Chicken anaemia virus (CAV), a member of the genus Gyrovirus, is the etiological agent of chicken infectious anaemia. CAV infects bone marrow-derived cells, resulting in severe anaemia and immunosuppression in young chickens and a compromised immune response in older birds. We investigated the molecular epidemiology of CAV in sick chickens in China from 2014 to 2015 and showed that the CAV-positive rate was 13.30%, in which mixed infection (55.56%) was the main type of infection. We isolated and identified 15 new CAV strains using different methods including indirect immunofluorescence assay and Western Blotting. We used overlapping polymerase chain reaction to map the whole genome of the strains. Phylogenetic analyses of the obtained sequences and related sequences available in GenBank generated four distinct groups (A–D). We built phylogenetic trees using predicted viral protein (VP) sequences. Unlike CAV VP2s and VP3s that were well conserved, the diversity of VP1s indicated that the new strains were virulent. Our epidemiological study provided new insights into the prevalence of CAV in clinical settings in recent years in China.

The most common method for establishing bioequivalence (BE) is to demonstrate similarity of concentration–time profiles in the systemic circulation, as a surrogate to the site of action. However, similarity of profiles from two formulations in the systemic circulation does not imply similarity in the gastrointestinal tract (GIT) nor local BE. We have explored the concordance of BE conclusions for a set of hypothetical formulations based on budesonide concentration profiles in various segments of gut vs. those in systemic circulation using virtual trials powered by physiologically based pharmacokinetic (PBPK) models. The impact of Crohn’s disease on the BE conclusions was explored by changing physiological and biological GIT attributes. Substantial ‘discordance’ between local and systemic outcomes of VBE was observed. Upper GIT segments were much more sensitive to formulation changes than systemic circulation, where the latter led to false conclusions for BE. The ileum and colon showed a lower frequency of discordance. In the case of Crohn’s disease, a product-specific similarity factor might be needed for products such as Entocort^® EC to ensure local BE. Our results are specific to budesonide, but we demonstrate potential discordances between the local gut vs. systemic BE for the first time.

The most common method for establishing bioequivalence (BE) is to demonstrate similarity of concentration-time profiles in the systemic circulation, as a surrogate to the site of action. However, the similarity, or otherwise, of profiles from two different formulation in the gastrointestinal tract (GIT) may not be associated with same conclusions based on systemic circulation. Here, we have explored the concordance of BE conclusions (or otherwise) for a set of hypothetical formulations based on drug concentration-profiles in various segments of gut vs those in systemic circulation using virtual trials powered by physiologically-based (PBPK) models. Moreover, by changing physiological and biological attributes of the GIT, the impact of Crohn’s Disease on the BE conclusions was explored. The virtual BE (VBE) was applied to an Entocort EC, a pH/time-dependent release formulation of budesonide, as model drug that is targeted at ileum and colon. Substantial “discordance” between the local and systemic outcomes of VBE was observed. Upper GIT segments were much more sensitive to formulation changes than systemic circulation, where the latter led to false conclusions for BE. The ileum and colon showed a lower frequency of discordance with systemic-derived VBE. Nonetheless, a higher f2 value than the default similarity standard (50) was required to achieve local BE. In the case of Crohn’s Disease, a product-specific f2 value might be needed for drugs such as Entocort EC to ensure local BE, knowing the insensitivity of systemic data to show lack of BE. The results, being limited to the single model drug product, Entocort EC, may not provide a a general and conclusive picture. However, for the first time, it demonstrated the potential discordances between the local gut vs systemic BE.