Abstract
Lyme disease, Borrelia burgdorferi-caused infection, if not recognized and appropriately treated by antibiotics, may lead to chronic complications, thus stressing the need for protective vaccine development. The immune protection is mediated by phagocytic cells and by Borrelia-specific complement-activating antibodies, associated with the Th1 immune response. Surface antigen OspC is involved in Borrelia spreading through the host body. Previously we reported that recombinant histidine tagged (His-tag) OspC (rOspC) could be attached onto liposome surfaces by metallochelation. Here we report that levels of OspC-specific antibodies vary substantially depending upon whether rOspC possesses an N' or C' terminal His-tag. This is the case in mice immunized: (a) with rOspC proteoliposomes containing adjuvants MPLA or non-pyrogenic MDP analogue MT06; (b) with free rOspC and Montanide PET GEL A; (c) with free rOspC and alum; or (d) with adjuvant-free rOspC. Stronger responses are noted with all N'-terminal His-tag rOspC formulations. OspC-specific Th1-type antibodies predominate post-immunization with rOspC proteoliposomes formulated with MPLA or MT06 adjuvants. Further analyses confirmed that the structural features of soluble N' and C' terminal His-tag rOspC and respective rOspC proteoliposomes are similar including their thermal stabilities at physiological temperatures. On the other hand, a change in the position of the rOspC His-tag from N' to C' terminal appears to affect substantially the immunogenicity of rOspC arguably due to steric hindrance of OspC epitopes by the C' terminal His-tag itself and not due to differences in overall conformations induced by changes in the His-tag position in rOspC variants.
Highlights
Spirochete Borrelia burgdorferi s. l. is the causative agent of Lyme disease
These molecular weights were confirmed experimentally by SDS-PAGE with Coomassie Brilliant Blue (CBB) staining (Fig 2A). The purity of both recombinant histidine tagged (His-tag) OspC (rOspC) variants was confirmed as higher than 93% by comparing the density of rOspC bands with all other visible bands on gel. The identities of both rOspC variants were further confirmed by peptide mass fingerprinting using MALDI-TOF mass spectrometry (MS), wherein the dominant protein bands were sequence matched with the known OspC protein sequence (NCBInr gi|374718430)
In this study we compared immunogenicity of two rOspC variants that differed in possessing a histidine tagged (His-tag) at either N' or C' terminus
Summary
Spirochete Borrelia burgdorferi s. l. is the causative agent of Lyme disease. at least nine Borrelia species are currently considered potentially pathogenic [1] B. afzelii, B. garinii, and B. burgdorferi s. s. still predominates in Europe and B. burgdorferi s. s. in the USA. At least nine Borrelia species are currently considered potentially pathogenic [1] B. afzelii, B. garinii, and B. burgdorferi s. If untreated by antibiotic therapy in time, Lyme disease can develop into a chronic phase of infection with long-lasting neural, cardiovascular, cutaneous, or orthopedic complications [2, 3]. The chronic phase can develop in spite of intensive antibiotic treatment. This complication emphasizes the need for the development of protective vaccines to control either Borrelia transmission from tick to vertebrate host or subsequently from spreading through the mammalian host organism [4,5,6]. (Outer surface protein) OspA and OspC are considered as the most promising antigens for vaccination purposes [5]
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