Nonetheless, glycocalyx could be also involved in other membrane processes, which includes the absorption of some viruses [43]. In this regard, some viruses have evolved to exploit distinct glycans to enter cells, like human rotaviruses that bind the blood group A antigens [44]. Rather, within the case of HIV [45], Ebola virus [46], HCV [47], as well as influenza [48] or Severe Acute Respiratory NOD-like Receptor Proteins Biological Activity Syndrome (SARS) viruses [49], the viruses themselves present glycans on their surface. Their presence on viral surfaces is exploited by immune cells, for instance macrophages or dendritic cells, to phagocyte virions. In turn, Ebola [46] and SARS viruses [49] reap the benefits of this anti-viral program to enter and replicate in macrophages and dendritic cells. On the other hand, glycans are also used by viruses to create a shield that hides viral epitopes to immune cells, as happens with HIV, known to possess the highest density of glycans attached to its surface proteins [50], plus the Lassa virus [51]. The substantial overlap of your biogenesis processes gives a plausible explanation for the similar composition observed amongst EVs and enveloped viruses [39]. Furthermore, both EVs and enveloped viruses can bind to the plasma membrane of recipient cells and, after fusion events, straight with the surface membrane or immediately after endocytosis, they release their luminal cargo into the cytosol, influencing cell activity [18]. In this respect, in a comparable manner to the viral envelope proteins, EV surface proteins, such as the intercellular adhesion molecule 1 (ICAM-1), mediate the adhesion and internalization of EVs in target cells [52]. As a result, each EVs and viruses may be regarded as as bioactive Cathepsin X/Cathepsin Z Proteins Biological Activity structures capable to influence the cellular behavior. The presence of many similarities in between viruses (in distinct retroviruses) and EVs, straight away triggered conjecture on the true relationship involving vesicles and viruses. Because of this, two alternative theories have been proposed. The first one, known as the “Trojan exosome hypothesis”, states that retroviruses are vesicles evolved following a mutation in the gag gene, which was initially encoded by an integrated retro-transposon that directed its expression product towards the route of vesicle generation. Within this point of view, the standard qualities of retroviruses would have been acquired by evolutionary divergence; the pre-existing biogenesis mechanism of vesicle production would have been applied to kind viral particles [53]. The second theory will not associate viruses to modified exosomes. It justifies the similarities, giving more significance for the phenomenon of convergent evolution, which would lead to the sharing on the same biogenesis pathways for vesicles and viruses [54]. Each theories present a plausible justification for the affinities observed in between viruses and EVs. Nonetheless, no matter their achievable origin, these affinities undoubtedly have a negativeViruses 2020, 12,4 ofimpact on immunological surveillance in the host, considering the fact that viruses, during infections, can take advantage of these affinities for escaping the immune method by mimicking vesicle composition and behavior [55]. The outstanding resemblance among EVs and viruses has brought on pretty a few complications inside the studies focused on the evaluation of EVs released throughout viral infections. Today, it can be an pretty much impossible mission to separate EVs and viruses by implies of canonical vesicle isolation techniques, such as differential ultracentrifugation, due to the fact.
