- Volume 105, Issue 12, 2024

It is important to be able to retrospectively determine severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections with high accuracy, both for post-coronavirus disease 2019 (COVID-19) epidemiological studies, and to distinguish between Long COVID and other multi-syndromic diseases that have overlapping symptoms. Although serum antibody levels can be measured to retrospectively diagnose SARS-CoV-2 infections, peptide stimulation of memory T cell responses is a more sensitive approach. This is because robust memory T cells are generated after SARS-CoV-2 infection and persist even after antibodies wane below detectability thresholds. In this study, we compare T cell responses using FluoroSpot-based methods and overnight stimulation of whole blood with SARS-CoV-2 peptides followed by an ELISA. Both approaches have comparable sensitivity and specificity but require different equipment and samples to be used. Furthermore, the elimination of peptides that cross-react with other coronaviruses increases the assay specificity but trades off some sensitivity. Finally, this approach can be used on archival, cryopreserved PBMCs. This work shows comparative advantages for several methods to measure SARS-CoV-2 T cell responses that could be utilized by any laboratory studying the effects of the coronavirus disease 2019 pandemic.

Respiratory syncytial virus (RSV) is a leading cause of respiratory infection, hospitalization and death in infants worldwide. No fully effective RSV therapy using direct antivirals is marketed. Since clinical efficacy data from naturally infected patients for such antivirals are not available yet, animal studies are indispensable to predict therapeutic intervention. Here, we report the impact of an RSV fusion inhibitor, JNJ-49214698, on severe RSV-associated acute lower respiratory tract infection (ALRTI) in neonatal lambs. Randomized animals were treated once daily with 25 mg/kg JNJ-49214698, starting either before RSV infection, 1 day post-infection or as late as peak lung viral load on Day 3 post-infection. Treatment efficacy was assessed by scoring clinical signs of illness, development of RSV-induced gross and microscopic lung lesions and measuring virus titres in the lungs. Treatment with JNJ-49214698 was very effective in all treatment groups. Even in animals for which treatment was delayed until peak viral load was reached, a reduced amount and severity of gross and microscopic lesions, as well as RSV titres and RNA levels, were found. These results strongly suggest that treatment with small-molecule fusion inhibitors is an effective strategy to treat patients who are diagnosed with an RSV-induced ALRTI.

Lassa virus (LASV) is an Old World (OW) mammarenavirus that causes Lassa fever, a life-threatening acute febrile disease endemic in West Africa. Lymphocytic choriomeningitis virus (LCMV) is a worldwide-distributed, prototypic OW mammarenavirus of clinical significance that has been largely neglected as a human pathogen. No licensed OW mammarenavirus vaccines are available, and the current therapeutic option is limited to the off-label use of ribavirin, which offers only partial efficacy. This situation underscores the urgent need to develop novel antivirals against human pathogenic mammarenaviruses. Previously, we showed that afatinib, a pan-ErbB tyrosine kinase inhibitor, inhibited multiple steps of the life cycles of OW LASV and LCMV, as well as the New World Junín virus vaccine strain Candid#1. In the present study, we investigated the inhibitory effect of U-73122, a phospholipase C inhibitor that acts downstream of ErbB signalling, on LCMV multiplication. U-73122 inhibited WT recombinant (r) LCMV multiplication in cultured cells. Preincubation of cell-free LCMV virions with U-73122 resulted in impaired virion infectivity. U-73122 also inhibited the infection of rLCMVs expressing heterologous viral glycoproteins, including the vesicular stomatitis Indiana virus (VSIV) glycoprotein, whereas WT VSIV infection was not affected by U-73122 treatment. Our results show the novel bioactivity of U-73122 as an LCMV inhibitor and indicate the presence of a virion-associated molecule that is necessary for virion infectivity and can be exploited as a potential antiviral drug target against human pathogenic mammarenavirus infections.

In Mononegavirales, phosphoproteins (P) are essential polymerase cofactors, forming oligomers and interacting with viral components to facilitate replication. Previous studies have demonstrated that a P-derived peptide (PFr) from the respiratory syncytial virus (RSV), containing the oligomerization domain (OD) and C-terminal domain (CTD), effectively inhibits RSV replication. Here, we extend this approach to paramyxoviruses, including HPIV3, MeV and MuV. Customized PFrs exhibited potent inhibitory effects against their respective viruses, with IC50 values below 100 nM, while showing minimal cytotoxicity. These findings highlight the potential of targeting P oligomerization as a broad-spectrum antiviral strategy for paramyxoviruses and other mononegaviruses.

The Bombyx mori nucleopolyhedrovirus (BmNPV) is a DNA virus that affects the silkworm, B. mori, causing substantial economic losses in sericulture. This study investigates the mechanisms underlying budded virus egress, focusing on the roles of the ubiquitin-proteasome pathway (UPP) machinery. BmNPV produces two virion types: budded virions (BVs) and occlusion-derived virions (ODVs), which differ in their envelope origins and functions. Recent findings suggest similarities in the budding pathways of BmNPV and Autographa californica multiple nucleopolyhedrovirus (AcMNPV), involving plasma membrane budding and multivesicular body (MVB) pathways. The study reveals that specific UPP-related proteins, including 26S proteasome non-ATPase regulatory subunit 14 (PSMD14), polyubiquitin, proteasome alpha subunit 6 (PSMA6) and proteasome zeta subunit (PSMZ), are involved in BV egress. Using recombinant viruses and UPP inhibitors, we demonstrate the necessity of these proteins for GP64 secretion and effective BV release. RNA interference and cell surface display of GP64 analyses further validate the critical role of UPP in BmNPV BV egress and protein secretion. This research enhances our understanding of the mechanisms behind BmNPV MVB budding and GP64 secretion while also identifying potential targets for controlling the virus in sericulture.