Expression of complement regulatory protein on porcine endogenous retrovirus (PERV) depends on molecular size.

Expression of complement regulatory proteins (CRP) on pig cells is an effective means to avoid hyperacute rejection. However, pig endogenous retrovirus (PERV) from pig cells transfected with CRP may acquire resistance to human serum (HS). The present study investigated the size limitations of the transfected CRP that can be easily expressed and function on PERV particles. cDNAs of various sized DAF(CD55)s, including single-, double-, triple-, tetra-, as well as 2.1- and 2.2-DAF, were prepared. Pig endothelial cells (PEC) were transduced with the LacZ gene, and were then infected with PERV-B to produce PEC(Z)/PB. The extent of complement-mediated lysis by the transfectant molecules on PEC(Z)/PB was then determined. HEK293 cells were incubated with PEC(Z)/PB culture supernatants in the presence of HS and the LacZ pseudo-type assay was then carried out. Amelioration of complement-mediated lysis by the hybrid molecules was verified in each PEC(Z)/PB clone. All molecules appeared to effectively protect xenogeneic cells against complement-mediated lysis. While PERVs from the PEC(Z)/PB with both the single-DAF and double-DAF were resistant to HS, PERVs from the triple-DAF and tetra-DAF showed no significant increase in resistance. In addition, the PERVs from PEC(Z)/PB with 2.1-DAF and 2.2-DAF were less resistant than PEC with double-DAF. Resistance to HS was steadily attenuated with increasing size of the DAF molecule. The resistance to HS was disappeared by the anti-DAF blocking mAb, indicating that PERVs from the transfectants express DAF molecules on the surface of the PERV. The data clearly indicate that, to avoid the induction of resistance to HS in PERV particles, relatively large CRPs, such as triple-DAF and tetra-DAF or DAF with other large molecules, should be employed in the production of transgenic pigs.

Analysis of the serine protease function of porcine factor I produced by liver cells for xenotransplantation.

The use of a bioartificial liver with pig liver cells in the treatment of fulminant hepatic failure has already begun as a clinical trial in several countries. Therefore, studies on plasma complement regulatory proteins of the pig are necessary, because the liver produces them. Complement factor I is a serine protease that cleaves C3b and C4b. The DNA sequences of factor I have been reported in many species, with the noted exception of pigs. In this study, porcine factor I was cloned and an open reading frame of 1794 base pairs were identified. The predicted amino acid sequence maintained a relatively high homology compared to those of other mammals, especially in the serine protease (SP) region. The cell membrane-bound forms of the porcine and the human SP domain of factor I were constructed. Amelioration of complement-mediated cell lysis by these molecules was then tested, using several kinds of sera and Chinese hamster ovary (CHO) cell transfectants. Both molecules had a suppressing effect on pig, human and dog complements, indicating little species-specificity. Further studies of other plasma complement regulatory proteins produced from pig liver cells will need to be considered as the primary feature of the pig bioartificial liver.

Studies of monkey complement: measurement of cynomolgus monkey CH50, ACH50, C4, C2 and C3.

BACKGROUND: The cynomolgus monkey is commonly used as the recipient in transplantation experiments. However, study of the complement system of cynomolgus monkeys is lacking. In the present study, the complement system of cynomolgus monkeys was compared with that of humans, by checking hemolytic titers. METHODS: Hemolytic titers of complement from cynomolgus monkeys were calculated using the same methods as are used in humans. The complement regulatory function of human decay accelerating factor (DAF, CD55) in cynomolgus monkey serum was next studied using erythrocytes from human DAF-transgenic pigs. RESULTS: The results indicated relatively high values, except for C4: CH50: 211.19 +/- 42.78 units/ml, ACH50: 51.47 +/- 12.43 units/ml, C4: 30 170 +/- 14 300 SFU/ml C2: 33831 +/- 7442 SFU/ml and C3: 93612 +/- 30131 SFU/ml. Western blot experiments using antibodies for human complement components revealed similarities between the cynomolgus monkey and human complement systems. Human DAF inhibited pig erythrocyte lysis from approximately 60-70% to 17% in both human and cynomolgus monkey sera, indicating an almost identical complement regulatory function. CONCLUSION: The hemolytic titer of cynomolgus monkeys was greater than the titer measured in human serum. However, human DAF showed nearly the same complement regulatory function in both human and cynomolgus monkey sera.

Features of a newly cloned pig C1 esterase inhibitor.

The pig cDNA encoding C1 esterase inhibitor (C1-INH) was isolated and the homology of the sequence was compared with that from other animals. The structure of pig C1-INH contains a two disulfide bridge pattern identical to the human C1-INH. In the amino acid sequence of the first Cys-91 to the C-terminal end, the pigC1-INH has a 76.2% homology with the human protein, and the sequence of the reactive site is close to the human. A surface-bound form of pig and human C1-INH, pC1-INH-PI and hC1-INH, respectively, were next constructed. Stable Chinese hamster ovarian tumor (CHO) cell lines and pig endothelial cell (PEC) lines expressing these C1-INH-PI were prepared by transfection. The basic function and the species specificity of pCI-INH were then investigated using these transfectants. pC1-INH and hC1-INH have almost the same suppressive effect on pig, human, dog and rabbit sera in complement-dependent cell lysis, indicating little species specificity.

Effect of tandem forms of DAF(CD55) on complement-mediated xenogeneic cell lysis.

BACKGROUND: It is difficult to produce a transgenic animal with high expression of decay-accelerating factor (CD55: DAF) or other molecules. The purpose of this study was to assess the effect of tandem forms of DAF on a xenogeneic cell membrane against human complement. METHODS: cDNAs of the delta-Short Consensus Repeat (SCR) 1-DAF, the double-DAF, the triple-DAF, and the tetra-DAF with a FLAG-tag were established. Chinese hamster ovary (CHO) cell lines and a pig endothelial cell (PEC) line expressing these molecules were established. The amelioration of complement-mediated lysis by the transfectant molecules on these cells was examined. The CHO cell transfectants were also incubated with normal human serum, and the amount of C3 deposited was determined by FACS analysis. RESULTS: Stable CHO cells and PEC transfectants, in which each molecule was clearly expressed, and Western blots showed that each band corresponded to the expected molecular weight. The extent of amelioration of complement-mediated lysis by these four molecules was then examined. A clear tendency was found, as follows: The higher the tandem number of DAF, the greater was the effect on cytotoxicity. Additional experiments focusing on triple-DAF and tetra-DAF did not indicate any significant difference in complement-mediated lysis. Consistent with the complement-regulatory ability, the inhibitory effect of the deposition of C3 fragments by these molecules was closely related to the degree of amelioration. CONCLUSION: These data indicate that tandem DAF, especially a triple-DAF, is a very effective form for protecting against complement activation.

Premature sister chromatid separation in HIV-1-infected peripheral blood lymphocytes.

To investigate the mechanism of aneuploidy that is frequently observed in AIDS, we examined premature sister chromatid separation (PCS), a sign of genomic instability, in peripheral blood cells of HIV-1-infected individuals. PCS was found in all six HIV-1 individuals at a high incidence. When peripheral blood cells from healthy volunteers were infected with HIV-1 in vitro, the incidence of PCS increased. This suggests that HIV-1 infection causes PCS and has the potential to induce aneuploidy.

Mycobacterium peregrinum infection in a patient with AIDS.

The patient, a 30-year-old housewife, visited a nearby doctor in mid August 2002 because of weight loss and neck swelling. HIV tests done at the hospital were positive. She was referred to and admitted to our hospital on October 2 for detailed examination and treatment of the neck tumor. A coat of epithelial debris extended from the oral cavity to the pharynx and an abscess and a fistula were found in the left tonsil. After hospitalization, an abscess culture revealed the presence of acid-fast bacteria, which was identified as Mycobacterium peregrinum. Treatment with imipenem and clarithromycin resulted in the normalization of CRP (0.1 mg/dl), on day 5 of treatment. The patient was discharged from the hospital after treatment for 2 weeks with imipenem and clarithromycin. Thereafter, the patient received continuous treatment with faropenem and clarithromycin for 4 more weeks, and has shown no signs of recurrence for 11 months to date. Only a few cases of infection with this bacterial strain have been reported. This infection is difficult to treat because most antituberculosis agents are not effective against it and there is limited availability of effective antibiotics. Medical treatment of infection caused by Mycobacterium peregrinum may be useful in such cases.