Characterization of B-cell Responses to Zika Virus (ZIKV)

Objective: Most ZIKV infections occur in regions endemic for the related dengue virus (DENV). Anti-DENV antibodies have been demonstrated to cross-react with ZIKV. Some neutralize ZIKV infection while others mediate antibody-dependent enhancement (ADE), exacerbating ZIKV infection and complicating diagnosis of the etiologic agent. We aimed to characterize the humoral immune response in a ZIKV+, DENV- experienced individual in order to explore this anamnestic response and identify antibodies that may be useful in the development of therapeutic agents. Design and Methodology: Peripheral blood mononuclear cells (PBMCs) were collected from an individual (TT66) who was newly infected with ZIKV but had two previous DENV infections. Plasmablasts were isolated and analyses conducted using Atreca's Immune Repertoire CaptureTM technology. Monoclonal antibodies (mAbs) derived from TT66 during their acute and convalescent phase of ZIKV infection were screened in vitro for ZIKV and DENV binding and neutralization activity. Epitopes were then mapped using a shotgun mutagenesis approach. Results: We observed clonal expansion of two distinct antibody lineages representing 70% of total immunoglobulin sequences from TT66. We screened 18 mAbs representing two major lineages and five smaller families for neutralization and ADE between DENV and ZIKV. No highly typespecific mAbs were observed but rather a diverse pattern of neutralization, even within an individual lineage. Shotgun mutagenesis epitope mapping demonstrated epitopes for two of these broadly neutralizing mAb lineages lay within domain II ofE, close to the fusion loop. Conclusions: Results suggest that neutralizing antibody responses to ZIKV are extensively shaped by previous DENV exposure.

Control of cation concentrations in stream waters by surface soil processes in an Amazonian watershed.

The chemical composition of ground waters and stream waters is thought to be determined primarily by weathering of parent rock. In relatively young soils such as those occurring in most temperate ecosystems, dissolution of primary minerals by carbonic acid is the predominant weathering pathway that liberates Ca2+, Mg2+ and K+ and generates alkalinity in the hydrosphere. But control of water chemistry in old and highly weathered soils that have lost reservoirs of primary minerals (a common feature of many tropical soils) is less well understood. Here we present soil and water chemistry data from a 10,000-hectare watershed on highly weathered soil in the Brazilian Amazon. Streamwater cation concentrations and alkalinity are positively correlated to each other and to streamwater discharge, suggesting that cations and bicarbonate are mainly flushed from surface soil layers by rainfall rather than being the products of deep soil weathering carried by groundwater flow. These patterns contrast with the seasonal patterns widely recognized in temperate ecosystems with less strongly weathered soils. In this particular watershed, partial forest clearing and burning 30 years previously enriched the soils in cations and so may have increased the observed wet season leaching of cations. Nevertheless, annual inputs and outputs of cations from the watershed are low and nearly balanced, and thus soil cations from forest burning will remain available for forest regrowth over the next few decades. Our observations suggest that increased root and microbial respiration during the wet season generates CO2 that drives cation-bicarbonate leaching, resulting in a biologically mediated process of surface soil exchange controlling the streamwater inputs of cations and alkalinity from these highly weathered soils.

Emissions of nitrous oxide and nitric oxide from soils of native and exotic ecosystems of the Amazon and Cerrado regions of Brazil.

This paper reviews reports of nitrous oxide (N2O) and nitric oxide (NO) emissions from soils of the Amazon and Cerrado regions of Brazil. N2O is a stable greenhouse gas in the troposphere and participates in ozone-destroying reactions in the stratosphere, whereas NO participates in tropospheric photochemical reactions that produce ozone. Tropical forests and savannas are important sources of atmospheric N2O and NO, but rapid land use change could be affecting these soil emissions of N oxide gases. The five published estimates for annual emissions of N2O from soils of mature Amazonian forests are remarkably consistent, ranging from 1.4 to 2.4 kg N ha(-1) year(-1), with a mean of 2.0 kg N ha(-1) year(-1). Estimates of annual emissions of NO from Amazonian forests are also remarkably similar, ranging from 1.4 to 1.7 kg N ha(-1) year(-1), with a mean of 1.5 kg N ha(-1) year(-1). Although a doubling or tripling of N2O has been observed in some young (< or = 2 years) cattle pastures relative to mature forests, most Amazonian pastures have lower emissions than the forests that they replace, indicating that forest-to-pasture conversion has, on balance, probably reduced regional emissions slightly (<10%). Secondary forests also have lower soil emissions than mature forests. The same patterns apply for NO emissions in Amazonia. At the only site in Cerrado where vegetation measurements have been made N2O emissions were below detection limits and NO emissions were modest (approximately 0.4 kg N ha(-1) year(-1)). Emissions of NO doubled after fire and increased by a factor of ten after wetting dry soil, but these pulses lasted only a few hours to days. As in Amazonian pastures, NO emissions appear to decline with pasture age. Detectable emissions of N2O have been measured in soybean and corn fields in the Cerrado region, but they are modest relative to fluxes measured in more humid tropical agricultural regions. No measurements of NO from agricultural soils in the Cerrado region have been made, but we speculate that they could be more important than N2O emissions in this relatively dry climate. While a consistent pattern is emerging from these studies in the Amazon region, far too few data exist for the Cerrado region to assess the impact of land use changes on N oxide emissions.

Biochemistry and mode of action of the Bacillus sphaericus toxins.

Bacillus sphaericus produces at least two toxins which are highly toxic to mosquito larvae. The binary toxin, which is comprised of proteins of 51.4 and 41.9 kDa, is present in all highly insecticidal strains. The 100 kDa SSII-1 toxin is present in most highly insecticidal as well as the weakly insecticidal strains. The current status of studies on biochemistry and mode of action of these toxins is reviewed.