Cytopathic feline leukemia viruses cause apoptosis in hemolymphatic cells.
Certain isolates of the oncoretrovirus feline leukemia virus (FeLV) are strongly cytopathic for hemolymphatic cells. A major cytopathicity determinant is encoded by the SU envelope glucoprotein gp70. Isolates with subgroup C SU gp70 genes specifically induce apoptosis in hemolymphatic cells but not fibroblasts. In vitro exposure of feline T-cells to FeLV-C leads first to productive viral replication, next to virus-induced cell agglutination, and lastly to apogenesis. This in vitro phenomenon may explain the severe progressive thymic atrophy and erythroid aplasia which follow viremic FeLV-C infection in vivo. Inappropriate apoptosis induction has also been hypothesized to explain the severe thymico-lymphoid atrophy and progressive immune deterioration associated with isolates of FeLV containing variant envelope genes. The influence of envelope hypervariability (variable regions 1 [Vr1] and 5 [Vr5] on virus tropism, viremia induction, neutralizing antibody development and cytopathicity is discussed. Certain potentially cytopathic elements in FeLV SU gp70 Vr5 may derive from replication-defective, poorly expressed, endogenous FeLVs. Other more highly conserved regions in FeLV TM envelope p15E may also influence apoptosis induction.
Rojko
J L
JL
Department of Veterinary Pathobiology, Ohio State University, Columbus 43210, USA.
Hartke
J R
JR
Cheney
C M
CM
Phipps
A J
AJ
Neil
J C
JC
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D002415:Cats; D003588:Cytopathogenic Effect, Viral; D005256:Leukemia Virus, Feline / Q000472:pathogenicity*; D008214:Lymphocytes / Q000473:pathology / Q000821:virology*; D008969:Molecular Sequence Data; D012192:Retroviridae Infections / Q000473:pathology*; D017386:Sequence Homology, Amino Acid; D014412:Tumor Virus Infections / Q000473:pathology*