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R S Nussenzweig

Publications and source records attributed to R S Nussenzweig.

At least 19 recordsLinked to original sources
PubMed1992

Recognition of different domains of the Plasmodium falciparum CS protein by the sera of naturally infected individuals compared with those of sporozoite-immunized volunteers.

The fine specificities of antibodies to the circumsporozoite (CS) protein of Plasmodium falciparum, present in the sera of volunteers immunized with irradiated P. falciparum sporozoites, were defined and compared to those of sera from persons living in a malaria-endemic area in West Africa. The specificity of these anti-CS antibodies was determined by ELISA, using recombinant proteins and synthetic peptides containing repeat and nonrepeat sequences of this CS protein. All 10 serum samples of the five sporozoite-immunized volunteers displayed very high antibody titers to the immunodominant repeat (NANP)n of the CS protein. However, only three of the serum samples of these vaccinees reacted with a single nonrepeat region and only at low titers. In contrast, a high percentage of sera from adults living in the malaria-endemic area who had been exposed to sporozoites, as well as liver and blood stages of P. falciparum, had high antibody levels, not only to the repeats but also to several nonrepeat regions of the CS protein. Furthermore, a number of sera from children living in this endemic area displayed appreciable levels of antibodies to the nonrepeat regions, in the absence of any antirepeat reactivity. Sera of Saimiri monkeys, which had undergone multiple blood-induced P. falciparum infections, consistently contained high titers of antibodies to several nonrepeat sequences of the CS protein, whereas only a few of these sera had low titers of antirepeat antibodies. Antibody binding sites, in nonrepeat regions, were mapped using synthetic polymers containing multiple copies of selected C-terminal sequences of the P. falciparum CS protein. The binding to sporozoites of antibodies to nonrepeat regions of the CS protein was determined. The basis for the differences in antibody binding sites of sera from persons immunized with irradiated sporozoites, compared to those from an endemic area, is discussed.

Adolescent↗
PubMed1992

The in vivo cytotoxic activity of CD8+ T cell clones correlates with their levels of expression of adhesion molecules.

CD8+ T cell clones specific for a defined epitope present in the circumsporozoite protein of Plasmodium yoelii display striking differences in their in vivo antiplasmodial activity. The adoptive transfer of certain clones (YA23 and YA26) into naive mice inhibits by 90% or more the development of liver stages of malaria parasites and protects against malaria infection. The adoptive transfer of two other T cell clones (YB8 and YA15) results, respectively, in partial or no inhibitory activity on parasite development. We found that "protective" and "nonprotective" cytotoxic T lymphocyte (CTL) clones do not differ in their fine epitope specificity and display similar levels of lysis and DNA degradation of target cells in vitro. Their pattern of production of lymphokines and granule-associated proteins also failed to correlate with their in vivo antiplasmodial activity. Histological studies combined with autoradiography showed that, upon adoptive transfer, only T cells from the protective CTL clones are capable of "associating" with a significant percentage of parasitized hepatocytes. Fluorescence-activated cell sorter analysis of surface molecules revealed pronounced differences in the levels of CD44 and VLA-4 expression by the different clones, correlating closely with their in vivo protective activity. The correlation between in vivo antiparasite activity and the expression of CD44 was further corroborated by the results of sorting, from the partially protective YB8 clone, two sub-populations expressing high and low levels of CD44. These were protective and nonprotective, respectively. The clones also differed in their adhesive properties. Cross-linking of CD44, using specific antibodies, induced LFA-1-mediated homotypic aggregation of protective clones, while nonprotective cells failed to aggregate.

Amino Acid Sequence↗
PubMed1992

T cell responses to repeat and non-repeat regions of the circumsporozoite protein detected in volunteers immunized with Plasmodium falciparum sporozoites.

The design of a malarial vaccine based on the circumsporozoite (CS) protein, a major surface antigen of the sporozoite stage of the malaria parasite, requires the identification of T and B cell epitopes for inclusion in recombinant or synthetic vaccine candidates. We have investigated the specificity and function of a series of T cell clones, derived from volunteers immunized with Plasmodium falciparum sporozoites, in an effort to identify relevant epitopes in the immune response to the pre-erythrocytic stages of the parasite. CD4+ T cell clones were obtained which specifically recognized a repetitive epitope located in the 5' repeat region of the CS protein. This epitope, when conjugated to the 3' repeat region in a synthetic MAPs construct, induced high titers of antisporozoite antibodies in C57BL mice. A second T cell epitope, which mapped to aa 326-345 of the carboxy terminal, was recognized by lytic, as well as non-lytic, CD4+ T cells derived from the sporozoite-immunized volunteers. The demonstration of CD4+ CTL in the human volunteers, and the recent studies in the rodent model (Renia et al., 1991; Tsuji et al., 1990), suggest that CS-specific CD4+ T cells, in addition to their indirect role as helper cells in the induction of antibody and CD8+ effector cells, may also play a direct role in protection against sporozoite challenge by targeting EEF within the liver.

Amino Acid Sequence↗
PubMed1991

T cell epitopes of the circumsporozoite protein of Plasmodium vivax. Recognition by lymphocytes of a sporozoite-immunized chimpanzee.

The humoral and cellular antisporozoite immune responses of a laboratory-born chimpanzee were measured following multiple exposures to the bites of Plasmodium vivax-infected mosquitoes. T cell lines and clones derived from the chimpanzee's PBL were used to identify T cell epitopes of the P. vivax circumsporozoite (CS) protein. Two independently obtained cell lines, established by culturing the PBL with either a recombinant P. vivax circumsporozoite (rPvCS) protein or a pool of synthetic peptides spanning the rPvCS sequence, recognized a 20-mer peptide from a nonpolymorphic region of the carboxyl terminus of the CS protein. This peptide overlaps a sequence homologous to region II of the Plasmodium falciparum CS protein. A third T cell line recognized an epitope within the central repeat domain, which has recently been found to be a polymorphic region of the P. vivax CS protein. The CD4+ clones derived from this third T cell line secreted IFN-gamma and IL-2 when stimulated with either the P. vivax repeat peptide (DRAAGQPAG)2 or the rPvCS protein.

Amino Acid Sequence↗
PubMed1991

Immunogenicity of multiple antigen peptides (MAP) containing T and B cell epitopes of the repeat region of the P. falciparum circumsporozoite protein.

The immunogenicity of multiple antigen peptides (MAP) constructs containing T and B cell epitopes of the repeat region of the P. falciparum circumsporozoite (CS) protein was examined in vitro, using a human T cell clone, and in vivo, using four different strains of mice. All the MAP constructs that contained the T cell epitope, (DPNANPNVDPNANPNV), stimulated proliferation and interferon-gamma production by a human T cell clone specific for this epitope which is located in the 5' end of the repeat region of the P. falciparum CS protein. These human T cells did not recognize MAP that contained only the B cell epitope, (NANP)3, which is located in the 3' repeat region. Optimal antibody responses were obtained in mice immunized with MAP containing four copies of tandemly arranged T and B cell epitopes, (TB)4. The murine immune response to the MAP constructs was genetically restricted. Mice of a high responder strain, C57BL, recognized both the 5' and 3' repeat sequences in the MAP as T, as well as B, cell epitopes and developed very high anti-MAP and anti-sporozoite antibody titers. A/J and C3H mice, which were intermediate responders, developed lower antibody titers which varied according to the orientation of the T vs. the B cell epitopes within the MAP constructs. BALB/c mice were nonresponders and did not develop antibodies following immunization with any of the MAP constructs containing the 5' and 3' repeats of the P. falciparum CS protein.

Amino Acid Sequence↗
PubMed1991

CD8+ cytolytic T cell clones derived against the Plasmodium yoelii circumsporozoite protein protect against malaria.

Immunization of BALB/c mice with radiation-attenuated Plasmodium yoelii sporozoites induces cytotoxic T lymphocytes (CTL) specific for an epitope located within the amino acid sequence 277-288 of the P. yoelii circumsporozoite (CS) protein. Several CD8+ CTL clones were derived from the spleen cells of sporozoite-immunized mice, all displaying an apparently identical epitope specificity. All the clones induced high levels of cytolysis in vitro upon exposure to peptide-incubated MHC-compatible target cells. The adoptive transfer of two of these clones conferred complete protection against sporozoite challenge to naive mice. This protection is species and stage specific. Using P. yoelii specific ribosomal RNA probes to monitor the in vivo effects of the CTL clones, we found that their target was the intrahepatocytic stage of the parasite. The protective clones completely inhibited the development of the liver stages of P. yoelii. Some CTL clones were only partially inhibitory in vivo, while others failed completely to alter liver stage development and to confer any detectable degree of protection. The elucidation of the effector mechanism of this CTL mediated protection against rodent malaria should facilitate the design of an effective malaria vaccine. From a broader perspective this model may provide further insight into the mechanism(s) of CTL mediated killing of intracellular non-viral pathogens in general.

Animals↗
PubMed1991

Inhibitory activity against Plasmodium vivax sporozoites induced by plasma from Saimiri monkeys immunized with circumsporozoite recombinant proteins or irradiated sporozoites.

Two Saimiri monkey vaccine trials have been conducted comparing four recombinant Plasmodium vivax circumsporozoite proteins and irradiated sporozoites. Only a small number of animals immunized with certain recombinants or irradiated sporozoites became fully protected against sporozoite challenge. Preimmunization and postimmunization plasma samples obtained from 30 monkeys on the day of challenge were tested in an in vitro assay based on sporozoite development into exoerythrocytic stages in primary cultures of Saimiri monkey hepatocytes. The percentage of inhibition was determined by comparison of the number of exoerythrocytic stages developing from sporozoites preincubated with a preimmunization and a postimmunization plasma sample of each animal. The plasma samples of the day of challenge of nearly all the immunized animals had a variable, but significant inhibitory effect, when compared with the corresponding preimmunization sample. We found no correlation between the degree of in vitro inhibition of liver stage development, and the in vivo protection against sporozoite challenge of individual animals. The variable results of the incubation of sporozoites with "normal" plasma of different animals indicates that the in vitro results were affected by plasma factors unrelated to anti-sporozoite antibodies.

Animals↗
PubMed1990

Plasmodium falciparum: restricted polymorphism of T cell epitopes of the circumsporozoite protein in Brazil.

We examined the extent of variation of the 3' region of the circumsporozoite gene among Plasmodium falciparum isolates through amplification of a selected DNA fragment followed by DNA sequencing. A total of 32 isolates were analyzed, of which 24 were from Amazon endemic areas in Brazil and 8 from widely separated geographical regions in the world. Among Brazilian isolates only 2 variants were detected: 19 displayed the same sequence of strain 7G8 whereas the 4 remaining isolates differed from the 7G8 strain at five nucleotide positions which also led to amino acid changes. Variation was restricted to one of the T-helper epitopes while the sequence identified as a cytotoxic T cell epitope was conserved in all Brazilian isolates. P. falciparum samples from other geographical regions in the world showed sequences distinct from those of Brazilian isolates. However, some constancy could be observed within that variation. For instance, the most frequent nucleotide substitutions, from A and C at nucleotide positions 1015 and 1024, were the same in all isolates.

Amino Acid Sequence↗
PubMed1990

Isolation and characterization of protective cytolytic T cells in a rodent malaria model system.

Protective immunity against malaria is induced by immunization with irradiation-attenuated sporozoites. Here we report the isolation of cytolytic T-cell (CTL) clones from BALB/c (H-2d) mice immunized with either Plasmodium berghei or Plasmodium yoelii sporozoites. The epitopes recognized by these CTL can be mimicked by synthetic peptides corresponding to a homologous region in the CS proteins of both rodent malaria species. Both peptides are recognized by the CTL in the context of the same MHC class I molecule, H-2 Kd. In vivo adoptive transfer of the CTL clones into non-immune syngeneic mice protected them from a lethal challenge of infectious sporozoites.

Amino Acid Sequence↗
PubMed1990

Further studies on the immunization of Saimiri sciureus boliviensis with recombinant vaccines based on the circumsporozoite protein of Plasmodium vivax.

Reported are the results of a trial in squirrel monkeys of 2 Plasmodium vivax malaria vaccine candidates based on the circumsporozoite (CS) protein, namely, rPvCs-2 and rPvCS-3. Compared with an earlier recombinant P. vivax CS construct, rPvCS-1, rPvCS-2 has an additional 24 amino acids at the C-terminal, which includes the thrombospondin region of homology and a putative T cell epitope. The rPvCS-3 was generated from a chemically synthesized gene that contained an additional 54 amino acids at the amino terminus and terminates at the same carboxy-terminal amino acid as rPvCS-2. In addition, rPvCS-3 contained only 1 each of the repeat sequences DRADGQPAG and DRAAGQPAG. Both antigens were administered with alum as adjuvant. Neither formulation caused toxic side effects and both recombinant molecules induced high antibody titers. Two monkeys were protected against sporozoite challenge by immunization with rPvCS-2 antigen, while none of the rPvCS-3 immunized animals displayed any degree of protection. While there was no correlation between protection and antibody titer or the in vitro proliferation of lymphocytes in response to the antigens, this is further evidence to support the role of the repeating epitopes in generating protective immunity.

Amino Acid Sequence↗
PubMed1979

Antibodies to sporozoites: their frequent occurrence in individuals living in an area of hyperendemic malaria.

Serum samples from 158 West Africans were tested for antibodies against sporozoites, the vector stage of the malaria parasite. Antibodies specific for Plasmodium falciparum sporozoites were detected by means of the circumsporozoite precipitation assay and indirect immunofluorescence. More than 90 percent of the serum samples from adults gave positive immunofluorescent reactions against falciparum sporozoites, whereas most of the samples from children gave low or negative reactions.

Adolescent↗
PubMed1979

Immune phagocytosis in murine malaria.

Spleen macrophages from Plasmodium berghei-infected mice are more efficient in the ingestion of parasitized reticulocytes than spleen macrophages obtained from normal animals. Other indications of spleen macrophage activation detected during malarial infection are enhanced macrophage spreading and increased phagocytosis of opsonized and nonopsonized sheep erythrocytes (E). Peritoneal macrophages are not activated to a significant degree. The appearance of antibodies directed against Forssman antigen, but not to other erythrocyte antigens, is also a feature of this infection and explains the ingestion of unsensitized E by spleen macrophages of the diseased animals. The recognition and ingestion of parasitized reticulocytes by infected mice in mediated by cold-agglutinin type immunoglobulins that appear during P. berghei infection and can be blocked by the Fc-binding protein A from Staphylococcus aureus. In advanced stages of the disease, the serum of infected animals inhibits phagocytosis, probably because of the high level of circulating immune complexes. Thus, the clearance of malaria parasites is regulated by several elements of the immune system, in addition to levels of specific antimerozoite antibodies, including the amount of antibodies bound to reticulocytes, the presence of circulating immune complexes, and the degree of macrophage stimulation.

Animals↗
PubMed1979

Freeze-fracture study of malaria sporozoites: antibody-induced changes of the pellicular membrane.

Plasmodium cynomolgi, Plasmodium knowlesi, and Plasmodium berghei sporozoites, before and after incubation with immune serum, were studied after freeze-fracture by electron microscopy. There were evenly distributed numerous intramembranous particles (IMP) on the P face of the outer membrane. The E face of the plasma membrane had fewer IMP than its P face. The E face of the intermediate membrane had few IMP and also linear arrays of slightly raised ridges running the length of the parasite. The P face of the intermediate membrane had many IMP aligned along the long axis of the sporozoite. On the P face of the inner membrane, IMP were arranged in very distinct rows conforming to the long axis of the parasite; the E face of this membrane had a few randomly distributed IMP. A prominent change in the sporozoite incubated in immune serum was the appearance of a layer of aggregated particles around the parasite. The P face of the plasma membrane had several clear areas devoid of IMP and IMP aggregates. No changes were seen in the other fractured faces of the pellicle. These observations suggest that immune serum acts only on the P face of the plasma membrane.

Animals↗
PubMed1979

Membrane-bound antibodies to bloodstream Trypanosoma cruzi in mice: strain differences in susceptibility to complement-mediated lysis.

The Y, CL and other strains of Trypanosoma cruzi display different morphological and immunological characteristics. Such observations are here extended to the interaction of bloodstream forms of different strains of T. cruzi with components of the complement system. We demonstrate that the bloodstream forms of the Y and B strains, but not those of the CL strain, are lysed by normal human serum. Lysis is mediated by combined activities of the alternative and classical complement pathways. These activities are triggered by antibodies on the surface of the parasites as shown by: (a) binding of fluorescein or radiolabelled anti-mouse immunoglobulin to the parasite's membrane and (b) the finding that bloodstream forms from lethally irradiated mice can be sensitized and rendered susceptible to complement-mediated lysis by incubation with sera from acutely infected animals. Bloodstream forms of the CL strain also bear surface immunoglobulin and sensitizing antibodies are present in the sera of mice infected with this strain. However, CL trypomastigotes from acutely infected mice fail to be lysed by human or mouse complement unless the parasites are pre-incubated with sera from chronically infected animals. The basis of the different interactions between CL and Y trypomastigotes with antibodies and the complement system, and their biological significance are discussed.

Animals↗