This study investigated the safety, efficacy, and clearance of SAG-2. an at
tentuated rabies virus, after oral vaccination in dogs. Nineteen dogs consu
med baits containing lyophilized vaccine, but residual SAG-2 virus was reco
vered in only one of 57 oral swabs, collected one hour post-vaccination. Se
ven vaccinates were euthanized between 24 and 96 h after consuming a bait.
Rabies virus RNA was detected in tonsils from all seven dogs by nested RT-P
CR, with primers to the viral glycoprotein. Genomic, sense-transcripts. and
m-RNAs were detected in five of seven tonsil samples using primers to the
rabies virus nucleoprotein gene, as well as in four of seven samples from t
he buccal mucosa and one of seven from the tongue. Rabies virus antigen was
detected in all tonsils by an immunohistochemistry test, confirming the RT
-PCR results. In addition, virus was isolated from one tonsil sample collec
ted at 96 h. providing supportive evidence of viral replication. Ten of 12
(83%) of the vaccinated dogs demonstrated an anamnestic response, with vira
l neutralizing antibody titers (greater than or equal to 0.5 IU/ml), after
rabies virus challenge. These ten dogs survived., whereas all control dogs
succumbed to rabies. Attenuated rabies viruses, such as SAG-2. replicate in
local tissues of the oral cavity and can be cleared relatively quickly, wi
thout viral excretion, leading to protective immunity against the disease.
Published by Elsevier Science Ltd.