Infectious Causes of Neoplasia in the Domestic Cat

Abstract

In recent years, growing attention has been paid to the influence/role of infectious diseases in tumour development and progression. Investigations have demonstrated that some infectious organisms can have a direct role in the development of neoplasia, whereas others can predispose to neoplasia by alterations in the immune response, or by creating a pro-inflammatory environment. Feline leukaemia virus was one of the first infectious agents recognised as an oncogenic organism, and along with feline immunodeficiency virus has received the most attention. Since the discovery of this retrovirus, several other organisms have been associated with neoplastic processes in cats, these include gammaherpes virus, mouse mammary tumour virus, papillomaviruses, hepadnavirus, Helicobacter species, and the parasitic infections Platynosomum fastosum and Opisthorchis viverrini. This review summarises the findings to date.

Exploring the link between viruses and cancer in companion animals: a comprehensive and comparative analysis

“…The two copies of single-stranded RNA released in the host cell cytoplasm are reverse transcribed into DNA by reverse transcriptase. The viral DNA enters the nucleus and integrates into the host cell DNA, acting as a template for the production of new viral particles [ 32 ].…”

“…The outcome of infection may be variable, depending on a number of factors, like immune status and age of the host, concentration and pathogenicity of the virus, route of exposure, and the presence of concomitant diseases [ 21 , 31 , 37 ]. If the immune system is able to contain viral spread through an appropriate immune response, cats may recover from infection, being known as “regressor subjects” [ 21 , 32 , 38 ]. This event, in natural circumstances, takes place in 1% up to 10% of exposed cats [ 23 ].…”

“…The virus integrates its genome in haemopoietic precursor cells, and the progeny cells released will all be infected, with the development of high-level viremia [ 37 ]. A number of subjects recover from viremia, but remain “latently infected” because of the persisting integration of the virus in bone marrow stem cell genome, while those who do not recover remain “persistently infected” [ 32 ].…”

“…FeLV-associated diseases are not only lymphoma and leukemia, as suggested by the name of the virus, but they also include non-neoplastic diseases related to its pancytotropism and to the involvement of bone marrow, lymphoid system and rapidly dividing cells. Among these diseases, myeloproliferative and immune-mediated diseases, cytopenia (particularly anemia), enteritis, and reproductive disorders can be found, along with secondary infections due to immunosuppression [ 23 , 31 , 32 , 43 , 44 ]…”

“…In this eventuality, the oncogene will be transduced along with the viral genome [ 23 , 61 ]. This mechanism is exploited by the FeLV-A subtype when it acquires cellular oncogenes like fes, fms, fgr, abi, and kit through transduction, giving rise to the so-called feline sarcoma viruses (FeSV), responsible of multicentric sarcomas [ 32 , 66 , 67 ]. FeSV belongs to the group of sarcoma viruses, recombinant viruses coming from the assembling of some leukemia virus genes and some host cell genes that Hardy, in 1981, defined as sarc [ 66 ].…”