Protection of neonatal kittens against feline immunodeficiency virus infection with passive maternal antiviral antibodies.

OBJECTIVE: Maternal antibodies from either vaccinated or feline immunodeficiency virus (FIV)-infected female cats (queens) were evaluated for their ability to protect kittens against homologous FIV infection.
DESIGN: Kittens that received different levels of maternal antiviral antibodies from either vaccinated or infected queens were inoculated with homologous FIV at 1 week post-parturition and monitored for FIV infection. Maternal antiviral antibodies in the kittens were also measured and compared to the level of FIV infection.
METHODS: Kittens at 1 week post-parturition were inoculated intraperitoneally with five median cat infectious doses of FIVPet. FIV infection was monitored by virus isolation for infectious FIV and by nested polymerase chain reaction for proviral DNA. Virus-neutralizing (VN) antibodies and antibodies to FIV transmembrane peptide and core protein were also monitored throughout the 25 weeks.
RESULTS: Neonatal kittens that received high levels of antiviral antibodies from either vaccinated or infected queens were protected from FIV inoculation. Kittens that received low levels of maternal antiviral antibodies were not completely protected from similar FIV inoculation. Protection correlated more closely with the level of maternal VN antibodies than the anti-p25 antibodies transferred to the kittens. The unprotected kittens born to infected queens were not infected from vertical transmission because all littermates that were not FIV-inoculated remained free of FIV infection.
CONCLUSIONS: Maternal antiviral antibodies, including VN antibodies, from either vaccinated or infected queens protected neonatal kittens from FIV inoculation. Thus, maternal antiviral antibodies play a key role in preventing or limiting infection in neonates and such antiviral immunity can be provided by vaccinated queens.