Comparative Analysis of the Properties and Ligand Binding Characteristics of CspZ, a Factor H Binding Protein, Derived fromBorrelia burgdorferiIsolates of Human Origin

Abstract

Borrelia burgdorferi CspZ (BBH06/BbCRASP-2) binds the complement regulatory protein factor H (FH) and additional unidentified serum proteins. The goals of this study were to assess the ligand binding capability of CspZ orthologs derived from an extensive panel of human Lyme disease isolates and to further define the molecular basis of the interaction between FH and CspZ. While most B. burgdorferi CspZ orthologs analyzed bound FH, specific, naturally occurring polymorphisms, most of which clustered in a specific loop domain of CspZ, prevented FH binding in some orthologs. Sequence analyses also revealed the existence of CspZ phyletic groups that correlate with FH binding and with the relationships inferred from ribosomal spacer types (RSTs). CspZ type 1 (RST1) and type 3 (RST3) strains bind FH, while CspZ type 2 (RST2) strains do not. Antibody responses to CspZ were also assessed. Anti-CspZ antibodies were detected in mice by week 2 of infection, indicating that there was expression during early-stage infection. Analyses of sera collected from infected mice suggested that CspZ production continued over the course of long-term infection as the antibody titer increased over time. While antibody to CspZ was detected in several human Lyme disease serum samples, the response was not universal, and the titers were generally low. Vaccination studies with mice demonstrated that while CspZ is immunogenic, it does not elicit an antibody that is protective or that inhibits dissemination. The data presented here provide significant new insight into the interaction between CspZ and FH and suggest that there is a correlation between CspZ production and dissemination. However, in spite of its possible contributory role in pathogenesis, the immunological analyses indicated that CspZ is likely to have limited potential as a diagnostic marker and vaccine candidate for Lyme disease.

Borrelia burgdorferi Linear Plasmid 28-3 Confers a Selective Advantage in an Experimental Mouse-Tick Infection Model

“…Interestingly, some of the annotated protein-coding sequences with predicted functions are suggestive of a role in the infectious cycle. These include cspZ, encoding complement regulator-acquiring surface protein 2 (CRASP2), a factor H-binding protein produced during mammalian infection and thought to play a role in the resistance of B. burgdorferi to complement-mediated killing (23-25), although it is dispensable in a mouse infection model (26)(27)(28). In addition, lp28-3 genes bbh13, bbh15, bbh16 and bbh18 encode hypothetical lipoproteins, and bbh12 and bbh14, while not homologous to genes encoding proteins of known function, are differentially regulated in response to conditions mimicking those found in a mammal relative to those found in a tick (29)(30)(31)(32).…”

Complement regulator-acquiring surface proteins of Borrelia burgdorferi: Structure, function and regulation of gene expression

“…B. burgdorferi , B. afzelii , B. garinii , B. spielmanii , and B. bavariensis as well as B. bissettii (identity ≥97.2%) (Kraiczy et al, 2008; Rogers et al, 2009a; Rogers and Marconi, 2007; Schutzer et al, 2011, 2012). Despite these high degrees of conservation, there are some significant differences among CspZ proteins.…”

“…There is a species-linked polymorphism in B. afzelii , B. garinii , and B. spielmanii cspZ genes, which encode an N-terminal domain of 44 amino acids that is absent from B. burgdorferi CspZ proteins. CspZ derived from B. burgdorferi bind both CFH and FHL1, while the CspZ orthologs of B. garinii , B. afzelii , and B. spielmanii do not bind these complement regulators (Rogers et al, 2009a; Rogers and Marconi, 2007). The N-terminal extension found in B. garinii CspZ proteins does not prevent binding of CFH or FHL1, indicating that other elements are involved in ligand binding.…”

“…The N-terminal extension found in B. garinii CspZ proteins does not prevent binding of CFH or FHL1, indicating that other elements are involved in ligand binding. By investigating a number of additional B. burgdorferi isolates, Rogers et al (2009a) showed that some natural CspZ orthologs probably lack CFH binding activity due to a 4-amino acid insertion at the N terminus of CspZ and/or point mutations at 3 distinct positions (amino acids 51, 150, and 193). Computer modeling of CspZ suggests that the 4-amino acid insertion is located in a loop between 2 α-helices and thus may destabilize the architecture of the protein and indirectly affect the interactions between CspZ and complement regulators (Kraiczy et al, 2009).…”

“…The RST grouping is also linked to a strain’s tendency toward hematogenous dissemination and invasiveness (Iyer et al, 2001; Rogers et al, 2009a; Wormser et al, 2008). This relationship is linked to 3 CspZ phylogenetic clusters (groups 1–3).…”