The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Estudios de biocompatibilidad y resistencia a la corrosión de recubrimientos de hidroxiapatita sobre aleaciones de Ti6Al4V

Universidad de Sevilla: Escuela Politécnica Superior VII Jornada de Investigación Desarrollo e Innovación de la Escuela Politécnica Superior de la Universidad de SevillaEl objetivo de este trabajo ha sido desarrollar recubrimientos orgánicos-inorgánicos modificados con dispersiones de partículas de hidroxiapatita (HAp) para mejorar la biocompatibilidad y la respuesta de osteoblastos humanos normales (NHOst) en términos de viabilidad y de adhesión sobre una aleación Ti6Al4V. Los recubrimientos híbridos se han obtenido por vía sol-gel a partir de mezclas de tetrametilortosilicato y ¿-metacriloxipropiltrimetoxisilano. Las partículas de HAp se han obtenido también por vía sol-gel mediante hidrólisis y condensación de una mezcla de trietilfosfito y nitrato de calcio tetrahidratado en cantidades estequiométricas, con una relación Ca/P de 1,67. Para la sinterización de los polvos de HAp, se han aplicado tratamiento térmicos convencionales y una modificación de la técnica de análisis térmico a velocidad controlada (CRTA), que ha mostrado ser una alternativa viable para la producción de películas delgadas de hidroxiapatita sintética con superficie específica controlada y distribución homogénea de poros. Se ha demostrado que la incorporación de partículas de HAp en la red híbrida mejora la adsorción de fibrinógeno y la protección frente a la corrosión de la aleación Ti6Al4V, probablemente debido a un aumento del grado de reticulación de la matriz órgano-polisiloxánica y del espesor del recubrimiento

Selective Crystal Growth Regulation by Chiral �-Hydroxycarboxylic Acids Improves the Strength and Toughness of Calcium Sulfate Cements

Natural biominerals, such as bones and teeth, use acidic matrix biomolecules to control growth, morphology, and organization of the brittle hydroxyapatite crystals. This interplay provides biominerals with outstanding mechanical properties. Recently, we reported that the l-enantiomer of chiral tartaric acid has a potent regulatory effect on the crystal structure and mechanical performance of brushite cement, a mineral with a monoclinic crystal system. We hypothesized that this strategy could be applied using various chiral �-hydroxycarboxylic acids to enhance the mechanical performance of calcium sulfate dihydrate cements, another mineral belonging to the monoclinic crystal system. Calcium sulfate cements are widely used in dentistry, medicine, and construction, but these cements have low mechanical properties. In this work, we first determined the impact of different chiral �-hydroxycarboxylic acids on the properties of calcium sulfate cements. After that, we focused on identifying the regulation effect of chiral tartaric acid on gypsum crystals precipitated in a supersaturated solution. Here, we show that the selective effect of �-hydroxycarboxylic acid l-enantiomers on calcium sulfate crystals improved the mechanical performance of gypsum cements, while d-enantiomer had a weak impact. Compare to the calcium sulfate cements prepared without additives, the presence of l-enantiomer enhanced the compressive strength and the fracture toughness of gypsum cements by 40 and 70%, respectively. Thus, these results prove the generalizability of this approach and help us to fabricate high-strength cements.Scopu

Recubrimientos bioactivos de base hidroxiapatita sobre titanio y sus aleaciones para aplicaciones biomédicas

Premios de la Academia de Ciencias de Cuba 2018 Las soluciones que la medicina moderna brinda ante las enfermedades óseas han propiciado que las ciencias contemporáneas dediquen cada vez más esfuerzos al desarrollo de biomateriales que mejoraren la capacidad funcional del individuo y su calidad de vida. Uno de los puntos críticos que se requiere superar es conseguir la fijación satisfactoria entre implante y tejido óseo. Sobre esta base, el objetivo del trabajo consistió en el desarrollo de una tecnología novedosa para obtener recubrimientos cerámicos de hidroxiapatita sobre titanio (Ti) y su aleación Ti6Al4V, utilizada en cirugía osteoarticular, combinando el método de sol-gel con una cristalización por tratamiento térmico a presión reducida, a bajas temperaturas. Los resultados del trabajo demostraron que con estos métodos se obtienen recubrimientos uniformes de hidroxiapatita con características texturales de porosidad controlada, mejor adherencia y efecto protector al fenómeno de la corrosión, propiedades requeridas para su uso en implantes óseos. Además, los ensayos de citocompatibilidad in vitro demostraron que los materiales obtenidos no son citotóxicos. Por otra parte, la obtención de piezas de titanio poroso recubiertas con hidroxiapatita, garantiza el equilibrio biomecánico y biofuncional, así como la obtención de la porosidad de tamaño adecuado (¿100 ¿m, 40-50 %vol) de tipo interconectada, permitirá el crecimiento del hueso hacia el interior del implante y el transporte del fluido fisiológico. Sobre la base de los resultados de caracterización químico-física, la morfología, la adherencia y la impedancia de los sistemas obtenidos, los recubrimientos de hidroxiapatita, además de sus propiedades de biocompabilidad, sirven como capa protectora al fenómeno de la corrosión haciendo promisorio el sistema para posibles aplicaciones biomédicas como prótesis ortopédicas

Biomimetic trace metals improve bone regenerative properties of calcium phosphate bioceramics

The bone regenerative capacity of synthetic calcium phosphates (CaPs) can be enhanced through the enrichment with selected metal trace ions. However, defining the optimal elemental composition required for bone formation is challenging due to many possible concentrations and combinations of these elements. We hypothesized that the ideal elemental composition exists in the inorganic phase of the bone extracellular matrix (ECM). To study our hypothesis, we first obtained natural hydroxyapatite through the calcination of bovine bone, which was then investigated its reactivity with acidic phosphates to produce CaP cements. Bioceramic scaffolds fabricated using these cements were assessed for their composition, properties, and in vivo regenerative performance and compared with controls. We found that natural hydroxyapatite could react with phosphoric acid to produce CaP cements with biomimetic trace metals. These cements present significantly superior in vivo bone regenerative performance compared with cements prepared using synthetic apatite. In summary, this study opens new avenues for further advancements in the field of CaP bone biomaterials by introducing a simple approach to develop biomimetic CaPs. This work also sheds light on the role of the inorganic phase of bone and its composition in defining the regenerative properties of natural bone xenografts.Scopu