About this Research Topic
One of the most important and outstanding characteristics of viruses is their cellular and host tropism. As parasitic entities, viruses have to compromise with numbers of positive and negative factors present in target cells for their survival. In the absence of an appropriate interaction with cells, they do not replicate at all. Viral tropism can be therefore determined at each replication step, from the entry to progeny production in target cells. There are two major types of viral tropism, that is, the receptor-dependent and -independent tropisms. Restriction of viral replication occurs on the cell surface (receptor-dependent viral entry step) and/or intracellularly (receptor-independent post-entry replication steps). Viruses have acquired some mechanisms through adaptive mutations and/or recombinations to counteract a wide variety of cellular restriction factors, or to correctly interact with numerous cellular factors necessary for replication. They thereby can replicate, spread and survive in certain cell lineages, tissues, organs and finally in host individuals. This evolutional process/pressure would have generated profound effects on the biological properties of viruses. Recently, many cellular anti-viral factors with unique action mechanisms in addition to co-viral factors have been discovered by extensive studies on molecular genetics of viruses. Researches of these factors would lead to the effective clinical applications, as well as the increase of basic biological knowledge.
In this Research Topic, we focus on the receptor-independent and uniquely associated viral tropism other than the strictly receptor-dependent or -mediated one. By presenting a series of centered articles, we describe here the unique properties of various virus species. Any types of the tier 1 article would be accepted and included in this Topic.
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