Differential immune response to the variable surface loop antigen of P66 of Borrelia burgdorferi sensu lato species in geographically diverse populations of lyme borreliosis patients

Broadly Protective Multivalent OspA Vaccine against Lyme Borreliosis, Developed Based on Surface Shaping of the C-Terminal Fragment

The development of vaccines for prevention of diseases caused by pathogenic species can encounter major obstacles if high sequence diversity is observed between individual strains. Therefore, development might be restricted either to conserved antigens, which are often rare, or to multivalent vaccines, which renders the production more costly and cumbersome. In light of this complexity, we applied a structure-based surface shaping approach for the development of a Lyme borreliosis (LB) vaccine suitable for the United States and Europe. The surface of the C-terminal fragment of outer surface protein A (OspA) was divided into distinct regions, based primarily on binding sites of monoclonal antibodies (MAbs). In order to target the six clinically most relevant OspA serotypes (ST) in a single protein, exposed amino acids of the individual regions were exchanged to corresponding amino acids of a chosen OspA serotype. Six chimeric proteins were constructed, and, based on their immunogenicity, four of these chimeras were tested in mouse challenge models. Significant protection could be demonstrated for all four proteins following challenge with infected ticks (OspA ST1, OspA ST2, and OspA ST4) or with in vitro-grown spirochetes (OspA ST1 and OspA ST5). Two of the chimeric proteins were linked to form a fusion protein, which provided significant protection against in vitro-grown spirochetes (OspA ST1) and infected ticks (OspA ST2). This article presents the proof-of-concept study for a multivalent OspA vaccine targeting a wide range of pathogenic LB Borrelia species with a single recombinant antigen for prevention of Lyme borreliosis.

The TamB ortholog of Borrelia burgdorferi interacts with the β-barrel assembly machine (BAM) complex protein BamA

Two outer membrane protein (OMP) transport systems in diderm bacteria assist in assembly and export of OMPs. These two systems are the β-barrel assembly machine (BAM) complex and the translocation and assembly module (TAM). The BAM complex consists of the OMP component BamA along with several outer membrane associated proteins. The TAM also consists of an OMP, designated TamA, and a single inner membrane (IM) protein, TamB. Together TamA and TamB aid in the secretion of virulence-associated OMPs. In this study we characterized the hypothetical protein BB0794 in Borrelia burgdorferi. BB0794 contains a conserved DUF490 domain, which is a motif found in all TamB proteins. All spirochetes lack a TamA ortholog, but computational and physicochemical characterization of BB0794 revealed it is a TamB ortholog. Interestingly, BB0794 was observed to interact with BamA and a BB0794 regulatable mutant displayed altered cellular morphology and antibiotic sensitivity. The observation that B. burgdorferi contains a TamB ortholog that interacts with BamA and is required for proper outer membrane biogenesis not only identifies a novel role for TamB-like proteins, but also may explain why most diderms harbor a TamB-like protein while only a select group encodes TamA.

Borrelia burgdorferi HtrA: evidence for twofold proteolysis of outer membrane protein p66

In prokaryotes, members of the High Temperature Requirement A (HtrA) family of serine proteases function in the periplasm to degrade damaged or improperly folded membrane proteins. Borrelia burgdorferi, the agent of Lyme disease, codes for a single HtrA homolog. Two-dimensional electrophoresis analysis of B. burgdorferi B31A3 and a strain that overexpresses HtrA (A3HtrAOE) identified a downregulated protein in A3HtrAOE with a mass, pI and MALDI-TOF spectrum consistent with outer membrane protein p66. P66 and HtrA from cellular lysates partitioned into detergent-resistant membranes, which contain cholesterol-glycolipid-rich membrane regions known as lipid rafts, suggesting that HtrA and p66 may reside together in lipid rafts also. This agrees with previous work from our laboratory, which showed that HtrA and p66 are constituents of B. burgdorferi outer membrane vesicles. HtrA degraded p66 in vitro and A3HtrAOE expressed reduced levels of p66 in vivo. Fluorescence confocal microscopy revealed that HtrA and p66 colocalize in the membrane. The association of HtrA and p66 establishes that they could interact efficiently and their protease/substrate relationship provides functional relevance to this interaction. A3HtrAOE also showed reduced levels of p66 transcript in comparison with wild-type B31A3, indicating that HtrA-mediated regulation of p66 may occur at multiple levels.

Whole-genome DNA array analysis of the response of Borrelia burgdorferi to a bactericidal monoclonal antibody

Identification and characterization of genes that contribute to infection with Borrelia burgdorferi and, of those, genes that are targets of host responses is important for understanding the pathogenesis of Lyme disease. The complement-independent bactericidal monoclonal antibody (MAb) CB2 recognizes a carboxy-terminal, hydrophilic epitope of the outer surface protein B (OspB). CB2 kills B. burgdorferi by an unknown bactericidal mechanism. Upon binding of CB2 to OspB, differentially expressed gene products may be responsible for, or associated with, the death of the organism. A time course of the response of B. burgdorferi to CB2 was completed to analyze the differential gene expression in the bacteria over a period of visual morphological changes. Bacteria were treated with a sublethal concentration in which spirochetes were visibly distressed by the antibody but not lysed. Preliminary whole-genome DNA arrays at various time points within 1 h of incubation of B. burgdorferi with the antibody showed that most significant changes occurred at 25 min. Circular plasmid 32 (cp32)-encoded genes were active in this period of time, including the blyA homologs, phage holin system genes. DNA array data show that three blyA homologs were upregulated significantly, >/==" BORDER="0">2 standard deviations from the mean of the log ratios, and a P value of </=0.01. Quantitative real-time PCR analysis verified blyA and blyB upregulation over an 18- to 35-min time course. The hypothesis to test is whether the killing mechanism of CB2 is through uncontrolled expression of the blyA and blyB phage holin system.