Comparison of visual microscopic and computer-automated fluorescence detection of rabies virus neutralizing antibodies.

The rapid fluorescent focus inhibition test (RFFIT) and the fluorescent antibody virus neutralization test (FAVNT) are both diagnostic tests for determining levels of rabies neutralizing antibodies. An automated method for determining fluorescence has been implemented to reduce the work time required for fluorescent visual microscopic observations. The automated method offers several advantages over conventional visual observation, such as the ability to rapidly test many samples. The antibody titers obtained with automated techniques were similar to those obtained with both the RFFIT (n = 165, r = 0.93, P < 0.001) and the FAVNT (n = 52, r = 0.99, P < 0.001).

Experimental rabies infection and oral vaccination in vampire bats (Desmodus rotundus).

A rabies virus variant isolated from a vampire bat (Desmodus rotundus) and characterized by genome sequencing was used for the standardization of an experimental infection in this species. The parenteral administration of 10(6) MICLD50 of this variant was capable of inducing death from rabies in 89% of animals. The mean duration of post-challenge survival was 12 days. None of the experimental rabid vampire bats showed aggressive behaviour. A vaccinia-rabies glycoprotein recombinant virus vaccine was administered orally to vampire bats on days -120, -90, -30 or -18 pre-challenge, on the same day of challenge, or on day +5 post-challenge. A significant protection was noticed only in animals vaccinated on days -18 or -30 pre-challenge. A longer period of incubation was observed in animals vaccinated 5 days post-challenge.

Primary multiplication site of the vaccinia-rabies glycoprotein recombinant virus administered to foxes by the oral route.

The primary multiplication site of VVTGgRAB, a recombinant vaccinia virus (VV) expressing the rabies virus G glycoprotein, was studied in comparison with that of the parental VV Copenhagen strain, after oral administration to foxes. Foxes were fed with 10(8) TCID50 of either VVTGgRAB or VV and were sacrificed 12, 24, 48 or 96 h after inoculation. Both viruses were detected by viral isolation in the tonsils during the first 48 h after inoculation at titres between 10(2) and 10(4.3) TCID50/ml. Indirect immunofluorescence confirmed the presence of the virus in tonsils of some of the foxes. The polymerase chain reaction allowed the detection of VVTGgRAB in the tonsils of both of two foxes tested after 24 h, three of three foxes after 48 h, in the buccal mucosa of one of two foxes tested after 24 h and two of three foxes after 48 h and in the soft palate of one of two foxes tested after 24 h and one of three foxes after 48 h. VV was detected in the tonsils of one fox tested after 48 h, in the buccal mucosa of another fox tested after 24 h, and in the first fox after 48 h by the same reaction. Foxes were inoculated with virus isolated from fox tonsils 24 h after oral administration (with or without cell culture amplification) to perform back passages. No virus could be isolated in either case after this passage. The innocuity of VVTGgRAB was also demonstrated when foxes were inoculated with passaged virus.