THE HYPERFERREMIC MOUSE MODEL FOR THE EVALUATION OF THE EFFECTIVENESSOF VA-MENGOC-BC(R) AGAINST NEISSERIA-MENINGITIDIS-B CLINICAL ISOLATES

VA-MENGOC-BC(R) Is a vaccine against B and C serogroups of Neisseria m eningitidis. Its effectiveness at population level has been shown afte r the application of the vaccine in Cuba, Brazil, Argentina and Colomb ia. In vitro assays are not always able to reproduce the microorganism -host relationships and this makes it necessary to compile and standar dize results obtained in animal models to extrapolate them with a grea ter degree of safety for humans. We evaluated the effectiveness of VA- MENGOC-BC(R) against Neisseria meningitidis group B isolates from clin ically ill patients in Latin America (Argentina, B not typeable: P1; C hile, not typed; Colombia, B4:P1.15 and Cuba B4:P1.15) using Balb/cJ m ice treated with iron to make them susceptible to Neisseria meningitid is. The lethal median dose of each strain and of two others that were not included in challenge assays (Brazil: P1.15 and Argentina, B2b:P1. 10) were determined. Results were 2.68 x 10(6), 3.16 x 10(7), 1.98 x 1 0(8), 1.28 x 10(9), 6.42 x 10(6) and 3.88 x 10(7) colony forming units (CFU), respectively. Nonimmunized animals and mice treated with one a nd two doses of VA-MENGOC-BC(R) were challenged with 10(8-10) CFU. Pro tection ranged from 30 to 100% with one dose and was equal to or highe r than 70% with the two-dose immunization schedule. A significant prot ection could not be observed against the Colombian isolate from the le thality point of view, but the mean time of survival lengthened in imm unized animals in relation to the controls. The applied inoculum of th is strain was much higher (505 x LD(50)) than the remaining ones. The protection conferred was evident; nevertheless, more data are needed t o determine how relevant the results are to humans.