Mendes, M. | bioRxiv Science

bioRxiv2021

Library-based analysis reveals segment and length dependent characteristics of defective influenza genomes

Parasitic elements of the viral population which are unable to replicate on their own yet rise to high frequencies, defective interfering particles are found in a variety of different viruses. Their presence is associated with a loss of population fitness, both through the depletion of key cellular resources and the stimulation of innate immunity. For influenza A virus, these particles contain large internal deletions in the genomic segments which encode components of the heterotrimeric polymerase. Using a library-based approach, we comprehensively profile the growth and replication of defective influenza species, demonstrating that they possess an advantage during genome replication, and that exclusion during packaging reshapes population composition in a manner consistent with their final, observed, distribution in natural populations. We find that an innate immune response is not linked to the size of a deletion; however, replication of defective segments can enhance their immunostimulatory properties. Overall, our results address several key questions in defective influenza A virus biology, and the methods we have developed to answer those questions may be broadly applied to other defective viruses.

microbiology↗

bioRxiv2021

Oligomeric α-Synuclein induces skin degeneration in a reconstructed human epidermis model

Cell senescence may promote epidermal inflammation and degeneration, termed as inflammaging, which is accompanied by keratinocyte loss, resulting in fine lines of wrinkles. Recent findings showed that healthy elderly skin expresses age- and neuron-related amyloidogenic proteins, such as tau, {beta}-Amyloid34, and -synuclein (-Syn), typically found in patients with neurodegenerative diseases. These proteins form toxic aggregates that trigger inflammatory signals. Herein, we investigated the impact of oligomeric -Syn (O-Syn) on the neurosphere (NP) and the reconstructed human epidermis (RHE) 3D models. First, we found the expression of -Syn, {beta}-Amyloid, and amyloid precursor protein (APP) in the RHE. Second, we challenged the RHE and NP with O-Syn, which decreased RHE regeneration, measured by the percentage of cell proliferation and thickness of the stratum basale, but did not affect NP neurite outgrowth. O-Syn did not decrease the number of human neonatal epidermal keratinocytes (HEKn) but, as seen for the RHE, it also decreased the proliferation of HEKn. We confirmed that the oligomeric, and not the monomeric -Syn species, accounted for the proliferation-decreasing effect. O-Syn also increased the NF-kB nuclear translocation in HEKn analyzed by nucleus/cytoplasm NF-{kappa}B fluorescence intensity. In addition, O-Syn triggered inflammation in the RHE, by increasing the mRNA levels of IL-1{beta} and tumor necrosis factor-alpha (TNF-), and the release of TNF- in a time-dependent manner. These findings show that O-Syn does not affect neurite outgrowth but induces a decrease in keratinocyte proliferation along with epidermal inflammation. With our tridimensional models, we demonstrated that the neurodegenerative protein O-Syn also degenerates the epidermis, drawing attention to the need of target-based screening to prevent and treat the effects of skin aging.

neuroscience↗