The difference in CD4 T cell immunity between high- and low-virulence Tembusu viruses is mainly related to residues 151 and 304 in the envelope protein.

Tembusu virus (TMUV) can result in a severe disease affecting domestic ducks. The role of T cells in protection from TMUV infection and the molecular basis of T cell-mediated protection against TMUV remain largely uncharacterized. Here, we used the high-virulence TMUV strain Y and the low-virulence TMUV strain PS to investigate the protective role for TMUV-specific CD4 and CD8 T cells.

An Antibody Neutralization Determinant on Domain III and the First α-Helical Domain in the Stem-Anchor Region of Tembusu Virus Envelope Protein.

Previous studies identified three neutralizing epitopes on domains I, II, and III of the Tembusu virus (TMUV) envelope (E). More evidence is needed to understand the molecular basis of Ab-mediated neutralization and protection against TMUV. In this study, we observed a neutralizing mAb, 6C8, that neutralized TMUV infection primarily by inhibiting cell attachment.

Antibody prophylaxis against Tembusu virus-associated disease.

Earlier studies have shown that Tembusu virus (TMUV) can elicit high levels of neutralizing antibodies, but the ability of antibodies to protect against TMUV-associated disease and to inhibit replication of TMUV in vivo remains to be investigated. Here, we tested the prophylactic efficacy of TMUV immune serum directly using a 2-day-old Pekin duck model. Passive administration of the immune serum prior to challenge protected ducklings against morbidity and mortality, substantially reduced TMUV-caused tissue injury, and significantly decreased TMUV levels in the periphery and central nervous system.

A quasispecies in a BHK-21 cell-derived virulent Tembusu virus strain contains three groups of variants with distinct virulence phenotypes.

Previous studies resulted in the isolation of a low-virulence plaque-purified variant from the third passage (P3) in BHK-21 cells of a Tembusu virus (TMUV) isolate, suggesting the presence of viral quasispecies in the P3 culture. To confirm this notion, the fourth passage virus (P4) was prepared by infecting BHK-21 cells with P3 for isolation of more variants. We isolated 10 plaque-purified viruses.

Mapping of a unique epitope on domain III of the envelope protein of Tembusu virus.

We recently developed a Tembusu virus (TMUV)-specific monoclonal antibody (MAb) 12F11, which was found to recognize a long amino acid sequence between residues 8 and 77 of domain III of the envelope protein (EDIII). Here, the epitope recognized by MAb 12F11 was mapped using alanine substitutions combined with dissociation constant analysis. The findings, and prediction of tertiary structure of TMUV EDIII, showed that the MAb 12F11 epitope contained one critical residue and 13 peripheral residues.

Substantial Attenuation of Virulence of Tembusu Virus Strain PS Is Determined by an Arginine at Residue 304 of the Envelope Protein.

The Tembusu virus (TMUV) PS strain, derived by several passages and plaque purifications in BHK-21 cells, displays markedly lower virulence in Pekin ducklings relative to a natural isolate of TMUV, but the potential virulence determinants and the mechanisms for substantial virulence attenuation of the passage variant remain unknown. Here, we constructed a series of chimeric and mutant viruses and assessed their virulence using a 2-day-old Pekin duckling model. We showed that residue 304 in the envelope (E) protein is the molecular determinant of TMUV virulence.

The Neutralizing Antibody Response Elicited by Tembusu Virus Is Affected Dramatically by a Single Mutation in the Stem Region of the Envelope Protein.

Tembusu virus (TMUV) is a mosquito-borne flavivirus that most commonly affects adult breeder and layer ducks. However, a TMUV-caused neurological disease has also been found in ducklings below 7 weeks of age, highlighting the need to develop a safe vaccine for young ducklings. In this study, a plaque-purified PS TMUV strain was attenuated by serial passage in BHK-21 cells.

Pathogenicity of a Jinding duck-origin cluster 2.1 isolate of Tembusu virus in 3-week-old Pekin ducklings.

Tembusu virus (TMUV) infection most commonly affects breeder and layer ducks during laying period, and can also affect young ducks below 7 weeks of age. Here, we report our investigation of a TMUV-caused fatal disease of Jingding ducklings (Anas platyrhynchos domesticus) in Northeast China. The disease resulted in mortalities of up to 40 % in 2 to 4-week-old ducks, up to 25 % in 5 to 6-week-old ducks, and less than 10 % in 7 to 8-week-old ducks.

Molecular evidence of goose-parvovirus-related abnormal molting in Pekin ducks.

Since January 2019, abnormal molting has been observed frequently in approximately 40-day-old Pekin ducks in China. To investigate the possible involvement of a virus, we tested the prevalence of duck circovirus (DuCV), goose hemorrhagic polyomavirus (GHPyV), and goose parvovirus (GPV) in 11 molt cases in two provinces. GPV was detected in all cases, particularly in all samples collected from the feather area.

A highly divergent hepacivirus-like flavivirus in domestic ducks.

Using random amplification and reverse transcription-PCR, a novel RNA virus was detected in sera of domestic ducks. The full genome of the virus was determined for three strains, identifying the first hepacivirus-like flavivirus in birds. The virus, that we tentatively named duck hepacivirus-like virus (DuHV), possesses several unique molecular features, such as possession of the largest hepacivirus-like polyprotein gene and a Pegivirus A-like internal ribosome entry site.