Modulation of the immune response of Balb/c mice against Leishmania major by Imuvert

This study investigated the effect of Imuvert, a biological response modifier derived from Serratia marcescens, on the progression of Leishmania major infection in Balb/c mice. A single 100 mu g Imuvert injection was significantly protective in Balb/c mice when challenged 28 days later in the footpad with 5 x 10(5) stationary phase L. major promastigotes. Intraperitoneal (i.p.) and intravenous (i.v.) immunization of mice with heat-killed stationary phase L. major promastigotes significantly reduced lesion development following challenge with L. major promastigotes. Subcutaneous (s.c.) immunization had no protective effect. A single 100 mu g Imuvert injection significantly reduced lesion development in s.c. immunized mice, but had a lesser effect in mice immunized by i.p. and i.v. routes. Balb/c mice receiving four Imuvert injections 14, 7, 2 and 1 day prior to footpad challenge with L. major promastigotes were not protected, but rather displayed significant exacerbation of infection. Our results suggest the possibility that Imuvert could be useful in stimulating a protective response against L. major when given along with s.c. vaccine, a realistic route for vaccinating humans in contrast to either i.v. or i.p. routes. Since the protective response in Balb/c mice against L. major is dependent on the stimulation of T-h1 cells, it is suggested that the observed adjuvant effect of Imuvert given with s.c. vaccine perhaps is due to changes in immunological responses in such a direction. (C) 1998 Published by Elsevier Science Ltd on behalf of the International Society for Immunopharmacology.