Vertical segregation and phylogenetic characterization of ammonia-oxidizing Archaea in a deep oligotrophic lake

12 páginas, 6 figuras, 1 tabla.Freshwater habitats have been identified as one of the largest reservoirs of archaeal genetic diversity, with specific lineages of ammonia-oxidizing archaea (AOA) populations different from soils and seas. The ecology and biology of lacustrine AOA is, however, poorly known. In the present study, vertical changes in archaeal abundance by CARD-FISH, quantitative PCR (qPCR) analyses and identity by clone libraries were correlated with environmental parameters in the deep glacial high-altitude Lake Redon. The lake is located in the central Spanish Pyrenees where atmospheric depositions are the main source of reactive nitrogen. Strong correlations were found between abundance of thaumarchaeotal 16S rRNA gene, archaeal amoA gene and nitrite concentrations, indicating an ammonium oxidation potential by these microorganisms. The bacterial amoA gene was not detected. Three depths with potential ammonia-oxidation activity were unveiled along the vertical gradient, (i) on the top of the lake in winter–spring (that is, the 0 oC slush layers above the ice-covered sheet), (ii) at the thermocline and (iii) the bottom waters in summer—autumn. Overall, up to 90% of the 16S rRNA gene sequences matched Thaumarchaeota, mostly from both the Marine Group (MG) 1.1a (Nitrosoarchaeum-like) and the sister clade SAGMGC−1 (Nitrosotalea-like). Clone-libraries analysis showed the two clades changed their relative abundances with water depth being higher in surface and lower in depth for SAGMGC−1 than for MG 1.1a, reflecting a vertical phylogenetic segregation. Overall, the relative abundance and recurrent appearance of SAGMGC−1 suggests a significant environmental role of this clade in alpine lakes. These results expand the set of ecological and thermal conditions where Thaumarchaeota are distributed, unveiling vertical positioning in the water column as a key factor to understand the ecology of different thaumarchaeotal clades in lacustrine environments.This research was supported by grants CRENYC CGL2006-12058 and PIRENA CGL2009-13318 to EOC, and CONSOLIDER grant GRACCIE CSD2007-00067 from the Spanish Office of Science and Innovation (MICINN). JCA benefits from a Juan de la Cierva postdoctoral fellow (MICINN).Peer reviewe

Anamnestic immune response and safety of an inactivated quadrivalent influenza vaccine in primed versus vaccine-naïve children

Background: It has not yet been demonstrated whether two doses of inactivated quadrivalent influenza vaccine (IIV4) prime a booster response in infants. We evaluated the anamnestic immune response to an IIV4 in children aged 17−48 months. Methods: Children were randomized to two doses of IIV4 or control in the primary phase III study (NCT01439360). One year later, in an open-label revaccination extension study (NCT01702454), a subset of children who received IIV4 in the primary study (primed group) received one IIV4 dose and children who received control in the primary study (unprimed) received two IIV4 doses 28 days apart. The primary objective was to evaluate hemagglutination inhibition (HI) antibody titers 7 days after first IIV4 vaccination in the per-protocol cohort (N=224 primed; N=209 unprimed). Neutralizing and anti-neuraminidase antibodies were also measured. Safety was analyzed in the total vaccinated cohort (N=241 primed; N=229 unprimed). Results: An anamnestic response was observed in primed children relative to unprimed controls, measured by age-adjusted geometric mean HI titer ratios against strains homologous (A/H1N1: 9.0; B/Victoria: 3.9) and heterologous (A/H3N2: 2.7; B/Yamagata: 6.7) to those in the primary vaccination series. The anamnestic response in primed children included increases in neutralizing antibodies (mean geometric increase: 5.0–10.6) and anti-neuraminidase antibodies (4.9–8.8). No serious adverse events related to vaccination were reported. Conclusion: In this study, 2-dose priming with IIV4 induced immune memory that was recalled with 1-dose IIV4 the following year to boost HI, anti-neuraminidase, and neutralizing antibodies, even though the IIV4 strain composition partially changed

Anamnestic immune response and safety of an inactivated quadrivalent influenza vaccine in primed versus vaccine-naïve children

Background: It has not yet been demonstrated whether two doses of inactivated quadrivalent influenza vaccine (IIV4) prime a booster response in infants. We evaluated the anamnestic immune response to an IIV4 in children aged 17−48 months. Methods: Children were randomized to two doses of IIV4 or control in the primary phase III study (NCT01439360). One year later, in an open-label revaccination extension study (NCT01702454), a subset of children who received IIV4 in the primary study (primed group) received one IIV4 dose and children who received control in the primary study (unprimed) received two IIV4 doses 28 days apart. The primary objective was to evaluate hemagglutination inhibition (HI) antibody titers 7 days after first IIV4 vaccination in the per-protocol cohort (N=224 primed; N=209 unprimed). Neutralizing and anti-neuraminidase antibodies were also measured. Safety was analyzed in the total vaccinated cohort (N=241 primed; N=229 unprimed). Results: An anamnestic response was observed in primed children relative to unprimed controls, measured by age-adjusted geometric mean HI titer ratios against strains homologous (A/H1N1: 9.0; B/Victoria: 3.9) and heterologous (A/H3N2: 2.7; B/Yamagata: 6.7) to those in the primary vaccination series. The anamnestic response in primed children included increases in neutralizing antibodies (mean geometric increase: 5.0–10.6) and anti-neuraminidase antibodies (4.9–8.8). No serious adverse events related to vaccination were reported. Conclusion: In this study, 2-dose priming with IIV4 induced immune memory that was recalled with 1-dose IIV4 the following year to boost HI, anti-neuraminidase, and neutralizing antibodies, even though the IIV4 strain composition partially changed