A year of genomic surveillance reveals how the SARS-CoV-2 pandemic unfolded in Africa.

The progression of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic in Africa has so far been heterogeneous, and the full impact is not yet well understood. In this study, we describe the genomic epidemiology using a dataset of 8746 genomes from 33 African countries and two overseas territories. We show that the epidemics in most countries were initiated by importations predominantly from Europe, which diminished after the early introduction of international travel restrictions. As the pandemic progressed, ongoing transmission in many countries and increasing mobility led to the emergence and spread within the continent of many variants of concern and interest, such as B.1.351, B.1.525, A.23.1, and C.1.1. Although distorted by low sampling numbers and blind spots, the findings highlight that Africa must not be left behind in the global pandemic response, otherwise it could become a source for new variants

Pre-clinical in vivo evaluation of cormatrix as right-sided valved conduit

Introduction: Although not FDA approved for heart valve repair, decellularized porcine small intestinal submucosa (Cormatrix) is currently used in quite a lot of institutes to reconstruct heart valves in patients. Recently, surgeons experienced clinical failures using Cormatrix as a patch in heart valve repair and words of caution were raised. The aim of this study was to pre-clinically evaluate CorMatrix as right-sided heart valved conduit in a xenogeneic animal model Methods: CorMatrix was used as valved conduit in the right ventricular outflow tract in sheep (n=10) and lambs (n=10). Valved conduits were home-made and explanted after 1 month, 3 months or 6 months. Valve function was assessed by echocardiography directly after implantation and prior to termination. Explants were analyzed using histology, scanning electron microscopy, mechanical testing, biochemical analysis and immunohistochemistry Results: All valved conduits were successfully implanted. 5 sheep and 2 lambs did not survive until planned follow-up. Diseased animals died due to valve failure after 1 or 2 months. Valve leaflets where thickened with signs of a massive inflammatory response. 5 sheep (1 month n=3, 3 months n=1 and 6 months n=1) and 8 lambs (1 month n=3, 3 months n=3, 6 months n=2) survived until planned follow up. In these animals, on echocardiography a well functioning valve with no signs of stenosis or insufficiency was seen. However all explants showed only limited signs of cellular infiltration or neotissue formation Conclusions: In the chronic sheep and lamb model, 13 out of 20 CorMatrix pulmonary valved conduits were intact and showed good functionality, although only limited signs of tissue remodeling. However, 7 out of 20 valves failed owing to a massive inflammatory response. Further analysis is needed to understand the disturbing dichotomous outcome before clinical application can be advised

Failure of decellularized porcine small intestinal submucosa as a heart valved conduit

Objective: Decellularized extracellular matrix made from porcine small intestinal submucosa, commercially available as CorMatrix (CorMatrix Cardiovascular, Inc, Roswell, Ga) is used off-label to reconstruct heart valves. Recently, surgeons experienced failures and words of caution were raised. The aim of this study was to evaluate decellularized porcine small intestinal submucosa as right-sided heart valved conduit in a xenogeneic animal model. Methods: A pulmonary valve replacement was performed with custom-made valved conduits in 10 lambs and 10 sheep (1 month [3 lambs and 3 sheep], 3 months [3 lambs and 3 sheep], 6 months [4 lambs and 4 sheep]). Valve function was assessed after implantation and before the animal was put to death. Explanted conduits were inspected macroscopically and analyzed using immunohistochemistry and scanning electron microscopy. They also underwent mechanical testing and testing for biochemical composition. Results: All valved conduits were successfully implanted. Five sheep and 2 lambs died due to congestive heart failure within 2 months after surgery. In the animals that died, the valve leaflets were thickened with signs of inflammation (endocarditis in 4). Five sheep and 8 lambs (1 month: 6 out of 6 animals, 3 months: 4 out of 6 animals, 6 months: 3 out of 8 animals) survived planned follow-up. At the time they were put to death, 5 lambs had significant pulmonary stenosis and 1 sheep showed severe regurgitation. A well-functioning valve was seen in 4 sheep and 3 lambs for up to 3 months. These leaflets showed limited signs of remodeling. Conclusions: Fifty percent of sheep and 20% of lambs died due to valve failure before the planned follow-up period was complete. A well-functioning valve was seen in 35% of animals, albeit with limited signs of tissue remodeling at ≤3 months after implantation. Further analysis is needed to understand the disturbing dichotomous outcome before clinical application can be advised