No abstract

The avian adeno-associated virus (AAAV) has been proved to be an efficient gene transfer vector for human gene therapy and vaccine research. In this experiment, an AAAV-based vaccine was evaluated for the development of a vaccine against duck hepatitis a virus type 1 (DHAV-1). The major capsid VP1 gene was amplified and subcloned into pFBGFP containing the inverted terminal repeats of AAAV, and then the recombinant baculovirus rBac-VP1 was generated. The recombinant AAAV expressing the VP1 protein (rAAAV-VP1) was produced by co-infecting Sf9 cells with rBac-VP1 and the other 2 baculoviruses containing AAAV functional genes and structural genes respectively, and confirmed by electron microscopy, Western blotting and immunofluorescence assays. Quantitative real-time PCR revealed that the titer of rAAAV-VP1 was about 9 × 1012 VG/mL. Immunogenicity was studied in ducklings. One day ducklings were injected intramuscularly once with rAAAV-VP1. Serum from rAAAV-VP1-vaccinated ducklings showed a systemic immune response evidenced by VP1-specific enzyme-linked immunosorbent assay and virus neutralization test. Furthermore, all ducklings inoculated with rAAAV-VP1 were protected against DHAV-1 challenge. The data of quantitative real-time RT-PCR from livers of challenged ducklings also showed that the level of virus copies in rAAAV-VP1 group was significantly lower than that of the PBS group. Collectively, these results demonstrate that the AAAV-based vaccine is a potential vaccine candidate for the control of duck viral hepatitis.

The effects of standard cow, goat and lactose-free cow milk powder on lactose intolerance symptoms and the nutritional status of dogs was studied. Forty adult Springer Spaniels with lactose intolerance were randomly allocated into four groups with ten dogs each and fed one of the milk powders or water for 21 d. The milk powders were reconstituted daily by diluting 10 g milk powder to 60 g water and 2 g milk powder/kg body weight was provided ad libitum and refusals were monitored daily. Lactose intolerance was assessed by faecal composition and pH, water and lactose contents. Biochemical markers for nutritional status were analysed. Feeding intolerance and lactose in faecal samples were observed in dogs fed the standard cow and goat milk powder, but not for the lactose-free milk powder or control groups. The high- and low-density lipoprotein cholesterol increased in all milk powder groups, while there were no other differences in nutritional status measurement. The results suggested that feeding lactose-free milk powder to dogs with lactose intolerance reduced the occurrence of symptoms, thereby enhancing the health and wellbeing of dogs.