Prevalence of Human Coronaviruses in Children and Phylogenetic Analysis of HCoV-OC43 during 2016-2022 in Riyadh, Saudi Arabia.

With the emergence of SARS-CoV-2, routine surveillance combined with sequence and phylogenetic analysis of coronaviruses is urgently required. In the current study, the four common human coronaviruses (HCoVs), OC43, NL63, HKU1, and 229E, were screened in 361 clinical samples collected from hospitalized children with respiratory symptoms during four winter seasons. RT-PCR-based detection and typing revealed different prevalence rates of HCoVs across the four seasons. Interestingly, none of the four HCoVs were detected in the samples (n = 100) collected during the winter season of the COVID-19 pandemic. HCoV-OC43 (4.15%) was the most frequently detected, followed by 229E (1.1%). Partial sequences of S and N genes of OC43 from the winter seasons of 2015/2016 and 2021/2022 were used for sequence and phylogenetic analysis. Multiple sequence alignment of the two Saudi OC43s strains with international strains revealed the presence of sequence deletions and several mutations, of which some changed their corresponding amino acids. Glycosylation profiles revealed a number of O-and N-glycosylation sites in both genes. Based on phylogenetic analysis, four genotypes were observed with Riyadh strains grouped into the genotype C. Further long-term surveillance with a large number of clinical samples and sequences is necessary to resolve the circulation patterns and evolutionary kinetics of OC43 in Saudi Arabia.

Durability of SARS-CoV-2 Specific IgG Antibody Responses Following Two Doses of Match and Mixed COVID-19 Vaccines Regimens in Saudi Population.

Background: SARS-CoV-2 pandemic continues to threaten the human population with millions of infections and deaths worldwide. Vaccination campaigns undertaken by several countries have resulted in a notable decrease in hospitalization and deaths. However, with the emergence of new virus variants, it is critical to determine the longevity and the protection efficiency provided by the current authorized vaccines. Aim: The aims of this study are to provide data about the magnitude of immune responses in individuals fully vaccinated against COVID-19 in Riyadh province of Saudi Arabia. Also, to evaluate the continuity of specific IgG levels and compare the titers in individuals who have been received two doses of the matched and mixed vaccines, including Pfizer and AstraZeneca against SARS-CoV-2 during the period of three to six months. Moreover, we analyze the current state of immune response in terms of antibody responses in thepopulation postvaccination using homogenous or hetrogenous vaccine regimen. Methods: A total of 141 healthy volunteers were recruited to our study; blood (n=63) and the saliva samples (n=78) and were collected from fully vaccinated individuals in Riyadh city. We employed a specific ELISA assay in plasma and saliva of fully vaccinated individuals. Results: IgG levels varied with age groups with the highest concentration in the age group 19-29 years, but the age group (≥50) had the lowest IgG concentration. The IgG levels in both serum and saliva were higher after three months and start to wane after six months. Individuals who received mixed types of vaccines had significantly better response than Pfizer vaccine alone. Conclusion: The current study investigates the status of humoral responses in different age groups, in terms of antibody measurements. These data will help to evaluate the need for further COVID-19 vaccine doses and to what extent a two-dose regimen will protect vaccinated individuals.

SARS-CoV-2: An Overview of Virus Genetics, Transmission, and Immunopathogenesis.

The human population is currently facing the third and possibly the worst pandemic caused by human coronaviruses (CoVs). The virus was first reported in Wuhan, China, on 31 December 2019 and spread within a short time to almost all countries of the world. Genome analysis of the early virus isolates has revealed high similarity with SARS-CoV and hence the new virus was officially named SARS-CoV-2. Since CoVs have the largest genome among all RNA viruses, they can adapt to many point mutation and recombination events; particularly in the spike gene, which enable these viruses to rapidly change and evolve in nature. CoVs are known to cross the species boundaries by using different cellular receptors. Both animal reservoir and intermediate host for SARS-CoV-2 are still unresolved and necessitate further investigation. In the current review, different aspects of SARS-CoV-2 biology and pathogenicity are discussed, including virus genetics and evolution, spike protein and its role in evolution and adaptation to novel hosts, and virus transmission and persistence in nature. In addition, the immune response developed during SARS-CoV-2 infection is demonstrated with special reference to the interplay between immune cells and their role in disease progression. We believe that the SARS-CoV-2 outbreak will not be the last and spillover of CoVs from bats will continue. Therefore, establishing intervention approaches to reduce the likelihood of future CoVs spillover from natural reservoirs is a priority.