A Tale of Two Spirochetes: Lyme Disease and Syphilis

Analysis of compositions of microbiomes with bias correction

Differential abundance (DA) analysis of microbiome data continues to be a challenging problem due to the complexity of the data. In this article we define the notion of "sampling fraction" and demonstrate a major hurdle in performing DA analysis of microbiome data is the bias introduced by differences in the sampling fractions across samples. We introduce a methodology called Analysis of Compositions of Microbiomes with Bias Correction (ANCOM-BC), which estimates the unknown sampling fractions and corrects the bias induced by their differences among samples. The absolute abundance data are modeled using a linear regression framework. This formulation makes a fundamental advancement in the field because, unlike the existing methods, it (a) provides statistically valid test with appropriate p-values, (b) provides confidence intervals for differential abundance of each taxon, (c) controls the False Discovery Rate (FDR), (d) maintains adequate power, and (e) is computationally simple to implement.

Neuroborreliosis and Neurosyphilis

PURPOSE OF REVIEW

This article presents an overview of the current diagnosis and management of two spirochetal infections of the nervous system, neuroborreliosis (Lyme disease) and neurosyphilis, focusing on similarities and differences. Although neuroborreliosis was first identified almost a century ago, much confusion remains about how to accurately diagnose this quite treatable nervous system infection. Well-established diagnostic tools and therapeutic regimens exist for neurosyphilis, which has been well-known for centuries.

RECENT FINDINGS

Serologic testing targeting the C6 antigen may simplify diagnostic testing in neuroborreliosis while improving accuracy. Historically, screening for syphilis has used a reaginic test followed by a treponeme-specific assay; alternative approaches, including use of well-defined recombinant antigens, may improve sensitivity without sacrificing specificity. In neuroborreliosis, measurement of the chemokine CXCL13 in CSF may provide a useful marker of disease activity in the central nervous system.

SUMMARY

Lyme disease causes meningitis, cranial neuritis, radiculitis, and mononeuropathy multiplex. Cognitive symptoms, occurring either during (encephalopathy) or after infection (posttreatment Lyme disease syndrome) are rarely, if ever, due to central nervous system infection. Posttreatment Lyme disease syndrome is not antibiotic responsive. Syphilis causes meningitis, cranial neuritis, chronic meningovascular syphilis, tabes dorsalis, and parenchymal neurosyphilis. The organism remains highly sensitive to penicillin, but residua of chronic infection may be irreversible.

Association of KIR genotypes and haplotypes with syphilis in a Chinese Han population

Killer immunoglobulin-like receptors (KIRs) can regulate the activation of NK and T cells in response to infection. Syphilis is a sexually transmitted infection caused by the Treponema pallidum subspecies pallidum spirochete bacterium. The objective of this study was to explore whether KIR genotypes and haplotypes were associated with syphilis in a Chinese Han population. Polymerase chain reaction with sequence-specific primers (PCR-SSP) was used to identify the KIR genotypes in 190 patients with syphilis and 192 healthy controls. The frequency of genotype P was higher in healthy controls than that in patients with syphilis (P = 0.002), and its OR was 0.304, while the frequencies of genotypes AE and AG were higher in patients with syphilis than those in healthy controls. The frequency of haplotype 17 was lower, and its OR was 0.321, whereas the frequencies of haplotype 1 and 6 were higher in patients with syphilis than those in healthy controls. KIR haplotypes A and B have distinctive centromeric (Cen) and telomeric (Tel) gene content motifs. The frequency of Tel-B/B was higher in patients with syphilis than that in healthy controls (P = 0.024). Based on these findings, it seems that individuals with the genotype AE, AG or Tel-B/B, or haplotypes 1 and 6 are susceptible to syphilis, whereas individuals with genotype P or haplotype 17 are protective from syphilis in the Chinese Han population.

Human leukocyte antigen-C and killer cell immunoglobulin-like receptor gene polymorphisms among patients with syphilis in a Chinese Han population

Syphilis is a sexually transmitted infection caused by the Treponema pallidum subspecies pallidum spirochete bacterium. The killer cell immunoglobulin-like receptors (KIR), interacting with human leukocyte antigens (HLA), regulate the activations of natural killer (NK) cells and certain T-cell subsets in response to microbe infection. The objective of this study was to explore whether KIR and HLA-C gene polymorphisms were associated with syphilis in a Chinese Han population. Polymerase chain reaction with sequence-specific primers (PCR-SSP) method was used to genotype KIR and HLA-C genes in 231 syphilis patients and 247 healthy controls. Framework genes KIR2DL4, KIR3DL2, KIR3DL3 and KIR3DP1 were present in all individuals. The frequencies of KIR2DS3 and KIR3DS1 were higher in syphilis patients than in healthy controls (p = 0.030 and p = 0.038, respectively), while the frequency of KIR2DS5 was higher in healthy controls than in syphilis patients (p = 0.015; OR = 0.575). The homozygote for HLA-C1 allele (HLA-C1C1) was more common in controls compared with syphilis patients (p = 0.030; OR = 0.667). The frequency of individuals with HLA-C1C1 and KIR2DL3 genotype was higher in control group relative to syphilis patient group (p = 0.018; OR = 0.647). These data indicated that KIR2DS3 and KIR3DS1 were more prevalent in syphilis patients than in controls, and that KIR2DS5, HLA-C1C1 and HLA-C1C1-KIR2DL3 were more prevalent in controls than in syphilis patients, respectively. These will require further investigation using functional studies.