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Étude du goulot d’étranglement dans la transmission mère-enfant du virus de l’hépatite C
Get PDFLa transmission mère-enfant (TME) du virus de l’hépatite C (VHC) est la première cause d’acquisition de l’infection chez les enfants des pays développés. Celle-ci prend place dans <10% des cas. Toutefois, dans le cas d’une coinfection maternelle avec le virus de l’immunodéficience de type 1 (VIH-1), ce taux est accru alors qu’il n’existe aucune intervention préventive de la TME du VHC. Le VHC arbore une diversité importante qui est le résultat d’une réplication exempte de mécanisme de correction. Il est donc retrouvé chez son hôte sous la forme d’un spectre de virions génétiquement apparentés mais différents qu’on appelle quasiespèce. Lorsque le VHC est transmis entre adultes, seulement un nombre limité de variantes sont responsables de l’infection, c’est ce qu’on appelle un goulot d’étranglement génétique. L’existence d’un tel profil de transmission lors de la TME du VHC restait, jusqu’à maintenant, à confirmer. En se basant sur la détection par RT-PCR de la virémie à la naissance, la TME du VHC est réputée prendre place in utero et peripartum, une dynamique de transmission qui reste à démontrer.
Ici, nous rapportons une analyse longitudinale de la TME du VHC par séquençage de nouvelle génération chez 5 paires mère-enfant dont 3 mères sont également coinfectées avec le VIH-1. L’analyse de l’identité des variantes virales basée sur la séquence nucléotidique des régions hypervariables 1-2 de la glycoprotéine E2 (positions 1491-1787 de l’isolat H77) révèle qu’un nombre limité de variantes virales sont transmises de la mère à l’enfant lorsque la mère est seulement infectée par le VHC (n = 1-4 variantes transmises). Dans le cas de la coinfection maternelle avec le VIH-1, ce nombre est toutefois drastiquement plus important (n = 111-118). La détection de variantes retrouvées chez la mère au deuxième trimestre et l’enfant mais non détectées subséquemment chez la mère témoigne que la TME du VHC peut prendre place aussi tôt que lors du deuxième trimestre de grossesse. Finalement, nous montrons que la dynamique d’infection chez l’enfant implique une augmentation transitoire de la virémie concomitante avec une perte de diversité de la quasiespèce. Dans l’ensemble ces résultats sont les premiers à démontrer directement l’existence d’un goulot d’étranglement lors de la TME du VHC. Celui-ci serait moins restringent dans le cas de la coinfection maternelle avec le VIH-1. Cette transmission peut prendre place aussi tôt que lors du deuxième trimestre de grossesse et il semblerait qu’un spectre limité de variantes soit responsable pour l’établissement de l’essentiel de la production virale chez le jeune enfant.Mother-to-child transmission (MTCT) of hepatitis C virus (HCV) represents the first cause of infection in children of developed countries. MTCT of HCV may take place in <10% when the mother is solely infected with HCV. However, maternal coinfection with type 1 human immunodeficiency virus (HIV-1) leads to a drastic increase of this rate. Besides, there is no mean of prevention of MTCT of HCV.
HCV replication leads to a prominent variability due to the absence of correction mechanism of its RNA-dependent RNA polymerase. Consequently, it is retrieved in its host as a swarm of genetically closely related but different variants named quasispecies. When HCV transmission occurs between adults, only a very limited number of variants are responsible for the infection. This phenomenon is called a genetic bottleneck and whether it exists during MTCT of HCV is to confirm. Based on the detection by RT-PCR of HCV’s RNA at birth, MTCT is believed to take place both in utero and peripartum. Nevertheless, such dynamics of MTCT of HCV have never been demonstrated directly.
Here we report, using next generation sequencing, a longitudinal analysis of MTCT of HCV in 5 mother-child pairs, in 3 cases the mother was also infected with HIV-1. Identity analysis based on nucleotide sequence of the glycoprotein E2 hypervariable regions 1-2 (positions 1491-1787 of the isolate H77) reveals that a tight genetic bottleneck exists during MTCT of HCV (n= 1-4 variants transmitted) when the mother is only infected with HCV. However, in the case of maternal coinfection with HIV-1, this number is radically increased (n = 111-118). Also, the detection of variants shared between mother and child that are only present at the 2nd trimester of pregnancy in the mother but not found after suggest that MTCT of HCV can take place as early as the 2nd trimester of gestation. Lastly, we show that the dynamics of the establishment of the infection in the young child involve a transitional increase of the viremia concomitant with reduced diversity of HCV quasispecies. Together, these results show the first direct evidence of a genetic bottleneck occurring during MTCT of HCV. This bottleneck appears to be much less constricted when the mother is coinfected with HIV-1 and HCV. It appears possible that the MTCT can take place as early as the second trimester of pregnancy and that a limited number of variants may be responsible for the essential of the viral production during early childhood
Étude du goulot d’étranglement dans la transmission mère-enfant du virus de l’hépatite C
Get PDFLa transmission mère-enfant (TME) du virus de l’hépatite C (VHC) est la première cause d’acquisition de l’infection chez les enfants des pays développés. Celle-ci prend place dans <10% des cas. Toutefois, dans le cas d’une coinfection maternelle avec le virus de l’immunodéficience de type 1 (VIH-1), ce taux est accru alors qu’il n’existe aucune intervention préventive de la TME du VHC. Le VHC arbore une diversité importante qui est le résultat d’une réplication exempte de mécanisme de correction. Il est donc retrouvé chez son hôte sous la forme d’un spectre de virions génétiquement apparentés mais différents qu’on appelle quasiespèce. Lorsque le VHC est transmis entre adultes, seulement un nombre limité de variantes sont responsables de l’infection, c’est ce qu’on appelle un goulot d’étranglement génétique. L’existence d’un tel profil de transmission lors de la TME du VHC restait, jusqu’à maintenant, à confirmer. En se basant sur la détection par RT-PCR de la virémie à la naissance, la TME du VHC est réputée prendre place in utero et peripartum, une dynamique de transmission qui reste à démontrer.
Ici, nous rapportons une analyse longitudinale de la TME du VHC par séquençage de nouvelle génération chez 5 paires mère-enfant dont 3 mères sont également coinfectées avec le VIH-1. L’analyse de l’identité des variantes virales basée sur la séquence nucléotidique des régions hypervariables 1-2 de la glycoprotéine E2 (positions 1491-1787 de l’isolat H77) révèle qu’un nombre limité de variantes virales sont transmises de la mère à l’enfant lorsque la mère est seulement infectée par le VHC (n = 1-4 variantes transmises). Dans le cas de la coinfection maternelle avec le VIH-1, ce nombre est toutefois drastiquement plus important (n = 111-118). La détection de variantes retrouvées chez la mère au deuxième trimestre et l’enfant mais non détectées subséquemment chez la mère témoigne que la TME du VHC peut prendre place aussi tôt que lors du deuxième trimestre de grossesse. Finalement, nous montrons que la dynamique d’infection chez l’enfant implique une augmentation transitoire de la virémie concomitante avec une perte de diversité de la quasiespèce. Dans l’ensemble ces résultats sont les premiers à démontrer directement l’existence d’un goulot d’étranglement lors de la TME du VHC. Celui-ci serait moins restringent dans le cas de la coinfection maternelle avec le VIH-1. Cette transmission peut prendre place aussi tôt que lors du deuxième trimestre de grossesse et il semblerait qu’un spectre limité de variantes soit responsable pour l’établissement de l’essentiel de la production virale chez le jeune enfant.Mother-to-child transmission (MTCT) of hepatitis C virus (HCV) represents the first cause of infection in children of developed countries. MTCT of HCV may take place in <10% when the mother is solely infected with HCV. However, maternal coinfection with type 1 human immunodeficiency virus (HIV-1) leads to a drastic increase of this rate. Besides, there is no mean of prevention of MTCT of HCV.
HCV replication leads to a prominent variability due to the absence of correction mechanism of its RNA-dependent RNA polymerase. Consequently, it is retrieved in its host as a swarm of genetically closely related but different variants named quasispecies. When HCV transmission occurs between adults, only a very limited number of variants are responsible for the infection. This phenomenon is called a genetic bottleneck and whether it exists during MTCT of HCV is to confirm. Based on the detection by RT-PCR of HCV’s RNA at birth, MTCT is believed to take place both in utero and peripartum. Nevertheless, such dynamics of MTCT of HCV have never been demonstrated directly.
Here we report, using next generation sequencing, a longitudinal analysis of MTCT of HCV in 5 mother-child pairs, in 3 cases the mother was also infected with HIV-1. Identity analysis based on nucleotide sequence of the glycoprotein E2 hypervariable regions 1-2 (positions 1491-1787 of the isolate H77) reveals that a tight genetic bottleneck exists during MTCT of HCV (n= 1-4 variants transmitted) when the mother is only infected with HCV. However, in the case of maternal coinfection with HIV-1, this number is radically increased (n = 111-118). Also, the detection of variants shared between mother and child that are only present at the 2nd trimester of pregnancy in the mother but not found after suggest that MTCT of HCV can take place as early as the 2nd trimester of gestation. Lastly, we show that the dynamics of the establishment of the infection in the young child involve a transitional increase of the viremia concomitant with reduced diversity of HCV quasispecies. Together, these results show the first direct evidence of a genetic bottleneck occurring during MTCT of HCV. This bottleneck appears to be much less constricted when the mother is coinfected with HIV-1 and HCV. It appears possible that the MTCT can take place as early as the second trimester of pregnancy and that a limited number of variants may be responsible for the essential of the viral production during early childhood
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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