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Aguilera, Ximena

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Aguilera

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Ximena

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End date: 2024 × Subject: SARS-CoV-2 ×

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    Seroprevalence and estimation of the impact of SARS-CoV-2 infection in older adults residing in Long-term Care Facilities in Chile
    (2022) Rubilar, Paola; Hirmas Adauy, Macarena; Matute, María Isabel; Browne, Jorge; Little, Cedric; Ruz, Gonzalo; Aguilera, Ximena; Avila, Carlos; Vial, Pablo; Gutknecht Mackenzie, Tania
    Introduction Older adults are at a higher risk of severe illness and death from COVID-19. This vulnera bility increases in those who live in long-term care facilities due to overcrowding, greater physical dependence, and contact with health workers. Evidence on the impact of the pan demic on these establishments in low- and middle-income countries has been scant. This study aims to determine the seroprevalence of SARS-CoV-2 in older people residing in long-term care facilities and estimate the impact of infection after the first wave of the pandemic. Methods A cross-sectional design with 2099 residents in three regions of Chile was carried out be tween September and November 2020. Measurement of antibodies was performed with a rapid test. The impact of SARS-CoV-2 infection was estimated with seropositive residents, those who had a history of positive polymerase chain reaction tests, and those who died from COVID-19. Bivariate analysis with the region, sex, age, history of COVID-19, physical dependence, and serological results were performed. In addition, we performed a correla tion analysis between the seroprevalence of the centers by the municipality and the rate of confirmed cases. Results The seroprevalence of SARS-CoV-2 antibodies in the three regions was 14.7% (95% confi dence interval: 13.2 to 16.3%), the infection impact was 46.4%, and the fatality rate was 19.6%. A significant correlation was found between the seroprevalence of older adults re siding in long-term care facilities and the cumulative incidence by municipalities. Conclusions The seroprevalence of older adults residing in long-term care facilities was higher than the general population. The high impact of infection among this population at the end of the first wave of the COVID-19 pandemic is similar to other countries. The centers' environ ment is directly related to COVID-19 infection. Morbidity and mortality monitoring sys tems should be implemented promptly to establish prevention and control measur
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    SARS-CoV-2 infectivity and antigenic evasion: spotlight on isolated Omicron sub-lineages
    (2024) Barrera, Aldo; Martínez, Constanza; Angulo, Jenniffer; Palma, Carlos; Hormazabal, Juan; Vial Cox, María Cecilia; Aguilera, Ximena; Castillo, Pablo; Pardo, Catalina; Balcells, María; Nervi, Bruno; Le Corre, Nicole; Ferrés, Marcela
    Since 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.

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