Regulation of RNA homeostasis or “RNAstasis” is a central step in eukaryotic gene expression. From transcription to decay, cellular messenger RNAs (mRNAs) associate with specific proteins in order to regulate their entire cycle, including mRNA localization, translation and degradation, among others. The best characterized of such RNA-protein complexes, today named membraneless organelles, are Stress Granules (SGs) and Processing Bodies (PBs) which are involved in RNA storage and RNA decay/storage, respectively. Given that SGs and PBs are generally associated with repression of gene expression, viruses have evolved different mechanisms to counteract their assembly or to use them in their favor to successfully replicate within the host environment. In this review we summarize the current knowledge about the viral regulation of SGs and PBs, which could be a potential novel target for the development of broad-spectrum antiviral therapies.

Chile has one of the worst numbers worldwide in terms of SARS-CoV-2 positive cases and COVID-19–related deaths per million inhabitants; thus, characterization of neutralizing antibody (NAb) responses in the general population is critical to understanding of immunity at the local level. Given our inability to perform massive classical neutralization assays due to the scarce availability of BSL-3 facilities in the country, we developed and fully characterized an HIV-based SARS-CoV-2 pseudotype, which was used in a 96-well plate format to investigate NAb responses in samples from individuals exposed to SARS-CoV-2 or treated with convalescent plasma. We also identified samples with decreased or enhanced neutralization activity against the D614G spike variant compared with the wild type, indicating the relevance of this variant in host immunity. The data presented here represent the first insights into NAb responses in individuals from Chile, serving as a guide for future studies in the country.

Hantaviruses infect human cells through cell attachment and subsequent fusion of viral and cellular membranes at low pH. This largely unknown entry process is mediated by the Gn and Gc glycoproteins, anchored at the viral envelope membrane. Performing bioinformatic analysis and peptide-liposome-binding assays we suggested in a former report that Gc of Andes virus (ANDV) and other hantaviruses corresponds to the viral fusion protein sharing characteristics with class II fusion proteins. To gain insights into the fusion protein of hantaviruses, residues within the previously predicted fusion peptide of ANDV Gc were substituted and mutant proteins tested in fusion and infection assays. To ensure proper folding of mutant proteins, they were first characterized for trafficking to the plasma membrane and incorporation on to ANDV Gn/Gc-pseudotyped lentiviral particles. Cell attachment of these particles was assessed using a newly developed binding assay and their subsequent entry properties determined by FACS analysis of transduced cells expressing the GFP reporter gene. Furthermore, a three-colour-based cell-cell fusion assay of ANDV Gn/Gc expressing cells was performed. The results indicate an essential role of conserved Gc residues W115 and N118 in membrane fusion. Conversely, substitutions of the non-conserved Gc residue G116 did not considerably affect fusion and infection. Altogether, the findings are fully consistent with our earlier prediction suggesting Gc residues 115-121 as an internal fusion peptide and further emphasize the importance of aromatic and polar residues in hantavirus-cell membrane fusion.

The ongoing COVID-19 pandemic has reached more than 200 countries and territories worldwide. Given the large requirement of SARS-CoV-2 diagnosis and considering that RNA extraction kits are in short supply, we investigated whether two commercial RT-qPCR kits were compatible with direct SARS-CoV-2 detection from nasopharyngeal swab samples. We show that one of the tested kits is fully compatible with direct SARS-CoV-2 detection suggesting that omission of an RNA extraction step should be considered in SARS-CoV-2 diagnosis.

We identified 3 novel and distinct avulaviruses from Gentoo penguins sampled in Antarctica. We isolated these viruses and sequenced their complete genomes; serologic assays demonstrated that the viruses do not have cross-reactivity between them. Our findings suggest that these 3 new viruses represent members of 3 novel avulavirus species.