Hongxia Shao

Infectious bursal disease virus (IBDV) primarily triggers severe immunosuppression in birds and has resulted in substantial economic losses to the poultry industry globally. Here, a novel naturally reassortant IBDV strain, designated IBDV_G3, was isolated from quails during a disease outbreak in Jiangsu Province, China. Genome sequencing revealed that IBDV_G3 carried segment A derived from the serotype-2-related A0 lineage, while segment B clustered within the B1a classical-like lineage, and this genomic constellation was further confirmed in the original uncultured quail tissues. IBDV_G3 replicated efficiently in LMH cells without prior adaptation, and its VP2 was recognized by the serotype 1 VP2-specific monoclonal antibody 5G10. These findings suggest that quails may harbor reassortant IBDV strains and that the quail–chicken interface warrants continuous surveillance for IBDV reassortment and evolutionary variation.

Upon infection, viruses reprogram the host metabolic system to hijack metabolic resources for proliferation. Avian leukosis virus subgroup J (ALV-J), an avian oncogenic virus, poses significant challenges to the poultry industry. ALV-J infection upgrades monosaccharide N-acetylgalactosamine (GalNAc) and galactosyltransferase (core 1 β3-Gal-T) in DF-1 cells, both of which are crucial for O-linked glycosylation. Addition of GalNAc or overexpression of core 1 β3-Gal-T in DF-1 cells can promote ALV-J replication. ALV-J envelope protein (Env) undergoes complex post-translational modifications. Two O-linked glycosylation sites (T32 and T271) located in the head region of the ALV-J Env have been identified for the first time using liquid chromatography–mass spectrometry (LC–MS). The results of coimmunoprecipitation and flow cytometry indicate that mutations in T32 or T271 diminish ALV-J infection by affecting viral internalization, rather than attachment. The viral internalization efficiency was partially restored under a low pH environment. Incorporation of T32A and T271A into ALV-J led to significantly reduced replication capacity in vivo and viral shedding of the recombinant virus. These findings are valuable for our understanding of the roles of glycans in the ALV-J infection cycle, as well as for providing potential anti-ALV-J strategies.

Introduction: Infectious bursal disease (IBD) is a severe immunosuppressive disease caused by the infection of infectious bursal disease virus (IBDV) in chicken. Recently, an emerging mutant named novel variant IBDV (nVarIBDV) has rapidly spread in China and become a prevalent strain. However, little is known about the unique antigenic sites of nVarIBDV escaped from current IBDV vaccines.Methods: Here, the expressed hypervariable region (HVR) of VP2 (VP2-HVR) of nVarIBDV was used as an immunogen and a novel monoclonal antibody (mAb) against VP2 (mAb 5B5) was generated.Results: Immunofluorescence assay (IFA) and ELISA demonstrated that mAb 5B5 specifically reacted with nVarIBDV and its VP2 protein, but not with classical IBDV (cIBDV), very virulent IBDV (vvIBDV), or attenuated IBDV (attIBDV) strains. Epitope mapping and site mutagenesis assay revealed that mAb 5B5 recognized the conformational epitope in peak A (212–224 aa) and heptapeptide (326–332 aa) regions, and identified residue 221K in VP2 as the key antigenic site, which is conserved exclusively in nVarIBDV strains. Notably, K221Q mutation in VP2 of nVarIBDV significantly altered the reaction profile for sera against vvIBDV or cIBDV. Neutralization assays revealed that mAb 5B5 could inhibit replication of an engineered attIBDV carrying 221K in Leghorn male hepatoma (LMH) cells. Structural analysis further found that 221K is surface-exposed and alters local electrostatic potential, possibly facilitating immune evasion.Discussion: All these demonstrated that 221K is a unique antigenic site in VP2 of nVarIBDV associated with immune escape, providing novel insights into the antigenicity of nVarIBDV and novel targets for efficient diagnostics, vaccine design, and molecular surveillance of IBDV.

Background: Duck adenovirus 3 (DAdV-3) is an emerging pathogen that has caused severe economic losses to the duck industry in China. Recently, the infection of ducks with serotype 4 fowl adenovirus (FAdV-4) has also been reported in China. Therefore, an efficient bivalent vaccine to control the diseases caused by DAdV-3 and FAdV-4 is extremely urgent. In our previous study, a recombinant FAdV-4 expressing Fiber-2 of DAdV-3 was generated and designated as rFAdV-4-Fiber-2/DAdV-3. Methods: Here, the recombinant virus rFAdV-4-Fiber-2/DAdV-3 was inactivated to serve as a bivalent vaccine, and its immunogenicity and protective efficacy against DAdV-3 were evaluated in Muscovy ducks. Results: The subcutaneous injection of rFAdV-4-Fiber-2/DAdV-3 could efficiently induce antibodies against Fiber-2 of DAdV-3 and neutralize antibodies against FAdV-4. After challenges with DAdV-3, in comparison with the non-immunized ducks, the immunized ducks did not show any bodyweight loss, gross lesions, or histopathologic change. Moreover, viral loads in livers and kidneys from immunized ducks were undetectable, whereas those in non-immunized ducks with challenge were significantly high. Conclusions: All these data demonstrate that the inactivated recombinant virus rFAdV-4-Fiber-2/DAdV-3 has the potential to be an efficient vaccine candidate against both FAdV-4 and DAdV-3, although efficacy for FAdV-4 needs to be confirmed experimentally.

African swine fever (ASF), caused by the African swine fever virus (ASFV), has resulted in significant losses in the global pig industry. Considering the absence of effective vaccines, developing drugs against ASFV may be a crucial strategy for its prevention and control in the future. In this study, punicalagin, a polyphenolic substance extracted from pomegranate peel, was found to significantly inhibit ASFV replication in MA-104, PK-15, WSL, and 3D4/21 cells by screening an antiviral compound library containing 536 compounds. Time-of-addition studies demonstrated that punicalagin acted on early viral replication stages, impinging on viral attachment and internalization. Meanwhile, punicalagin could directly inactivate the virus according to virucidal assay. RT-qPCR and Western blot results indicated that punicalagin modulated the NF-κB/STAT3/NLRP3 inflammasome signaling pathway and reduced the levels of inflammatory mediators induced by ASFV. In conclusion, this study reveals the anti-ASFV activity of punicalagin and the mechanism of action, which may have great potential for developing effective drugs against ASFV.

African swine fever (ASF) has become a global pandemic due to inadequate prevention and control measures, posing a significant threat to the swine industry. Despite the approval of a single vaccine in Vietnam, no antiviral drugs against the ASF virus (ASFV) are currently available. Aloperine (ALO), a quinolizidine alkaloid extracted from the seeds and leaves of bitter beans, exhibits various biological functions, including anti-inflammatory, anti-cancer, and antiviral activities. In this study, we found that ALO could inhibit ASFV replication in MA-104, PK-15, 3D4/21, and WSL cells in a dose-dependent manner without cytotoxicity at 100 μM. Furthermore, it was verified that ALO acted on the co- and post-infection stages of ASFV by time-of-addition assay, and inhibited viral internalization rather than directly inactivating the virus. Notably, RT-qPCR analysis indicated that ALO did not exert anti-inflammatory activity during ASFV infection. Additionally, gene ontology (GO) and KEGG pathway enrichment analyses of transcriptomic data revealed that ALO could inhibit ASFV replication via the PRLR/JAK2 signaling pathway. Together, these findings suggest that ALO effectively inhibits ASFV replication in vitro and provides a potential new target for developing anti-ASFV drugs.

Marek’s disease (MD), caused by the Marek’s disease virus (MDV), is a common infectious tumor disease in chickens and was the first neoplastic disease preventable by vaccination. However, the vaccine cannot completely prevent virulent MDV infections, allowing both the vaccine and virulent MDV to coexist in the same chicken for extended periods. This study aims to investigate the changes in viral load of the very virulent strain Md5 and the rHVT-IBD vaccine in different chicken tissues using a real-time PCR assay. The results showed that the rHVT-IBD vaccine significantly reduced the viral load of MDV-Md5 in different organs, while the load of rHVT-IBD was significantly increased when co-infected with Md5. Additionally, co-infection with Md5 and rHVT-IBD in chickens not only changed the original viral load of both viruses but also affected the positive rate of Md5 at 14 days post-vaccination. The positive rate decreased from 100% to 14.29% (feather tips), 0% (skin), 33.33% (liver), 16.67% (spleen), 28.57% (thymus), 33.33% (bursa), and 66.67% (PBL), respectively. This study enhances our understanding of the interactions between HVT vector vaccines and very virulent MDV in chickens and provides valuable insights for the future development of MD vaccines.