Pretransplantation Donor-Recipient Pair Seroreactivity Against BK Polyomavirus Predicts Viremia and Nephropathy After Kidney Transplantation.

Kidney transplant donors are not currently implicated in predicting BK polyomavirus (BKPyV) infection in kidney transplant recipients. It has been postulated, however, that BKPyV infection originates from the kidney allograft. Because BKPyV seroreactivity correlates with BKPyV replication and thus might mirror the infectious load, we investigated whether BKPyV seroreactivity of the donor predicts viremia and BKPyV-associated nephropathy (BKPyVAN) in the recipient. In a retrospective cohort of 407 living kidney donor-recipient pairs, pretransplantation donor and recipient sera were tested for BKPyV IgG levels and correlated with the occurrence of recipient BKPyV viremia and BKPyVAN within 1 year after transplantation. Donor BKPyV IgG level was strongly associated with BKPyV viremia and BKPyVAN (p < 0.001), whereas recipient BKPyV seroreactivity showed a nonsignificant inverse trend. Pairing of high-BKPyV-seroreactive donors with low-seroreactive recipients resulted in a 10-fold increased risk of BKPyV viremia (hazard ratio 10.1, 95% CI 3.5-29.0, p < 0.001). In multivariate analysis, donor BKPyV seroreactivity was the strongest pretransplantation factor associated with viremia (p < 0.001) and BKPyVAN (p = 0.007). The proportional relationship between donor BKPyV seroreactivity and recipient infection suggests that donor BKPyV seroreactivity reflects the infectious load of the kidney allograft and calls for the use of pretransplantation BKPyV serological testing of (potential) donors and recipients.

Herbivory and abiotic factors affect population dynamics of Arabidopsis thaliana in a sand dune area.

Population dynamics of the annual plant Arabidopsis thaliana (L.) Heynh. were studied in a natural habitat of this species on the coastal dunes of the Netherlands. The main objective was to elucidate factors controlling population dynamics and the relative importance of factors affecting final population density. Permanent plots were established and plants were mapped to obtain data on survival and reproductive performance of each individual, with special attention to herbivore damage. In experimental plots we studied how watering, addition of nutrients, artificial disturbance, and natural herbivores affected survival and growth. Mortality was low during autumn and early winter and high at the time of stem elongation, between February and April. A key factor analysis showed a high correlation between mortality from February to April and total mortality. The specialist weevils Ceutorhyncus atomus and C. contractus (Curculionidae) were identified as the major insect herbivores on A. thaliana, reducing seed production by more than 40 %. These herbivores acted in a plant size-dependent manner, attacking a greater fraction of the fruits on large plants. While mortality rates were not affected by density, fecundity decreased with density, although the effect was small. Adding water reduced mortality in rosette and flowering plant stages. Soil disturbance did not increase seed germination, but did have a significant positive effect on survival of rosette and flowering plants. Seed production of A. thaliana populations varied greatly between years, leading to population fluctuations, with a small role for density-dependent fecundity and plant size-dependent herbivory.

A novel approach to identify antigens recognized by CD4 T cells using complement-opsonized bacteria expressing a cDNA library.

In patients with hematological malignancies receiving HLA-matched stem cell transplantation, T cells specific for minor histocompatibility antigens play a major role in graft rejection, induction of graft-versus-host disease and beneficial graft-versus-leukemia reactivity. Several human minor histocompatibility antigens recognized by T cells have been identified, but only two are presented by HLA class II molecules. In search of an efficient approach to identify antigenic peptides processed through the HLA class II pathway, we constructed a cDNA library in bacteria that were induced to express proteins. Bacteria were opsonized with complement to enforce receptor-mediated uptake by Epstein-Barr virus immortalized B cells that were subsequently used as antigen-presenting cells. This approach was validated with an HLA class II-restricted antigen encoded by gene DBY. We were able to identify bacteria expressing DBY diluted into a 300-fold excess of bacteria expressing a nonrelevant gene. Screening of a bacterial library using a DBY-specific CD4 T cell clone resulted in the isolation of several DBY cDNAs. We propose this strategy for a rapid identification of HLA class II-restricted antigenic peptides recognized by CD4 T cells.

Sex ratio of some long-lived dioecious plants in a sand dune area.

In dioecious plants the fraction of males among flowering plants in the field (the secondary sex ratio) is the result of the fraction of males in the seeds (the primary sex ratio) and the subsequent survival and age at first reproduction of the two genders. It has been assumed that survival and age at first reproduction are the main determinants of biased secondary sex ratio but, especially for long-lived perennials, few data are available. We address this issue for natural populations of four long-lived perennials in a dune area. In Asparagus officinale and Bryonia dioica, the secondary sex ratio was unbiased. In Salix repens the secondary sex ratio was female-biased (0.337). Hippophae rhamnoides populations were male-biased; the average sex ratio of flowering plants was 0.658, while the fraction of males varied between 0.39 near the sea to 0.84 at the inland side of the dunes. The primary sex ratio was estimated by germinating seeds and growing plants under favourable conditions with minimal mortality. In S. repens the primary sex ratio in seeds was variable among mother plants and was, on average, female-biased (0.289). This is close to the secondary sex ratio, suggesting that the female bias already originates in the seed stage. In Hippophae rhamnoides the primary sex ratio was slightly male-biased (0.564). We argue that in this species, apart from the primary sex ratio, higher mortality and a later age at first reproduction for females contribute to the strong male bias among flowering plants in the field.

Contrasting dynamics in the same plant-herbivore interaction.

Long-term studies of two-species interactions under field conditions are unusual; most long-term field studies are of single species dynamics (1-6). Concurrent long-term studies on the dynamics of the same two interacting species in different locations are very rare. This result has led to the tacit assumption that different cases of the same two-species interaction would involve essentially quantitative differences (e.g., context-specific differences in the numeric values of demographic parameters like fecundity or death rates). Here, we show that for one of the best-known two-species systems (ragwort and cinnabar moth), this finding does not hold. The interaction between the plant and its herbivore is fundamentally different in coastal dunes in The Netherlands and in grasslands in Southeast England. In the first case, the dynamics are cyclic and the interaction involves both direct and delayed density dependence; in the second case, the insect has little impact on plant dynamics and there are no time lags in density dependence. The difference is caused by differences in the importance of seed-limitation in plant recruitment in the two locations.

Synaptojanin 2 is recognized by HLA class II-restricted hairy cell leukemia-specific T cells.

Hairy cell leukemia (HCL) is a chronic mature B-cell leukemia characterized by malignant B cells that have typical hairy protrusions. To characterize possible HCL-associated tumor antigens, we generated an HCL-specific and HLA class II (DPw4)-restricted proliferative CD4+ T-cell clone. To identify the target antigen of these T cells, we constructed a synthetic peptide library dedicated to bind HLA DPw4, and identified a mimicry epitope recognized by the T-cell clone. With this epitope, the recognition motif of the T-cell clone was deduced and a peptide of human synaptojanin 2 (Syn 2) was identified that stimulated the HCL-reactive T-cell clone. Both Northern and Western blot analyses showed that Syn 2 expression was increased in HCL samples compared to other B cells. Besides, the Syn 2-expressing cell line AML193, with the introduced restrictive HLA-DPw4 molecules, was recognized by the HCL-specific T-cell clone. These results indicate that Syn 2 is a target of autoreactive HCL-specific T cells. Since Syn 2 is a phosphatidylinositol 4,5-biphosphatase involved in cell growth and rearrangement of actin filaments, the increased Syn 2 expression may correlate with the disease etiology or the characteristic morphologic alterations caused by the disease.

Inhibition of human papillomavirus-16 long control region activity by interferon-gamma overcome by p300 overexpression.

Although interferons (IFNs) are currently used in the treatment of various human papillomavirus (HPV)-associated lesions, their mechanisms of action are still unclear. In this study, we clearly demonstrated that IFN-gamma was a strong inhibitor of HPV-16 long control region (LCR) activity in two human cervical carcinoma cell lines. The effect of IFN-gamma was dose dependent. We investigated whether the effect of IFN-gamma on HPV-16 LCR could involve the inhibition of the CREB-binding protein (CBP)/p300 family of transcriptional coactivators. In support of this model, we demonstrated by transfection experiments that a 12S E1A mutant (RG2), which interacts poorly with p300 and CBP in comparison to wild-type E1A, was less able to repress human papillomavirus (HPV) 16 long control region (LCR) than wild-type E1A. More important, overexpression of p300 was able to increase the HPV-16 LCR activity and to overcome inhibition by IFN-gamma. Finally, we demonstrated that p300 could cooperate with c-jun to activate HPV-16 LCR. According to our results, IFN-gamma might inhibit HPV-16 LCR transcription by activating the signal transducer and activator of transcription 1alpha, which in turn might compete for p300/CBP binding with specific transcription factors involved in LCR activation.

A functional NF-kappaB binding site in the human papillomavirus type 16 long control region.

By computer search, we identified one potential NF-kappaB binding site in the HPV16 long control region (LCR) at position 7554-7563 having two mismatches in comparison to the consensus NF-kappaB binding site of the Igkappa L promoter. Bandshift experiments with nuclear extracts from HeLa cells or purified glutathione S-transferase-p65 fusion protein clearly demonstrated that NF-kappaB is able to bind to this region of the LCR. However, in comparison to NF-kappaB binding on a consensus probe, the affinity of NF-kappaB for this site is about 250-fold reduced. When mutations were introduced into this NF-kappaB binding site, the activity of the LCR was increased, strongly suggesting that NF-kappaB was acting as a transcriptional repressor in the context of the HPV16 LCR. In addition, overexpression of NF-kappaB p65 repressed the activity of the HPV16 LCR, strengthening this conclusion.

Transcriptional regulation of human papillomavirus type 16 LCR by different C/EBPbeta isoforms.

During genital human papillomavirus (HPV) infection several cytokines are released, such as interleukin-1 (IL-1), tumor necrosis factoralpha (TNFalpha), IL-6, and IL-8. These cytokines may play a role in the immune surveillance against viral infection. Two of these cytokines, IL-1 and TNFalpha, suppress the transcription of the HPV16 early genes. CAATT/ enhancer binding protein, (C/EBPbeta), which is activated by IL-1 and TNFalpha, has been suggested to act as a mediator of this transcriptional downregulation. C/EBPbeta contains three different translation initiation sites that can lead probably by leaky ribosome scanning to the generation of three isoforms of C/EBPbeta, namely full-length C/EBPbeta, liver enriched transcriptional activator protein (LAP), and liver enriched inhibitory protein (LIP). When transiently expressed in C33A and HeLa cells, the first two C/EBPbeta isoforms activate the HPV16 long control region (LCR). LIP, which acts as an antagonist of C/EBPbeta, represses the HPV16 LCR activity. Our observation that treatment of HeLa cells with IL-1 leads to induction of LIP supports the hypothesis that the LCR downregulation by IL-1 is mediated by LIP.

Evolutionary dynamics of seed size and seedling competitive ability.

We present a model for the evolutionary dynamics of seed size when there is a trade-off between seed size and seed number, and seedlings from large seeds are better competitors and have a higher precompetitive survival than seedlings from small seeds. We find that strong competitive asymmetry, high resource levels, and intermediate harshness of the precompetitive environment favor coexistence of plants with different seed sizes. If the evolution of seed size is mutation-limited and single mutations have only a small phenotypic effect, then an initially monomorphic population reaches the final evolutionarily stable polymorphic state through one or more discrete evolutionary branching events. At each such branching event, a given lineage already present in the population divides into two phenotypically diverging daughter lines, each with its own seed size. If the precompetitive survival of seeds and seedlings is high for small and large seeds alike, however, evolutionary branching may be followed by the extinction of one or more lineages. Various results presented here are model-independent and point the way to a more general evolutionary bifurcation theory describing how the number and stability properties of evolutionary equilibria may change as a consequence of changes in model parameters.

Involvement of strictosidine as a defensive chemical inCatharanthus roseus.

The involvement of the glucoalkaloid strictosidine in antimicrobial and antifeedant activity inCatharanthus roseus leaves was investigated. Strictosidine and its deglucosylation product, specifically formed by the enzyme strictosidine glucosidase, were shown to be active against several microorganisms. In contrast, neither the intact glucoside, nor the aglycone product(s) was found to exhibit antifeedant activity againstSpodoptera exigua larvae, as was found for intactC. roseus leaves and leaf extracts. Besides alkaloids further downstream in the biosynthesis pathway, a more apolar, yet unidentified compound may be involved in this activity.

The role of primary and secondary metabolites in chrysanthemum resistance toFrankliniella occidentalis.

The presence of deleterious secondary metabolites to western flower thrips (WFT) (Frankliniella occidentalis Pergande) in several chrysanthemum (Dendranthema grandiflora Tzvelev) cultivars was tested. WFT performance on leaf sap mixed with artificial diet was compared to WFT performance on a control of artificial diet mixed with water. Leaf sap of six of 10 chrysanthemum cultivars tested had a significant negative effect on WFT performance and therefore contained deleterious secondary metabolites. Leaf sap of a resistant and a susceptible chrysanthemum cultivar were fractionated by gel to study the role of secondary metabolites in greater detail. None of the 20 individual fractions obtained had a negative effect on WFT performance, whereas after mixing of these fractions activity was found again. Moreover, WFT performance on the fraction mixture of the resistant cultivar was significantly lower than on the susceptible fraction mixture. The results suggest that WFT resistance in the cultivars studied was caused by several secondary metabolites that had an additional or synergistic negative effect on WFT performance. The role of a deficiency of primary metabolites in WFT resistance of chrysanthemum was also investigated. WFT performance on leaf sap with and without extra primary metabolites (artificial diet) was compared. The variance in WFT performance was significantly smaller when extra primary metabolites were added; WFT performance on leaf sap with and without extra primary metabolites was not correlated. The results suggest that resistance was partly caused by a deficiency of primary metabolites.

The "Raison D'être" of pyrrolizidine alkaloids inCynoglossum officinale: Deterrent effects against generalist herbivores.

In this study we tested whether pyrrolizidine alkaloids (PAs) ofCynoglossum officinale serve as antifeedants against herbivores. Total PA N-oxide extracts of the leaves significantly deterred feeding by generalist herbivores. Specialist herbivores did not discriminate between food with high and low PA levels. Three PAs fromC. officinale, heliosupine, echinatine, and 3'-acetylechinatine, equally deterred feeding by the polyphagous larvae ofSpodoptera exigua. Although the plants mainly contain PAs in their N-oxide form, reduced PAs deterred feeding byS. exigua more efficiently than PA N-oxides. On rosette plants, the monophagous weevilMogulones cruciger significantly consumed more of the youngest leaves, which had the highest PA level and the highest nitrogen percentage. Larvae ofEthmia bipunctella, which are oligophagous within the Boraginaceae, did not discriminate between leaves. All generalist herbivores tested significantly avoided the youngest leaves with the highest PA levels. In the field, the oldest leaves also were relatively more damaged by herbivores than the youngest leaves. It is hypothesized that the skewed distribution of PAs over the leaves of rosette plants reflects optimal defense distribution within the plant.

Detrimental effects ofCinchona leaf alkaloids on larvae of the polyphagous insectSpodoptera exigua.

YoungCinchona ledgeriana plants contain two types of alkaloid: indole alkaloids in the leaves and quinoline alkaloids in the root. FromCinchona leaves, a crude alkaloid extract was made, containing the cinchophylline type of indole alkaloids and a small amount of 5-methoxytryptamine. The leaf alkaloid extract exerted a strong detrimental effect on the growth of larvae of the polyphagous beet armyworm,Spodoptera exigua (Lepidoptera). Feeding of larvae on an artificial diet containing the leaf alkaloids at the same concentrations as those found in the plant resulted in significant growth reduction, retardation in development, and mortality of the larvae. Cinchophyllines are composed of 5-methoxytryptamine coupled to a corynantheal unit. When incorporated into the artificial diet, 5-methoxytryptamine alone had no effect on the 5.exigua larvae. Corynantheal, however, had a strong detrimental effect on growth of the larvae, its effect being comparable to that of the leaf alkaloid extract. In contrast to the indole-type leaf alkaloids, the quinolinetypeCinchona root alkaloids did not affect growth and development of the larvae. These results suggest that the indole-type alkaloids, which inCinchona plants are present at the highest concentrations in the young, vulnerable leaflets, are involved in the chemical defense of the plant against herbivorous insects.

Herbivore exploitation of a fugitive plant species: Local survival and extinction of the Cinnabar Moth and Ragwort in a heterogeneous environment.

1. In the dune system under observation, Ragwort is distributed in small local populations that have only a restricted lifetime; (temporary) extinction has been observed frequently. 2. Cinnabar Moth attack on these populations is of even shorter duration. Colonization and extinction of the Cinnabar Moth is related to the amount of food present. 3. The presence of the predator Formica polyctena negatively influences the probability of local oviposition. 4. There is a continual shift of the Cinnabar Moth over its food-plant populations. When populations in a favorable food situation in Formica-free habitats became scarce, there was a shift towards populations in Formica habitats. 5. Negative effects of attack on the food-plant populations could be demonstrated, but they were small compared to fluctuations in these populations caused by other factors. 6. After dispersal each year new plant populations providing a favorable food situation are colonized. The heterogeneity of the populations in time and space is the factor that ensures survival of the insect in the system of plant populations.