Rudimentary phosvitin domain in a minor chicken vitellogenin gene

We have determined the nucleotide sequence and the derived amino acid sequence of the phosphoprotein-encoding region of the chicken vitellogenin III gene. The sequence of this minor vitellogenin could be aligned with exon 22 up to exon 27 of the previously sequenced major vitellogenin II gene (van het Schip et al., 1987). The exon 23 and 25 sequences are rich in serine codons (26% and 41%, respectively), and this region encodes at least one of the small egg yolk phosphoproteins. The major egg yolk phosphoprotein, phosvitin, is encoded by the analogous region in vitellogenin II. Comparison of the vitellogenin II and vitellogenin III sequences shows a great reduction in the size of the putative exon 23 of the latter (321 base pairs as opposed to 690). The number of serine codons is also drastically reduced from 124 in exon 23 of the vitellogenin II gene to 28 in vitellogenin III. The grouping of synonymous serine codons, as has hitherto been observed in sequenced vitellogenin phosphoproteins, has been maintained in vitellogenin III. A putative asparagine-linked N-glycosylation site which was conserved in the chicken vitellogenin II and the Xenopus laevis vitellogenin A2 gene, at the beginning of exon 23, is also present in vitellogenin III. The two chicken vitellogenins show a low conservation in the phosphoprotein-encoding region (average 33%, at the protein level) compared to that in the peripheral sequences (58% identity), which indicates that it is a rapidly evolving domain of the vertebrate vitellogenin gene.     

Molecular cloning and characterization of an alpha1,3 fucosyltransferase, CEFT-1, from Caenorhabditis elegans

We report on the identification, molecular cloning, and characterization of an alpha1,3 fucosyltransferase (alpha1,3FT) expressed by the nematode, Caenorhabditis elegans . Although C. elegans glycoconjugates do not express the Lewis x antigen Galbeta1-- >4[Fucalpha1-->3]GlcNAcbeta-->R, detergent extracts of adult C.elegans contain an alpha1,3FT that can fucosylate both nonsialylated and sialylated acceptor glycans to generate the Lexand sialyl Lexantigens, as well as the lacdiNAc-containing acceptor GalNAcbeta1-->4GlcNAcbeta1-- >R to generate GalNAcbeta1-->4 [Fucalpha1-->3]GlcNAcbeta1-->R. A search of the C.elegans genome database revealed the existence of a gene with 20-23% overall identity to all five cloned human alpha1,3FTs. The putative cDNA for the C.elegans alpha1,3FT (CEFT-1) was amplified by PCR from a cDNA lambdaZAP library, cloned, and sequenced. COS7 cells transiently transfected with cDNA encoding CEFT-1 express the Lex, but not sLexantigen. The CEFT-1 in the transfected cell extracts can synthesize Lex, but not sialyl Lex, using exogenous acceptors. A second fucosyltransferase activity was detected in extracts of C. elegans that transfers Fuc in alpha1,2 linkage to Gal specifically on type-1 chains. The discovery of alpha-fucosyltransferases in C. elegans opens the possibility of using this well-characterized nematode as a model system for studying the role of fucosylated glycans in the development and survival of C.elegans and possibly other helminths.      

Silica-based cationic bilayers as immunoadjuvants

Background  

Silica particles cationized by dioctadecyldimethylammonium bromide (DODAB) bilayer were previously described. This work shows the efficiency of these particulates for antigen adsorption and presentation to the immune system and proves the concept that silica-based cationic bilayers exhibit better performance than alum regarding colloid stability and cellular immune responses for vaccine design.     

Characterization of a novel influenza A virus hemagglutinin subtype (H16) obtained from black-headed gulls

In wild aquatic birds and poultry around the world, influenza A viruses carrying 15 antigenic subtypes of hemagglutinin (HA) and 9 antigenic subtypes of neuraminidase (NA) have been described. Here we describe a previously unidentified antigenic subtype of HA (H16), detected in viruses circulating in black-headed gulls in Sweden. In agreement with established criteria for the definition of antigenic subtypes, hemagglutination inhibition assays and immunodiffusion assays failed to detect specific reactivity between H16 and the previously described subtypes H1 to H15. Genetically, H16 HA was found to be distantly related to H13 HA, a subtype also detected exclusively in shorebirds, and the amino acid composition of the putative receptor-binding site of H13 and H16 HAs was found to be distinct from that in HA subtypes circulating in ducks and geese. The H16 viruses contained NA genes that were similar to those of other Eurasian shorebirds but genetically distinct from N3 genes detected in other birds and geographical locations. The European gull viruses were further distinguishable from other influenza A viruses based on their PB2, NP, and NS genes. Gaining information on the full spectrum of avian influenza A viruses and creating reagents for their detection and identification will remain an important task for influenza surveillance, outbreak control, and animal and public health. We propose that sequence analyses of HA and NA genes of influenza A viruses be used for the rapid identification of existing and novel HA and NA subtypes.     

Vif and the p55(Gag) polyprotein of human immunodeficiency virus type 1 are present in colocalizing membrane-free cytoplasmic complexes

The Vif protein of human immunodeficiency virus type 1 (HIV-1) is a potent regulator of viral infectivity. Current data posit that Vif functions late in replication to modulate assembly, budding, and/or maturation. Consistent with this model, earlier indirect immunofluorescence analyses of HIV-1-infected cells demonstrated that Vif and Gag colocalize to a substantial degree (J. H. M. Simon, R. A. M. Fouchier, T. E. Southerling, C. B. Guerra, C. K. Grant, and M. H. Malim, J. Virol. 71:5259-5267, 1997). Here, we describe a series of subcellular fractionation studies which indicate that Vif and the p55(Gag) polyprotein are present in membrane-free cytoplasmic complexes that copurify in sucrose density gradients and are stable in nonionic detergents. Both Vif and Gag are targeted to these complexes independent of each other, and their association with them appears to be mediated by protein-protein interactions. We propose that these complexes may represent viral assembly intermediates and that Vif is appropriately localized to influence the final stages of the viral life cycle and, therefore, the infectivity of progeny virions.     

Recolonization history and large-scale dispersal in the open sea: the case study of the North Atlantic cod, Gadus morhua L.

Most studies of the genetic structure of Atlantic cod have focused on small geographical scales. In the present study, the genetic structure of cod sampled on spawning grounds in the North Atlantic was examined using eight microsatellite loci and the Pan I locus. A total of 954 cod was collected from nine different regions: the Baltic Sea, the North Sea, the Celtic Sea, the Irish Sea and Icelandic waters during spring 2002 and spring 2003, from Norwegian waters and the Faroe Islands (North and West spawning grounds) in spring 2003, and from Canadian waters in 1998. Temporal stability among spawning grounds was observed in Icelandic waters and the Celtic Sea, and no significant difference was observed between the samples from the Baltic Sea and between the samples from Faroese waters. F -statistics showed significant differences between most populations and a pattern of isolation-by-distance was described with microsatellite loci. The Pan I locus revealed the presence of two genetically distinguishable basins, the North-west Atlantic composed of the Icelandic and Canadian samples and the North-east Atlantic composed of all other samples. Permutation of allele sizes at each microsatellite locus among allelic states supported a mutational component to the genetic differentiation, indicating a historical origin of the observed variation. Estimation of the time of divergence was approximately 3000 generations, which places the origin of current genetic pattern of cod in the North Atlantic in the late Weichselian (Wisconsinian period), at last glacial maximum.  © 2008 The Linnean Society of London, Biological Journal of the Linnean Society , 2008, 94 , 315–329.     

Disease dynamics and bird migration--linking mallards Anas platyrhynchos and subtype diversity of the influenza A virus in time and space

The mallard Anas platyrhynchos is a reservoir species for influenza A virus in the northern hemisphere, with particularly high prevalence rates prior to as well as during its prolonged autumn migration. It has been proposed that the virus is brought from the breeding grounds and transmitted to conspecifics during subsequent staging during migration, and so a better understanding of the natal origin of staging ducks is vital to deciphering the dynamics of viral movement pathways. Ottenby is an important stopover site in southeast Sweden almost halfway downstream in the major Northwest European flyway, and is used by millions of waterfowl each year. Here, mallards were captured and sampled for influenza A virus infection, and positive samples were subtyped in order to study possible links to the natal area, which were determined by a novel approach combining banding recovery data and isotopic measurements (δ(2)H) of feathers grown on breeding grounds. Geographic assignments showed that the core natal areas of studied mallards were in Estonia, southern and central Finland, and northwestern Russia. This study demonstrates a clear temporal succession of latitudes of natal origin during the course of autumn migration. We also demonstrate a corresponding and concomitant shift in virus subtypes. Acknowledging that these two different patterns were based in part upon different data, a likely interpretation worth further testing is that the early arriving birds with more proximate origins have different influenza A subtypes than the more distantly originating late autumn birds. If true, this knowledge would allow novel insight into the origins and transmission of the influenza A virus among migratory hosts previously unavailable through conventional approaches.     

The Vif and Gag proteins of human immunodeficiency virus type 1 colocalize in infected human T cells.

The Vif protein of human immunodeficiency virus type 1 (HIV-1) and other lentiviruses is required for efficient replication in primary cells and certain immortalized cell lines in vitro and, in all likelihood, for the establishment of pathogenic infections in vivo. Current hypotheses concerning Vif's mechanism of action posit that it operates in virus-expressing cells during virion assembly, budding, or maturation such that released virions are modified in a manner that enables them to undergo productive infection in subsequent viral challenges. To gain further insight into the mechanism of action of lentivirus Vif proteins, we have performed a variety of in situ localization and biochemical fractionation studies using cells in which Vif is essential for efficient replication. Double-label immunofluorescence analyses of cells productively infected with HIV-1 or feline immunodeficiency virus revealed dramatic patterns of colocalization between Vif and the virally encoded Gag proteins. Subcellular fractionations of human T cells expressing HIV-1 Vif performed in the absence of any detergent demonstrated that greater than 90% of Vif is associated with cellular membranes. Additional purification using a continuous density gradient indicated that the majority of the membrane-bound Vif copurifies with the plasma membrane. Taken together, these observations suggest that lentivirus Vif and Gag proteins colocalize at the plasma membrane as virion assembly and budding take place. As a result, Vif is able to exert its modulatory effect(s) on these late steps of the virus life cycle.     

Oviposition preferences of Maculinea alcon as influenced by aphid (Aphis gentianae) and fungal (Puccinia gentianae) infestation of larval host plants

Abstract 1. The influence of infestation of the larval host plant Gentiana cruciata on the egg‐laying preferences of the xerophilous ecotype of Alcon Blue butterfly (Maculinea alcon) was studied in a semi‐dry grassland area (Aggtelek Karst Region, Northern Hungary). 2. We examined whether oviposition patterns of females differed when G. cruciata stems were uninfested compared with when they were infested by an aphid (Aphis gentianae) or a rust (Puccinia gentianae) species. 3. Females laid more than 90% of their eggs on fertile, uninfested G. cruciata stems, although these stems comprised only ～ 50% of the total stems available. Stems infested by aphids were similar to uninfested ones in properties that had a strong correlation with egg numbers, and yet there were significantly fewer eggs on infested stems than on intact ones. 4. Females never laid eggs on parts of Gentiana stems infested by aphids, and the presence of Lasius paralienus ants, which have a mutualistic interaction with Aphis gentianae, did not increase the repulsive effect of aphids. Infection of Gentiana by Puccinia did not influence the egg‐laying behaviour of females, even though the flowers and buds of infested stems exhibited a delayed development. 5. Aphid infestation can influence butterfly oviposition patterns through both direct and indirect effects. The presence of aphids directly excluded oviposition, but our data also indicated the possibility of an indirect effect of aphid infestation. Stems that had no aphids at the last egg counting, but were infested prior to it, had significantly fewer eggs than those that were never infested.