Dual-subtype FIV vaccine protects cats against in vivo swarms of both homologous and heterologous subtype FIV isolates.
OBJECTIVE
To evaluate the immunogenicity and efficacy of an inactivated dual-subtype feline immunodeficiency virus (FIV) vaccine.


METHODS
Specific-pathogen-free cats were immunized with dual-subtype (subtype A FIV(Pet) and subtype D FIV(Shi)) vaccine and challenged with either in vivo- or in vitro-derived FIV inocula.


METHODS
Dual-subtype vaccinated, single-subtype vaccinated, and placebo-immunized cats were challenged within vivo-derived heterologous subtype B FIV(Bang) [10--100 50% cat infectious doses (CID(50))], in vivo-derived homologous FIV(Shi)(50 CID(50)), and in vitro- and in vivo-derived homologous FIV(Pet)(20--50 CID(50)). Dual-subtype vaccine immunogenicity and efficacy were evaluated and compared to single-subtype strain vaccines. FIV infection was determined using virus isolation and proviral PCR of peripheral blood mononuclear cells and lymphoid tissues.


RESULTS
Four out of five dual-subtype vaccinated cats were protected against low-dose FIV(Bang) (10 CID(50)) and subsequently against in vivo-derived FIV(Pet) (50 CID(50)) challenge, whereas all placebo-immunized cats became infected. Furthermore, dual-subtype vaccine protected two out of five cats against high-dose FIV(Bang) challenge (100 CID(50)) which infected seven out of eight single-subtype vaccinated cats. All dual-subtype vaccinated cats were protected against in vivo-derived FIV(Pet), but only one out of five single-subtype vaccinated cats were protected against in vivo-derived FIV(Pet). Dual-subtype vaccination induced broad-spectrum virus-neutralizing antibodies and FIV-specific interferon-gamma responses along with elevated FIV-specific perforin mRNA levels, suggesting an increase in cytotoxic cell activities.


CONCLUSIONS
Dual-subtype vaccinated cats developed broad-spectrum humoral and cellular immunity which protected cats against in vivo-derived inocula of homologous and heterologous FIV subtypes. Thus, multi-subtype antigen vaccines may be an effective strategy against AIDS viruses.
Pu
R
R
Department of Pathobiology, College of Veterinary Medicine, University of Florida, Gainesville, 32611-0880, USA.
Coleman
J
J
Omori
M
M
Arai
M
M
Hohdatsu
T
T
Huang
C
C
Tanabe
T
T
Yamamoto
J K
JK
D000818:Animals; D001483:Base Sequence; D002415:Cats; D017931:DNA Primers; D016181:Feline Acquired Immunodeficiency Syndrome / Q000276:immunology / Q000517:prevention & control*; D007111:Immunity, Cellular; D016089:Immunodeficiency Virus, Feline / Q000276:immunology*; D007371:Interferon-gamma / Q000096:biosynthesis; D009500:Neutralization Tests; D010919:Placebos; D016133:Polymerase Chain Reaction; D014765:Viral Vaccines / Q000276:immunology*
D017931:DNA Primers; D010919:Placebos; D014765:Viral Vaccines; D007371:Interferon-gamma