PIWI silencing mechanism involving the retrotransposon nimbus orchestrates resistance to infection with Schistosoma mansoni in the snail vector, Biomphalaria glabrata.

BACKGROUND: Schistosomiasis remains widespread in many regions despite efforts at its elimination. By examining changes in the transcriptome at the host-pathogen interface in the snail Biomphalaria glabrata and the blood fluke Schistosoma mansoni, we previously demonstrated that an early stress response in juvenile snails, manifested by induction of heat shock protein 70 (Hsp 70) and Hsp 90 and of the reverse transcriptase (RT) domain of the B. glabrata non-LTR- retrotransposon, nimbus, were critical for B. glabrata susceptibility to S. mansoni. Subsequently, juvenile B. glabrata BS-90 snails, resistant to S. mansoni at 25°C become susceptible by the F2 generation when maintained at 32°C, indicating an epigenetic response. METHODOLOGY/PRINCIPAL FINDINGS: To better understand this plasticity in susceptibility of the BS-90 snail, mRNA sequences were examined from S. mansoni exposed juvenile BS-90 snails cultured either at 25°C (non-permissive temperature) or 32°C (permissive). Comparative analysis of transcriptomes from snails cultured at the non-permissive and permissive temperatures revealed that whereas stress related transcripts dominated the transcriptome of susceptible BS-90 juvenile snails at 32°C, transcripts encoding proteins with a role in epigenetics, such as PIWI (BgPiwi), chromobox protein homolog 1 (BgCBx1), histone acetyltransferase (BgHAT), histone deacetylase (BgHDAC) and metallotransferase (BgMT) were highly expressed in those cultured at 25°C. To identify robust candidate transcripts that will underscore the anti-schistosome phenotype in B. glabrata, further validation of the differential expression of the above transcripts was performed by using the resistant BS-90 (25°C) and the BBO2 susceptible snail stock whose genome has now been sequenced and represents an invaluable resource for molecular studies in B. glabrata. A role for BgPiwi in B. glabrata susceptibility to S. mansoni, was further examined by using siRNA corresponding to the BgPiwi encoding transcript to suppress expression of BgPiwi, rendering the resistant BS-90 juvenile snail susceptible to infection at 25°C. Given transposon silencing activity of PIWI as a facet of its role as guardian of the integrity of the genome, we examined the expression of the nimbus RT encoding transcript at 120 min after infection of resistant BS90 piwi-siRNA treated snails. We observed that nimbus RT was upregulated, indicating that modulation of the transcription of the nimbus RT was associated with susceptibility to S. mansoni in BgPiwi-siRNA treated BS-90 snails. Furthermore, treatment of susceptible BBO2 snails with the RT inhibitor lamivudine, before exposure to S. mansoni, blocked S. mansoni infection concurrent with downregulation of the nimbus RT transcript and upregulation of the BgPiwi encoding transcript in the lamivudine-treated, schistosome-exposed susceptible snails. CONCLUSIONS AND SIGNIFICANCE: These findings support a role for the interplay of BgPiwi and nimbus in the epigenetic modulation of plasticity of resistance/susceptibility in the snail-schistosome relationship.

Knowledge and practice of colorectal screening in a suburban group of Iraqi American women.

Colorectal cancer (CRC) was the second most common cancer among women in 2008, accounting for 571,000 cases, and 9.4% of all cancer cases afflicting women worldwide. According to the World Health Organization (WHO) and the Iraqi National Cancer Registry (INCR), Iraq has seen a steady rise in CRC rates among its general population over the past several decades. Despite Iraq's increasing national incidence of CRC and the growth of the US' Iraqi immigrant population over the last 10 years, little remains known about the prevalence of CRC among the latter population, their knowledge of CRC and associated risk factors, or their behavioral intent and practices regarding CRC screening. The aims of this study were to (1) examine the knowledge of and adherence to National Cancer Institute screening recommendations for CRC among a population of Iraqi women living in the Washington D.C. Metropolitan Area and (2) test the efficacy of a one-time educational intervention conducted using linguistically and culturally appropriate materials to raise awareness of, and promote future adherence to, CRC screening methods. This descriptive study used a pre/post design with a 12-month follow-up. Following extensive dissemination of information regarding the study in the Iraqi American community in the study location, 50 women were initially recruited, of whom 32 participated in the study. The study's findings revealed that the participants generally had low baseline levels of CRC screening adherence and preventive knowledge that significantly improved after the intervention as demonstrated by pre- and post-assessments of knowledge and behavior. These findings could be used to raise awareness (1) among clinicians regarding the need for early detection and screening of and referral for CRC treatment among Iraqi American women and (2) among Iraqi American women about risk factors for this disease and the importance of early detection and screening. The study also highlights the need for a larger study of knowledge, attitudes, and perceptions among both this population and the clinicians who serve them.

The inception and evolution of a unique masters program in cancer biology, prevention and control.

The University of the District of Columbia (UDC) and the Lombardi Comprehensive Cancer Center (LCCC), Georgetown University Medical Center established a Masters Degree Program in Cancer Biology, Prevention and Control at UDC that is jointly administered and taught by UDC and LCCC faculty. The goal of the Masters Degree Program is to educate students as master-level cancer professionals capable of conducting research and service in cancer biology, prevention, and control or to further advance the education of students to pursue doctoral studies. The Program's unique nature is reflected in its philosophy "the best cancer prevention and control researchers are those with a sound understanding of cancer biology". This program is a full-time, 2-year, 36-credit degree in which students take half of their coursework at UDC and half of their coursework at LCCC. During the second year, students are required to conduct research either at LCCC or UDC. Unlike most cancer biology programs, this unique Program emphasizes both cancer biology and cancer outreach training.

Biomphalaria glabrata peroxiredoxin: effect of schistosoma mansoni infection on differential gene regulation.

To identify gene(s) that may be associated with resistance/susceptibility in the intermediate snail host Biomphalaria glabrata to Schistosoma mansoni infection, a snail albumen gland cDNA library was differentially screened and a partial cDNA encoding an antioxidant enzyme thioredoxin peroxidase (Tpx), or peroxiredoxin (Prx), was identified. The 753bp full-length, single-copy, constitutively expressed gene now referred to as BgPrx4 was later isolated. BgPrx4 is a 2-Cys peroxiredoxin containing the conserved peroxidatic cysteine (C(P)) in the N-terminus and the resolving cysteine (C(R)) in the C-terminus. Sequence analysis of BgPrx4 from both resistant and susceptible snails revealed the presence of several (at least 7) single nucleotide polymorphisms (SNPs). Phylogenetic analysis indicated BgPrx4 to resemble a homolog of human peroxiredoxin, PRDX4. Northern analysis of hepatopancreas RNA from both resistant and susceptible snails showed that upon parasite exposure there were qualitative changes in gene expression. Quantitative real-time RT-PCR analysis showed differences in the levels of BgPrx4 transcript induction following infection, with the transcript up-regulated in resistant snails during the early phase (5h) of infection compared to susceptible snails in which it was down-regulated within the early time period. While there was an increase in transcription in susceptible snails later (48h) post-infection, this never reached the levels detected in resistant snails. A similar trend - higher, earlier up-regulation in the resistant snails but lower, slower protein expression in susceptible snails - was observed by Western blot analysis. Enzymatic analysis of the purified, recombinant BgPrx4 revealed the snail sequence to function as Prx but with an unusual ability to use both thioredoxin and glutathione as substrates.

Influence of biosolids compost on the bradyrhizobial genotypes recovered from cowpea and soybean nodules.

The interaction of biosolids compost application to soil and bradyrhizobial genotypes recovered from nodules was examined. Among 170 isolates, seven genotypes were recovered from soils receiving either no biosolids application or rates of 73 or 146 Mg/ha for three successive years. With the exception of one genotype, the distribution of the bacterial genotypes recovered from nodules was interrelated with the level of biosolids. Two of the genotypes nodulated both soybean and cowpea. Because soybean-nodulating bradyrhizobia were not recovered from control plots, it is possible that they had been introduced together with the biosolids compost application.

Ultrastructure of the Schistosoma mansoni cercaria.

The cercaria of the schistosome parasite is a short-lived, free-swimming larval stage that is infective for the mammalian, definitive host. This atlas describes the ultrastructure of the cells that comprise the cercaria of Schistosoma mansoni, a leading causative agent of human schistosomiasis. In addition to the cells which make up the various organ systems, such as the nervous, tegumental, osmoregulatory, muscular and primordial digestive systems, also we show the ultrastructure of those cells whose organization or location are not as well defined structurally but are essential nevertheless for the success of the parasite. These latter include the various support cells, and those cells that, upon differentiation into the adult worm, serve reproductive functions. A description is also given of the cells whose sole functions are realized only at the cercarial stage, chiefly involved in the vigorous act of skin penetration. Although we include a detailed review of the ultrastructure of S. mansoni cercariae, much of the information reported has not been previously published. In summary, this paper brings together an ultrastructural description of all the cell types presently known that make up the much studied larval stage of this medically important trematode.