Search PubMed⌕ Search

Biomedical subjects

P Perlmann

Publications and source records attributed to P Perlmann.

At least 55 records · Page 3Linked to original sources
PubMed1995

Cellular mechanisms in the immune response to malaria in Plasmodium vinckei-infected mice.

Infection of mice with the malaria parasite Plasmodium vinckei vinckei is 100% lethal. However, after two infections followed by drug cure, BALB/c mice develop a solid immunity which is antibody independent but mediated by CD4+ T cells. To elucidate the mechanisms of this immunity, spleen cells from immune mice were challenged in vitro with lysates of P. vinckei-infected or uninfected erythrocytes. The parasite antigen induced proliferation of T cells from immune mice but not from nonimmune mice. When gamma interferon production by cells from immune mice was assayed at the single-cell level, 1 to 3 cells per 1,000 cells were found to release this cytokine when exposed to antigen. In contrast, the numbers of interleukin 4 (IL-4)-producing cells from both immune and control mice were < or = 4 per 10(6) cells, regardless of antigen exposure. Investigation in a bioassay showed that P. vinckei antigen induced the release of IL-4 from spleen cells of immune mice but not from those of control mice. Nevertheless, that IL-4 is of minor significance in this system is also suggested by the absence of elevation of immunoglobulin E levels in blood samples from these mice, in contrast to what is seen with P. chabaudi infection, in which IL-4-producing Th2 cells are of major importance for immunity during later phases of infection. Taken together, the present results indicate that immunity to P. vinckei is a Th1 response, with gamma interferon being an important protective factor. Whether or not the Th1 response, through overproduction of tumor necrosis factor alpha, is also responsible for pathology and death in this infection remains to be clarified.

Animals↗
PubMed1995

Genetic restriction and specificity of the immune response in mice to fusion proteins containing repeated sequences of the Plasmodium falciparum antigen Pf155/RESA.

The genetic restriction and specificity of the immune response in mice to two fusion proteins, ZZ-M3 and ZZ-M5, were studied. These proteins contain two IgG-binding domains (ZZ) from staphylococcal protein A, and repeated sequences from the C-terminal [(VEHDAEEN)5 (VEEN)10] (M3) or central [(VEEPTVADDEH)3(VEEPTVAEEH)2] (M5) regions of the Plasmodium falciparum malaria blood stage antigen Pf155/RESA. Strong antibody and T-cell responses to M3 and M5 were linked to expression of the I-Ak allele, and T-cell responses to the bacterial fusion partner ZZ were restricted to mice of the H-2k haplotype. The response to M5 was less restricted than that to M3, giving intermediate responses in mice of H-2d haplotypes as well. However, ZZ-M5-primed lymph node (LN) cells from these mice were primarily induced to proliferate in vitro by the complete ZZ-M5 construct and not by synthetic peptides representing the repeated subunits in M5. The reactivity with intact Pf155/RESA in erythrocyte membrane immunofluorescence was weak of antisera from mice immunized with ZZ-M5, whereas the reactivity of antisera from mice immunized with ZZ-M3 roughly paralleled their reactivity with M3 in an enzyme-linked immunosorbent assay (ELISA). The antibody responses induced by immunization with ZZ-M3 or ZZ-M5 were specific for M3 or M5, respectively, while activated T cells displayed cross-reactivity between M3 and M5 in an in vitro proliferation assay. The results indicate that the assembly of repeated sequences in fusion proteins affects both the MHC class II restriction and the specificity of the induced antibody and T-cell responses.

Amino Acid Sequence↗
PubMed1994

Presentation of the Plasmodium falciparum antigen Pf155/RESA to human T cells. Variations in responsiveness induced by antigen presenting cells from different but MHC class II identical donors.

The antibody response in humans naturally primed to a malaria vaccine candidate antigen (Pf155/RESA) is genetically regulated. Here, the impact of antigen presenting cells (APC) on the control of in vitro T-cell responses induced by Pf155/RESA or synthetic peptides corresponding to its major Pf155/RESA epitopes was studied. T cells and APC were from the peripheral blood of monozygotic or dizygotic twins and their age matched siblings, all living in the central highlands of Madagascar. When induced to proliferate (thymidine incorporation) in vitro by antigenic peptides, the T-cell responses varied less within the twin pairs than between them and their siblings or the entire group, implying that they were genetically regulated. Occasional MHC class II associations of some of the responses were weak and did not reflect underlying MHC class II restrictions. When T cells and APC from different but MHC class II identical donors were incubated in various combinations, antigen charged APC from homologous donors induced in vitro T-cell proliferation which differed from that induced by the T-cell donors' own APC. Pretreatment of the APC with either paraformaldehyde or anti-class II antibodies inhibited or abolished this antigen dependent T-cell proliferation. The results suggest that the observed differences in T-cell responses induced by APC from different donors reflect differences at the level of these cells. Whether they reflect differences in the proteases involved in antigen processing, in the costimulatory signals provided by the APC to the T cells or in the secretion of other regulatory factors remains to be elucidated.

Adolescent↗
PubMed1994

B- and T-cell responses in congenic mice to repeat sequences of the malaria antigen Pf332: effects of the number of repeats.

The Plasmodium falciparum antigen Pf332 comprises degenerated 11-amino-acid repeats with regularly spaced pairs of glutamic acid. Epitopes formed by such repeats are recognized by polyclonal and monoclonal antibodies that interfere with the life cycle of the blood stages of the malaria parasite. In order to study the immunogenicity of one such Pf332 repeat sequence (SVTEEIAEEDK), fusion proteins containing ZZ (two IgG binding domains of staphylococcal protein A) and dimers, trimers or tetramers of the malarial sequence were injected into mice. To analyse possible major histocompatibility complex class II restrictions of the immune response, mice of different H-2 haplotypes were used. A significant antibody response was elicited by administration of all the three fusion proteins in mice expressing the I-Ak allele (B10.BR, B10.A(2R) and B10.A(4R)) whereas B10 and C57BL/6 (H-2b) mice were low responders. In comparison, B10.D2 (H-2d) mice were low responders to fusion proteins with 2 or 3 repeats but responded well to the protein containing 4 repeats. Lymph node cells from B10.BR (H-2k) mice, primed in vivo with ZZ-fusion proteins containing either 2 or 4 repeats, proliferated in vitro in response to repeat sequences fused to ZZ or to an unrelated fusion partner, as well as to a synthetic peptide containing less than two repeats. In contrast, a response of lymph node cells from B10.D2 (H-2d) mice was only obtained when a fusion protein containing 4 repeats was used both for in vivo priming and in vitro restimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

IgE elevation and IgE anti-malarial antibodies in Plasmodium falciparum malaria: association of high IgE levels with cerebral malaria.

In the course of studying immunoregulation in human Plasmodium falciparum malaria we have investigated IgE levels and IgE anti-plasmodial antibodies in children and adults from areas of high malaria endemicity in both Africa and Asia. On average, 85% of all donors had significantly elevated levels of total IgE. A fraction of the IgE had anti-plasmodial activity as revealed by ELISA with lysates of infected erythrocytes as antigen. Using synthetic peptides representing antigenic regions of two major plasmodial blood stage antigens, IgE antibody concentrations ranged from 5 to 15 ng/ml serum for each of the peptides. On average, the concentrations of the corresponding IgG antibodies were x 500-1000 higher. Immunoblotting of parasite lysates showed that most donors had IgE antibodies against one or several of a restricted number of plasmodial polypeptides, with antibodies against an antigen of mol.wt 45 kD already being present in all donors at an early age. Donors having IgE antibodies to particular antigens also frequently had corresponding IgG4 antibodies, reflecting underlying IL-4-dependent cellular mechanisms controlling formation of these isotypes. As infection with other parasites such as helminths is known to induce IgE elevation, the results do not prove that plasmodial infections were the primary cause of IgE induction. However, the importance of plasmodial infection for IgE elevation was supported by the finding of significantly higher levels of IgE, but not of IgG, in children with cerebral malaria compared with patients with uncomplicated disease.

Adolescent↗
PubMed1994

Human monocytes cultured with and without interferon-gamma inhibit Plasmodium falciparum parasite growth in vitro via secretion of reactive nitrogen intermediates.

Adherent cells from human peripheral blood were studied for their interaction with asexual blood forms of Plasmodium falciparum in vitro. Freshly isolated monocytes only showed weak anti-parasitic effects. However, an enhancement of this anti-parasitic activity was apparent when monocytes were allowed to mature in vitro. Monocytes activated with IFN-gamma for two or three days had an enhanced anti-parasitic effect. In contrast, the inhibition mediated by cells incubated for five days was the same with or without IFN-gamma treatment. There was no evidence of toxicity when IFN-gamma at high concentrations was added directly to P. falciparum cultures. The anti-parasitic activity of the activated cells seemed to be due to nitric oxide since incubation of macrophages with L-NMMA reduced the level of inhibition. However, inhibition was only partial suggesting that other factors also were involved in inhibition of parasite growth.

Animals↗
PubMed1994

Immunosuppression after measles vaccination.

The influence of conventional live attenuated measles vaccine on cellular immune responsiveness was investigated in Sweden and Guinea-Bissau. Sixteen children in a residential area in Bissau and 16 living in southern Stockholm were examined before and 8-10 days after vaccination. Lymphoproliferation was measured to concanavalin A (con-A), PPD and tetanus toxoid (TT) using a whole-blood 3H-thymidine incorporation assay. Stimulation indices were significantly lower after vaccination than before, in the case of con-A (p = 0.03) and TT (p = 0.01) in the Guinean children and in the case of PPD (p = 0.009) and TT (p = 0.03) in the Swedish children. Stimulation of lymphocytes from measles-immune children with measles antigens resulted in weak lymphoproliferative responses. These observations may be relevant to the increased mortality found in children immunized with high-titre measles vaccines, as compared to controls, in recent studies. The study confirms the applicability and usefulness under field conditions of the whole blood version of the thymidine incorporation assay.

Child, Preschool↗
PubMed1994

High molecular weight growth hormone (> 160 kD) in human serum characterized with monoclonal antibodies.

Human growth hormone (hGH) was analyzed by six monoclonal antibodies (Mabs) and a polyclonal antiserum (Pas) before and after molecular sieve chromatography of sera from healthy subjects. Their hGH levels were between < 0.2 and 0.4 ng/ml as determined with Pas. The six Mabs reacted with five distinct epitopes and bound to a hGH fragment corresponding to the amino acid sequence 15-125. Two of the Mabs showed reduced binding to 20-kD hGH. The binding of Mabs to dimeric forms of hGH varied. Human GH levels in unfractionated sera as determined with Mabs were < 3.1-390 ng/ml. After molecular sieve chromatography of the sera, one peak of hGH-immunoreactive material of high molecular weight (> 160 kD) and one at the elution volume of monomeric hGH were determined with Pas and Mabs. The major part of the high molecular weight hGH (> 160 kD) seemed to consist of 22-kD hGH molecules, since Pas and all Mabs detected the hGH immunoreactivity (> 160 kD) in a similar manner. This high molecular weight hGH (> 160 kD) was distinguishable from the identified, receptor-like hGH-binding protein in serum.

Adult↗
PubMed1994

T-cell control of immunity to the asexual blood stages of the malaria parasite.

Both antibody-dependent and antibody-independent mechanisms are involved in immune protection against the asexual blood stages of the malaria parasite. It is well established that T cells play a crucial role in both induction and maintenance of this immunity. Of the two T-cell subsets (CD4+, CD8+) carrying alpha/beta T-cell receptors, the CD4+ T cells are of major importance for the development of blood stage immunity in both experimental and human malaria. In mice, CD4+ T cells comprise at least two functionally distinct cell types (TH1, TH2), distinguished on the basis of their lymphokine production. The balance between these subsets is critical for the outcome of an infection. In some rodent malarias, TH1 cells producing IFN-gamma and IL-2 are important for controlling infection in its early phases, while TH2 cells, producing i.a. IL-4 and IL-10, together with antibodies, are important for parasite clearance in later phases of infection. Distinct CD4+ T cells of either TH1 or TH2 type also have regulatory functions in human P. falciparum infection. In contrast to the CD4+ T cells, the role of CD8+ T cells in blood stage infection appears to be limited, but suppression of some CD4+ activities has been reported for both experimental and human malaria. As in other infections, peripheral T cells equipped with gamma/delta receptors are strongly upregulated in malaria and also respond to parasite antigens in vitro by proliferation and lymphokine production. However, the importance of the gamma/delta T cells for protection when compared with pathogenesis is presently unclear. Rapid advances made in recent years in the characterization and cloning of plasmodial antigens eliciting immune protection have made it possible to define some of the antigenic structures involved in T-cell immunity. This, together with an improved understanding of cellular mechanisms, provides some basis for the development of modern malaria vaccines.

Animals↗
PubMed1994

Lymphocyte responses to Plasmodium falciparum ring-infected erythrocyte surface antigen (Pf155/RESA) peptides in individuals with naturally acquired Plasmodium falciparum malaria.

Antibody titers and lymphocyte responses to synthetic peptides corresponding to repeated amino acid sequences of the 3' and 5' regions of Pf155/ring-infected erythrocyte surface antigen (RESA) were studied in two groups of Thai subjects, soldiers (Rangers), and villagers who differed in their history of malaria exposure. The frequency of Pf155/RESA seropositivity was similar in the two groups while the frequency of high titer antibody was significantly greater in villagers than in Rangers. Lymphocyte responsiveness in vitro to all Pf155/RESA peptides was infrequent for both groups although half of the subjects studied responded to crude Plasmodium falciparum asexual blood stage malaria antigen (MA). Among responders, Pf155/RESA peptides elicited lymphocyte responses in which proliferation and interferon-gamma (IFN-gamma) production were not associated, whereas with MA, the two responses were associated. The MA-stimulated lymphocyte proliferation and IFN-gamma production for both groups of volunteers appeared to be independent of antibody titer. In this study, antibody, but not lymphocyte, responses to Pf155/RESA peptides were shown to reflect differences in prior exposure and levels of acquired immunity to falciparum malaria.

Adult↗
PubMed1994

A longitudinal study of seroreactivities to a major blood stage antigen (Pf155/RESA) of the malaria parasite Plasmodium falciparum in an endemic area of Thailand.

We have performed a longitudinal study of the formation of antibodies to Plasmodium falciparum in an area of Thailand where malaria transmission is moderate and seasonal. The study population comprised 118 subjects living in two villages 230 km southeast of Bangkok. All subjects included in this study were seropositive for antibodies to the blood stages of P. falciparum but only approximately 80% had antibodies to the blood stage antigen Pf155/RESA when assayed by erythrocyte membrane immunofluorescence (EMIF) or peptide ELISA during the period of maximal transmission. The reduced capacity to form these antibodies in a significant fraction of subjects living under comparable environmental and socio-economic conditions may reflect a genetic but antigen specific non-responsiveness. Both seropositivity and mean antibody titers to Pf155/RESA and its B-cell epitopes tended to be slightly higher during the rainy than during the dry season but the seasonal variations were slight and statistically not significant. Parasite rates were significantly higher in the rainy than in the dry season in both the EMIF positive and the EMIF negative groups. However, during the rainy season, the parasite rates in subjects with no or low titered antibodies to Pf155/RESA were significantly higher than those in subjects having such antibodies. The results suggest that antibodies to Pf155/RESA and some of its defined epitopes may be of importance for controlling parasitemias.

Adolescent↗
PubMed1994

Humoral immune responses to Plasmodium falciparum antigens in children and adults living in a hypoendemic area of Punjab (Pakistan).

We have investigated the prevalence and the levels of antibodies reactive with repeat sequences in Plasmodium falciparum asexual blood-stage Pf155/ring-infected erythrocyte surface antigen (RESA), Pf332 antigen, and the circumsporozoite (CS) protein in 532 children and adults residing in a hypoendemic area in the Punjab (Pakistan). We show here that the levels of antibodies reactive with synthetic peptides corresponding to repeat sequences in these antigens increased gradually with age. However, the prevalence and levels of antibodies reactive with the peptides were quite low as compared with the high prevalence of such antibodies in donors from areas holoendemic and hyperendemic for malaria. The levels of Ag332 (2-12)2-reactive antibodies in individual sera as well as in the study population as a whole correlated well with the levels of antibodies to the Pf155/RESA peptide (EENV)6. However, there was no correlation between anti-(EENV)6 and anti-Ag332 (2-12)2 antibody levels and malaria parasitemia. There was a significant negative correlation between anti-(NANP)6-reactive antibodies and the parasite rate, suggesting that a heavy load of blood-stage parasites may be one factor that exerts an immunosuppressive effect on the antibody response to the sporozoites.

Adult↗
PubMed1993

Plasmodium falciparum: analysis of the cytoadherence inhibition of the human monoclonal antibody 33G2 and of antibodies reactive with antigen Pf332.

The capacity of a human monoclonal antibody (MAb 33G2) to interfere in vitro both with Plasmodium falciparum merozoite invasion and cytoadherence of infected erythrocytes to melanoma cells has been reported. MAb 33G2 cross-reacts with several P. falciparum antigens but shows highest reactivity with repeated sequences in the asexual blood stage antigen Pf332. This study was conducted in order to further analyze the cytoadherence inhibition mediated by MAb 33G2 and to evaluate the relative contribution of antibodies to Pf332 in the inhibitory activity of immunoglobulins from P. falciparum immune donors. We show here that MAb 33G2 inhibits cytoadherence of infected erythrocytes (PRBCs) with similar efficiency independently of the strain of parasite, while the inhibitory capacity of immunoglobulin fractions from Liberian immune donors was restricted to some strains only. There appears to be no correlation between the reactivity with Pf332 of immunoglobulin preparations from different donors and their capacity to inhibit cytoadherence of PRBCs to melanoma cells. In contrast to MAb 33G2, polyclonal antibodies affinity purified on the Pf332 peptide containing the epitope seen by the MAb showed little or no inhibition of cytoadherence of infected erythrocytes.

Amino Acid Sequence↗
PubMed1993

Enzyme-linked staining method for light microscopic detection of antibodies to parasite antigens on the membrane of Plasmodium falciparum infected erythrocytes.

Indirect erythrocyte membrane immunofluorescence (EMIF), a standard method for detection of antibodies to the P. falciparum blood stage vaccine candidate antigen Pf155/RESA, has been adapted to light microscopy by enzyme-linked immunostaining of the erythrocyte membrane, using alkaline phosphatase and chromogenic substrate. This method gives a dark blue staining of the membranes of ring infected erythrocytes. Results obtained with 70 African sera in EMIF and in enzyme immunostaining correlated well although the enzyme based method sometimes resulted in higher antibody titers and appeared to be slightly more sensitive. Similar results were obtained when comparing immunofluorescence with enzyme immunostaining for detection of antibodies to intraerythrocytic parasite antigens. The enzyme linked immunostaining described is simple and fast and does not require expensive equipment and should, thus, be well suited for use in laboratories with limited resources or under field conditions.

Animals↗
PubMed1993

Analysis of a human monoclonal antibody reactive with multiple Plasmodium falciparum antigen repeat sequences using a solid phase affinity assay.

A solid-phase affinity assay was set up for the determination of the affinity of the interaction between the human monoclonal antibody (mAb) 33G2 and peptides corresponding to repeated sequences in three blood stage antigens of the malaria parasite Plasmodium falciparum. The epitope of this mAb is of interest due to the parasite blocking capacity of the mAb. Previous studies with PEPSCAN have defined the minimal epitope for the mAb as the pentapeptide VTEEI, a sequence frequently found in antigen Pf332. In the previous study, epitopes responsible for the cross-reactivity of the mAb with antigens Pf155/RESA and Pf11.1 were also identified. In the affinity assay described herein, the mAb was coated on a solid phase and binding of a labelled peptide was displaced by homologous or heterologous peptides. The affinity of peptides corresponding to Pf332 increased with increasing length, and the highest affinity was displayed by a dimer (23 amino acids) of a Pf332 repeat (K = 1.9 x 10(8) M-1). Peptide length did not influence the binding of peptides corresponding to the Pf155/RESA and Pf11.1 repeats, which had lower affinities comparable to that of the shortest Pf332 octapeptide (K = 2.2 x 10(4) M-1). Only peptides containing binding sites as defined by PEPSCAN analysis showed a measurable binding. When using peptides as inhibitors in peptide ELISA, binding correlated with the affinity of the peptides, but only the high affinity peptides were inhibitory. In contrast, a poor correlation was found when peptides were used directly for coating in ELISA.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Seroreactivity with the Plasmodium falciparum blood stage antigen Pf332 in adults and children from malaria-endemic regions.

It has earlier been reported that the human monoclonal antibody (MoAb 33G2) and polyclonal antibodies reactive with Pf332 may interfere in vitro with the erythrocytic cycle of Plasmodium falciparum at two potential target sites for protective antibodies, indicating that the antigen may constitute an important target for immune responses during malaria infections. MoAb 33G2 shows its highest reactivity with repeated sequences in the antigen Pf332 and also cross-reacts with determinants in Pf155/RESA. This study was conducted in order to assess the prevalence of seroreactivity against Pf332 in individuals residing in areas of different malaria endemicity, and in children with different degrees of disease severity. We now report that individuals resident in malaria-endemic regions show a high prevalence of seroreactivity to antigen Pf332 repeat sequences. The mean antibody concentrations were significantly higher in donors from Liberia, Madagascar and Gambia compared with Thai and Colombian donors, probably reflecting the higher degree of exposure in the African regions. Although the levels of such antibodies in individual sera correlated well with the levels of antibodies to one Pf155/RESA repeat peptide, only a minor part of the peptide-reactive antibodies were cross-reactive between the two antigens. In Gambian children, the mean concentrations of antibodies reactive with Pf332 or Pf155/RESA peptides were significantly higher in children with severe than with mild malaria. Further longitudinal studies are needed to evaluate the capacity of Pf332 to induce potentially protective or harmful antibody responses.

Adult↗