Overexpression and purification of an immunologically reactive His-BIV capsid fusion protein

First evidence of bovine immunodeficiency virus infection in Mexican cattle

This study set out to identify the presence of bovine immunodeficiency virus (BIV) in animals geographically located in Mexico. BIV was first discovered in the United States in a dairy cow with persistent lymphocytosis, lymphoid hyperplasia and lymphocytic encephalitis. Many studies indicate that BIV infection is globally distributed, but its presence in Mexico remains unknown. We collected 1,168 heparinized blood samples from cattle in ten states across the Mexican Republic, then separated plasma using centrifugation and tested for antibodies against BIV. We used an indirect ELISA based on the use of a synthetic peptide derived from transmembrane glycoprotein (gp45/TM). In order to identify the viral genome, we designed a synthetic gene as a PCR control, as well as a pair of oligonucleotides for amplifying a 519 bp product of the env gene which encodes the surface protein. Positive amplicons were purified and subjected to nucleotide sequencing. A total of 189 (28.94%) tested plasma samples suggest the presence of specific anti-BIV antibodies in all states studied except for Chiapas. Additionally, PCR results identified six positive cows in the states of Puebla and Coahuila. BIV in these cows was confirmed via nucleotide sequencing and in silico analysis of these samples. This is the first report of the presence of BIV in Mexican cattle.

Bovine immunodeficiency virus: a lentiviral infection

The bovine immunodeficiency virus (BIV) is a lentivirus which is known to infect cattle worldwide. Though serological and genomic evidence of BIV in cattle has been found throughout the world, isolation of the virus has been reported only from few places. Very little is known about its impact on animal health status, pathogenesis and mode of transmission. BIV is considered generally non-pathogenic and is not known to cause any serious disease in cattle. BIV is genetically and antigenically related to Jembrana disease virus (JDV), the cause of an acute disease in Bali cattle (Bos javanicus) and human immunodeficiency virus, the cause of acquired immunodeficiency syndrome in human. Therefore, it is important to monitor the presence of BIV in cattle to keep vigil over its possible evolution in its natural host to emerge as pathogenic lentivirus like JDV. Differentiation of BIV infection in cattle from the acutely pathogenic JDV is important for diagnosis of the latter. Currently, BIV is considered as a safe model for understanding the complex genome of lentiviruses. Further research on BIV is indeed needed to elucidate its possible role in animal health as well as for insight into the molecular mechanisms adopted by related lentiviruses.

Construction of a cloning system for the mass production of a virus-binding protein specific for poliovirus type 1

In our previous study, virus-binding proteins (VBPs) demonstrating the ability to strongly bind poliovirus type 1 (PV1) were recovered from a bacterial culture derived from activated sludge. The isolated VBPs would be useful as viral adsorbents for water and wastewater treatments. The VBP gene of activated sludge bacteria was isolated, and the cloning system of the VBP was established. The isolation of the VBP gene from DNA libraries for activated sludge bacteria was achieved with the colony hybridization technique. The sequence of the VBP gene consisted of 807 nucleotides encoding 268 amino acids. Fifteen amino acid sequences were retrieved from 2,137,877 sequences by a homology search using the BLAST server at the National Center for Biotechnology Information. The protein encoded in the isolated genome was considered to be a newly discovered protein from activated sludge culture, because any sequences in protein databases were not perfectly matched with the sequence of the VBP. It was confirmed that Escherichia coli BL21 transformed by pRSET carrying the isolated VBP gene could extensively produce the VBP clones. Enzyme-linked immunosorbent assay (ELISA) revealed that the VBP clone exhibited the binding ability with intact particles of PV1. The equilibrium binding constant between PV1 and VBP in the ELISA well was estimated to be 2.1 x 10(7) (M(-1)), which also indicated that the VBP clones have a high affinity with the PV1 particle. The VBP cloning system developed in this study would make it possible to produce a mass volume of VBPs and to utilize them as a new material of the specific adsorbent in several technologies, including virus removal, concentration, and detection.

Versatile method for production and controlled polymer-immobilization of biologically active recombinant proteins

The immobilization of a protein by covalent attachment to a support matrix should involve only functional groups of the protein that are not essential for its biological activity. A general strategy for obtaining recombinant proteins designed for oriented covalent grafting onto copolymers was investigated. The rationale involves the definition of seven p24-derived recombinant proteins as fused to either distant or adjacent tags comprising primary amine rich tag consisting of six contiguous lysines suitable for oriented covalent immobilization and a hexa-histidine tag suitable for metal chelate affinity purification. High-level expression, efficient affinity purification, and coupling yields onto maleic anhydride-alt-methyl vinyl ether copolymers higher than 95% were obtained for all proteins. Afterwards, an investigation of the biological features of the immobilized vs. nonimmobilized protein onto the copolymer allowed us to select one bioconjugate which was used in a diagnostic context, i.e., as a capture antigen in an ELISA format test. Sera from 107 HIV-seropositive individuals at various stages of HIV infection, including two seroconversion panels and 104 healthy HIV-seronegative controls, were tested using either RH24 or RK24H-copolymer coated onto the microtiter plate. These assays showed that the use of such a protein-copolymer bioconjugate allowed detection of lower antibody titers than the RH24 protein, illustrating the potential of applications of such doubly tagged proteins. Thus, a set of expression vectors was designed containing four different combinations of hexa-lysine and hexa-histidine tags and a multiple cloning site, allowing the production of different recombinant fusion proteins suitable for biological reactivity conservation after immobilization.

Mechanisms leading to an oriented immobilization of recombinant proteins derived from the P24 capsid of HIV-1 onto copolymers

To investigate the mechanism leading to an oriented immobilization of recombinant proteins onto synthetic copolymers, five genetically modified HIV-1 p24 capsid proteins (RH24, RH24A4K2, RH24R6, RH24R4K2, and RH24K6) were tested for their efficiency to covalently bind to maleic anhydride-alt-methyl vinyl ether (MAMVE) and N-vinyl pyrrolidone-alt-maleic anhydride (NVPMA) copolymers. These proteins contain, at their C-termini, tags differing in cationic and/or reactive amino acids density. We demonstrated that an increase of the charge and amine density in the tag enhances the coupling yield, the most efficient tag being a six lysine one. The reactivity of the proteins depends directly on the reactivity of the tag, and this led us to conclude that the tag was the site where the covalent grafting with the polymer occurred. Thus, design of such tags provides a new efficient and versatile method allowing oriented immobilization of recombinant proteins onto copolymers.

Molecular specificities of antibodies against ovine and murine recombinant prion proteins

The prion proteins (PrP) from sheep and mouse were produced in large quantities of full-length protein in Escherichia coli after fusion with a carboxy-terminal hexahistidine sequence. Both recombinant proteins were recognized, at variable levels, in ELISA using a panel of antibodies recognizing different parts of the PrP molecules, from the octo-repeat region (79-92 human sequence), to the C terminal end of the protein. We show that these recombinant proteins enable polyclonal antisera to be produced in PrP0/0 mice, the sheep prion protein being strongly immunogenic, using either native or guanidium hydrochloride-treated recombinant protein. Sera produced against the sheep protein also reacted in Western blot with bovine, ovine, and murine PrP res, but showed higher reactivity with sheep PrP res. Interestingly, when compared to an antiserum produced against bovine 106-121 peptidic sequence (RB1), we found strikingly different ratios of the PrP res glycoforms, in both cattle with BSE and sheep with natural scrapie, but not in scrapie infected mice. Such results further demonstrate that the assessment of PrP res glycoform ratios, using different antibodies, may depend on antibodies species-specificities.

Immunological characterization of the sheep prion protein expressed as fusion proteins in Escherichia coli

The prion protein (PrP) from sheep was produced in large quantities of entire protein in Escherichia coli after fusion with a carboxy-terminal hexahistidine sequence. In contrast, amino-terminal fusion with glutathione S-transferase (GST) revealed a high susceptibility toward cleavage of the protein. Both recombinant proteins were recognised, at variable levels, in Western blots using a panel of antibodies against the 40-56, 89-104, 98-113 and 112-115 sequences of the prion protein, similarly to the abnormal prion protein extracted from scrapie-infected sheep. Interestingly, monoclonal antibody 3F4 was found to react with these three proteins in Western blot.