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Biomedical subjects

F Zavala

Publications and source records attributed to F Zavala.

At least 55 records · Page 3Linked to original sources
PubMed1994

Induction of soluble tumor necrosis factor receptor (sTNF-R75) release by HIV adsorption on cultured human monocytes.

Soluble tumor necrosis factor (TNF) receptors were recently detected in the circulation of patients with early HIV-induced disease, at significantly higher levels than in control subjects. They were proposed as markers of disease progression and of the degree of immunodeficiency. We report that adsorption of heat-inactivated HIV-1 LAI to isolated human monocytes triggers the release of both TNF-alpha and its natural specific inhibitor, the soluble TNF receptor (sTNF-R)75, but not that of sTNF-R55. Only limited inhibition of sTNF-R release was obtained in the presence of a fully neutralizing anti-TNF-alpha monoclonal antibody, suggesting that stimulation by TNF-alpha was only partially responsible for sTNF-R release. HIV-1 LAI induced a higher sTNF-R/TNF ratio than lipopolysaccharide, a well-known monocyte activator. Monocytes thus represent a cellular source of sTNF-R that can be detected in the circulation of HIV-infected patients from seroconversion onwards. The release of sTNF-R could be of great significance in the control of HIV infection via the cytokine network and especially TNF-alpha.

HIV Infections↗
PubMed1994

Demonstration of heat-shock protein 70 in the sporozoite stage of malaria parasites.

Three monoclonal antibodies generated by immunization of mice with Plasmodium berghei-infected red blood cells were found to react with the 75-kDa heat-shock protein (HSP70) present in liver stages and erythrocytic forms of the parasites. These antibodies were shown to react with a recombinant protein encoding the carboxyl terminal half of PfHSP70 (aa 365-681). Differently from earlier results, we clearly demonstrated that HSP70 was also expressed in the sporozoite stage, using these monoclonal antibodies in an immunofluorescence and Western immunoblot assay. These monoclonal antibodies react not only with sporozoites of P. berghei, the parasites originally used for the immunization, but also with sporozoites of several other rodent and human plasmodial species. Passive transfer of these monoclonal antibodies into naive mice, simultaneously injected with sporozoites, failed to neutralize the infectivity of P. berghei sporozoites and to inhibit the development of liver stages of P. yoelii.

Animals↗
PubMed1993

Priming with recombinant influenza virus followed by administration of recombinant vaccinia virus induces CD8+ T-cell-mediated protective immunity against malaria.

Live vectors expressing foreign antigens have been used to induce immunity against several pathogens. However, for the virulent rodent malaria parasite Plasmodium yoelii, the use of recombinant vaccinia virus, pseudorabies virus, or Salmonella, expressing the circumsporozoite protein of this parasite, failed to induce protection. We generated a recombinant influenza virus expressing an epitope from the circumsporozoite protein of P. yoelii known to be recognized by CD8+ T cells and demonstrated that this vector induced class I major histocompatibility complex-restricted cytotoxic T cells against this foreign epitope. Immunization of mice with this recombinant influenza virus, followed by a recombinant vaccinia virus expressing the entire circumsporozoite protein, induced protective immunity against sporozoite-induced malaria. The sequence of immunization appears to be crucial, since a primer injection with recombinant vaccinia virus, followed by a booster injection with recombinant influenza virus, failed to induce protection. The protection induced by immunization with these recombinant viruses is mostly mediated by CD8+ T cells, as treatment of mice with anti-CD8 monoclonal antibody abolishes the anti-malarial immunity. The use of different live vectors for primer and booster injections has a synergistic effect on the immune response and might represent an effective general strategy for eliciting protective immune responses to key antigens of microbial pathogens.

Amino Acid Sequence↗
PubMed1993

Increase in IL-6, IL-1 and TNF levels in rat brain following traumatic lesion. Influence of pre- and post-traumatic treatment with Ro5 4864, a peripheral-type (p site) benzodiazepine ligand.

The effects of fluid percussion trauma on brain interleukin (IL)-6, IL-1 and tumor necrosis factor-alpha (TNF-alpha) levels have been studied. In the cortex and hippocampus of control and sham-operated rats, the levels of these cytokines were very low (below 4 units/mg protein) and constant. IL-6 and IL-1 levels in the ipsilateral cortex increased rapidly following trauma to reach a maximum of 350 and 16 units/mg protein, respectively, 8 h after the lesion, remained elevated until 18 h and decreased thereafter to basal values. TNF-alpha levels were maximally elevated (12 units/mg protein) at 3 h and 8 h and returned to basal values by 18 h. Qualitatively similar changes, but with 25-80-fold smaller amplitude, were seen in the contralateral cortex and in the ipsi- and contralateral hippocampus. The levels of IL-6 in the plasma of sham-operated and lesioned rats were only slightly elevated, whereas IL-1 and TNF-alpha were undetectable. Histological studies of brain tissue at early stages after trauma demonstrated an acute hemorrhage associated with neutrophil invasion. The administration of Ro5 4864 (0.5 mg/kg i.p.), a specific ligand of p (peripheral-type benzodiazepine) binding sites, did not result in any significant effect on the levels of IL-6, IL-1 or TNF-alpha in the brain of control or sham-operated animals. However, when administered 24 h before or 15 min after trauma, this benzodiazepine enhanced the increase of these cytokines by 2-4-fold in the ipsilateral cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

The relative contribution of antibodies, CD4+ and CD8+ T cells to sporozoite-induced protection against malaria.

Protective immunity against Plasmodium yoelii, induced by sporozoite immunization, was investigated using a quantitative method based on the measurement of plasmodial ribosomal RNA in the liver of sporozoite-challenged mice. The relative importance of the different immune mechanisms induced by sporozoite immunization was determined by evaluating quantitatively the anti-parasite activity of antibodies, CD4+ and CD8+ T cells. The role of antibodies was determined by passive transfer of immune sera to naive mice. The transfer to mice of sera obtained after a single immunizing dose reduced the liver stages by 47%. The respective contribution of CD4+ and CD8+ T-cell subsets was determined in B10 (H-2b) mice, treated with a monoclonal antibody (mAb) which inhibits B-cell maturation, and subsequently immunized once with irradiated sporozoites. These mice produced low levels of anti-sporozoite antibodies, but were capable of inhibiting the development of liver stages as efficiently as non-manipulated immunized mice. Administration of either anti-CD4 or anti-CD8 mAb to these mice, did not significantly decrease their capacity to inhibit the development of liver stages. We only observed a significant loss of immunity when the mice were depleted in vivo of both CD4+ and CD8+ T cells. In contrast to earlier studies, we found that the induction of protective immunity is not a phenomenon restricted to a few strains of mice having a particular genetic make-up. The apparent non-responsiveness observed in some strains of mice can be overcome by using larger immunizing doses.

Animals↗
PubMed1993

Modulation of tumor necrosis factor-alpha, interleukin-1 beta, interleukin-6, interleukin-8, and granulocyte/macrophage colony-stimulating factor expression in human monocytes by an endogenous anxiogenic benzodiazepine ligand, triakontatetraneuropeptide: evidence for a role of prostaglandins.

Triakontatetraneuropeptide (TTN) is the major processing product of the endogenous anxiogenic peptide ligand of the benzodiazepine receptor, diazepam binding inhibitor. In the present study, we demonstrated by Northern blot analysis that the mRNA levels for tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1 beta, granulocyte/macrophage colony-stimulating factor, IL-6, and IL-8 were significantly increased after 4 hr of incubation of human monocytes with lipopolysaccharide (LPS) and TTN (10(-11) M), compared with cells incubated with LPS alone. Exposure of monocytes for 20 hr to LPS and TTN (10(-11) M) also stimulated TNF-alpha, IL-1 beta and granulocyte/macrophage colony-stimulating factor release by 80%, 110%, and 98%, respectively, relative to the response elicited by LPS alone. Smaller stimulatory effects were observed using the prototypic pharmacological peripheral benzodiazepine Ro5-4864 (10(-11) M) (55%, 72%, and 62%, assessed by means of specific enzyme immunoassays). In contrast, TTN and Ro5-4864 did not modulate LPS-induced IL-6 and IL-8 production. Treatment with the cyclooxygenase inhibitor indomethacin increased IL-1 beta and TNF-alpha secretion but not that of IL-6 or IL-8. The observed stimulatory effects of TTN and indomethacin were not additive. Taken together, these findings suggest a common mechanism of action for TTN and indomethacin, involving PG formation. In this respect, TTN inhibited prostaglandin (PG) E2 production by 30%. The fact that the observed modulatory effects correlated with PG levels suggests the existence of a second-messenger pathway associated with the peripheral-type benzodiazepine receptor. These results indicate that human TTN differentially modulates the LPS-induced expression of proinflammatory cytokines, and they further support the concept that this endogenous psychoactive peptide could be involved in physiological control of the inflammatory response.

Cells, Cultured↗
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↗