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F Zavala

Publications and source records attributed to F Zavala.

At least 19 recordsLinked to original sources
PubMed1992

Immunogenic properties of multiple antigen peptide systems containing defined T and B epitopes.

Immunization with chemically defined synthetic polymers, multiple Ag peptide (MAP) systems, containing T and B epitopes of the circumsporozoite protein of P. berghei induce high levels of circulating antibodies that are detectable several months after boosting. The anti-MAP secondary antibody response is characterized by an increase in the levels of circulating IgG and a concomitant decrease in the IgM levels. In vitro and in vivo experiments indicated that Th epitopes included in the MAP are recognized by T cells induced after immunization with the native protein and, also, that MAP-induced T cells can recognize the native protein. In addition to high levels of anti-B epitope antibodies, MAP immunization also induces antibodies against the T epitope. This anti-T epitope immune response does not affect the generation of the anti-B epitope antibodies. Immunization of different strains of mice revealed that the antibody response is consistent with the genetically restricted pattern of recognition of the T epitope. There are, however, significant differences in the levels of antibody responses observed among responder strains. The findings of this study indicate that MAP are potent immunogens capable of inducing immunologic memory and are, thus, good candidates for the development of subunit vaccines designed to induce high levels of circulating antibodies.

Animals↗
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

Monoclonal antibodies recognize a processing dependent epitope present in the mature CS protein of various plasmodial species.

In the present paper, we have characterized the specificity of a series of monoclonal antibodies (MoAbs) against Plasmodium berghei sporozoites, selected for their lack of reactivity with the repeat domain of the circumsporozoite (CS) protein. We found that these MoAbs recognize Pb44, the mature membrane form of the CS protein, but they do not react with Pb54, its precursor. Furthermore, these MoAbs do not react with any of the synthetic peptides representing the linear sequence of the P. berghei CS protein nor do they react with a recombinant CS (rCS) protein. These observations indicate that the epitope recognized by these antibodies is expressed only after the processing of the CS protein has occurred. This 'processing dependent epitope' is present in sporozoites of P. berghei, and also in those of P. falciparum, P. yoelii and P. brasilianum. It is not present in sporozoites of the P. cynomolgi-P. vivax complex and of P. gallinaceum. These anti-sporozoite MoAbs strongly inhibit sporozoite invasion of hepatoma cells, in vitro, however, they displayed no protective effect in an in vivo assay.

Animals↗
PubMed1991

A monoclonal antibody against peripheral benzodiazepine receptor activities the human neutrophil NADPH-oxidase.

A murine monoclonal antibody, mAb 8523, raised against whole human pro-monocytic U937 cells recognizes an 18 kDa antigen in human neutrophils (PMN), as determined by immunoprecipitation and by immunodetection on Western blots of SDS-PAGE of PMN membrane fractions. That is 18 kDa antigen corresponds to the phagocyte peripheral benzodiazepine receptor (PBZDR) is evidenced by its co-migration with the 18 kDa covalently labeled PBZDR, detected by autoradiography, and their co-modulation upon phorbol-myristate-acetate activation of PMN. Purified mAb 8523 (IgG2b) is able to dose-dependently and specifically stimulate both the basal and the FMLP-induced oxidative burst of intact human PMN, assessed by luminol-amplified chemiluminescence. This property of the first described monoclonal antibody against PBZDR supports the implication of this receptor in NADPH-oxidase activation and consequently in phagocyte-dependent host defense mechanisms.

Antibodies, Monoclonal↗
PubMed1991

Benzodiazepine anesthesia in humans modulates the interleukin-1 beta, tumor necrosis factor-alpha and interleukin-6 responses of blood monocytes.

The influence of sedative and anxiolytic benzodiazepines on human monocyte function was assessed in 11 patients undergoing anesthesia prior to control endoscopy of the urinary tract. A single i.v. injection of 0.08 mg/kg midazolam induced a marked and delayed inhibition of the lipopolysaccharide-induced production of interleukin-1 beta, tumor necrosis factor-alpha and interleukin-6 by monocytes isolated from peripheral blood. Corticosteroids were not responsible for the observed immunosuppression. These studies demonstrate that, when administered in man, benzodiazepines markedly alter the capacity of monocytes to synthetize major mediators of the host inflammatory response.

Anesthesia↗
PubMed1991

Studies using a recombinant vaccinia virus expressing the circumsporozoite protein of Plasmodium berghei.

A recombinant vaccinia virus was constructed which expressed the circumsporozoite protein of Plasmodium berghei. Four different strains of mice belonging to different haplotypes were immunized with the recombinant virus. The antibody response to the circumsporozoite protein as well as to vaccinia virus varied among the strains, independently of each other. The anti-circumsporozoite protein titers were comparable to that obtained on immunization with irradiated sporozoites. Spleen cells from H2d mice immunized with P. berghei sporozoites showed a significant proliferative response when cultured in vitro with a low multiplicity of the recombinant vaccinia virus. A weak cytotoxic T lymphocyte response specifically targeting the circumsporozoite protein could be identified in spleens of BALB/c (H2d) mice immunized with vaccinia virus when BALB 3T3 cells transformed with a plasmid expressing the circumsporozoite protein under control of the simian virus 40 promoter were used as target cells in the cytotoxic T lymphocyte assay. However, none of the recombinant virus-immunized animals could be protected from a challenge of sporozoites even at the lowest dose of parasite used.

Animals↗
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

Endogenous anxiogenic peptide, ODN-diazepam-binding inhibitor, and benzodiazepines enhance the production of interleukin-1 and tumor necrosis factor by human monocytes.

Benzodiazepines (BZD) have been described to interact with specific peripheral-type receptors on phagocytes. The present study demonstrates that pico- to nanomolar concentrations of BZD compounds enhance the lipopolysaccharide (LPS)-induced production of tumor necrosis factor (TNF) and interleukin-1 (IL-1) by human monocytes, as determined by specific immunoreactive and biological assays for these cytokines. BZD remained ineffective in the absence of LPS. The activity of BZD was restricted to peripheral (Ro 5-4864) and mixed (diazepam, Valium) type ligands, while anxiogenic (beta-carbolines) or anxiolytic (clonazepam) central type ligands had no effect. Interestingly, peptide fragments of the endogenous anxiogenic ligand diazepam-binding inhibitor (DBI), such as octadecaneuropeptide (ODN-DBI) and the octaneuropeptide corresponding to its COOH-terminal sequence, very efficiently modulated the LPS-induced production of both monokines. Similar results were obtained directly within whole blood samples. These results indicate that widely prescribed pharmacological compounds and endogenous anxiety modulators affect molecular mediators of human host defense mechanisms and inflammatory reactions.

Anti-Anxiety Agents↗
PubMed1990

CD4+ cytolytic T cell clone confers protection against murine malaria.

A CD4+ T cell clone (A1.6) was derived from spleen cells of mice immunized with irradiated sporozoites. This T cell clone recognizes an antigen that is shared by sporozoites and blood forms of Plasmodium berghei and differs from the circumsporozoite protein. Clone A1.6 displays cytotoxic activity, produces IFN-gamma and IL-2 in vitro, and recognizes the plasmodial antigen in the context of the class II I-Ed molecule. Passive transfer of this CD4+ clone into naive mice resulted in a high degree of protection against sporozoite challenge.

Animals↗
PubMed1990

Altered expression of neutrophil peripheral benzodiazepine receptor in X-linked chronic granulomatous disease.

This study was aimed at determining whether the peripheral benzodiazepine receptor (PBZDR), which is abundantly expressed on mononuclear phagocytes, is involved in host defense mechanisms depending on phagocyte membrane-associated NADPH-oxidase complex. Analysis by reversible and covalent binding of PBZDR expression on human neutrophils shows that it is modulated during NADPH-oxidase activation with phorbol 12-myristate 13-acetate. Based on a series of 17 patients with chronic granulomatous disease (CGD), results show that PBZDR expression is dramatically impaired in X-linked CGD, an inherited disorder due to a mutation on the gene coding for cytochrome b558 NADPH-oxidase component, whereas it is unaffected in autosomal recessive CGD where cytochrome b558 is normally expressed, suggesting a link between PBZDR and cytochrome b558 expressions. PBZDR can be assigned by covalent binding to an 18-Kd membrane protein. These results suggest that the neutrophil PBZDR, which can accommodate the widely prescribed anxiolytic drug Valium (diazepam), is involved in host defense against pathogens, a function that could be affected by neuroimmune interactions.

Enzyme Activation↗
PubMed1990

Incorporation of T and B epitopes of the circumsporozoite protein in a chemically defined synthetic vaccine against malaria.

We show here an effective and novel approach to engineer peptide-based vaccines using a chemically defined system, known as multiple peptide antigen systems (MAPs), to protect an inbred mouse strain from infection against rodent malaria. 10 mono- and di-epitope MAP models containing different arrangements and stoichiometry of functional B and/or T helper cell epitopes from the circumsporozoite protein of Plasmodium berghei were used to immunize A/J mice. While these mice did not respond to the mono-epitope MAP bearing only the B or T epitope, very high titers of antibody and protective immunity against sporozoite challenge were elicited by di-epitope MAPs, particularly those with the B and T epitopes in tandem and present in equimolar amounts. These results, obtained in a well-defined rodent malaria model, indicate that MAPs may overcome some of the difficulties in the development of synthetic vaccines, not only for malaria but also for other infectious diseases.

Amino Acid Sequence↗
PubMed1990

VH and VL region structure of antibodies that recognize the (NANP)3 dodecapeptide sequence in the circumsporozoite protein of Plasmodium falciparum.

The sporozoite form of Plasmodium falciparum displays on its surface the circumsporozoite (CS) protein. The central domain of this protein possesses a reiterated tetrapeptide sequence Asn-Ala-Asn-Pro (NANP), and greater than 90% of the sporozoite-specific antibodies obtained from individuals living in malaria endemic areas recognize epitopes within this repeat sequence. Considering the highly repetitive structure of this naturally occurring antigen and its immunodominance, we were interested in analyzing the structural diversity of antibodies that bind to the (NANP)3 sequence. Molecular characterization of immunoglobulin heavy and light chain mRNA was performed for five hybridomas that produce antibodies with binding specificity for the dodecapeptide (NANP)3. These hybridomas were produced in BALB/c mice by inoculation with whole P. falciparum sporozoites. Sequence analysis and Northern blotting showed that for heavy chain, three hybridomas used VH elements that belong to the VHIX family and two to the VHJ558 family. Four different V kappa subgroups were represented among the light chains. Different D and J kappa segments are also utilized, while four heavy chain gene rearrangements involved the JH4 segment. These results indicated that multiple VH-VL gene combinations can code for reactivity to the (NANP)3 sequence, demonstrating that the murine antibody response to this immunodominant region is structurally heterogeneous.

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

Protective anti-sporozoite antibodies induced by a chemically defined synthetic vaccine.

Chemically defined synthetic polymers, known as multiple antigen peptide systems (MAPs) represent an effective and novel approach for engineering peptide-based vaccines. Ten different mono and diepitope MAP models, containing different arrangements and stoichiometry of functional B and/or T helper epitopes from the circumsporozoite protein of Plasmodium berghei were used to immunize mice. High titers of antibody and protective immunity against sporozoite challenge were elicited by MAPs containing T and B epitopes arranged in tandem and in equimolar amounts. These results indicate that MAPs may serve as a basis for developing subunit vaccines to induce high levels of antibodies against sporozoites.

Amino Acid Sequence↗