Some Lyme disease spirochete isolates can bind complement regulatory protein factor H (fH), a process that may allow evasion of complement-mediated killing. Here we demonstrate significant differences in the fH binding capabilities of species of the Borrelia burgdorferi sensu lato complex. The percentages of B. burgdorferi, B. afzelii, and B. garinii bacteria that bound fH in either enzyme-linked immunosorbent assays or affinity ligand binding immunoblot assays were 100, 83, and 29%, respectively. The fH binding protein profiles were examined and found to exhibit variability among isolates and to form two distinct classes. Differences in fH binding ability may contribute to the differences in pathogenesis and clinical course observed upon infection with different species of the B. burgdorferi sensu lato complex.

Some Borrelia species associated with Lyme disease bind the complement-regulatory protein factor H (fH), a process that may aid in immune evasion. In this report we demonstrate that some Borrelia species associated with relapsing fever bind fH, but not those associated with avian borreliosis and epizootic bovine abortion. Cell-bound fH was also found to mediate cleavage of exogenously supplied human C3b, demonstrating the biological relevance of fH binding and its possible importance in the pathogenesis of the relapsing-fever spirochetes.

BBA68 (BbCRASP-1) of the Lyme disease spirochetes binds human factor H (FH) and FH-like protein 1 (FHL-1).Here we assess transcription of the BBA68 gene and production of BBA68 in infected mice and humans using real-time reverse transcriptase PCR and immunoblotting. The species specificity of FH binding to BBA68 was also tested. The data suggest that BBA68 does not play an important role in immune evasion in animals.The Lyme disease spirochete, Borrelia burgdorferi, can bind the human complement regulatory proteins, factor H (FH) and FH-like protein 1 (FHL-1) (1,8,11,16). FH and FHL-1 serve as cofactors in the factor I-mediated cleavage of C3b (18). C3b is an important opsonin and central component of the complement system. The binding of FH and FHL-1 to the bacterial surface is thought to locally increase the efficiency of C3b cleavage, locally downregulate the alternative complement cascade, and inhibit C3b-mediated opsonophagocytosis (30). The FH/FHL-1 binding proteins (FHBPs) identified in B. burgdorferi B31MI include the OspE proteins (BBL39, BBN38, and BBP38) and BBA68 (also referred to as BbCRASP-1) (1,8,10,11,15,16). Analyses of in vitro-cultivated bacteria indicate that BBA68 is the dominant FHBP and is the only paralog of the 14-member protein family 54 (The Institute for Genome Research designation) to exhibit human FH/FHL-1 binding activity (10, 15). Inactivation of BBA68 increases sensitivity to complement in vitro, and the introduction of BBA68 into Borrelia garinii strains that lack the gene decreases their serum sensitivity (3). While it is widely held that BBA68 plays an important role in immune evasion, earlier studies provided evidence that it may not be expressed during infection (2,17,23,25). In fact, Tokarz et al. demonstrated that, when human blood was added to actively growing cultures, BBA68 and BBA69 gene transcription was downregulated 1.8-fold. In addition, Brooks et al. demonstrated a sevenfold reduction in BBA68 transcript levels in spirochetes cultivated in dialysis membrane chambers implanted into the peritoneal cavities of rats (2, 23). The goals of this study were to further investigate the putative contribution of BBA68 in immune evasion in humans and other animals. In summary, the data indicate that the BBA68 gene is not transcribed during infection in mice and does not elicit an antibody response in mice and humans. In addition, BBA68 does not bind to FH produced by animals other than humans, and hence it is not likely to be involved in FH-mediated immune evasion in its natural mammalian reservoirs. Collectively, the data suggest that BBA68 does not carry out an important function directly in infected humans and animals.As one approach to assessing production of BBA68 during infection we screened for an antibody response to BBA68 in infected mice and humans. Since an understanding of the potential heterogeneity of BBA68 is an essential first step in interpreting immunoblot analyses and identifying the appropriate test antigen to be employed in the screening, we first assessed...

The binding of Borrelia burgdorferi OspE, OspF, and family 163 (Elp) proteins to factor H/factor H-like protein 1 (FHL-1) and other serum proteins from different animals was assessed. OspE paralogs bound factor H and unidentified serum proteins from a subset of animals, while OspF and Elp proteins did not. These data advance our understanding of factor H binding, the host range of the Lyme spirochetes, and the expanding role of OspE in pathogenesis.

Immune neutropenia is the most common referral to pediatric hematologists. Controversy exists as to whether anti-neutrophil antibody testing is necessary or helpful in establishing a diagnosis, predicting outcomes or establishing the necessity of treatment with G-CSF. It is also unclear if clinicians can separate immune neutropenia and hereditary/congenital neutropenia based on patients' clinical presentations, blood counts and anti-neutrophil antibody testing. We reviewed the records of 60 patients with the clinical diagnosis of autoimmune or idiopathic neutropenia, enrolled in the Severe Chronic Neutropenia International Registry (SCNIR) who had the onset of neutropenia before age 2 and who were tested for anti-neutrophil antibodies (positive or negative) to see if they resolved neutropenia by age 7 years. We identified 36 antibody positive and 24 antibody negative patients. Neutropenia resolved by age 7 in 27/36 (75%) antibody positive and in 15/24 (62.5%) antibody negative patients (p = 0.3910, Fisher's exact test). The median age at recovery for those with resolving neutropenia was 3.10 years for the antibody positive and 3.60 years for antibody negative patients (mean ages 3.39 and 3.52 years, respectively; p = 0.7614, unpaired t-test). All 60 patients had severe neutropenia (mean ANC 0.376 x 109/L ± 0.620, median 0.193 x 109/L) and history of recurrent fevers and infections, and were treated with G-CSF (mean dose antibody positive 3.12 ± 7.22 mcg/kg/day, mean dose antibody negative 2.57 ± 3.21 mcg/kg/day, p = 0.7311, unpaired t-test; median doses 1.42 and 1.53 mcg/kg/day, respectively). The ANC responses were quite similar, with antibody positive patients' mean ANC on treatment 3.36 x 109/L ± 1.48; antibody negative mean ANC on treatment 4.10 x 109/L ± 2.06 (p = 0.107, unpaired t-test; median ANCs 1.83 and 2.42 x 109/L, respectively). There were no apparent differences in demographic or hematological characteristics of the patients that resolved or failed to resolve. We also identified 8 children with ELANE mutations who had a positive test for anti-neutrophil antibodies. A positive anti-neutrophil antibody result is generally thought to predict a benign course and favor withholding treatment with G-CSF. Six of eight of these children did not receive G-CSF until after the development of severe infections, which included pneumonia, liver abscess, and cellulitis, including one who developed severe cellulitis with the loss of a lower extremity. Importantly, neutropenia did not resolve in any of the ELANE mutated patients. This retrospective review demonstrates that anti-neutrophil antibody testing in young children is of very limited or perhaps no value in predicting prognosis or response to G-CSF treatment. Furthermore, the results of the antibody testing may lead to withholding G-CSF therapy from children who are at risk of severe infectious complications. We believe it is prudent to treat young children with severe neutropenia who have recurrent fevers and infections independent of the anti-neutrophil antibody test results. We also advocate genetic testing to detect congenital neutropenia and predict outcomes in these patients. Disclosures Boxer: Amgen: Equity Ownership. Dale:Amgen: Consultancy, Honoraria, Research Funding.