Utilization of a deoxynucleoside diphosphate substrate by HIV reverse transcriptase

Background: Deoxynucleoside triphosphates (dNTPs) are the normal substrates for DNA sysnthesis is catalyzed by polymerases such as HIV-1 reverse transcriptase (RT). However, substantial amounts of deoxynucleoside diphosphates (dNDPs) are also present in the cell. Use of dNDPs in HIV-1 DNA sysnthesis could have significant implications for the efficacy of nucleoside RT inhibitors such as AZT which are first line therapeutics fro treatment of HIV infection. Our earlier work on HIV-1 reverse transcriptase (RT) suggested that the interaction between the γ phosphate of the incoming dNTP and RT residue K65 in the active site is not essential for dNTP insertion, implying that this polymerase may be able to insert dNPs in addition to dNTPs. Methodology/Principal Findings: We examined the ability of recombinant wild type (wt) and mutant RTs with substitutions at residue K65 to utilize a dNDP substrate in primer extension reactions. We found that wild type HIV-1 RT indeed catalyzes incorporation of dNDP substrates whereas RT with mutations of residue K645 were unable to catalyze this reaction. Wild type HIV-1 RT also catalyzed the reverse reaction, inorganic phosphate-dependent phosphorolysis. Nucleotide-mediated phosphorolytic removal of chain-terminating 3′-terminal nucleoside inhibitors such as AZT forms the basis of HIV-1 resistance to such drugs, and this removal is enhanced by thymidine analog mutations (TAMs). We found that both wt and TAM-containing RTs were able to catalyze Pi-mediated phosphorolysis of 3′-terminal AZT at physiological levels of Pi with an efficacy similar to that for ATP-dependent AZT-excision. Conclusion: We have identified two new catalytic function of HIV-1 RT, the use of dNDPs as substrates for DNA synthesis, and the use of Pi as substrate for phosphorolytic removal of primer 3′-terminal nucleotides. The ability to insert dNDPs has been documented for only one other DNA polymerase The RB69 DNA polymerase and the reverse reaction employing inorganic phosphate has not been documented for any DNA polymerase. Importantly, our results show that Pi-mediated phosphorolysis can contribute to AZT resistance and indicates that factors that influence HIV resistance to AZT are more complex than previously appreciated. © 2008 Garforth et al

Peptides Derived from HIV-1 Integrase that Bind Rev Stimulate Viral Genome Integration

The human immunodeficiency virus type 1 (HIV-1) integrase protein (IN), catalyzes the integration of viral DNA into the host cell genome. IN catalyzes the first step of the integration process, namely the 3′-end processing in which IN removes a pGT dinucleotide from the 3′ end of each viral long terminal repeat (LTR). Following nuclear import of the viral preintegration complex, the host chromosomal DNA becomes accessible to the viral cDNA and the second step of the integration process, namely the strand-transfer step takes place. This ordered sequence of events, centered on integration, is mandatory for HIV replication. assay system, we show that INr-1 and INr-2 are able to abrogate the inhibitory effects exerted by Rev and Rev-derived peptides on integrase activity. Both INr-1 and INr-2 were found to be cell-permeable and nontoxic, allowing a study of their effect in HIV-1-infected cultured cells. Interestingly, both INr peptides stimulated virus infectivity as estimated by production of the viral P24 protein, as well as by determination of the appearance of newly formed virus particles. Furthermore, kinetics studies revealed that the cell-permeable INr peptides enhance the integration process, as was indeed confirmed by direct determination of viral DNA integration by real-time PCR.The results of the present study raise the possibility that in HIV-infected cells, the Rev protein may be involved in the integration of proviral DNA by controlling/regulating the activity of the integrase. Release from such inhibition leads to stimulation of IN activity and multiple viral DNA integration events

K70Q Adds High-Level Tenofovir Resistance to “Q151M Complex” HIV Reverse Transcriptase through the Enhanced Discrimination Mechanism

HIV-1 carrying the “Q151M complex” reverse transcriptase (RT) mutations (A62V/V75I/F77L/F116Y/Q151M, or Q151Mc) is resistant to many FDA-approved nucleoside RT inhibitors (NRTIs), but has been considered susceptible to tenofovir disoproxil fumarate (TFV-DF or TDF). We have isolated from a TFV-DF-treated HIV patient a Q151Mc-containing clinical isolate with high phenotypic resistance to TFV-DF. Analysis of the genotypic and phenotypic testing over the course of this patient's therapy lead us to hypothesize that TFV-DF resistance emerged upon appearance of the previously unreported K70Q mutation in the Q151Mc background. Virological analysis showed that HIV with only K70Q was not significantly resistant to TFV-DF. However, addition of K70Q to the Q151Mc background significantly enhanced resistance to several approved NRTIs, and also resulted in high-level (10-fold) resistance to TFV-DF. Biochemical experiments established that the increased resistance to tenofovir is not the result of enhanced excision, as K70Q/Q151Mc RT exhibited diminished, rather than enhanced ATP-based primer unblocking activity. Pre-steady state kinetic analysis of the recombinant enzymes demonstrated that addition of the K70Q mutation selectively decreases the binding of tenofovir-diphosphate (TFV-DP), resulting in reduced incorporation of TFV into the nascent DNA chain. Molecular dynamics simulations suggest that changes in the hydrogen bonding pattern in the polymerase active site of K70Q/Q151Mc RT may contribute to the observed changes in binding and incorporation of TFV-DP. The novel pattern of TFV-resistance may help adjust therapeutic strategies for NRTI-experienced patients with multi-drug resistant (MDR) mutations

Vers une professionnalisation des fonctions hydrauliques des périmètres irrigués en Afrique de l’Ouest

 Lors du transfert des aménagements hydro agricoles aux usagers les agriculteurs se sont vus confier des missions hydrauliques qu’ils n’avaient pas toujours la capacité d’assurer. De nombreux aménagements ont ainsi subi un abandon, partiel ou total, du fait d’un déficit de maintenance des infrastructures ou de problèmes récurrents de pompage et de distribution de l’eau.  L’analyse de onze périmètres nuance cette vision pessimiste de l’irrigation en Afrique de l’Ouest. Elle montre en premier lieu que sur les aménagements étudiés, les coopératives effectuent des provisions importantes pour l’amortissement de leur équipement de pompage. Plusieurs d’entre elles ont ainsi déjà procédé de façon autonome au renouvellement de leur système de pompage. Par ailleurs, certaines coopératives parviennent à assurer un approvisionnement en eau proche des besoins des cultures, à un coût satisfaisant, tout en maintenant une certaine équité de distribution à l’échelle du périmètre. Enfin, s’il est vrai qu’un déficit de maintenance est constaté sur la plupart des périmètres les coopérateurs ont de plus en plus conscience de la nécessité d’un entretien de qualité et adaptent leurs pratiques en conséquence.  Des progrès restent à réaliser pour assurer une irrigation efficiente productive et durable. L’expérience de certains périmètres montre que la solution repose en partie sur la professionnalisation des fonctions hydrauliques du périmètre. L’intervention d’experts permet d’apporter les compétences que ne possèdent pas les irrigants sur des aspects divers de la gestion de l’eau : pompage, distribution entretien des infrastructures gestion de la redevance... Elle peut prendre la forme d’un appui conseil ponctuel ou d’une totale délégation du service de l’eau

NMR and biochemical characterization of recombinant human tRNA(Lys)3 expressed in Escherichia coli: identification of posttranscriptional nucleotide modifications required for efficient initiation of HIV-1 reverse transcription.

Reverse transcription of HIV-1 viral RNA uses human tRNA(Lys)3 as a primer. Some of the modified nucleotides carried by this tRNA must play a key role in the initiation of this process, because unmodified tRNA produced in vitro is only marginally active as primer. To provide a better understanding of the contribution of base modifications in the initiation complex, we have designed a recombinant system that allows tRNA(Lys)3 expression in Escherichia coli. Because of their high level of overexpression, some modifications are incorporated at substoichiometric levels. We have purified the two major recombinant tRNA(Lys)3 subspecies, and their modified nucleotide contents have been characterized by a combination of NMR and biochemical techniques. Both species carry psis, Ds, T, t6A, and m7G. Differences are observed at position 34, within the anticodon. One fraction lacks the 5-methylaminomethyl group, whereas the other lacks the 2-thio group. Although the s2U34-containing recombinant tRNA is a less efficient primer, it presents most of the characteristics of the mammalian tRNA. On the other hand, the mnm5U34-containing tRNA has a strongly reduced activity. Our results demonstrate that the modifications that are absent in E. coli (m2G10, psi27, m5C48, m5C49, and m1A58) as well as the mnm5 group at position 34 are dispensable for initiation of reverse transcription. In contrast, the 2-thio group at position 34 seems to play an important part in this process

Bacillus cereus infection in neonates and the absence of evidence for the role of banked human milk: Case reports and literature review

International audienceBACKGROUND: Banked human milk (BHM) has inherent infectious risks, even when pasteurized. Because of the ubiquity of Bacillus cereus in the environment and its ability to resist the Holder pasteurization process, there is a concern that BHM might lead to severe B. cereus infections. OBJECTIVE: We reviewed observed and published cases to determine the potential causal role of BHM as the source of these infections. METHODS: Two infants in the province of Quebec (Canada) developed a B. cereus neonatal infection, and both had received BHM. We conducted bacteriological studies to compare clinical isolates and those found in these cases. RESULTS: After extended culture of BHM retention lots, B. cereus was found to have been involved in batches related to the first case. However, molecular typing showed that the strain was different from the clinical isolate, therefore excluding BHM as the source of contamination. In the second case, a Brevibacillus spp was isolated, a species distinct from the clinical isolate. CONCLUSION: Based on these cases and others reported in the literature, a causal link between B. cereus contaminated BHM and preterm neonatal infection has never been documented. Therefore, the risk that BHM can cause this infection remains theoretical. Given the widespread presence of B. cereus in the hospital environment and its capacity to resist standard cleaning procedures, it seems likely that airborne or direct or indirect contact are the main sources of most, if not all, cases of severe B. cereus neonatal infections, even in babies exposed to BHM

Supplementary Material for: Breastfeeding success and newborn health before and during the COVID-19 pandemic: a single centre comparative study

Introduction: Due to the SARS-CoV-2 pandemic, adjustments in patient and visitor traffic were made in hospitals to limit viral exposure. The primary objective of our study was to compare the breastfeeding success of healthy newborns in a maternity ward during the 2020 lockdown period compared with the same period in the previous year. Material and methods: single-center comparative study based on prospectively collected data. All neonates born alive, from a single pregnancy, and with a gestational age greater than 36 weeks were considered for this study. Results: 309 infants born in 2020 and 330 born in 2019 were included. Among women who desired to exclusively breastfeed, the rate of exclusive breastfeeding at discharge from the maternity ward was higher in 2020 than in 2019 (85% vs. 79%; p=0.078). After logistic regression analysis adjusted for potential confounders (i.e., maternal BMI, parity, mode of delivery, gestational age, and size at birth), study period remained significantly and independently associated with exclusive breastfeeding at discharge(OR [95%IC] = 1.645 [1.005; 2.694]; p=0.046). Newborns born in 2020 were less likely to have weight loss ≥10% than those born in 2019 (OR [95%IC] = 2.596 [1.148; 5.872]; p=0.017) but had similar need for phototherapy (p=0.41). Conclusion: The success of exclusive breastfeeding during the 2020 lockdown period was increased compared with the same period in 2019

It's time to change the recommendations on COVID-19 and human milk donations

International audienceNo abstract availabl

Current debates on immunology of preeclampsia. Report of the sixth international workshop of Reunion Island (Indian Ocean, December 2008)

Les troubles hypertensifs de la grossesse (THG) représentent globalement 10 % des naissances humaines, et leur complication majeure, la prééclampsie, 3 à 5 %. L’étiologie de ces THG reste toujours controversée ; cependant des avancées majeures ont eu lieu ces dernieres 25 années. Le « sixième colloque international d’immunologie de la reproduction, de l’immunotolérance et de l’immunologie de la prééclampsie » 2008 a fêté cette année son dixième anniversaire. Durant cette décennie, ces six colloques bisannuels ont largement contribué à nourrir le débat entre immunologistes, cliniciens, anthropologues et spécialistes des maladies cardiovasculaires. Le défaut de l’invasion trophoblastique profonde obligatoire chez les humains rencontrée dans la prééclampsie, le retard de croissance intra-utérin, et dans une certaine mesure dans la menace d’accouchement prématuré n’ont été compris qu’à la fin des années 1970. Dans le même temps, des études cliniques et épidémiologiques à la fin du xxe siècle ont permis de réaliser que la prééclampsie « maladie des primipares » pouvait en fait être une maladie de la première grossesse au niveau d’un couple. Parmi les avancées significatives, l’immunologie de la reproduction a fait des bonds de géant dans la dernière décennie. Ce papier relate les étapes majeures franchies dans la compréhension de cette pathologie et met en lumière l’intérêt de ces travaux immunologiques et des nouveaux concepts afférents. Il semble, en ce début de xxie siècle que nous soyons plus près que jamais de comprendre l’étiologie de cette énigme obstétricale. Dans ce domaine, l’immunologie de la reproduction sera sans doute un des interlocuteurs majeurs.Hypertensive disorders of pregnancy (HDP) represent globally 10% of human births and their major complication, preeclampsia, 3 to 5%. The etiology of these HDP remains still uncertain, however major advances have been made these last 25 years. The Sixth International Workshop on Reproductive Immunology, Immunological Tolerance and Immunology of Preeclampsia 2008 celebrated its 10th Anniversary in Reunion-island (French overseas Department in the Indian Ocean). Over this decade, these six workshops have contributed extensively to immunological, epidemiological, anthropological and even vascular debates. The defect of trophoblastic invasion encountered in preeclampsia, intra-uterine growth retardation and to some extend also preterm labour has been understood only at the end of the 1970's. On the other hand, clinical and epidemiological findings at the end of the 20th century permitted to apprehend that “preeclampsia disease of primiparae” may in fact well be the disease of first pregnancies at the level of human couples. Among the important advances, immunology of reproduction is certainly the topic where knowledge has literally exploded in the last decade. This paper relates some major steps in comprehension of this disease and focuses on the interest to follow these immunological works and their new concepts. It seems, at the beginning of the 21st century, that we are possibly closer than ever to understand the etiology of this obstetrical enigma. In this quest, the immunology of reproduction will certainly come out as one of the main players