Selective delivery of rifampicin incorporated into poly(DL-lactic-co-glycolic) acid microspheres after phagocytotic uptake by alveolar macrophages, and the killing effect against intracellular Mycobacterium bovis Calmette-Guérin

Macrophages and their phagocytotic abilities play a dominant role for defense against infected organisms. However, Mycobacterium tuberculosis can survive in the phagosomes of macrophages. In this study, the effective delivery of a drug and the killing effect of tubercle bacilli within macrophages were investigated utilizing the phagocytotic uptake of rifampicin (RFP) that had been incorporated into poly(DL-lactic-co-glycolic) acid (PLGA) microspheres. The microspheres were composed of PLGA that had a monomer ratio (lactic acid/glycolic acid) of either 50/50 or 75/25. They had molecular weights from 5000 to 20,000, and diameters of 1.5, 3.5, 6.2 and 8.9 microm. The most significant factor for phagocytotic activity of macrophages was the diameter of the microspheres. By contrast, molecular weight and monomer ratio of PLGA did not influence phagocytosis. The amount of RFP delivered into cells was also investigated. RFP-PLGA microspheres composed of PLGA with a molecular weight of 20,000 and monomer ratio of 75/25 showed the highest amount of delivery (4 microg/1 x 10(6) cells). Fourteen days after infection, the survival rate of treated intracellular bacilli was 1% when compared with untreated cells. There was almost no killing effect of free RFP (4 or 15 microg/ml) on intracellular bacilli. In vivo efficacy of RFP-PLGA was also examined in rats infected with M. tuberculosis Kurono. Intratracheal administration of RFP-PLGA microspheres was shown to be superior to free RFP for killing of intracellular bacilli and preventing granuloma formation in some lobes. These results suggest that phagocytotic activity could be part of a new drug delivery system that selectively targeted macrophages.     

Identification of a human monoclonal Fab with neutralizing activity against H3N2 influenza A strain from a newly constructed human Fab library

A combinatorial Fab library was constructed in pComb3H phagemid vectors, using RNA from peripheral blood lymphocytes of a healthy volunteer who had recovered from an influenza A virus infection. The library contained approximately 1.3 x 10(8)E. coli transformants. Bio-panning was carried out against an influenza vaccine containing components of influenza A/New Caledonia/20/99 (H1N1), A/Panama/2007/99 (H3N2), and B/Shandong/7/97 for the enrichment of phages displaying human Fab specific to the viral proteins. E. coli transformed with IF1A11, 1 of 94 randomly selected clones, displayed a human Fab antibody molecule (FabIF1A11) with efficient neutralizing activity against H3N2 influenza A virus strains. The purified FabIF1A11 demonstrated neutralizing activity against A/Okayama/6/01 (H3N2) and A/Kitakyushu/159/93 (H3N2) with 50% plaque reduction neutralization titers of 0.11 microg/ml (2.2 nM) and 1.4 microg/ml (28 nM) respectively. However, FabIF1A11 did not show neutralizing activity against the influenza A virus strain A/USSR/77 (H1N1) or the influenza B virus strain B/Kanagawa/73, even at a concentration of 20 microg/ml (400 nM). The Kd of FabIF1A11 was calculated as 3.6 x 10(-9) M. FabIF1A11 was estimated to recognize a conformational epitope on the hemagglutinin of A/Okayama/6/01 (H3N2). The human monoclonal Fab product FabIF1A11 may have potential as a therapeutic or short-term prophylactic molecule for humans with influenza A H3N2 infection.     

Acylated flavanols and procyanidins from Salix sieboldiana

An homologous series of acylated flavan-3-ols and procyanidins have been isolated, together with the known procyanidins B-1, B-3 and trimer, from the bark of Salix sieboldiana. Chemical and spectroscopic evidence led to the assignments of their structures as the 3-O-(1,6-dihydroxy-2-cyclohexene-1-carboxylic acid ester) of (+)-catechin and the 1-hydroxy-6-oxo-2-cyclohexene carboxylic acid esters of (+)-catechin and procyanidins B-1, B-3 and trimer.     

Host range of braconid species (Hymenoptera: Braconidae) that attack Asphondyliini (Diptera: Cecidomyiidae) in Japan

We reared six idiobiont braconids, Bracon asphondyliae, B. sunosei, B. tamabae, Simplicibracon curticaudis, Testudobracon longicaudis and T. pleuralis from 22 identified species and 11 unidentified segregates of Asphondyliini (Diptera: Cecidomyiidae) in Japan. A total of 22 cecidomyiid species and segregates were newly recorded as hosts of the braconids. Analysis of cytochrome oxidase subunit I (COI) did not show any evidence of host races among the braconids. Bracon sunosei, which was synonymized with B. asphondyliae, is restored to a valid species. The host range of the braconid species seemed to be related to the lineage of host genera within Asphondyliini.     

Structural dynamics shape the fitness window of alanine:glyoxylate aminotransferase

The conformational landscape of a protein is constantly expanded by genetic variations that have a minimal impact on the function(s) while causing subtle effects on protein structure. The wider the conformational space sampled by these variants, the higher the probabilities to adapt to changes in environmental conditions. However, the probability that a single mutation may result in a pathogenic phenotype also increases. Here we present a paradigmatic example of how protein evolution balances structural stability and dynamics to maximize protein adaptability and preserve protein fitness. We took advantage of known genetic variations of human alanine:glyoxylate aminotransferase (AGT1), which is present as a common major allelic form (AGT‐Ma) and a minor polymorphic form (AGT‐Mi) expressed in 20% of Caucasian population. By integrating crystallographic studies and molecular dynamics simulations, we show that AGT‐Ma is endowed with structurally unstable (frustrated) regions, which become disordered in AGT‐Mi. An in‐depth biochemical characterization of variants from an anticonsensus library, encompassing the frustrated regions, correlates this plasticity to a fitness window defined by AGT‐Ma and AGT‐Mi. Finally, co‐immunoprecipitation analysis suggests that structural frustration in AGT1 could favor additional functions related to protein–protein interactions. These results expand our understanding of protein structural evolution by establishing that naturally occurring genetic variations tip the balance between stability and frustration to maximize the ensemble of conformations falling within a well‐defined fitness window, thus expanding the adaptability potential of the protein.     

A triangle lattice model that predicts transmembrane helix configuration using a polar jigsaw puzzle

We developed a method of predicting the tertiary structures of seven transmembrane helical proteins in triangle lattice models, assuming that the configuration of helices is stabilized by polar interactions. Triangle lattice models having 12 or 11 nearest neighbor pairs were used as general templates of a seven-helix system, then the orientation angles of all helices were varied at intervals of 15 degrees. The polar interaction energy for all possible positions of each helix was estimated using the calculated polar indices of transmembrane helices. An automated system was constructed and applied to bacteriorhodopsin, a typical membrane protein with seven transmembrane helices. The predicted optimal and actual structures were similar. The top 100 predicted helical configurations indicated that the helix-triangle, CFG, occurred at the highest frequency. In fact, this helix-triangle of bacteriorhodopsin forms an active proton-pumping site, suggesting that the present method can identify functionally important helices in membrane proteins. The possibility of studying the structure change of bacteriorhodopsin during the functional process by this method is discussed, and may serve to explain the experimental structures of photointermediate states.