Proteomic analysis of Rickettsia akari proposes a 44 kDa-OMP as a potential biomarker for Rickettsialpox diagnosis.

BACKGROUND: Rickettsialpox is a febrile illness caused by the mite-borne pathogen Rickettsia akari. Several cases of this disease are reported worldwide annually. Nevertheless, the relationship between the immunogenicity of R. akari and disease development is still poorly understood. Thus, misdiagnosis is frequent. Our study is aiming to identify immunogenic proteins that may improve disease recognition and enhance subsequent treatment. To achieve this goal, two proteomics methodologies were applied, followed by immunoblot confirmation. RESULTS: Three hundred and sixteen unique proteins were identified in the whole-cell extract of R. akari. The most represented protein groups were found to be those involved in translation, post-translational modifications, energy production, and cell wall development. A significant number of proteins belonged to amino acid transport and intracellular trafficking. Also, some proteins affecting the virulence were detected. In silico analysis of membrane enriched proteins revealed 25 putative outer membrane proteins containing beta-barrel structure and 11 proteins having a secretion signal peptide sequence. Using rabbit and human sera, various immunoreactive proteins were identified from which the 44 kDa uncharacterized protein (A8GP63) has demonstrated a unique detection capability. It positively distinguished the sera of patients with Rickettsialpox from other rickettsiae positive human sera. CONCLUSION: Our proteomic analysis certainly contributed to the lack of knowledge of R. akari pathogenesis. The result obtained may also serve as a guideline for a more accurate diagnosis of rickettsial diseases. The identified 44 kDa uncharacterized protein can be certainly used as a unique marker of rickettsialpox or as a target molecule for the development of more effective treatment.

Functional and structural characterisation of 5 missense mutations of the phenylalanine hydroxylase.

Phenylketonuria (PKU) and hyperphenylalaninemia (HPA) are a group of genetic disorders predominantly caused by mutations in the phenylalanine hydroxylase (PAH) gene. To date, more than 950 variants have been identified, however the pathogenic mechanism of many variants remains unknown. In this study, in silico prediction and in vitro prokaryotic and eukaryotic expression systems were used to functionally characterize five PAH missense variants (p.F233I, p.R270I, p.F331S, p.S350Y, and p.L358F) previously identified in Slovak and Czech patients. p.F233I, p.R270I, and p.S350Y were classified as deleterious mutations since they showed no specific activity in functional assay and no response to chaperone co-expression. Protein levels of these PAH variants were very low when expressed in HepG2 cells, and only p.S350Y responded to BH4 precursor overload by significant increase in PAH monomer, probably due to reduced rate of protein degradation as the result of proper protein folding. Variants p.F331S and p.L358F exerted residual enzymatic activity in vitro. While the first can be classified as probably pathogenic due to its very low protein levels in HepG2 cells, the latter is considered to be mild mutation with protein levels of approximately 17.85% compared to wt PAH. Our findings contribute to better understanding of structure and function of PAH mutated enzymes and optimal treatment of PKU patients carrying these mutations using BH4 supplementation.

Evaluation of the possible use of genus Mentha derived essential oils in the prevention of SENLAT syndrome caused by Rickettsia slovaca.

ETHNOPHARMACOLOGICAL RELEVANCE: Essential oils and essential oil bearing medicinal and culinary plants have a long tradition of being used to combat infection, treat various conditions, and promote and restore health. Mint oils are traditionally applied to repel insects and treat various conditions including wounds, skin infections, inflammation, eczema, urticaria, psoriasis, scabies and insect bites. They are among essential oils promoted as a natural way to prevent tick-borne diseases and recommended as ingredients in various homemade repellent mixtures and tick-bite treatments. AIM OF THE STUDY: The aim of this study was to evaluate the effect of three most common mint oils - peppermint (Mentha x piperita L.), cornmint (M. arvensis L.), and spearmint (M. spicata L.) on obligate intracellular tick-borne bacterium Rickettsia slovaca. MATERIALS AND METHODS: Influence of mint oils on R. slovaca replication in Vero cells initially infected by lower (106) or higher (108) number of rickettsial particles was tested during in vitro cultivation with daily change of medium. qPCR and RT-qPCR based growth curves and linear mixed effect models were applied to evaluate the growth inhibition. Peppermint oil was further tested in pilot in vivo study on experimentally infected ticks. RESULTS: Two of the tested essential oils, peppermint and cornmint, significantly inhibited rickettsial growth. On average, peppermint oil reduced the amount of rickettsiae present on day 4 post infection up to 0.05% of the rickettsial load present in the respective controls. Cornmint oil decreased the amount of rickettsiae to 0.09% of control. Peppermint oil also significantly reduced the number of living rickettsiae in artificially infected ticks. CONCLUSIONS: Present study showed that essential oils with antimicrobial properties may also inhibit tick-transmitted bacteria, and thus their possible use as preventative measures against tick-borne diseases is worth further research.

Structural and Functional Impact of Seven Missense Variants of Phenylalanine Hydroxylase.

The molecular genetics of well-characterized inherited diseases, such as phenylketonuria (PKU) and hyperphenylalaninemia (HPA) predominantly caused by mutations in the phenylalanine hydroxylase (PAH) gene, is often complicated by the identification of many novel variants, often with no obvious impact on the associated disorder. To date, more than 1100 PAH variants have been identified of which a substantial portion have unknown clinical significance. In this work, we study the functionality of seven yet uncharacterized PAH missense variants p.Asn167Tyr, p.Thr200Asn, p.Asp229Gly, p.Gly239Ala, p.Phe263Ser, p.Ala342Pro, and p.Ile406Met first identified in the Czech PKU/HPA patients. From all tested variants, three of them, namely p.Asn167Tyr, p.Thr200Asn, and p.Ile406Met, exerted residual enzymatic activity in vitro similar to wild type (WT) PAH, however, when expressed in HepG2 cells, their protein level reached a maximum of 72.1% ± 4.9%, 11.2% ± 4.2%, and 36.6% ± 7.3% compared to WT PAH, respectively. Remaining variants were null with no enzyme activity and decreased protein levels in HepG2 cells. The chaperone-like effect of applied BH4 precursor increased protein level significantly for p.Asn167Tyr, p.Asp229Gly, p.Ala342Pro, and p.Ile406Met. Taken together, our results of functional characterization in combination with in silico prediction suggest that while p.Asn167Tyr, p.Thr200Asn, and p.Ile406Met PAH variants have a mild impact on the protein, p.Asp229Gly, p.Gly239Ala, p.Phe263Ser, and p.Ala342Pro severely affect protein structure and function.