SHORT-DURATION OF NEUTRALIZING ANTIBODY-TITERS AFTER PREEXPOSURE RABIES VACCINATION WITH SUCKLING MOUSE-BRAIN VACCINE

The human anti-rabies pre-exposure treatment currently used in Brazil, employing a 1-ml dose of suckling mouse brain vaccine (SMBV) administ ered on days 0, 2, 4 and 28, was compared to an alternative treatment with two 1 ml-doses on day 0, and one 1 ml-dose injected on days 7 and 21. The latter induced higher virus-neutralizing antibody (VNA) titer s on day 21. Both Brazilian rabies vaccines produced with PV or CVS ra bies virus strains were tested. Two additional volunteer vaccinee grou ps, receiving the pre-exposure and the abbreviated postexposure schedu les recommended by the WHO using cell-culture vaccine (CCV) produced w ith PM rabies virus strain, were included as reference. The VNA were m easured against both PV and CVS strains on days 21, 42 and 180 by the cell-culture neutralization microtest. The PV-SMBV elicited higher ser oconversion rates and VNA by day 21 than the CVS-SMBV. Both, however, failed to induce a long-term immunity, since VNA titers were <0.5 IU/m l on bay 180, regardless of the schedule used. Cell-culture vaccine al ways elicited very high VNA on all days of collection. When serum samp les from people receiving mouse brain tissue were titrated against the PV and CVS strains, the VNA obtained were similar, regardless of the vaccinal strain and the virus used in the neutralization test. These r esults contrast with those obtained with sera from people receiving PM -CCV, whose VNA were significantly higher when tested against the CVS strain.