Prevalence and Seroprevalence of Non-SARS Human Coronaviruses 229E and OC43 in East Tyrol/Austria

The recent SARS-CoV-2 pandemic renewed interest in other previously discovered human coronaviruses—the non-severe acute respiratory syndrome human coronavirus (non-SARS hCoVs) and this study is a starting point for a closer investigation of those. With the pandemic behind us we believe it to be important to also examine the current and past respiratory pathogen landscape in the patient population in our care. Therefore, 954 nasopharyngeal swabs of patients with respiratory diseases collected between October 2018 and March 2020 were tested against the pathogens Mycoplasma pneumoniae, Bordetella pertussis, Influenza A and virus, Human metapneumovirus, respiratory syncytial virus, Parainfluenza virus, human Adenovirus and Polyoma virus BK/JC. Swabs negative against these pathogens were further tested for OC43 and 229E by RT-qPCR. Human coronaviruses 229E and OC43 were proven as the causative agents in a considerable number of cases, confirmed by PCR. Overall, our results show that those two non-SARS hCoVs were responsible for 13.9% (11 of 79) of infections with flu-like symptoms of unknown etiology in the study area. In the subsequent seroprevalence study, it was shown that the seroprevalence rate of IgG antibodies against 229E and OC43 was over 50%, indicating that a big part of the population in our study area has been in contact with these non-SARS-CoVs and has built the specific humoral immune response accordingly.

The mutational dynamics of the SARS-CoV-2 virus in serial passages in vitro

Since its outbreak in 2019,Severe Acute Respiratory Syndrome Coronavirus 2(SARS-Co V-2)keeps surprising the medical community by evolving diverse immune escape mutations in a rapid and effective manner.To gain deeper insight into mutation frequency and dynamics,we isolated ten ancestral strains of SARS-Co V-2 and performed consecutive serial incubation in ten replications in a suitable and common cell line and subsequently analysed them using RT-q PCR and whole genome sequencing.Along those lines we hoped to gain fundamental insights into the evolutionary capacity of SARS-Co V-2 in vitro.Our results identified a series of adaptive genetic changes,ranging from unique convergent substitutional mutations and hitherto undescribed insertions.The region coding for spike proved to be a mutational hotspot,evolving a number of mutational changes including the already known substitutions at positions S:484 and S:501.We discussed the evolution of all specific adaptations as well as possible reasons for the seemingly inhomogeneous potential of SARS-Co V-2 in the adaptation to cell culture.The combination of serial passage in vitro with whole genome sequencing uncovers the immense mutational potential of some SARS-Co V-2 strains.The observed genetic changes of SARS-Co V-2 in vitro could not be explained solely by selectively neutral mutations but possibly resulted from the action of directional selection accumulating favourable genetic changes in the evolving variants,along the path of increasing potency of the strain.Competition among a high number of quasi-species in the SARS-Co V-2 in vitro population gene pool may reinforce directional selection and boost the speed of evolutionary change.