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Resumen El virus papiloma humano (VPH) es un virus de ADN circular doble hebra con alrededor de 200 genotipos. Este virus se relaciona a distintas lesiones tumorales que afectan cabeza y cuello, incluyendo lesiones malignas escamosas causadas por genotipos de alto riesgo como VPH-16 y VPH-18. Esta revisión tiene por objetivo determinar el rol del VPH en distintas patologías, haciendo distinción entre lesiones benignas y malignas, y con particular énfasis en aquellas en que se ha demostrado una asociación causal con el virus, tales como papilomatosis laríngea y carcinoma escamoso orofaríngeo. Además, se analizarán los mecanismos moleculares de daño, métodos de detección y de prevención como la vacunación contra el virus. Es necesario conocer la relevancia del VPH en nuestra especialidad, ya que su determinación puede tener implicancias en cuanto al manejo y pronóstico de los pacientes.

Abstract Human papillomavirus (HPV) is a double stranded circular DNA virus with around 200 genotypes. This virus is related to different tumor lesions that affect the head and neck, including malignant squamous lesions caused by high-risk genotypes such as HPV-16 and HPV-18. The objective of this review is to determine the role of HPV in different pathologies, distinguishing between benign and malignant lesions, and with particular emphasis on those in which a causal association with the virus has been demonstrated, such as laryngeal papillomatosis and oropharyngeal squamous carcinoma. In addition, molecular damage mechanisms, detection and prevention methods such as vaccination against the virus will be analyzed. It is necessary to know the relevance of HPV in our specialty, since its determination may have implications in terms of patient management and prognosis.

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SARS-CoV-2 is the causative agent of COVID-19. The dimeric form of the viral Mpro is responsible for the cleavage of the viral polyprotein in 11 sites, including its own N and C-terminus. The lack of structural information for intermediary forms of Mpro is a setback for the understanding its self-maturation process. Herein, we used X-ray crystallography combined with biochemical data to characterize multiple forms of SARS-CoV-2 Mpro. For the immature form, we show that extra N-terminal residues caused conformational changes in the positioning of domain-three over the active site, hampering the dimerization and diminishing its activity. We propose that this form preludes the cis and trans-cleavage of N-terminal residues. Using fragment screening, we probe new cavities in this form which can be used to guide therapeutic development. Furthermore, we characterized a serine site-directed mutant of the Mpro bound to its endogenous N and C-terminal residues during dimeric association stage of the maturation process. We suggest this form is a transitional state during the C-terminal trans-cleavage. This data sheds light in the structural modifications of the SARS-CoV-2 main protease during its self-maturation process.

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Resumen Uno de los pilares fundamentales en el manejo de la pandemia por SARS-CoV2 es la detección temprana de la presencia del virus en pacientes. El método más utilizado es mediante hisopado nasofaríngeo para amplificar ácidos nucleicos mediante reacción en cadena de polimerasa (PCR). Las complicaciones asociadas a la técnica de hisopado aún no están completamente caracterizadas. Hasta ahora hay un caso reportado internacionalmente de fístula de líquido cefalorraquídeo poshisopado nasofaríngeo. Presentamos dos casos de fístula posterior a dicho examen: el primer caso un paciente de género femenino con sospecha de hipertensión intracraneal idiopática, cuya brecha se reparó quirúrgicamente; el segundo caso un paciente de género masculino con antecedente de hidrocefalia y meningitis neonatal que, al estudio por rinorraquia, se encuentra un meningoencefalocele en el receso frontal derecho, también reparado quirúrgicamente.

Abstract One of the cornerstones in the management of coronavirus pandemic is the early identification of virus presence in patients. The most used test is the nasopharyngeal swab, used to amplify nucleic acids through polymerase chain reaction. Complications with this test have not been completely characterized. Until now, only one international report of cerebrospinal fluid leak has been reported. We present two cases of leak after nasopharyngeal swab test: the first case corresponded to an adult feminine gender patient with suspected idiopathic intracranial hypertension, whose gap was surgically repaired; the second case adult male patient with medical history of hydrocephalus and neonatal meningitis who was further studied for rhinoliquorrhea that showed a meningoencephalocele occupying the right frontal recess.

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Resumen Los pacientes trasplantados presentan mayor vulnerabilidad a complicaciones infecciosas, no solo debido al uso de drogas inmunosupresoras, sino que también, a las enfermedades subyacentes que presentan y a la falla de órganos primarios. A pesar de que las infecciones otorrinolaringológicas no son frecuentes en estos pacientes, es importante establecer un adecuado estudio y tratamiento de ellas. A través del siguiente artículo se aportan directrices en el estudio pretrasplante desde un enfoque otorrinolaringológico, generando recomendaciones de acuerdo a la patología del paciente y el órgano a trasplantar. Si bien, las recomendaciones se realizan según evaluación rinosinusal, otológica y faringoamigdalina, una adecuada anamnesis y examen físico son los pilares de la evaluación pretrasplante en otorrinolaringología, reservándose el estudio con imágenes para aquellos pacientes con alteraciones sospechosas.

Abstract Transplanted patients have higher frequency of infectious complications, not only due to the use of immunosuppressive drugs, but also the underlying diseases that present and the failure of primary organs. Although ear, nose and throat (ENT) infections are not frequent in these patients, it is important to establish an adequate study and treatment of them. Through the following article, guidelines are provided in the pretransplant study from an ENT approach, generating recommendations according to the pathology of the patient and the organ to be transplanted. Although, the recommendations are made according to rhinosinusal, otological and pharyngotonsiline evaluation, adequate anamnesis and physical examination are the pillars of the pretransplant evaluation in otolaryngology, reserving the study with images for patients with suspicious alterations.

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El osteoma es el tumor más frecuente de los senos paranasales, habitualmente asintomático debido a su lento crecimiento, sin embargo, pueden desarrollarse síntomas dependiendo del tamaño, localización y extensión, con potencial compromiso de órbita y cerebro. La cirugía está indicada en casos sintomáticos pudiendo realizarse abordaje externo, endoscópico o combinado. Presentamos un caso de osteoma etmoidal con compromiso orbitario resuelto, manejado por medio de la cirugía endoscópica nasal, con apoyo de navegación.

The osteoma is the most common tumor of the paranasal sinuses, is usually asymptomatic because of their slow growth, however, may develop symptoms depending on the size, location and extent, with potential compromise of orbit and brain. Surgery is indicated in symptomatic cases, with external, endoscopic or combined approach. We present a case of ethmoidal osteoma with orbital involvement managed by endoscopic image guided surgery.

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Introducción: La prueba Visual Subjetiva Vertical (SVV por sus siglas en inglés) corresponde a una prueba de bajo costo y complejidad que permite el estudio de la función vestibular "estática". En el año 2009 se valida la Prueba del Balde con igual confianza, sensibilidad y especificidad, que la prueba de domo. Sin embargo, diversos factores impresionan disminuir su precisión. Objetivo: Proponer un nuevo método utilizando un programa computacional y una interfaz pantalla-paciente, que permita disminuir la influencia de variables y aumentar la precisión de la evaluación. Material y método: En 43 voluntarios sin historia de patología vestibular y en 32 pacientes con patología vestibular se compararon los resultados de la aplicación de SVV en dos modalidades: prueba del balde tradicionalyuna prueba computarizada propuesta en el presente artículo. Resultados: En nuestro estudio el SVV con balde muestra 57% de sensibilidad y 90% de especificidad, mientras el SVV digital tiene 74% de sensibilidad y 93% de especificidad, el cual también presentó significativamente una menor desviación estándar. Conclusión: En suma, el SVV computarizado arroja un resultado más preciso que SVV con balde, con mejor utilidad clínica al tener mayor de discriminación con mejores perfiles de sensibilidad/especificidad.

Background: Subjective Visual Vertical Test (SVV) is a low-cost and simple evaluation that allows the physician to study the static vestibular function of a patient. In 2009 the Bucket Test was validated as a high confidence, sensitivity and specificity comparable to the hemispheric dome testing device. Although, its result can be affected by multiple variables. Aim: To propose a new method to evaluate SVV using a computer software interface, that allows a reduction ofvariables therefore increasing its precision. Material and method: In a sample of 43 volunteers with no previous history of vestibular pathologies and 32 patients with diagnosed vestibular pathologies we compared the results of 2 different modules of SVV testing: a traditional bucket test and a computerized test proposed in the present article. Results: Bucket test SVV for this research showed a sensitivity of 57% and a specificity of 90%, meanwhile Computerized SVV had a sensitivity of 74% and a specificity of 93%, which also presented a significant smaller standard deviation. Conclusion: In summary, digital SVV testing grants more accurate result in comparison to the Bucket Test, with a better clinical performance due to an improved discriminatory capacity with better Sensitivity/Specificity profiles.

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Introducción: Los cánceres de cabeza y cuello (CCyC) son reconocibles precozmente mediante la cínica y exámenes poco invasivo, sin embargo, existe importante demora entre las primeras molestias del paciente y el tratamiento. Objetivo: Describir los tiempos involucrados entre los primeros síntomas y el tratamiento. Material y método: Estudio descriptivo retrospectivo, mediante evaluación de fichas de pacientes diagnosticados y tratados por CCyC en otorrinolaringología del Hospital San Juan de Dios durante 18 meses. Resultados: Fueron elegibles 33 casos. El 93,7% correspondieron a carcinomas escamosos. Fueron comprometidos principalmente laringe (45,4%) y orofaringe (24,2%). El 90,2% se diagnosticó en estadio avanzado. Los pacientes demoraron 17 semanas en consultar desde sus primeros síntomas. Pasó una semana para ser evaluados por el especialista. Este tardó una semana en obtener una biopsia. El resultado histológico tomó tres semanas y el tratamiento se realizó a las cinco semanas. Quienes recibieron cirugía como primer tratamiento tardaron cuatro semanas en recibirla. Quienes fueron a quimiorradioterapia como coadyuvancia esperaron 11,5 semanas. Mientras, quienes recibieron quimiorradioterapia como único tratamiento, tardaron 8 semanas. Conclusión: Los principales retrasos en el manejo de estos pacientes son: la demora del paciente en consultar, el informe histológico y el acceso al tratamiento al conocerse el diagnóstico, especialmente cuando el tratamiento es la radio-quimioterapia.

Introduction: Head and neck cancers (HNC) are recognizable by clinical and early minimally invasive tests, however, there is significant delay between the first symptoms and treatment. Aim: To describe the times involved between the first symptoms and treatment. Material and method: Descriptive and retrospective study, by evaluating records of patients diagnosed and treated for HNC in otolaryngology at the Hospital San Juan de Dios, for 18 months. Results: 33 cases were eligible. 937% corresponded to squamous cell carcinoma. The sites most committed were larynx (45.4%) and (24.2%); the diagnosis was made in advanced stages in 90.2% of the cases. The patients took 17 weeks to consult since their first symptoms. It took 1 week to be evaluated by the specialist. It took 1 week to get a biopsy. The histological result took 3 weeks and treatment was performed at 5 weeks. Who received surgery as first treatment took 4 weeks to receive it. Who went to chemo-radiotherapy as co-adjuvant waited 11.5 weeks. Those receiving chemo-radiotherapy as the only treatment, 8 weeks. Conclusion: The major delays are the patient delay in consulting, the time delay in the histological report and access to treatment when knowing the diagnosis, especially when treatment is radio-chemotherapy.

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Introducción: La cirugía guiada por imágenes corresponde a una herramienta quirúrgica que comienza a desarrollarse a mediados del siglo XX. En 1990 comienza a utilizarse en otorrinolaringología, siendo sus principales indicaciones la cirugía endoscópica de cavidades paranasales y la cirugía de base de cráneo anterior. Objetivo: Analizar y presentar el resultado del uso de cirugía guiada por imágenes en pacientes intervenidos en el Hospital Clínico de la Universidad de Chile (HCUCH). Material y método: Se realizó un estudio retrospectivo incluyendo todos los casos de cirugía endoscópica nasosinusal y base de cráneo asistida por imágenes en HCUCH. La selección para usar la navegación se hizo en base a las recomendaciones de la Academia Americana de Otorrinolaringología. Resultados: De un total de 12 pacientes intervenidos con el uso de navegación, se obtuvo 100% de éxito quirúrgico con disminución de los síntomas y sin complicaciones intraoperatorias. Conclusión: La cirugía asistida por navegación en cavidades paranasales y base de cráneo, es una herramienta de suma utilidad en casos seleccionados que potencia las habilidades quirúrgicas del cirujano sin reemplazar sus conocimientos anatómicos. Otorga seguridad y precisión en cirugías que comprometen estructuras nobles como base de cráneo y órbita entre otros.

Introduction: Image Guided Surgery is a surgical tool that develop in the mid-twentieth century. In 1990 it began to be used in otolaryngology, being its main indications endoscopic surgery of paranasal sinuses and anterior skull base. Aim: To analyze and present the result of image-guided surgery in patients undergoing surgery at the Hospital of the University of Chile. Material and method: A retrospective study included all cases of endoscopic sinus surgery and skull base imaging assisted at the Clinical Hospital of the University of Chile from August 2015 to August 2016. The choice to use the navigation was made in based on the recommendations of the American Academy of Otolaryngology, and analyzed case by case. Results: A total of 12 patients were operated using Navigation, achieving 100 % of surgical success with decreased symptoms and without intraoperative complications. Conclusion: Image Guided Surgery in paranasal sinuses and skull base is a tool very useful in selected cases where enhances the surgeon skills without replacing their anatomical knowledge. Provides security and accuracy in surgeries involving noble structures such as the skull base, orbit among others. their anatomical knowledge. Provides security and accuracy in surgeries involving noble structures such as the skull base, orbit among others.

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BACKGROUND: Complicated skin and skin structure infections (cSSSIs) are an important healthcare concern worldwide, as they can be life-threatening and challenging to treat. cSSSIs are normally managed using a combination of surgical intervention and prompt antibiotic use. New therapeutic options, including novel antibiotics, are required to improve outcomes in terms of duration of illness and to reduce the consumption of healthcare resources. METHODS: This was a prospective, randomized, open-label, parallel-group, multinational clinical study comparing sequential intravenous/oral (iv/po) moxifloxacin, 400 mg once daily, and iv amoxicillin/clavulanate, 1,000 mg/ 200 mg three times daily followed by po amoxicillin/ clavulanate, 500 mg/125 mg three times daily, for 7-21 days in hospitalized patients. RESULTS: A total of 804 patients were enrolled (mean age 51.8 years). The most common clinical diagnosis was complicated erysipelas (32.1% moxifloxacin; 30.0% amoxicillin/ clavulanate) and major abscess (31.1% moxifloxacin; 29.3% amoxicillin/clavulanate). Overall clinical success rates at the test-of-cure (TOC) visit (14-28 days post-treatment) for the per-protocol population (primary efficacy variable) were 80.6% (254/315) for patients in the moxifloxacin group and 84.5% (268/317) for those receiving amoxicillin/clavulanate (95% confidence interval [CI] -9.41, 2.18). Similar results were obtained for the intention-to-treat population (95% CI -7.56, 4.31). In both treatment groups, the highest clinical success rates were recorded for patients with complicated erysipelas, major abscess, surgical wound infection, and cellulitis. The lowest clinical cure rates were reported for diabetic foot infection and necrotizing fasciitis. In the microbiologically evaluable population, the bacteriological success rate (eradication and presumed eradication) was 76.0% (127/ 167) in the moxifloxacin group and 81.4% (140/172) in the amoxicillin/clavulanate group (95% CI -12.96, 4.41). Staphylococcus aureus (137 isolates) and Escherichia coli (50 isolates) were the most frequently isolated skin pathogens. Adverse event rates were comparable between treatment groups. CONCLUSIONS: Treatment with sequential iv/po moxifloxacin monotherapy once daily is clinically comparable to that with iv/po amoxicillin/clavulanate three times daily in the management of cSSSIs. Moxifloxacin's simple dose regimen offers an advantage over amoxicillin/clavulanate and represents a valuable addition to current antibiotic regimens used in the treatment of cSSSIs.

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Introducción: La estenosis grave de la arteria carótida es una causa importante de accidente vascular encefálico(AVE) y evento isquémico transitorio (TIA) (10-20 por ciento). La endarterectomía carotídea extracraneana (ECE) ha demostrado ser efectiva en reducir este riesgo en pacientes seleccionados, sintomáticos y asintomáticos. Objetivo: Presentar los resultados de una serie de pacientes sometidos a ECE. Métodos: Serie de 135 ECE en 121 sujetos (84 hombres y 37 mujeres), con mediana de 72,2 +/- 7,7 años, tratados con ECE en el Servicio de Cirugía Vascular del Hospital Dipreca entre enero de 1998 y diciembre de 2004. La operación consistió en endarterectomía carotídea (común e interna) luego de realizar arteriotomía longitudinal amplia y endarterectomía carotídea externa por eversión. En la mayoría de los casos se utilizó shunt y bloqueo anestésico cervical profundo y superficial; en todos se fijó la placa distal y arteriorráfia con parche. Se utilizó estadística descriptiva y se calculó porcentajes, medianas, promedios, desviaciones estándar y supervivencia. Resultados: El déficit neurológico central homolateral postoperatorio fue de 1,5 por ciento. La morbilidad general fue de 12,6 por ciento. No hubo mortalidad perioperatoria. Se obtuvo un 94 por ciento de seguimiento. La causa de muerte más frecuente fue la de origen cardíaco (74 por ciento) y hubo un 4,7 por ciento de eventos neurológicos tardíos (TIA o AVE). La supervivencia libre de re estenosis fue de 92 por ciento. Conclusión: La ECE sigue siendo una alternativa de tratamiento en nuestro Hospital con baja morbimortalidad en sujetos seleccionados con estenosis carotídea sintomática y asintomática.

Background: Critical carotid artery stenosis is an important cause of stroke (CVA) and transient ischemic attack (TIA). Extra cranial endarterectomy (ECE) has proven effective in reducing the risk of these complications in selected patients, both symptomatic and asymptomatic. Aim: To report the results of ECE at Dipreca Hospital in Santiago, Chile. Methods: From January 1998 to December 2004, 135 ECE procedures were performed in 121 patients (84 males and 37 females). Mean age was 72.2 years (SD 7.7). ECE consisted of common and external carotid artery endarterectomy with eversion. In most cases, superficial and deep anesthetic blockade and shunts were utilized. A patch and fixation of distal plaque were performed in all. Results are presented with standard statistics methods. Results: Homolateral postoperative neurologic deficit was observed in 1.5 percent. All cause morbidity was 12.6 percent. There was no perioperative mortality. Follow up data was obtained for 94 percent of patients. Seventy-four percent of late deaths were due to cardiac events and 4.7 percent of patients developed late neurologic events (CVA or TIA). Restenosis free survival was 92 percent. Conclusion: ECE is a safe procedure for patients with both symptomatic and asymptomatic carotid artery stenosis.

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In drug discovery programs, dimethyl sulfoxide (DMSO) is a standard solvent widely used in biochemical assays. Despite the extensive use and study of enzymes in the presence of organic solvents, for some enzymes the effect of organic solvent is unknown. Macromolecular targets may be affected by the presence of different solvents in such a way that conformational changes perturb their active site structure accompanied by dramatic variations in activity when performing biochemical screenings. To address this issue, in this work we studied the effects of two organic solvents, DMSO and methanol (MeOH), in the isothermal titration calorimetry (ITC) kinetic assays for the catalyzed reaction of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from Trypanosoma cruzi. The solvent effects on T. cruzi GAPDH had not yet been studied. This enzyme was shown here to be affected by the organic solvents content up to 5.0% for MeOH and up to 7.5% for DMSO. The results show that when GAPDH is assayed in the presence of DMSO (5%, v/v) using the ITC experiment, the enzyme exhibits approximately twofold higher activity than that of GAPDH with no cosolvent added. When MeOH (5%, v/v) is the cosolvent, the GAPDH activity is sixfold higher. The favorable effects of the organic solvents on the Michaelis-Menten enzyme-substrate complex formation ensure the consistency of the biological assays, structural integrity of the protein, and reproducibility over the measurement time. The reaction was also kinetically monitored by standard spectrophotometric assays to establish a behavioral performance of T. cruzi GAPDH when used for screening of potential inhibitors.

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Adenine phosphoribosyltransferase (APRT) enzyme from Leishmania tarentolae has been proposed as a target for the rational search of new leishmanicidal drugs. In this paper, we describe the evaluation of the inhibitory activity on L. tarentolae APRT enzyme of 46 crude extracts of Meliaceae and Rutaceae plants, besides three furoquinolone alkaloids. The results showed that 21 extracts were able to decrease the APRT enzymatic activity (IA% > or = 50). The methanolic extracts from roots and leaves of Cedrela fissilis and from fruits, branches and leaves of Cipadessa fruticosa have showed strong activities. Therefore, these species could be a promising source of lead compounds for the rational design of new leishmanicidal drugs. The phytochemical investigation of an active fraction from Almeidea rubra afforded the alkaloids isodutaduprine, isoskimmianine and isokokusagine, which showed low to moderate activity on APRT.

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Phosphoribosylpyrophosphate synthases (PRS; EC 2.7.6.1) are enzymes that are of central importance in several metabolic pathways in all cells. The sugar cane PRS enzyme contains 328 amino acids with a molecular weight of 36.6 kDa and represents the first plant PRS to be crystallized, as well as the first phosphate-independent PRS to be studied in molecular detail. Sugar cane PRS was overexpressed in Escherichia coli, purified and crystallized using the hanging-drop vapour-diffusion method. Using X-ray diffraction experiments it was determined that the crystals belong to the orthorhombic system, with space group P2(1)2(1)2 and unit-cell parameters a = 213.2, b = 152.6, c = 149.3 A. The crystals diffract to a maximum resolution of 3.3 A and a complete data set to 3.5 A resolution was collected and analysed.

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Several natural compounds have been identified for the treatment of leishmaniasis. Among them are some alkaloids, chalcones, lactones, tetralones, and saponins. The new compound reported here, 7-geranyloxycoumarin, called aurapten, belongs to the chemical class of the coumarins and has a molecular weight of 298.37. The compund was extracted from the Rutaceae species Esenbeckia febrifuga and was purified from a hexane extract starting from 407.7 g of dried leaves and followed by four silica gel chromatographic fractionation steps using different solvents as the mobile phase. The resulting compound (47 mg) of shows significant growth inhibition with an LD50 of 30 æM against the tropical parasite Leishmania major, which causes severe clinical manifestations in humans and is endemic in the tropical and subtropical regions. In the present study, we investigated the atomic structure of aurapten in order to determine the existence of common structural motifs that might be related to other coumarins and potentially to other identified inhibitors of Leishmania growth and viability. This compound has a comparable inhibitory activity of other isolated molecules. The aurapten is a planar molecule constituted of an aromatic system with electron delocalization. A hydrophobic side chain consisting of ten carbon atoms with two double bonds and negative density has been identified and may be relevant for further compound synthesis.

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Several natural compounds have been identified for the treatment of leishmaniasis. Among them are some alkaloids, chalcones, lactones, tetralones, and saponins. The new compound reported here, 7-geranyloxycoumarin, called aurapten, belongs to the chemical class of the coumarins and has a molecular weight of 298.37. The compound was extracted from the Rutaceae species Esenbeckia febrifuga and was purified from a hexane extract starting from 407.7 g of dried leaves and followed by four silica gel chromatographic fractionation steps using different solvents as the mobile phase. The resulting compound (47 mg) of shows significant growth inhibition with an LD50 of 30 microM against the tropical parasite Leishmania major, which causes severe clinical manifestations in humans and is endemic in the tropical and subtropical regions. In the present study, we investigated the atomic structure of aurapten in order to determine the existence of common structural motifs that might be related to other coumarins and potentially to other identified inhibitors of Leishmania growth and viability. This compound has a comparable inhibitory activity of other isolated molecules. The aurapten is a planar molecule constituted of an aromatic system with electron delocalization. A hydrophobic side chain consisting of ten carbon atoms with two double bonds and negative density has been identified and may be relevant for further compound synthesis.

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Avaliou-se a técnica de imunofluorescência indireta (IFA) na detecção de anticorpos contra o vírus da imunodeficiência felina (FIV) numa pesquisa epidemiológica do FIV na Argentina. A IFA foi modificada e comparada com duas outras técnicas imunológicas: western blot (WB) e imunocromatografia em camadas (SI) com kit comercial e também com reação em cadeia de polimerase (PCR) para detecção do DNA proviral. A IFA mostrou ser um teste com alta sensibilidade e especificidade e poderá ser empregada como ferramenta útil em estudos epidemiológicos. A baixa porcentagem de reatividade não específica pode ser esclarecida com testes mais avançados ou usando métodos alternativos.

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This study evaluated an indirect immunofluorescence assay (IFA) to detect feline immunodeficiency virus infection (FIV) antibody in a comprehensive epidemiological survey of FIV in Argentina. IFA modified in our laboratory, was compared with two other immunoassays, western blot (WB) and a sandwich immunochromatographic commercial kit (SI), and also with a direct polymerase chain reaction (PCR) method that detects proviral DNA. IFA showed to be a test with high sensitivity and specificity, and could be useful as a diagnostic tool in epidemiological studies. The presence of a low percentage of results with non-specific reactivity in the IFA could be resolved with further testing or use of an alternative method.(AU)

Avaliou-se a técnica de imunofluorescência indireta (IFA) na detecção de anticorpos contra o vírus da imunodeficiência felina (FIV) numa pesquisa epidemiológica do FIV na Argentina. A IFA foi modificada e comparada com duas outras técnicas imunológicas: western blot (WB) e imunocromatografia em camadas (SI) com kit comercial e também com reação em cadeia de polimerase (PCR) para detecção do DNA proviral. A IFA mostrou ser um teste com alta sensibilidade e especificidade e poderá ser empregada como ferramenta útil em estudos epidemiológicos. A baixa porcentagem de reatividade não específica pode ser esclarecida com testes mais avançados ou usando métodos alternativos.(AU)

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The three-dimensional structure of Leishmania tarentolae adenine phosphoribosyltransferase (APRT) in complex with adenosine-5-monophosphate (AMP) and a phosphate ion has been solved. Refinement against X-ray diffraction data extending to 2.2-A resolution led to a final crystallographic R factor of 18.3%. Structural comparisons amongst this APRT enzyme and other 'type I' PRTases whose structures have been determined reveal several important features of the PRTases catalytic mechanism. Based on structural superpositions and molecular interaction potential calculations, it was possible to suggest that the PRPP is the first substrate to bind, while the AMP is the last product to leave the active site, in accordance to recent kinetic studies performed with the Leishmania donovani APRT.

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The second enzyme in the glycolytic pathway, phosphoglucose isomerase (PGI), catalyses an intracellular aldose-ketose isomerization. Here we describe the human recombinant PGI structure (hPGI) solved in the absence of active site ligands. Crystals isomorphous to those previously reported were used to collect a 94% complete data set to a limiting resolution of 2.1 A. From the comparison between the free active site hPGI structure and the available human and rabbit PGI (rPGI) structures, a mechanism for protein initial catalytic steps is proposed. Binding of the phosphate moiety of the substrate to two distinct elements of the active site is responsible for driving a series of structural changes resulting in the polarisation of the active site histidine, priming it for the initial ring-opening step of catalysis.

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The structure of the glycosomal glyceraldehyde-3-phosphate dehydrogenase (gGAPDH) from Trypanosoma cruzi complexed with chalepin, a natural product from Pilocarpus spicatus, has been determined by X-ray crystallography to 1.95 A resolution. The structure is in the apo form without cofactors in the subunits of the tetrameric gGAPDH in the asymmetric unit. Unequivocal density corresponding to the inhibitor was clearly identified in one monomer. The final refined model of the complex shows extensive conformational changes when compared with the native structure. The mode of binding of chalepin to gGAPDH and its implications for inhibitor design are discussed.

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