Effectiveness of Egg Yolk Antibody Against Shiga Toxin II Variant Toxicity In Vitro and In Vivo

We prepared anti-Shiga toxin II variant (Stx2e) and anti-Stx2e B antibodies in chicken egg yolk and investigated their effectiveness in vitro and in vivo. Both Egg yolk antibodies (IgY) reduced the cytotoxic effects of Stx2e to Vero cells. The protective efficacy of anti-Stx2e IgY and anti-Stx2e B IgY was investigated in clean Kunming mice, which were experimentally induced with Stx2e. Peritoneal injection of anti-Stx2e IgY and anti-Stx2e B IgY apparently reduced the lethal effect of Stx2e to mice. These results indicate that both anti-Stx2e IgY and anti-Stx2e B IgY could protect mice from Stx2e challenge. Therefore, anti-Stx2e IgY or anti-Stx2e B IgY might be considered as potential candidate for therapeutics for porcine edema disease.     

Genomic and Structural Characterization of Kunitz-Type Peptide LmKTT-1a Highlights Diversity and Evolution of Scorpion Potassium Channel Toxins

Background

Recently, a new subfamily of long-chain toxins with a Kunitz-type fold was found in scorpion venom glands. Functionally, these toxins inhibit protease activity and block potassium channels. However, the genomic organization and three-dimensional (3-D) structure of this kind of scorpion toxin has not been reported.

Principal Findings

Here, we characterized the genomic organization and 3-D nuclear magnetic resonance structure of the scorpion Kunitz-type toxin, LmKTT-1a, which has a unique cysteine pattern. The LmKTT-1a gene contained three exons, which were interrupted by two introns located in the mature peptide region. Despite little similarity to other Kunitz-type toxins and a unique pattern of disulfide bridges, LmKTT-1a possessed a conserved Kunitz-type structural fold with one α-helix and two β-sheets. Comparison of the genomic organization, 3-D structure, and functional data of known toxins from the α-KTx, β-KTx, γ-KTx, and κ-KTx subfamily suggested that scorpion Kunitz-type potassium channel toxins might have evolved from a new ancestor that is completely different from the common ancestor of scorpion toxins with a CSα/β fold. Thus, these analyses provide evidence of a new scorpion potassium channel toxin subfamily, which we have named δ-KTx.

Conclusions/Significance

Our results highlight the genomic, structural, and evolutionary diversity of scorpion potassium channel toxins. These findings may accelerate the design and development of diagnostic and therapeutic peptide agents for human potassium channelopathies.     

Virucidal activity of a scorpion venom peptide variant mucroporin-M1 against measles, SARS-CoV and influenza H5N1 viruses

Outbreaks of SARS-CoV, influenza A (H5N1, H1N1) and measles viruses in recent years have raised serious concerns about the measures available to control emerging and re-emerging infectious viral diseases. Effective antiviral agents are lacking that specifically target RNA viruses such as measles, SARS-CoV and influenza H5N1 viruses, and available vaccinations have demonstrated variable efficacy. Therefore, the development of novel antiviral agents is needed to close the vaccination gap and silence outbreaks. We previously indentified mucroporin, a cationic host defense peptide from scorpion venom, which can effectively inhibit standard bacteria. The optimized mucroporin-M1 can inhibit gram-positive bacteria at low concentrations and antibiotic-resistant pathogens. In this investigation, we further tested mucroporin and the optimized mucroporin-M1 for their antiviral activity. Surprisingly, we found that the antiviral activities of mucroporin-M1 against measles, SARS-CoV and influenza H5N1 viruses were notably increased with an EC₅₀ of 7.15 μg/ml (3.52 μM) and a CC₅₀ of 70.46 μg/ml (34.70 μM) against measles virus, an EC₅₀ of 14.46 μg/ml (7.12 μM) against SARS-CoV and an EC₅₀ of 2.10 μg/ml (1.03 μM) against H5N1, while the original peptide mucroporin showed no antiviral activity against any of these three viruses. The inhibition model could be via a direct interaction with the virus envelope, thereby decreasing the infectivity of virus. This report provides evidence that host defense peptides from scorpion venom can be modified for antiviral activity by rational design and represents a practical approach for developing broad-spectrum antiviral agents, especially against RNA viruses.     

Association mapping in an elite maize breeding population

Association mapping (AM) is a powerful approach to dissect the genetic architecture of quantitative traits. The main goal of our study was to empirically compare several statistical methods of AM using data of an elite maize breeding program with respect to QTL detection power and possibility to correct for population stratification. These models were based on the inclusion of cofactors (Model A), cofactors and population effect (Model B), and SNP effects nested within populations (Model C). A total of 930 testcross progenies of an elite maize breeding population were field-evaluated for grain yield and grain moisture in multi-location trials and fingerprinted with 425 SNP markers. For grain yield, population stratification was effectively controlled by Model A. For grain moisture with a high ratio of variance among versus within populations, Model B should be applied in order to avoid potential false positives. Model C revealed large differences among allele substitution effects for trait-associated SNPs across multiple plant breeding populations. This heterogeneous SNP allele substitution effects have a severe impact for genomic selection studies, where SNP effects are often assumed to be independent of the genetic background.     

Construction and characterization of the chimeric antibody 8C11 to the hepatitis E virus

Homodimers of the truncated hepatitis E virus (HEV) capsid proteins, E2 and p239, were conformed to model the dominant antigenic determinants of HEV. Using E2 as an immunogen, two neutralizing monoclonal antibodies (mAbs), namely 8C11 and 8H3, were produced. We constructed a mouse-human chimeric antibody derived from 8C11 and its expression in Chinese hamster ovary (CHO) cells. cDNAs encoding variable regions of heavy and light chains were isolated from hybridoma cells and inserted into mammalian expression vectors containing cDNA of human gamma-1 and kappa constant regions, respectively. The vectors were then cotransfected into CHO cells, and a stable cell line was established. Results from indirect enzyme-linked immunosorbent assay (ELISA) and Western blot analysis showed that the chimeric antibody was assembled correctly to the native IgG molecule and could be secreted from the cells. Similar to the original mAb, the expressed chimeric antibody displayed HEV antigen-binding activity and an enhancement effect on 8H3 binding to HEV antigen. The chimeric antibody could specifically inhibit the binding of p239 to HepG2 cells and compete with HEV IgG in positive serum by antibody-competitive ELISA. The chimeric antibody is expected to be less immunogenic in human and more suitable for antibody therapy of hepatitis E.     

Evidence for the existence of a robust pattern of prey selection in food webs

Food webs aim to provide a thorough representation of the trophic interactions found in an ecosystem. The complexity of empirical food webs, however, is leading many ecologists to focus dynamic ecosystem studies on smaller microcosm or mesocosm studies based upon community modules, which comprise three to five species and the interactions likely to have ecological relevance. We provide here a structural counterpart to community modules. We investigate food-web 'motifs' which are n-species connected subgraphs found within the food web. Remarkably, we find that the over- and under-representation of three-species motifs in empirical food webs can be understood through comparison to a static food-web model, the niche model. Our result conclusively demonstrates that predation upon species with some 'characteristic' niche value is the prey selection mechanism consistent with the structural properties of empirical food webs.     

Genotypic correlations and QTL correspondence between line per se and testcross performance in sugar beet (Beta vulgaris L.) for the three agronomic traits beet yield,potassium content,and sodium content

The genotypic correlation between line per se and testcross performance is an important quantitative genetic parameter in the design of hybrid breeding programs. The main goal of this survey was to study the association of line per se and testcross performance at the phenotypic and molecular levels by applying multiple-line cross quantitative trait locus (QTL) mapping. We used experimental data from line per se and testcross performance of three segregating sugar beet (Beta vulgaris L.) populations. The segregating progenies were genotyped with 481 single nucleotide polymorphism and 40 simple sequence repeat markers and evaluated in field trials for beet yield as well as potassium and sodium content. We observed a decrease in the genotypic correlations between testcross and line per se performance with increasing complexity of the analyzed trait. This picture was also reflected at a molecular level by the presence of overlapping QTLs. A more detailed analysis of the forces causing low genotypic correlation between line per se and testcross performance could not rule out a possible relevance of epistasis and suggested the presence of masking dominance effects.     

Functional Changes in Pulmonary Arterial Endothelial Cells Associated with BMPR2 Mutations

Pulmonary arterial hypertension (PAH) is a devastating disease characterized by abnormal remodeling of small, peripheral pulmonary arteries. Germline mutations in the bone morphogenetic protein receptor type 2 (BMPR2) gene are a major risk factor for developing PAH. At present, the correlation between the BMPR2 mutation and the patient''s prognosis remains controversial despite several investigations. In this study, we explored the functional effects of four BMPR2 mutations to dissect the functional significance of the BMPR2 gene defect. Cellular immunofluorescence assay of four mutants (Tyr67Cys, Thr268fs, Ser863Asn, and Gln433X) revealed that the BMPR2 protein containing Thr268fs, Ser863Asn, or Gln433X exhibited abnormal subcellular localization. The BrdU incorporation and TUNEL assay suggested that any of the BMPR2 mutations Thr268fs, Ser863Asn, or Gln433X could improve endothelial cell apoptosis and decrease cell proliferation. All of the four mutants could inhibit nitric oxide (NO) synthesis in HLMVE cells, and ET-1 levels increased in the cells transfected with mutant Ser863Asn. Our results will improve the understanding of the genotype-phenotype correlations and mechanisms associated with BMPR2 mutations.