CD46 transgene expression in pig peripheral blood mononuclear cells does not alter their susceptibility to measles virus or their capacity to downregulate endogenous and transgenic CD46

Codon optimized membrane cofactor protein expression in α 1, 3 galactosyltransferase knockout pig cells improve protection against cytotoxicity of monkey serum

In this study, we attempted to upgrade GT ^-MCP/-MCP pig genetically to express MCP at a higher level and additionally thrombomodulin (TBM), which have respective roles as a complement regulatory protein and a coagulation inhibitor. We constructed a dicistronic cassette consisting of codon-optimized MCP (mMCP) and TBM (m-pI2), designed for ubiquitous expression of MCP and endothelium specific expression of TBM. The cassette was confirmed to allow extremely increased MCP expression compared with non-modified MCP, and an endothelial-specific TBM expression. We thus transfected m-pI2 into ear-skin fibroblasts isolated from a GT ^-MCP/-MCP pig. By twice selection using magnetically activated cell sorting (MACS), and single-cell culture, we were able to obtain clones over 90% expressing MCP. The cells of a clone were provided as a donor for nuclear transfer resulting in the generation of a GT ^-MCP/-MCP /mMCP/TBM pig, which was confirmed to be carrying cells expressing MCP and functioning as an inhibitor against the cytotoxic effect of normal monkey serum, comparable with donor cells. Collectively, these results demonstrated an effective approach for upgrading transgenic pig, and we assumed that upgraded pig would increase graft survival.

Expression of human CD46 has no effect on porcine circovirus type 2 infection and shedding in the experimental pig model

Xenotransplantation of tissues from transgenic pigs with desired genetic modifications such as CD46 expression help minimize xenograft rejections. However, CD46 is a known receptor for some viruses. In this study, pigs transgenic for human CD46 (CD46-TG) and appropriate non-transgenic (non-TG) control pigs were utilized to determine possible differences in the level of replication and shedding of porcine circovirus type 2 (PCV2). Non-TG and CD46-TG were blocked by transgenic status and randomly divided into three groups: Non-TG negative controls (n = 3), non-TG-PCV2 (n = 10; PCV2a = 5, PCV2b = 5), and CD46-TG-PCV2 (n = 6; PCV2a = 3, PCV2b = 3). Blood, oral, nasal and fecal swabs were collected at regular intervals from the day of arrival until 70 days post inoculation (DPI). All samples were tested by quantitative real-time PCR for the presence of PCV2 DNA and serum was tested for presence of PCV2 antibodies by ELISA. Overall, the main effects "transgenic status" and "PCV2 subtype" had no influence on degree of PCV2 viremia and shedding or the anti-PCV2 humoral immune response in CD46-TG-PCV2 pigs compared to non-TG-PCV2 pigs. Differences in PCV2 concentrations between non-TG-PCV2 and CD46-TG-PCV2 pigs were minimal and limited to DPI 35 in sera, DPI 7 in fecal swabs and DPI 5 in nasal swabs when CD46-TG-PCV2 pigs had significantly higher concentrations of PCV2 DNA. At DPI 1, CD46-TG-PCV2 pigs had significantly lower concentrations of PCV2 DNA in oral swabs. Under the study conditions, the presence of human CD46 in transgenic pigs had no effect on PCV2 infection in otherwise healthy pigs capable of a normal immune response.

Nuclear remodeling and nuclear reprogramming for making transgenic pigs by nuclear transfer

A better understanding of the cellular and molecular events that occur when a nucleus is transferred to the cytoplasm of an oocyte will permit the development of improved procedures for performing nuclear transfer and cloning. In some cases it appears that the gene(s) are reprogrammed, while in other cases there appears to be little effect on gene expression. Not only does the pattern of gene expression need to be reprogrammed, but other structures within the nucleus also need to be remodeled. While nuclear transfer works and transgenic and knockout animals can be created, it still is an inefficient process. However, even with the current low efficiencies this technique has proved very valuable for the production of animals that might be useful for tissue or organ transplantation to humans.

Is mRNA and protein level of CD46 altered in measles virus vaccine strain S191-infected cells?

Previous research showed that the expression of measles virus receptor CD46 was downregulated after expression of measles virus hemagglutinin protein on the surface of the virus infected cell or triggered by infected cell-to-cell contact. We reported here that the mRNA level of CD46 in MV infected cells was not changed which was tested by real-time quantitative PCR. To further analyse the surface expression alteration of CD46 after MV infection, flow cytometric analysis and indirect immunofluorescence were used to detect the protein level of CD46. Altogether, our results provided a demonstration that the expression of CD46 was not downregulated by the infection of MV strain S191 both on mRNA level and cellular surface protein level. Previous results reported that the "downregulation" of CD46 expression on the cell surface may take place because H protein masks the antibody recognition site on CD46 which results in "downregulation" of the expression of CD46.

Production and characterization of a pig line transgenic for human membrane cofactor protein

A pig line transgenic for human membrane cofactor protein (hMCP) has been established. Offspring from the founder were produced by crossing the founder with pigs heterozygous for the human decay accelerating factor (hDAF) transgene. As a result, pigs transgenic for both hMCP and hDAF have been produced. Ribonuclease protection assay (RPA) indicated that hMCP was expressed in all the tissues analysed. In addition, immunohistochemical results indicated a high level of expression of hMCP on neural tissues and islets where hDAF was absent or weakly expressed. C3 fragment deposition and cytotoxicity assays indicated that hMCP expression alone on pig endothelial cells and peripheral blood lymphocytes (PBLs) provided protection against human complement mediated damage. However, we did not find that porcine endothelial cells expressing both hDAF and hMCP were better protected than those expressing hDAF alone. The expression of hMCP on tissues where hDAF is not expressed could provide these tissues with protection against human complement mediated lysis.

CD150 (SLAM) is a receptor for measles virus but is not involved in viral contact-mediated proliferation inhibition

Measles virus (MV) interacts with cellular receptors on the surface of peripheral blood lymphocytes (PBL) which mediate virus binding and uptake. Simultaneously, the direct contact of the viral glycoproteins with the cell surface induces a negative signal blocking progression to the S phase of the cell cycle, resulting in a pronounced proliferation inhibition. We selected a monoclonal antibody (MAb 5C6) directed to the surface of highly MV-susceptible B cells (B95a), which inhibits binding to and infection of cells with MV wild-type and vaccine strains. By screening a retroviral cDNA library from human splenocytes (ViraPort; Stratagene) with this antibody, we cloned and identified the recognized molecule as signaling lymphocytic activation molecule (SLAM; CD150), which is identical to the MV receptor recently found by H. Tatsuo et al. (Nature 406:893-897, 2000). After infection of cells, and after surface contact with MV envelope proteins, SLAM is downregulated from the cell surface of activated PBL and cell lines. Although anti-SLAM and/or anti-CD46 antibodies block virus binding, they do not interfere with the contact-mediated proliferation inhibition. In addition, the cell-type-specific expression of SLAM does not correlate with the sensitivity of cells for proliferation inhibition. The data indicate that proliferation inhibition induced by MV contact is independent of the presence or absence of the virus-binding receptors SLAM and CD46.