VACCINE-ASSOCIATED FELINE SARCOMAS: INVESTIGATION OF POTENTIAL VIRAL ETIOLOGIES

B. Kidney, D. Haines, J. Ellis and M. Jackson.  Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada

            The pathogenesis of vaccine-associated feline sarcomas (VAFS) remains obscure.  The low prevalence of VAFS suggests that congenital or acquired genetic factors within individual susceptible cats may act as initiators of oncogenesis. 
The purpose of our study was to investigate retroviral and DNA tumor viral candidates in the etiology of VAFS.  The retroviruses investigated included feline immunodeficiency virus (FIV), feline foamy virus (FEFV) and endogenous feline leukemia virus (enFeLV).  Vaccination could increase replication and/or expression of latent retroviruses or endogenous retroviruses within proliferating fibroblasts and/or inflammatory cells.  Malignant transformation could then result from insertional activation or inactivation of cellular genes. The specific DNA tumor viruses evaluated included papillomavirus, herpesvirus and polyomavirus.  Members of these three viral families have oncogenic potential and could be introduced either as vaccine contaminants or as skin contaminants transported to the subcutis by vaccination.  Also, non-pathogenic or latent viruses pre-existing in host tissues could become oncogenic within the local milieu created by vaccination.  Fifty formalin-fixed, paraffin-embedded  VAFS were negative for the five viruses, for which they were evaluated, using polymerase chain reaction (PCR) and/or immunohistochemistry.  The level of enFeLV RNA in VAFS was not significantly different compared to that in non-vaccine site associated feline fibrosarcomas using  semi-quantitative reverse transcriptase PCR.   
We concluded that the retroviruses, including FIV, FEFV and enFeLV, and the DNA tumor viruses, specifically papillomavirus, polyomavirus and herpesvirus do not appear to be directly involved in the pathogenesis of VAFS.

Dr. Beverly Kidney
Department of Veterinary Pathology
Western College of Veterinary Medicine
University of Saskatchewan
Saskatoon, SK
Canada

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