Multicentric evaluation of a new real-time PCR assay for quantification of Cryptosporidium spp. and identification of Cryptosporidium parvum and Cryptosporidium hominis.

Cryptosporidium is a protozoan parasite responsible for gastroenteritis, especially in immunocompromised patients. Laboratory diagnosis of cryptosporidiosis relies on microscopy, antigen detection, and nucleic acid detection and analysis. Among the numerous molecular targets available, the 18S rRNA gene displays the best sensitivity and sequence variations between species and can be used for molecular typing assays. This paper presents a new real-time PCR assay for the detection and quantification of all Cryptosporidium species associated with the identification of Cryptosporidium hominis and Cryptosporidium parvum. The sensitivity and specificity of this new PCR assay were assessed on a multicentric basis, using well-characterized Cryptosporidium-positive and -negative human stool samples, and the efficiencies of nine extraction methods were comparatively assessed using Cryptosporidium-seeded stool samples and phosphate-buffered saline samples. A comparison of extraction yields showed that the most efficient extraction method was the Boom technique in association with mechanical grinding, and column extraction showed higher binding capacity than extraction methods based on magnetic silica. Our PCR assay was able to quantify at least 300 oocysts per gram of stool. Satisfactory reproducibility between laboratories was observed. The two main species causing human disease, Cryptosporidium hominis and Cryptosporidium parvum, were identified using a duplex real-time PCR assay with specific TaqMan minor-groove-binding ligand (MGB) probes for the same amplicon. To conclude, this one-step quantitative PCR is well suited to the routine diagnosis of cryptosporidiosis since practical conditions, including DNA extraction, quantification using well-defined standards, and identification of the two main species infecting humans, have been positively assessed.

Evaluation of four commercial rapid immunochromatographic assays for detection of Cryptosporidium antigens in stool samples: a blind multicenter trial.

In a multicenter study, potassium dichromate-preserved stools from patients infected with Cryptosporidium parvum (n = 20), C. hominis (n = 20), and other Cryptosporidium species (n = 10) and 60 controls were examined using four immunochromatographic assays. Assay sensitivity ranged between 50.1% and 86.7% for C. parvum and C. hominis but was <35% for other species.

Assessment of cryptodiag for diagnosis of cryptosporidiosis and genotyping Cryptosporidium species.

The performance of a new commercial PCR-enzyme-linked immunosorbent assay (ELISA) (Cryptodiag; Bio Advance, France) for the diagnosis of cryptosporidiosis and the identification of Cryptosporidium hominis and C. parvum from stool samples was examined. This test is based on PCR amplification of Cryptosporidium DNA extracted from stools, followed by an ELISA based on hybridization with Cryptosporidium sp.-, C. hominis-, or C. parvum-specific probes. In spiking experiments, approximately five oocysts were detected either in water or in stool suspensions while assessing for the efficient removal of stool PCR inhibitors. No cross-reactivity was observed in the detection of C. parvum and C. hominis using the respective specific probes. Thirty-three fecal samples from patients with microscopically proven cryptosporidiosis and 118 from patients with or without other digestive protozoan infections were tested by Cryptodiag, blinded to the results of microscopy. Compared to microscopy, the sensitivity of Cryptodiag was 97.0% (32/33) and 100% (33/33), including the gray zone, and specificity was 98.3% (116/118) and 96.6% (114/118), including the gray zone. Among 34 positive results, Cryptodiag identified 19 due to C. hominis, 8 due to C. parvum, and 7 due to Cryptosporidium spp. Genotyping by Cryptodiag agreed with reference typing methods in 85% of cases of C. parvum or C. hominis infections. Cryptodiag proved to be reliable and sensitive for the diagnosis of cryptosporidiosis. The use of specific probes allowed the identification of C. hominis and C. parvum, i.e., the two main species responsible for human cryptosporidiosis, and rapidly provided information on the possible source of infection.

Occurrence of Pneumocystis jiroveci pneumonia after allogeneic stem cell transplantation: a 6-year retrospective study.

Pneumocystis jiroveci pneumonia (PCP) has become a rare opportunistic infection due to the efficacy of prophylactic regimens. We conducted a 6-year retrospective study at our institution. A total of 13 cases of PCP were diagnosed among 519 patients undergoing allogeneic hematopoietic stem cell transplantation (HSCT) (2.5%). In three patients, PCP occurred within the first 5 months following HSCT. These severely immunocompromised patients were receiving prophylaxis and had concomitant aspergillosis that caused rapid death in two of them. In 10 other patients, PCP occurred a median of 14.5 months after HSCT. In all these patients, PCP prophylaxis had been discontinued, mainly because of the suspected bone-marrow toxicity of the prophylactic regimen. Median CD4+ T cell count was 131/microl at diagnosis. Seven of these 10 patients were receiving immunosuppressive therapy for chronic graft versus host disease and three had a relapse of their hematological malignancy. One patient died from PCP despite high doses of cotrimoxazole. We conclude that PCP is still occurring after allogeneic HSCT, mainly as a late complication in patients in whom PCP prophylaxis had been prematurely discontinued. Long-term PCP prophylaxis should be maintained in patients receiving immunosuppressive drugs, and in those with low CD4+ T cell counts or a relapse of their hematological malignancy.

Predictive value of Toxoplasma gondii antibody titres on the occurrence of toxoplasmic encephalitis in HIV-infected patients. ANRS 005/ACTG 154 Trial Group.

OBJECTIVE: To study the predictive value of anti-Toxoplasma gondii antibody titres for the occurrence of toxoplasmic encephalitis (TE) in HIV-infected patients. METHODS: Data from the placebo arm of a trial of primary prophylaxis for TE (ANRS 005/ACTG 154) were analysed. Patients included had CD4+ cell counts < 200 x 10(6)/l and a positive Toxoplasma serology. Immunoglobulin (Ig) G and IgM Toxoplasma antibody titres at entry were retrospectively determined by enzyme-linked immunosorbent assay and agglutination on serum samples in a single laboratory. Incidence of TE was estimated by Kaplan-Meier method and a Cox model was used to study the predictive value of antibody titres, adjusted for other covariates. RESULTS: All 164 patients studied were positive for IgG antibodies and one had IgM antibodies. After a mean follow-up of 16 months, 31 cases of TE were documented. One-year incidence of TE was significantly higher in patients with IgG titres > or = 150 IU/ml (23.7%) than in patients with titres < 150 IU/ml (7.7%; relative risk, 3.1; P < 0.003). IgG titres remained significantly associated with the occurrence of TE (relative risk, 3.3; P < 0.005) in the Cox model. Predictive value of IgG titres did not differ according to baseline CD4+ cell counts. CONCLUSIONS: In patients with CD4+ cell counts < 200 x 10(6)/l, IgG anti-Toxoplasma antibody titre is a prognostic factor of occurrence of TE, with a higher risk for titres > or = 150 IU/ml. This finding should reinforce the recommendation of specific prophylaxis in these patients.

Diagnosis of infections caused by Enterocytozoon bieneusi and Encephalitozoon intestinalis using polymerase chain reaction in stool specimens.

OBJECTIVE: To study the usefulness of polymerase chain reaction (PCR) for the species identification of microsporidia in stool specimens obtained from HIV-infected patients with Enterocytozoon bieneusi or Encephalitozoon intestinalis infections. SETTING: Infectious disease clinic in a university hospital. PATIENTS: Thirty-seven stool specimens from 29 HIV-infected patients with microsporidiosis were tested. The diagnosis of microsporidian infection was made by light microscopy of stool specimens and species identification was made by transmission electron microscopy of duodenal biopsies. Sixty-one stool specimens from 45 HIV-infected patients without microsporidiosis served as controls. METHODS: PCR was performed using DNA extracted from stools with two primers sets, one specific for E. bieneusi and one specific for E. intestinalis. RESULTS: A 1265 base-pair fragment of the small subunit ribosomal RNA (rrs) gene could be amplified from all 31 stool specimens infected with E. bieneusi. In addition, a 930 base-pair fragment of the rrs gene could be amplified from all six stool specimens infected with E. intestinalis. The 61 control stools were negative with both primers. CONCLUSIONS: These results suggest that a PCR based assay using species-specific primers sets can be used successfully for microsporidian species differentiation from stool specimens, thus obviating the need for invasive biopsy procedures.

Trial of oral fumagillin for the treatment of intestinal microsporidiosis in patients with HIV infection. ANRS 054 Study Group. Agence Nationale de Recherche sur le SIDA.

OBJECTIVE: Intestinal microsporidiosis caused by Enterocytozoon bieneusi is a cause of chronic diarrhoea in patients with HIV infection for which there is no current therapy. This study was designed to assess the safety and efficacy of oral fumagillin in this infection. DESIGN: A dose-escalation trial. METHODS: Twenty-nine HIV-infected patients with E. bieneusi infection were consecutively enrolled in the trial. Oral doses of fumagillin were given to four groups of patients for 14 days: 10 mg/day (group 1), 20 mg/day (group 2), 40 mg/day (group 3), and 60 mg/day (group 4). Patients were seen at weeks 1, 2, 4 and 6 to assess safety and efficacy. Efficacy was assessed primarily by the clearance of microsporidia from stools and follow-up duodenal biopsies. RESULTS: Thirteen patients complained of abdominal cramps, vomiting or diarrhoea during the study, and three patients had fumagillin withdrawn because of adverse events. Thrombocytopenia, neutropenia and hyperlipasaemia were the most frequent biological adverse events. Twenty-one out of 29 patients transiently cleared microsporidia from their stools during the study. By week 6, however, all patients in groups 1, 2 and 3 had parasitic relapse. Interestingly, eight out of 11 (72%) patients treated with 60 mg/day (group 4) apparently cleared microsporidia from their gastrointestinal tract and gained weight. No parasitic relapse was documented in these eight patients during a mean follow-up of 11.5 months. CONCLUSION: Treatment with fumagillin at 60 mg/day for 14 days has promise as an effective oral treatment for E. bieneusi infections.

Potential efficacy of fumagillin in intestinal microsporidiosis due to Enterocytozoon bieneusi in patients with HIV infection: results of a drug screening study. The French Microsporidiosis Study Group.

OBJECTIVE: Intestinal microsporidiosis due to Enterocytozoon bieneusi is a frequent cause of chronic diarrhoea in patients with HIV infection for which there is no available therapy. This study was designed to search for a drug with activity against this organism. DESIGN: Prospective open-labelled Phase II multicentre study. SETTING: University hospitals. PATIENTS: Sixty HIV-infected men with intestinal E. bieneusi infection. INTERVENTIONS: Ten drug regimens were consecutively tested orally for 3 weeks: albendazole plus metronidazole, sulphadiazine plus pyrimethamine, atovaquone, doxycycline plus nifuroxazide, itraconazole, flubendazole, chloroquine, paromomycin, sparfloxacin and fumagillin. Nine evaluable patients per regimen were required, but each patient could be enrolled up to three times in the study. OUTCOME MEASURE: Efficacy was assessed primarily by the clearance of E. bieneusi from stools and intestinal biopsies. The safety of each regimen was also assessed. RESULTS: Only purified fumagillin was able to clear E. bieneusi from stools as well as intestinal biopsies, whereas all other regimens failed to show antiparasitic efficacy. However, only four patients received fumagillin because of drug-induced thrombocytopenia. The four patients who received fumagillin remained free of E. bieneusi infection after a mean follow-up of 10 months. CONCLUSION: Eradication of E. bieneusi from the intestinal tract of patients with HIV infection and persistent immunosuppression is an achievable goal. Our study allowed the identification of oral fumagillin as a potential treatment for intestinal microsporidiosis due to E. bieneusi.

Toxoplasma gondii pneumonia in patients with the acquired immunodeficiency syndrome.

PURPOSE: To perform a retrospective and descriptive study of Toxoplasma gondii pneumonia in patients infected with the human immunodeficiency virus (HIV). Clinical presentation, diagnostic procedures, results of therapy, and hypotheses on pathophysiology are discussed. PATIENTS AND METHODS: The study consisted of 13 HIV-infected patients who had developed T. gondii pneumonia. Eight had acquired immunodeficiency syndrome (AIDS) prior to T. gondii pneumonia and three of them had non-Hodgkin's lymphoma. Mean CD4 cell count was 32 x 10(6)/L. Serum anti-toxoplasma antibody titers were measured by an indirect hemagglutination assay and/or by an indirect immunofluorescence assay. RESULTS: All patients had fever and bilateral pulmonary infiltrates; two of them presented with septic shock. Mean arterial oxygen tension was 47 +/- 12 mm Hg. The diagnosis was established by bronchoalveolar lavage in 10 of 11 cases, open lung biopsy in one case, and postmortem biopsy in two cases. Serologic evidence of past infection was observed in 11 of 12 cases, while one patient presented with acute disseminated disease and absence of serum anti-toxoplasma antibody response. Extrapulmonary involvement was present in seven patients: liver (four), brain (three), bone marrow (two), heart (two), stomach (one). Ten patients recovered from T. gondii pneumonia. CONCLUSION: T. gondii pneumonia must be considered in AIDS patients with severe diffuse bilateral pneumonia, especially when associated with a very low CD4 cell count or non-Hodgkin's lymphoma. In most of these cases, disseminated disease was associated with reactivation of prior latent infection.

Toxoplasma antibody titers in renal transplant recipients. Pretransplant evaluation and posttransplant follow-up of 73 patients.

In 73 consecutive kidney transplant recipients, anti-Toxoplasma antibodies were determined before transplantation and during a 3-year follow-up after transplantation. In 9 patients, antibody titers increased significantly after transplantation. Antibody titers to various viral antigens determined in parallel remained unchanged, suggesting that the anti-Toxoplasma antibody increase was not due to polyclonal nonspecific stimulation. In 2 of the 24 pretransplant seronegative patients, acquired toxoplasmosis was diagnosed serologically after transplantation, with the observation of a strong IgM and IgG antibody response. The incidence of toxoplasmosis in this group of patients was not found to be significantly different from that in a normal population, suggesting that transmission of Toxoplasma from the transplanted kidney may not be a significant mode of contamination. Among the 49 patients who were seropositive before transplantation, reactivation of toxoplasmosis was suspected in 7 cases on the basis of a significant increase in IgG antibodies. Reactivation occurred more frequently in patients treated with azathioprine and antithymocyte globulin, and a direct relationship between administration of steroids and antibody increase was demonstrated in three patients. Although toxoplasmosis has occasionally been reported as a major infectious problem in kidney transplant recipients, our clinical and serological data show that the potential risk of developing Toxoplasma infection is low since none of the patients with either acquired or reactivated toxoplasmosis developed clinical disease.

Application of topological descriptors in QSAR and drug design: history and new trends.

Powerful methodologies for drug design and drug database screening and selection are presently available. Studies relating the structure of molecules to a property or a biological activity by means of statistical tools (QSPR and QSAR studies, respectively) are particularly relevant. An important point for this methodology is the use of good structural descriptors that are representative of the molecular features responsible for the relevant activity. Topological indices (TIs) are two-dimensional descriptors which take into account the internal atomic arrangement of compounds, and which encode in numerical form information about molecular size, shape, branching, presence of heteroatoms and multiple bonds. The usefulness of TIs in QSPR and QSAR studies has been extensively demonstrated, and they have also been used as a measure of structural similarity or diversity by their application to databases virtually generated by computer. In this article we will briefly review the history of TIs, their advantages and limitations with respect to other descriptors, and their possibilities in drug design and database selection. These applications rely on new computational techniques such as virtual combinatorial synthesis, virtual computational screening or inverse QSAR.

Anti-toxoplasmosis drugs.

The drugs most commonly used for treatment of toxoplasmosis combine folate inhibitors that frequently cause undesirable side effects. There is an urgent need for new drugs or drug combinations that are able to eradicate the tissue cysts responsible for relapses, particularly for patients intolerant to folate inhibitors. Although promising for its activity against cysts, atovaquone is still limited by its variable intestinal absorption. The recent demonstration that the apicoplast of Toxoplasma gondii could be a possible unique drug target for antibiotics such as macrolides and fluoroquinolones represented an important breakthrough in this area.

Prophylaxis of toxoplasmosis infection with pyrimethamine/sulfadoxine (Fansidar) in bone marrow transplant recipients.

Prophylaxis against toxoplasmosis with weekly administration of pyrimethamine/sulfadoxine (Fansidar) was assessed for efficacy and toxicity in bone marrow transplant (BMT) recipients over a 21 month period. Sixty-nine of 90 consecutive seropositive patients were evaluable. Fansidar was administered from the time of established engraftment (median day 40, range days 13-100). Medication was scheduled to be continued until 6 months or longer in cases of continued immunosuppression (median 10 months, range day 72 to 22 months). No proven case of toxoplasmosis occurred in patients receiving prophylaxis. In addition, there were no cases of Pneumocystis carinii. Side-effects included BM suppression requiring cessation (n = 4) or interruption (n = 8) of therapy and rash (n = 1). To evaluate toxicity associated with prolonged therapy, 42 evaluable patients were assessed at 6 months following transplant (or at least 4 months of continuous treatment). Haematological toxicity was minimal and compounded in three patients showing moderate derangement by cytomegalovirus infection and graft-versus-host disease. Fansidar is an effective prophylactic agent against toxoplasmosis in BMT patients.

Toxoplasma infection after human allogeneic bone marrow transplantation: clinical and serological study of 80 patients.

Systematic clinical and serological studies to evaluate the frequency of toxoplasmosis in bone marrow transplant recipients were performed in 80 consecutive patients. Antitoxoplasma antibody titres were measured in donors and recipients before transplant and subsequently post-transplant. Before bone marrow transplant, 54 recipients were seropositive and 26 were seronegative, whereas 35 donors were seropositive and 45 were seronegative. After bone marrow transplant, the frequency of clinical and serological manifestations of toxoplasmosis appeared closely related to the recipient's serological status before transplant. In the seronegative group of patients before transplant the incidence of toxoplasmosis was low: only two patients experienced seroconversion 3 months after bone marrow transplant and one developed clinical symptoms consistent with toxoplasmosis but without cerebral involvement. Clinical toxoplasmosis or secondary elevation of antibody titres was mostly observed in pre-bone marrow transplant seropositive patients; in this group, cerebral toxoplasmosis occurred in four patients and a significant secondary rise of antibody titres was observed in 16 patients. It thus appears that toxoplasmosis is most often related to a reactivation of latent cysts. Prophylactic treatment may be useful in patients presenting serological evidence of past or latent infection before bone marrow transplant.

Epidemiology and diagnosis of invasive pulmonary aspergillosis in bone marrow transplant patients: results of a 5 year retrospective study.

Of 322 patients undergoing allogeneic BMT, 18 developed invasive pulmonary aspergillosis at a mean of 115 days post-transplant, with a mortality rate of 82%. Pulmonary localization was common but cerebral involvement was seen in 10 of 18 patients. The diagnosis was made ante mortem in 11 patients by direct examination of pathological samples or culture and A. fumigatus was the only species isolated. Specific antibodies were not demonstrated before or at the time of clinical symptoms and Aspergillus antigen was only seen in one patient a few days before death.

Detection by PCR of Toxoplasma gondii in blood in the diagnosis of cerebral toxoplasmosis in patients with AIDS.

The polymerase chain reaction (PCR) for amplification of Toxoplasma gondii DNA was performed prospectively in the blood of 19 patients with AIDS and cerebral toxoplasmosis. The B1 gene and TGR1E sequence were used as targets and results were confirmed by hybridisation. Controls consisted of 24 HIV infected patients with tissue culture proven T gondii parasitaemia and 57 HIV infected patients without toxoplasmosis. PCR was positive with both targets in 20 of 24 samples (84%) from patients with parasitaemia. Three of 57 samples (5%) from patients without toxoplasmosis were PCR positive with either target, but none was positive with both targets. Only three of the 19 patients (16%) with cerebral toxoplasmosis had a positive PCR with both targets before the start of specific treatment. PCR performed in blood is of little diagnostic value in cases of cerebral toxoplasmosis but could be useful in patients with disseminated infection.

Specific anti-toxoplasmic IgG antibody immunoblot profiles in patients with AIDS-associated Toxoplasma encephalitis.

Among 186 suspected cases of Toxoplasma encephalitis (TE) in HIV-infected patients, 113 were classified as TE and 73 as non-TE. Serum Toxoplasma gondii (T.g.) antibodies were detected by ELISA in 97% of TE vs 71% of non-TE cases (p < 0.001). In the 164 patients positive for T. g. antibodies, the IgG 27 and 32 bands were more frequently present in TE than in non-TE (p = 0.003, p = 0.002, respectively). Among patients with positive T.g. serology, multivariate analysis showed that the presence of an IgG 32 (OR 3.1) or IgG 27 band (OR 2.7) on Western blot was highly indicative of TE independently of each other. Positive T.g. serology, but not anti-T.g. IgG antibody titres, was predictive. Thus, the positivity of IgG 27 and 32 bands on Western blot analysis provides useful data for improving the diagnosis of presumptive TE in HIV-infected patients with suspected TE and positive Toxoplasma serology.

Polymorphisms and intronic structures in the 18S subunit ribosomal RNA gene of the fungi Scytalidium dimidiatum and Scytalidium hyalinum. Evidence of an IC1 intron with an His-Cys endonuclease gene.

The fungi Scytalidium dimidiatum (Nattrassia mangiferae synanamorph) and Scytalidium hyalinum are mainly encountered in (sub)tropical areas as plant pathogens and agents of human dermatomycosis. Because the classification and differentiation of these two species is unclear, we studied 22 S. dimidiatum and 15 S. hyalinum isolates in order to identify potential species-specific insertions and polymorphisms in the 18S subunit ribosomal gene. The presence of an IE intron in S. dimidiatum, together with a single polymorphism (A in S. dimidiatum, G in S. hyalinum) in the coding region, allowed us to differentiate these two species in most cases. Moreover, in one S. dimidiatum isolate we found a group IC1 intron containing a putative truncated His-Cys endonuclease gene. This enzyme shows strong similarity to the intronic homing endonuclease of Physarum polycephalum. Based on these results and our previous findings, we propose an evolutionary pathway for 18S rDNA S. dimidiatum insertions, implying independent events.

Influence of the host and parasite strain in a mouse model of visceral Leishmania infantum infection.

We investigated the respective roles of the host and parasite strain in a murine model of visceral leishmaniasis. Balb/c and C57Bl/6 mice were selected for their respective 'non cure' and 'cure' haplotypes vis-a-vis Leishmania major. Mice were infected with 10(7) stationary-phase promastigotes of four strains of Leishmania infantum with different infection profiles in mice: visceralization or regulation, as established by Sulahian et al. (Sulahian et al. (1998) FEMS Immunol. Med. Microbiol. 17, 131-138). The infection was monitored by measuring parasite load in the liver and spleen on days 9, 22, 44 and 87 post-infection, using a sensitive microtitration technique. Similar profiles (visceralizing or regulating) were observed in the two mouse strains, suggesting a predominant role of the Leishmania strain in the visceralization process. The host response was assessed by analyzing the granulomatous response in the liver and by quantifying specific IgG, IgG1 and IgG2a as a marker of the Th1/Th2 immune response. A granulomatous response was observed in both strains of mice but was more pronounced with visceralizing strains of L. infantum and in C57Bl/6 mice compared to Balb/c mice. The kinetics of anti-Leishmania IgG antibody production was similar in all the groups, but the distribution of IgG1 and IgG2a isotypes was different between the two mouse strains: Balb/c mice had a predominantly Th2-like response whereas C57Bl/6 had a mixed Th1/Th2-like response. This study demonstrates the determining role of both the parasite and mouse strain in the outcome of L. infantum infection. The Th1/Th2 concept does not seem to explain susceptibility and resistance to infection in our model of visceral L. infantum infection, contrary to the L. major model.