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P H Lambert

Publications and source records attributed to P H Lambert.

At least 55 records · Page 3Linked to original sources
PubMed1993

Effector functions of circumsporozoite peptide-primed CD4+ T cell clones against Plasmodium yoelii liver stages.

Previously, CD4+ T cell lines and clones were isolated after immunization of BALB/c and C57BL/6 mice with the Py1 peptide, a 21-mer synthetic peptide corresponding to a N-terminal segment of the circumsporozoite protein of Plasmodium yoelii. The clones were separated into the Th1 and Th2 subsets on the basis of lymphokine production. It was observed that immunization with the Py1 peptide induced preferentially Th1 cells in BALB/c and Th2 cells in C57BL/6 mice. These clones were then tested for their cytolytic ability in vitro. Some of the clones from BALB/c and C57BL/6 mice eliminated liver stage parasites from cultured hepatocytes in a MHC restricted manner. Nevertheless, none of these clones was able to lyse Py1 peptide-pulsed target cells. It was also found that two clones could protect BALB/c mice against a sporozoite challenge. These results provide evidence that CD4+ T cells, induced after priming with a defined peptide, could participate in the effector mechanisms against malaria liver stages.

Animals↗
PubMed1993

Characterization of host CD4+ T lymphocytes in mice neonatally tolerized to alloantigens.

BALB/c mice injected at birth with semi-allogeneic F1 spleen cells become tolerant to alloantigens as shown by their CTL unresponsiveness to the corresponding alloantigen and the persistence of donor F1 cells into the BALB/c host. Moreover, these mice develop a transient systemic lupus erythematosis-like autoimmune syndrome characterized by splenomegaly, glomerulonephritis, thrombocytopenia and abnormal serological findings, such as several autoantibodies and IgG1 hypergammaglobulinemia. Recent studies done in our laboratory have shown that donor F1 B cells persisting in the host are responsible for the production of autoantibodies and must be activated in vivo by the host CD4+ T lymphocytes in a MHC class II-restricted fashion. In the present work, we have focused our attention on the ability of splenic CD4+ T cells recovered at different periods from BALB/c mice injected at birth with (CBA/Ca x BALB.Ighb) F1 spleen cells to interact with and activate F1 semi-allogeneic spleen cells in vitro. We show that (i) only CD4+ T cells from 2- and 3-week-old tolerant BALB/c mice preferentially produce IL-4 and IL-5 in response to a F1 semi-allogeneic in vitro stimulation, (ii) CD4+ T cells purified from 3-week-old tolerant BALB/c mice are able to induce in vitro IgG and IgM production by F1 B cells. Taken together, these results strongly suggest that host CD4+ T cells, belonging to the TH2 subset progressively lose their reactivity towards the F1 semi-allogeneic persistent B cells, reaching a state of unresponsiveness that correlates with the disappearance of serum autoantibodies and autoimmune pathology.

Animals↗
PubMed1993

Anti-Ia treatment prevents lupus-like autoimmune syndrome in mice neonatally tolerized to alloantigens.

Neonatal injection of semi-allogeneic F1 spleen cells into newborn parental mice results in induction of tolerance to the corresponding class I alloantigen and chimerism. This state of tolerance is associated with the development of a transient lupus-like autoimmune syndrome. Previous experiments performed in our laboratories have shown that host CD4+ T lymphocytes and donor B cells persist in the host and are essential in triggering the autoimmune syndrome observed in neonatally tolerized mice. In this study, we show that early treatment of tolerized mice with anti-donor MHC class II mAb totally prevents the lupus-like syndrome. Moreover, delayed treatment significantly decreases, but to a lesser extent, autoimmune pathological features in tolerized mice. Taken together, these results show that lupus-like autoimmune syndrome developed by neonatally tolerized mice is efficiently prevented by anti-Ia treatment without interfering with the induction of tolerance.

Animals↗
PubMed1993

Successful primate immunization with peptides conjugated to purified protein derivative or mycobacterial heat shock proteins in the absence of adjuvants.

We have previously shown in mice that antibodies can be induced to synthetic malaria peptides conjugated to mycobacterial antigens, such as purified protein derivative (PPD) or heat shock proteins (hsp), and given in the absence of adjuvants after a previous priming with bacille Calmette-Guérin (BCG). In the present study we investigated this model of immunization in the non-human primates, Saimiri sciureus monkeys. Monkeys primed with BCG subcutaneously and then immunized subcutaneously with the Plasmodium falciparum sporozoite (NANP)40 synthetic peptide conjugated to PPD or mycobacterial hsp of 65 or 70 kD, in the absence of adjuvants, produced antipeptide and anti-sporozoite IgG antibodies. Interestingly, the carrier effect of the hsp of 70 kD for the induction of anti-(NANP)40 antibodies was also observed in the absence of a previous priming with BCG. These data suggest that such a vaccination strategy may be applied to humans.

Adjuvants, Immunologic↗
PubMed1993

Presentation of T-cell epitopes assembled as multiple-antigen peptides to murine and human T lymphocytes.

Multiple-antigen peptide (MAP) constructs containing different T- and B-cell epitopes were assessed for their ability to be specifically recognized by murine and human T-cell clones. The different synthetic MAP constructs consisted of a malaria T-cell epitope or of a human universal tetanus toxin helper T-cell epitope collinearly synthesized with B-cell epitopes from the circumsporozoite proteins of different malaria parasites. All constructs were able to stimulate specifically T-cell clones. Interestingly, T-cell epitopes assembled as MAP constructs did not require processing for the specific stimulation of murine and human T-cell clones, as shown by retention of their stimulatory effect in the presence of glutaraldehyde-fixed antigen-presenting cells. However, processing was required for most of the synthetic constructs containing both T- and B-cell epitopes. Thus, the requirement for processing of these constructs seems to be dictated by the nature of the B-cell epitope present.

Amino Acid Sequence↗
PubMed1992

Mycobacterial heat-shock proteins as carrier molecules. II: The use of the 70-kDa mycobacterial heat-shock protein as carrier for conjugated vaccines can circumvent the need for adjuvants and Bacillus Calmette Guérin priming.

In a recent work, we have shown that mycobacterial heat-shock proteins (hsp) of 65-kDa (GroEL-type) and 70-kDa (DnaK-type) acted as carrier molecules in mice, previously primed with Mycobacterium tuberculosis var. bovis (bacillus Calmette-Guérin, BCG), for the induction of high and long-lasting titers of IgG against the repetitive malaria synthetic peptide (NANP)40. Anti-peptide antibodies were induced when the malaria peptide, conjugated to the mycobacterial hsp, was given in the absence of any adjuvants (Lussow et al., Eur. J. Immunol. 1991. 87:2960). In this report, we show that mice immunized with peptides or oligosaccharides conjugated to the 70-kDa hsp produced high titers of IgG antibodies in the absence of any previous priming with BCG. The anti-peptide antibody response persisted for at least 1 year. This adjuvant-free carrier effect of the 70-kDa hsp was T cell dependent, since no anti-peptide nor anti-70-kDa IgG antibodies were induced in athymic nu/nu mice. Previous immunization of mice with the 65-kDa or 70-kDa hsp did not have any negative effect on the induction of anti-peptide IgG antibodies after immunization with hsp-peptide conjugates in the absence of adjuvants. Furthermore, preimmunization with the 65-kDa hsp could substitute for BCG in providing an effective priming for the induction of anti-(NANP) antibodies. Finally, both the 65-kDa and 70-kDa hsp acted as carrier molecules for the induction of IgG antibodies to group C meningococcal oligosaccharides, in the absence of adjuvants. These findings strongly suggest that the use of hsp as carriers in conjugated constructs for the induction of anti-peptide and anti-oligosaccharide antibodies could be of value in the design of new vaccines for eventual use in humans.

Amino Acid Sequence↗
PubMed1992

Hepatitis B virus, alpha-fetoprotein synthesis, and hepatocellular carcinoma in Zaire.

We investigated the epidemiology of hepatocellular carcinoma (HCC) in Zaire, and evaluated the association between exposure to hepatitis B virus (HBV) and the development of HCC. Two hundred and twenty-three consecutive cases of HCC diagnosed over 19 years (1966-1985) were reviewed. HCC represented 8.32% of all carcinomas and 5.56% of all cancers. Frequency was higher in males (75.7%) than in females (24.3%); a sex ratio of 3/1. The majority (82.1%) of patients were aged 14 to 55 years with a peak occurrence in the fourth decade (28.6%). The mean age in males (41.27 +/- 17.5 years) and females (37.40 +/- 15.16 years) was significantly different (p < 0.02). Sera from 40 patients and 68 age and sex-matched controls were analyzed for markers of HBV infection: patients and controls had comparable rates of exposure (96% vs 72.1%, respectively). However, patients had significantly higher HBsAg carrier rates (56.7% vs 7.35%; p < 0.001), and lower anti-HBsAg seroconversion rates (25% vs 63.2%, p < 0.05). Using immunohistochemical analysis, the livers of patients were evaluated for HBsAg and HBcAg. These HBV antigens were more frequent in non-tumourous hepatocytes (53.3% vs 23.3%, respectively) than in HCC cells (13.3% vs 3.3%). Serum alpha-fetoprotein (AFP) was abnormal (> 20 ng/ml) in 90% of patients. The geometric mean (GM) AFP was 7273.8 ng/ml. AFP levels were significantly higher in HBsAg-positive HCC cases (GM: 19,322.6 ng/ml; 95% confidence interval (CI): [3639.2, 102,565.2]) than in antigen negative cases (GM: 1939.5 ng/ml; 95% CI: [182.8, 19,952.6]), but did not correlate with HBV replication. Immunohistochemical detection of AFP revealed a similar correlation between AFP and HBsAg. Neither AFP level nor HBsAg production correlated with cellular atypia or tumor grade.

Adolescent↗
PubMed1992

Hemolysin-producing Listeria monocytogenes affects the immune response to T-cell-dependent and T-cell-independent antigens.

A murine experimental infection with a hemolysin-producing (Hly+) strain of Listeria monocytogenes and a non-hemolysin-producing (Hly-) mutant was used as an in vivo model to evaluate the role of hemolysin production in the immune response. No antilisterial antibodies were detectable following sublethal infection with Hly+ bacteria, but consistent antilisterial immunoglobulin G (IgG) and IgM antibody production was observed following sublethal infection with the Hly- mutant. Hly+ but not Hly- L. monocytogenes induced transient inhibition of antibody response to Hly- bacteria and to unrelated T-cell-dependent (tetanus toxoid) and T-cell-independent (pneumococcal polysaccharide 3) antigens. Transient inhibition of the activation of an antigen-specific T-cell clone was also observed following Hly+ infection of antigen-presenting cells but not following Hly- infection. These results suggest that hemolysin production by L. monocytogenes is an important factor in modulating the immune response to T-cell-dependent and T-cell-independent antigens in infected individuals.

Animals↗
PubMed1992

Synthesis and ACE inhibitory activity of the stereoisomers of perindopril (S 9490) and perindoprilate (S 9780).

Perindopril, a powerful ACE inhibitor contains 5 chiral carbons, thus there is the possibility of 2(5) = 32 stereoisomers for the general structure 1. These 32 stereoisomers were synthesized by cross-coupling the 8 stereoisomers of perhydroindole 2-carboxylic acid benzylester with the 4 stereoisomers of 2-(1-carbethoxybutylamino) propionic acid 4, then hydrogenating the resulting benzylesters. Each stereoisomer of perindopril furnished by saponification the corresponding diacid stereoisomer 2 of perindoprilate which is the active form of perindopril. For each of the 32 stereoisomers 2 the in vitro ACE inhibitory potency (IC50) was determined. Four of them, including perindoprilate, had activities in the nanomolar range, and four more were ca. 10 x less active. The four acid esters 1 corresponding respectively to the four most active diacids 2 in vitro were studied (1 mg/kg via the oral route) for their in vivo activity in dogs. It could be concluded that p.o. absorption of the active acid esters 1 and their activation to the active diacid 2 depended only on the chiralities of the two ring junction carbons of the perhydroindole ring.

Administration, Oral↗
PubMed1991

Transient T and B cell activation after neonatal induction of tolerance to MHC class II or Mls alloantigens.

The neonatal injection of semiallogeneic F1 spleen cells into newborn parental mice results in the induction of tolerance to the corresponding alloantigen (alloAg) and chimerism. In these F1 cell-injected mice, we have previously observed that this state of specific tolerance is associated with the development of a transient lupus-like autoimmune syndrome. In this study, we show that neonatal injection of mice with spleen cells differing from the host at major histocompatibility complex (MHC) class I, class II, class (I + II), or minor lymphocyte stimulating (Mls) alloAg induced a state of specific tolerance characterized by the absence of alloreactive CTL and/or Th cell responses in the spleen and the thymus of 6- to 12-week-old injected mice. However, in mice rendered tolerant to MHC class II or class (I + II) alloAg, the presence of high levels of IgG1 antibodies, of circulating immune complexes, of anti-ssDNA autoantibodies, and of tissue lesions were transiently observed. In these mice, an increased Ia Ag expression on lymphoid spleen cells was also detected at 1 wk. The elevated production of IgG1 and the overexpression of Ia Ag were almost completely prevented by treatment with an anti-IL-4 mAb. Such manifestations of B cell activation and autoimmunity were not observed in mice neonatally injected with F1 cells differing from the host only at MHC class I Ag. In mice neonatally tolerized to Mls Ag, a transient increase in IgG2a production and an overexpression of Ia Ag were detected without features of autoimmunity, and were prevented by anti-INF-gamma mAb treatment. In mice rendered tolerant to MHC class II, class (I + II), or Mls alloAg at birth, the manifestations of B cell activation were associated with the presence of in vivo-activated alloreactive CD4+ T cells in the spleen--but not the thymus--of 1-wk-old injected mice. Together, these results suggest that in mice neonatally injected with semiallogeneic F1 cells, the process of tolerance induction is not efficient during the early postnatal period, and could allow the maturation and peripheralization of some alloreactive CD4+ T cells, leading to transient B cell activation and, depending on the alloAg, to autoimmunity.

Animals↗
PubMed1991

Lack of H-2 restriction of the Plasmodium falciparum (NANP) sequence as multiple antigen peptide.

The major surface antigen of malaria sporozoites, the circumsporozoite protein, contains a region of tandem amino acid repeats, which in the case of the human malaria parasite Plasmodium falciparum, consist of four amino acids Asn-Ala-Asn-Pro (NANP) repeated up to about 40 times. This repetitive sequence has been considered as the basis for the development of subunit vaccines against P. falciparum malaria. We and others had previously shown that synthetic and recombinant NANP peptides were immunogenic only in H-2b mice. In the present report we show that, when mice with different H-2 haplotypes are immunized with the repetitive NANP sequence incorporated in a synthetic branching multiple antigen peptide (MAP), all except one of the mouse strains tested mounted an anti-peptide antibody response. Such a response does not appear to be due to the peculiar assembly of the NANP sequence. In fact, MAP containing repetitive sequences from circumsporozoite proteins of other malaria parasites did not overcome the genetic restriction of the immune response to the linear peptides. These data show that in the case of the P. falciparum NANP repeats, their immunogenicity can be dramatically changed and increased when these peptides are assembled as MAP. This unexpected finding may be of interest in the design of synthetic candidate malaria vaccines.

Amino Acid Sequence↗
PubMed1991

Mycobacterial heat-shock proteins as carrier molecules.

We have previously shown that the priming of mice with live Mycobacterium tuberculosis var. bovis (Bacillus Calmette-Guérin, BCG) and immunization with the repetitive malaria synthetic peptide (NANP)40 conjugated to purified protein derivative (PPD), led to the induction of high and long-lasting titers of anti-peptide IgG antibodies, overcoming the requirement of adjuvants and the genetic restriction of the antibody response to the peptide (Lussow et al., Proc. Natl. Acad. Sci. USA 1990. 87:2960). This initial work led us to the following observations. BCG had to be live for priming to lead to the induction of anti-peptide antibodies. Surprisingly, priming with other living microorganisms which chronically infect the macrophage (e.g. Salmonella typhimurium and Leishmania major) also induced anti-peptide antibodies in mice immunized with PPD-(NANP)40 conjugate. It was, thus, hypothesized that molecules expressed during active infection and also known to be highly conserved between species, namely the heat-shock proteins (hsp), could mediate the T cell sensitization required for the production of anti-peptide antibodies. In fact, when the PPD protion of the conjugate was replaced by a highly purified recombinant protein corresponding to the 65-kDa (GroEL-type) hsp of M. bovis, this resulted in the production of anti-(NANP) IgG antibodies in BCG-primed mice, irrespective of the major histocompatibility complex-controlled responsiveness to the (NANP) sequence itself. Further, similar induction of anti-peptide antibody response was also obtained with a recombinant 70-kDa (DnaK-type) hsp of M. tuberculosis, but not with a small molecular mass (18 kDa) of M. leprae. Finally, an adjuvant-free carrier effect for anti-peptide IgG antibody production in BCG-primed mice, was also exerted by the GroEL hsp of Escherichia coli. This finding that hsp can act as carrier molecules without requiring conventional adjuvants is of potential importance in the development of vaccine strategies.

Adjuvants, Immunologic↗
PubMed1991

Characterization of murine monoclonal antibodies against a repetitive synthetic peptide from the circumsporozoite protein of the human malaria parasite, Plasmodium falciparum.

Monoclonal antibodies (mAbs) were raised in mice against the synthetic peptide (NANP)40, consisting of 40 (NANP) repeats of the circumsporozoite (CS) protein of the human malaria parasite, Plasmodium falciparum, and characterized. (i) Five of these mAbs recognized the P. falciparum CS protein in western blot experiments and in immunofluorescence assays using different preparations of sporozoites. The remaining two mAbs (CT3.2 and CT3.3, both IgG1) gave negative results by both techniques. (ii) When the anti-(NANP)40 peptide mAbs were functionally tested in vitro to assess their ability to inhibit the attachment and penetration of the parasites into cultured human liver cells, six of them exhibited inhibitory activities ranging between 66 and 90%. CT3.2 mAbs, also, inhibited sporozoite attachment and penetration, despite the negative results by immunofluorescence and western blot experiments. However, when immunofluorescence was repeated in the presence of calcium, CT3.2 did reveal a positive recognition of P. falciparum sporozoites, suggesting that this mAb could recognize the (NANP) sequence when calcium was bound to the repetitive peptide. (iii) Furthermore, the binding of an anti-(NANP)40 IgM mAb (CT1) to the solid-phase peptide was not inhibited by preincubation of the peptide with a mAb against the P. falciparum CS protein. (iv) Finally, one anti-(NANP)40 IgG1 mAb (CT3.1) was unable to bind to the shorter (NANP)3 peptide, although it recognized the (NANP)40 peptide and the P. falciparum CS protein. The results presented here suggest that heterogeneous antibody populations are produced upon immunization of mice with (NANP)40 synthetic peptide and that epitopes different from those simply related to the linear (NANP) amino acid sequence are likely to be present in long (NANP)n constructs as well as in the repetitive domain of the P. falciparum CS protein.

Amino Acid Sequence↗