Humoral and cell-mediated immune responses to various economical regimens of purified Vero cell rabies vaccine.

Purified Vero cell rabies vaccine (PVRV) is a new effective but inexpensive tissue culture rabies vaccine for human use. We investigated if the cost of immunization with PVRV could be further reduced by intradermal immunization. Fifty-eight subjects with low-risk exposure to rabies were randomized into 4 groups to receive full-dose (0.5 ml) intramuscular injection of PVRV on days 0, 3, 7, 14 and 28 or 4, 2 or 1 intradermal injections of PVRV (0.1 ml) on days 0, 3, and 7, followed by another intradermal injection on day 28. Neutralizing antibodies and specific cell-mediated response (CMIR) were sequentially followed up to day 36. The antibody levels in the intradermal groups increased with the number of injection sites and the levels achieved by the 2-site i.d. regimen were not significantly different from those obtained by the full-dose i.m. even though only 1/3 of the amount of PVRV was used. Specific CMIR occurred 1 week sooner in the 2 and 4-site i.d. regimens than the full-dose i.m. We therefore recommended that our 2-site i.d. regimen of PVRV should be further tested with a view to substituting it for the more expensive full-dose i.m. regimen in order to further reduce the cost of rabies prophylaxis particularly in the developing countries.

Effect of inosiplex on the humoral and cell-mediated immune responses to intradermal human diploid cell rabies vaccine.

Antigen-stimulated lymphocyte transformation was studied in recipients of intradermal human diploid cell rabies vaccine (HDCV). HDCV was administered intradermally at 8 different anatomical sites, 0.1 ml each, on day 0; followed by another 4-site injection on day 7. Rabies antigen-stimulated in vitro proliferative response was evident as early as 7 days after starting immunization. It reached a peak on day 14 and had declined by day 28. The cellular proliferative response preceded and roughly correlated with the antirabies antibody response. Simultaneous administration of inosiplex, an antiviral and immunopotentiating drug, during the first 10 days of intradermal HDCV immunization did not result in heightened antibody titres or cell-mediated immune response to the vaccine. The number of T cells and the lymphocyte proliferative response to phytohaemagglutinin in inosiplex-treated vaccinees were similarly not significantly different from untreated controls. Our results confirm other previous findings that a specific cell-mediated immune response can be consistently and rapidly induced by an intradermal regimen of HDCV immunization. The addition of inosiplex to this regimen did not enhance the humoral or cell-mediated immune responses to the vaccine. The apparent lack of immunostimulating effect of inosiplex in this setting may be the result of several factors such as the immunization schedule and the immunologic parameters examined.