LSECtin interacts with filovirus glycoproteins and the spike protein of SARS coronavirus

Cellular attachment factors like the C-type lectins DC-SIGN and DC-SIGNR (collectively referred to as DC-SIGN/R) can augment viral infection and might promote viral dissemination in and between hosts. The lectin LSECtin is encoded in the same chromosomal locus as DC-SIGN/R and is coexpressed with DC-SIGNR on sinusoidal endothelial cells in liver and lymphnodes. Here, we show that LSECtin enhances infection driven by filovirus glycoproteins (GP) and the S protein of SARS coronavirus, but does not interact with human immunodeficiency virus type-1 and hepatitis C virus envelope proteins. Ligand binding to LSECtin was inhibited by EGTA but not by mannan, suggesting that LSECtin unlike DC-SIGN/R does not recognize high-mannose glycans on viral GPs. Finally, we demonstrate that LSECtin is N-linked glycosylated and that glycosylation is required for cell surface expression. In summary, we identified LSECtin as an attachment factor that in conjunction with DC-SIGNR might concentrate viral pathogens in liver and lymph nodes.     

Immature B cells from human and mouse bone marrow can change their surface light chain expression

The capacity of bone marrow-derived surface immunoglobulin-positive (sIg⁺) human and mouse immature B cells, generated either in vitro or in vivo, to change their light (L) chain expression, has been assayed by the number of cells which change in vitro from one type of L chain to the other type, or to no sIg at all. Immature sIg⁺ B cells were generated in vitro from sIg^? precursor cells from human or mouse bone marrow. The immature sIg⁺ cells expressed RAG-1. Human sIg⁺ cells expressed xfr; and λ L chains in ratios between 1:1 and 3:1, whereas in mouse cells, this ratio ranged from 10:1 to 20:1. Upon reculture of the human and mouse xfr;⁺sIg⁺ cells, about half of them remained xfr;⁺, a quarter became λ⁺, and another quarter became sIg^?. Between 1 and 3% expressed both xfr; and λ chains. Of the human λ⁺ cells, about two-thirds remained λ⁺, only 1 to 2% became xfr;⁺, while the other third became sIg^?. Again, between 1 and 3% expressed both xfr; and λ L chains. These results indicate that expression of sIgM in the B cell membrane does not terminate L chain gene rearrangement, and that some order exists in xfr; versus λ gene rearrangements. Hence, human and mouse xfr;⁺ immature B cells can become λ⁺, but very few of the λ⁺ cells can become xfr;⁺, and both can become sIg^?. Further, human CD10⁺/sIg⁺ xfr;⁺ and λ⁺ cells and mouse B220^low/sIg^low xfr;⁺ cells enriched from bone marrow, i.e. immature B cells differentiated in vivo, changed their Ig phenotype upon in vitro culture, but in lower frequencies. By contrast, human and mouse mature B cells did not change their L chain or Ig phenotype. Hence, at least a part of the sIg⁺ immature B cells in bone marrow retain the capacity to change their L chain and Ig phenotype, and this capacity is lost when they become mature, peripheral B cells.     

Distribution of actin and myosin in a rat neuronal cell line infected with herpes simplex virus

Summary The indirect immunofluorescence technique was used to study alterations in the distribution of actin and myosin filaments in a rat B 103 neuronal cell line infected with herpes simplex virus type 1 (HSV-1). In uninfected cells, actin filaments were arranged in parallel and ran lengthwise from one end of the cell to the other; although myosin filaments were closely associated with actin filaments, additional myosin formed a netlike distribution which did not stain for actin. In infected cells, actin filaments became more randomly aligned and were concentrated along with myosin in close association with rosette-like formations of nuclei in syncytial cells; structural organization of actin and myosin within these intensely staining areas was no longer evident. The possible role of contractile proteins (actin and myosin) in viral infections of neural tissue is raised.With 3 Figures     

Sterilitätsbehandlung mit donogener Insemination

Donor inseminations (DI) have been performed for decades. Most of the publications on this topic deal only with problems of tolerance and acceptance of this treatment for sterility. We already reported on them in parts I and II. In the present third and last part, we discuss the indications for DI: male infertility, genetic disorders, and unsuccessful assisted reproduction therapy. Which conditions do affect the success of therapy? Which methods are recommended? Our treatment results verify realistically that in effect DI only produces the desired child in about 50 % of the couples. As a complementary therapy, in vitro fertilization (IVF) with donor spermatozoa offers a real chance for pregnancy even for women whose husbands are infertile and who themselves suffer from impaired fertility such as pathological conditions of the fallopian tube or when simple inseminations have not resulted in pregnancy. After receiving consent from the State Physicians’ Chamber, we treated 19 women by donor IVF in our group practice and fulfilled their desire to bear their own child.     

Ultrastructural morphometric investigation of early lesions in the pulmonary alveolar region of pigs during experimental swine influenza infection.

Experimental infection of specific-pathogen-free pigs with swine influenza virus by the intratracheal route resulted in a severe respiratory disease that closely resembled natural swine influenza in clinical course and pathologic lesions. Alveolar epithelial necrosis with sloughing of necrotic cells occurred from 24 to 96 hours after inoculation (p.i.) and was associated with alveolar edema and diffuse interstitial pneumonitis. The latter, initially of neutrophilic character, became histiocytic 48 hours p.i. Ultrastructural analysis of alveolar parenchyma disclosed viral replication in epithelial cells beginning at 5 hours p.i. and lasting to 96 hours. Budding of pleomorphic virus particles from the surface of alveolar epithelial cells and accumulation of viral proteins within the nucleus and cytoplasm of epithelial cells were seen. The extent of parenchymal lesions as quantified by stereologic morphometry within the whole lung was characterized by a marked relative and absolute volume increase of interalveolar septa and increased air-blood tissue barrier thickness. The volume increase of interalveolar septa was due to an increase of interstitial tissue volume by 85% in pigs at 96 hours p.i., compared with control pigs with similar lung volumes.     

Identification of a galactose-binding lectin on Fusobacterium nucleatum FN-2.

A previous study has suggested that Fusobacterium nucleatum FN-2 contains a galactose-binding protein (lectin) on the cell surface (P. A. Murray, V. Matarese, C. I. Hoover, and J. R. Winkler, FEMS Microbiol. Lett. 40:123-127, 1987). In the present study, the molecular specificity and size of this lectin were investigated by several techniques. Whole-cell affinity chromatography with asialofetuin covalently coupled to Sepharose 6MB demonstrated that 81% of 3H-labeled F. nucleatum were specifically eluted by 0.5 M galactose. Specific binding was calcium dependent and did not occur in the presence of calcium chelators. Binding was inhibited by preincubation with galactose. Agglutination of human parotid saliva by F. nucleatum was also inhibited by galactose and its structural analogs. Inhibition by lactose was 2 times that of galactose, inhibition by p-aminophenyl galactosides was 4 times that of galactose, and inhibition by asialoglycopeptides was 100 times that of galactose. Similar inhibition results were obtained for hemagglutination of neuraminidase-treated erythrocytes. These findings suggest that the binding specificity of F. nucleatum FN-2 is more complex than simply the recognition of the monosaccharide galactose. This is consistent with the concept that lectins considered identical in terms of monosaccharide specificity can recognize fine differences in more complex structures. To identify the specific bacterial component(s) involved in galactose recognition, proteins of F. nucleatum FN-2 were separated on a 4 to 11% gradient sodium dodecyl sulfate slab gel, transferred to nitrocellulose paper to renature bacterial binding sites, and then incubated with 125I-labeled asialofetuin. Autoradiographs of the nitrocellulose revealed a band at a range of Mr 300,000 to 330,000 which was not present when the blots were preincubated with galactose. These data support the concept that F. nucleatum FN-2 possesses a lectin that recognizes galactose and galactose-containing substrates.