Development of an AAV9 coding for a 3XFLAG-TALEfrat#8-VP64 able to increase in vivo the human frataxin in YG8R mice

Artificially designed transcription activator-like effector (TALE) proteins fused to a transcription activation domain (TAD), such as VP64, are able to activate specific eukaryotic promoters. They thus provide a good tool for targeted gene regulation as a therapy. However, the efficacy of such an agent in vivo remains to be demonstrated as the majority of studies have been carried out in cell culture. We produced an adeno-associated virus 9 (AAV9) coding for a TALEfrat#8 containing 13 repeat variable diresidues able to bind to the proximal promoter of human frataxin (FXN) gene. This TALEfrat#8 was fused with a 3XFLAG at its N terminal and a VP64 TAD at its C terminal, and driven by a CAG promoter. This AAV9_3XFLAG-TALEfrat#8-VP64 was injected intraperitoneally to 9-day-old and 4-month-old YG8R mice. After 1 month, the heart, muscle and liver were removed and their FXN mRNA and FXN protein were analyzed. The results show that the AAV9_3XFLAG-TALEfrat#8-VP64 increased the FXN mRNA and FXN protein in the three organs studied. These results corroborate our previous in vitro studies in the FRDA human fibroblasts. Our study indicates that an AAV coding for a TALE protein coupled with a TAD may be used to increase gene expression in vivo as a possible treatment not only for FRDA but also for other haploinsufficiency diseases.

The association of cytochrome P450 genetic polymorphisms with sulfolane formation and the efficacy of a busulfan-based conditioning regimen in pediatric patients undergoing hematopoietic stem cell transplantation

Cytochrome P450 enzymes (CYPs) and flavin-containing monooxygenases (FMOs) likely have a role in the oxidation of intermediate metabolites of busulfan (Bu). In vitro studies to investigate the involvement of these enzymes are cumbersome because of the volatile nature of the intermediate metabolite tetrahydrothiophene (THT) and the lack of sensitive quantitation methods. This study explored the association between the CYP2C9, CYP2C19, CYP2B6 and FMO3 genotypes and sulfolane (Su, a water soluble metabolite of Bu) plasma levels in children undergoing hematopoietic stem cell transplantation (HSCT). The relationship between these genotypes and the effectiveness of myeloablative conditioning was also analyzed. Sixty-six children receiving an intravenous Bu-based myeloablative conditioning regimen were genotyped for common functional variant alleles in CYP2C9 (*2 and *3), CYP2C19 (*2 and *17), FMO3 (rs2266780, rs2266782 and rs1736557) and CYP2B6 (*5 and *9). The plasma levels of Bu and its metabolite Su were measured after the ninth Bu dose in a subset of 44 patients for whom plasma samples were available. The ratio of Bu to Su was considered the metabolic ratio (MR) and was compared across the genotype groups. Higher MRs were observed in CYP2C9*2 and *3 allele carriers (mean±s.d.: 7.8±3.6 in carriers vs 4.4±2.2 in non-carriers; P=0.003). An increased incidence of graft failure was observed among patients with an MR>5 compared with those with MR values <5 (20% vs 0%; P=0.02). In contrast, a significantly higher incidence of relapse and graft failure (evaluated as event-free survival) was observed in patients with malignant disease who carried CYP2B6 alleles with reduced function on both chromosomes compared with carriers of at least one normal allele (100% vs 40%; P=0.0001). These results suggest that CYP2C9 has a role in the oxidation reactions of THT and indicate that it may be possible to predict the efficacy of Bu-based myeloablative conditioning before HSCT on the basis of CYP genotypes and Bu MRs.

Invisible bleeding from clean-shave haircuts: detection with blood specific RNA markers

BACKGROUND

'Haircut-associated bleeding' is a newly recognized entity that affects at least a quarter of African men who wear shiny clean-shave ('chiskop') haircuts.

AIM

This pilot study aimed to elucidate whether invisible haircut-associated bleeding was detectable using blood specific RNA markers (16 participants, 5 with unknown HIV status) and whether surface virus could be detected using PCR from scalp swabs (of 11 known HIV-positive participants).

METHODS

Haircuts were performed professionally and scalps examined by a dermatologist to exclude injury. Serum samples for viral loads were also collected at the same time.

RESULTS

In all, 6/16 (37%) samples tested positive (>100 relative fluorescent units) for hemoglobin beta and albumin, confirming evidence of blood; of these, only 1/11 was HIV-positive but had an undetectable serum viral load. No surface HIV was detected from any scalp samples.

CONCLUSIONS

This study confirms the entity of haircut-associated bleeding but goes further to show for the first time that invisible bleeding from clean-shave haircuts is also common. Both a high serum viral load and evidence of bleeding should ideally be present prior to surface HIV detection. Future investigations for potential HIV (and hepatitis B) transmission through clean-shave haircuts are warranted but should not delay public education for disease prevention.

Infected tracheal diverticulum mimicking an aggressive mediastinal lesion on FDG PET/CT: an interesting case with review of the literature

The differential diagnosis for intense hypermetabolic mediastinal lesions on positron emission tomography (PET) could benefit from the combined morphological and metabolic information present in a fluorodeoxyglucose (FDG) PET/CT study. We report a case of an infected tracheal diverticulum mimicking an FDG-avid malignancy in a patient with a history of chronic lymphoproliferative disease. We review the literature for a systematic approach in the differential diagnosis of cystic mediastinal lesions. The embryological development of the normal tracheobronchial tree is reviewed, followed by a presentation of various congenital and acquired mediastinal lesions. The characteristic CT findings are described for each lesion and the avidity for FDG on PET is mentioned when references are available. This case emphasises that complicated benign processes should be considered in the differential diagnosis of an FDG-avid mediastinal lesion, even in subgroups of patients with significant risk factors for malignancy.

Meganucleases can restore the reading frame of a mutated dystrophin

Mutations in Duchenne muscular dystrophy (DMD) are either inducing a nonsense codon or a frameshift. Meganucleases (MGNs) can be engineered to induce double-strand breaks (DSBs) at specific DNA sequences. These breaks are repaired by homologous recombination or by non-homologous end joining (NHEJ), which results in insertions or deletions (indels) of a few base pairs. To verify whether MGNs could be used to restore the normal reading frame of a dystrophin gene with a frameshift mutation, we inserted in a plasmid coding for the dog micro-dystrophin sequences containing a MGN target. The number of base pairs in these inserted sequences changed the reading frame. One of these modified target micro-dystrophin plasmids and an appropriate MGN were then transfected in 293FT cells. The MGN induced micro-deletion or micro-insertion in the micro-dystrophin that restored dystrophin expression. MGNs also restored micro-dystrophin expression in myoblasts in vitro and in muscle fibers in vivo. The mutation of the targeted micro-dystrophin was confirmed by PCR amplification followed by digestion with the Surveyor enzyme and by cloning and sequencing of the amplicons. These experiments are thus a proof of principle that MGNs that are adequately engineered to target appropriate sequences in the human dystrophin gene should be able to restore the normal reading frame of that gene in DMD patients with an out-of-frame deletion. New MGNs engineered to target a sequence including or near nonsense mutation could also be used to delete it.

Analysis of the HLA population data (AHPD) submitted to the 15th International Histocompatibility/Immunogenetics Workshop by using the Gene[rate] computer tools accommodating ambiguous data (AHPD project report)

During the 15th International Histocompatibility and Immunogenetics Workshop (IHIWS), 14 human leukocyte antigen (HLA) laboratories participated in the Analysis of HLA Population Data (AHPD) project where 18 new population samples were analyzed statistically and compared with data available from previous workshops. To that aim, an original methodology was developed and used (i) to estimate frequencies by taking into account ambiguous genotypic data, (ii) to test for Hardy-Weinberg equilibrium (HWE) by using a nested likelihood ratio test involving a parameter accounting for HWE deviations, (iii) to test for selective neutrality by using a resampling algorithm, and (iv) to provide explicit graphical representations including allele frequencies and basic statistics for each series of data. A total of 66 data series (1-7 loci per population) were analyzed with this standard approach. Frequency estimates were compliant with HWE in all but one population of mixed stem cell donors. Neutrality testing confirmed the observation of heterozygote excess at all HLA loci, although a significant deviation was established in only a few cases. Population comparisons showed that HLA genetic patterns were mostly shaped by geographic and/or linguistic differentiations in Africa and Europe, but not in America where both genetic drift in isolated populations and gene flow in admixed populations led to a more complex genetic structure. Overall, a fruitful collaboration between HLA typing laboratories and population geneticists allowed finding useful solutions to the problem of estimating gene frequencies and testing basic population diversity statistics on highly complex HLA data (high numbers of alleles and ambiguities), with promising applications in either anthropological, epidemiological, or transplantation studies.

Attempted eradication of methicillin-resistant Staphylococcus aureus colonisation in horses on two farms

REASONS FOR PERFORMING STUDY

Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging equine and zoonotic pathogen. Infection control protocols can be used to control MRSA in human hospitals, but measures to eradicate MRSA on horse farms have not been evaluated.

OBJECTIVES

To describe an MRSA eradication programme that was used to attempt to eliminate MRSA colonisation among horses and horse personnel on 2 equine farms.

METHODS

Active surveillance cultures and infection control protocols were implemented on 2 farms with endemic MRSA.

RESULTS

Active screening and strict implementation of infection control protocols resulted in a rapid decrease in number of colonised horses on both farms. The majority of horses eliminated MRSA without antimicrobial treatment. On one farm colonisation was eradicated, while only 2 (3%) colonised horses remained on the other farm at the end of the study.

CONCLUSIONS

Although at this stage the benefit of eradication of MRSA from populations of horses and cost-benefit studies have not been established, this study illustrates that short-term eradication can be achieved with a policy of segregation, enhanced infection control precautions and repeated testing of groups of animals.

POTENTIAL RELEVANCE

Infection control practices should form the basis of MRSA control. Antimicrobial therapy does not appear to be required for eradication of MRSA colonisation in horses and control of MRSA on farms. In appropriate circumstances, these methods may be useful for controlling the spread of this potentially serious pathogen.

Volume quantification by fuzzy logic modelling in freehand ultrasound imaging

INTRODUCTION

Many algorithms exist for 3D reconstruction of data from freehand 2D ultrasound slices. These methods are based on interpolation techniques to fill the voxels from the pixels. For quantification purposes, segmentation is involved to delineate the structure of interest. However, speckle and partial volume effect errors can affect quantification.

OBJECTIVE

This study aimed to assess the effect of the combination of a fuzzy model and 3D reconstruction algorithms of freehand ultrasound images on these errors.

METHODS

We introduced a fuzzification step to correct the initial segmentation, by weighting the pixels by a distribution function, taking into account the local gray levels, the orientation of the local gradient, and the local contrast-to-noise ratio. We then used two of the most wide-spread reconstruction algorithms (pixel nearest neighbour (PNN) and voxel nearest neighbour (VNN)) to interpolate and create the volume of the structure. Finally, defuzzification was used to estimate the optimal volume.

VALIDATION

B-scans were acquired using 5 MHz and 8 MHz ultrasound probes on ultrasound tissue-mimicking phantoms. Quantitative evaluation of the reconstructed structures was done by comparing the method output to the real volumes. Comparison was also done with classical PNN and VNN algorithms.

RESULTS

With the fuzzy model quantification errors were less than 4.3%, whereas with classical algorithms, errors were larger (10.3% using PNN, 17.2% using VNN). Furthermore, for very small structures (0.5 cm(3)), errors reached 24.3% using the classical VNN algorithm, while they were about 9.6% with the fuzzy VNN model.

CONCLUSION

These experiments prove that the fuzzy model allows volumes to be determined with better accuracy and reproducibility, especially for small structures (<3 cm(3)).