation.
OBJECTIVE: To investigate the effectiveness of chemoprophylaxis and the determinants of malaria importation from Kenya. METHOD: In a population-based case-control study, 51 travellers from Bavaria diagnosed with falciparum malaria imported from Kenya (cases) and a sample of 383 healthy Bavarian travellers returning from Kenya (controls) were interviewed. Data were analysed by multiple logistic regression. RESULTS: Mefloquine (OR = 0.055; 95% CI 0.019-0.16) and chloroquine combined with proguanil (OR = 0.128; 95% CI 0.039-0.419) were highly protective against P. falciparum malaria, whereas other drugs were ineffective (OR = 1.225; 95% CI 0.536-2.803). Ineffective prophylaxis (10.4%) and non-prophylaxis (11.2%) were the main reasons for malaria importation. Travelling alone or with friends, male sex, and travel duration over 4 weeks could be identified as additional risk factors. The main reason for inadequate chemoprophylaxis was inappropriate medical advice (87.5%). Prophylaxis refusal occurred frequently despite correct advice (58.1%). Diagnosis was often delayed unnecessarily (27.5%). CONCLUSION: Malaria importation from Kenya could be reduced substantially (34%) by eliminating inappropriate medical advice.
The efficacy of sulphadoxine/pyrimethamine (S/P) in treatment of uncomplicated falciparum malaria in Africa is increasingly compromised by development of resistance. The occurrence of mutations associated with the active site sequence in the Plasmodium falciparum genes coding for dihydrofolate reductase (DHFR) and dihydropteroate synthetase (DHPS) is associated with in vitro resistance to pyrimethamine and sulphadoxine. This study investigates the occurrence of these mutations in infected blood samples taken from Tanzanian children before treatment with S/P and their relationship to parasite breakthrough by day 7. The results show that alleles of DHPS (436-alanine, 437-alanine and 540-lysine) were significantly reduced in prevalence on day 7 after S/P treatment. In this area, a DHPS with 436-serine, 437-glycine and 540-glutamate appears to play a major role in resistance to S/P in vivo. Evidence for the influence of mutations in the DHFR gene in this investigation is not clear, probably because of the high prevalence of 'resistance-related' mutations at day 0 in the local parasite population. For apparently the same reason, it was not possible to show a statistical association between S/P resistance and the presence of particular polymorphisms in the DHFR and DHPS genes before treatment.
Most knowledge about the synthesis of human tumor necrosis factor (TNF)-alpha and its regulation derives from in vitro studies. The hypothesis that the syndrome of malaise, myalgia, and low fever observed after a vaccination with live attenuated yellow fever virus could be associated with increased synthesis of TNF was investigated. Plasma samples of 15 healthy subjects taken before and until day 2 (until day 11 in 5 of these subjects) after yellow fever vaccination, showed a significant increase of plasma TNF concentration on day 2 after vaccination and a second peak on day 7. Interleukin-1 receptor antagonist (IL-1ra) concentration was significantly elevated in all subjects on day 2 after vaccination. In a control group receiving non-live vaccinations, TNF and IL-1ra concentrations were unchanged. Thus, yellow fever vaccination represents a routine medical intervention that results in a reproducible increase in the plasma concentration of TNF and secondary cytokines. This may serve as a unique model for the study of the regulation of TNF synthesis in vivo.
Circumsporozoite (CS) antibodies, indicating plasmodial infection but not necessarily development of disease, have been shown to be reliable indicators of transmission in endemic areas. To estimate the actual rate of plasmodial infection, the prevalence of CS antibodies was investigated by an ELISA test system in a selected population of 2,131 travelers returning from areas endemic for malaria who presented to an outpatient clinic without any apparent symptom or clinical sign of malaria. Serum specimens from 104 of the investigated 2,131 patients (4.9%) were found to be positive (titer > or = 6.25 international ELISA units [IEU]). The geometric mean titer of antibody concentrations (IEU) in seropositive patients was 18.64 IEU (95% confidence interval [CI] = 13.15-24.13), while it was 2.1 IEU (95% CI = 1.8-2.4) in seronegative patients. A significantly above average risk for plasmodial infection could be found among travelers to East Africa (risk ratio [RR] = 4.5, P < 0.001), West Africa (RR = 4.5, P < 0.001), and Southern Africa (RR = 3.2, P = 0.015), while areas with a comparatively low risk included Central America (RR = 0.86, P < 0.001), the Indian subcontinent (RR = 0.45, P = 0.015), South America (RR = 0.49, P = 0.091), East Asia (RR = 0.68, P = 0.441), West Asia (RR = 0.24, P = 0.099), and Southeast Asia (RR = 0.69, P = 0.094). The results of this study emphasize the importance of adequate malaria chemoprophylaxis in nonimmune travelers to endemic areas. By use of the described method, estimates of the true infection rate of malaria in travelers can be derived for certain areas and the value of prophylactic measures can be demonstrated.
Dengue is an acute, mosquito-transmitted viral disease characterized by fever, arthralgia, myalgia, rash, nausea, and vomiting and caused by any of four different serotypes of the virus (DEN-1, DEN-2, DEN-3, and DEN-4).1 The disease is endemic in most tropical areas of the world and has been reported in international travelers returning from such areas.2 The incidence of epidemic and endemic dengue has increased substantially in the Americas since 1977, and various epidemics have occurred.1-4
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BACKGROUND: Dengue has been recognized as a potential hazard to tourists. A prospective, controlled study in the outpatient clinic of a German infectious disease clinic was conducted to assess the prevalence of dengue virus infection among international travelers. METHODS: Serum samples from 130 patients with signs or recent history clinically compatible with dengue (fever, headache, muscle and joint pain, or rash), 95 matched controls with diarrhea, and 26 patients who never visited a country endemic for dengue were investigated. RESULTS: Nine (6.9%) of the 130 patients with compatible symptoms and 1 (1%) of the 95 controls with diarrhea developed rising antibody titers against dengue virus. Of these 10 patients with probable dengue infection, 6 had been to Thailand, 2 to Malaysia, and 1 each to Indonesia and Brazil. CONCLUSIONS: Infection with dengue virus appears to be a realistic threat to travelers to Southeast Asia. Symptoms commonly associated with dengue, such as fever, myalgia, arthralgia, and vomiting, can be helpful for diagnosis when present, but the absence of typical symptoms does not exclude infection.