Acute virulent infection with feline immunodeficiency virus (FIV) results in lymphomagenesis via an indirect mechanism

Four cats (24%) experimentally infected with FIV unexpectedly developed neoplastic changes within four months of inoculation. While FIV has previously been associated with neoplasia, the rapidity and high attack rate seen here is highly unusual. PCR for antigen receptor rearrangements (PARR) detected clonally rearranged T cells in two animals diagnosed with B cell follicular lymphoma by classical means. All cats were negative for feline leukemia virus; gamma-herpesvirus DNA was not amplified using degenerate primers. FIV proviral load in neoplastic tissue was two orders of magnitude lower than in the periphery, lower in neoplastic vs non-neoplastic lymph node, and clonal integration was not detected. We hypothesize that neoplasia was secondary to FIV immune dysregulation, and show that PARR can augment our capacity to phenotype these tumors and distinguish follicular hyperplasia from lymphoma. Age of exposure and relative virulence of the inoculum likely contributed to this unusual presentation of FIV infection.

► Neoplastic changes were identified in four of seventeen SPF cats infected with FIV.
► No confounding infectious etiologies were identified.
► Clonal integration of FIV was not detected via Southern blot.
► Low proviral burden was identified in the tumor tissue.
► Results suggest an indirect mechanism of tumorigenesis.