The Origins of Severe Acute Respiratory Syndrome-Coronavirus-2

Development and application of a high-titer VSV-based HCoV-NL63 pseudovirus system via C-terminal 14 amino acid truncation of spike

To provide efficient tools for the development of novel antiviral drugs and vaccines of HCoV-NL63, it is urgently necessary to establish a safe, widely applicable, and high-titer NL63 pseudotyped particles (NL63pp) production system. In this research, we conducted a comparative analysis of several NL63pps, each with a truncated spike (S) protein missing part of its C-terminal amino acids. We discovered that deleting the C-terminal 14 amino acid sequence of the S protein (D14) led to a remarkable approximately 10-fold increase in the infection titer of VSV-based NL63pp. This value is higher than the titers of NL63pp packaged with S proteins having deletions of 18 or 24 amino acids at the C-terminus. Moreover, adding the VSV-G tag to the D14 C-terminus (D14V) resulted in an additional 30 % increase. We then constructed the recent prevalent HCoV-NL63 subgenotype C3 dual-reporter pseudovirus system C3-D14V, and found that C3-D14V had a higher infection efficiency. Utilizing this system, we investigated the susceptibility of several cell lines and observed that cells derived from liver (Huh7.5.1), small intestine (Caco-2) and lung (Calu-3) exhibited higher susceptibility. Furthermore, we applied this system to assess several bis-benzylisoquinoline alkaloids, notably, Cepharanthine demonstrated the highest inhibitory efficiency against NL63pp infection with EC50 0.61 μM. In conclusion, we have identified that S protein with a 14 amino acids deletion at the C-terminus significantly enhances the infection titer of HCoV-NL63 pseudovirus and provides an efficient VSV-based HCoV-NL63 dual-reporter (mCherry and luciferase2) pseudovirus system for various applications such as drug screening and antibody development in the future.

Retrospective Analysis of Vitamin D Deficiency in an Adult Population of Arad County, Western Romania (2019-2022)

Vitamin D, a steroid hormone synthesized primarily in the skin upon exposure to ultraviolet light, is widely deficient across global populations. This study aimed to fill the data gap in Western Romania by measuring 25-hydroxy-vitamin D levels in a cohort of 7141 from Arad County. It was observed that women, younger adults (18-29 years), and older adults (70-79 years) had notably lower vitamin D levels compared to the average population. Additionally, there was a rise in vitamin D levels over the four-year span of 2018-2022, coinciding with the COVID-19 pandemic. Our research provides fresh data on those most susceptible to vitamin D deficiency and lays the groundwork for educational campaigns on vitamin D supplementation benefits.

What do we know about the origin of COVID-19 three years later?

More than three years have passed since the first case of a new coronavirus infection (SARS-CoV-2) in the city of Wuhan (Hubei, China). The Wuhan Institute of Virology was founded in that city in 1956 and the country's first biosafety level 4 laboratory opened within that center in 2015. The coincidence that the first cases of infection emerged in the city where the virology institute's headquarters is located, the failure to 100% identify the virus' RNA in any of the coronaviruses isolated in bats, and the lack of evidence on a possible intermediate animal host in the contagion's transmission make it so that at present, there are doubts about the real origin of SARS-CoV-2. This article will review two theories: SARS-CoV-2 as a virus of zoonotic origin or as a leak from the high-level biosafety laboratory in Wuhan.