Current approaches used in treating COVID-19 from a molecular mechanisms and immune response perspective

Coronavirus disease 2019 (COVID-19), which is caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was declared by the World Health Organization (WHO) as a global pandemic on March 11, 2020. SARS-CoV-2 targets the respiratory system, resulting in symptoms such as fever, headache, dry cough, dyspnea, and dizziness. These symptoms vary from person to person, ranging from mild to hypoxia with acute respiratory distress syndrome (ARDS) and sometimes death. Although not confirmed, phylogenetic analysis suggests that SARS-CoV-2 may have originated from bats; the intermediary facilitating its transfer from bats to humans is unknown. Owing to the rapid spread of infection and high number of deaths caused by SARS-CoV-2, most countries have enacted strict curfews and the practice of social distancing while awaiting the availability of effective U.S. Food and Drug Administration (FDA)-approved medications and/or vaccines. This review offers an overview of the various types of coronaviruses (CoVs), their targeted hosts and cellular receptors, a timeline of their emergence, and the roles of key elements of the immune system in fighting pathogen attacks, while focusing on SARS-CoV-2 and its genomic structure and pathogenesis. Furthermore, we review drugs targeting COVID-19 that are under investigation and in clinical trials, in addition to progress using mesenchymal stem cells to treat COVID-19. We conclude by reviewing the latest updates on COVID-19 vaccine development. Understanding the molecular mechanisms of how SARS-CoV-2 interacts with host cells and stimulates the immune response is extremely important, especially as scientists look for new strategies to guide their development of specific COVID-19 therapies and vaccines.

Attenuated live vaccine usage affects accurate measures of virus diversity and mutation rates in avian coronavirus infectious bronchitis virus

The full-length genomes of 11 infectious bronchitis virus (IBV) field isolates from three different types of the virus; Massachusetts (Mass), Connecticut (Conn) and California (CAL) isolated over a 41, 25 and 8 year period respectively, were sequenced and analyzed to determine the mutation rates and level of polymorphisms across the genome. Positive selection was not detected and mutation rates ranged from 10(-4) to 10(-6)substitutions/site/year for Mass and Conn IBV types where attenuated live vaccines are routinely used to control the disease. In contrast, for CAL type viruses, for which no vaccine exists, positive selection was detected and mutation rates were 10 fold higher ranging from 10(-2) to 10(-3)substitutions/site/year. Lower levels of genetic diversity among the Mass and Conn viruses as well as sequence similarities with vaccine virus genomes suggest that the origin of the Mass and all but one of the Conn viruses was likely vaccine virus that had been circulating in the field for an unknown but apparently short period of time. The genetic data also identified a recombinant IBV isolate with 7 breakpoints distributed across the entire genome suggesting that viruses within the same serotype can have a high degree of genetic variability outside of the spike gene. These data are important because inaccurate measures of genetic diversity and mutation rates could lead to underestimates of the ability of IBV to change and potentially emerge to cause disease.