Biomedical subjects

V Lejon

Publications and source records attributed to V Lejon.

At least 19 recordsLinked to original sources

PubMed2006

Aparasitemic serological suspects in Trypanosoma brucei gambiense human African trypanosomiasis: a potential human reservoir of parasites?

The serological and parasitological tests used for Trypanosoma brucei gambiense human African trypanosomiasis (HAT) diagnosis have low specificity and sensitivity, respectively, and in the field, control program teams are faced with subjects with positive serology but negative parasitology who remain untreated. The aim of this work was to explore, using PCR tool, the significance of these aparasitemic serological suspects. Since discordant PCR results have been observed earlier with different extraction methods, two DNA extraction methods were compared (the Chelex 100 resin and the DNeasy Tissue kit). The study was conducted on 604 blood samples: 574 from parasitologically confirmed patients, aparasitemic serological suspects and endemic controls collected in Côte d'Ivoire and 30 from healthy volunteers collected in France. No significant differences were observed between the PCR results obtained with the two extraction methods. Concerning PCR, problems of reproducibility and discordances with both serological and parasitological test results were observed, mainly for the aparasitemic serological suspects. In addition to previous results that pointed to the existence of non-virulent or non-pathogenic trypanosome strains and of individual susceptibility leading to long term seropositivity without detectable parasitaemia but positive PCR, the results of this study support the notion of a long lasting human reservoir that may contribute to the maintenance or periodic resurgences of HAT in endemic foci.

Agglutination Tests↗

PubMed2006

Detection of trypanosome-specific antibodies in saliva, towards non-invasive serological diagnosis of sleeping sickness.

OBJECTIVE: The detection of trypanosome-specific antibodies in saliva is technically feasible, and, if clinically validated, could become an attractive option for non-invasive diagnosis of sleeping sickness. We wanted to optimize the test format of an enzyme-linked immunosorbent assay (ELISA)-based antibody detection system. METHODS: Different ELISA formats for antibody detection in serum and saliva were developed and standardized. Saliva and serum samples were collected from 78 patient and 128 endemic control samples, and sensitivity and specificity of saliva ELISAs, serum ELISAs and the card agglutination test for trypanosomiasis (CATT), were evaluated. RESULTS: All ELISA formats showed sensitivity and specificity above 90%. Saliva ELISAs showed a similar test performance as serum ELISAs and the CATT on whole blood or serum. CONCLUSIONS: This study confirms the potential of trypanosome-specific antibody detection in saliva.

Agglutination Tests↗

PubMed2005

Recombinant RoTat 1.2 variable surface glycoprotein as antigen for diagnosis of Trypanosoma evansi in dromedary camels.

The transcript encoding a predominant Trypanosoma evansi variable surface glycoprotein RoTat 1.2 was cloned and expressed as a recombinant protein in Spodoptera frugiperda and Trichoplusia ni (insect) cells. Its potential as an antigen for specific detection of antibody in serum of dromedary camels affected by surra, was evaluated. In ELISA, the reactivity of the recombinant RoTat 1.2 VSG was similar to that of native RoTat 1.2 VSG. An indirect agglutination reagent was therefore prepared by coupling the recombinant RoTat 1.2 VSG onto latex particles. The performance of the latex agglutination test was evaluated on camel sera, and compared with the performance of CATT/T. evansi and LATEX/T. evansi tests, using the immune trypanolysis assay with T. evansi RoTat 1.2 as a reference test. The relative sensitivity and specificity of the latex coated with recombinant RoTat 1.2 VSG, using a 1:4 serum dilution, were respectively, 89.3 and 99.1%. No differences were observed between the performance of latex coated with recombinant RoTat 1.2 VSG and LATEX/T. evansi or CATT/T. evansi. Here, we describe the successful use of the recombinant RoTat 1.2 VSG for detection of specific antibodies induced by T. evansi infections.

Animals↗

PubMed2005

Review Article: cerebrospinal fluid in human African trypanosomiasis: a key to diagnosis, therapeutic decision and post-treatment follow-up.

Human African trypanosomiasis is a lethal parasitic infection with neurological involvement. Examination of the cerebrospinal fluid (CSF) plays an essential role in diagnosis, selection of treatment and post-treatment follow-up. This paper reviews clinical presentation, diagnosis and treatment of the disease, with emphasis on CSF characteristics and interpretation of the CSF results for therapeutic decision and post-treatment follow-up.

Animals↗

PubMed2003

The challenge of Trypanosoma brucei gambiense sleeping sickness diagnosis outside Africa.

Sleeping sickness is a lethal African disease caused by parasites of the Trypanosoma brucei subspecies, which is transmitted by tsetse flies. Occasionally, patients are reported outside Africa. Diagnosis of such imported cases can be problematic when the infection is due to Trypanosoma brucei gambiense, the chronic form of sleeping sickness found in west and central Africa. The low number of trypanosomes in the blood and the non-specific, variable symptoms make the diagnosis difficult, particularly when the index of suspicion is low. When the trypanosomes have penetrated into the central nervous system, neuropathological signs become apparent but even at this stage, misdiagnosis is frequent. Rapid and correct diagnosis of sleeping sickness can avoid inappropriate or delayed treatment and even death of the patient. In this article, an overview on diagnosis of imported cases of T b gambiense sleeping sickness is given, and possible pitfalls in the diagnostic process are highlighted. Bioclinical parameters that should raise the suspicion of sleeping sickness in a patient who has been in west or central Africa are discussed. Techniques for diagnosis are reviewed. A clinician suspecting sleeping sickness should contact a national reference centre for tropical medicine in his or her country, or the WHO, Geneva, Switzerland, or the Centers for Disease Control and Prevention (CDC), Atlanta, GA, USA, for clinical consultation and provision of specific diagnostic tests. Appropriate drugs for sleeping sickness treatment are also provided by WHO and the CDC.

Animals↗

PubMed2003

Towards saliva-based screening for sleeping sickness?

A pilot study was carried out on the detection of trypanosome-specific antibodies in saliva for diagnosis of sleeping sickness. All twenty-three saliva samples of parasitologically confirmed Trypanosoma brucei gambiense patients tested positive in an indirect enzyme-linked immunosorbent assay, whereas all 14 saliva samples of a negative control group remained negative. Trypanosome-specific antibody levels in patient saliva correlated with antibody levels in serum, but were about 250-fold lower. Eight of 23 undiluted saliva samples of sleeping sickness patients tested positive in CATT/T. b. gambiense and two of 23 in LATEX/T. b. gambiense. All fourteen saliva samples of the negative control group were also positive in CATT/T. b. gambiense, as were four of 14 in LATEX/T. b. gambiense. CATT and LATEX were thus inappropriate for antibody detection in saliva. These results indicate that trypanosome-specific antibody detection in saliva is possible. This could lead to the development of a simple, non-invasive, reliable saliva field test for diagnosis of sleeping sickness.

Animals↗

PubMed2003

Stage determination and therapeutic decision in human African trypanosomiasis: value of polymerase chain reaction and immunoglobulin M quantification on the cerebrospinal fluid of sleeping sickness patients in Côte d'Ivoire.

In human African trypanosomiasis (HAT), two disease stages are defined: the first, or haemo-lymphatic stage, and the second, or meningo-encephalitic stage. Stage determination forms the basis of therapeutic decision and is of prime importance, as the drug used to cure second-stage patients has considerable side-effects. However, the tests currently used for stage determination have low sensitivity or specificity. Two new tests for stage determination in the cerebrospinal fluid (CSF) were evaluated on 73 patients diagnosed with HAT in Côte d'Ivoire. The polymerase chain reaction (PCR) detecting trypanosome DNA (PCR/CSF) is an indirect test for trypanosome detection whereas the latex agglutination test detecting immunoglobulin M (LATEX/IgM) is an indicator for neuro-inflammation. Both tests were compared with classically used tests, double centrifugation and white blood cell count of the CSF. PCR/CSF appeared to be the most sensitive test (96%), and may be of use to improve stage determination. However, its value for therapeutic decision appears limited, as patients whose CSF was positive with PCR were successfully treated with pentamidine. This result confirms those of previous works that showed that some patients with trypanosomes in the CSF could be treated successfully with pentamidine. LATEX/IgM, which depending on the cut-off, showed lower sensitivity of 76% and 88%, but higher specificity of 83% and 71% for LATEX/IgM 16 and LATEX/IgM 8 respectively, appears more appropriate for therapeutic decision making.

Animals↗

PubMed2003

Human African trypanosomiasis: quantitative and qualitative assessment of intrathecal immune response.

Quantitative and qualitative techniques for assessment of the intrathecal humoral immune response in human African trypanosomiasis were compared, and their diagnostic potential for detection of the meningo-encephalitic stage of the disease was evaluated. Total and trypanosome specific immunoglobulin G (IgG) and IgM intrathecal synthesis were studied in paired cerebrospinal fluid (CSF) and blood samples of 38 trypanosomiasis patients and in three controls using Reiber's formulae. The presence of CSF-specific oligoclonal IgG and of trypanosome-specific antibodies was determined using iso-electric focusing followed by immunoblotting and antigen-driven immunoblots. The intrathecal IgG fraction (16% positive) and oligoclonal IgG detection (24% positive) were insensitive for detection of an intrathecal humoral immune response. Trypanosome-specific IgG synthesis, reflected by the IgG antibody index (AI) (26% positive), was confirmed by the presence of oligoclonal specific IgG (47% positive), but the latter was more sensitive. Although the detection technique failed for oligoclonal IgM, the intrathecal IgM fraction (42% positive) and the IgM AI (32% positive) indicated that the meningo-encephalitic stage of the disease is characterized by a dominant intrathecal IgM response, which was higher than the IgG response. The highest combination of diagnostic sensitivity and specificity for the meningo-encephalitic stage of trypanosomiasis was observed for quantitative IgM determinations.

Albumins↗

PubMed2002

Susceptibility of trypanotolerant West African Dwarf goats and F1 crosses with the susceptible Sahelian breed to experimental Trypanosoma congolense infection and interactions with helminth infections and different levels of diet.

Forty pure West African Dwarf (WAD) goats and 35 of its F1 crosses with the Sahelian breed were used in a multifactorial experimental design to evaluate the effects of an experimental Trypanosoma congolense infection and interactions with natural helminth infections and different levels of diet on health and productivity of these two breeds. Trypanosome infection caused a severe drop in packed cell volume (PCV), but this was not significantly affected by breed. Neither deworming nor diet had any effect on the course of anaemia after trypanosome infection. The mean score of parasitaemia tended to be higher in crossbreeds than in WAD goats although this was not significant (P>0.05). Similarly, the antibody response to trypanosome infection was not significantly different between breeds. Parasitaemia level was significantly influenced by the level of diet with the group under high supplementation having a higher mean parasitaemia score than the group under low supplementation. Weight loss due to trypanosome infection tended to be greater in crossbreeds than in WAD goats (P>0.05). During this study, there was no difference in mean helminth egg output between crossbred and WAD goats. However, between weeks 4 and 10 after trypanosome infection (corresponding to a period of heavy rainfall and highly infective pastures), the mean egg output was higher in the crossbreeds. The immunosuppressive effect of trypanosome infections was revealed by a lower antibody response to Haemonchus contortus in infected animals compared to the uninfected controls. Trypanosome infection tended to increase strongyle egg output. This study did no reveal any superior trypanotolerance of WAD goats compared to crossbreeds.

Animal Feed↗

PubMed2002

Blood-cerebrospinal fluid barrier and intrathecal immunoglobulins compared to field diagnosis of central nervous system involvement in sleeping sickness.

Diagnosis of central nervous system (CNS) involvement in sleeping sickness is crucial in order to give an appropriate treatment regimen. Neurological symptoms occur late, therefore field diagnosis is based on white blood cell count, total protein concentration and presence of trypanosomes in cerebrospinal fluid (CSF). More sensitive and specific parameters are now available. Blood-CSF barrier (B-CSFB) dysfunction, intrathecal total and specific immunoglobulin synthesis were evaluated in 95 patients with and without obvious meningoencephalitis, and compared to field criteria.B-CSFB dysfunction is a rather late event in the course of CNS involvement and correlates with the presence of trypanosomes, neurological signs and intrathecal polyspecific and specific immune response. IgM intrathecal response and particularly IgM antibody index are early markers of CNS invasion. We showed that 29% of patients with CSF abnormalities but without trypanosome detection in the field had no neuro-immunological response. In contrast, patients with normal CSF according to field diagnosis showed an intrathecal immune response in 31% of the cases.Field diagnosis can therefore fail to determine neurological involvement but can also provide false positive results. Improved criteria including B-CSFB dysfunction and IgM detection are needed in order to provide an adapted treatment regimen.

Albumins↗

PubMed2002

Comparison of different DNA preparation protocols for PCR diagnosis of Human African Trypanosomosis in Côte d'Ivoire.

During a medical survey the sleeping sickness focus in Bonon, Ivory Coast, PCR with Trypanosoma brucei specific primers (TBR 1-2 from Parasitology 99 (1989) 57) was tested on DNA derived from blood samples. DNA purification using a chelating resin was performed either on whole blood or on the buffy coat prepared in two different ways. The preparation based on whole blood performed better than those using the buffy-coat. Using this first method, the sensitivity was 100% on parasitologically confirmed patients, and the specificity was 92%. However, problems of reproducibility of the technique were pointed out, particularly on samples from serologically positive but apparently aparasitemic individuals. It is suggested that the PCR could help in the diagnosis of Human African Trypanosomosis, but the use of other primers should be investigated.

Animals↗

PubMed2002

IgM quantification in the cerebrospinal fluid of sleeping sickness patients by a latex card agglutination test.

An increased IgM concentration in cerebrospinal fluid (CSF), occurring as a consequence of massive intrathecal IgM synthesis, is a marker of interest for diagnosis of the meningo-encephalitic stage in human African trypanosomiasis. However, in current practice, IgM in CSF is not determined because of the lack of a simple and robust test that is applicable in African rural regions where the disease prevails. We describe the development of a sensitive semiquantitative card agglutination test, LATEX/IgM, for IgM quantification in CSF. The test is simple and fast and the lyophilized reagent remains stable even at 45 degrees C. CSF end-titres obtained with LATEX/IgM parallel the IgM concentrations determined by nephelometry and enzyme-linked immunosorbent assay. Detection of intrathecal IgM synthesis is the most sensitive marker for CNS involvement in sleeping sickness. At a cut-off value of >or= 8, the sensitivity and specificity of LATEX/IgM for intrathecal IgM synthesis are 89.4 and 92.7%. As a consequence, patients with LATEX/IgM end-titres >or= 8 are likely to have intrathecal IgM synthesis, thus central nervous system involvement and therefore should be treated accordingly. Further studies should concentrate on the relationship between the LATEX/IgM end-titres, presence of intrathecal IgM synthesis and occurrence of treatment failures in patients treated with pentamidine.

Animals↗

PubMed2002

[Diagnosis of sleeping sickness stage: towards a new approach].

Diagnosis of the neurological disease stage in Trypanosoma brucei (T.b.) gambiense infection is essential to select an optimal chemotherapy. The actual parameters for stage determination, the cerebrospinal fluid (CSF) cell count, total protein concentration and trypanosome detection, are insufficiently specific and sensitive. In order to identify new parameters for stage determination, we studied the neuro-inflammatory immune response in the central nervous system, notably the intrathecal humoral immune response in sleeping sickness patients. The presence of intrathecal IgM synthesis was identified as an excellent marker of central nervous system involvement. However, intrathecal IgM detection cannot be performed under field conditions. As a consequence of the strong intrathecal IgM synthesis, extremely high concentrations of IgM are found in the CSF of sleeping sickness. We therefore developed a latex agglutination field test (LATEX/IgM) indicative for intrathecal IgM synthesis and CNS involvement in sleeping sickness. Based on our observations on the intrathecal immune response and with LATEX/IgM, we propose a new approach for stage determination in sleeping sickness.

Animals↗

PubMed2001

Biological data and clinical symptoms as predictors of astrogliosis and neurodegeneration in patients with second-stage Trypanosoma brucei gambiense sleeping sickness.

Concentrations of glial fibrillary acidic protein (GFAp) and light subunit neurofilament protein (NFL) in cerebrospinal fluid (CSF) were measured in patients with second-stage Trypanosoma brucei gambiense sleeping sickness. Correlations between GFAp and NFL in CSF as markers for astrogliosis and neurodegeneration, and clinical and biological data were investigated. Abnormal levels of GFAp and NFL were significantly associated with increasing CSF cell number and protein concentration, and with the absence of lymph nodes or the absence of trypanosomes in lymph node aspirate. A significant association was found between abnormal NFL and presence of trypanosomes in CSF, abnormal limb movements, difficulties in gait and coordination, and low Karnofsky index. By multivariate analysis, it was shown that increasing CSF cell number, increasing CSF protein concentration, and the absence of lymph nodes or the absence of trypanosomes in the lymph node aspirate were the best predictors for astrogliosis and neurodegeneration among the variables tested. These results demonstrate the importance of CSF cell count and protein determination in assessment of the severity of central nervous system involvement and reinforces the importance of laboratory diagnosis to assess the stage of the disease. The clinical symptoms studied were less useful in predicting astrogliosis or neurodegeneration.

Adolescent↗

PubMed2001

[Diagnosis of human African trypanosomiasis in 2001].

Human African trypanosomiasis is characterized by a non-specific clinical presentation with no consistent, pathognomonic manifestations. However definite diagnosis is necessary to avoid unnecessary therapeutic risks with toxic drugs. Further complicating this situation is the frequent need to achieve field diagnosis in remote locations with limited facilities. Serological tests such as CATT (card agglutination trypanosomiasis test) are useful for initial population screening to identify suspects but are not sufficiently reliable for definitive diagnosis since the variations in sensitivity and specificity have been observed between countries and disease pockets. Parasitological examination is still the only method of definitive diagnosis. Thresholds of trypanosome detection differ from one technique to another, i.e., 10,000 trypanosomes per millilitre (T/ml) for fresh blood smears, 5,000 T/ml for thick drop specimens stained with Giemsa, 500 T/ml for centrifugation in capillary tubes, less than 500 T/ml for the QBC test, and 100 T/ml for the ion exchange minicolumn system. The possibility that the QBC test and minicolumn anion exchange system may go out of production could pose a serious problem for field diagnosis. Decisional algorithms are being developed to optimize use of remaining techniques.

Animals↗

PubMed2001

Stage determination and follow-up in sleeping sickness.

In order to select a correct treatment after primary diagnosis of trypanosomiasis infection, accurate assessment of the disease stage, haemo-lymphatic or meningo-encephalitic, is essential. This is achieved by lumbar puncture and subsequent examination of the cerebrospinal fluid. These examinations have to be repeated during 2 years after treatment, and only after the cerebrospinal fluid has normalized one can decide on complete cure. The currently used cerebrospinal fluid parameters, i.e. white blood cell count, total protein determination and finding of trypanosomes, and practical problems encountered using these parameters are discussed. Alternative markers for stage determination and follow-up include trypanosome specific antibodies, anti-galactocerebroside antibodies and IgM measurement in CSF.

Animals↗

PubMed2000

Follow-up of Card Agglutination Trypanosomiasis Test (CATT) positive but apparently aparasitaemic individuals in Côte d'Ivoire: evidence for a complex and heterogeneous population.

The aetiological diagnosis of human African trypanosomiasis (HAT) is based on the detection of the parasite, but currently available parasitological tests have low sensitivity and are hampered by fluctuating parasitaemia. The identification of seropositive individuals on whom to focus parasitological examination is based on antibody detection by means of the Card Agglutination Trypanosomiasis Test (CATT/T.b.gambiense). A complicating phenomenon is the occurrence of serologically positive but parasitologically unconfirmed results (isolated CATT positivity). This work presents a two-year longitudinal serological, parasitological and molecular follow-up of CATT-positive individuals including repeated examinations of each individual, to study the evolution over time of seropositivity at both the population and the individual levels. At the population level, the rate of seropositivity decreased during the first months of the survey, and afterwards showed remarkable stability. At the individual level, the results reveal the extreme heterogeneity of this population, with subjects showing fluctuating results, others with a short transient CATT positivity, and subjects that maintain their seropositivity over time. The stability of seropositivity and the pattern of results obtained with both immunological and parasitological examinations support the view that individual factors, such as immune response to infection, might be involved in the isolated CATT positivity phenomenon.

Adolescent↗

PubMed1999

Improved latex agglutination test for detection of antibodies in serum and cerebrospinal fluid of Trypanosoma brucei gambiense infected patients.

A rapid latex agglutination test (LATEX/T. b. gambiense) for detection of antibodies in patients infected with Trypanosoma brucei gambiense is presented. The reagent is coated with a mixture of three variable surface antigens of bloodstream form trypanosomes. Two hundred and forty sera and 79 CSF samples from patients with parasitologically confirmed trypanosome infection along with 173 sera and 38 CSF samples from non-trypanosomiasis patients have been tested. At 1:16 serum dilution, test specificity was 99%, while sensitivity ranged from 83.8 to 100% depending on the geographical origin of the samples. Undiluted CSF samples from non-trypanosomiasis and from first stage patients scored negative while 42 out of 66 CSF samples from second stage patients were positive. Stability and reproducibility of the lyophilized reagent were excellent.

Animals↗