Genomic Evidence of SARS-CoV-2 Reinfection Involving E484K Spike Mutation, Brazil.

Uncertainty remains about how long the protective immune responses against severe acute respiratory syndrome coronavirus 2 persists, and suspected reinfection in recovered patients has been reported. We describe a case of reinfection from distinct virus lineages in Brazil harboring the E484K mutation, a variant associated with escape from neutralizing antibodies.

Betulinic Acid Exerts Cytoprotective Activity on Zika Virus-Infected Neural Progenitor Cells.

Zika virus (ZIKV), a member of the Flaviviridae family, was brought into the spotlight due to its widespread and increased pathogenicity, including Guillain-Barré syndrome and microcephaly. Neural progenitor cells (NPCs), which are multipotent cells capable of differentiating into the major neural phenotypes, are very susceptible to ZIKV infection. Given the complications of ZIKV infection and potential harm to public health, effective treatment options are urgently needed. Betulinic acid (BA), an abundant terpenoid of the lupane group, displays several biological activities, including neuroprotective effects. Here we demonstrate that Sox2+ NPCs, which are highly susceptible to ZIKV when compared to their neuronal counterparts, are protected against ZIKV-induced cell death when treated with BA. Similarly, the population of Sox2+ and Casp3+ NPCs found in ZIKV-infected cerebral organoids was significantly higher in the presence of BA than in untreated controls. Moreover, well-preserved structures were found in BA-treated organoids in contrast to ZIKV-infected controls. Bioinformatics analysis indicated Akt pathway activation by BA treatment. This was confirmed by phosphorylated Akt analysis, both in BA-treated NPCs and brain organoids, as shown by immunoblotting and immunofluorescence analyses, respectively. Taken together, these data suggest a neuroprotective role of BA in ZIKV-infected NPCs.

Generation and characterization of transgenic mouse mesenchymal stem cell lines expressing hIGF-1 or hG-CSF.

Mesenchymal stem cells (MSC) are promising tools in the fields of cell therapy and regenerative medicine. In addition to their differentiation potential, MSC have the ability to secrete bioactive molecules that stimulate tissue regeneration. Thus, the overexpression of cytokines and growth factors may enhance the therapeutic effects of MSC. Here we generated and characterized mouse bone marrow MSC lines overexpressing hG-CSF or hIGF-1. MSC lines overexpressing hG-CSF or hIGF-1 were generated through lentiviral vector mediated gene transfer. The expression of hG-CSF or hIGF-1 genes in the clones produced was quantified by qRT-PCR, and the proteins were detected in the cell supernatants by ELISA. The cell lines displayed cell surface markers and differentiation potential into adipocytes, osteocytes and chondrocytes similar to the control MSC cell lines, indicating the conservation of their phenotype even after genetic modification. IGF-1 and G-CSF transgenic cells maintained immunosuppressive activity. Finally, we performed a comparative gene expression analysis by qRT-PCR array in the cell lines expressing hIGF-1 and hG-CSF when compared to the control cells. Our results demonstrate that the cell lines generated may be useful tools for cell therapy and are suitable for testing in disease models.

Granulocyte-Colony Stimulating Factor-Overexpressing Mesenchymal Stem Cells Exhibit Enhanced Immunomodulatory Actions Through the Recruitment of Suppressor Cells in Experimental Chagas Disease Cardiomyopathy.

Genetic modification of mesenchymal stem cells (MSCs) is a promising strategy to improve their therapeutic effects. Granulocyte-colony stimulating factor (G-CSF) is a growth factor widely used in the clinical practice with known regenerative and immunomodulatory actions, including the mobilization of regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs). Here we evaluated the therapeutic potential of MSCs overexpressing G-CSF (MSC_G-CSF) in a model of inflammatory cardiomyopathy due to chronic Chagas disease. C57BL/6 mice were treated with wild-type MSCs, MSC_G-CSF, or vehicle (saline) 6 months after infection with Trypanosoma cruzi. Transplantation of MSC_G-CSF caused an increase in the number of circulating leukocytes compared to wild-type MSCs. Moreover, G-CSF overexpression caused an increase in migration capacity of MSCs to the hearts of infected mice. Transplantation of either MSCs or MSC_G-CSF improved exercise capacity, when compared to saline-treated chagasic mice. MSC_G-CSF mice, however, were more potent than MSCs in reducing the number of infiltrating leukocytes and fibrosis in the heart. Similarly, MSC_G-CSF-treated mice presented significantly lower levels of inflammatory mediators, such as IFNγ, TNFα, and Tbet, with increased IL-10 production. A marked increase in the percentage of Tregs and MDSCs in the hearts of infected mice was seen after administration of MSC_G-CSF, but not MSCs. Moreover, Tregs were positive for IL-10 in the hearts of T. cruzi-infected mice. In vitro analysis showed that recombinant hG-CSF and conditioned medium of MSC_G-CSF, but not wild-type MSCs, induce chemoattraction of MDSCs in a transwell assay. Finally, MDSCs purified from hearts of MSC_G-CSF transplanted mice inhibited the proliferation of activated splenocytes in a co-culture assay. Our results demonstrate that G-CSF overexpression by MSCs potentiates their immunomodulatory effects in our model of Chagas disease and suggest that mobilization of suppressor cell populations such as Tregs and MDSCs as a promising strategy for the treatment of chronic Chagas disease. Finally, our results reinforce the therapeutic potential of genetic modification of MSCs, aiming at increasing their paracrine actions.

Zika virus infection induces mitosis abnormalities and apoptotic cell death of human neural progenitor cells.

Zika virus (ZIKV) infection has been associated with severe complications both in the developing and adult nervous system. To investigate the deleterious effects of ZIKV infection, we used human neural progenitor cells (NPC), derived from induced pluripotent stem cells (iPSC). We found that NPC are highly susceptible to ZIKV and the infection results in cell death. ZIKV infection led to a marked reduction in cell proliferation, ultrastructural alterations and induction of autophagy. Induction of apoptosis of Sox2+ cells was demonstrated by activation of caspases 3/7, 8 and 9, and by ultrastructural and flow cytometry analyses. ZIKV-induced death of Sox2+ cells was prevented by incubation with the pan-caspase inhibitor, Z-VAD-FMK. By confocal microscopy analysis we found an increased number of cells with supernumerary centrosomes. Live imaging showed a significant increase in mitosis abnormalities, including multipolar spindle, chromosome laggards, micronuclei and death of progeny after cell division. FISH analysis for chromosomes 12 and 17 showed increased frequency of aneuploidy, such as monosomy, trisomy and polyploidy. Our study reinforces the link between ZIKV and abnormalities in the developing human brain, including microcephaly.