Correlation of Culture Positivity, PCR Positivity, and Burden of Borrelia burgdorferi Sensu Lato in Skin Samples of Erythema Migrans Patients with Clinical Findings

Background

Limited data are available regarding the relationship of Borrelia burden in skin of patients with erythema migrans (EM) and the disease course and post-treatment outcome.

Methods

We studied 121 adult patients with EM in whom skin biopsy specimens were cultured and analyzed by quantitative PCR for the presence of Borreliae. Evaluation of clinical and microbiological findings were conducted at the baseline visit, and 14 days, 2, 6, and 12 months after treatment with either amoxicillin or cefuroxime axetil.

Results

In 94/121 (77.7%) patients Borrelia was detected in skin samples by PCR testing and 65/118 (55.1%) patients had positive skin culture result (96.8% B. afzelii, 3.2% B. garinii). Borrelia culture and PCR results correlated significantly with the presence of central clearing and EM size, while Borrelia burden correlated significantly with central clearing, EM size, and presence of newly developed or worsened symptoms since EM onset, with no other known medical explanation (new or increased symptoms, NOIS). In addition, the logistic regression model for repeated measurements adjusted for time from inclusion, indicated higher Borrelia burden was a risk factor for incomplete response (defined as NOIS and/or persistence of EM beyond 14 days and/or occurrence of new objective signs of Lyme borreliosis). The estimated association between PCR positivity and unfavorable outcome was large but not statistically significant, while no corresponding relationship was observed for culture positivity.

Conclusions

Higher Borrelia burden in EM skin samples was associated with more frequent central clearing and larger EM lesions at presentation, and with a higher chance of incomplete response.

Evaluation of OspA vaccination-induced serological correlates of protection against Lyme borreliosis in a mouse model

BACKGROUND

For clinical development of a novel multivalent OspA vaccine against Lyme borreliosis, serological assays are required which can be used to establish immune correlates of protection against infection with Borrelia.

METHODS

Four assays (an OspA IgG ELISA, a competitive inhibition (CI) ELISA, a Borrelia surface-binding (SB) assay and a Borrelia killing assay) were used to evaluate the correlation between immune responses induced by rOspA 1/2 (a chimeric immunogen containing protective epitopes from OspA serotypes 1 and 2), and protective immunity against infection by B. burgdorferi s.s. (OspA-1) and B. afzelii (OspA-2). Mice were immunized with OspA 1/2 doses ranging from 0.3 ng to 100 ng, to induce a range of OspA antibody titers, and exposed to needle challenge with B. burgdorferi s.s. or tick challenge with B. afzelii. Receiver operator characteristics (ROC) curves were constructed for each assay, and the area under the curve (AUC), sensitivity, specificity and Youden Index were calculated. Potential cutoff antibody titers which could be used as correlates of vaccine-induced protection were derived from the maximum Youden Index.

RESULTS

Immunization with OspA-1/2 provided dose-dependent protection against infection with B. burgdorferi s.s. and B. afzelii. Antibody responses detected by all four assays were highly significantly correlated with protection from infection by either B. burgdorferi s.s. (p<0.0001 to 0.0062) or B. afzelii (p<0.0001). ROC analyses of the diagnostic effectiveness of each assay showed the AUC to range between 0.95 and 0.79, demonstrating that all assays distinguish well between infected and non-infected animals. Based on sensitivity, specificity and AUC, the OspA IgG ELISA and SB assays best discriminated between infected and non-infected animals.

CONCLUSIONS

All four assays differentiate well between Borrelia-infected and non-infected animals. The relatively simple, high throughput IgG ELISA would be suitable to establish immune correlates of protection for the novel OspA vaccine in clinical trials.

Quantitative detection of Borrelia burgdorferi sensu lato in erythema migrans skin lesions using internally controlled duplex real time PCR

B. burgdorferi sensu stricto, B. afzelii, B. garinii and B. bavariensis are the principal species which account for Lyme borreliosis (LB) globally. We have developed an internally controlled duplex quantitative real time PCR assay targeting the Borrelia 16S rRNA and the human RNAseP genes. This assay is well-suited for laboratory confirmation of suspected cases of LB and will be used to assess the efficacy of a vaccine against LB in clinical trials. The assay is highly specific, successfully detecting DNA extracted from 83 diverse B. burgdorferi sensu lato strains representing all major species causing LB, while 21 unrelated microbial species and human genomic DNA tested negative. The assay was highly reproducible and sensitive, with a lower limit of detection of 6 copies per PCR reaction. Together with culture, the assay was used to evaluate paired 3 mm skin biopsy samples taken from 121 patients presenting with solitary erythema migrans (EM) lesion. PCR testing identified more positive biopsy samples than culture (77.7% PCR positive versus 55.1% culture positive) and correctly identified all specimens scored as culture positive. OspA-based typing identified the majority of isolates as B. afzelii (96.8%) and the bacterial load was significantly higher in culture positive biopsies than in culture negative biopsies (P<0.001). The quantitative data also enabled relationships between Borrelia burden and patient symptoms to be evaluated. The bacterial load was significantly higher among patients with systemic symptoms than without (P = 0.02) and was significantly higher for biopsies retrieved from patients with EM lesions with central clearing (P<0.001). 16S copy numbers were moderately lower in samples from patients reporting a history of LB (P = 0.10). This is the first quantitative PCR study of human skin biopsies predominantly infected with B. afzelii and the first study to demonstrate a clear relationship between clinical symptoms in B. afzelii-infected patients and Borrelia burden.

A new approach to a Lyme disease vaccine

A single recombinant outer surface protein A (OspA) antigen designed to contain protective elements from 2 different OspA serotypes (1 and 2) is able to induce antibody responses that protect mice against infection with either Borrelia burgdorferi sensu stricto (OspA serotype-1) or Borrelia afzelii (OspA serotype-2). Protection against infection with B burgdorferi ss strain ZS7 was demonstrated in a needle-challenge model. Protection against B. afzelii species was shown in a tick-challenge model using feral ticks. In both models, as little as .03 μg of antigen, when administered in a 2-dose immunization schedule with aluminum hydroxide as adjuvant, was sufficient to provide complete protection against the species targeted. This proof of principle study proves that knowledge of protective epitopes can be used for the rational design of effective, genetically modified vaccines requiring fewer OspA antigens and suggests that this approach may facilitate the development of an OspA vaccine for global use.

Wide distribution of a high-virulence Borrelia burgdorferi clone in Europe and North America

The A and B clones of Borrelia burgdorferi sensu stricto, distinguished by outer surface protein C (ospC) gene sequences, are commonly associated with disseminated Lyme disease. To resolve phylogenetic relationships among isolates, we sequenced 68 isolates from Europe and North America at 1 chromosomal locus (16S-23S ribosomal RNA spacer) and 3 plasmid loci (ospC,dbpA, and BBD14). The ospC-A clone appeared to be highly prevalent on both continents, and isolates of this clone were uniform in DNA sequences, which suggests a recent trans-oceanic migration. The genetic homogeneity of ospC-A isolates was confirmed by sequences at 6 additional chromosomal housekeeping loci (gap, alr, glpA, xylB, ackA, and tgt). In contrast, the ospC-B group consists of genotypes distinct to each continent, indicating geographic isolation. We conclude that the ospC-A clone has dispersed rapidly and widely in the recent past. The spread of the ospC-A clone may have contributed, and likely continues to contribute, to the rise of Lyme disease incidence.

Cell culture (Vero) derived whole virus (H5N1) vaccine based on wild-type virus strain induces cross-protective immune responses

The rapid spread and the transmission to humans of avian influenza virus (H5N1) have induced world-wide fears of a new pandemic and raised concerns over the ability of standard influenza vaccine production methods to rapidly supply sufficient amounts of an effective vaccine. We report here on a robust and flexible strategy which uses wild-type virus grown in a continuous cell culture (Vero) system to produce an inactivated whole virus vaccine. Candidate vaccines based on clade 1 and clade 2 influenza H5N1 strains were developed and demonstrated to be highly immunogenic in animal models. The vaccines induce cross-neutralising antibodies, highly cross-reactive T-cell responses and are protective in a mouse challenge model not only against the homologous virus but also against other H5N1 strains, including those from another clade. These data indicate that cell culture-grown whole virus vaccines, based on the wild-type virus, allow the rapid high yield production of a candidate pandemic vaccine.

Delineation of Borrelia burgdorferi sensu lato species by multilocus sequence analysis and confirmation of the delineation of Borrelia spielmanii sp. nov

To evaluate multilocus sequence analysis (MLSA) for taxonomic purposes in the delineation of species withinBorrelia burgdorferi sensu lato, seven relevant loci of various strains for which extensive DNA–DNA reassociation data were available were sequenced. MLSA delineation proved to be fully concordant with conventional methods. Our analysis confirmed the delineation of a novel species,Borrelia spielmaniisp. nov., previously known as ‘Borrelia spielmani’ Richteret al. 2004, with strain PC-Eq17N5T(=DSM 16813T=CIP 108855T) as the type strain.

A DNA vaccine encoding the outer surface protein C from Borrelia burgdorferi is able to induce protective immune responses

The outer surface protein C (OspC) of Borrelia burgdorferi, the spirochete that causes Lyme disease, is a promising candidate for a vaccine against borreliosis. BALB/c and C3H/HeJ mice were immunized either with recombinant OspC protein or with plasmid DNA encoding OspC fused to the human tissue plasminogen activator leader sequence (pCMV-TPA/ZS7). The influence of the route of administering the DNA and the use of oligodeoxynucleotides containing CpG-motifs on the development of the immune response was investigated. In both mouse strains, protein as well as gene-gun immunization induced Th2 type responses, whereas needle injection of plasmid DNA resulted in Th1 type antibody production. Co-injection of CpG-motifs did not significantly modify the response type in any immunization group, as indicated by only marginal changes of antibody subclass distribution. The protection rate after challenge with 10(4) B. burgdorferi organisms per mouse was between 80% and 100% for all groups. These results demonstrate, for the first time, that a DNA vaccine encoding OspC of B. burgdorferi is suitable for inducing protection against Lyme borreliosis.

Gene gun bombardment with gold particles displays a particular Th2-promoting signal that over-rules the Th1-inducing effect of immunostimulatory CpG motifs in DNA vaccines

The mode of administering a DNA vaccine can influence the type of immune response induced by the vaccine. For instance, application of a DNA vaccine by gene gun typically induces a Th2-type reaction, whereas needle inoculation triggers a Th1 response. It has been proposed that the approximately 100-fold difference in the amount of DNA administered by these two methods is the critical factor determining whether a Th1 or a Th2 response is made. To test this hypothesis, BALB/c mice were immunized with two plasmid DNA constructs encoding different proteins (OspC/ZS7 of Borrelia burgdorferi and Bet v 1a, the major birch pollen allergen). Both vaccines were applied by needle and/or by gene gun immunization at the same and at different sites of injection. An analysis of the IgG subclass distribution and measurement of IFN-gamma after antigen-specific lymphoproliferation does not support the widely accepted view that Th2-type immunity induced by gene gun application is solely due to the low amount of injected plasmid DNA thus falling below the critical concentration of CpG motifs necessary for Th1-induction. Furthermore, the data also indicate a strong and even systemic adjuvant effect of the gene gun shot itself.

Improvement of the immune response against plasmid DNA encoding OspC of Borrelia by an ER-targeting leader sequence

The present study outlines the characterization of a DNA-based immune response against the OspC antigen, one of the most promising candidates for a Borrelia vaccine. Balb/c mice were injected intradermally with plasmid DNA encoding the OspC gene (lacking the natural leader sequence) under transcriptional control of the cytomegalovirus (CMV) promotor. Immunization with this construct elicited only a marginal response, which was drastically improved by a fusion construct containing the human tissue plasminogen activator (hTPA) signal sequence. The results indicate that for DNA-based immunization against OspC an ER-targeting signal may be necessary for both antibody production as well as cellular immune responses.

Evidence for lateral transfer and recombination in OspC variation in Lyme disease Borrelia

The ospC gene was amplified by the polymerase chain reaction from each of 76 Lyme disease Borrelia strains. Restriction fragment length polymorphism (RFLP) analysis demonstrated 33 distinct RFLP types; two additional RFLP types were identified from published ospC sequences. For each RFLP type, at least one ospC gene was sequenced and the degree of sequence relatedness examined by construction of an ospC gene tree. The genes were extremely diverse, with sequence identity ranging from 74.4% to 99.0%; the majority of changes are localized within the central portion of the molecule. A comparison of ospC sequences suggests that recombination occurs frequently between ospC alleles; this genetic exchange is proposed to be mediated by lateral transfer of ospC sequences. Evidence indicates that recombination occurs between ospC genes from the same Borrelia species (i.e. B. afzelii and B. garinii) as well as between different Borrelia species (i.e. B. afzelii and B. garinii, B. burgdorferi and genogroup DN127).

Identification of Bordetella avium using the polymerase chain reaction

A DNA fragment from Bordetella pertussis, encoding the fim2 fimbrial subunit gene with adjacent sequences, was used as a probe for the detection of homologous sequences in chromosomal DNA of Bordetella avium. A 1.8 kb Sa1I-PstI fragment from the genome of B. avium, which hybridized with the probe, was isolated and sequenced. No fimbrial subunit gene was located on the B. avium DNA fragment. Two regions could be distinguished in the sequence of the fragment. Region 1, which was 80% identical to the sequence upstream of the fim2 gene of B. pertussis and region 2, which had no identity with any known sequence. A 491 bp EagI DNA fragment (probe A) within region 1 and a 650 bp EagI DNA fragment (probe B) within region 2 were used as DNA probes on restriction endonuclease digests of chromosomal DNA from various bacterial species. This hybridization experiment showed that the region 2 sequence was specific for B. avium. A polymerase chain reaction (PCR) with specific primers within region 2 resulted in the amplification of a 500 bp DNA fragment with B. avium DNA only. This PCR is a useful method for the rapid detection of B. avium and appeared useful to discriminate B. avium from other Bordetella species and also from Alcaligenes faecalis.

Analysis of the chromosomal location of two copies of a Bordetella pertussis insertion sequence

IS481v1 and IS481v2 are two copies of a Bordetella pertussis insertion sequence element. We have shown that IS481v1 is located within 3 kbp of the start of the adenylate cyclase gene whilst IS481v2 is immediately adjacent to the end of the agglutinogen 2 gene and provides the stop codon for that gene. In addition, IS481v1 and IS481v2 were present at these two specific sites in nine strains of B. pertussis, including two Phase IV strains which expressed neither adenylate cyclase nor agglutinogen 2 and three Phase I strains which did not express agglutinogen 2. The loss of expression in these strains is not the result of DNA rearrangements at the sites of IS481v1 or IS481v2.

Analysis of separate isolates of Bordetella pertussis repeated DNA sequences

Two independent isolates of a Bordetella pertussis repeated DNA unit were sequenced and shown to be an insertion sequence element with five nucleotide differences between the two copies. The sequences were 1053 bp in length with near-perfect terminal inverted repeats of 28 bp, had three open reading frames, and were each flanked by short direct repeats. The two insertion sequences showed considerable homology to two other B. pertussis repeated DNA sequences reported recently: IS481 and a 530 bp repeated DNA unit. The B. pertussis insertion sequence would appear to comprise a group of closely related sequences differing mainly in flanking direct repeats and the terminal inverted repeats. The two isolates reported here, which were from the adenylate cyclase and agglutinogen 2 regions of the genome, were numbered IS48lvl and IS48lv2 respectively.

Cloning and nucleotide sequence analysis of the serotype 2 fimbrial subunit gene of Bordetella pertussis

An oligonucleotide probe complementary to the beginning of the gene encoding the serotype 2(ST2) fimbrial subunit of Bordetella pertussis was synthesized and a cloned DNA fragment hybridizing with the probe identified and sequenced. Several lines of evidence indicate that an open reading frame with coding information for a polypeptide of 207 amino acids, including a 26-amino-acid signal sequence, is the ST2 gene. The protein deduced from the nucleotide sequence shows good agreement with the NH2-terminal amino acid sequence, amino acid composition and molecular weight of the purified fimbrial subunit. In addition, the proposed ST2 subunit is shown to have homology with other fimbrial subunits.

Characterization of fimbrial subunits from Bordetella species

Using antisera raised against serotype 2 and 3 fimbrial subunits from Bordetella pertussis, serologically related polypeptides were detected in Bordetella bronchiseptica, Bordetella parapertussis and Bordetella avium strains. The two B. pertussis fimbrial subunits, and three of the serologically related B. bronchiseptica polypeptides, were shown to be very similar in amino acid composition and N-terminal amino acid sequence. Homology was observed between the N-termini of these polypeptides, and fimbrial subunits from Escherichia coli, Haemophilus influenzae and Proteus mirabilis. A synthetic oligonucleotide probe, derived from the N-terminal sequence of the B. pertussis serotype 2 fimbrial subunit, was used to identify fimbrial genes in genomic Southern blots. The results suggested the presence of multiple fimbrial subunit genes in B. pertussis, B. bronchiseptica and B. parapertussis. The DNA probe was used to clone one of the three tentative fimbrial subunit genes detected in B. pertussis.

Phenotypic modification of the reactivity in human serum of Escherichia coli K1 isolates

Three Escherichia coli strains producing the K1 antigen and shown to be resistant to the complement-mediated bactericidal action of human serum when grown in batch culture, were cultivated in the chemostat under conditions of carbon-, nitrogen-, magnesium- and phosphate-limitation. All strains were fully serum resistant when grown under carbon-limiting conditions but became phenotypically serum sensitive when limited by magnesium. One strain, belonging to serogroup O7:K1, also displayed serum sensitivity when nitrogen limited and showed an intermediate serum response when phosphate was used as the limiting nutrient.

Production and properties of Bordetella pertussis heat-labile toxin

Twelve selected strains of Bordetella pertussis were compared quantitatively for their ability to produce heat-labile toxin (HLT); all proved to be active producers, with only a three-fold range between the highest and the lowest. Bordet-Gengou agar, charcoal agar, modified Hornibrook medium and Stainer and Schölte (12G) medium differed little in their ability to support toxin production by three B. pertussis strains. However, cells grown on the solid media for 24 h were slightly more toxic than their counterparts grown for 72 h whereas in the liquid media the opposite was true. The concentration of iron in the medium did not influence HLT production, but high concentrations of nicotinic acid significantly reduced the HLT content of the cells. Crude preparations of toxin underwent only a 10% loss of toxicity per annum at -20 degrees C and were stable for up to 2 weeks at 4 degrees C. At 37 degrees C, toxicity was lost within a few days. The toxin was partially purified by a series of mild procedures and had a mol. wt by gel filtration of 89 000 +/- 10%. HLT was toxoided by treatment with formaldehyde to give a product which was immunogenic in rabbits but not in mice. Because anti-HLT could be absorbed out of the rabbit antisera by treatment with intact B. pertussis, it was concluded that some of the HLT in the bacteria is surface-exposed even though the main part may have a cytoplasmic location.