The novel coronavirus SARS-CoV-2: From a zoonotic infection to coronavirus disease 2019.

The novel coronavirus (CoV), severe acute respiratory syndrome (SARS)-CoV-2 is an international public health emergency. Until now, the intermediate host and mechanisms of the interspecies jump of this virus are unknown. Phylogenetic analysis of all available bat CoV complete genomes was performed to analyze the relationships between bat CoV and SARS-CoV-2. To suggest a possible intermediate host, another phylogenetic reconstruction of CoV genomes obtained from animals that were hypothetically commercialized in the Chinese markets was also carried out. Moreover, mutation analysis was executed to suggest genomic regions that may have permitted the adaptation of SARS-CoV-2 to the human host. The phylogenetic analysis demonstrated that SARS-CoV-2 formed a cluster with the bat CoV isolate RaTG13. Possible CoV interspecies jumps among bat isolates were also observed. The phylogenetic tree reconstructed from CoV strains belonging to different animals demonstrated that SARS-CoV-2, bat RaTG13, and pangolin CoV genomes formed a monophyletic cluster, demonstrating that pangolins may be suggested as SARS-CoV-2 intermediate hosts. Three AA substitutions localized in the S1 portion of the S gene were observed, some of which have been correlated to structural modifications of the S protein which may facilitate SARS-CoV-2 tropism to human cells. Our analysis shows the tight relationship between SARS-CoV-2 and bat SARS-like strains. It also hypothesizes that pangolins might have been possible intermediate hosts of the infection. Some of the observed AA substitutions in the S-binding protein may serve as possible adaptation mutations in humans but more studies are needed to elucidate their function.

First Report of Wenzhou sobemo-like virus 4 in Aedes albopictus (Diptera: Culicidae) in Latin America.

Insect-specific viruses (ISVs) are viruses that replicate exclusively in arthropod cells. Many ISVs have been studied in mosquitoes as many of them act as vectors for human etiological agents, such as arboviruses. Aedes (Stegomyia) albopictus is an important potential vector of several arboviruses in Brazil, such as dengue (DENV), Zika (ZIKV) and chikungunya (CHIKV). The development of next-generation sequencing metagenomics has enabled the discovery and characterization of new ISVs. Ae. albopictus eggs were collected using oviposition traps placed in two urban parks in the city of São Paulo, Brazil. The Aedes albopictus females were divided into pools and the genetic material was extracted and processed for sequencing by metagenomics. Complete genomes of ISV Wenzhou sobemo-like virus 4 (WSLV4) were obtained in three of the four pools tested. This is the first detection of ISV WSLV4 in Ae. albopictus females in Latin America. Further studies on ISVs in Ae. albopictus are needed to better understand the role of this species in the dynamics of arbovirus transmission in the Americas.

Rapid viral metagenomics using SMART-9N amplification and nanopore sequencing.

Emerging and re-emerging viruses are a global health concern. Genome sequencing as an approach for monitoring circulating viruses is currently hampered by complex and expensive methods. Untargeted, metagenomic nanopore sequencing can provide genomic information to identify pathogens, prepare for or even prevent outbreaks. SMART (Switching Mechanism at the 5' end of RNA Template) is a popular approach for RNA-Seq but most current methods rely on oligo-dT priming to target polyadenylated mRNA molecules. We have developed two random primed SMART-Seq approaches, a sequencing agnostic approach 'SMART-9N' and a version compatible rapid adapters  available from Oxford Nanopore Technologies 'Rapid SMART-9N'. The methods were developed using viral isolates, clinical samples, and compared to a gold-standard amplicon-based method. From a Zika virus isolate the SMART-9N approach recovered 10kb of the 10.8kb RNA genome in a single nanopore read. We also obtained full genome coverage at a high depth coverage using the Rapid SMART-9N, which takes only 10 minutes and costs up to 45% less than other methods. We found the limits of detection of these methods to be 6 focus forming units (FFU)/mL with 99.02% and 87.58% genome coverage for SMART-9N and Rapid SMART-9N respectively. Yellow fever virus plasma samples and SARS-CoV-2 nasopharyngeal samples previously confirmed by RT-qPCR with a broad range of Ct-values were selected for validation. Both methods produced greater genome coverage when compared to the multiplex PCR approach and we obtained the longest single read of this study (18.5 kb) with a SARS-CoV-2 clinical sample, 60% of the virus genome using the Rapid SMART-9N method. This work demonstrates that SMART-9N and Rapid SMART-9N are sensitive, low input, and long-read compatible alternatives for RNA virus detection and genome sequencing and Rapid SMART-9N improves the cost, time, and complexity of laboratory work.