Baculovirus expression of the M genome segment of Rift Valley fever virus and examination of antigenic and immunogenic properties of the expressed proteins

Autographa californica nuclear polyhedrosis viral recombinants containing coding information for the Rift Valley fever virus (RVFV) envelope glycoproteins (G1 and G2) and varying amounts of preglycoprotein coding sequences were prepared by using transfer vectors pAc373 or pAcYM1. Expression products were processed to yield proteins indistinguishable from authentic G1 and G2 by gel electrophoresis. The immunogenic properties of the expressed proteins were assessed by immunizing mice and challenging with RVFV. A single inoculation with lysates of cells infected with recombinants expressing both G1 and G2 induced neutralizing antibody responses in mice and protected them from an otherwise lethal challenge with RVFV. Lysates of cells infected with a recombinant expressing only G2 also induced a protective response after two immunizations. Survivors displayed elevated antibody titers to G1 and G2 and also developed antibodies to the RVFV nucleocapsid protein, the latter allowing discrimination from vaccinated mice and indicating that animals had survived infection. Nonimmune mice were protected from lethal RVFV infection by passive transfer of sera from animals immunized with recombinant antigens, indicating that a humoral immune response is sufficient to protect against RVFV.

Mapping of neutralizing epitopes to fragments of the bovine coronavirus E2 protein by proteolysis of antigen-antibody complexes

Neutralizing antigenic domains on bovine coronavirus gp100/E2 were mapped to fragments of this protein by proteolytic cleavage and fragment analysis. The procedure involved analysis of fragments generated after incubation of E2-monoclonal antibody complexes with various proteases. The smallest antibody-bound fragments obtained were a 50K fragment following Staphylococcus aureus V8 protease and submaxillary protease digestion, and a 37K fragment following trypsin digestion. Trypsin also produced a transient antibody-bound 50K fragment. A 40K fragment which was not bound by antibody was observed following digestions with all three proteases. The 50K fragments generated by V8, submaxillary protease and trypsin comigrated on gels and displayed the same altered mobility under non-reducing conditions, suggesting identity of these fragments and indicating the presence of disulphide linkages in these fragments. The 40K fragments generated by these three enzymes also comigrated and displayed the same altered mobility under non-reducing conditions. The 37K trypsin fragment contained both neutralizing domains, A and B.

Cloning and in vitro expression of the gene for the E3 haemagglutinin glycoprotein of bovine coronavirus

A cDNA clone representing the gene for the E3 glycoprotein, the haemagglutinin, of bovine coronavirus was isolated from a plasmid cDNA library of the viral genome and sequenced. The gene is located immediately 5' of the E2 glycoprotein gene on the viral genome. Nucleotide sequencing of the E3 gene predicts a polypeptide of 424 amino acids with an Mr of 47K. In vitro translation of mRNA transcribed from the cloned E3 gene yielded a polypeptide of Mr 45K, similar to that predicted from the nucleotide sequence. In the presence of microsomal membranes, the in vitro product was cotranslationally processed to a 62K polypeptide which comigrated on SDS-polyacrylamide gels with the E3 monomer (gp62) obtained from virus-infected cells. Both the 45K and 62K polypeptides were immunoprecipitated with E3-specific monoclonal antibodies, confirming the identity of the gene as that encoding the E3 glycoprotein. Finally, only monoclonal antibodies to the E3 protein inhibited haemagglutination by the virus thus confirming its identity as the haemagglutinin of bovine coronavirus.

Expression of bovine herpesvirus 1 glycoproteins gI and gIII in transfected murine cells

Genes encoding two of the major glycoproteins of bovine herpesvirus 1 (BHV-1), gI and gIII, were cloned into the eucaryotic expression vectors pRSVcat and pSV2neo and transfected into murine LMTK- cells, and cloned cell lines were established. The relative amounts of gI or gIII expressed from the two vectors were similar. Expression of gI was cell associated and localized predominantly in the perinuclear region, but nuclear and plasma membrane staining was also observed. Expression of gI was additionally associated with cell fusion and the formation of polykaryons and giant cells. Expression of gIII was localized predominantly in the nuclear and plasma membranes. Radioimmunoprecipitation in the presence or absence of tunicamycin revealed that the recombinant glycoproteins were proteolytically processed and glycosylated and had molecular weights similar to those of the forms of gI and gIII expressed in BHV-1-infected bovine cells. However, both recombinant glycoproteins were glycosylated to a lesser extent than were the forms found in BHV-1-infected bovine cells. For gI, a deficiency in N-linked glycosylation of the amino-terminal half of the protein was identified; for gIII, a deficiency in O-linked glycosylation was implicated. The reactivity pattern of a panel of gI- and gIII-specific monoclonal antibodies, including six which recognize conformation-dependent epitopes, was found to be unaffected by the glycosylation differences and was identical for transfected or BHV-1-infected murine cells. Use of the transfected cells as targets in immune-mediated cytotoxicity assays demonstrated the functional recognition of recombinant gI and gIII by murine antibody and cytotoxic T lymphocytes. Immunization of mice with the transfected cells elicited BHV-1-specific virus-neutralizing antibody, thus verifying the antigenic authenticity of the recombinant glycoproteins and the important role of gI and gIII as targets of the immune response to BHV-1 in this murine model system.

Gene mapping and positive identification of the non-structural proteins NS2A, NS2B, NS3, NS4B and NS5 of the flavivirus Kunjin and their cleavage sites

Partial N-terminal amino acid analyses of five radiolabelled non-structural (ns) proteins specified by Kunjin (KUN) virus provided positive identification of NS3, NS5 and three previously hypothetical ns proteins of flaviviruses, ns2a, ns2b and ns4b. Their correct gene order was obtained from their deduced amino acid sequences. Thus the gene order for KUN virus relative to that proposed for yellow fever (YF) virus was as follows: KUN 5'...GP44.P19.P10.P71.(?).P21.P98-3', YF 5'...NS1.ns2a.ns2b.NS3.ns4a.ns4b.NS5 -3'. The identity of GP44 as NS1 was assumed from the known nucleotide and deduced amino acid sequences; ns4a was not identified. The cleavage sites in the polyprotein for KUN NS2B, NS3 and NS5 were identical, Lys-Arg decreased Gly, similar in form to the sequence Arg-Arg decreased Ser defined at the cleavage sites of YF NS3 and NS5. A new consensus cleavage site for NS1, NS2A and NS4B in the form Val-X-Ala decreased, where X is any one of several uncharged amino acids, was found at corresponding sites homologous to those of KUN virus in all published flavivirus sequences (a total of 18 sites). NS1 and NS4B, but not NS2A, were preceded by a putative signal sequence.

Nucleotide and complete amino acid sequences of Kunjin virus: definitive gene order and characteristics of the virus-specified proteins

A Kunjin (KUN) virus cDNA sequence of 10664 nucleotides was obtained and it encoded a single open reading frame for 3433 amino acids. Partial N-terminal amino acid analyses of KUN virus-specified proteins identified the polyprotein cleavage sites and the definitive gene order. The gene order relative to that proposed for yellow fever (YF) virus is as follows: KUN 5'-C.GP20.E.GP44.P19.P10.P71.(?).P21.P98-3' YF 5'-C.prM.E.NS1.ns2a.ns2b.NS3.ns4a.ns4b. NS5-3'. The order of putative signal sequences and stop transfer sequences indicated that KUN NS1, NS2A and NS4B are probably cleaved in the lumen of the endoplasmic reticulum, at a consensus site Val-X-Ala decreases where X is an uncharged residue, and NS2B, NS3 and NS5 are cleaved in the cytosol at the site Lys-Arg decreases Gly. Comparisons with the complete amino acid sequences of YF and West Nile (WN) viruses showed that KUN virus shared 93% homology with WN virus, but only 46% homology with YF virus. Comparisons among individual gene products of six flaviviruses showed that E, NS1, NS3 and NS5 tended to be the most highly conserved, and C among the least conserved. Homologous cleavage sites were evident, and six domains in NS5, a total of over 170 residues, shared at least 85% homology. Comparisons with the KUN C to NS2B sequence defined a gradient of relationships of all gene products in decreasing order WN greater than Murray Valley greater than Japanese encephalitis greater than St Louis encephalitis viruses within this closely related serological complex. A non-coding 5' sequence (75 nucleotides) of KUN virus shared 95% homology with WN virus and a shorter imperfect match with Murray Valley encephalitis virus (15 of 18 nucleotides). The KUN non-coding 3' sequence of 290 nucleotides contained several short and imperfectly matched sequences, and shared 87% homology over the distal region of 191 nucleotides with the corresponding region of WN virus RNA.

Identification and molecular analysis of a third Aspergillus nidulans alcohol dehydrogenase gene

An Aspergillus nidulans functional cDNA encoding an alcohol dehydrogenase (ADH) was isolated by its ability to complement an adh1 mutation in Saccharomyces cerevisiae. Alignment of the cDNA and cloned genomic DNA sequences indicated that the ADH gene contains two small introns. The presence of ethanol in the growth medium was shown to result in ADH mRNA accumulation presumably due to transcriptional induction of the gene. However, ADH mRNA accumulation was at most only partially repressed by the presence of glucose. The ADH gene characterized here is designated ADH3 since it is distinct from the alcA gene which encodes ADH I and appears distinct from the gene which encodes ADH II. We demonstrated that the first intron in the A. nidulans ADH3 gene was not efficiently spliced in S. cerevisiae whereas the promoter region was utilized weakly. We also present a comparison of the primary structure of A. nidulans ADH III with the alcohol dehydrogenases of S. cerevisiae and Schizosaccharomyces pombe.

Complete nucleotide sequence of the M RNA segment of Rift Valley fever virus

The entire M RNA segment of the phlebovirus Rift Valley fever virus (RVFV) has been molecularly cloned and the complete nucleotide sequence determined. The RNA is 3884 nucleotides in length, corresponding to a molecular weight of 1.38 X 10(6), having a base composition of 27.3% A, 25.4% G, 27.2% U, and 20.1% C. Sequences present at the 3' and 5' termini of the molecule are largely complementary for some 51 residues and can form a stable duplex structure when the potential secondary structure of the entire molecule is considered. A single major open reading frame, capable of encoding 1206 amino acids (131,845 Da), was found in the viral-complementary sequence ("positive" polarity). Amino-terminal amino acid sequencing of the purified viral glycoproteins G1 and G2 allowed for the positioning of the coding sequences for these polypeptides within this major open reading frame in the following orientation with respect to the genomic M RNA: 3'-G2-G1-5'. From the predicted amino acid composition of the two mature viral glycoproteins, both were found to have a high cysteine content (G2, 6%; G1, 5%). Sequences within the open reading frame capable of encoding up to 23,000 Da of polypeptide were found in addition to those required for the viral glycoproteins. The potential contribution of these sequences to the coding capacity of the M RNA, viral protein processing, and intracellular protein distribution is discussed.

Solitary spinal metastasis from Wilms' tumor

A 7 year old boy presented with sudden lower extremity paresis six months after resection of a Wilms' tumor. Roentgenologic studies showed destruction of the sixth vertebral body and a thoracic extradural block by an epidural mass subsequently proven to be a solitary Wilms' metastasis.

Comparison of the complement-fixing activity of antinuclear antibodies in lupus nephritis, mixed connective tissue disease, and scleroderma

Complement-fixing antinuclear antibody (CFANA) titers were measured in 18 patients with lupus nephritis and were compared to titers in 22 patients with scleroderma and mixed connective tissue disease (MCTD) who had comparable ANA titers but lacked nephritis. CFANA titers were higher in SLE patients with nephritis than in a control group of SLE patients without nephritis but were no higher than in scleroderma or MCTD. Thus the striking differences in the prevalence of nephritis among these patients with high titer ANA cannot be explained by differences in complement fixation by these antibodies.

Combined titre and fluorescent pattern of IgG antinuclear antibodies using cultured cell monolayers in evaluating connective tissue diseases

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