Omega Interferon (ω-INF)¹

Virbac Australia has released Virbagen Omega, the first veterinary interferon registered in Australia. It is a recombinant type-1 omega interferon (ω-INF) of feline origin. ω-INF is closely related to human alpha and beta interferons. Like all interferons, it has antiviral, immunomodulatory and antiproliferative properties. Interferons are protein molecules secreted temporarily by almost all cells in response to invasion by a virus, bacteria or tumour cells and play a major role in the host's defence mechanisms. They belong to the cytokine family (like interleukins).

Omega interferon, of feline origin, exerts significant cross-species protection affects when administered to dogs. However, interferon is not virus specific. Interferons produced during a distemper infection in dogs are effective against parvovirus infection, locally and/or after distribution throughout the body.

Mode of action

Interferons bind to specific receptors on the plasma membrane of other cells. The binding activates a complex transcriptional cascade, leading to an upregulation of greater than 20 cellular genes, producing an interferon-activated cell. Interferon-induced proteins are numerous and each protein confers a new property to the cell. This may be antiviral, immune modulating or antiproliferative. Additional to cells producing proteins as a response to interferon, interferon also stimulates leucocytes and there is an increase in cytotoxic activity, natural killer cell activity and oxidase activity by neutrophils. There is an increased antigen presentation by the cell and an increase in apoptosis receptors in the cell membrane. All of these processes induce an antiviral state and result in death of infected cells.

In contrast to antibodies, interferons are secreted transiently in response to virus infections. They are induced by almost any virus, multiplying in almost any cell type, an in any vertebrate species.

Indications

Omega Interferon is currently registered in Australia as an adjunct in the treatment of canine parvovirus and feline calicivirus infections. In laboratory and field use, omega interferon has been shown to reduce the duration and severity of fever and oral ulceration associated with feline calicivirus.

The current registered dose rates in Australia are:

Dogs - 2.5 MU/kg once daily for 3 consecutive days

Cats - registered protocol for caliciviral infection in cats is  1-5 MU/kg once daily every 2nd day for 3 injections; for retroviruses in cats (FeLV and FIV), is 1 MU/kg SQ oid for 5 days, given at Day 0 (on presentation) and repeated again at day 14 and day 60.

Clinical studies have demonstrated its benefits when used in FIV and/or FeLV infected symptomatic cats and has been approved for this indication in Europe. Other areas of interest include FIP, herpetic keratitis, feline chronic gingivostomatitis (lymphocytic plasmacytic stomatitis) and distemper.

1. Vischer, C. (2005) Virbagen Omega: The potential of a veterinary interferon. http://72.14.253.104/search?q=cache:PhMzYVtG2CEJ:www.petdental.com.au/Conference%2520Papers/Virbagen%2520Omega.doc+omega+INTERFERON+cats&hl=en&ct=clnk&cd=9&gl=au