FeLV-infection: problems and prospects of vaccine prevention and interferon-therapy of feline leukemia

Abstract

Here, we review an overall effectiveness of interferon-based preparations and interferon biosynthesis inducers for treatment of feline leukemia, as well as development of methodological approaches to improve efficacy of interferon therapy. Feline leukemia is a systemic hematopoietic malignancy caused by a single-stranded RNA retrovirus called Feline Leukemia Virus (FeLV) that leads to lethal outcome within about 3 years after the onset. FelV is widely distributed in population of domestic cats worldwide, being often detected in the blood of wild cats, including those of rare and endangered species. In some regions, FeLV prevalence may be high not only among domestic cats, but among wild as well. Currently, there are several commercially available vaccines to protect cats from FeLV infection (e.g., inactivated whole-virion vaccines such as Nobivac adjuvanted Feline 2-FeLV, two-adjuvant subunit vaccine FeLV-derived protein antigens as well as non-adjuvanted vector DNA vaccine). However, none of such vaccines provides durable protection. In addition, vaccination of cats against FeLV is often associated with development of diverse inflammatory, allergic and shock complications, and highly serious side effects such as developing vaccine-associated sarcoma at the injection site that some researchers connect with use of adjuvants like aluminum salts etc. We briefly describe FeLV virus, pathogenetic parametersassociated with FeLV infection as well as current technologies for preventing and treating feline leukemia. A historic background and current state of interferon therapy for FeLV infection as well as associated neoplastic processes in domestic cats and some wild species are evaluated. Possible interventions aimed at improving efficiency of interferon therapy of feline leukemia based on using new recombinant interferon preparations of various types and subtypes, as well as interferon inducers are discussed. In conclusion, it is noted that another interesting and potentially highly promising option in defining strategy of biotherapy associated with modulating IFN system in FeLV-infected animals might be to use of synthetic inducers triggering endogenous IFN production.