Mammals posses both serum
transferrin and
lactoferrin, whose functions are taken over in birds by
ovotransferrin, displaying both
iron transport and antibacterial activities.
Ovotransferrin also exerts
antiviral activity towards
Marek's disease virus, an avian member of the herpes family of viruses. This virus infects lymphoid organs and induces the transcription of
ovotransferrin in infected chicken embryo fibroblasts. However, it has not yet been established whether
ovotransferrin gene transcription is linked to the release of the
protein outside the cells or whether
ovotransferrin expression and release also occurs in chicken lymphoblastoid cells in which the
Marek's disease viral genome is integrated. Our results indicate that both serum and egg-white
isoforms of
ovotransferrin are expressed and released in the supernatants of chicken embryo fibroblast and lymphoblastoid cells in the absence of
infection.
Viral infection of chicken embryo fibroblasts caused a slight increase of
ovotransferrin release, whereas viral
reinfection of lymphoblastoid cells caused a remarkable
ovotransferrin release in a virus concentration-dependent manner. These findings suggest that
ovotransferrin release in vivo may play a crucial role in protecting the whole organism from
viral infection spreading, and support the hypothesis that the
antiviral activity of
ovotransferrin is an important part of the innate immune response in birds, resembling the
antiviral activity of
lactoferrin in mammals.