Cancer and brassinosteroids: Mechanisms of action, SAR and future perspectives

Brassinosteroids are plant hormones whose main function is to stimulate plant growth. However, they have been studied for their biological applications in humans. Brassinosteroid compounds have displayed an important role in the study of cancer pathology and show potential for developing novel anticancer drugs. In this review we describe the relationship of brassinosteroids with cancer with focus on the last decade, the mechanisms of cytotoxic activity described to date, and a structure-activity relationship based on the available information.

New Morphiceptin Peptidomimetic Incorporating (1S,2R,3S,4S,5R)-2-Amino-3,4,5-trihydroxycyclopen-tane-1-carboxylic acid: Synthesis and Structural Study

We present the synthesis and structural study of a new peptidomimetic of morphiceptin, which can formally be considered as the result of the replacement of the central proline residue of this natural analgesic drug with a subunit of (1S,2R,3S,4S,5R)-2-amino-3,4,5-trihydroxycyclopentane-1-carboxylic acid, previously obtained from L-idose. An optimized synthesis of this trihydroxylated cispentacin derivative is also reported. Molecular docking calculations on the target receptor support a favorable role of the hydroxy substituents of the non-natural β-amino acid incorporated into the peptidomimetic.

Synthesis, in vitro evaluation and molecular docking of a new class of indolylpropyl benzamidopiperazines as dual AChE and SERT ligands for Alzheimer's disease

During the last decade, the one drug-one target strategy has resulted to be inefficient in facing diseases with complex ethiology like Alzheimer's disease and many others. In this context, the multitarget paradigm has emerged as a promising strategy. Based on this consideration, we aim to develop novel molecules as promiscuous ligands acting in two or more targets at the same time. For such purpose, a new series of indolylpropyl-piperazinyl oxoethyl-benzamido piperazines were synthesized and evaluated as multitarget-directed drugs for the serotonin transporter (SERT) and acetylcholinesterase (AChE). The ability to decrease β-amyloid levels as well as cell toxicity of all compounds were also measured. In vitro results showed that at least four compounds displayed promising activity against SERT and AChE. Compounds 18 and 19 (IC₅₀ = 3.4 and 3.6 μM respectively) exhibited AChE inhibition profile in the same order of magnitude as donepezil (DPZ, IC₅₀ = 2.17 μM), also displaying nanomolar affinity in SERT. Moreover, compounds 17 and 24 displayed high SERT affinities (IC₅₀ = 9.2 and 1.9 nM respectively) similar to the antidepressant citalopram, and significant micromolar AChE activity at the same time. All the bioactive compounds showed a low toxicity profile in the range of concentrations studied. Molecular docking allowed us to rationalize the binding mode of the synthesized compounds in both targets. In addition, we also show that compounds 11 and 25 exhibit significant β-amyloid lowering activity in a cell-based assay, 11 (50% inhibition, 10 μM) and 25 (35% inhibition, 10 μM). These results suggest that indolylpropyl benzamidopiperazines based compounds constitute promising leads for a multitargeted approach for Alzheimer's disease.

Three-Dimensional Quantitative Structure-Activity Relationships (3D-QSAR) on a Series of Piperazine-Carboxamides Fatty Acid Amide Hydrolase (FAAH) Inhibitors as a Useful Tool for the Design of New Cannabinoid Ligands

Fatty Acid Amide Hydrolase (FAAH) is one of the main enzymes responsible for endocannabinoid metabolism. Inhibition of FAAH increases endogenous levels of fatty acid ethanolamides such as anandamide (AEA) and thus consitutes an indirect strategy that can be used to modulate endocannabinoid tone. In the present work, we present a three-dimensional quantitative structure-activity relationships/comparative molecular similarity indices analysis (3D-QSAR/CoMSIA) study on a series of 90 reported irreversible inhibitors of FAAH sharing a piperazine-carboxamide scaffold. The model obtained was extensively validated (q² = 0.734; r² = 0.966; r²_m = 0.723). Finally, based on the information derived from the contour maps we designed a series of 10 new compounds with high predicted FAAH inhibition (predicted pIC₅₀ of the best-proposed compounds = 12.196; 12.416).

Structure-Activity Relationships Based on 3D-QSAR CoMFA/CoMSIA and Design of Aryloxypropanol-Amine Agonists with Selectivity for the Human β3-Adrenergic Receptor and Anti-Obesity and Anti-Diabetic Profiles

The wide tissue distribution of the adrenergic β3 receptor makes it a potential target for the treatment of multiple pathologies such as diabetes, obesity, depression, overactive bladder (OAB), and cancer. Currently, there is only one drug on the market, mirabegron, approved for the treatment of OAB. In the present study, we have carried out an extensive structure-activity relationship analysis of a series of 41 aryloxypropanolamine compounds based on three-dimensional quantitative structure-activity relationship (3D-QSAR) techniques. This is the first combined comparative molecular field analysis (CoMFA) and comparative molecular similarity index analysis (CoMSIA) study in a series of selective aryloxypropanolamines displaying anti-diabetes and anti-obesity pharmacological profiles. The best CoMFA and CoMSIA models presented values of r²_ncv = 0.993 and 0.984 and values of r²_test = 0.865 and 0.918, respectively. The results obtained were subjected to extensive external validation (q², r², r²_m, etc.) and a final series of compounds was designed and their biological activity was predicted (best pEC₅₀ = 8.561).

Combined CoMFA and CoMSIA 3D-QSAR study of benzimidazole and benzothiophene derivatives with selective affinity for the CB2 cannabinoid receptor

The preceding years have brought an exponential increase in our understanding of the endocannabinoid system (ECS), including the knowledge of CB1 and CB2 cannabinoid receptors, endocannabinoids, and the enzymes that synthesize and degrade endocannabinoids. Among these ECS components CB2 receptors have been the subject of considerable attention, primarily due to their promising therapeutic potential to treat numerous pathologies while avoiding the adverse psychotropic effects that can accompany CB1 receptor-based therapies. Recently, our research group has reported a new series of non-cytotoxic benzo[d]imidazoles and benzo[b]thiophenes displaying high CB2/CB1 selectivity index. In order to investigate the structural requirements for CB2 ligands and to derive a predictive model that can be used for the design of novel selective CB2 ligands, a three-dimensional quantitative structure-activity relationship (3D-QSAR) study was performed on the above mentioned chemical series employing comparative molecular field analysis (CoMFA) and comparative molecular similarity index analysis (CoMSIA) techniques. The CoMFA and CoMSIA models displayed high external predictability (r_pred² 0.919 and 0.908) and good statistical robustness. Valuable information regarding the steric, electrostatic and hydrophobic properties of the molecules was obtained, and several modifications around both heterocycles were evaluated with the aim to generate new promising series of benzo[d]imidazoles and benzo[b]thiophenes derivatives displaying high CB2 selectivity and low toxicity.

Evaluation of a Triatoma infestans elimination program by the decrease of Trypanosoma cruzi infection frequency in children younger than 10 years, Chile, 1991-1998

Chagas disease is widespread in Chile, distributed in rural and periurban areas in the 7 most northern regions of the country. The principal vector of Trypanosoma cruzi is Triatoma infestans. The interruption of the domestic cycle of transmission of T. cruzi has been attempted by health education, human housing improving, and elimination of the vector by means of systematic insecticide spraying of human dwellings. Spraying with insecticides has been supported by Chile's health authorities and has been carried out for the last 12 years. A total of 13,280 children (aged up to 10 years) were randomly selected from 47 counties in the area of Chile endemic for Chagas disease, and blood samples were collected to determine the levels of antibodies to T. cruzi by indirect hemagglutination and enzyme-linked immunosorbent assay tests. The results of the tests were analyzed to determine the changes that occurred after 12 years of insecticide spraying of dwellings to eliminate T. infestans infestation. A total of 142 (1.1%) samples of children showed antibodies to T. cruzi. This rate is significantly lower than the data generated in similar studies conducted in 1982-1985. The following reduction in prevalence rates were observed in each of the 7 endemic regions of the country: region I, 5.5-0.3%; region II, 6.6-0.3%; region III, 9.8-1.0%; region IV, 7.2-2.0%; region V, 5.2-1.9%, Metropolitan region, 1.4-0.6%; and region VI, 1.4-0.4%. Serovigilance of T. cruzi antibodies level represents a novel approach that may allow the evaluation of the impact of the vector elimination program. The results identify regions that need to strengthen the efforts to reduce the insect infestation of dwellings.

[Serological certification of the interruption of the vectorial transmission of Chagas disease in Chile]

BACKGROUND

In 1999 an International Commission of Experts evaluated the sanitary interventions that started in 1980 to eliminate Triatoma infestans, the biological vector of Chagas disease, to certify if the conditions needed to interrupt the transmission, were achieved.

AIM

To report the data used by the International certification commission to certify the interruption of vectorial transmission of Chagas disease in Chile.

MATERIAL AND METHODS

A comparative evaluation of the prevalence of Trypanosoma cruzi antibodies in children surveyed between 1994 and 1995 and between 1995 and 1999.

RESULTS

In the first period, 5,948 children were surveyed and in the second, 5,069 children were studied. Twenty children (0.4%) were positive for Trypanosoma cruzi antibodies in the second survey. These figures were significantly lower than the 1.1% prevalence detected between 1994 and 1995. In only three of the 20 cases, the transmission through vectors was confirmed, which represents a 99.4% reduction of this way of transmission.

CONCLUSIONS

Based on these findings, the Commission certified that Chile is the second country in Latin America to interrupt the vector transmission of Chagas disease. The successful public health program for Chagas disease will have a positive impact improving the quality of life of rural populations, that are most exposed to the disease.

Highly diastereofacial anti-aldol reaction: practical synthesis of optically active anti-2-alkyl-3-hydroxycarboxylic acid ester units

A variety of esters derived from commercially available norephedrine were used in diastereoselective anti-aldol reactions. The aldol reaction of designed 2-(N-2-methylbenzyl-N-2,4,6-trimethylbenzyl)amino-1-phenylpropanol esters 4a-d with aldehydes furnished anti-2-alkyl-3-hydroxycarboxylic acid esters in excellent diastereomeric ratios (>98:2) when LDA-Cp2ZrCl2 (0.3 equiv) was used for enolization, followed by transmetalation into the zirconium enolate for aldolization. The novel auxiliary 3 for the anti-aldol reaction does not exhibit the ordinary basicity of tertiary amines; 3 can be extracted from acidic media with organic solvents. Its use is, therefore, very advantageous not only for extraction of the aldol products from the acidic water solutions, but also for recovering the chiral auxiliary 3 after the reductive cleavage. Treatment of aldol or 3-protected aldol products with DIBAL-H or LiAlH4 affords the versatile synthons, 2-alkyl-propane-1,3-diols or those 3-protected diols in >98% ee's together with 3 in nearly quantitative recovery.

[Frequency of anti-Toxoplasma gondii antibodies in cats from Valdivia city, Chile]

Toxoplasmosis is a parasitic zoonosis. The importance of the cat as related to this parasitosis lies in the fact that it is not only the definite host of the parasite, but responsible for its dissemination through the release of oocysts, which subsequently infect both humans and other animals. The objective of this study was to determine the serological prevalence of Toxoplasma gondii in the feline population of the city of Valdivia (Chile) and to establish the possible epidemiological implications of this prevalence. With these goals in mind the technique of indirect immunofluorescence was implemented to detect anti- T. gondii species--specific IgG. Blood samples from 97 cats (selected using a directed sampling process) from different sectors of Valdivia were collected. The sample included 46 males and 51 females of different ages, Positive and negative control sera obtained from de United States were used to verify the results, observed by UV microscopy. The anti-feline IgG antibody was used as directed by the manufacturer (Sigma). Of the 97 selected cats, 32 were found to be positive with a titre higher than 1:4, a prevalence of 33.0%. The number of infected males as compared to the number of infected females was found to be statistically insignificant, using the chi-square analysis with p less than 0.1. In contrast, a definite correlation between age and seropositivity was found; infection levels were higher in older animals. These results are consistent with those obtained in different studies on this topic that have been performed in different parts of the world. However, they would seem to be in conflict with other, similar studies that have been done recently in Chile; this may be due to the fact that the cats selected for this study were exposed to different climatic conditions than those examined in previous works. In conclusion, it has been determined that in Valdivia exist cats infected by T. gondii, which indicate the presence of the necessary epidemiological conditions for the persistence of this parasitic cycle and the source of infection for humans and other animals.

Development of an immunoenzymatic assay for the detection of human antibodies against Trypanosoma cruzi calreticulin, an immunodominant antigen

We have developed an indirect immunoenzymatic assay (ELISA) for the detection of human antibodies against calreticulin (formerly known as Tc45), a dimorphic Trypanosoma cruzi antigen, described in our laboratory. PVC microtitration plates were sensitized with the monoclonal anti-calreticulin antibody (MoAb) and reacted with calreticulin present in a partially purified preparation. The presence of anti-T. cruzi calreticulin IgG in sera from infected individuals was tested. The data generated with this assay were validated by correlation, in a regression analysis, with those obtained by an indirect immunoradiometric assay (IRMA). From the 12 seropositive sera (as defined by a commercial test), eight came out positive and four negative in both assays. The 12 human sera were also analyzed in direct immunometric assays (ELISA and IRMA), where the solid phase was sensitized with a whole parasite extract. The direct ELISA and IRMA correlated positively (P<0.01). Further validation of this ELISA was achieved with an indirect immunofluorescense assay. The high degree of significance obtained when the indirect IRMA and ELISA systems were compared, indicated that the relatively small sample number used (12) was statistically satisfactory for the purposes of this investigation. Thus, the IRMA can be replaced by the ELISA, with advantages mainly derived from the cumbersome manipulation of radioactive wastes. The MoAb used as an antigen capture agent in the ELISA proposed here, recognizes a homologous protein in Trypanosoma rangeli, suggesting that individuals infected with this parasite might have crossreactive antibodies. However, the system retains its diagnostic interest, given the facts that the MoAb does not recognize a homologous protein in Leishmania mexicana, Leishmania donovani, or Crithidia fasciculata.

[Comparison of Trypanosoma cruzi infection in less than 10 years old children from the V Región, Chile, 1982-1995]

Evaluation of desinsectation programs carried out in the two Health Services from the V Region, was undertaken by comparing serologic prevalences of T. cruzi infection age groups exposed to the risk of infection in rural areas during the antivectorial campaign activities (1982 vs 1995). Thus, were studied 2,193 blood samples from children under 10 years of age, proceeding from six chagasic endemic provinces in which antitriatomic domiciliary insecticide sprayings had been performed. Indirect hemagglutination and ELISA tests were carried out to each of the blood samples. A total de 42 (1.9%) children resulted positive. As in five counties no positive cases were detected in the last five years it is possible to assume that vector transmission of T. cruzi should have been interrupted in them. When comparing prevalences existing in 1982 with the present ones, it is possible to observe a 63.5% of reduction of transmission in the V Region, been this reduction higher in the Aconcagua Health Service with 79.6% and lower in the Viña del Mar--Quillota Health Service with 55.6%. According to these results, comparison of prevalence of T. cruzi infection in children less than 10-year-old in diverse periods, allows evaluate the vectorial control of Triatoma infestans programs.

Seroprevalence of Toxoplasma gondii infection in sheep and alpacas (Llama pacos) in Chile

Serum samples from 408 sheep from different regions of Chile and 447 alpacas (Llama pacos) from the north of the country were tested for Toxoplasma gondii antibodies. The indirect haemagglutination test (IHAT) was used in both species and the indirect immunofluorescence test (IIFT) was also used on the sheep samples in order to compare the performance of the tests in that species. In both tests, titers > or = 1:16 were considered diagnostically significant. Sera from 49 sheep (12%) were positive to T. gondii antibodies by the IHAT. When using the IIFT, 114 sheep sera (28%) were positive. The different results obtained in sheep sera between the tests were significant (p < 0.0001). No differences were observed between geographical locations or sex of the sampled sheep regarding serological detection of T. gondii antibodies in sheep. As expected, adult sheep showed higher T. gondii reactivity than young sheep (p = 0.0008). The corrected prevalence of toxoplasmosis in alpaca was 16.3% (32 positive out of 447). The rather low prevalence in alpacas may be associated with their extensive management as well as the extreme climatic conditions of The Andes which apparently would not be favorable for the transmission of the parasite.

[Epidemiological status of Chagas disease in the endemic area from Region II of Antofagasta]

During 1997 a seroepidemiological study on Chagas' disease was carried out in 18 localities of three provinces (Tocopilla, El Loa and Antofagasta) of Region II (20 degrees 56'-26 degrees South Lat.; 70 degrees 38'-67 degrees West Long.), in order to assess the impact of the control program against Triatoma infestans launched in 1988, based on insecticide spraying of dwellings. By means of ELISA and an indirect hemagglutination test for Chagas' disease blood samples from 1,034 children under 10 years of age were examined, arising a 0.5% (3 cases) positivity. Test resulted positive in 2 (0.9%) children from the locality of San Pedro de Atacama and 1 (0.4%) from Calama city, all in the age group 6-10 year-old. However, none of their dwellings were found infested with T. infestants. These results indicate that the control program has a good possibility to prevent new human infections. It is advisable to continue the seroepidemiological and entomological vigilance and remark the necessity of increasing the effort in the study of transmission through other routes, to adopt or reinforce the pertinent preventive measures.

Identification of immunodominant antigens by immunoelectrotransfer in hydatid fluid

Identification and characterization of immunodominant antigens in hydatid fluid was performed by electrophoresis in polyacrylamide gels (SDS PAGE) followed by immunoelectrotransfer (Western Blot). The studies were performed in sera of 23 patients with surgically confirmed hydatid disease, 12 patients with clinical suspicion of the infection and positive serology according to conventional serology (double diffusion with detection of are 5 and ELISA test), 28 healthy subject and 23 patients with parasitic infections different from hydatidosis. The results showed 7 antigenic bands located between 8 and 120 kDa, two immunodominant bands (MW 8 and 12 kDa) were recognized by the sera of patients suffering from hydatid disease and those with positive serology. Two additional bands were detected by the sera of healthy subjects and by the samples of patients presenting cysticercosis. It is concluded that the antigens with molecular weights of 8 and 12 kDa. would be those of major diagnostic value, while those of 32 and 60 kDa are nonspecific.

[Yield of xenodiagnosis and PCR in the evaluation of specific chemotherapy of Chagas' disease in children]

Amplification by the polymerase chain reaction (PCR) of Trypanosoma cruzi kinetoplastic DNA was used to enhance sensitivity in the detection of the parasite in blood, with the ultimate goal of improving the parasitological diagnosis of Chagas' disease in 0-10 year-old infected children. Twenty eight children were evaluated by using xenodiagnosis (XD) and PCR. Whereas XD detected 75.0% of the cases PCR was positive in 96.8%. The usefulness of the PCR was further investigated in the 28 children who have received specific treatment with nifurtimox. Negativation of XD after three and six months post treatment was observed in all the cases, but only 21.4% and 35.8% negativation of the PCR after three and six months post treatment respectively. These observations suggest that PCR is the most sensitive and quick technique available for direct detection of T. cruzi in chagasic children and that it can be a very useful tool for the follow-up of infected subjects after specific chemotherapeutical treatment.

[Clinical and epidemiological study of blood donors seropositive for Trypanosoma cruzi]

BACKGROUND

The prevalence of positive antibodies for Chagas disease in a blood bank of a public hospital in Santiago is 1.2%. These positive individuals should be informed about their condition and further studied.

AIM

To perform a serological confirmation, an epidemiological and clinical assessment of blood donors seropositive for Chagas disease in a blood bank of Santiago.

SUBJECTS AND METHODS

One hundred eleven seropositive donors, detected between 1994 and 1996, were studied. Serological reactions were confirmed with ELISA and indirect immunofluorescence reactions. Those confirmed as positive were subjected to a clinical-epidemiological questionnaire, physical examination, EKG and barium enema or swallow according to symptoms.

RESULTS

Seventy individuals were confirmed as positive for Chagas disease. Most of them lived at least once in an endemic zone for Chagas disease or in a sun-dried clay brick house. Forty-percent of individuals knew reduviid bugs and 14% had been bitten by these insects. Twenty six percent of these subjects had an abnormal EKG (61% with bradycardia). No digestive diseases attributable to Chagas disease were detected.

CONCLUSIONS

The high prevalence of problems attributable to Chagas disease among seropositive blood donors underscores the need of an epidemiological follow up of these individuals.

A putative pyruvate dehydrogenase alpha subunit gene from Trypanosoma cruzi

A full-length DNA clone encoding a putative pyruvate dehydrogenase alpha subunit (E1 alpha) gene was isolated from a Trypanosoma cruzi (RA strain) DNA library. Sequencing of this clone revealed it to encode a 378 amino acid protein (M(r) 42774) with high sequence similarity to E1 alpha obtained from different sources. The highest score is obtained with human E1 alpha: 43,3% similarity. Southern blot analysis is consistent with the existence of a single copy of this putative T. cruzi E1 alpha gene per haploid genome in different parasite strains. Expression of this gene was demonstrated by Northern blot analysis and its trans-splicing acceptor site was identified by Polymerase Chain Reaction-mediated amplification of its cDNA.

[Evaluation of vectors of Chagas' disease eradication programs in Chile by serological study of children under 10 years old]

Chagas' disease is a parasitic zoonosis with high prevalence in Chile. It is distributed in rural and periurban section in the northern most seven out of thirteen regions in which the country is divided, and affects about 142,000 individuals dispersed in most of the 165 counties sited in the chagasic zone. Triatoma infestans--intradomiciliary species--is the main and practically exclusive vector of Trypanosoma cruzi. Diverse tools may be utilized in order to interrupt the domestic cycle of transmission of T. cruzi: health education, housing improvement and elimination of vectors by dwelling insecticide sprayings. This last resource has received priority in Chile in the last 12 years. To evaluate the effectivity of the programs for eliminating T. infestans a serological study for Chagas' disease--comprising 8,767 children less than 10 years old from 27 rural counties insecticide sprayed in the last 12 years--was carried out. A global total of 125 (1.4%) children resulted positive, figure significantly lower than 5.4% found in 1982-1990 in the same age group. Distribution by regions of positive individuals showed a decrease of prevalence in each of them: III Region, from 9.8 to 1.0%, IV Region, 7.2 to 2.0%, V Region, 5.2 to 1.9%, and Metropolitan Region, 1.4% to 0.6. Even though positive children have still been found in 46.7% of localities of the studied counties, it is possible to affirm that the vector control programs have been effective and must be maintained, and increased in those localities with T. cruzi infection in children under 10 years of age, with the general aim of eradicate Chagas' disease transmission in Chile before 2000.

[Evaluation of a triatoma infestans eradication program in rural dwellings from the IV region, Chile, by means of serology for Chagas disease in 0-10 years old children]

The present study deals with the evaluation of the effectiveness of the measures employed in the control of Triatoma infestans, the vector of Trypanosoma cruzi infection (Chagas' disease), in the IV region of Chile through a serological follow up program. For this reason, a serological survey has been carried out in 2,783 children, from 0 to 10 years, who live in rural high endemic areas of the region. The sera were tested using an indirect hemagglutination test (IHAT) and ELISA techniques with results agreeing in 99.9% of the samples. In children with positive serology xenodiagnosis was performed and blood samples from the corresponding mothers were submitted to serology for Chagas' disease. These additional tests should allow to distinguish between congenital infection and vectorial transmission. It was observed that vectorial transmission of T. cruzi was interrupted in some localities where entomological control has been applied for 10 years, or lowered in those which have been submitted to desinsectations in the last 5 years. On the other hand, a relatively high prevalence of the infection has been detected in some localities. These results suggest an apparent increase of vectorial transmission, indicating the need of readjusting the dwellings insecticide sprayings activities to improve the measures against the vector.

Diagnostic value of detecting specific IgA and IgM with recombinant Trypanosoma cruzi antigens in congenital Chagas' disease

The present study compares the early diagnosis of congenital Chagas' disease with a DOT assay using recombinant antigens with immunofluorescence antibody testing (IFAT) and an enzyme-linked immunosorbent assay (ELISA). The studies were performed using cord blood and sera of 12 infected newborns (group I) and 12 uninfected ones born to Trypanosoma cruzi-infected mothers (group II). Conventional IFAT and ELISA showed positive results for IgG at high titers, in infants and mothers of both groups; IgA antibodies were detected by ELISA in four of the infected infants and IgM was detected in two of them. All sera of the uninfected infants were negative for IgA and IgM in the ELISA. Application of a DOT assay using eight recombinant T. cruzi antigens allowed detection of specific IgA in the cord blood of six of the infected cases and IgM in eight of them. Repetition of these serologic tests in samples obtained during a monthly follow-up gave positive results for IgA in two of the initially negative infants of group I and for IgM in four of them. This means that diagnosis of congenital T. cruzi infection was confirmed, through demonstration of specific IgM, in all infected infants, and of IgA in eight of them. The importance of late detection of IgM in siblings born of infected mothers is discussed. The detection of IgM and IgA in sera obtained after birth is believed to be due to a congenital transmission of the parasite that occurred late in pregnancy. No IgA or IgM antibodies could be detected by the DOT assay in the sera of the negative controls.(ABSTRACT TRUNCATED AT 250 WORDS)

[Highly homogeneous Trypanosoma cruzi populations in a low endemic region for Chagas disease: importance in the pathogenesis of Chagas disease in Chile]

Trypanosoma cruzi from 23 chronic and acute cases of Chagas disease were isolated and further characterized. They displayed a remarkable similarity, after typification by schizodeme analysis using restriction endonuclease Eco Ri. All T cruzi isolates belonged to the isoenzymatic Zymodeme 2 Bol. These findings were corroborated analyzing cases from families with demonstrated congenital transmission. The acute cases were newborns or offspring of infected mothers or patients with AIDS. All T cruzi strains isolated in these cases were very similar with almost identical schizodemes. Patients with AIDS had severe clinical manifestations whereas children with congenital infections had a great variety of clinical symptoms. In chronic cases, little clinical differences were observed for the different T cruzi strains. It is concluded that there is a low correlation between the T cruzi strain and the clinical prognosis of Chagas disease, being of greater relevance the host's genetic background and immune response.

[Evaluation of commercial kits used for Chagas disease diagnosis in blood banks in Chile. II. Routine application]

Aiming to study the applicability and reproducibility of four commercial kits used for the serological detection of Chagas disease (Chagatest-Inst Invest Paraguay, Ortho Chagas, Abbott Chagas (ELISA tests) and Estabilgen Hemo Chagas (indirect hemagglutination test)), a comparative serological study was performed in 256 sera samples coming from a highly endemic area, 249 samples from a low endemic area, 180 reference sera and 2264 samples coming from three blood banks. Specificity of the kits was excellent and sensitivity ranged from 60 to 100%. The indirect hemagglutination test has the lower sensitivity. Some disagreements in the results were observed in the three blood banks, probably due to an unsatisfactory reactive management. We conclude that ELISA tests should be recommended for routine detection of Chagas disease and that for this purpose, a net of laboratories under the direction of a national reference center should exist. This center should assess new commercial products, train technicians and supervise the laboratories.

[The diagnosis of chronic Chagas disease using recombinant antigens of Trypanosoma cruzi]

A panel of eight recombinant Trypanosoma cruzi antigens was used to study the IgG reactivity of sera proceeding from 151 patients with chronic Chagas disease. These samples were reactive against T Cruzi epimastigotes by immunofluorescence and enzyme linked assays. A dot blot assay was performed to evaluate the reactivity against recombinant clones 1, 2, 13, 26, 30, 36, 54 and SAPA (Shed Acute Phase Antigen). Ninety six percent of samples reacted against one or more of these antigens. The most frequently recognized proteins were clones 1, 2, 13, 36 and 26 with 90, 89, 76, 71 and 66 percent of reactivity respectively. Less than 50% of sera reacted against clones 30, 54 and SAPA. Sera from symptomatic patients had a significantly higher frequency of reactivity against clone SAPA than those from asymptomatic patients. This difference suggests that a high reactivity against clone SAPA may be related to acute infections and symptoms. No significant relationship could be established between specific recombinant clone recognitions and particular clinical forms of the disease (cardiological or digestive). It is concluded that these recombinant proteins may become a good tool for the evaluation of the immune response of patients infected with T. cruzi.

[Etiologic diagnosis of pneumonia in HIV-AIDS patients. Usefulness of fibrobronchoscopy]

AIM

to assess the usefulness of fiberoptic bronchoscopy in the etiologic diagnosis of pulmonary infiltrates in patients with AIDS.

PATIENTS AND METHODS

in 25 patients with AIDS and pneumonia, 31 fiberoptic bronchoscopies with bronchoalveolar lavage were performed; in 11 occasions, a transbronchial biopsy was also performed.

RESULTS

in 24 of the 31 procedures (77%) an etiologic diagnosis was made. There were 7 false negative results; in two of these patients, a repeated examination allowed an etiologic diagnosis. The etiologies of the infiltrates were pyogenic bacteria in 14 cases. Pneumocystis carinii in 9, mycobacteria in 3, cytomegalovirus in one and a lymphocytic interstitial pneumonia in one. In 5 patients, the association of two or more etiological agents was observed. Except one case, all patients had a good response to specific treatments. There were no complications attributed to the bronchoscopic procedure.

CONCLUSIONS

fiberoptic bronchoscopy and bronchoalveolar lavage are safe and effective procedures for the etiologic diagnosis of pulmonary infiltrates in patients with AIDS.

[Pneumocystis carinii infection. Various aspects on its clinical and laboratory diagnosis]

P carinii is an opportunistic pathogenic agent able to produce severe infection that must be diagnosed promptly. We analyzed 138 samples from 100 patients suspected of having infection by P carinii. The ortho-toluidine blue and the methenamine stains were used to analyze the samples. Infection was demonstrated in 18 patients, 13 adults and 5 children. Underlying disease was AIDS in 7 and other immunosuppressive disorders in the rest. No immunocompetent patient was infected with P carinii. Proper sample collection is important for diagnosis. When bronchoalveolar lavage is not possible, pharyngo-tracheal aspirate in children and sputum sampling after assisted coughing in adults are recommended. At least 2 staining methods and proper controls are advisable.

[Evaluation of commercially available reagents for diagnosis of chagas disease in Chilean blood banks. I. Selection of reagents]

Infection with T cruzi through blood transfusion is an important public health problem in Latin America, including Chile. A study on the sensitivity, specificity and applicability of currently applied methods was performed. Ten commercially available products were tested in a panel of 180 blood specimens against the indirect immunofluorescence antibody test (IFAT) and the immunoperoxidase test (IP). Qualitative concordance ranged from 82 to 98%, sensitivity from 64 to 97% and specificity from 93 to 100%. Some commercial products had a low performance and ELISA is recommended for routine use in Chilean blood banks, given its significantly higher sensitivity and specificity when compared to the hemagglutination test. In addition, experience with the use of the ELISA test is widespread in Chile.

Immunodetection of antibodies in sera from symptomatic and asymptomatic Chilean Chagas' disease patients with Trypanosoma cruzi recombinant antigens

A panel of eight Trypanosoma cruzi antigens produced by recombinant DNA techniques was used to compare the reactivity of IgG specificities in the sera from 45 chronic Chagas' disease patients with different clinical symptoms (cardiac disease, gastrointestinal lesions, and combined syndrome) with those present in the sera from 55 asymptomatic patients in Chile. All of the serum samples were first characterized for antibody to T. cruzi epimastigotes by immunofluorescence assay. All of the Chagas' disease sera were reactive, but none of five healthy controls whose sera were also tested had antibodies against the fixed parasites. A dot-blot assay was then performed to evaluate the serum reactivity against recombinant DNA clones 1, 2, 13, 26, 30, 36, 54, and SAPA (shed acute phase antigen). These recombinant antigens were recognized by a large proportion of the sera collected from the Chilean patients. Ninety-five percent of the serum samples reacted with one or more of the recombinant clones. Analysis of the reactivity with individual fusion proteins showed that 88% of these sera reacted with clones 1 and 2, and 78% reacted with clone 13. Differences in reactivity to clones number 13, 30, and SAPA were observed when symptomatic and asymptomatic patients were compared. These differences in reactivity were statistically significant (P less than 0.01) according to Fisher's exact test.

Evaluation of an enzyme-linked immunosorbent assay for the diagnosis of Chagas' disease using synthetic peptides

An enzyme-linked immunosorbent assay (ELISA) has been developed to detect antibodies in human sera to synthetic peptides derived from the repeating amino acid sequence in recombinant Trypanosoma cruzi antigens. Sixty serum samples from patients with chronic Chagas' disease were used to determine the reactivity against the synthetic repeat peptides derived from clones 1, 2, 30, 36, and shed acute phase antigen (SAPA). Ninety-eight percent of the samples had detectable antibodies to one or more of the synthetic peptides at titers greater than 1:100. The percentage of reactive sera increased from 28% with peptide SAPA to 93% with peptide 2. The exposure of patients to T. cruzi was reflected in indirect immunofluorescent antibody titers to fixed epimastigotes. Comparisons between ELISA and immunoradiometric assay data indicated that both tests were of approximately equal sensitivity.

[Serological diagnosis of congenital infection with Trypanosoma cruzi]

Enzyme linked immuno sorbent assay (ELISA) for IgG and IgM antibodies against T. cruzi were applied to 382 sera form adults and newborn infants, referred to our laboratory for serological diagnosis, to improve diagnosis of congenital Chagas disease. A comparative study between immunofluorescent antibody test (IFAT) and ELISA results was undertaken for IgG T. cruzi antibodies in 346 samples of adults sera, 225 of which were IFAT negative (non reactive or reactive at dilutions under 1/10) and 121 IFAT IgG positive (reactive at dilutions > or = 1/20). Positive results were obtained with both methods in 117 patients, only with ELISA in 11 IFAT negative samples and only with IFAT at low titers in four ELISA IgG negative (non reactive or reactive in dilutions < or = 1/40) samples. Thus ELISA IgG did not detect more infections than IFAT IgG, although ELISA showed higher titers (> or = 2 dilutions) in 42/117 simultaneously positive specimens. In 88 sera from patients with acute, chronic and initial infection, ELISA-IgM rendered more positive results than IFAT-IgM, including approximately 17% of low titers false positives in control's sera. For this reason, when such results are obtained in patient's sera, it is advisable to consider them suspicious and to repeat the test in order to get a definitive result. ELISA allowed to detect IgM in sera from four of 36 infants born to infected mothers, which had given negative results with IFAT IgM. These results confirm that ELISA is more sensitive than IFAT for IgM antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Assay for detection of Trypanosoma cruzi antibodies in human sera based on reaction with synthetic peptides

Synthetic peptides modelled according to the amino acid sequences derived from the repeated domains of five Trypanosoma cruzi antigens were used in an immunoradiometric assay to detect antibodies appearing after natural human infections. An enzyme-linked immunosorbent assay and an indirect immunofluorescence assay performed with a complex antigenic mixture from parasites were used as controls. The results indicate that the synthetic peptides were recognized by a large proportion of serum samples collected from 34 patients with Chagas' disease in Chile and point to their possible use in diagnosis.

[Application of a system of serological surveillance of Chagas disease in a region of high chagasic endemia. I. Prevalence of Trypanosoma cruzi infection in Salamanca]

A serologic study for prevalence of Chagas infection was performed in Salamanca, Northern Chile. Indirect immunofluorescence and indirect hemagglutination reactions were used in samples from 1529 females and 698 males representing 10% of the population. A total of 499 positive results were obtained. The incidence of infection increases at a mean rate of 1% per year up to age 30, declining slowly in older groups to reach a maximum of 39.7% for the population. These data will be used to implement appropriate serologic surveillance programs and sanitary control measures in this and other populations.

Trypanosoma cruzi: a possible control of transfusion-induced Chagas' disease by phenolic antioxidants

The following phenolic antioxidant food additives were evaluated against Trypanosoma cruzi epimastigotes: BHT, BHA, gallic acid and its methyl, propyl, octyl, and lauryl esters, 2,4-di-tert-butyl-6-(4-methoxybenzyl)-phenol, 4,4'-isopropilidenediphenol, and protocatechuic acid and its ethyl ester. The inhibition of the respiration; the changes in motility, shape, and lysis of the parasites; and the human blood hemolysis caused by these chemicals were studied. Human blood samples experimentally contaminated with 2000 or 150,000 trypomastigotes per milliliter were freed of parasites after treatment for 24 hr at 4 degrees C with 5 or 10 mM BHT (2,6-di-tert-butyl-4-hydroxytoluene), respectively. Consequently, BHT and other phenolic compounds deserve further study to determine their role in preventing the transmission of Chagas' disease by blood transfusion.

Fetal IgG specificities against Trypanosoma cruzi antigens in infected newborns

A panel of Trypanosoma cruzi antigens produced by recombinant DNA techniques was used to analyze the IgM and IgG specificities present in sera from 22 mothers with chronic Chagas disease and their newborn infants. Ten of the newborns were congenitally infected and the other 12 children were healthy. While in most cases IgG specificities in the newborns mirrored those of their mothers, congenitally infected newborns had, in addition, IgG specificities that were undetectable in their mothers. The new IgG specificities observed most frequently were against a shed acute-phase antigen (SAPA), and less frequently, against other nine different parasite antigens. Thus, SAPA is able to identify new fetal IgGs because antibodies against this antigen are generated during the acute phase of the infection and not in their chronically infected mothers. Sera from congenital cases also had IgMs against several parasite antigens, but again, SAPA was the most frequently detected. Neither IgMs nor new IgG specificities were detected in healthy children born to mothers with Chagas disease. We conclude that individual antigens can be used to detect new IgG specificities present in the cord blood from infected newborns. Furthermore, detection of IgMs and new fetal IgGs with recombinant antigens may be used to sort out congenitally infected infants from uninfected ones, a method that might be applied to other infectious diseases.

[Chagas' disease in patients in chronic hemodialysis. Prevalence and risk of transmission by blood transfusion]

A serologic study of Chagas disease was performed in 110 patients submitted to chronic hemodialisis and blood transfusions. Immunofluorescence antibody testing (IgG and IgM) was positive in 6 out of 62 patients receiving multiple blood transfusions (9.7%), but negative in all 48 subjects without transfusions. Thus, repeated blood transfusion is a significant risk for T cruzi infection in chronic hemodialized patients.

A comparative study of some combined treatment regimens in acute toxoplasmosis in mice

The effectiveness of five treatment regimens was compared to mice during acute and late infection with Toxoplasma gondii. Parasitic cure rates, as judged by failure of brain tissue from surviving mice to produce infection when inoculated into clean mice, were as follows: pyrimethamine + sulfamethoxypyridazine, 92%; clindamycin + sulfamethoxypyridazine, 75%; spiramycin + sulfamethoxypyridazine, 16.7%; trimethoprim + sulfamethoxypryridazine alone, 0%. Pyrimethamine + sulfamethoxypyridazine was the most effective combination against acute toxoplasmosis in mice.

Effect of three coccidiostatics against toxoplasmosis in mice

Duocoxin, nicrazine and amprol plus showed no therapeutic effect in 50 mice each of which was infected with 25,000 organisms of a virulent Toxoplasma strain.