The Crown's Secrets: A novel analysis of coronavirus adaptation and evolution

Viruses, like all organisms (not saying viruses are organisms), must be able to adapt to the pressures of their host environment and the environments which encompass their hosts. Furthermore, over time, they must be able to evolve to match or outcompete the harsh conditions and defensive role that compose a host's immune system; without this adaptation and evolution, a viral species would likely reach its end, its maker, in the traps of immune responses. Relatedly, some of the most common viruses are those that cause common colds; coronaviruses fall into exactly this category. Likewise, they must have some distinct methods of viral adaptation and evolution. It's exactly this question that drove researchers Pierre Talbot and Marc Desforges to investigate just how these viruses manage to repeatedly infect and temporarily defeat host immune systems.

Coronaviruses are known for their crown of spikes, which are both aesthetically pleasing and physiologically functional. It's been known for sometime that these are crucial to viral identification of and by cells as these are the first proteins any cellular receptor would recognize. Likewise, they determine tissue, cellular, and host tropisms. These researchers have also discovered that the modulation and adaptations of these same spikes seems to be what allows coronaviruses to be as various and effective as they are.

Apparently (or at least in HCoV229E, the pertinent virus of this study) Coronaviruses' spikes have three long loops at their ends that make up three regions of the receptor binding domains (RBD). RBDs are the tropogens (i.e. the parts of the virus that are recognized by a cellular receptor/protein for entry). Using HCoV229E's RBD and its receptor, aminopeptidase N, the team crystallized the attached complex and found that the virus was able to vary each region, each loop separately, vastly enlarging its diversity as a species. This allows for a method to modulate how strongly viruses attach to cells (affinity) and which cells are most susceptible to infection. Indeed, it appears that these three loops are the only things that vary from strain to strain. On top of that, these viruses are also capable of masking and unmasking their RBDs until they're completely ready to infect cells, preventing their recognition by the immune system.

Thus, the common cold is quite diverse both in the viral species that cause it and how these species specifically function to overcome your immune system, which has probably encountered them before!

Well, I'm Corona-gone-ya!

-javarcia ivory

https://www.sciencedaily.com/releases/2017/11/171127105937.htm