Wei Gao

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.

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.

The outbreak of goose gout disease caused by novel goose astrovirus type 1 (GAstV-1) has resulted in huge economic losses to the goose industry in China si

Coagulase is a critical factor for distinguishing Staphylococcus aureus and coagulase-negative Staphylococcus. Our previous studies demonstrated that the null mutation of coagulase (coa) or its direct regulator, SaeRS, significantly enhanced the ability of S. aureus (CA-MRSA 923) to survive in human blood in vitro. This led us to further investigate the role of coagulase and its direct regulator, SaeRS, in the pathogenicity of CA-MRSA 923 in bacteremia during infection. In this study, we found that the null mutation of coa significantly decreased the mortality of CA-MRSA 923; moreover, the single null mutation of saeRS and the double deletion of coa/saeRS abolished the virulence of CA-MRSA 923. Moreover, the mice infected with either the saeRS knockout or the coa/saeRS double knockout mutant exhibited fewer histological lesions and less neutrophils infiltration in the infected kidneys compared to those infected with the coa knockout mutant or their parental control. Furthermore, we examined the impact of coa and saeRS on bacterial survival in vitro. The null mutation of coa had no impact on bacterial survival in mice blood, whereas the deletion mutation of saeRS or coa/saeRS significantly enhanced bacterial survival in mice blood. These data indicate that SaeRS plays a key role in the lethality of CA-MRSA 923 bacteremia, and that coagulase is one of the important virulence factors that is regulated by SaeRS and contributes to the pathogenicity of CA–MRSA 923.

Neuraminidases (NAs) of H9N2 avian influenza virus (AIV) and H3N2 human seasonal influenza virus (HSIV) share similar antigenic structures. However, there are few reports on epitopes shared by these two NAs. We previously reported a monoclonal antibody (mAb) 1G8 against the NA of H9N2 AIV with neuraminidase inhibition (NI) ability. In this study, 1G8 was shown to cross-react with and inhibit the NA of H3N2 HSIV. In a passive transfer experiment, 1G8 provided protection to mice challenged with rescued H1N2 viruses carrying H9N2 NA or H3N2 NA. Mutation at amino acid position 199 was also selected and proved to be crucial for H3N2 HSIV to escape from mAb 1G8. Moreover, we found that residue 199 contributed to inducing broad protective antibodies without the influence of the N-linked glycosylation at amino acid position 200 in NAs. Residues as residue 199, which are not shielded by glycosylation modification, would form ideal epitopes for developing universal vaccine and protective antibodies.

In China, although the ALV eradication program and the MD vaccination strategy greatly reduce the disease burdens caused by the infection of ALV and MDV, the frequent emergence of novel ALV-K or vvMDV in the vaccinated chicken flock challenges the current control strategies for both diseases. In Guangdong Province, an indigenous chicken flock was infected with neoplastic disease. Hematoxylin–eosin staining of the tissues showed the typical characteristics of MDV and classical ALV infection. The PCR and sequencing data demonstrated that the identified MDV was clustered into a very virulent MDV strain endemic in domestic chickens in China. Moreover, subgroups ALV-A and ALV-K were efficiently recovered from two samples. The full genome sequence revealed that the ALV-K isolate was phylogenetically close to the ALV TW3593 isolate from Taiwan Province. A co-infection of vvMDV with multiple ALV subgroups emerged in a chicken flock with neoplastic disease in Guangdong Province. The co-infection with different subgroups of ALV with vvMDV in one chicken flock poses the risk for the emergence of novel ALVs and heavily burdens the control strategy for MDV.

Some immune escape mutants of H9N2 virus and the corresponding mutations in hemagglutinin (HA) have been documented, but little is known about the impact of a single mutation on the antigenicity and pathogenesis of H9N2. In this study, seven critical sites in HA associated with the antigenicity were identified and the effects of a HA mutation (N166D) derived from a H9N2 escape mutant (m3F2) were investigated. Although N166D did not significantly affect viral replication in Madin–Darby canine kidney (MDCK) cells and viral shedding in the larynx and cloaca of chicken, N166D attenuated the pathogenesis of the virus in mice. Compared to the rescued RgPR8-H9_166D, RgPR8-H9_166N caused greater body weight loss and higher viral titers in the lungs of the infected mice. Moreover, hemagglutination inhibition (HI) assay for the sera from the chickens infected with wild type H9N2 and mutant m3F2 showed that N166D mutation could result in weak antibody response in chickens. Considering the field strains of H9N2 with N166D mutation are frequently isolated in the countries with H9N2 vaccination, the findings that the single mutation in HA, N166D, affected both the antigenicity and pathogenesis of H9N2 highlight the significance of surveillance on such mutation that may contribute to the failure of H9N2 vaccination in the field.

Recently, serotype 4 fowl adenovirus (FAdV-4) has spread widely and caused huge economic loss to poultry industry. However, little is known about the molecular pathogenesis of FAdV-4. Fiber protein is thought to be vital for its infection and pathogenesis. Two novel monoclonal antibodies (mAbs) targeting the fiber-1 protein of FAdV-4 were generated, designated as mAb 3B5 and 6H9 respectively. Indirect immunofluorescence assay (IFA) showed that both mAbs only reacted with the FAdV-4 and FAdV-10, not with other serotypes including FAdV-1, FAdV-5, FAdV-6, FAdV-7, FAdV-8 and FAdV-9 tested. Although both mAbs did not recognize the linear epitopes, they could efficiently immunoprecipitate the fiber-1 protein in LMH cells either infected with FAdV-4 or transfected with pcDNA3.1-Fiber-1. Moreover, mAb 3B5 as a capture antibody and HRP-conjugated mAb 6H9 as a detection antibody, a novel sandwich ELISA for efficient detection of FAdV-4 was generated. The limit of detection of the ELISA could reach to 1000 TCID50/ml of FAdV-4 and the ELISA could be efficiently applied to detect FAdV-4 in the clinical samples. The two mAbs specific targeting fiber-1 generated here would pave the way for further studying on the role of fiber-1 in the infection and pathogenesis of FAdV-4, and the established mAb based sandwich ELISA would provide an efficient diagnostics tool for detection of FAdV-4/10.