Kinetics of replication of a partially attenuated virus and of the challenge virus during a three-year intersubtype feline immunodeficiency virus superinfection experiment in cats.
The effects of preinfecting cats with a partially attenuated feline immunodeficiency virus (FIV) on subsequent infection with a fully virulent FIV belonging to a different subtype were investigated. Eight specific-pathogen-free cats were preinfected with graded doses of a long-term in vitro-cultured cell-free preparation of FIV Petaluma (FIV-P, subtype A). FIV-P established a low-grade or a silent infection in the inoculated animals. Seven months later, the eight preinfected cats and two uninfected cats were challenged with in vivo-grown FIV-M2 (subtype B) and periodically monitored for immunological and virological status. FIV-P-preinfected cats were not protected from acute infection by FIV-M2, and the sustained replication of this virus was accompanied by a reduction of FIV-P viral loads in the peripheral blood mononuclear cells and plasma. However, from 2 years postchallenge (p.c.) until 3 years p.c., when the experiment was terminated, preinfected cats exhibited reduced total viral burdens, and some also exhibited a diminished decline of circulating CD4(+) T lymphocytes relative to control cats infected with FIV-M2 alone. Interestingly, most of the virus detected in challenged cats at late times p.c. was of FIV-P origin, indicating that the preinfecting, attenuated virus had become largely predominant. By the end of follow-up, two challenged cats had no FIV-M2 detectable in the tissues examined. The possible mechanisms underlying the interplay between the two viral populations are discussed.
Pistello
M
M
Retrovirus Center and Virology Section, Department of Biomedicine, University of Pisa, Pisa, Italy.
Matteucci
D
D
Cammarota
G
G
Mazzetti
P
P
Giannecchini
S
S
Del Mauro
D
D
Macchi
S
S
Zaccaro
L
L
Bendinelli
M
M
D000818:Animals; D000914:Antibodies, Viral / Q000276:immunology; D018791:CD4 Lymphocyte Count; D002415:Cats; D005260:Female; D016089:Immunodeficiency Virus, Feline / Q000276:immunology / Q000502:physiology*; D007700:Kinetics; D016180:Lentivirus Infections / Q000276:immunology / Q000821:virology*; D007963:Leukocytes, Mononuclear / Q000821:virology; D011533:Proviruses; D019562:Viral Load; D014779:Virus Replication
D000914:Antibodies, Viral