Statins reduce spirochetal burden and modulate immune responses in the C3H/HeN mouse model of Lyme disease

Current and emerging approaches for eliminating Borrelia burgdorferi and alleviating persistent Lyme disease symptoms

Lyme disease is the most prevalent tick-borne infection caused by Borrelia burgdorferi bacteria in North America. Other Borrelia species are predominately the cause of this disease in Eurasia with some distinct and various overlapping manifestations. Consequently, caution must be exercised when comparing the disease and its manifestations and treatment regimens in North America and Europe. Diagnosis of the early Lyme disease remains difficult using the currently FDA approved serological tests in the absence of a reported tick bite or of erythema migrans in many individuals, non-specific initial symptoms, and the absence of detectable anti-Borrelia antibodies in the prepatent period of infection. Furthermore, it is difficult to distinguish persistence of infection and disease versus reinfection in the endemic regions of Lyme disease by serological assays. If early infection remains untreated, spirochetes can disseminate and could affect various organs in the body with a variety of disease manifestations including arthralgias and musculoskeletal pain, neurologic symptoms and anomalies, and acrodermatitis chronicum atrophicans (ACA) in Europe. Although most patients recover after antibiotic treatment, an estimated ∼10-20% patients in the United States show persistence of symptoms known as post-treatment Lyme disease syndrome (PTLDS). The causes and biomarkers of PTLDS are not well-defined; however, several contributing factors with inconsistent degree of supporting evidence have been suggested. These include antigenic debris, dysregulation of immunological response, bacterial persisters, or combination of these features. This review highlights currently employed treatment approaches describing different antimicrobials used, and vaccine candidates tried to prevent B. burgdorferi infection.

A tick saliva serpin, IxsS17 inhibits host innate immune system proteases and enhances host colonization by Lyme disease agent

Lyme disease (LD) caused by Borrelia burgdorferi is among the most important human vector borne diseases for which there is no effective prevention method. Identification of tick saliva transmission factors of the LD agent is needed before the highly advocated tick antigen-based vaccine could be developed. We previously reported the highly conserved Ixodes scapularis (Ixs) tick saliva serpin (S) 17 (IxsS17) was highly secreted by B. burgdorferi infected nymphs. Here, we show that IxsS17 promote tick feeding and enhances B. burgdorferi colonization of the host. We show that IxsS17 is not part of a redundant system, and its functional domain reactive center loop (RCL) is 100% conserved in all tick species. Yeast expressed recombinant (r) IxsS17 inhibits effector proteases of inflammation, blood clotting, and complement innate immune systems. Interestingly, differential precipitation analysis revealed novel functional insights that IxsS17 interacts with both effector proteases and regulatory protease inhibitors. For instance, rIxsS17 interacted with blood clotting proteases, fXII, fX, fXII, plasmin, and plasma kallikrein alongside blood clotting regulatory serpins (antithrombin III and heparin cofactor II). Similarly, rIxsS17 interacted with both complement system serine proteases, C1s, C2, and factor I and the regulatory serpin, plasma protease C1 inhibitor. Consistently, we validated that rIxsS17 dose dependently blocked deposition of the complement membrane attack complex via the lectin complement pathway and protected complement sensitive B. burgdorferi from complement-mediated killing. Likewise, co-inoculating C3H/HeN mice with rIxsS17 and B. burgdorferi significantly enhanced colonization of mouse heart and skin organs in a reverse dose dependent manner. Taken together, our data suggests an important role for IxsS17 in tick feeding and B. burgdorferi colonization of the host.

Metabolic modeling predicts unique drug targets in Borrelia burgdorferi

IMPORTANCE

Lyme disease is often treated using long courses of antibiotics, which can cause side effects for patients and risks the evolution of antimicrobial resistance. Narrow-spectrum antimicrobials would reduce these risks, but their development has been slow because the Lyme disease bacterium, Borrelia burgdorferi, is difficult to work with in the laboratory. To accelerate the drug discovery pipeline, we developed a computational model of B. burgdorferi's metabolism and used it to predict essential enzymatic reactions whose inhibition prevented growth in silico. These predictions were validated using small-molecule enzyme inhibitors, several of which were shown to have specific activity against B. burgdorferi. Although the specific compounds used are not suitable for clinical use, we aim to use them as lead compounds to develop optimized drugs targeting the pathways discovered here.

Cellular and transcriptome signatures unveiled by single-cell RNA-Seq following ex vivo infection of murine splenocytes with Borrelia burgdorferi

Introduction

Lyme disease, the most common tick-borne infectious disease in the US, is caused by a spirochetal pathogen Borrelia burgdorferi (Bb). Distinct host responses are observed in susceptible and resistant strains of inbred of mice following infection with Bb reflecting a subset of inflammatory responses observed in human Lyme disease. The advent of post-genomic methodologies and genomic data sets enables dissecting the host responses to advance therapeutic options for limiting the pathogen transmission and/or treatment of Lyme disease.

Methods

In this study, we used single-cell RNA-Seq analysis in conjunction with mouse genomics exploiting GFP-expressing Bb to sort GFP+ splenocytes and GFP- bystander cells to uncover novel molecular and cellular signatures that contribute to early stages of immune responses against Bb.

Results

These data decoded the heterogeneity of splenic neutrophils, macrophages, NK cells, B cells, and T cells in C3H/HeN mice in response to Bb infection. Increased mRNA abundance of apoptosis-related genes was observed in neutrophils and macrophages clustered from GFP+ splenocytes. Moreover, complement-mediated phagocytosis-related genes such as C1q and Ficolin were elevated in an inflammatory macrophage subset, suggesting upregulation of these genes during the interaction of macrophages with Bb-infected neutrophils. In addition, the role of DUSP1 in regulating the expression of Casp3 and pro-inflammatory cytokines Cxcl1, Cxcl2, Il1b, and Ccl5 in Bb-infected neutrophils were identified.

Discussion

These findings serve as a growing catalog of cell phenotypes/biomarkers among murine splenocytes that can be exploited for limiting spirochetal burden to limit the transmission of the agent of Lyme disease to humans via reservoir hosts.

Ixodes scapularis nymph saliva protein blocks host inflammation and complement-mediated killing of Lyme disease agent, Borrelia burgdorferi

Tick serine protease inhibitors (serpins) play crucial roles in tick feeding and pathogen transmission. We demonstrate that Ixodes scapularis (Ixs) nymph tick saliva serpin (S) 41 (IxsS41), secreted by Borrelia burgdorferi (Bb)-infected ticks at high abundance, is involved in regulating tick evasion of host innate immunity and promoting host colonization by Bb. Recombinant (r) proteins were expressed in Pichia pastoris, and substrate hydrolysis assays were used to determine. Ex vivo (complement and hemostasis function related) and in vivo (paw edema and effect on Bb colonization of C3H/HeN mice organs) assays were conducted to validate function. We demonstrate that rIxsS41 inhibits chymase and cathepsin G, pro-inflammatory proteases that are released by mast cells and neutrophils, the first immune cells at the tick feeding site. Importantly, stoichiometry of inhibition analysis revealed that 2.2 and 2.8 molecules of rIxsS41 are needed to 100% inhibit 1 molecule of chymase and cathepsin G, respectively, suggesting that findings here are likely events at the tick feeding site. Furthermore, chymase-mediated paw edema, induced by the mast cell degranulator, compound 48/80 (C48/80), was blocked by rIxsS41. Likewise, rIxsS41 reduced membrane attack complex (MAC) deposition via the alternative and lectin complement activation pathways and dose-dependently protected Bb from complement killing. Additionally, co-inoculating C3H/HeN mice with Bb together with rIxsS41 or with a mixture (rIxsS41 and C48/80). Findings in this study suggest that IxsS41 markedly contributes to tick feeding and host colonization by Bb. Therefore, we conclude that IxsS41 is a potential candidate for an anti-tick vaccine to prevent transmission of the Lyme disease agent.

Cholesterol Contributes to Risk, Severity, and Machine Learning-Driven Diagnosis of Lyme Disease

BACKGROUND

Lyme disease is the most prevalent vector-borne disease in the US, yet its host factors are poorly understood and diagnostic tests are limited. We evaluated patients in a large health system to uncover cholesterol's role in the susceptibility, severity, and machine learning-based diagnosis of Lyme disease.

METHODS

A longitudinal health system cohort comprised 1 019 175 individuals with electronic health record data and 50 329 with linked genetic data. Associations of blood cholesterol level, cholesterol genetic scores comprising common genetic variants, and burden of rare loss-of-function (LoF) variants in cholesterol metabolism genes with Lyme disease were investigated. A portable machine learning model was constructed and tested to predict Lyme disease using routine lipid and clinical measurements.

RESULTS

There were 3832 cases of Lyme disease. Increasing cholesterol was associated with greater risk of Lyme disease and hypercholesterolemia was more prevalent in Lyme disease cases than in controls. Cholesterol genetic scores and rare LoF variants in CD36 and LDLR were associated with Lyme disease risk. Serological profiling of cases revealed parallel trajectories of rising cholesterol and immunoglobulin levels over the disease course, including marked increases in individuals with LoF variants and high cholesterol genetic scores. The machine learning model predicted Lyme disease solely using routine lipid panel, blood count, and metabolic measurements.

CONCLUSIONS

These results demonstrate the value of large-scale genetic and clinical data to reveal host factors underlying infectious disease biology, risk, and prognosis and the potential for their clinical translation to machine learning diagnostics that do not need specialized assays.

Association between statin use and clinical course, microbiologic characteristics, and long-term outcome of early Lyme borreliosis. A post hoc analysis of prospective clinical trials of adult patients with erythema migrans

Background

Statins were shown to inhibit borrelial growth in vitro and promote clearance of spirochetes in a murine model of Lyme borreliosis (LB). We investigated the impact of statin use in patients with early LB.

Methods

In this post-hoc analysis, the association between statin use and clinical and microbiologic characteristics was investigated in 1520 adult patients with early LB manifesting as erythema migrans (EM), enrolled prospectively in several clinical trials between June 2006 and October 2019 at a single-center university hospital. Patients were assessed at enrollment and followed for 12 months.

Results

Statin users were older than patients not using statins, but statin use was not associated with Borrelia seropositivity rate, Borrelia skin culture positivity rate, or disease severity as assessed by erythema size or the presence of LB-associated symptoms. The time to resolution of EM was comparable in both groups. The odds for incomplete recovery decreased with time from enrollment, were higher in women, in patients with multiple EM, and in those reporting LB-associated symptoms at enrollment, but were unaffected by statin use.

Conclusion

Statin use was not associated with clinical and microbiologic characteristics or long-term outcome in early LB.

Borrelia peptidoglycan interacting Protein (BpiP) contributes to the fitness of Borrelia burgdorferi against host-derived factors and influences virulence in mouse models of Lyme disease

The Peptidoglycan (PG) cell wall of the Lyme disease (LD) spirochete, Borrelia burgdorferi (Bb), contributes to structural and morphological integrity of Bb; is a persistent antigen in LD patients; and has a unique pentapeptide with L-Ornithine as the third amino acid that cross-links its glycan polymers. A borrelial homolog (BB_0167) interacted specifically with borrelilal PG via its peptidoglycan interacting motif (MHELSEKRARAIGNYL); was localized to the protoplasmic cylinder of Bb; and was designated as Borrelia peptidoglycan interacting Protein (BpiP). A bpiP mutant displayed no defect under in vitro growth conditions with similar levels of several virulence-related proteins. However, the burden of bpiP mutant in C3H/HeN mice at day 14, 28 and 62 post-infection was significantly lower compared to control strains. No viable bpiP mutant was re-isolated from any tissues at day 62 post-infection although bpiP mutant was able to colonize immunodeficient SCID at day 28 post-infection. Acquisition or transmission of bpiP mutant by Ixodes scapularis larvae or nymphs respectively, from and to mice, was significantly lower compared to control strains. Further analysis of bpiP mutant revealed increased sensitivity to vancomycin, osmotic stress, lysosomal extracts, human antimicrobial peptide cathelicidin-LL37, complement-dependent killing in the presence of day 14 post-infection mouse serum and increased internalization of CFSC-labeled bpiP mutant by macrophages and dendritic cells compared to control strains. These studies demonstrate the importance of accessory protein/s involved in sustaining integrity of PG and cell envelope during different phases of Bb infection.

Effect of Statin Use on the Clinical Manifestations, Laboratory Test Results and Outcome of Lyme Neuroborreliosis

Statins have anti-inflammatory and potentially antimicrobial activity, but whether they have a beneficial effect on the course of infectious diseases is controversial. In this study, we assessed the impact of pre-existing statin use on the course and outcome of Lyme neuroborreliosis manifested as meningoradiculitis (Bannwarth’s syndrome). One hundred and twenty three consecutive patients with Bannwarth’s syndrome, of whom 18 (14.6%) were being treated with statins, were included in the study. To assess the influence of statin use on the course and outcome of the disease, univariate and multivariable analyses were performed. No statistically significant association was found between statin pre-treatment and the clinical manifestations, laboratory test results, and outcome of Bannwarth’s syndrome. In conclusion, pre-existing use of statins did not significantly impact either the clinical presentation or the outcome of Bannwarth’s syndrome.

Specific composition of polyphenolic compounds with fatty acids as an approach in helping to reduce spirochete burden in Lyme disease: in vivo and human observational study

Background:

Lyme disease (LD) is a tick-borne infection caused by Borrelia burgdorferi sensu lato. The current therapeutic approach to this disease is limited to antibiotics. However, after their administration, about 20% of patients experience delayed onset of this illness manifesting as lingering persistent symptoms.

Methods:

To determine a suitable approach that would help reduce this number, we examined the efficacy of a composition of polyphenolic compounds (baicalein, luteolin, and rosmarinic acid) with fatty acids (monolaurin and cis-2-decenoic acid), and iodine/kelp in a Lyme disease animal model and volunteers.

Results:

The results showed that 4 weeks of dietary intake of this composition reduced the spirochete burden in animal tissues by about 75%. Basic and differential blood parameters did not show significant differences between control animals and the animals fed with this composition. Also, hepatic and renal toxicity markers were not changed and apoptosis was not observed. Relevant inflammatory cytokines such as IL-6, IL-17, TNF-α, and INF-γ, were elevated in infected animals but normalized in infected and treated animals. A small observational study revealed that after administration of this composition to 17 volunteers three times per day for 6 months, 67.4% of the volunteers with late or persistent LD, and not receptive to previous antibiotic application, responded positively, in terms of energy status as well as physical and psychological wellbeing to supplementation with this composition, while 17.7% had slight improvement, and 17.7% were none responsive.

Conclusion:

We concluded that this specific composition revealed feasible benefits in late or persistent LD management, although double-blind controlled clinical trials are warranted.

Statins: a viable candidate for host-directed therapy against infectious diseases

Statins were first identified over 40 years ago as lipid-lowering drugs and have been remarkably effective in treating cardiovascular diseases. As research advanced, the protective effects of statins were additionally attributed to their anti-inflammatory, antioxidative, anti-thrombotic and immunomodulatory functions rather than lipid-lowering abilities alone. By promoting host defence mechanisms and inhibiting pathological inflammation, statins increase survival in human infectious diseases. At the cellular level, statins inhibit the intermediates of the host mevalonate pathway, thus compromising the immune evasion strategies of pathogens and their survival. Here, we discuss the potential use of statins as an inexpensive and practical alternative or adjunctive host-directed therapy for infectious diseases caused by intracellular pathogens, such as viruses, protozoa, fungi and bacteria.

Comparison of Minimum Inhibitory Concentration (MIC) value of statin drugs: A Systematic Review

Background:

Microbial infection and its resistance to clinically approved drugs create a huge threat to human health. Emerging reports have indicated the potential of statin drugs in the treatment of various types of microbial infections. However, it is still unclear, how much concentration of statin is effective against microbial infections. In literature, Minimum Inhibitory Concentration (MIC) values of statin drugs vary according to strain, species, and the type of statins. Thus, the main aim of the current study is to compare the MIC values of various types of statins against various types of micro-organisms. The data related to statin and microbial infection has been extracted from Pub Med (from September 1

Methodology:

987 to October 2017). A total of 662 studies have been published from 1987 -2017 regarding statin and microbial infections. After inclusion and exclusion criteria, finally, 28 studies have been selected for comparative analysis of MIC values.

Results:

All the statin drugs have shown a significant effect on various types of microbial infections. Among all the tested statin drugs, Simvastatin has lower MIC value in almost all types of microorganisms as compared to other statin drugs. However, on S. pneumoniae and aspergillus, Fluvastatin has the lowest MIC values as compared to Simvastatin. Atorvastatin was found to be the most potent against almost all strains of gram-negative bacteria. However, Rosuvastatin and Pravastatin have high MIC value against all types of microorganisms. Further, FICI value indicated the synergetic effect of Simvastatin with Amphotericin B, Itraconazole, and Fluconazole against various strains of Cryptococcus.

Conclusion:

In conclusion, Simvastatin, Atorvastatin, and Fluvastatin could be developed as potential antimicrobial agents. However, further studies are required to understand its complete safety and efficacy profile..

Short-Chain Fatty Acids Alter Metabolic and Virulence Attributes of Borrelia burgdorferi

Borrelia burgdorferi responds to a variety of host-derived factors and appropriately alters its gene expression for adaptation under different host-specific conditions. We previously showed that various levels of acetate, a short-chain fatty acid (SCFA), altered the protein profile of B. burgdorferi In this study, we determined the effects of other physiologically relevant SCFAs in the regulation of metabolic/virulence-associated proteins using mutant borrelial strains. No apparent increase in the synthesis of outer surface protein C (OspC) was noted when a carbon storage regulator A (csrA of B. burgdorferi, or csrA_Bb ) mutant (mt) was propagated within dialysis membrane chambers implanted within rat peritoneal cavity, while the parental wild type (wt; B31-A3 strain) and csrA_Bb cis-complemented strain (ct) had increased OspC with a reciprocal reduction in OspA levels. Growth rates of wt, mt, ct, 7D (csrA_Bb mutant lacking 7 amino acids at the C terminus), and 8S (csrA_Bb with site-specific changes altering its RNA-binding properties) borrelial strains were similar in the presence of acetate. Increased levels of propionate and butyrate reduced the growth rates of all strains tested, with mt and 8S exhibiting profound growth deficits at higher concentrations of propionate. Transcriptional levels of rpoS and ospC were elevated on supplementation of SCFAs compared to those of untreated spirochetes. Immunoblot analysis revealed elevated levels of RpoS, OspC, and DbpA with increased levels of SCFAs. Physiological levels of SCFAs prevalent in select human and rodent fluids were synergistic with mammalian host temperature and pH to increase the levels of aforementioned proteins, which could impact the colonization of B. burgdorferi during the mammalian phase of infection.

Borrelia Host Adaptation Protein (BadP) Is Required for the Colonization of a Mammalian Host by the Agent of Lyme Disease

Borrelia burgdorferi, the agent of Lyme disease (LD), uses host-derived signals to modulate gene expression during the vector and mammalian phases of infection. Microarray analysis of mutants lacking the B orrelia host adaptation regulator (BadR) revealed the downregulation of genes encoding enzymes whose role in the pathophysiology of B. burgdorferi is unknown. Immunoblot analysis of the badR mutants confirmed reduced levels of these enzymes, and one of these enzymes, encoded by bb0086, shares homology to prokaryotic magnesium chelatase and Lon-type proteases. The BB0086 levels in B. burgdorferi were higher under conditions mimicking those in fed ticks. Mutants lacking bb0086 had no apparent in vitro growth defect but were incapable of colonizing immunocompetent C3H/HeN or immunodeficient SCID mice. Immunoblot analysis revealed reduced levels of proteins critical for the adaptation of B. burgdorferi to the mammalian host, such as OspC, DbpA, and BBK32. Both RpoS and BosR, key regulators of gene expression in B. burgdorferi, were downregulated in the bb0086 mutants. Therefore, we designated BB0086 the B orrelia host adaptation protein (BadP). Unlike badP mutants, the control strains established infection in C3H/HeN mice at 4 days postinfection, indicating an early colonization defect in mutants due to reduced levels of the lipoproteins/regulators critical for initial stages of infection. However, badP mutants survived within dialysis membrane chambers (DMCs) implanted within the rat peritoneal cavity but, unlike the control strains, did not display complete switching of OspA to OspC, suggesting incomplete adaptation to the mammalian phase of infection. These findings have opened a novel regulatory mechanism which impacts the virulence potential of B burgdorferi.