Browsing by Author "Valiente Echeverria, Fernando"
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- ItemA cis-Acting Element Present within the gag Open Reading Frame Negatively Impacts on the Activity of the HIV-1 IRES(2013) Valiente Echeverria, Fernando; Vallejos, Maricarmen; Monette, Anne; Pino, Karla; Letelier, Alejandro; Huidobro Toro, J. Pablo; Mouland, Andrew J.; López Lastra, Marcelo Andrés
- ItemActivity of the human immunodeficiency virus type 1 cell cycle-dependent internal ribosomal entry site is modulated by IRES trans-acting factors(OXFORD UNIV PRESS, 2011) Vallejos, Maricarmen; Deforges, Jules; Plank, Terra Dawn M.; Letelier, Alejandro; Ramdohr, Pablo; Abraham, Christopher G.; Valiente Echeverria, Fernando; Kieft, Jeffrey S.; Sargueil, Bruno; Lopez Lastra, MarceloThe 5' leader of the human immunodeficiency virus type 1 (HIV-1) genomic RNA harbors an internal ribosome entry site (IRES) that is functional during the G2/M phase of the cell cycle. Here we show that translation initiation mediated by the HIV-1 IRES requires the participation of trans-acting cellular factors other than the canonical translational machinery. We used 'standard' chemical and enzymatic probes and an 'RNA SHAPE' analysis to model the structure of the HIV-1 5' leader and we show, by means of a footprinting assay, that G2/M extracts provide protections to regions previously identified as crucial for HIV-1 IRES activity. We also assessed the impact of mutations on IRES function. Strikingly, mutations did not significantly affect IRES activity suggesting that the requirement for pre-formed stable secondary or tertiary structure within the HIV-1 IRES may not be as strict as has been described for other viral IRESes. Finally, we used a proteomic approach to identify cellular proteins within the G2/M extracts that interact with the HIV-1 5' leader. Together, data show that HIV-1 IRES-mediated translation initiation is modulated by cellular proteins.
- ItemAnaplasma platys in dogs, Chile(CENTER DISEASE CONTROL, 2007) Abarca, Katia; Lopez, Javier; Perret, Cecilia; Guerrero, Javier; Godoy, Paula; Veloz, Ana; Valiente Echeverria, Fernando; Leon, Ursula; Gutjahr, Constanza; Azocar, TeresaWe conducted a 16S rRNA nested PCR for the genus Ehrlichia and Ehrlichia spp. with blood samples from 30 ill dogs in Chile. Phylogenetic analysis was performed by using groESL gene amplification. We identified Anaplasma platys as 1 of the etiologic agents of canine ehrlichiosis.
- ItemImmune responses during COVID-19 breakthrough cases in vaccinated children and adolescents(Frontiers Media SA, 2024) Rivera Pérez, Daniela; Méndez Vejar, Constanza Soledad; Diethelm Varela, Benjamín Manuel; Melo González, Felipe Andrés; Vázquez Hernández, Yaneisi; Meng, Xing; Xin, Qianqian; Fasce, Rodrigo A.; Fernández, Jorge; Mora, Judith; Ramírez, Eugenio; Acevedo, Mónica L.; Valiente Echeverria, Fernando; Soto Rifo, Ricardo; Grifoni, Alba; Weiskopf, Daniela; Sette, Alessandro; Astudillo Paredes, Patricio Andrés; Le Corre Pérez, Monique Nicole; Abarca Villaseca, Katia; Perret Pérez, Cecilia; González Muñoz, Pablo Alberto; Soto Ramírez, Jorge Andrés; Bueno Ramírez, Susan; Kalergis, Alexis M.Background: Vaccine effectiveness against SARS-CoV-2 infection has been somewhat limited due to the widespread dissemination of the Omicron variant, its subvariants, and the immune response dynamics of the naturally infected with the virus. Methods: Twelve subjects between 3-17 years old (yo), vaccinated with two doses of CoronaVac®, were followed and diagnosed as breakthrough cases starting 14 days after receiving the second dose. Total IgGs against different SARS-CoV-2 proteins and the neutralizing capacity of these antibodies after infection were measured in plasma. The activation of CD4+ and CD8+ T cells was evaluated in peripheral blood mononuclear cells stimulated with peptides derived from the proteins from the wild-type (WT) virus and Omicron subvariants by flow cytometry, as well as different cytokines secretion by a Multiplex assay. Results: 2 to 8 weeks post-infection, compared to 4 weeks after 2nd dose of vaccine, there was a 146.5-fold increase in neutralizing antibody titers against Omicron and a 38.7-fold increase against WT SARS-CoV-2. Subjects showed an increase in total IgG levels against the S1, N, M, and NSP8 proteins of the WT virus. Activated CD4+ T cells showed a significant increase in response to the BA.2 subvariant (p<0.001). Finally, the secretion of IL-2 and IFN-γ cytokines showed a discreet decrease trend after infection in some subjects. Conclusion: SARS-CoV-2 infection in the pediatric population vaccinated with an inactivated SARS-CoV-2 vaccine produced an increase in neutralizing antibodies against Omicron and increased specific IgG antibodies for different SARS-CoV-2 proteins. CD4+ T cell activation was also increased, suggesting a conserved cellular response against the Omicron subvariants, whereas Th1-type cytokine secretion tended to decrease. Clinical Trial Registration: clinicaltrials.gov #NCT04992260
- ItemMolecular identification of Ehrlichia canis in a dog from Arica, Chile(SOC CHILENA INFECTOLOGIA, 2012) Lopez, Javier; Abarca, Katia; Isabel Mundaca, M.; Caballero, Carla; Valiente Echeverria, FernandoWe report a molecular confirmed case of canine ehrlichiosis caused by Ehrlichia canis. A 10-year old female crossbred Siberian from the city of Arica, which was infested by ticks, presented hemorrhagic manifestations (hematomas and snout bleeding) and prostration. Blood cell count revealed thrombocytopenia (30,000 platelets/mm(3)). Immunochromatographic rapid testing for E. canis IgG was positive. Amplification and sequencing of a fragment of the 16S rRNA gen from a blood sample showed 100% homology with E. can is from Peril. This is the first report of E. canis in Chile, an agent with known zoonotic potential.
- ItemMorphological and molecular identification of canine filariae in a semi-rural district of the Metropolitan Region in Chile(SOC CHILENA INFECTOLOGIA, 2012) Lopez, Javier; Valiente Echeverria, Fernando; Carrasco, Marcela; Mercado, Ruben; Abarca, KatiaIntroduction: To date, there has been no definitive confirmation of the presence of zoonotic dirofilariasis in dogs in Chile. Objectives: To study the presence of dirofilarias in blood samples from dogs collected in a semi-rural district near Santiago and to compare their frequency in dogs with and without dermatological manifestations. Methods: We examined 100 blood samples for dog filariae infections using microscopic methods (modified Knott technique). 50 dogs presented dermatological symptoms or signs compatible with filarial infections and 50 were asymptomatic. ITS-2 and 12s rDNA gene amplification by PCR and sequencing were performed in samples microscopically positive for microfilariae. Results. We observed microfilariae in 22 dogs (22%). Of these, 16/50 (32%) were symptomatic and 6/50 (12%) were asymptomatic (p = 0.02). Morphologically, the majority of microfilariae were similar to Dirofilaria repens, although many had a bigger size than previously described. Nucleotide sequencing of the amplified genes showed no more than 95% homology with the D. repens sequences available for comparison. D. reconditum and D. dracunculoides infections were also identified. Conclusions: These features might indicate the presence of new species of Dirofilaria or a D. repens close related variant in Chile.
- ItemThe 5'-untranslated region of the mouse mammary tumor virus mRNA exhibits cap-independent translation initiation(OXFORD UNIV PRESS, 2010) Vallejos, Maricarmen; Ramdohr, Pablo; Valiente Echeverria, Fernando; Tapia, Karla; Rodriguez, Felipe E.; Lowy, Fernando; Pablo Huidobro Toro, J.; Dangerfield, John A.; Lopez Lastra, MarceloIn this study, we demonstrate the identification of an internal ribosome entry site (IRES) within the 5'-untranslated region (5'-UTR) of the mouse mammary tumor virus (MMTV). The 5'-UTR of the full-length mRNA derived from the infectious, complete MMTV genome was cloned into a dual luciferase reporter construct containing an upstream Renilla luciferase gene (RLuc) and a downstream firefly luciferase gene (FLuc). In rabbit reticulocyte lysate, the MMTV 5'-UTR was capable of driving translation of the second cistron. In vitro translational activity from the MMTV 5'-UTR was resistant to the addition of m(7)GpppG cap-analog and cleavage of eIF4G by foot-and-mouth disease virus (FMDV) L-protease. IRES activity was also demonstrated in the Xenopus laevis oocyte by micro-injection of capped and polyadenylated bicistronic RNAs harboring the MMTV-5'-UTR. Finally, transfection assays showed that the MMTV-IRES exhibits cell type-dependent translational activity, suggesting a requirement for as yet unidentified cellular factors for its optimal function.
- ItemThe Elav-like protein HuR exerts translational control of viral internal ribosome entry sites(ACADEMIC PRESS INC ELSEVIER SCIENCE, 2009) Rivas Aravena, Andrea; Ramdohr, Pablo; Vallejos, Maricarmen; Valiente Echeverria, Fernando; Dormoy Raclet, Virginie; Rodriguez, Felipe; Pino, Karla; Holzmann, Cristian; Huidobro Toro, J. Pablo; Gallouzi, Imed Eddine; Lopez Lastra, MarceloThe human embryonic-lethal abnormal vision (ELAV)-like protein. HuR, has been recently found to be involved in the regulation of protein synthesis. In this study we show that HuR participates in the translational control of the HIV-1 and HCV IRES elements. HuR functions as a repressor of HIV-1]RES activity and acts as an activator of the HCV]RES. The effect of HuR was evaluated in three independent experimental systems, rabbit reticulocyte lysate, HeLa cells, and Xenopus laevis oocytes, using both overexpression and knockdown approaches. Furthermore, results suggest that HuR mediated regulation of HIV-1 and HCV IRESes does not require direct binding of the protein to the RNA nor does it need the nuclear translocation of the IRES-containing RNAs. Finally, we show that HuR has a negative impact on post-integration steps of the HIV-1 replication cycle. Thus, our observations yield novel insights into the role of HuR in the post-transcriptional regulation of HCV and HIV-1 gene expression. (C) 2009 Elsevier Inc. All rights reserved.