Virus serological diagnosis in two avian species based on binding of human C1q to avian antibody

Diagnosis of infectious diseases in birds using direct assays such as conventional ELISA or immunofluorescence require antibody directed to IgG of each avian species. In this study, we tested binding of human C1q to different antigen-antibody complexes of two avian species in a sandwich immunofluorescent complement fixation test (S-ICFT). The reaction was as follows: virus (in cells) + decomplemented avian serum + human-C1q + goat anti-human-C1q + fluorescein isothiocyanate rabbit anti-goat-IgG. Positive and negative chicken (order Galliformes) sera against chicken anaemia virus (CAV) and sera against avian pox virus as well as positive and negative sera against chicken pox virus raised in a milvago chimango (order Falconiformes) were used. Positive sera of either avian species demonstrated clear fluorescent staining of infected cells while negative sera did not show any reaction. This demonstrated that both chicken and milvago chimango antibodies were able to bind human C1q. Since both avian species tested belonged to different orders, we believe that antibodies of other avian species will also bind human C1q allowing serological surveys in feral birds through S-ICF