Human immunodeficiency virus-specific CD8+ T-cell activity is detectable from birth in the majority of in utero-infected infants

Human immunodeficiency virus (HIV)-infected infants in sub-Saharan Africa typically progress to AIDS or death by 2 years of life in the absence of antiretroviral therapy. This rapid progression to HIV disease has been related to immaturity of the adaptive immune response in infants. We screened 740 infants born to HIV-infected mothers and tracked development and specificity of HIV-specific CD8⁺ T-cell responses in 63 HIV-infected infants identified using gamma interferon enzyme-linked immunospot assays and intracellular cytokine staining. Forty-four in utero-infected and 19 intrapartum-infected infants were compared to 45 chronically infected children >2 years of age. Seventy percent (14 of 20) in utero-infected infants tested within the first week of life demonstrated HIV-specific CD8⁺ T-cell responses. Gag, Pol, and Nef were the principally targeted regions in chronic pediatric infection. However, Env dominated the overall response in one-third (12/36) of the acutely infected infants, compared to only 2/45 (4%) of chronically infected children (P = 0.00083). Gag-specific CD4⁺ T-cell responses were minimal to undetectable in the first 6 months of pediatric infection. These data indicate that failure to control HIV replication in in utero-infected infants is not due to an inability to induce responses but instead suggest secondary failure of adaptive immunity in containing this infection. Moreover, the detection of virus-specific CD8⁺ T-cell responses in the first days of life in most in utero-infected infants is encouraging for HIV vaccine interventions in infants.     

The hr1 and fusion peptide regions of the subgroup B avian sarcoma and leukosis virus envelope glycoprotein influence low pH-dependent membrane fusion

The avian sarcoma and leukosis virus (ASLV) envelope glycoprotein (Env) is activated to trigger fusion by a two-step mechanism involving receptor-priming and low pH fusion activation. In order to identify regions of ASLV Env that can regulate this process, a genetic selection method was used to identify subgroup B (ASLV-B) virus-infected cells resistant to low pH-triggered fusion when incubated with cells expressing the cognate TVB receptor. The subgroup B viral Env (envB) genes were then isolated from these cells and characterized by DNA sequencing. This led to identification of two frequent EnvB alterations which allowed TVB receptor-binding but altered the pH-threshold of membrane fusion activation: a 13 amino acid deletion in the host range 1 (hr1) region of the surface (SU) EnvB subunit, and the A32V amino acid change within the fusion peptide of the transmembrane (TM) EnvB subunit. These data indicate that these two regions of EnvB can influence the pH threshold of fusion activation.     

Genome sequence of Thermotoga sp. strain RQ2, a hyperthermophilic bacterium isolated from a geothermally heated region of the seafloor near Ribeira Quente, the Azores

Thermotoga sp. strain RQ2 is probably a strain of Thermotoga maritima. Its complete genome sequence allows for an examination of the extent and consequences of gene flow within Thermotoga species and strains. Thermotoga sp. RQ2 differs from T. maritima in its genes involved in myo-inositol metabolism. Its genome also encodes an apparent fructose phosphotransferase system (PTS) sugar transporter. This operon is also found in Thermotoga naphthophila strain RKU-10 but no other Thermotogales. These are the first reported PTS transporters in the Thermotogales.     

Administration of a gonadotropin-releasing hormone antagonist to mares at different times during the luteal phase of the estrous cycle

The GnRH antagonist cetrorelix was given during the early (Days 1-5), mid (Days 6-10 or 5-12) or for the entire (Days 1-16) luteal phase of mares to inhibit the secretion of FSH and LH (Day 0=ovulation). Frequent blood sampling from Day 6 to Day 14 was used to determine the precise time-course of the suppression (cetrorelix given Days 6-10). Cetrorelix treatment caused a decrease in FSH and LH concentrations by 8 and 16 h, respectively, and an obliteration of the response to exogenous GnRH given 24h after treatment onset. Treatment never suppressed gonadotropin concentrations to undetectable levels; e.g. frequent sampling showed that the nadirs reached in FSH and LH were 46.2±6% and 33.1±11%, respectively, of pre-treatment concentrations. Daily FSH concentrations were decreased in all treatment groups but daily LH concentrations were lower only when treatment commenced at the beginning of the luteal phase; progesterone concentrations depended on the time of cetrorelix administration, but the changes suggested a role for LH in corpus luteum function. The inter-ovulatory interval was longer than controls when cetrorelix was given in the mid- or for the entire luteal phase, but was unaffected by treatment in the early phase. Nevertheless, in all groups, FSH concentrations were higher (P<0.05 when compared to Day 0, subsequent ovulation) approximately 6-10 days before this next ovulation. This consistent relationship suggests a stringent requirement for a GnRH-induced elevation of FSH above a threshold at, but only at, this time; i.e. approximately 6-10 days before ovulation.     

Influence of drought on plant performance through changes in belowground tritrophic interactions

Climate change is predicted to increase the risk of drought in many temperate agroecosystems. While the impact of drought on aboveground plant‐herbivore‐natural enemy interactions has been studied, little is known about its effects on belowground tritrophic interactions and root defense chemistry. We investigated the effects of low soil moisture on the interaction between maize, the western corn rootworm (WCR, Diabrotica virgifera), and soil‐borne natural enemies of WCR. In a manipulative field experiment, reduced soil moisture and WCR attack reduced plant performance and increased benzoxazinoid levels. The negative effects of WCR on cob dry weight and silk emergence were strongest at low moisture levels. Inoculation with entomopathogenic nematodes (EPNs, Heterorhabditis bacteriophora) was ineffective in controlling WCR, and the EPNs died rapidly in the warm and dry soil. However, ants of the species Solenopsis molesta invaded the experiment, were more abundant in WCR‐infested pots and predated WCR independently of soil moisture. Ant presence increased root and shoot biomass and was associated with attenuated moisture‐dependent effects of WCR on maize cob weight. Our study suggests that apart from directly reducing plant performance, drought can also increase the negative effects of root herbivores such as WCR. It furthermore identifies S. molesta as a natural enemy of WCR that can protect maize plants from the negative impact of herbivory under drought stress. Robust herbivore natural enemies may play an important role in buffering the impact of climate change on plant‐herbivore interactions.     

Synthesis of gibberellin GA6 and its role in flowering of Lolium temulentum

The induction of flowering by one long day (LD) in the grass Lolium temulentum is most closely mimicked by application of the gibberellins (GAs) GA(5) or GA(6), both of which occur naturally. These gibberellins promote floral development but have little effect on stem elongation. Endogenous GA(5) and GA(6) contents in the shoot apex double on the day after the LD and, for GA(5) (and we presume for GA(6) as well) reach a concentration known to be inductive for the excised shoot apex in vitro. They are, therefore, strong candidates as LD floral stimuli in this grass. The synthesis of GA(6) and an examination of its florigenic properties in L. temulentum are described.     

The Gla domain of factor IXa binds to factor VIIIa in the tenase complex

During blood coagulation factor IXa binds to factor VIIIa on phospholipid membranes to form an enzymatic complex, the tenase complex. To test whether there is a protein-protein contact site between the gamma-carboxyglutamic acid (Gla) domain of factor IXa and factor VIIIa, we demonstrated that an antibody to the Gla domain of factor IXa inhibited factor VIIIa-dependent factor IXa activity, suggesting an interaction of the factor IXa Gla domain with factor VIIIa. To study this interaction, we synthesized three analogs of the factor IXa Gla domain (FIX1-47) with Phe-9, Phe-25, or Val-46 replaced, respectively, with benzoylphenylalanine (BPA), a photoactivatable cross-linking reagent. These factor IX Gla domain analogs maintain native tertiary structure, as demonstrated by calcium-induced fluorescence quenching and phospholipid binding studies. In the absence of phospholipid membranes, FIX1-47 was able to inhibit factor IXa activity. This inhibition is dependent on the presence of factor VIIIa, suggesting a contact site between the factor IXa Gla domain and factor VIIIa. To demonstrate a direct interaction we did cross-linking experiments with FIX1-479BPA, FIX1-4725BPA, and FIX1-4746BPA. Covalent cross-linking to factor VIIIa was observed primarily with FIX1-4725BPA and to a much lesser degree with FIX1-4746BPA. Immunoprecipitation experiments with an antibody to the C2 domain of factor VIIIa indicate that the factor IX Gla domain cross-links to the A3-C1-C2 domain of factor VIIIa. These results suggest that the factor IXa Gla domain contacts factor VIIIa in the tenase complex through a contact site that includes phenylalanine 25 and perhaps valine 46.     

Evolutionary Relationships between Rhynchosporium lolii sp. nov. and Other Rhynchosporium Species on Grasses

The fungal genus Rhynchosporium (causative agent of leaf blotch) contains several host-specialised species, including R. commune (colonising barley and brome-grass), R. agropyri (couch-grass), R. secalis (rye and triticale) and the more distantly related R. orthosporum (cocksfoot). This study used molecular fingerprinting, multilocus DNA sequence data, conidial morphology, host range tests and scanning electron microscopy to investigate the relationship between Rhynchosporium species on ryegrasses, both economically important forage grasses and common wild grasses in many cereal growing areas, and other plant species. Two different types of Rhynchosporium were found on ryegrasses in the UK. Firstly, there were isolates of R. commune that were pathogenic to both barley and Italian ryegrass. Secondly, there were isolates of a new species, here named R. lolii, that were pathogenic only to ryegrass species. R. lolii was most closely related to R. orthosporum, but exhibited clear molecular, morphological and host range differences. The species was estimated to have diverged from R. orthosporum ca. 5735 years before the present. The colonisation strategy of all of the different Rhynchosporium species involved extensive hyphal growth in the sub-cuticular regions of the leaves. Finally, new species-specific PCR diagnostic tests were developed that could distinguish between these five closely related Rhynchosporium species.     

2-carboxy-d-hexitol 1,6-bisphosphate: An inhibitor of d-ribulose 1,5-bisphosphate carboxylase/oxygenase

2-Carboxy-d-hexitol 1,6-bisphosphate (CHBP) has been prepared from d-fructose 1,6-bisphosphate and cyanide. DEAE-Sephadex chromatography separated the reaction products into two fractions which were identified as CHBP and CHBP-lactone. CHBP is presumably a mixture of two diastereomers, 2-carboxy-d-glucitol 1,6-bisphosphate and 2-carboxy-d-mannitol 1,6-bisphosphate, but an attempt to separate these compounds was not successful. The material in the CHBP-lactone peak had no effect on d-ribulose 1,5-bisphosphate (RuBP) carboxylase. However, CHBP was a potent reversible inhibitor of RuBP carboxylases. This compound displayed an inhibition constant (K_i at pH 8.0 and 30 °C) of 1–2 μm with the enzymes from spinach and barley, while the K_i was 60–70 μm with bacterial RuBP carboxylases from Pseudomonas oxalaticus and Rhodospirillum rubrum. The mode of inhibition was competitive with respect to RuBP for all the carboxylases, and noncompetitive with respect to CO₂ for the enzymes from spinach, P. oxalaticus and R. rubrum. The results indicate that, in the binding of certain organic phosphates by RuBP carboxylases, there may be a fundamental difference between the enzymes isolated from microbial and from higher plant sources. RuBP oxygenase activities from spinach and P. oxalaticus were also inhibited by CHBP, with K_i values which were similar to those obtained with the carboxylase activity of the same enzymes. The mode of inhibition of the oxygenase activities was also competitive with respect to RuBP. Thus, it seems that the binding of CHBP is similar for the carboxylase and oxygenase reactions of the same enzyme.     

Thermal biology of the common garter snake Thamnophis sirtalis (L.)

Summary The thermoregulatory significance of a striped-melanic colour polymorphism in the common garter snake, Thamnophis sirtalis, was assessed through a combination of labortory experimentation and field study. In experiments with living snakes the melanic morph maintained a higher body temperature than the striped morph, when exposed to natural insolation. Experiments with excised skin showed that this thermal advantage is attributable to some integumental difference between the two morphs. Body temperatures of snakes in the field revealed that, during the colder part of the active season, melanics were able to stay warmer than striped snakes by an amount (1.24 C°) approximating the difference observed in the laboratory. Some evidence and argument is presented to suggest that melanism also may confer protection against overheating in warm periods.