Implementation of amotosalen plus ultraviolet A-mediated pathogen reduction for all platelet concentrates in France: Impact on the risk of transfusion-transmitted infections

BACKGROUND AND OBJECTIVES

Pathogen reduction (PR) technology may reduce the risk of transfusion-transmitted infections (TTIs), notably transfusion-transmitted bacterial infection (TTBI) associated with platelet concentrates (PCs). PR (amotosalen/UVA treatment) was implemented for all PCs transfused in France in November 2017. No bacterial detection was in place beforehand. The study aimed to assess the impact of PR PC on TTI and TTBI near-miss occurrences.

MATERIALS AND METHODS

TTI and TTBI near-miss occurrences were compared before and after 100% PR implementation. The study period ran from 2013 to 2022. Over 300,000 PCs were transfused yearly.

RESULTS

No PC-related transmission of human immunodeficiency virus, hepatitis C virus, hepatitis B virus and human T-cell lymphotropic virus was reported throughout the study period. PC-mediated hepatitis E virus and hepatitis A virus infections occurred irrespective of PR implementation. Mean PC-mediated TTBI occurrence before PR-PC implementation was 3/year (SD: 1; n = 15; 1/92,687 PC between 2013 and 2016) with a fatal outcome in two patients. Since PR implementation, one TTBI has been reported (day 4 PC, Bacillus cereus) (1/1,645,295 PC between 2018 and 2022; p < 0.001). Two PR PC quarantined because of a negative swirling test harboured bacteria: a day 6 PC in 2021 (B. cereus and Staphylococcus epidermidis) and a day 7 PC in 2022 (Staphylococcus aureus). Five similar occurrences with untreated PC were reported between 2013 and 2020.

CONCLUSION

Transfusion of 100% PR PC resulted in a steep reduction in TTBI occurrence. TTBI may, however, still occur. Pathogen-reduced PC-related TTI involving non-enveloped viruses occurs as well.

Evolutionary and ecological processes influencing chemical defense variation in an aposematic and mimetic Heliconius butterfly

Chemical defences against predators underlie the evolution of aposematic coloration and mimicry, which are classic examples of adaptive evolution. Surprisingly little is known about the roles of ecological and evolutionary processes maintaining defence variation, and how they may feedback to shape the evolutionary dynamics of species. Cyanogenic Heliconius butterflies exhibit diverse warning color patterns and mimicry, thus providing a useful framework for investigating these questions. We studied intraspecific variation in de novo biosynthesized cyanogenic toxicity and its potential ecological and evolutionary sources in wild populations of Heliconius erato along environmental gradients, in common-garden broods and with feeding treatments. Our results demonstrate substantial intraspecific variation, including detectable variation among broods reared in a common garden. The latter estimate suggests considerable evolutionary potential in this trait, although predicting the response to selection is likely complicated due to the observed skewed distribution of toxicity values and the signatures of maternal contributions to the inheritance of toxicity. Larval diet contributed little to toxicity variation. Furthermore, toxicity profiles were similar along steep rainfall and altitudinal gradients, providing little evidence for these factors explaining variation in biosynthesized toxicity in natural populations. In contrast, there were striking differences in the chemical profiles of H. erato from geographically distant populations, implying potential local adaptation in the acquisition mechanisms and levels of defensive compounds. The results highlight the extensive variation and potential for adaptive evolution in defense traits for aposematic and mimetic species, which may contribute to the high diversity often found in these systems.

Sex-specific regulation of aging in Caenorhabditis elegans

A fascinating aspect of sexual dimorphism in various animal species is that the two sexes differ substantially in lifespan. In humans, for example, women's life expectancy exceeds that of men by 3-7 years. Whether this trait can be attributed to dissimilar lifestyles or genetic (regulatory) factors remains to be elucidated. Herein, we demonstrate that in the nematode Caenorhabditis elegans, the significantly longer lifespan of hermaphrodites-which are essentially females capable of sperm production-over males is established by TRA-1, the terminal effector of the sex-determination pathway. This transcription factor directly controls the expression of daf-16/FOXO, which functions as a major target of insulin/IGF-1 signaling (IIS) and key modulator of aging across diverse animal phyla. TRA-1 extends hermaphrodite lifespan through promoting daf-16 activity. Furthermore, TRA-1 also influences reproductive growth in a DAF-16-dependent manner. Thus, the sex-determination machinery is an important regulator of IIS in this organism. These findings provide a mechanistic insight into how longevity and development are specified unequally in the two genders. As TRA-1 is orthologous to mammalian GLI (glioma-associated) proteins, a similar sex-specific mechanism may also operate in humans to determine lifespan.

Inhibition of DNA methyltransferase leads to increased genomic 5-hydroxymethylcytosine levels in hematopoietic cells

5‐Hydroxymethylcytosine (5hmC) is produced from 5‐methylcytosine (5mC) by Ten‐eleven translocation (TET) dioxygenases. The epigenetic modification 5hmC has crucial roles in both cellular development and differentiation. The 5hmC level is particularly high in the brain. While 5mC is generally associated with gene silencing/reduced expression, 5hmC is a more permissive epigenetic mark. To understand its physiological function, an easy and accurate quantification method is required. Here, we have developed a novel LC‐MS/MS‐based approach to quantify both genomic 5mC and 5hmC contents. The method is based on the liberation of nucleobases by formic acid. Applying this method, we characterized the levels of DNA methylation and hydroxymethylation in mouse brain and liver, primary hepatocytes, and various cell lines. Using this approach, we confirm that the treatment of different cell lines with the DNA methyltransferase inhibitor 5‐aza‐2′‐deoxycytidine leads to a decrease in 5mC content. This decrease was accompanied by an increase in 5hmC levels in cell lines of hematopoietic origin. Finally, we showed that ascorbate elevates the levels of 5hmC and augments the effect of 5‐aza‐2′‐deoxycytidine without significantly influencing 5mC levels.

Transcriptional regulation of the ABCC6 gene and the background of impaired function of missense disease-causing mutations

The human ATP-binding cassette family C member 6 (ABCC6) gene encodes an ABC transporter protein expressed primarily in the liver and to a lesser extent in the kidneys and the intestines. We review here the mechanisms of this restricted tissue-specific expression and the role of hepatocyte nuclear factor 4α which is responsible for the expression pattern. Detailed analyses uncovered further regulators of the expression of the gene pointing to an intronic primate-specific regulator region, an activator of the expression of the gene by binding CCAAT/enhancer-binding protein beta, which interacts with other proteins acting in the proximal promoter. This regulatory network is affected by various environmental stimuli including oxidative stress and the extracellular signal-regulated protein kinases 1 and 2 pathway. We also review here the structural and functional consequences of disease-causing missense mutations of ABCC6. A significant clustering of the missense disease-causing mutations was found at the domain–domain interfaces. This clustering means that the domain contacts are much less permissive to amino acid replacements than the rest of the protein. We summarize the experimental methods resulting in the identification of mutants with preserved transport activity but failure in intracellular targeting. These mutants are candidates for functional rescue by chemical chaperons. The results of such research can provide the basis of future allele-specific therapy of ABCC6-mediated disorders like pseudoxanthoma elasticum or the generalized arterial calcification in infancy.

Rapid turnover of DNA methylation in human cells

Recent studies demonstrated that cytosine methylation in the genome can be reversed without DNA replication by enzymatic mechanisms based on base excision-repair pathways. Both enzymatic methylation and demethylation mechanisms are active in the cell nucleus at the same time. One can hypothesize that the actual level of CpG methylation could be the result of a balance between the two antagonistic processes with a rapid turnover. In the present study, we used mass spectrometry to measure the total methyl-cytosine content of the genome in cultured human cells after short incubation with the known methyltransferase inhibitor 5-deoxy-azacytidine. A significant decrease of the DNA methylation was observed. Indeed, the inhibition of the methylation can only result in a rapid reduction of the overall methyl-cytosine level if the process of demethylation is simultaneous. These observations suggest that the enzymatic mechanisms responsible of the opposing reactions of DNA methylation and demethylation act simultaneously and may result in a continuous and rapid turnover of methylated cytosines. This conclusion is supported by the observation that 5-deoxy-azacytidine was incorporated in the genomic DNA of non-dividing cells and could be detected as soon as after two hours of incubation, hence providing a mechanistic explanation to the inhibition of methyltransferases. The observations are compatible with the idea that the enzymatic mechanisms that bring together of the opposing reactions of DNA methylation and demethylation act simultaneously and may result in a continuous and unsuspected rapid turnover of DNA methylation. This conclusion is at odds with the generally accepted view of high stability of cytosine methylation where the role of enzymatic demethylation is considered as limited to some special situations such as transcription. It places DNA methylation in the same category as other epigenetic modifications with covalent modifications dynamically added to and removed from the chromatin with high turnover rate.

ABCC6 expression is regulated by CCAAT/enhancer-binding protein activating a primate-specific sequence located in the first intron of the gene

Pseudoxanthoma elasticum (PXE), a rare recessive genetic disease causing skin, eye, and cardiovascular lesions, is characterized by the calcification of elastic fibers. The disorder is due to loss-of-function mutations of the ABCC6 gene, but the pathophysiology of the disease is still not understood. Here we investigated the transcriptional regulation of the gene, using DNase I hypersensitivity assay followed by luciferase reporter gene assay. We identified three DNase I hypersensitive sites (HSs) specific to cell lines expressing ABCC6. These HSs are located in the proximal promoter and in the first intron of the gene. We further characterized the role of the HSs by luciferase assay and demonstrated the transcriptional activity of the intronic HS. We identified the CCAAT/enhancer-binding protein β (C/EBPβ) as a factor binding the second intronic HS by chromatin immunoprecipitation and corroborated this finding by luciferase assays. We also showed that C/EBPβ interacts with the proximal promoter of the gene. We propose that C/EBPβ forms a complex with other regulatory proteins including the previously identified regulatory factor hepatocyte nuclear factor 4α (HNF4α). This complex would account for the tissue-specific expression of the gene and might serve as a metabolic sensor. Our results point toward a better understanding of the physiological role of ABCC6.

A homogeneous enzyme immunoassay with avidin-ligand conjugate as the enzyme-modulator

A homogeneous enzyme immunoassay (EIA) based on the immunomodulation of an avidin-ligand conjugate and the inhibition of pyruvate carboxylase is described. The conjugation of the ligand, 5,5-diphenylhydantoin (DPH), to avidin does not affect avidin's capacity to bind biotin or inhibit pyruvate carboxylase. The DPH-avidin conjugate and free DPH were shown to compete for a limited number of antibody sites. The interaction of anti-DPH with the DPH-avidin conjugate sterically inhibited enzyme inactivation. Enzyme activity was correlated with DPH concentrations in the therapeutic range found in serum.