Azithromycin, a 15-membered macrolide antibiotic, inhibits influenza A(H1N1)pdm09 virus infection by interfering with virus internalization process

The pandemic influenza 2009 (A(H1N1)pdm09) virus currently causes seasonal and annual epidemic outbreaks. The widespread use of anti-influenza drugs such as neuraminidase and matrix protein 2 (M2) channel inhibitors has resulted in the emergence of drug-resistant influenza viruses. In this study, we aimed to determine the anti-influenza A(H1N1)pdm09 virus activity of azithromycin, a re-positioned macrolide antibiotic with potential as a new anti-influenza candidate, and to elucidate its underlying mechanisms of action. We performed in vitro and in vivo studies to address this. Our in vitro approaches indicated that progeny virus replication was remarkably inhibited by treating viruses with azithromycin before infection; however, azithromycin administration after infection did not affect this process. We next investigated the steps inhibited by azithromycin during virus invasion. Azithromycin did not affect attachment of viruses onto the cell surface, but blocked internalization into host cells during the early phase of infection. We further demonstrated that azithromycin targeted newly budded progeny virus from the host cells and inactivated their endocytic activity. This unique inhibitory mechanism has not been observed for other anti-influenza drugs, indicating the potential activity of azithromycin before and after influenza virus infection. Considering these in vitro observations, we administered azithromycin intranasally to mice infected with A(H1N1)pdm09 virus. Single intranasal azithromycin treatment successfully reduced viral load in the lungs and relieved hypothermia, which was induced by infection. Our findings indicate the possibility that azithromycin could be an effective macrolide for the treatment of human influenza.

Mechanism by which the lectin actinohivin blocks HIV infection of target cells

Various lectins have attracted attention as potential microbicides to prevent HIV transmission. Their capacity to bind glycoproteins has been suggested as a means to block HIV binding and entry into susceptible cells. The previously undescribed lectin actinohivin (AH), isolated by us from an actinomycete, exhibits potent in vitro anti-HIV activity by binding to high-mannose (Man) type glycans (HMTGs) of gp120, an envelope glycoprotein of HIV. AH contains 114 aa and consists of three segments, all of which need to show high affinity to gp120 for the anti-HIV characteristic. To generate the needed mechanistic understanding of AH binding to HIV in anticipation of seeking approval for human testing as a microbicide, we have used multiple molecular tools to characterize it. AH showed a weak affinity to Man alpha(1-2)Man, Man alpha(1-2)Man alpha(1-2)Man, of HMTG (Man8 or Man9) or RNase B (which has a single HMTG), but exhibited a strong and highly specific affinity (K(d) = 3.4 x 10(-8) M) to gp120 of HIV, which contains multiple Man8 and/or Man9 units. We have compared AH to an alternative lectin, cyanovirin-N, which did not display similar levels of discrimination between high- and low-density HMTGs. X-ray crystal analysis of AH revealed a 3D structure containing three sugar-binding pockets. Thus, the strong specific affinity of AH to gp120 is considered to be due to multivalent interaction of the three sugar-binding pockets with three HMTGs of gp120 via the "cluster effect" of lectin. Thus, AH is a good candidate for investigation as a safe microbicide to help prevent HIV transmission.

Longispora albida gen. nov., sp. nov., a novel genus of the family Micromonosporaceae

A novel actinomycete strain was isolated from a soil sample collected in Japan by using gellan gum as a solidifying agent. Spore-chains from the short sporophores were straight and each had more than 20 spores per chain. Spores possessed no motility. Cell-wall peptidoglycan contained meso-diaminopimelic acid, glycine, alanine and glutamic acid; whole-cell hydrolysates contained arabinose, galactose and xylose. The acyl type of the peptidoglycan was glycolyl. The predominant menaquinones were MK-10(H(4)) and MK-10(H(6)); MK-10(H(8)) was a minor component. Mycolic acids were not detected. The diagostic phospholipid was phosphatidylethanolamine. Cellular fatty acids included heptadecenoic (C(17 : 1)), 14-methylpentadecanoic (i-C(16 : 0)) and octadecenoic (C(18 : 1)) acids. The G+C content of the DNA was 70 mol%. On the basis of morphogical and chemotaxonomic properties and phylogenetic analysis based on 16S rDNA sequence data, it is proposed that this strain should be classified in a novel genus and species, Longispora albida gen. nov., sp. nov., in the family MICROMONOSPORACEAE: The type strain is K97-0003(T) (=NRRL B-24201(T)=JCM 11711(T)).

Patulibacter minatonensis gen. nov., sp. nov., a novel actinobacterium isolated using an agar medium supplemented with superoxide dismutase, and proposal of Patulibacteraceae fam. nov

A novel Gram-positive bacterial strain, designated KV-614T, was isolated from a soil sample using an agar medium supplemented with superoxide dismutase. Based on 16S rRNA gene sequence analysis, it was found that the strain represented a novel deep-rooting lineage within the class Actinobacteria and clustered with yet-uncultivated bacteria from terrestrial environments and some unidentified strains isolated by unique methods. The most closely related established genus was Conexibacter (92.4% sequence similarity to Conexibacter woesei DSM 14684T). Cells of strain KV-614T were rod-shaped and motile with long flagella. The strain was catalase-positive, oxidase-negative and grew under aerobic conditions. The cell-wall peptidoglycan contained meso-diaminopimelic acid as the diagnostic diamino acid and alanine and glutamic acid. The peptidoglycan acyl type was acetyl. The only detected isoprenoid quinone was demethylmenaquinone with seven isoprene units (DMK-7). Mycolic acids were not detected. The predominant cellular fatty acid was omega9c-octadecenoic acid (C18:1omega9c). Minor components were 12-methyl tetradecanoic acid (anteiso-C15:0) and 14-methyl hexadecanoic acid (anteiso-C17:0). The DNA G+C content was 72 mol%. On the basis of phenotypic and genotypic characteristics, it is proposed that strain KV-614T represents a new genus and a novel species, Patulibacter minatonensis gen. nov., sp. nov., in the class Actinobacteria. The type strain is KV-614T (=NRRL B-24346T=JCM 12834T=NBRC 100761T). The creation of the family Patulibacteraceae fam. nov. is proposed to encompass the genus Patulibacter gen. nov.

Molecular insights into the biosynthesis of guadinomine: a type III secretion system inhibitor

Guadinomines are a recently discovered family of anti-infective compounds produced by Streptomyces sp. K01-0509 with a novel mode of action. With an IC(50) of 14 nM, guadinomine B is the most potent known inhibitor of the type III secretion system (TTSS) of Gram-negative bacteria. TTSS activity is required for the virulence of many pathogenic Gram-negative bacteria including Escherichia coli , Salmonella spp., Yersinia spp., Chlamydia spp., Vibrio spp., and Pseudomonas spp. The guadinomine (gdn) biosynthetic gene cluster has been cloned and sequenced and includes 26 open reading frames spanning 51.2 kb. It encodes a chimeric multimodular polyketide synthase, a nonribosomal peptide synthetase, along with enzymes responsible for the biosynthesis of the unusual aminomalonyl-acyl carrier protein extender unit and the signature carbamoylated cyclic guanidine. Its identity was established by targeted disruption of the gene cluster as well as by heterologous expression and analysis of key enzymes in the biosynthetic pathway. Identifying the guadinomine gene cluster provides critical insight into the biosynthesis of these scarce but potentially important natural products.

Phytohabitans suffuscus gen. nov., sp. nov., an actinomycete of the family Micromonosporaceae isolated from plant roots

An actinomycete strain, K07-0523T, was isolated from the roots of an orchid collected in Okinawa prefecture, Japan. 16S rRNA gene sequence analysis indicated that the new strain belonged to the family Micromonosporaceae and the similarity values between strain K07-0523T and the type species of 24 genera in the family Micromonosporaceae were 93.3–97.7 %. Strain K07-0523T contained d-glutamic acid, glycine, d-alanine, meso-diaminopimelic acid, hydroxydiaminopimelic acid and l-lysine in the cell wall. The major menaquinones were MK-9(H6), MK-10(H4) and MK-10(H6). Galactose, glucose, mannose, ribose and xylose were present in the whole-cell sugars. The acyl type of the peptidoglycan was glycolyl. Major fatty acids were anteiso-C17 : 0, iso-C17 : 0, iso-C16 : 0 and iso-C15 : 0. Phosphatidylethanolamine was detected as the major phospholipid and corresponded to phospholipid type II. The G+C content of the genomic DNA was 73 mol%. On the basis of phylogenetic and chemotaxonomic data, the new strain represents a member of a new genus and novel species, namely Phytohabitans suffuscus gen. nov., sp. nov., in the family Micromonosporaceae. The type strain of the type species is K07-0523T (=DSM 45306T=NBRC 105367T).

Trehangelins A, B and C, novel photo-oxidative hemolysis inhibitors produced by an endophytic actinomycete, Polymorphospora rubra K07-0510

Three new natural products, designated trehangelins A, B and C, were isolated by solvent extraction, silica gel and octadecylsilyl silica gel column chromatographies and subsequent preparative HPLC from the cultured broth of an endophytic actinomycete strain, Polymorphospora rubra K07-0510. The trehangelins consisted of a trehalose moiety and two angelic acid moieties. Trehangelins A (IC50 value, 0.1 mg ml(-1)) and C (IC50 value, 0.4 mg ml(-1)), with symmetric structures, showed potent inhibitory activity against hemolysis of red blood cells induced by light-activated pheophorbide a. However, trehangelin B, with an asymmetric structure, displayed only a slight inhibition (IC50 value, 1.0 mg ml(-1)).