Pseudotyped Viruses for Retroviruses.

Since the discovery of retroviruses, their genome and replication strategies have been extensively studied, leading to the discovery of several unique features that make them invaluable vectors for virus pseudotyping, gene delivery, and gene therapy. Notably, retroviral vectors enable the integration of a gene of interest into the host genome, they can be used to stably transduce both dividing and nondividing cells, and they can deliver relatively large genes. Today, retroviral vectors are commonly used for many research applications and have become an active tool in gene therapy and clinical trials. This chapter will discuss the important features of the retroviral genome and replication cycle that are crucial for the development of retroviral vectors, the different retrovirus-based vector systems that are commonly used, and finally the research and clinical applications of retroviral vectors.

Human coronaviruses: The emergence of SARS-CoV-2 and management of COVID-19.

To date, a total of seven human coronaviruses (HCoVs) have been identified, all of which are important respiratory pathogens. Recently, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), has led to a global pandemic causing millions of infections and deaths. Here, we summarize the discovery and fundamental virology of HCoVs, discuss their zoonotic transmission and highlight the weak species barrier of SARS-CoV-2. We also discuss the possible origins of SARS-CoV-2 variants of concern identified to date and discuss the experimental challenges in characterizing mutations of interest and propose methods to circumvent them. As the COVID-19 treatment and prevention landscape rapidly evolves, we summarize current therapeutics and vaccines, and their implications on SARS-CoV-2 variants. Finally, we explore how interspecies transmission of SARS-CoV-2 may drive the emergence of novel strains, how disease severity may evolve and how COVID-19 will likely continue to burden healthcare systems globally.

Schlafen 5 suppresses human immunodeficiency virus type 1 transcription by commandeering cellular epigenetic machinery.

Schlafen-5 (SLFN5) is an interferon-induced protein of the Schlafen family, which are involved in immune responses and oncogenesis. To date, little is known regarding its anti-HIV-1 function. Here, the authors report that overexpression of SLFN5 inhibits HIV-1 replication and reduces viral mRNA levels, whereas depletion of endogenous SLFN5 promotes HIV-1 replication. Moreover, they show that SLFN5 markedly decreases the transcriptional activity of HIV-1 long terminal repeat (LTR) via binding to two sequences in the U5-R region, which consequently represses the recruitment of RNA polymerase II to the transcription initiation site. Mutagenesis studies show the importance of nuclear localization and the N-terminal 1-570 amino acids fragment in the inhibition of HIV-1. Further mechanistic studies demonstrate that SLFN5 interacts with components of the PRC2 complex, G9a and Histone H3, thereby promoting H3K27me2 and H3K27me3 modification leading to silencing HIV-1 transcription. In concert with this, they find that SLFN5 blocks the activation of latent HIV-1. Altogether, their findings demonstrate that SLFN5 is a transcriptional repressor of HIV-1 through epigenetic modulation and a potential determinant of HIV-1 latency.