Significantly, these SBA titers were identical to those induced by the N-term His full rMIP (LP). rMIP proteins was compared to that of full (i.e., full-length) rMIP proteins (containing the globular domain) with either an N- or C-terminal His tag and with or without the LP sequence. By comparing the functional murine antibody responses to these various constructs, we determined that C-term His truncated rMIP (LP) delivered in liposomes induced high levels of antibodies that bound to the surface of wild-type Ppia but not mipmutant meningococci and showed bactericidal activity BMS-911543 against homologous type I MIP (median titers of 128 to 256) and heterologous type II and III (median titers of 256 to 512) strains, thereby providing at least 82% serogroup B strain coverage. In contrast, in constructs lacking the LP, placement of the His tag at the N terminus appeared to abrogate bactericidal activity. The strategy used in this study would obviate any potential concerns regarding the use of MIP antigens for inclusion in bacterial vaccines. == INTRODUCTION == Neisseria meningitidis(meningococcus) infections contribute significantly to mortality and morbidity worldwide (1). Implementation of capsular polysaccharide-protein conjugate vaccines against serogroups A, C, Y, and W into the routine immunization schedules of developed countries has been successful (25), but this approach cannot be used for serogroup B strains. The polysaccharide capsule of serogroup B meningococci (MenB) shows structural mimicry of human fetal brain neural cell adhesion molecules (6). Licensed MenB vaccines based on lipooligosaccharide (LOS)-depleted outer membrane (OM) vesicles (V) have been used to control serosubtype strain-specific clonal outbreaks of MenB infection, e.g., in Norway (7), Cuba (8), Brazil (9), and New Zealand (10), but they do not provide cross-strain protection (11). Recently, the 4CMenB (Bexsero) vaccine, developed using a genome-based reverse-vaccinology approach (12), has received a license from the European Union and has been recommended by the Joint Committee for Vaccination and Immunization for the routine vaccination of infants in the United Kingdom since 2014. The vaccine consists of the factor H binding protein (fHbp, fused to GNA2091 carrier protein), neisserial heparin binding protein (NHBA, fused to GNA1030 carrier protein), and an adhesin, NadA, mixed with the MenZB OMV vaccine from the New Zealand MenB outbreak strain (NZ98/254, P1.7-2,4, sequence type 41 [ST-41]/ST-44) (13,14). Another vaccine, bivalent in nature, consists of two recombinant LP2086 (rLP2086) (fHbp) subfamily proteins and is currently in phase III trials. This first generation of MenB vaccines, however, shows incomplete strain coverage of meningococcal strains in the populations examined. For example, it has been predicted using a meningococcal antigen typing system that approximately 73% to 78% of all MenB strains in several European countries would be killed by postvaccination sera induced by the BMS-911543 4CMenB vaccine (15); in Canada, the estimate was only 66% (95% confidence interval [CI], 46% to 78%) (16). Estimating the breadth of strain coverage afforded by the bivalent rLP2086 vaccine is a complex task, but, using a methodology based on a killing assay, it has been reported that for toddlers and adolescents-young adults, protective bactericidal titers ranged from 44% to 100% and from 68% to 98%, respectively, against MenB strains expressing heterologous fHbp proteins (17). In order to develop effective vaccines, it is critical to identify novel conserved antigens capable of inducing cross-protective antibody responses. Many individual OM and secreted proteins have been investigated for their ability to induce serum bactericidal antibodies (SBA) (18), which is a generally accepted laboratory correlate of protection for serogroup B meningococci (19). Proteomic studies carried out in our laboratory identified the high abundance of a 29-kDa meningococcal BMS-911543 MIP protein (the product of gene NMB1567, NEIS1487) in the OM (20). It has been also reported that the gonococcal homologueNeisseria gonorrhoeaemacrophage infectivity potentiator (Ng-MIP) was a surface-exposed lipoprotein inN. gonorrhoeae(21). We showed in a previous study (22) that MIP is highly conserved, and in a collection of well-characterized meningococcal isolates (differing in serogroup, serotype, and serosubtype), isolated from carriers or patients, we found only three distinct MIP sequence types (designated I, II, and III). MIP is.