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Background: Acute myocardial infarction (AMI) results from obstruction of a coronary artery and affects around 126 million individuals globally. We have shown in a small pilot study that intracardiac delivery of autologous CD34+ cells after myocardial infarction is safe and leads to long term improvement. The improvement was such that three patients initially recommended for early heart transplantation in this study, no longer required it years after the cell injection. After the successful results of this pilot study, we started a multicenter, randomized, controlled Phase I/IIb study in post-AMI to investigate the safety and efficacy of intramyocardial injection of expanded autologous CD34+ cells (ProtheraCytes®) (NCT02669810). While patient recruitment is ongoing, we have developed a potency assay for the batch release of ProtheraCytes®. Methods: The proposed mechanisms of action by which ProtheraCytes® promote cardiac regeneration and revascularisation of damaged myocardial tissue is via the secretion of angiogenic factors and endothelial differentiation. We conducted a series of in vitro studies characterizing the growth factor secretion, exosome secretion, gene expression, cell surface markers, differentiation potential, and angiogenic potential of ProtheraCytes® clinical batches to develop a potency assay. Results: Here we show that ProtheraCytes® secrete vascular endothelial growth factor (VEGF) and its concentration is significantly correlated with the number of CD34+ cells obtained after expansion (Pearson r = 0.7484; p-value = 0.0009). ProtheraCytes® also secrete exosomes containing proangiogenic miRNAs (126, 130a, 378, 26a), antiapoptotic miRNAs (21 and 146a), antifibrotic miRNAs (133a, 24, 29b, 132), and miRNAs promoting myocardial regeneration (199a and 590). We also show that ProtheraCytes® have in vitro angiogenic activity, express surface markers of endothelial and cardiomyocyte progenitor cells, and can differentiate in vitro into endothelial cells. Conclusions: The potency assay should represent the product's mechanism of action, quantitatively measure the relevant biological product attribute, and have lot to lot consistency. Developing a potency assay is a required step before commencing the pivotal Phase 3 clinical studies. After the in vitro characterization of multiple ProtheraCytes® clinical batches, we established that measuring the concentration of VEGF provided the most practical, reliable, and consistent potency assay.

The recent Zika virus (ZIKV) epidemic has highlighted the poor knowledge on its physiopathology. Recent studies showed that ZIKV of the Asian lineage, responsible for this international outbreak, causes neuropathology in vitro and in vivo. However, two African lineages exist and the virus is currently found circulating in Africa. The original African strain was also suggested to be neurovirulent but its laboratory usage has been criticized due to its multiple passages. In this study, we compared the French Polynesian (Asian) ZIKV strain to an African strain isolated in Central African Republic and show a difference in infectivity and cellular response between both strains in human neural stem cells and astrocytes. Consistently, this African strain led to a higher infection rate and viral production, as well as stronger cell death and anti-viral response. Our results highlight the need to better characterize the physiopathology and predict neurological impairment associated with African ZIKV., Highlights • ZIKV from two Asian and African strains infect differentially IPSc-derived NSCs • African ZIKV strain displays more infectivity and anti-viral response • African and Asian ZIKV strains infect and replicate efficiently in human astrocytes Zika virus (ZIKV) is involved in a major epidemic in Latin America. Some neurological complications are reported following infection, in particular microcephaly and Guillain-Barré syndromes. Analyses show that one Asian and two Africans lineages exist. Although originally discovered in Africa in 1947, the actual epidemic is due to Asian ZIKV. Here, we compared the virulence of two African and Asian ZIKV strains in neural cells. We showed that in human neural stem cells, African ZIKV strain had a higher infectivity and triggered stronger cellular response. Altogether, our results highlight the need to better characterize ZIKV lineages to anticipate further epidemics.