Palmitoylation of the Bovine Foamy Virus Envelope Glycoprotein Is Required for Viral Replication

Effects of Chemokine Ligand 2 on Budding of Bovine Foamy Virus

The endosomal sorting complex required for transport (ESCRT) machinery is essential for the budding of retroviruses such as human immunodeficiency virus (HIV) and bovine foamy virus (BFV), which rely on their late domain to recruit ESCRT complexes to facilitate budding. However, the impact of intracellular host proteins on BFV budding remains poorly understood. In this study, we aimed to investigate the impact of CCL2 on BFV budding and interactions with key host proteins. Our results indicate that CCL2 promotes BFV budding in an ALG-2-interacting protein X (Alix)-dependent manner by enhancing the interaction between Alix and BFV Gag (BGag). Notably, we found a link between Alix, BGag and CCL2, with Alix mediating the interaction between the latter two. Furthermore, we observed that natural host bovine CCL2 also has a facilitating role in the budding process of BFV, similar to human CCL2. Taken together, these results demonstrate that CCL2 promotes BFV budding by enhancing the Alix-BGag association.

Palmitoylation at Residue C221 of Japanese Encephalitis Virus NS2A Protein Contributes to Viral Replication Efficiency and Virulence

Palmitoylation of viral proteins is crucial for host-virus interactions. In this study, we examined the palmitoylation of Japanese encephalitis virus (JEV) nonstructural protein 2A (NS2A) and observed that NS2A was palmitoylated at the C221 residue of NS2A. Blocking NS2A palmitoylation by introducing a cysteine-to-serine mutation at C221 (NS2A/C221S) impaired JEV replication in vitro and attenuated the virulence of JEV in mice. NS2A/C221S mutation had no effect on NS2A oligomerization and membrane-associated activities, but reduced protein stability and accelerated its degradation through the ubiquitin-proteasome pathway. These observations suggest that NS2A palmitoylation at C221 played a role in its protein stability, thereby contributing to JEV replication efficiency and virulence. Interestingly, the C221 residue undergoing palmitoylation was located at the C-terminal tail (amino acids 195 to 227) and is removed from the full-length NS2A following an internal cleavage processed by viral and/or host proteases during JEV infection. IMPORTANCE An internal cleavage site is present at the C terminus of JEV NS2A. Following occurrence of the internal cleavage, the C-terminal tail (amino acids 195 to 227) is removed from the full-length NS2A. Therefore, it was interesting to discover whether the C-terminal tail contributed to JEV infection. During analysis of viral palmitoylated protein, we observed that NS2A was palmitoylated at the C221 residue located at the C-terminal tail. Blocking NS2A palmitoylation by introducing a cysteine-to-serine mutation at C221 (NS2A/C221S) impaired JEV replication in vitro and attenuated JEV virulence in mice, suggesting that NS2A palmitoylation at C221 contributed to JEV replication and virulence. Based on these findings, we could infer that the C-terminal tail might play a role in the maintenance of JEV replication efficiency and virulence despite its removal from the full-length NS2A at a certain stage of JEV infection.

Development of the H3N2 influenza microneedle vaccine for cross-protection against antigenic variants

Due to the continuously mutating nature of the H3N2 virus, two aspects were considered when preparing the H3N2 microneedle vaccines: (1) rapid preparation and (2) cross-protection against multiple antigenic variants. Previous methods of measuring hemagglutinin (HA) content required the standard antibody, thus rapid preparation of H3N2 microneedle vaccines targeting the mutant H3N2 was delayed as a result of lacking a standard antibody. In this study, H3N2 microneedle vaccines were prepared by high performance liquid chromatography (HPLC) without the use of an antibody, and the cross-protection of the vaccines against several antigenic variants was observed. The HA content measured by HPLC was compared with that measured by ELISA to observe the accuracy of the HPLC analysis of HA content. The cross-protection afforded by the H3N2 microneedle vaccines was evaluated against several antigenic variants in mice. Microneedle vaccines for the 2019–20 seasonal H3N2 influenza virus (19–20 A/KS/17) were prepared using a dip-coating process. The cross-protection of 19–20 A/KS/17 H3N2 microneedle vaccines against the 2015–16 seasonal H3N2 influenza virus in mice was investigated by monitoring body weight changes and survival rate. The neutralizing antibody against several H3N2 antigenic variants was evaluated using the plaque reduction neutralization test (PRNT). HA content in the solid microneedle vaccine formulation with trehalose post-exposure at 40℃ for 24 h was 48% and 43% from the initial HA content by HPLC and ELISA, respectively. The vaccine was administered to two groups of mice, one by microneedles and the other by intramuscular injection (IM). In vivo efficacies in the two groups were found to be similar, and cross-protection efficacy was also similar in both groups. HPLC exhibited good diagnostic performance with H3N2 microneedle vaccines and good agreement with ELISA. The H3N2 microneedle vaccines elicited a cross-protective immune response against the H3N2 antigenic variants. Here, we propose the use of HPLC for a more rapid approach in preparing H3N2 microneedle vaccines targeting H3N2 virus variants.

[Viral hepatitis A to E: prevalence, pathogen characteristics, and pathogenesis]

Bei der viralen Hepatitis handelt es sich um eine akute oder chronische Entzündung der Leber, die durch verschiedene Viren verursacht wird. Weltweit leiden derzeit ca. 325 Mio. Menschen an der chronischen Form. Jährlich versterben insgesamt ca. 1,6 Mio. an den Folgen einer viralen Hepatitis. Die Hepatitisviren werden in 5 Erregergruppen unterteilt, die mit den Buchstaben A bis E bezeichnet werden (HAV–HEV). Diese unterscheiden sich in Phylogenie, Übertragung, Epidemiologie, Wirtsspezifität, Lebenszyklus, Struktur und in speziellen Aspekten der Pathogenese.

Das strikt humanpathogene HAV, Teil der Familie Picornaviridae, induziert meist nur akute Hepatitiden und ist primär in Entwicklungsländern verbreitet. Das den Hepeviridae zugeordnete HEV beschreibt eine ähnliche Epidemiologie, ist jedoch durch sein zoonotisches Potenzial auch in Industrienationen weitverbreitet und kann zusätzlich eine chronische Erkrankung induzieren. Eine Chronifizierung tritt ebenso bei dem weltweit verbreiteten HBV (Hepadnaviridae) auf, dessen Satellitenvirus HDV (Kolmioviridae) das vorhandene kanzerogene Potenzial noch einmal erhöht. Das ebenfalls weltweit verbreitete HCV (Flaviviridae) birgt ein äußerst hohes Risiko der Chronifizierung und somit ebenfalls ein stark erhöhtes, kanzerogenes Potenzial.

Die Erreger der viralen Hepatitis unterscheiden sich in ihren Eigenschaften und Lebenszyklen. Eine differenzierte Betrachtung im Hinblick auf Epidemiologie, Nachweismethoden und Prävention ist daher angezeigt. Obwohl robuste Therapien, und im Falle einzelner Erreger auch Vakzine, vorhanden sind, muss die Forschung insbesondere in Hinblick auf die armutsassoziierten Erreger erheblich vorangetrieben werden.

S-acylation of SARS-CoV-2 spike protein: Mechanistic dissection, in vitro reconstitution and role in viral infectivity

S-acylation, also known as palmitoylation, is the most widely prevalent form of protein lipidation, whereby long-chain fatty acids get attached to cysteine residues facing the cytosol. In humans, 23 members of the zDHHC family of integral membrane enzymes catalyze this modification. S-acylation is critical for the life cycle of many enveloped viruses. The Spike protein of SARS-CoV-2, the causative agent of COVID-19, has the most cysteine-rich cytoplasmic tail among known human pathogens in the closely related family of β-coronaviruses; however, it is unclear which of the cytoplasmic cysteines are S-acylated, and what the impact of this modification is on viral infectivity. Here we identify specific cysteine clusters in the Spike protein of SARS-CoV-2 that are targets of S-acylation. Interestingly, when we investigated the effect of the cysteine clusters using pseudotyped virus, mutation of the same three clusters of cysteines severely compromised viral infectivity. We developed a library of expression constructs of human zDHHC enzymes and used them to identify zDHHC enzymes that can S-acylate SARS-CoV-2 Spike protein. Finally, we reconstituted S-acylation of SARS-CoV-2 Spike protein in vitro using purified zDHHC enzymes. We observe a striking heterogeneity in the S-acylation status of the different cysteines in our in cellulo experiments, which, remarkably, was recapitulated by the in vitro assay. Altogether, these results bolster our understanding of a poorly understood posttranslational modification integral to the SARS-CoV-2 Spike protein. This study opens up avenues for further mechanistic dissection and lays the groundwork toward developing future strategies that could aid in the identification of targeted small-molecule modulators.