Human BST2 inhibits rabies virus release independently of cysteine-linked dimerization and asparagine-linked glycosylation.

The innate immune response is a first-line defense mechanism triggered by rabies virus (RABV). Interferon (IFN) signaling and ISG products have been shown to confer resistance to RABV at various stages of the virus's life cycle. Human tetherin, also known as bone marrow stromal cell antigen 2 (hBST2), is a multifunctional transmembrane glycoprotein induced by IFN that has been shown to effectively counteract many viruses through diverse mechanisms. Here, we demonstrate that hBST2 inhibits RABV budding by tethering new virions to the cell surface. It was observed that release of virus-like particles (VLPs) formed by RABV G (RABV-G VLPs), but not RABV M (RABV-G VLPs), were suppressed by hBST2, indicating that RABV-G has a specific effect on the hBST2-mediated restriction of RABV. The ability of hBST2 to prevent the release of RABV-G VLPs and impede RABV growth kinetics is retained even when hBST2 has mutations at dimerization and/or glycosylation sites, making hBST2 an antagonist to RABV, with multiple mechanisms possibly contributing to the hBST2-mediated suppression of RABV. Our findings expand the knowledge of host antiviral mechanisms that control RABV infection.

The immunogenicity and reactogenicity of four COVID-19 booster vaccinations against SARS-CoV-2 variants following CoronaVac or ChAdOx1 nCoV-19 primary series.

BACKGROUND: The appropriate COVID-19 booster vaccine following inactivated or adenoviral vector COVID-19 vaccination is unclear. OBJECTIVE: To investigate the immunogenicity of four COVID-19 booster vaccines. METHODS: We prospectively enrolled healthy adults who received a two-dose CoronaVac or ChAdOx1 8-12 weeks earlier and allocated them to receive one of the following booster vaccine: inactivated (BBIBP-CorV), ChAdOx1 or mRNA (BNT162b2 at full [30 µg] and half [15 µg] dose) vaccines. We determined the reactogenicity and the humoral (anti-receptor binding domain IgG (anti-RBD-IgG), neutralizing antibodies (nAb) against Delta, Beta and Omicron variants) and cellular immunity measuring by interferon gamma (IFN-γ) responses post-booster. AR patients. RESULTS: Among the 352 participants (179 CoronaVac and 173 ChAdOx1 participants), 285 (81%) were female, and median age was 39 (IQR: 31-47) years. Two weeks post-booster, both 30 µg- and 15 µg- BNT162b2 induced the highest anti-RBD IgG concentration (BAU/mL); Coronavac-prime: 30 µg-BNT162b2, 5152.2 (95%CI 4491.7-5909.8); 15 µg-BNT162b2, 3981.1 (3397.2-4665.4); ChAdOx1, 1358.0 (1141.8-1615.1); BBIBP-CorV, 154.6 (92.11-259.47); ChAdOx1-prime: 30 µg-BNT162b2, 2363.8 (2005.6-2786.1; 15 µg-BNT162b2, 1961.9 (1624.6-2369.1); ChAdOx1, 246.4 (199.6-304.2); BBIBP-CorV, 128.1 (93.5-175.4). Similarly, both 30 µg- and 15 µg- BNT162b2 boosting induced the highest nAb titers against Beta, Delta and Omicron BA.1 variants and highest T-cell response at 2 weeks after boosting. While all BNT162b2 or heterologous ChAdOx1-boosted participants had nAb against Omicron, these were < 50% for BBIBP-CorV and 75% for homologous ChAdOx1-boosted participants. There was significant decrease in nAb ( > 4-fold) at 16-20 weeks post booster for all groups. CONCLUSIONS: Heterologous boosting with BNT162b2 following CoronaVac or ChAdOx1 primary series is most immunogenic. Additional studies are needed to verify the clinical efficacy and persistence of immunity following half-dose BNT162b2.

Immunogenicity and reactogenicity against the SARS-CoV-2 variants following heterologous primary series involving CoronaVac, ChAdox1 nCov-19 and BNT162b2 plus BNT162b2 booster vaccination: An open-label randomized study in healthy Thai adults.

We evaluated the immunogenicity and reactogenicity of heterologous COVID-19 primary schedules involving BNT162b2 (Pfizer-BioNTech), ChAdOx1 nCoV-19 (AstraZeneca) and CoronaVac (Sinovac) in healthy adults, as well as booster response to BNT162b2 following heterologous CoronaVac and ChAdOx1 nCoV-19 regimens. Participants were randomized to one of seven groups that received two-dose homologous BNT162b2 or heterologous combinations of CoronaVac, ChAdOx1 nCoV-19 and BNT162b2, with 4 weeks interval. A total of 210 participants were enrolled, 30 in each group. Median age of participants was 38 (19-60) years, and 108/210 (51.43%) were female. Overall adverse events after the second dose were mild to moderate. We found that groups that received BNT162b2 as second dose induced the highest anti-receptor binding domain IgG response against the ancestral strain [BNT162b2: geometric mean concentration (GMC) 2133-2249 BAU/mL; ChAdOx1 nCoV-19: 851-1201; CoronaVac: 137-225 BAU/mL], neutralizing antibodies (NAb) against Beta and Delta, and interferon gamma response. All groups induced low to negligible NAb against Omicron after second dose. A BNT162b2 booster (third dose) following heterologous CoronaVac and ChAdOx1 nCoV-19 regimens induced >140-fold increase in NAb titers against Omicron. Our findings indicate that heterologous regimens using BNT162b2 as the second dose may be an alternative schedule to maximize immune response. While heterologous two-dose schedules induced low NAb against Omicron, the use of an mRNA vaccine booster dose substantially increased the Omicron response. These findings are relevant for low-income countries considering heterologous primary and booster COVID-19 vaccine schedules.

Chimeric Virus-like Particle-Based COVID-19 Vaccine Confers Strong Protection against SARS-CoV-2 Viremia in K18-hACE2 Mice.

Virus-like particles (VLPs) are highly immunogenic and versatile subunit vaccines composed of multimeric viral proteins that mimic the whole virus but lack genetic material. Due to the lack of infectivity, VLPs are being developed as safe and effective vaccines against various infectious diseases. In this study, we generated a chimeric VLP-based COVID-19 vaccine stably produced by HEK293T cells. The chimeric VLPs contain the influenza virus A matrix (M1) proteins and the SARS-CoV-2 Wuhan strain spike (S) proteins with a deletion of the polybasic furin cleavage motif and a replacement of the transmembrane and cytoplasmic tail with that of the influenza virus hemagglutinin (HA). These resulting chimeric S-M1 VLPs, displaying S and M1, were observed to be enveloped particles that are heterogeneous in shape and size. The intramuscular vaccination of BALB/c mice in a prime-boost regimen elicited high titers of S-specific IgG and neutralizing antibodies. After immunization and a challenge with SARS-CoV-2 in K18-hACE2 mice, the S-M1 VLP vaccination resulted in a drastic reduction in viremia, as well as a decreased viral load in the lungs and improved survival rates compared to the control mice. Balanced Th1 and Th2 responses of activated S-specific T-cells were observed. Moderate degrees of inflammation and viral RNA in the lungs and brains were observed in the vaccinated group; however, brain lesion scores were less than in the PBS control. Overall, we demonstrate the immunogenicity of a chimeric VLP-based COVID-19 vaccine which confers strong protection against SARS-CoV-2 viremia in mice.

Establishment of Human-Induced Pluripotent Stem Cell-Derived Neurons-A Promising In Vitro Model for a Molecular Study of Rabies Virus and Host Interaction.

Rabies is a deadly viral disease caused by the rabies virus (RABV), transmitted through a bite of an infected host, resulting in irreversible neurological symptoms and a 100% fatality rate in humans. Despite many aspects describing rabies neuropathogenesis, numerous hypotheses remain unanswered and concealed. Observations obtained from infected primary neurons or mouse brain samples are more relevant to human clinical rabies than permissive cell lines; however, limitations regarding the ethical issue and sample accessibility become a hurdle for discovering new insights into virus-host interplays. To better understand RABV pathogenesis in humans, we generated human-induced pluripotent stem cell (hiPSC)-derived neurons to offer the opportunity for an inimitable study of RABV infection at a molecular level in a pathologically relevant cell type. This study describes the characteristics and detailed proteomic changes of hiPSC-derived neurons in response to RABV infection using LC-MS/MS quantitative analysis. Gene ontology (GO) enrichment of differentially expressed proteins (DEPs) reveals temporal changes of proteins related to metabolic process, immune response, neurotransmitter transport/synaptic vesicle cycle, cytoskeleton organization, and cell stress response, demonstrating fundamental underlying mechanisms of neuropathogenesis in a time-course dependence. Lastly, we highlighted plausible functions of heat shock cognate protein 70 (HSC70 or HSPA8) that might play a pivotal role in regulating RABV replication and pathogenesis. Our findings acquired from this hiPSC-derived neuron platform help to define novel cellular mechanisms during RABV infection, which could be applicable to further studies to widen views of RABV-host interaction.

Interaction Between PEDV and Its Hosts: A Closer Look at the ORF3 Accessory Protein.

Porcine epidemic diarrhea virus (PEDV) is a causative agent of a highly contagious enteric disease in swine of all ages, leading to severe economic losses for the swine industry in many countries. One of the most effective approaches in controlling PEDV infection is vaccination. The ORF3 accessory protein has been proposed as a crucial viral virulence factor in a natural host. However, due to the lack of an extensive comparative study of ORF3, exactly how the ORF3 takes part in virus replication and pathogenesis as well as its role in host-virus interaction is unclear. In this review, we aim to discuss the current knowledge of ORF3 concerning its dispensability for viral replication in vitro, ability to modulate host responses, contribution to virus pathogenicity, and research gaps among ORF3 functional studies. These will be beneficial for further studies to a better understanding of PEDV biology and PEDV vaccine development.