Emergence of a CD4+CD28- granzyme B+, cytomegalovirus-specific T cell subset after recovery of primary cytomegalovirus infection

Cytotoxic CD4(+)CD28(-) T cells form a rare subset in human peripheral blood. The presence of CD4(+)CD28(-) cells has been associated with chronic viral infections, but how these particular cells are generated is unknown. In this study, we show that in primary CMV infections, CD4(+)CD28(-) T cells emerge just after cessation of the viral load, indicating that infection with CMV triggers the formation of CD4(+)CD28(-) T cells. In line with this, we found these cells only in CMV-infected persons. CD4(+)CD28(-) cells had an Ag-primed phenotype and expressed the cytolytic molecules granzyme B and perforin. Importantly, CD4(+)CD28(-) cells were to a large extent CMV-specific because proliferation was only induced by CMV-Ag, but not by recall Ags such as purified protein derivative or tetanus toxoid. CD4(+)CD28(-) cells only produced IFN-gamma after stimulation with CMV-Ag, whereas CD4(+)CD28(+) cells also produced IFN-gamma in response to varicella-zoster virus and purified protein derivative. Thus, CD4(+)CD28(-) T cells emerge as a consequence of CMV infection.     

The size and phenotype of virus-specific T cell populations is determined by repetitive antigenic stimulation and environmental cytokines

Based on the expression of the TNFR SFP CD27, two Ag-primed CD8(+) T cell subsets can be discerned in the circulation of healthy individuals: CD27(+) T cells that produce a variety of cytokines but do not display immediate cytolytic activity; and cytotoxic CD27(-) T cells, which secrete only IFN-gamma and TNF-alpha. The mechanism that controls the generation of these different phenotypes is unknown. We show that CMV reactivation not only increases the number of virus-specific T cells but also induces their transition from a CD27(+) to a CD27(-) phenotype. In support of a relation between pool size and phenotype in a cohort of latently infected individuals, the number of Ag-specific CD27(-) CD8(+) T cells was found to be linearly related to the total number of CMV-specific CD8(+) T cells. In vitro studies revealed that the acquisition of the CD27(-) phenotype on CMV-specific T cells depended on the interaction of CD27 with its cellular ligand, CD70. Expression of CD70 was proportional to the amount of antigenic stimulation and blocked by the CD4(+) T cell-derived cytokine IL-21. Thus, induction of CD70, which may vary in distinct viral infections, appears to be a key factor in determining the size and phenotype of the CMV-specific T cell population in latently infected individuals.     

Microhabitat suitability as a tool to improve the success rate of a translocation or reintroduction,case‐study of the bullhead (Cottus perifretum) in Flanders,Belgium

Microhabitat suitability models are useful tools to enhance the reintroduction success of fish. Since 2008, a translocation and reintroduction program has been carried out in Flanders to prevent substantial loss of genetic variability in the Cottus perifretum (bullhead) population, and to meet the goals set by the Habitat Directive. To this end, habitat suitability of potential headstreams was assessed on a macrohabitat and microhabitat scale prior to the reintroduction. On a macrohabitat scale, water quality, habitat structure, food availability, and fish community were screened. Based on microhabitat models for bullhead in the summer period, microhabitat suitability was assessed in headstreams where macrohabitat characteristics showed a high potential for success. Both macro‐ and microhabitat assessment showed that reintroduction of bullheads in the Nellebeek, Bruelbeek, and Mollendaalbeek would most likely lead to self‐sustaining populations. For the Sint‐Annabeek, the microhabitat suitability model, considering depth and stream velocity, estimates that 7.5–9.5% of the headstream is suitable for bullhead. However, when substratum is taken into account, the microhabitat suitability index shows that only 4.3–5.8% of the brook is suitable. The current habitat quality and quantity in the Sint‐Annabeek is estimated to support a mean total population of 812 bullheads. However, the microhabitat suitability can be substantially improved by the artificial deposition of medium‐sized gravel (5–50 mm) and large gravel (50–100 mm). By doing so, the mean estimated population size could increase up to 1,330 individuals. Our results show that habitat improvement is necessary prior to the reintroduction of bullheads in the Sint‐Annabeek.     

Mitochondrial phylogeny of African wood mice, genus Hylomyscus (Rodentia, Muridae): implications for their taxonomy and biogeography

This paper investigates the usefulness of two mitochondrial genes (16S rRNA and cytochrome b) to solve taxonomical difficulties within the genus Hylomyscus and to infer its evolutionary history. Both genes proved to be suitable molecular markers for diagnosis of Hylomyscus species. Nevertheless the resolving powers of these two genes differ, and with both markers (either analyzed singly or in combination), some nodes remain unresolved. This is probably related to the fact that the species emerged during a rapid diversification event that occurred 2-6 Myr ago (4-5 Myr ago for most divergence events). Our molecular data support the recognition of an "aeta" group, while the "alleni" and "parvus" groups are not fully supported. Based on tree topology and genetic divergence, two taxa generally recognized as subspecies should be elevated at the species level (H. simus and H. cf kaimosae). H. stella populations exhibit ancient haplotype segregation that may represent currently unrecognized allopatric species. The existence of cryptic species within H. parvus is questioned. Finally, three potentially new species may occur in West Central Africa. The Congo and Oubangui Rivers, as well as the Volta and Niger Rivers and/or the Dahomey gap could have formed effective barriers to Hylomyscus species dispersal, favoring their speciation in allopatry. The pronounced shifts in African climate during the late Pliocene and Miocene, which resulted in major changes in the distribution and composition of the vegetation, could have promoted speciation within the genus (refuge theory). Future reports should focus on the geographic distribution of Hylomyscus species in order to get a better understanding of the evolutionary history of the genus.     

Rer1p competes with APH-1 for binding to nicastrin and regulates gamma-secretase complex assembly in the early secretory pathway

The gamma-secretase complex, consisting of presenilin, nicastrin, presenilin enhancer-2 (PEN-2), and anterior pharynx defective-1 (APH-1) cleaves type I integral membrane proteins like amyloid precursor protein and Notch in a process of regulated intramembrane proteolysis. The regulatory mechanisms governing the multistep assembly of this "proteasome of the membrane" are unknown. We characterize a new interaction partner of nicastrin, the retrieval receptor Rer1p. Rer1p binds preferentially immature nicastrin via polar residues within its transmembrane domain that are also critical for interaction with APH-1. Absence of APH-1 substantially increased binding of nicastrin to Rer1p, demonstrating the competitive nature of these interactions. Moreover, Rer1p expression levels control the formation of gamma-secretase subcomplexes and, concomitantly, total cellular gamma-secretase activity. We identify Rer1p as a novel limiting factor that negatively regulates gamma-secretase complex assembly by competing with APH-1 during active recycling between the endoplasmic reticulum (ER) and Golgi. We conclude that total cellular gamma-secretase activity is restrained by a secondary ER control system that provides a potential therapeutic value.     

ENVIRONMENTAL CONDITIONS, GROWTH AND PRODUCTION OF ANADARA SENILIS (LINNAEUS, 1758) IN A SENEGAL LAGOON

Two populations of Anadara senilis were sampled periodicallyin a lagoon of Senegal. Spatfall occurs in summer during therainy season. Population density decreases from about 50, 000.m^–2,two months after spatfall, down to 6, 750 one year later and750 after 28 months. The average growth, measured on the surfaceof the shell, following the umbo rim axis is 0.8 mm per month.The main reduction in growth rate occurs in winter and endsby the deposition of a growth ring. A second growth reductiontakes place during the rainy season and sometimes ends by aweak growth ring. The microgrowth increments are conspicuousand widest during spring equinox. They are not directly relatedto the tidal cycle, but it was impossible to determine if theyhave a tidal or a daily periodicity. (Received 11 February 1990; accepted 16 July 1993)     

Induction of labour at 41 weeks or expectant management until 42 weeks: A systematic review and an individual participant data meta-analysis of randomised trials

BackgroundThe risk of perinatal death and severe neonatal morbidity increases gradually after 41 weeks of pregnancy. Several randomised controlled trials (RCTs) have assessed if induction of labour (IOL) in uncomplicated pregnancies at 41 weeks will improve perinatal outcomes. We performed an individual participant data meta-analysis (IPD-MA) on this subject.Methods and findingsWe searched PubMed, Excerpta Medica dataBASE (Embase), The Cochrane Library, Cumulative Index of Nursing and Allied Health Literature (CINAHL), and PsycINFO on February 21, 2020 for RCTs comparing IOL at 41 weeks with expectant management until 42 weeks in women with uncomplicated pregnancies. Individual participant data (IPD) were sought from eligible RCTs. Primary outcome was a composite of severe adverse perinatal outcomes: mortality and severe neonatal morbidity. Additional outcomes included neonatal admission, mode of delivery, perineal lacerations, and postpartum haemorrhage. Prespecified subgroup analyses were conducted for parity (nulliparous/multiparous), maternal age (<35/≥35 years), and body mass index (BMI) (<30/≥30). Aggregate data meta-analysis (MA) was performed to include data from RCTs for which IPD was not available.From 89 full-text articles, we identified three eligible RCTs (n = 5,161), and two contributed with IPD (n = 4,561). Baseline characteristics were similar between the groups regarding age, parity, BMI, and higher level of education. IOL resulted overall in a decrease of severe adverse perinatal outcome (0.4% [10/2,281] versus 1.0% [23/2,280]; relative risk [RR] 0.43 [95% confidence interval [CI] 0.21 to 0.91], p-value 0.027, risk difference [RD] −57/10,000 [95% CI −106/10,000 to −8/10,000], I² 0%). The number needed to treat (NNT) was 175 (95% CI 94 to 1,267).Perinatal deaths occurred in one (<0.1%) versus eight (0.4%) pregnancies (Peto odds ratio [OR] 0.21 [95% CI 0.06 to 0.78], p-value 0.019, RD −31/10,000, [95% CI −56/10,000 to −5/10,000], I² 0%, NNT 326, [95% CI 177 to 2,014]) and admission to a neonatal care unit ≥4 days occurred in 1.1% (24/2,280) versus 1.9% (46/2,273), (RR 0.52 [95% CI 0.32 to 0.85], p-value 0.009, RD −97/10,000 [95% CI −169/10,000 to −26/10,000], I² 0%, NNT 103 [95% CI 59 to 385]). There was no difference in the rate of cesarean delivery (10.5% versus 10.7%; RR 0.98, [95% CI 0.83 to 1.16], p-value 0.81) nor in other important perinatal, delivery, and maternal outcomes. MA on aggregate data showed similar results.Prespecified subgroup analyses for the primary outcome showed a significant difference in the treatment effect (p = 0.01 for interaction) for parity, but not for maternal age or BMI. The risk of severe adverse perinatal outcome was decreased for nulliparous women in the IOL group (0.3% [4/1,219] versus 1.6% [20/1,264]; RR 0.20 [95% CI 0.07 to 0.60], p-value 0.004, RD −127/10,000, [95% CI −204/10,000 to −50/10,000], I² 0%, NNT 79 [95% CI 49 to 201]) but not for multiparous women (0.6% [6/1,219] versus 0.3% [3/1,264]; RR 1.59 [95% CI 0.15 to 17.30], p-value 0.35, RD 27/10,000, [95% CI −29/10,000 to 84/10,000], I² 55%).A limitation of this IPD-MA was the risk of overestimation of the effect on perinatal mortality due to early stopping of the largest included trial for safety reasons after the advice of the Data and Safety Monitoring Board. Furthermore, only two RCTs were eligible for the IPD-MA; thus, the possibility to assess severe adverse neonatal outcomes with few events was limited.ConclusionsIn this study, we found that, overall, IOL at 41 weeks improved perinatal outcome compared with expectant management until 42 weeks without increasing the cesarean delivery rate. This benefit is shown only in nulliparous women, whereas for multiparous women, the incidence of mortality and morbidity was too low to demonstrate any effect. The magnitude of risk reduction of perinatal mortality remains uncertain. Women with pregnancies approaching 41 weeks should be informed on the risk differences according to parity so that they are able to make an informed choice for IOL at 41 weeks or expectant management until 42 weeks.Study Registration: PROSPERO CRD42020163174

Mårten Alkmark and co-workers report on a meta-analysis of randomized trials of labour induction at 41 weeks'' gestation as compared with expectant management until 42 weeks.     

The effect of temperature on Agrobacterium tumefaciens-mediated gene transfer to plants

Agrobacterium tumefaciens is generally used to achieve genetic transformation of plants. The temperatures that have been used for infection with Agrobacterium in published transformation protocols differ widely and, to our knowledge, the effect of temperature on the efficiency of T-DNA transfer to plants has not been investigated systematically. Agrobacterium tumefaciens strains harbouring a binary vector with the β-glucuronidase ( uidA ) gene and either a nopaline-, an octopine- or an agropine/ succinamopine-type helper plasmid were tested in two transformation systems at temperatures between 15 and 29°C. One system involved cocultivation of Phaseolus acutifolius callus whereas in the other system Nicotiana tabacum leaves were vacuum-infiltrated. In both situations, irrespective of the type of helper plasmid, the levels of transient uidA expression decreased notably when the temperature was raised above 22°C. Expression was low at 27°C and undetectable at 29°C. We anticipate that the efficiency of many published transformation protocols can be improved by reconsidering the factor of temperature.     

Electroporation-mediated DNA delivery to seedling tissues ofPhaseolus vulgaris L. (common bean)

Summary DNA was delivered to intact embryonic axes of the legumePhaseolus vulgaris L. through electroporation. Expression of the ß-glucuronidase reporter gene was observed in hypocotyl and epicotyl tissue in a spot-like manner. Transgene expression was high when a single pulse of 260 ms at a field strength of 225 V·cm^–1 was applied but could be achieved within a wide range of electrical conditions. Linearization of plasmid DNA greatly enhanced transient expression levels. The procedure was successful for embryonic axes of all testedP. vulgaris cultivars, for similar explants of several large-seeded leguminous species, as well as for some other tissues ofP. vulgaris.