The BB0345 Hypothetical Protein of Borrelia burgdorferi Is Essential for Mammalian Infection.

During the natural enzootic life cycle of Borrelia burgdorferi (also known as Borreliella burgdorferi), the bacteria must sense conditions within the vertebrate and arthropod and appropriately regulate expression of genes necessary to persist within these distinct environments. bb0345 of B. burgdorferi encodes a hypothetical protein of unknown function that is predicted to contain an N-terminal helix-turn-helix (HTH) domain. Because HTH domains can mediate protein-DNA interactions, we hypothesized that BB0345 might represent a previously unidentified borrelial transcriptional regulator with the ability to regulate events critical for the B. burgdorferi enzootic cycle. To study the role of BB0345 within mammals, we generated a bb0345 mutant and assessed its virulence potential in immunocompetent mice. The bb0345 mutant was able to initiate localized infection and disseminate to distal tissues but was cleared from all sites by 14 days postinfection. In vitro growth curve analyses revealed that the bb0345 mutant grew similar to wild-type bacteria in standard Barbour-Stoenner-Kelley II (BSK-II) medium; however, the mutant was not able to grow in dilute BSK-II medium or dialysis membrane chambers (DMCs) implanted in rats. Proteinase K accessibility assays and whole-cell partitioning indicated that BB0345 was intracellular and partially membrane associated. Comparison of protein production profiles between the wild-type parent and the bb0345 mutant revealed no major differences, suggesting BB0345 may not be a global transcriptional regulator. Taken together, these data show that BB0345 is essential for B. burgdorferi survival in the mammalian host, potentially by aiding the spirochete with a physiological function that is required by the bacterium during infection.

Surgical resection of macrocystic lymphatic malformations of the head and neck: Short and long-term outcomes.

BACKGROUND: Controversy exists on management of lymphatic malformations, with schools of thought advocating for observation, surgery or sclerotherapy. This study sought to examine outcomes after surgical resection of pediatric cervicofacial macrocystic lymphatic malformations (MLM). METHODS: Case series with planned data collection on pediatric patients with cervicofacial MLM who underwent surgical resection at a tertiary referral center for vascular anomalies from January 1995 to June 2016. For consistency in patient population analysis, patients who had pre-surgical sclerotherapy or had mixed or microcystic disease were excluded. The main outcome was complete response rate (CR) and long-term recurrence-free survival (RFS). RESULTS: Sixty-three patients who underwent excision of MLM were included, 52.4% were female, 77.8% Caucasian. The majority had de Serres stage I-III (96.8%) affecting the neck (71.4%). Patients were discharged the same day (28.6%), or had a 1 day median length-of-stay (interquartile range (IQR) = 2). Surgical complications included seroma/hematoma (9.5%), transient nerve weakness (facial nerve, sympathetic chain, or phrenic nerve, 6.3%), and infection (1.6%). On long-term follow-up (median: 12 months, IQR 1-43 months), a single surgery achieved CR in 90.5% of patients. RFS was achieved in 86% of patients in our observation period of up to 15 years. Most patients requiring a second intervention failed within 6-months of initial procedure (4/5 patients, 90%); associated factors included bilaterality, advanced staging, and partial response at first-follow-up (p = 0.0051, 0.0051, and <0.0001, respectively). CONCLUSIONS: Surgery is safe and effective as first line treatment for selected MLM. For stage I-III MLM CR and long-term RFS can be achieved with a single surgery. A direct and randomized comparison of treatment modalities is needed.

BB0238, a presumed tetratricopeptide repeat-containing protein, is required during Borrelia burgdorferi mammalian infection.

The Lyme disease spirochete, Borrelia burgdorferi, occupies both a tick vector and mammalian host in nature. Considering the unique enzootic life cycle of B. burgdorferi, it is not surprising that a large proportion of its genome is composed of hypothetical proteins not found in other bacterial pathogens. bb0238 encodes a conserved hypothetical protein of unknown function that is predicted to contain a tetratricopeptide repeat (TPR) domain, a structural motif responsible for mediating protein-protein interactions. To evaluate the role of bb0238 during mammalian infection, a bb0238-deficient mutant was constructed. The bb0238 mutant was attenuated in mice infected via needle inoculation, and complementation of bb0238 expression restored infectivity to wild-type levels. bb0238 expression does not change in response to varying culture conditions, and thus, it appears to be constitutively expressed under in vitro conditions. bb0238 is expressed in murine tissues during infection, though there was no significant change in expression levels among different tissue types. Localization studies indicate that BB0238 is associated with the inner membrane of the spirochete and is therefore unlikely to promote interaction with host ligands during infection. B. burgdorferi clones containing point mutations in conserved residues of the putative TPR motif of BB0238 demonstrated attenuation in mice that was comparable to that in the bb0238 deletion mutant, suggesting that BB0238 may contain a functional TPR domain.

Identification of lysine residues in the Borrelia burgdorferi DbpA adhesin required for murine infection.

Decorin-binding protein A (DbpA) of Borrelia burgdorferi mediates bacterial adhesion to heparin and dermatan sulfate associated with decorin. Lysines K82, K163, and K170 of DbpA are known to be important for in vitro interaction with decorin, and the DbpA structure, initially solved by nuclear magnetic resonance (NMR) spectroscopy, suggests these lysine residues colocalize in a pocket near the C terminus of the protein. In the current study, we solved the structure of DbpA from B. burgdorferi strain 297 using X-ray crystallography and confirmed the existing NMR structural data. In vitro binding experiments confirmed that recombinant DbpA proteins with mutations in K82, K163, or K170 did not bind decorin, which was due to an inability to interact with dermatan sulfate. Most importantly, we determined that the in vitro binding defect observed upon mutation of K82, K163, or K170 in DbpA also led to a defect during infection. The infectivity of B. burgdorferi expressing individual dbpA lysine point mutants was assessed in mice challenged via needle inoculation. Murine infection studies showed that strains expressing dbpA with mutations in K82, K163, and K170 were significantly attenuated and could not be cultured from any tissue. Proper expression and cellular localization of the mutated DbpA proteins were examined, and NMR spectroscopy determined that the mutant DbpA proteins were structurally similar to wild-type DbpA. Taken together, these data showed that lysines K82, K163, and K170 potentiate the binding of DbpA to dermatan sulfate and that an interaction(s) mediated by these lysines is essential for B. burgdorferi murine infection.