Browsing by Author "Palma, Carlos"
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- ItemDetección del SARS-CoV-2 mediante RT-qPCR utilizando saliva en pacientes ambulatorios con estudio de COVID-19(2022) Perret Pérez, Cecilia; Abarca Villaseca, Katia; Solari Gajardo, Sandra; Aguilera, Pablo; García-Huidobro Munita, Diego Nicolas; Olivares, Felipe; Palma, Carlos; Contreras, Ana María; Martínez Valdebenito, Constanza Pamela; Ferrés, MarcelaLa pandemia de COVID-19 ha afectado a millones de personas en todo el mundo. La identificación de sujetos infectados ha sido importante para el control. Objetivo: Evaluar el rendimiento deuna reacción de polimerasa en cadena (RPC) cuantitativa en tiempo real (en inglés: RT-qPCR) para SARS-CoV-2, utilizando saliva como matriz en comparación con un hisopado nasofaríngeo (HNF). Metodología: Se reclutaron adultos en atención ambulatoria, la mayoría sintomáticos. Fueron estudiadas 530 muestras pareadas de saliva e HNF con RT-qPCR. Resultados: Fueron positivas 59 muestras de HNF y 54 de saliva. La sensibilidad con saliva fue 91%, especificidad 100%, el valor predictor positivo (VPP) 100%, valor predictor negativo (VPN) 98%. El índice Kappa fue de 0,95 y LR-0,08. En promedio, el umbral de ciclo (en inglés cycle threshold-CT) de la saliva fue 3,99 puntos más alto que los de HNF (p < 0,0001) mostrando que la carga viral (CV) es menor en saliva. La carga viral en ambas disminuyó con el tiempo después del inicio de los síntomas. El muestreo de saliva fue preferido por los sujetos en lugar de HNF. Conclusión: Este estudio demuestra que la RPC para SARS-CoV-2 utilizando saliva, es adecuada para el diagnóstico de COVID-19 en adultos ambulatorios,especialmente en la etapa temprana de los síntomas.
- ItemDrug resistance mutations in proviral DNA of HIV-infected patients with low level of viremia(2020) Villalobos, Camila; Elena Ceballos, Maria; Ferres, Marcela; Palma, Carlos
- ItemEmotion Recognition from ECG Signals Using Wavelet Scattering and Machine Learning(2021) Sepulveda, Axel; Castillo, Francisco; Palma, Carlos; Rodriguez-Fernandez, MariaAffect detection combined with a system that dynamically responds to a person's emotional state allows an improved user experience with computers, systems, and environments and has a wide range of applications, including entertainment and health care. Previous studies on this topic have used a variety of machine learning algorithms and inputs such as audial, visual, or physiological signals. Recently, a lot of interest has been focused on the last, as speech or video recording is impractical for some applications. Therefore, there is a need to create Human-Computer Interface Systems capable of recognizing emotional states from noninvasive and nonintrusive physiological signals. Typically, the recognition task is carried out from electroencephalogram (EEG) signals, obtaining good accuracy. However, EEGs are difficult to register without interfering with daily activities, and recent studies have shown that it is possible to use electrocardiogram (ECG) signals for this purpose. This work improves the performance of emotion recognition from ECG signals using wavelet transform for signal analysis. Features of the ECG signal are extracted from the AMIGOS database using a wavelet scattering algorithm that allows obtaining features of the signal at different time scales, which are then used as inputs for different classifiers to evaluate their performance. The results show that the proposed algorithm for extracting features and classifying the signals obtains an accuracy of 88.8% in the valence dimension, 90.2% in arousal, and 95.3% in a two-dimensional classification, which is better than the performance reported in previous studies. This algorithm is expected to be useful for classifying emotions using wearable devices.
- ItemExactitud y utilidad diagnóstica de la IgM en infecciones por Bartonella henselae(2013) Abarca Villaseca, Katia; Winter, Matías; Marsac, Delphine; Palma, Carlos; Contreras, Ana M.; Ferrés Garrido, Marcela Viviana
- ItemSARS-CoV-2 infectivity and antigenic evasion: spotlight on isolated Omicron sub-lineages(2024) Barrera, Aldo; Martinez-Valdebenito, Constanza; Angulo, Jenniffer; Palma, Carlos; Hormazabal, Juan; Vial, Cecilia; Aguilera, Ximena; Castillo-Torres, Pablo; Pardo-Roa, Catalina; Balcells, Maria Elvira; Nervi, Bruno; Le Corre, Nicole; Ferres, MarcelaSince the SARS-CoV-2 outbreak in 2019, a diversity of viral genomic variants has emerged and spread globally due to increased transmissibility, pathogenicity, and immune evasion. By the first trimester of 2023 in Chile, as in most countries, BQ and XBB were the predominant circulating sub-lineages of Omicron. The molecular and antigenic characteristics of these variants have been mainly determined using non-authentic spike pseudoviruses, which is often described as a limitation. Additionally, few comparative studies using isolates from recent Omicron sub-lineages have been conducted. In this study, we isolated SARS-CoV-2 variants from clinical samples, including the ancestral B.1.1, Delta, Omicron BA.1, and sub-lineages of BA.2 and BA.5. We assessed their infectivity through cell culture infections and their antibody evasion using neutralization assays. We observed variations in viral plaque size, cell morphology, and cytotoxicity upon infection in Vero E6-TMPRSS2 cells for each variant compared to the ancestral B.1.1 virus. BA.2-derived sub-variants, such as XBB.1.5, showed attenuated viral replication, while BA.5-derived variants, such as BQ.1.1, exhibited replication rates similar to the ancestral SARS-CoV-2 virus. Similar trends were observed in intestinal Caco-2 cells, except for Delta. Antibody neutralization experiments using sera from individuals infected during the first COVID-19 wave (FWI) showed a consistent but moderate reduction in neutralization against Omicron sub-lineages. Interestingly, despite being less prevalent, BQ.1.1 showed a 6.1-fold greater escape from neutralization than XBB.1.5. Neutralization patterns were similar when tested against sera from individuals vaccinated with 3xBNT162b2 (PPP) or Coronavac-Coronavac-BNT162b2 (CCP) schedules. However, CCP sera showed 2.3-fold higher neutralization against XBB.1.5 than FWI and PPP sera. This study provides new insights into the differences between BA.2 and BA.5-derived variants, leading to their eventual outcompetition. Our analysis offers important evidence regarding the balance between infectivity and antigenic escape that drives the evolution of second-generation SARS-CoV-2 variants in the population.
- ItemViral shedding and viraemia of Andes virus during acute hantavirus infection: a prospective study(2024) Ferres, Marcela; Martinez-Valdebenito, Constanza; Henriquez, Carolina; Marco, Claudia; Angulo, Jenniffer; Barrera, Aldo; Palma, Carlos; Pinto, Gonzalo Barriga; Cuiza, Analia; Ferreira, Leonila; Rioseco, Maria Luisa; Calvo, Mario; Fritz, Ricardo; Bravo, Sebastian; Bruhn, Alejandro; Graf, Jeronimo; Llancaqueo, Alvaro; Rivera, Gonzalo; Cerda, Carolina; Tischler, Nicole; Valdivieso, Francisca; Vial, Pablo; Mertz, Gregory; Vial, Cecilia; Le Corre, NicoleBackground Andes virus (ANDV) is a zoonotic Orthohantavirus leading to hantavirus cardiopulmonary syndrome. Although most transmissions occur through environmental exposure to rodent faeces and urine, rare person -toperson transmission has been documented, mainly for close contacts. This study investigates the presence and infectivity of ANDV in body fluids from confirmed cases and the duration of viraemia. Methods In this prospective study, 131 participants with confirmed ANDV infection were enrolled in Chile in a prospective study between 2008 and 2022. Clinical samples (buffy coat, plasma, gingival crevicular fluid [GCF], saliva, nasopharyngeal swabs [NPS], and urine) were collected weekly for 3 weeks together with clinical and epidemiological data. Samples were categorised as acute or convalescent (up to and after 16 days following onset of symptoms). Infectivity of positive fluids was assessed after the culture of samples on Vero E6 cells and use of flow cytometry assays to determine the production of ANDV nucleoprotein. Findings ANDV RNA was detected in 100% of buffy coats during acute phase, declining to 95% by day 17, and to 93% between days 23-29. ANDV RNA in GCF and saliva decreased from 30% and 12%, respectively, during the acute phase, to 12% and 11% during the convalescent phase. Successful infectivity assays of RT-qPCR-positive fluids, including GCF, saliva, NPS, and urine, were observed in 18 (42%) of 43 samples obtained during the acute phase of infection. After re -culture, the capacity to infect Vero E6 cells was maintained in 16 (89%) of 18 samples. Severity was associated with the presence of ANDV RNA in one or more fluids besides blood (odds ratio 258 [95% CI 142-518]). Interpretation ANDV infection is a systemic and viraemic infection, that affects various organs. The presence of infectious particles in body fluids contributes to our understanding of potential mechanisms for person -to -person transmission, supporting the development of preventive strategies. Detection of ANDV RNA in additional fluids at hospital admission is a predictor of disease severity. Funding National Institutes of Health and Agencia de Investigaci & oacute;n y Desarrollo. Copyright (c) 2024 Elsevier Ltd. All rights reserved.