A joint effort: The interplay between the innate and the adaptive immune system in Lyme arthritis.

Articular joints are a major target of Borrelia burgdorferi, the causative agent of Lyme arthritis. Despite antibiotic treatment, recurrent or persistent Lyme arthritis is observed in a significant number of patients. The host immune response plays a crucial role in this chronic arthritic joint complication of Borrelia infections. During the early stages of B. burgdorferi infection, a major hinder in generating a proper host immune response is the lack of induction of a strong adaptive immune response. This may lead to a delayed hyperinflammatory reaction later in the disease. Several mechanisms have been suggested that might be pivotal for the development of Lyme arthritis and will be highlighted in this review, from molecular mimicry of matrix metallopeptidases and glycosaminoglycans, to autoimmune responses to live bacteria, or remnants of Borrelia spirochetes in joints. Murine studies have suggested that the inflammatory responses are initiated by innate immune cells, but this does not exclude the involvement of the adaptive immune system in this dysregulated immune profile. Genetic predisposition, via human leukocyte antigen-DR isotype and microRNA expression, has been associated with the development of antibiotic-refractory Lyme arthritis. Yet the ultimate cause for (antibiotic-refractory) Lyme arthritis remains unknown. Complex processes of different immune cells and signaling cascades are involved in the development of Lyme arthritis. When these various mechanisms are fully been unraveled, new treatment strategies can be developed to target (antibiotic-refractory) Lyme arthritis more effectively.

Plasmacytoid dendritic cells have divergent effects on HIV infection of initial target cells and induce a pro-retention phenotype.

Although HIV infection inhibits interferon responses in its target cells in vitro, interferon signatures can be detected in vivo soon after sexual transmission, mainly attributed to plasmacytoid dendritic cells (pDCs). In this study, we examined the physiological contributions of pDCs to early HIV acquisition using coculture models of pDCs with myeloid DCs, macrophages and the resting central, transitional and effector memory CD4 T cell subsets. pDCs impacted infection in a cell-specific manner. In myeloid cells, HIV infection was decreased via antiviral effects, cell maturation and downregulation of CCR5 expression. In contrast, in resting memory CD4 T cells, pDCs induced a subset-specific increase in intracellular HIV p24 protein expression without any activation or increase in CCR5 expression, as measured by flow cytometry. This increase was due to reactivation rather than enhanced viral spread, as blocking HIV entry via CCR5 did not alter the increased intracellular p24 expression. Furthermore, the load and proportion of cells expressing HIV DNA were restricted in the presence of pDCs while reverse transcriptase and p24 ELISA assays showed no increase in particle associated reverse transcriptase or extracellular p24 production. In addition, pDCs also markedly induced the expression of CD69 on infected CD4 T cells and other markers of CD4 T cell tissue retention. These phenotypic changes showed marked parallels with resident memory CD4 T cells isolated from anogenital tissue using enzymatic digestion. Production of IFNα by pDCs was the main driving factor for all these results. Thus, pDCs may reduce HIV spread during initial mucosal acquisition by inhibiting replication in myeloid cells while reactivating latent virus in resting memory CD4 T cells and retaining them for immune clearance.

Seasonal and Nonseasonal Longitudinal Variation of Immune Function.

Different components of the immune response show large variability between individuals, but they also vary within the same individual because of host and environmental factors. In this study, we report an extensive analysis of the immune characteristics of 56 individuals over four timepoints in 1 single year as part of the Human Functional Genomics Project. We characterized 102 cell subsets using flow cytometry; quantified production of eight cytokines and two chemokines in response to 20 metabolic, bacterial, fungal, and viral stimuli; and measured circulating markers of inflammation. Taking advantage of the longitudinal sampling, both seasonal and nonseasonal sources of variability were studied. The circulating markers of inflammation IL-18, IL-18 binding protein, and resistin displayed clear seasonal variability, whereas the strongest effect was observed for α-1 antitrypsin. Cytokine production capacity also showed strong seasonal changes, especially after stimulation with the influenza virus, Borrelia burgdorferi, and Escherichia coli Furthermore, we observed moderate seasonality effects on immune cell counts, especially in several CD4+/CD8+ T cell subpopulations. Age of the volunteers was an important factor influencing IFN-γ and IL-22 production, which matched the strong impact of age on several T cell subsets. Finally, on average, genetics accounted for almost 50% of the interindividual variance not already explained by age, sex, and body mass index, although this varies strongly for different parameters. In conclusion, seasonality is an important environmental factor that influences immune responses, in addition to specific genetic and nongenetic host factors, and this may well explain the seasonal variation in the incidence and severity of immune-mediated diseases.

Borrelia burgdorferi Is a Poor Inducer of Gamma Interferon: Amplification Induced by Interleukin-12.

Laboratory diagnosis of Lyme borreliosis (LB) is mainly based on serology, which has limitations, particularly in the early stages of the disease. In recent years there have been conflicting reports concerning a new diagnostic tool using the cytokine interferon-gamma (IFN-γ). Previous studies have generally found low concentrations of IFN-γ in early LB infection. The goal of this study is to investigate IFN-γ regulation during early LB and provide insights into the host response to B. burgdorferi. We performed in vitro experiments with whole blood assays and peripheral blood mononuclear cells (PBMCs) of LB patients and healthy volunteers exposed to B. burgdorferi and evaluated the IFN-γ response using ELISA and related interindividual variation in IFN-γ production to the presence of single nucleotide polymorphisms. IFN-γ production of B. burgdorferi-exposed PBMCs and whole blood was amplified by the addition of interleukin-12 (IL-12) to the stimulation system. This effect was observed after 24 h of B. burgdorferi stimulation in both healthy individuals and LB patients. The effect was highly variable between individuals, but was significantly higher in LB patients 6 weeks since the start of antibiotic treatment compared to healthy individuals. IL-12 p40 and IL-18 mRNA were upregulated upon exposure to B. burgdorferi, whereas IL-12 p35 and IFN-γ mRNA expression remained relatively unchanged. SNP Rs280520 in the downstream IL-12 pathway, Tyrosine Kinase 2, was associated with increased IFN-γ production. This study shows that IL-12 evokes an IFN-γ response in B. burgdorferi exposed cells, and that LB patients and healthy controls respond differently to this stimulation.

B. burgdorferi sensu lato-induced inhibition of antigen presentation is mediated by RIP1 signaling resulting in impaired functional T cell responses towards Candida albicans.

Antigen presentation is a crucial innate immune cell function that instructs adaptive immune cells. Loss of this pathway severely impairs the development of adaptive immune responses. To investigate whether B. burgdorferi sensu lato. spirochetes modulate the induction of an effective immune response, primary human PBMCs were isolated from healthy volunteers and stimulated with B. burgdorferi s.l. Through cell entry, TNF receptor I, and RIP1 signaling cascades, B. burgdorferi s.l. strongly downregulated genes and proteins involved in antigen presentation, specifically HLA-DM, MHC class II and CD74. Antigen presentation proteins were distinctively inhibited in monocyte subsets, monocyte-derived macrophages, and dendritic cells. When compared to a range of other pathogens, B. burgdorferi s.l.-induced suppression of antigen presentation appears to be specific. Inhibition of antigen presentation interfered with T-cell recognition of B. burgdorferi s.l., and memory T-cell responses against Candidaalbicans. Re-stimulation of PBMCs with the commensal microbe C.albicans following B. burgdorferi s.l. exposure resulted in significantly reduced IFN-γ, IL-17 and IL-22 production. These findings may explain why patients with Lyme borreliosis develop delayed adaptive immune responses. Unravelling the mechanism of B. burgdorferi s.l.-induced inhibition of antigen presentation, via cell entry, TNF receptor I, and RIP1 signaling cascades, explains the difficulty to diagnose the disease based on serology and to obtain an effective vaccine against Lyme borreliosis.

Correction: A systematic review and meta-analysis of the protective effects of metformin in experimental myocardial infarction.

[This corrects the article DOI: 10.1371/journal.pone.0183664.].

The stability of antimycobacterial drugs in media used for drug susceptibility testing.

The emergence of drug-resistant tuberculosis and disease caused by nontuberculous mycobacteria has increased the need for accurate drug susceptibility testing of mycobacteria. The stability of the tested drugs in relevant test media have been understudied. We assessed the stability of isoniazid, rifampicin, clarithromycin, linezolid and amikacin in Middlebrook 7H9 medium and that of clarithromycin, amikacin and cefoxitin in the cation-adjusted Mueller Hinton broth. We used ultra-performance liquid chromatography (UPLC) methods for rifampicin and isoniazid and a microbiological assay for rifampicin, clarithromycin, amikacin, cefoxitin and linezolid. Rifampicin and isoniazid concentrations in Middlebrook 7H9 medium had decreased by 92% and 54% after 7 days. The microbiological assay revealed decreases in drug concentration of ≥75% (rifampicin, clarithromycin, cefoxitin) and 60% (linezolid) after 14 days. With the exception of amikacin, all antimycobacterial drugs were unstable during 14 days of incubation in the preferred media for DST. Drug stability may influence minimum inhibitory concentration measurements.

A systematic review of discomfort due to toe or ear clipping in laboratory rodents.

Toe clipping and ear clipping (also ear notching or ear punching) are frequently used methods for individual identification of laboratory rodents. These procedures potentially cause severe discomfort, which can reduce animal welfare and distort experimental results. However, no systematic summary of the evidence on this topic currently exists. We conducted a systematic review of the evidence for discomfort due to toe or ear clipping in rodents. The review methodology was pre-specified in a registered review protocol. The population, intervention, control, outcome (PICO) question was: In rodents, what is the effect of toe clipping or ear clipping, compared with no clipping or sham clipping, on welfare-related outcomes? Through a systematic search in PubMed, Embase, Web of Science and grey literature, we identified seven studies on the effect of ear clipping on animal welfare, and five such studies on toe clipping. Studies were included in the review if they contained original data from an in vivo experiment in rodents, assessing the effect of toe clipping or ear clipping on a welfare-related outcome. Case studies and studies applying unsuitable co-interventions were excluded. Study quality was appraised using an extended version of SYstematic Review Centre for Laboratory animal Experimentation (SYRCLE)'s risk of bias tool for animal studies. Study characteristics and outcome measures were highly heterogeneous, and there was an unclear or high risk of bias in all studies. We therefore present a narrative synthesis of the evidence identified. None of the studies reported a sample size calculation. Out of over 60 different outcomes, we found evidence of discomfort due to ear clipping in the form of increased respiratory volume, vocalization and blood pressure. For toe clipping, increased vocalization and decreased motor activity in pups were found, as well as long-term effects in the form of reduced grip strength and swimming ability in adults. In conclusion, there is too little evidence to reliably assess discomfort due to toe or ear clipping, and the quality of the available evidence is uncertain. Adequately powered, high-quality studies reporting reliable, relevant outcome measures are needed to accurately assess the impact of these identification techniques. Until more reliable evidence is available, any effect of toe clipping or ear clipping on animal welfare and study results cannot be confirmed or excluded.