SARS CoV-2 bulaşma ve replikasyon dinamiği

Çin’de 2019 yılı sonunda ansızın pneumoni salgını ortaya çıkmışve bu salgına SARS-CoV-2 ismi verilen yeni bir coronavirus tipininsebep olduğu bildirilmiştir. Hızlı bir yayılım gösteren bu virus, halksağlığı açısından krize sebep olmuş ve Çin’in dışına çıkan enfektekişiler ile kısa sürede yayılarak pandemiye dönüşmüştür. Yarasalardan orijin alan bu yeni virusun insanlara bulaşmasında pangolinismi verilen ara konakçı memelinin rol oynadığı düşünülmektedir.Henüz tam aydınlığa kavuşturulamamış olsa da, betacoronaviruslariçin gen havuzu sağlayan yarasalardan pangoline aktarılan bu yenitip coronavirusun, pangolinde kısmi S geni mutasyonu ile insanlarıenfekte edebilir hale dönüştüğü şimdilik en geçerli hipotezler arasında yer almaktadır. İnsanların solunum sistemi epitel dokularındayer alan ACE2 reseptörüne SARS-CoV-2’nin S glikoproteini ile tutunması yoluyla epitop-paratop ilişkisi sağlanmaktadır. Hücre içinealınan SARS-CoV-2; transkripsiyon, translasyon ve replikasyondanoluşan yaşam siklusunu tamamlayarak yeni nesil enfektif virionları diğer duyarlı hücreleri enfekte etmek üzere hücre dışına aktarır.SARS-CoV-2’nin yaşam siklusunda önemli rol üstlenen viral proteinler; reseptöre bağlanma spesifitesi, proteolitik aktivasyonu, endositoz etkinliği ve konakçının doğal bağışıklık tepkisinin engellenmesifaaliyetlerini kusursuz bir şekilde yöneterek hastalığın patogenezinişekillendirmektedir. SARS-CoV-2’nin sebep olduğu COVID-19 enfeksiyonunu diğer coronavirus enfeksiyonlarından ayıran en önemlifaktörün, SARS-CoV-2’ye ait yapısal ve yapısal olmayan protein aktivitelerinden kaynaklandığı düşünülmektedir. Sonuç olarak, son yıllarda ortaya çıkan sırasıyla SARS-CoV, MERS-CoV ve SARS-CoV-2 gibizoonotik coronavirus türleri önemli bir halk sağlığı problemi oluşturmuştur. Coronaviruslarda gerçekleşen mutasyonlara bağlı olarakzaman içerisinde yeni tiplerin ortaya çıkması olasıdır. Bu sebeplecoronavirusların biyolojisi, patogenezi ve epidemiyolojisi üzerineyapılan detaylı ve sürekliliği olan çalışmalara ihtiyaç duyulmaktadır.

Transmission and replication dynamics of SARS CoV-2

At the end of 2019, there was a sudden outbreak of pneumonia in China, which was reported to be caused by the new type of coronavirus, called SARS-CoV-2. This rapidly spreading virus has caused a public health crisis, and turned into a pandemic in a short time through the infected people traveling outside of China. It is believed that bats, which are the reservoir of the new coronavirus and provides a gene pool for betacoronaviruses, transmitted the SARS-CoV-2 to an intermediate host called pangolin, which in turn transmitted it to humans. Although not fully clarified yet, it is currently the most valid hypothesis that pangolin provided a partial S gene mutation to new coronavirus which is transformed into the final SARS-CoV-2 form that can infect humans. The epitope-paratope interaction is achieved through the binding of S glycoprotein of SARS-CoV-2 to the ACE2 receptors in the epithelial tissues of the human respiratory system. Following its entry into cells, SARS-CoV-2 completes its life cycle consisting of transcription, translation and replication stages, and transfers the next generation of infective virions out of the cell to infect other susceptible cells. The viral proteins, which play an important role in the life cycle of SARS-CoV-2, manage the activities of receptor binding specificity, proteolytic activation, endocytosis activity and inhibition of the host's natural immune response, and shape the pathogenesis of the disease in this way. The most important factor that distinguishes COVID-19 infection caused by SARSCoV-2 from other coronavirus infections is believed to be due to the structural and non-structural protein activities of SARS-CoV-2. As a result, the zoonotic coronavirus species, such as SARS-CoV, MERSCoV, and SARS-CoV-2 that have emerged in recent years have caused a significant public health problem. Depending on the mutations in coronaviruses, new species are likely to emerge over time. Therefore, detailed and ongoing studies on the biology, pathogenesis and epidemiology of coronaviruses are needed.

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