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C Bona

Publications and source records attributed to C Bona.

At least 37 records · Page 2Linked to original sources
PubMed1998

Protective cellular immunity against influenza virus induced by plasmid inoculation of newborn mice.

Neonate organisms display an intrinsic disability to mount effective immune responses to infectious agents or conventional vaccines. Whereas low doses of antigens trigger a suboptimal response, higher doses are frequently associated with tolerance induction. We investigated the ability of a plasmid-expressing nucleoprotein of influenza virus to prime a specific cellular immune response when administered to newborn mice. We found that persistent exposure to antigen following plasmid inoculation of neonates leads to a vigorous priming of specific CTLs rather than tolerance induction. The CTLs were cross-reactive against multiple strains of type A influenza viruses and produced IFNgamma but no IL-4. The immunity triggered by plasmid inoculation of neonates was protective in terms of pulmonary virus clearance as well as survival rate following lethal challenge with influenza virus. Whereas the persistence of the plasmid at the site of injection was readily demonstrable in adult mice at 3 months after inoculation, mice immunized as newborns displayed no plasmid at 3 months and very little at 1 month after injection. Thus, DNA-based immunization of neonates may prove an effective and safe vaccination strategy for induction of cellular immunity against microbes that cause serious infectious diseases in the early period of life.

Animals↗
PubMed1997

Immune response of neonates elicited by somatic transgene vaccination with naked DNA.

Neonates display lower immune responsiveness and higher susceptibility for high-dose tolerance. Quantitative as well as functional differences between the neonatal and adult lymphocytes or antigen presenting cells (APC) respectively, explain the particular immune responsiveness during the early stages of the postnatal development. Reduced numbers of lymphocytes and APCs as well as a modified responsiveness of T cells in neonates, are the main factors that account for the low threshold of tolerance in newborns. Taking into account these particularities, the design of effective vaccines for neonates poses significant difficulties. We hypothesized that a continuous exposure to low doses of antigens may avoid high-zone tolerance and may lead instead, to effective expansion of effector and memory cells. Indeed, inoculation of newborn mice with plasmids encoding nucleoprotein (NP) or hemagglutinin (HA) of influenza virus, led to the priming of specific cytotoxic (CTL), helper (Th) and B cells, rather than induction of unresponsiveness. Mice immunized as neonates with naked DNA and challenged later with lethal doses of influenza virus, displayed significant protection. Thus, DNA immunization may be a promising strategy for vaccination against serious infectious diseases of infants and children.

Adult↗
PubMed1997

Conditions that induce tolerance in mature CD4+ T cells.

Establishment of antigen-specific tolerance among mature T cells has been a long debated, yet poorly understood issue. In this study we have used transgenic mice bearing a class II--restricted TCR specific for the hemmagglutinin of the influenza virus in order to test the behavior of CD4+ T cells upon exposure to antigen in different forms and doses. We first studied the fate of T cells expressing the transgenic TCR (6.5) in double transgenic mice where HA was expressed as a self antigen by hemapoietic cells. In these mice, we found some mature T cells in periphery that had escaped thymic deletion and that showed signs of activation but which were anergic. Mature CD4+6.5+ cells that were transferred into antigen-containing recipients went through an initial phase of expansion after which most cells were deleted and those remaining became unresponsive, as previously described for CD8+ cells. Inducing tolerance in CD4+6.5+ cells in situ in single transgenic mice proved a difficult task: classical protocols using single doses of soluble or deaggregated antigen as well as feeding antigen all failed to induce antigen-specific unresponsiveness. It was only after decreasing cell numbers by CD4 antibody treatment and by repeatedly reintroducing antigen thereafter that unresponsiveness of 6.5+ cells was achieved and maintained. In no case could we observe the appearance of antigen-specific T cells with a Th2 cytokine profile among the remaining cells and therefore conclude that deletion and anergy represent the major mechanisms of tolerance in our studies.

Adoptive Transfer↗
PubMed1997

Induction of humoral and cellular immunity against influenza virus by immunization of newborn mice with a plasmid bearing a hemagglutinin gene.

Neonates and infants display an intrinsic disability to mount protective immune responses to influenza viruses or conventional influenza vaccines. We investigated the ability of naked DNA to prime protective immune responses by inoculating newborn and adult mice with a plasmid (pHA) expressing hemagglutinin (HA) from the neurovirulent strain A/WSN/33 of influenza virus. Continuous exposure to small doses of antigen subsequent to neonatal DNA immunization led to effective priming of specific B and Th cells, rather than tolerance induction. The pHA immunization of adult mice primed a strongly biased Th1 response, whereas in neonates it induced a mixed Th1/Th2 response. In contrast to the effect of live-virus immunization, DNA immunization of neonates was followed by enhanced cytotoxic T lymphocyte responses subsequent to challenge with A/WSN/33 influenza virus. Mice immunized as neonates or adults with pHA plasmid exhibited significant increases in survival and decreases in virus lung titers following lethal challenge with the A/WSN/33 virus or the A/PR8/34 drift variant. Our results demonstrate that DNA vaccination is an efficient and safe means to generate broad humoral and cellular immune responses to influenza viruses, during the earliest stages of postnatal life.

Aging↗
PubMed1996

Kinetics of generation and persistence on membrane class II molecules of a viral peptide expressed on foreign and self proteins.

We had previously shown that a genetically engineered Ig expressing an immunodominant CD4+ T epitope corresponding to the 110-120 amino acids of influenza virus hemagglutinin (HA), activated T cells more efficiently than the synthetic peptide. Taking advantage of a T cell hybridoma specific for HA 110-120 and transfected with a reporter gene under the IL-2 promoter, we studied the kinetics of generation and persistence on surface MHC-II of the HA 110-120 peptide derived from various carriers. Our results show that the generation rate of immunogenic MHC II-peptide complex is dependent on the nature of the carrier. Abs specific for HA 110-120 peptide or for other epitopes on HA affect through various mechanisms the presentation of HA 110-120 peptide to T cells. The persistence of immunogenic MHC II-peptide complex on the surface of APC is not dependent on the nature of the carrier and correlates with the half-life of class II molecules, suggesting an irreversible binding of peptides to MHC-II molecules in 2PK3 murine B lymphoma cells.

Animals↗
PubMed1996

Silicone does not potentiate development of the scleroderma-like syndrome in tight skin (TSK/+) mice.

Several reports have implicated an association between the development of connective tissue disorders and exposure to silicone in breast implant patients. These connective tissue disorders include local or systemic scleroderma-like syndrome and have been characterized by fibrosis as well as the presence of circulating autoantibodies. Whether silicone does potentiate the development of a scleroderma-like syndrome is still to be defined. The purpose of the present study was to determine the effect of silicone on the tight skin (TSK/+) mouse which develops a scleroderma-like syndrome and on its normal pa/pa TSK/- littermate. Groups of six TSK and five of their normal pa/pa littermates were injected subcutaneously with low molecular weight silicone (LMW-PDMS), high molecular weight silicone gel (HMW-PDMS), incomplete Freunds' adjuvant (IFA) or Hank's balanced salt solution (HBSS) in the dorsal neck area and ventrally in the upper chest region. Serum was obtained prior to and 1 month after injection of silicone, IFA, or control HBSS. Antibody levels to bovine serum albumin (BSA), RNA polymerase (RNAP) and topoisomerase I were determined. Mice were then euthanized and strips of skin from the injection sites as well as samples of kidney and liver were studied histologically. No significant pathological changes were observed in TSK/- mice 1 month following injection with HBSS, LMW-PDMS or HMW-PDMS. Skin samples from TSK/+ mice which received LMW-PDMS showed hyperplasia of the dermis and peri-panniculus carnosus tissue and infiltrates of macrophages containing lipid-like vacuolated materials. Lipid vacuoles were observed throughout the deeper dermis as multiple loculated vacuoles. TSK mice which received HMW-PDMS showed similar thickening of the dermis and the peri-panniculus carnosus connective tissue. There were no significant differences in the histologic characteristics of the silicone-injected TSK/+ mice compared to those that received HBSS or IFA. No detectable changes in the kidney, spleen, or liver samples taken from TSK/+ or TSK/- mice injected with HBSS, IFA or silicone (LMW-PDMS, HMW-PDMS) preparations were noted. Baseline circulating antibody levels to BSA, RNAP and topoisomerase were significantly higher in TSK/+ mice compared to the control TSK/- littermates. Administration of silicone (LMW-PDMS or HMW-PDMS) did not significantly alter circulating antibody levels to BSA, RNAP and topoisomerase in either the TSK/+ or the TSK/- mice. The results of this study indicate that silicone administration does not potentiate the development of the scleroderma-syndrome characterized by skin lesions and presence of circulating antibodies in the TSK/+ model.

Animals↗
PubMed1996

Development of scleroderma-like syndrome in Tsk/+ mice is not enhanced by silicone administration.

The possible role of silicone in the pathogenesis of a scleroderma-like syndrome is still unresolved. It has been proposed that silicone escaping from breast implants potentiates the progression of the disease. To clarify whether silicone enhances development of fibrotic skin lesions and autoantibodies, we tested its effect on tight skin (TSK/+) mice. TSK/+ mice spontaneously develop skin fibrosis and characteristic autoantibodies which resemble human scleroderma. The results of the present study indicate that silicone administration does not enhance development of skin fibrosis nor synthesis of autoantibodies to RNA polymerase and topoisomerase in TSK/+ mice.

Animals↗
PubMed1996

DNA immunization of newborn mice with a plasmid-expressing nucleoprotein of influenza virus.

Lower responsiveness and higher susceptibility to tolerance are the two main characteristics of neonatal immunity that limit the efficacy of conventional vaccines administered during this period. Based on the fact that DNA immunization of adult organisms is able to generate protective immune responses, we investigated the ability of a plasmid-(NPV1) encoding nucleoprotein (NP) of A/PR8/34 strain of influenza virus to generate a cellular immune response following intramuscular delivery in neonates. Newborn mice immunized with NPV1 plasmid developed significant cytotoxic immunity, comparable to the immune response displayed by adult mice injected with the same dose of plasmid. Furthermore, mice infected with influenza virus 1 month after completion of immunization showed a significant decrease of virus lung titer between day 3 and 7 after challenge, consistent with the protectivity conferred by specific cytotoxic immunity. Thus, mice immunized as neonates with NPV1 plasmid developed a protective cellular immune response, like the adult mice. Therefore, the strategy of DNA immunization may be considered for the purpose of human vaccination to prevent horizontally and vertically transmitted life-threatening infections in infants or children.

Animals↗
PubMed1995

Contribution of the V lambda light chain to the development of the primary antibody repertoire.

The experiments outlined here provide evidence that most VH gene families are expressed in association with either of three V lambda genes available in kappa-deficient mice, though their expression is nonrandom. An exclusive use of V lambda L-chain genes, where predominantly expressed V lambda 1 and V lambda 2 differ by only seven amino acid substitutions in the germline, results in a higher degree of self-reactive antibodies to conserved natural antigens like albumin, thyroglobulin, and stress proteins. The higher levels of self-reactive antibodies, characteristic of preimmune B-cell repertoire, are likely to be a product of nonrandom VH gene family expression and their restricted pairing with three V lambda L-chain genes. These data suggest that a low lambda L-chain expression in normal mice is due, in part, to endogenous selection against lambda L chain in order to restrict self reactivity within the homeostatic threshold.

Animals↗
PubMed1995

Phosphorylation of human plasminogen activators and plasminogen.

Plasminogen (PG), urokinase-type plasminogen activator (u-PA) and tissue-type PA (t-PA) are the main molecules involved in fibrinolysis and in many other physiological and pathological processes. In the present study we report that human t-PA, purified from human melanoma cells, and PG, purified from human plasma, both contain P-Tyr residues, as revealed by immunoblotting analyses with monoclonal anti-P-Tyr antibodies. In addition HPLC amino acid analysis of acid-hydrolyzed t-PA, PG and u-PA, shows that: (i) P-Ser and P-Tyr residues are present in t-PA; (ii) P-Thr and P-Tyr are present in PG; (iii) P-Ser, P-Thr and P-Tyr are present in u-PA. The utilization of monoclonal anti-P-Ser and anti-P-Thr antibodies in immunoblotting experiments has confirmed these data which indicate that phosphorylation is a common feature of PAs and of PG.

Antibodies, Monoclonal↗
PubMed1995

Purification of antigenized immunoglobulins derivatized with monomethoxypolyethylene glycol.

Genetically engineered immunoglobulins (Igs) carrying viral B or T cell peptides in the CDR3 loop, function as efficient delivery system of the defined viral epitopes. Two of these antigenized Igs (AIgs) were derivatized with 2-O-monomethoxypolyethylene glycol-4,6-dichloro-s-triazine (mPEG). Herein, we describe a two-step strategy to purify mPEG-derivatized AIgs (AIgs-mPEG). Unreacted mPEG polymers were removed by size-exclusion chromatography using ammonium hydrogencarbonate as a buffer system. Mildly PEGylated AIgs were isolated from free and highly derivatized AIgs by anion-exchange chromatography. Electrophoretic analysis indicated that the AIgs-mPEG preparation contained less than 4 x 10(-4) M unreacted mPEG. This strategy may be applied to other mPEG-derivatized monoclonal antibodies.

Animals↗
PubMed1995

Presentation by a major histocompatibility complex class I molecule of nucleoprotein peptide expressed in two different genes of an influenza virus transfectant.

Major histocompatibility (MHC) class I glycoproteins are specialized to present to CD8+ T cells, peptides that originate from proteins synthesized within the cytoplasm. Conventional killed vaccines are unable to get into the cell cytoplasm and therefore fail to expand the CD8+ T cell population. We have created a novel influenza transfectant virus, R10, which carries an immunogenic peptide from the nucleoprotein (NP) of PR8 influenza virus in its hemagglutinin (HA) and another similar peptide in its HK influenza virus NP. The two peptides are both presented by H-2Db and bind with approximately equal affinity. They can compete with one another for binding to H-2Db. Yet in cells infected with R10, both peptides are presented efficiently enough to expand the respective cytotoxic T lymphocyte (CTL) precursors in vivo and to serve as targets for CTL lysis in vitro. It has been proposed that proteins bearing signal sequences may be processed by a transporter-independent pathway. To investigate this, we infected the transporter-deficient cell line RMA-S with the R10 virus to see if the NP peptide expressed by the HA would be presented. The result shows that even the presence of a signal peptide in the HA does not overcome the lack of a transporter function, suggesting that the presentation of both peptides is dependent on functional transporter proteins. Our data also suggest the feasibility of creating by genetic engineering, recombinant vaccines expressing multiple epitopes that can effectively stimulate a cellular immune response.

Amino Acid Sequence↗
PubMed1995

Antibody response against poly (Glu60Ala30Tyr10) terpolymer and bacterial levan in kappa-deficient mice.

In murine species, the kappa (+)-bearing immunoglobulins dominate the antibody (Ab) repertoire with a kappa/lambda ratio of 95:5. The aim of the present study is to investigate the characteristics of the antibody response in kappa-deficient (K-/-) mice immunized with a T-dependent synthetic antigen, poly(Glu60Ala30Tyr10) (GAT) and a T-independent antigen, bacterial levan (BL). K-/- mice were obtained by targeted deletion of the J kappa C kappa gene segments. In response to GAT, K-/- mice respond by producing increasing amounts of anti-GAT Ig lambda 1 and Ig lambda 2 in the primary as well as secondary response, although anti-GAT specific monoclonal antibodies (mAb) raised in K-/- mice are mostly of IgM isotype. The GAT public idiotype, GATIdX, present on all GAT-specific Ab bearing kappa light chain, is not detected in the sera of K-/- mice or on any of the anti-GAT lambda 1 mAb. In response to BL, the amount of Ig lambda 1+ Ab in K-/- mice is comparable to the amount of Ig kappa + Ab in normal mice. However, lambda 2+ Ab are detected neither in wild-type nor in K-/- mice. Like kappa + Ab, the majority of lambda 1+ mAb are specific for beta 2-6 fructosan present in BL and rye levan and, to some extent, express the BL-specific idiotype, A48ld. Our results show that important compensatory mechanisms occur in kappa-deficient mice, restoring their ability to mount immune responses against a variety of T-dependent and T-independent antigens by the alternative usage of the clonally restricted lambda repertoire.

Animals↗
PubMed1995

Skewed VH and V kappa gene family expression and pairing occurs among B lymphocytes in autoimmune motheaten mice.

Motheaten mice homozygous for the recessive mev mutation develop a fatal immunodeficiency syndrome associated with hypergammaglobulinemia, thymic aplasia, production of autoantibodies and development of a severe lupus like systemic autoimmune disease. Most B lymphocytes in this mutant strain belong to B-1 subset. We have addressed the question if differences existed in the V-gene repertoire of autoimmune mev/mev mice as compared to phenotypically normal mev/+ and C57BL/6 background strain by examining the VH and V kappa gene family expression as well as the association of VH and V kappa gene families among B lymphocyte clones. The data outlined here demonstrate that both the expression of VH and V kappa gene families and their association is skewed in mev/mev mice, suffering from systemic autoimmune disease, and differs significantly from phenotypically normal mev/+ litter mates as well as the C57BL/6 background strain. In addition, VH+V kappa gene family pairs in phenotypically normal mev/+ differed from normal C57BL/6 mice suggesting that motheaten mutation, whether homozygous or heterozygous, alters the development of the B lymphocyte repertoire. These observations suggest positive selection of B-1 lymphocytes in autoimmune motheaten mice either as a result of selective processes, via receptor-ligand interactions, operating on the development of the primary antibody repertoire or defective B lymphocyte haematopoiesis due to the deficiency of haematopoietic cell phosphatase involved in determining the threshold by which B cells respond to self antigen(s).

Adjuvants, Immunologic↗