Synthesis and Evaluation of Acyclic Nucleotide Analogs

Abstract

Acyclic nucleotide analogs derived from antiviral 9-(2-phosphonylmethoxyethyl)adenine by modification at the side chain or by alternation of the heterocyclic base were synthesized and investigated for their antiviral activity.     

Improved Targeting of the Flanks of a DNA Stem Using α-Oligodeoxynucleotides.-The Enhanced Effect of an Intercalator

Abstract

2′-Deoxy-5′-0-(4,4′-dimethoxytrityl)-5-methyl-N ⁴-(1-pyrenylmethyl)-α-cytidine (5) was prepared by reaction of 1-pyrenylmethylamine with an appropriate protected 4-(l,2,4-triazolyl)-α-thymidine derivative 3 which was synthesized from 5-O-DMT protected α-thymidine 1. Aminolysis of 3 afforded 3′-O-acetyl-2′-deoxy-5′-O-(4,4′-dimethoxytrityl)-5-methyl-α-cytidine (8). Benzoylation of 8 and removal of acetyl afforded N ⁴-benzoyl-2-deoxy-5–0-(4,4′-dimethoxytrityl)-5-methyl-α-cytidine (10). The amidites of compounds 5and 10 were prepared and used in α-oligonucleotide synthesis. DNA three-way junction (TWJ) is stabilized when an α-ODN is used for targeting the dangling flanks of the stem in a DNA hairpin. Further stabilization of the TWJ is observed when 5 is inserted into the α-ODN at the junction region.

     

Ribosylation of Pyrimidine 2′-Deoxynucleosides

Abstract

The previously developed method for the preparation of 2′-O-D-ribofuranosyl-nucleosides is extended to ribosylation of 2′-deoxynucleosides. The scope and limitations of this reaction are discussed.     

Symbiotic specificity,association patterns,and function determine community responses to global changes: defining critical research areas for coral‐Symbiodinium symbioses

Climate change‐driven stressors threaten the persistence of coral reefs worldwide. Symbiotic relationships between scleractinian corals and photosynthetic endosymbionts (genus Symbiodinium) are the foundation of reef ecosystems, and these associations are differentially impacted by stress. Here, we couple empirical data from the coral reefs of Moorea, French Polynesia, and a network theoretic modeling approach to evaluate how patterns in coral‐Symbiodinium associations influence community stability under climate change. To introduce the effect of climate perturbations, we simulate local ‘extinctions’ that represent either the loss of coral species or the ability to engage in symbiotic interactions. Community stability is measured by determining the duration and number of species that persist through the simulated extinctions. Our results suggest that four factors greatly increase coral‐Symbiodinium community stability in response to global changes: (i) the survival of generalist hosts and symbionts maximizes potential symbiotic unions; (ii) elevated symbiont diversity provides redundant or complementary symbiotic functions; (iii) compatible symbiotic assemblages create the potential for local recolonization; and (iv) the persistence of certain traits associate with symbiotic diversity and redundancy. Symbiodinium may facilitate coral persistence through novel environmental regimes, but this capacity is mediated by symbiotic specificity, association patterns, and the functional performance of the symbionts. Our model‐based approach identifies general trends and testable hypotheses in coral‐Symbiodinium community responses. Future studies should consider similar methods when community size and/or environmental complexity preclude experimental approaches.     

Effect of Alpha Linolenic Acid Supplementation on Serum Prostate Specific Antigen (PSA): Results from the Alpha Omega Trial

Background

Alpha linolenic acid (ALA) is the major omega-3 fatty acid in the diet. Evidence on health effects of ALA is not conclusive, but some observational studies found an increased risk of prostate cancer with higher intake of ALA. We examined the effect of ALA supplementation on serum concentrations of prostate-specific antigen (PSA), a biomarker for prostate cancer.

Methods

The Alpha Omega Trial (ClinicalTrials.gov Identifier: {"type":"clinical-trial","attrs":{"text":"NCT00127452","term_id":"NCT00127452"}}NCT00127452) was a double-blind, placebo-controlled trial of ALA and the fish fatty acids eicosapentanoic acid (EPA) and docosahexanoic acid (DHA) on the recurrence of cardiovascular disease, using a 2×2 factorial design. Blood was collected at the start and the end of the intervention period. The present analysis included 1622 patients with a history of a myocardial infarction, aged 60–80 years with an initial PSA concentration <4 ng/mL. They received either 2 g per day of ALA or placebo in margarine spreads for 40 months. T-tests and logistic regression were used to assess the effects of ALA supplementation on changes in serum PSA (both continuously and as a dichotomous outcome, cut-off point: >4 ng/mL).

Findings

Mean serum PSA increased by 0.42 ng/mL on placebo (n = 815) and by 0.52 ng/mL on ALA (n = 807), a difference of 0.10 (95% confidence interval: −0.02 to 0.22) ng/mL (P = 0·12). The odds ratio for PSA rising above 4 ng/mL on ALA versus placebo was 1.15 (95% CI: 0.84–1.58).

Interpretation

An additional amount of 2 g of ALA per day increased PSA by 0.10 ng/mL, but the confidence interval ranged from −0.02 to 0.22 ng/mL and included no effect. Therefore, more studies are needed to establish whether or not ALA intake has a clinically significant effect on PSA or prostate cancer.

Trial registration information

ClinicalTrials.gov; Identifier: {"type":"clinical-trial","attrs":{"text":"NCT00127452","term_id":"NCT00127452"}}NCT00127452. URL: http://www.clinicaltrials.gov/ct2/show/{"type":"clinical-trial","attrs":{"text":"NCT00127452","term_id":"NCT00127452"}}NCT00127452.     

Microbiota Dynamics in Patients Treated with Fecal Microbiota Transplantation for Recurrent Clostridium difficile Infection

Clostridium difficile causes antibiotic-associated diarrhea and pseudomembraneous colitis and is responsible for a large and increasing fraction of hospital-acquired infections. Fecal microbiota transplantation (FMT) is an alternate treatment option for recurrent C. difficile infection (RCDI) refractory to antibiotic therapy. It has recently been discussed favorably in the clinical and scientific communities and is receiving increasing public attention. However, short- and long-term health consequences of FMT remain a concern, as the effects of the transplanted microbiota on the patient remain unknown. To shed light on microbial events associated with RCDI and treatment by FMT, we performed fecal microbiota analysis by 16S rRNA gene amplicon pyrosequencing of 14 pairs of healthy donors and RCDI patients treated successfully by FMT. Post-FMT patient and healthy donor samples collected up to one year after FMT were studied longitudinally, including one post-FMT patient with antibiotic-associated relapse three months after FMT. This analysis allowed us not only to confirm prior reports that RCDI is associated with reduced diversity and compositional changes in the fecal microbiota, but also to characterize previously undocumented post-FMT microbiota dynamics. Members of the Streptococcaceae, Enterococcaceae, or Enterobacteriaceae were significantly increased and putative butyrate producers, such as Lachnospiraceae and Ruminococcaceae were significantly reduced in samples from RCDI patients before FMT as compared to post-FMT patient and healthy donor samples. RCDI patient samples showed more case-specific variations than post-FMT patient and healthy donor samples. However, none of the bacterial groups were invariably associated with RCDI or successful treatment by FMT. Overall microbiota compositions in post-FMT patients, specifically abundances of the above-mentioned Firmicutes, continued to change for at least 16 weeks after FMT, suggesting that full microbiota recovery from RCDI may take much longer than expected based on the disappearance of diarrheal symptoms immediately after FMT.     

Indirect Immunofluorescence Assay for the Simultaneous Detection of Antibodies against Clinically Important Old and New World Hantaviruses

In order to detect serum antibodies against clinically important Old and New World hantaviruses simultaneously, multiparametric indirect immunofluorescence assays (IFAs) based on biochip mosaics were developed. Each of the mosaic substrates consisted of cells infected with one of the virus types Hantaan (HTNV), Puumala (PUUV), Seoul (SEOV), Saaremaa (SAAV), Dobrava (DOBV), Sin Nombre (SNV) or Andes (ANDV). For assay evaluation, serum IgG and IgM antibodies were analyzed using 184 laboratory-confirmed hantavirus-positive sera collected at six diagnostic centers from patients actively or previously infected with the following hantavirus serotypes: PUUV (Finland, n = 97); SEOV (China, n = 5); DOBV (Romania, n = 7); SNV (Canada, n = 23); ANDV (Argentina and Chile, n = 52). The control panel comprised 89 sera from healthy blood donors. According to the reference tests, all 184 patient samples were seropositive for hantavirus-specific IgG (n = 177; 96%) and/or IgM (n = 131; 72%), while all control samples were tested negative. In the multiparametric IFA applied in this study, 183 (99%) of the patient sera were IgG and 131 (71%) IgM positive (accordance with the reference tests: IgG, 96%; IgM, 93%). Overall IFA sensitivity for combined IgG and IgM analysis amounted to 100% for all serotypes, except for SNV (96%). Of the 89 control sera, 2 (2%) showed IgG reactivity against the HTNV substrate, but not against any other hantavirus. Due to the high cross-reactivity of hantaviral nucleocapsid proteins, endpoint titrations were conducted, allowing serotype determination in >90% of PUUV- and ANDV-infected patients. Thus, multiparametric IFA enables highly sensitive and specific serological diagnosis of hantavirus infections and can be used to differentiate PUUV and ANDV infection from infections with Murinae-borne hantaviruses (e.g. DOBV and SEOV).