Overview of extracellular vesicles in pathogens with special focus on human extracellular protozoan parasites

Extracellular vesicles (EVs) are lipid-bilayered membrane-delimited particles secreted by almost any cell type, involved in different functions according to the cell of origin and its state. From these, cell to cell communication, pathogen-host interactions and modulation of the immune response have been widely studied. Moreover, these vesicles could be employed for diagnostic and therapeutic purposes, including infections produced by pathogens of diverse types; regarding parasites, the secretion, characterisation, and roles of EVs have been studied in particular cases. Moreover, the heterogeneity of EVs presents challenges at every stage of studies, which motivates research in this area. In this review, we summarise some aspects related to the secretion and roles of EVs from several groups of pathogens, with special focus on the most recent research regarding EVs secreted by extracellular protozoan parasites.

Futuro de la terapia y el diagnóstico con vesículas extracelulares / Future of therapeutics and diagnostics with extracellular vesicles

Resumen Las vesículas extracelulares son nanoparticulas secretadas por células procariotas y eucariotas, con funciones variadas que van desde la comunicación intercelular hasta la modulación de la respuesta inmune. La investigación en este tema se enfocó inicialmente en el aislamiento, identificación y caracterización, para luego abarcar los mecanismos fisiológicos en los que se ven involucradas. Más recientemente, la investigación, particularmente centrada en exosomas, ha permitido abrir campo a novedosas hipótesis sobre su utilidad en inmunoterapia y como marcadores biológicos. Esta revisión explora aspectos básicos sobre la biogénesis y la composición de los exosomas, así como su uso en diagnóstico y tratamiento, a partir del conocimiento generado sobre su aislamiento y purificación, distribución de cargos específicos y su relación con la respuesta inmune. Los hallazgos sobre su aplicabilidad en procesos cancerosos son promisorios; sin embargo, existe toda una ventana de posibilidades para investigar esta plataforma molecular como potenciales vacunas acelulares y marcadores de pronóstico, diagnóstico y alerta, tanto en cáncer como en patologías causadas por agentes infecciosos.

Abstract Extracellular vesicles are nanoparticles released by prokaryotic and eukaryotic cells, with a variety of functional roles in intercellular communication and even in modulation of the immune response. Research in this topic was initially focused on isolation, identification and characterization of the vesicles, with subsequent understanding of the physiological mechanisms in which they are involved. Furthermore, recent studies, particularly with exosomes, have opened the field to novel hypotheses about their usefulness in immunotherapy and as biological markers. This review explores general aspects about the biogenesis and composition of exosomes, as well as their potential use in diagnosis and treatment, based on the knowledge generated about their isolation, production, cargoes, delivery engineering and relationship with the immune response. The findings on its applicability in cancerous processes are promising, but there is still a variety of investigation possibilities of this molecular platforms as cell-free vaccines and as prognostic, diagnostic and/or warning markers, both in cancer but also in infectious diseases.

Potentially pathogenic Acanthamoeba genotype T4 isolated from dental units and emergency combination showers

BACKGROUND Acanthamoeba is the genus of free-living amoebae that is most frequently isolated in nature. To date, 20 Acanthamoeba genotypes have been described. Genotype T4 is responsible for approximately 90% of encephalitis and keratitis cases. Due to the ubiquitous presence of amoebae, isolation from environmental sources is not uncommon; to determine the clinical importance of an isolation, it is necessary to have evidence of the pathogenic potential of amoebae. OBJECTIVE The aim of this study was to physiologically characterise 8 Acanthamoeba T4 isolates obtained from dental units and emergency combination showers and to determine their pathogenic potential by employing different laboratory techniques. METHODS Eight axenic cultures of Acanthamoeba genotype T4 were used in pathogenic potential assays. Osmotolerance, thermotolerance, determination and characterisation of extracellular proteases and evaluation of cytopathic effects in MDCK cells were performed. FINDINGS All of the isolates were osmotolerant, thermotolerant and had serine proteases from 44-122 kDa. Two isolates had cytopathic effects on the MDCK cell monolayer. MAIN CONCLUSION The presence of Acanthamoeba T4 with pathogenic potential in areas such as those tested in this study reaffirms the need for adequate cleaning and maintenance protocols to reduce the possibility of infection with free-living amoebae.

An indirect immunofluorescence antibody test employing whole eggs as the antigen for the diagnosis of abdominal angiostrongyliasis

Abdominal angiostrongyliasis is a potentially fatal zoonotic disease with a broad geographical distribution throughout Central and South America. This study assessed the performance of Angiostrongylus costaricensis eggs as the antigen in an indirect immunofluorescence assay for the determination of parasite-specific IgG and IgG1 antibodies. For prevalence studies, an IgG antibody titre > 16 was identified as the diagnostic threshold with the best performance, providing 93.7 percent sensitivity and 84.6 percent specificity. Cross reactivity was evaluated with 65 additional samples from patients with other known parasitic infections. Cross reactivity was observed only in samples from individuals infected with Strongyloides stercoralis. For clinical diagnosis, we recommend the determination of IgG only as a screening test. IgG1 determination may be used to increase the specificity of the results for patients with a positive screening test.

Cyclospora cayetanensis: revisión de cuatro casos clínicos / Cyclospora cayetanensis: review of four clinical cases

Cyclospora cayetanensis es un protozoario coccidio que afecta el intestino delgado del ser humano. Es el agente causal de la ciclosporiasis, una enfermedad que se caracteriza por una diarrea profusa que conlleva a ausentismo laboral temporal y que en algunos casos, de acuerdo a su severidad y al estado inmune del paciente, puede llevar incluso a la muerte. A cyclospora cayetanensis se le ha considerado desde inicios de los años noventa como responsable de una serie de brotes diarreicos asociados con agua y alimentos, especialmente en los Estados Unidos y Canadá. En Costa Rica son pocos los casos reportados de estas parasitosis en el laboratorio clínico, y el parásito es considerado aún por muchos profesionales como un organismo exótico. En este trabajo se presentan cuatro casos clínicos de ciclosporiasis, atendidos en un período de 15 días en lña Clínica Dr. Marcial Fallas, en el cantón de Desamparados. Se hace una revisión de las características de Cyclospora cayetanensis y se insiste en la necesidad de considerar a este parásito como posible agente causal de diarreas de origen abrupto.

Cyclospora cayetanensis is a coccidian protozoan which attaches the small intestine of the human being. It is the etiological agent of cyclosporiasis, a disease characterized by profuse diarrhea that leads to temporary sick leave and in some cases, depending on the severity of the illness and the immunologic condition of the patient, may lead to death. Since the 90’s Cyclospora cayetanensis has been considered responsible for a series of diarrheic outbreaks related to food and water, especially in USA and Canada. In Costa Rica few cases of this parasitosis have been reported in the clinical laboratory, and this parasite is still considered by many healthcare professionals as an exotic organism. This work presents four clinical cases of cyclosporiasis detected throughout...

Prevalencia de parásitos intestinales en escolares de Limón centro, Costa Rica / Prevalence of intestinal parasites in students of Limon center, Costa Rica

Se recolectaron 898 muestras de heces de escolares de cinco centros educativos de la provincia de limón y se analizaron en el laboratorio de Helmintología de la Universidad de Costa Rica mediante examen al fresco y técnica de Kato. Las muestras colectadas provenían de los siguientes centros educativos Cieneguita (243), Atilia Mata (108), Tomás Guardia (287), Los Lirios (72) y Limoncito (188). Los resultados del examen coproparasitológico indicaron una positividad del 47.6 por ciento entre organismos parásitos y comensales. Los centros educativos con mayor índice de positividad fueron Los Lirios (71.4 por ciento) y Cieneguita (63.9 por ciento). Los niños de tercer y quinto nivel escolar presentaron el mayor índice de infección (20 por ciento) y las especies parásitas con mayor prevalencia fueron Ascaris lumbricoides (16.6 por ciento), Trichuris trichiura (18.6 por ciento) y Giardia duodenalis (7 por ciento). La prevalencia de uncinarias en este estudio fue del 3 por ciento. Las últimas encuestas nacionales sobre parasitismo intestinal en Costa Rica revelaron una dramática disminución de dichas enfermedades, a la vez que alertaron sobre la alta prevalencia en las zonas marginales y rurales del país. Los resultados de este estudio reflejan severas deficiencias en la infraestructura sanitaria y en los hábitos higiénicos de la población estudiada, lo que sugiere un alto índice de contaminación fecal y mala disposición de excretas. Estos datos deben llamar la atención de las autoridades de Salud de Costa Rica hacia las necesidades de la población escolar infantil de la ciudad de Limón, una de las más pobres y con mayor desempleo del país.

Fecal samples of children from five elementary schools of the province of Limón, Costa Rica were analyzed at the Helminthology laboratory of the University of Costa Rica by means of direct smears and Kato methods. The 898 samples were from the schools of: Cieneguita (243), Atilia Mata (108), Tomás Guardia (287), Los Lirios (72) and Limoncito (188). The results showed that 47.6% of the children were positive for parasites (pathogenic and commensal organisms). The elementary schools with the highest positivity were Los Lirios (71.4%) and Cieneguita (63.9%). Children from third and fifth grade showed the highest infection rates (20%) and the most prevalent parasites were Ascaris lumbricoides (16.65), Trichuris trichiura (18.6%) and Lamblia intestinalis (7%). The prevalence of hookworms was 3%. The last national surveys of parasites in Costa Rica (1982, 1996), showed a dramatic reduction in intestinal helmintiasis and at the same time highlights that the prevalence of parasites is higher in marginal and rural communities. Our results reveal deep deficiencies in life conditions and hygiene, demonstrated with the high level of fecal contamination and an inadequate disposition of stools. The present study calls the attention of the health authorities about the needs of the children population in this province, the poorest and with the highest level of unemployment in the country.