Browsing by Author "Ferrés, Marcela"

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    Búsqueda de mutaciones en el gen UL 97 asociadas a resistencia a ganciclovir en citomegalovirus obtenidos desde muestras biológicas de pacientes chilenos
    (2010) Oyarzún Andrade, María Angélica; Bustos, Patricia; González Agüero, Marcela Margot; Domínguez Moreno, María Isabel; Aguayo González, Francisco Renan; Nervi Nattero, Bruno; Ferrés, Marcela
    Background: Long term use of ganciclovir (GCV) is associated with acquired resistance to it. Ninety percent of the responsible mutations occur in cytomegalovirus (CMV) UL97 gene. Aim: To search for these mutations, comparing nucleotide sequences of CMV-positive samples from post transplant and immunocompromised patients receiving GCV, with sequences of CMV isolates obtained from subjects not exposed to the drug. Patients and Methods: Codons 440 to 465 of gene UL97, including the most common mutations causing resistance to GCV, were amplified in 33 plasma samples from patients exposed to GCV and in 15 urine samples of newborns. Both populations and their nucleotide sequences were compared with the prototype strain CMV AD169. Results: Samples of exposed patients had multiple mutations but only one had a mutation associated with clinical resistance (M4601). Eight subjects had the D605E mutation, whose role in resistance is controversial. The remaining 150 mutations were silent mutations. Conclusions: A low frequency of mutations associated with CMV resistance to GCV was found in these exposed and unexposed samples. These mutations may reflect coexistence of multiple genetic variants of CMV. The absence of clinical expression of resistance, even with these mutations, can be explained by the use of GCV for a shorter lapse than that associated with the appearance of resistance. (Rev Med Chile 2010; 138: 421-427).
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    Correlation between female sex, IL28B genotype, and the clinical severity of bronchiolitis in pediatric patients
    (2020) Astudillo, P.; Angulo, J.; Pino, K.; de Carvalho, J. B.; de Morais, G. L.; Perez, S.; de Vasconcelos, A. T. R.; Ferrés, Marcela; López Lastra, Marcelo Andrés
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    Detección del SARS-CoV-2 mediante RT-qPCR utilizando saliva en pacientesambulatorios con estudio de COVID-19
    (2022) Perret Perez, Cecilia; Abarca Villaseca, Katia; Solari Gajardo, Sandra; Aguilera, Pablo; Garcia-huidobro Munita, Diego Nicolas; Olivares, Felipe; Palma, Carlos; Contreras, Ana María; Martinez Valdebenito, Constanza Pamela; Ferrés, Marcela
    La pandemia de COVID-19 ha afectado a millonesde personas en todo el mundo. La identificación de sujetos infectadosha sido importante para el control. Objetivo: Evaluar el rendimiento deuna reacción de polimerasa en cadena (RPC) cuantitativa en tiemporeal (en inglés: RT-qPCR) para SARS-CoV-2, utilizando saliva comomatriz 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.
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    Insights into neutralizing antibody responses in individuals exposed to SARS-CoV-2 in Chile
    (2021) Beltrán Pavez, Carolina; Riquelme Barrios, Sebastián; Oyarzún Arrau, Aarón; Gaete Argel, Aracelly; González Stegmaier, Roxana; Cereceda Solis, Karina; Aguirre, Adam; Travisany, Dante; Palma Vejares, Ricardo; Barriga, Gonzalo P.; Gaggero, Aldo; Martínez Valdebenito, Constanza; Le Corre Pérez, Monique Nicole; Ferrés, Marcela; Balcells Marty, María Elvira; Fernández, Jorge; Ramírez, Eugenio; Villarroel, Franz; Valiente Echeverría, Fernando; Soto Rifo, Ricardo
    Chile has one of the worst numbers worldwide in terms of SARS-CoV-2 positive cases and COVID-19-related deaths per million inhabitants; thus, characterization of neutralizing antibody (NAb) responses in the general population is critical to understanding of immunity at the local level. Given our inability to perform massive classical neutralization assays due to the scarce availability of BSL-3 facilities in the country, we developed and fully characterized an HIV-based SARS-CoV-2 pseudotype, which was used in a 96-well plate format to investigate NAb responses in samples from individuals exposed to SARS-CoV-2 or treated with convalescent plasma. We also identified samples with decreased or enhanced neutralization activity against the D614G spike variant compared with the wild type, indicating the relevance of this variant in host immunity. The data presented here represent the first insights into NAb responses in individuals from Chile, serving as a guide for future studies in the country.
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    Modelo computacional interactivo, semi-automatizado y de código abierto aplicado a la vigilancia de virus respiratorios
    (2020) Reyes Zaldivar, Felipe Tomás; Ferrés, Marcela; Vial, P.; Vollrath, V.; Camponovo, R.; Montecinos, L.; Hirsch Birn, Tamara; Valenzuela, P.; Perret Pérez, Cecilia
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    Mother-to-child transmission of Andes virus through breast milk, Chile
    (2020) Ferrés, Marcela; Martínez Valdebenito, Constanza; Angulo, J.; Henríquez, C.; Vera Otarola, Jorge Andrés; Vergara, M. J.; Vial Cox, María Cecilia; Vial Claro, Pablo; Pérez, J.; Le Corre Pérez, Monique Nicole; Fernández, J.; Sotomayor, V.; Valdés, M. F.; González-Candia, D.; Tischler, N. D.; Mertz, G.
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    SARS-CoV-2 vaccine booster in solid organ transplant recipients previously immunised with inactivated versus mRNA vaccines: A prospective cohort study
    (2022) Dib Marambio, Martín Javier; Le Corre Pérez, Monique Nicole; Ortiz Koh, Catalina Alejandra; García, Daniel; Ferrés, Marcela; Martínez Valdebenito, Constanza; Ruiz-Tagle, Cinthya; Ojeda Valenzuela, María José; Espinoza Sepúlveda, Manuel Antonio; Jara Contreras, Aquiles; Arab Verdugo, Juan Pablo; Rabagliati B., Ricardo; Vizcaya Altamirano, Cecilia; Ceballos, María Elena; Sarmiento Maldonado, Mauricio; Mondaca Contreras, Sebastián Patricio; Viñuela Morales, Macarena Rocío; Pastore Thomson, Antonia; Szwarcfiter Neiman, Vania; Galdames Lavín, Elizabeth Alejandra; Barrera Vásquez, Aldo Vincent; Castro Gálvez, Pablo Federico; Gálvez Arriagada, Nicolás Marcelo Salvador; Soto Ramírez, Jorge Andrés; Bueno Ramírez, Susan; Kalergis Parra, Alexis Mikes; Nervi Nattero, Bruno; Balcells Marty, María Elvira
    Solid-organ transplant (SOT) recipients have worse COVID-19 outcomes than general population and effective immunisation in these patients is essential but more difficult to reach. We aimed to determine the immunogenicity of an mRNA SARS-CoV-2 vaccine booster in SOT recipients previously immunised with either inactivated or homologous SARS-CoV-2 mRNA vaccine. Methods: Prospective cohort study of SOT recipients under medical care at Red de Salud UC-CHRISTUS, Chile, previously vaccinated with either CoronaVac or BNT162b2. All participants received a BNT162b2 vaccine booster. The primary study end point was anti-SARS-CoV-2 total IgG antibodies (TAb) seropositivity at 8-12 weeks (56-84 days) post booster. Secondary end points included neutralising antibodies (NAb) and specific T-cell responses. Findings: A total of 140 (50% kidney, 38% liver, 6% heart) SOT recipients (mean age 54 [13.6] years; 64 [46%] women) were included. Of them, 62 had homologous (three doses of BNT162b2) and 78 heterologous vaccine schedules (two doses of CoronaVac followed by BNT162b2 booster). Boosters were received at a median of 21.3 weeks after primary vaccination. The proportion achieving TAb seropositivity (82.3% vs 65.4%, P = 0.035) and NAb positivity (77.4% vs 55.1%, P = 0.007) were higher for the homologous versus the heterologous group. On the other hand, the number of IFN-γ and IL-2 secreting SARS-CoV-2-specific T-cells did not differ significantly between groups. Interpretation: This cohort study shows that homologous mRNA vaccine priming plus boosting in SOT recipients, reaches a significantly higher humoral immune response than inactivated SARS-CoV-2 vaccine priming followed by heterologous mRNA booster.
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    Symptom Profiles and Risk Factors for Hospitalization in Patients With SARS-CoV-2 and COVID-19 : A Large Cohort From South America
    (2020) Díaz Piga, Luis Antonio; García-Salum, T.; Fuentes López, Eduardo; Ferrés, Marcela; Medina, Rafael; Riquelme Pérez, Arnoldo
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    Varicella-Zoster Virus Meningitis and Encephalitis: An Understated Cause of Central Nervous System Infections
    (2020) Alvarez, J. C.; Alvarez Lavin, Jorge E.; Ticono, J.; Mellado T., Patricio; Miranda Vera, Héctor David; Ferrés, Marcela; Forero, J.; Alvarez, C.