Initial antibodies binding to HIV-1 gp41 in acutely infected subjects are polyreactive and highly mutated

Many HIV-1 envelope-reactive antibodies shortly after HIV-1 transmission may arise from crow-reactive memory B cells previously stimulated by non-HIV-1 host or microbial antigen

Cage Matching: Head to Head Competition Experiments of an Invasive Plant Species from Different Regions as a Means to Test for Differentiation

Many hypotheses are prevalent in the literature predicting why some plant species can become invasive. However, in some respects, we lack a standard approach to compare the breadth of various studies and differentiate between alternative explanations. Furthermore, most of these hypotheses rely on ‘changes in density’ of an introduced species to infer invasiveness. Here, we propose a simple method to screen invasive plant species for potential differences in density effects between novel regions. Studies of plant competition using density series are a fundamental tool applied to virtually every aspect of plant population ecology to better understand evolution. Hence, we use a simple density series with substitution contrasting the performance of Centaurea solstitialis in monoculture (from one region) to mixtures (seeds from two regions). All else being equal, if there is no difference between the introduced species in the two novel regions compared, Argentina and California, then there should be no competitive differences between intra and inter-regional competition series. Using a replicated regression design, seeds of each species were sown in the greenhouse at 5 densities in monoculture and mixed and grown till onset of flowering. Centaurea seeds from California had higher germination while seedlings had significantly greater survival than Argentina. There was no evidence for density dependence in any measure for the California region but negative density dependence was detected in the germination of seeds from Argentina. The relative differences in competition also differed between regions with no evidence of differential competitive effects of seeds from Argentina in mixture versus monoculture while seeds from California expressed a relative cost in germination and relative growth rate in mixtures with Argentina. In the former instance, lack of difference does not mean ‘no ecological differences’ but does suggest that local adaptation in competitive abilities has not occurred. Importantly, this method successfully detected differences in the response of an invasive species to changes in density between novel regions which suggests that it is a useful preliminary means to explore invasiveness

Antibody light-chain-restricted recognition of the site of immune pressure in the RV144 HIV-1 vaccine trial is phylogenetically conserved.

CAPRISA, 2014.Abstract available in pdf

The small-scale spatiotemporal pattern of the seedbank and vegetation of a highly invasive weed, Centaurea solstitialis: Strength in numbers

The dynamics of invasive plant populations are intriguing and informative of the importance of population and community-level processes. A dominant approach to understanding and describing invasion has been the development of unique hypotheses to explain invasion. However, here we directly explore the relevance of the small-scale, spatiotemporal pattern in seedbanks and plants of the highly invasive weed, Centaurea solstitialis, to determine whether pattern can be used to contrast predictions associated with the simple ecological hypotheses of seed versus microsite limitations. At three invaded grasslands in California, highly invaded (> 20 adult plants present), invaded (< 10 adults), and uninvaded (no C. solstitialis plants) sites were selected. The spatial pattern of the seedbank was assessed using fine-scale, 2 cm diameter contiguous cores and geostatistical statistics, and the number of C. solstitialis seeds in the seedbank was recorded in addition to the total community seedbank density. Three of the four critical predictions associated with the seed limitation hypothesis were clearly supported as an explanation for the patterns of C. solstitialis invasion observed in the field. The density of C. solstitialis seeds decreased from high to low extents of invasion, there was no relationship between the community seedbank and C. solstitialis seeds, and the distances between C. solstitialis plants was inversely related to the density of C. solstitialis seeds. However, both the persistent and transient seedbanks of C. solstitialis were spatially aggregated with autocorrelation up to 12 cm2 which suggests that aggregation is a consistent attribute of this species in the seedbank regardless of extent of invasion. This basic pattern-based approach clearly detected an ecological signal of invasive seedbank dynamics and is thus a useful tool for subsequent studies of invasions in grasslands.Fil: Lortie, Cristopher J.. York University; CanadáFil: Munshaw, Michael. York University; CanadáFil: DiTomaso, Joseph. University of California at Davis; Estados UnidosFil: Hierro, Jose Luis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. York University; Canad

The relative effect of growth in competition with <i>C. solstitialis</i> plants from another invaded region (California and Argentina) to performance in monocultures, i.e. seeds from the same region.

<p>The mean relative interaction indices are plotted (Rii)+/−1 s.e. and were calculated for each paired density (2, 10, & 20 seeds per pot).</p

Tests of the relative interaction index (Rii) contrasting performance in mixtures to that in monocultures.

<p>Mixtures refers to the performance of individuals of <i>C. solstitialis</i> in competition with seeds sown from two regions, Argentina (AR) and California (CA), at 2, 10, and 20 seeds per pot or in monocultures, i.e. seeds from only one invaded region. Two-tailed t-tests were used to determine whether the mean Rii values were significantly different from 0 (at p<0.01).</p

A summary of the generalised linear models used to test the importance of density, region, and density by region on the four responses measured in this greenhouse experiment of <i>C. solstitialis</i>.

<p>Seeds collected from two invaded regions were tested (California and Argentina), densities included 1, 2, 5, 10, and 20 seeds per pot, and details for the responses are reported in the text. Proportionate germination and survival were tested with logistic models and relative growth rates (rgr) with linear models. Bold denotes significant effects.</p

The importance of density on measures of the invasive weed <i>C. solstitialis</i>.

<p>See text for generalized linear model statistics. Data is summarized by plotting the mean response per seed densities tested (1, 2, 5, 10, & 20).</p