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E Medina

Publications and source records attributed to E Medina.

At least 19 recordsLinked to original sources
PubMed2000

Modulation of host immune responses stimulated by Salmonella vaccine carrier strains by using different promoters to drive the expression of the recombinant antigen.

We evaluated whether immune responses stimulated by Salmonella vaccine carriers can be modulated by using different promoters to drive antigen expression. Mice were orally immunized with strains transfected with plasmids carrying beta-galactosidase (beta-gal) under the control of either a constitutive or an in vivo-activated promoter. While alpha-gal-reactive IgG1, IgG2a, IgG2b and IgG3 were detected in sera of mice immunized with Salmonella expressing constitutively beta-gal, higher titers dominated by IgG2a and IgG2b were detected in sera when the in vivo-activated promoter was used. beta-gal-specific proliferative responses of spleen-derived CD4+ T lymphocytes were similar in both groups. However, CD4+ T lymphocytes from mice immunized with the constitutive promoter secreted IL-4, IL-5, IL-6, IL-10 and IFN-gamma (Th1/Th2 pattern), whereas CD4+ cells mainly secreted IFN-gamma (Th1 pattern) when the second construct was used. The spleens of all immunized mice contained beta-gal-reactive CD8+ CTL precursors. The vaccine prototypes were tested for their capacity to control seeding and/or development within the lung of an intravenously delivered aggressive fibrosarcoma transfected with beta-gal. Reduced metastasis and significantly increased mean survival times were observed in all vaccinated mice. However, protection was improved when the carrier expressed beta-gal upon infection (80 % versus 50% survival, p < 0.05).

Administration, Oral↗
PubMed2000

Modulation of immune responses following antigen administration by mucosal route.

Most microbial infections are either restricted to the mucosal membranes or the etiologic agents needed to transit the mucosa. Thus, it is desirable to stimulate a mucosal response following vaccination, to block both infection and disease development. Attenuated vaccine carriers mimic natural infections, triggering also mucosal responses. Similar results can be achieved by administering antigens with appropriate adjuvants. However, the delivery of antigens per se is not sufficient to engender a protective response. A successful immunization requires the elicitation of an appropriate type of immune response (e.g. antibodies vs. cell-mediated immunity, Th1 vs. Th2 helper pattern). Therefore, a successful vaccination strategy demands the choice of adequate antigens, and their appropriate delivery and/or formulation to promote the required quality of immune response. Different strategies to optimize the immune responses elicited following vaccine administration by the mucosal route are discussed.

Adjuvants, Immunologic↗
PubMed1999

Fc-mediated nonspecific binding between fibronectin-binding protein I of Streptococcus pyogenes and human immunoglobulins.

Fibronectin-binding protein I (SfbI) from Streptococcus pyogenes plays a key role in bacterial adhesion to, and invasion of, eukaryotic cells. In addition, SfbI exhibits a considerable potential as mucosal adjuvant and can trigger polyclonal activation of B cells. Here, we report that SfbI is also capable of binding human IgG in a nonimmune fashion. SfbI was reactive with IgG1, IgG2, IgG3, and IgG4 isotypes (type IIo IgG-binding profile). The affinity constant (Kd) of the SfbI-IgG interaction was in the range of 1-2 x 10(-5) M. Further studies demonstrated that the SfbI binding was mediated by the Fc component of the IgG molecule. Experiments performed using purified recombinant proteins spanning different domains of SfbI showed that the IgG-binding activity was restricted to the fibronectin-binding domains, and in particular to the fibronectin-binding repeats. Finally, the presence of recombinant SfbI resulted in an impairment of both phagocytosis of IgG-coated RBCs and Ab-dependent cell cytotoxicity by macrophages. These results demonstrated for the first time that, in addition to its major role during the colonization process, SfbI may also favor bacterial immune evasion after the onset of the infection by interfering with host clearance mechanisms.

Adhesins, Bacterial↗
PubMed1999

Expression of urease does not affect the ability of Bordetella bronchiseptica to colonise and persist in the murine respiratory tract.

To investigate the role played by urease during the Bordetella bronchiseptica infection process, the ability to colonise and persist in the mouse respiratory tract of a urease-negative B. bronchiseptica BB7865 and a BB7865 derivative constitutively expressing urease was compared with that of the wild-type strain. The results obtained showed that neither constitutive expression nor abolishment of urease activity had any significant effect on the course of B. bronchiseptica infection. Therefore, under our experimental conditions, urease is not essential for B. bronchiseptica to colonise and persist within the murine host.

Animals↗
PubMed1999

Salmonella vaccine carrier strains: effective delivery system to trigger anti-tumor immunity by oral route.

Recombinant Salmonella strains expressing heterologous antigens can be delivered by oral route triggering the elicitation of efficient antigen-specific humoral, T helper and cytotoxic responses. The potential of attenuated Salmonella spp. to trigger anti-tumor immunity was evaluated for the first time by using beta-galactosidase (beta-gal) as a model tumor-associated antigen (TAA). Beta-gal was expressed in a Salmonella typhimurium aroA vaccine carrier strain either constitutively or under the control of a promoter activated upon infection. Oral immunization with both vaccine prototypes resulted in the elicitation of beta-gal-specific humoral and cell-mediated immunity. Although both strains were able to trigger antigen-specific CTL, responses were more efficient when the expression was controlled by the promoter activated upon infection. The anti-tumor efficacy of the stimulated response was validated by challenging vaccinated animals with an aggressive fibrosarcoma transfected with beta-gal, which operationally acts as a TAA. Both groups of vaccinated mice exhibited a significant reduction in tumor take and growth with respect to animals vaccinated with plasmidless carrier (p < 0.05). However, the overall efficiency was better in the group in which beta-gal was controlled by the in vivo-activated promoter (85% versus 54%; p < 0.05).

Administration, Oral↗
PubMed1999

Genetically susceptible mice remain proportionally more susceptible to tuberculosis after vaccination.

DBA/2 mice are much more susceptible to infection with Mycobacterium tuberculosis than major histocompatibility complex-compatible BALB/c mice. It is shown here that, although vaccination provided mice of both strains with a capacity to reduce the level of infection in their lungs, vaccinated DBA/2 mice remained much more susceptible in this organ than vaccinated BALB/c mice. Consequently, the former mice developed more lung pathology and died much earlier than the latter. On the other hand, colony-forming unit counts and histology suggest that vaccination provided mice of both strains with an increased and equal ability to express immunity in the liver and spleen, thereby indicating that they possessed equal systemic levels of vaccine-induced immunity at the time of M. tuberculosis challenge. The results indicate that inefficient expression of immunity in the lungs is likely to prove an obstacle to successful vaccination against tuberculosis in resistant and susceptible mouse strains, but more so in the latter strains.

Animals↗
PubMed1999

Protective immune response against Streptococcus pyogenes in mice after intranasal vaccination with the fibronectin-binding protein SfbI.

Despite the significant impact on human health of Streptococcus pyogenes, an efficacious vaccine has not yet been developed. Here, the potential as a vaccine candidate of a major streptococcal adhesin, the fibronectin-binding protein SfbI, was evaluated. Intranasal immunization of mice with either SfbI alone or coupled to cholera toxin B subunit (CTB) triggered efficient SfbI-specific humoral (mainly IgG) and lung mucosal (14% of total IgA) responses. CTB-immunized control mice were not protected against challenge with S. pyogenes (90%-100% lethality), whereas SfbI-vaccinated animals showed 80% and 90% protection against homologous and heterologous challenge, respectively. Multiple areas of consolidation with diffused cellular infiltrates (macrophages and neutrophils) were observed in lungs from control mice; the histologic structure was preserved in SfbI-vaccinated animals, which occasionally presented focal infiltrates confined to the perivascular, peribronchial, and subpleural areas. These results suggest that SfbI is a promising candidate for inclusion in acellular vaccines against S. pyogenes.

Adhesins, Bacterial↗
PubMed1999

Neurally mediated syncope: pathophysiology and implications for treatment.

Neurally mediated syncope may occur in patients whose hemodynamic picture does not fit the characteristics of orthostatic intolerance as described elsewhere in this issue. Nonetheless, patients who suffer from neurocardiogenic or vasovagal syncope may be seriously incapacitated by their episodes of syncope or presyncope. Although it has been assumed that vagal activation as a result of stimulation of ventricular mechanoreceptors is essential to the production of these episodes, several critical observations are presented that suggest that other mechanisms may also be operative in some patient subsets. In addition, evidence is presented that the sympathetic responses of many of these patients may be reduced rather than increased and that abnormal baroreflex responsiveness may also play an causative role. These findings suggest new avenues for therapy in this field in which carefully controlled, randomized, double-blind trials are scarce.

Autonomic Nervous System↗
PubMed1999

Pathogenicity island 2 mutants of Salmonella typhimurium are efficient carriers for heterologous antigens and enable modulation of immune responses.

The potential use as vaccine delivery system of Salmonella typhimurium strains harboring defined mutations in the sseC (HH104) and sseD (MvP101) genes, which encode putative effector proteins of the type III secretion system of Salmonella pathogenicity island 2, was evaluated and compared with that of the well-characterized aroA mutant strain SL7207 by using beta-galactosidase (beta-Gal) as a model antigen. When orally administered to immune-competent or gamma interferon-deficient (IFN-gamma-/-) BALB/c mice, both mutants were found to be highly attenuated (50% lethal dose, >10(9) bacteria). Both strains were also able to efficiently colonize and persist in Peyer's patches. Immunization with HH104 and MvP101 triggered beta-Gal-specific serum and mucosal antibody responses equivalent to or stronger than those observed in SL7207-immunized mice. Although immunoglobulin G2 (IgG2) serum antibodies were dominant in all groups, IgG1 was also significantly increased in mice vaccinated with MvP101 and SL7207. Comparable beta-Gal-specific IgA and IgG antibodies were detected in intestinal lavages from mice immunized with the different strains. Antigen-specific CD4(+) T-helper cells were generated after vaccination with all vaccine prototypes; however, responses were significantly more efficient when HH104 and MvP101 were used (P < 0.05). Significantly higher levels of IFN-gamma were produced by restimulated spleen cells from mice immunized with HH104 than from those vaccinated with the MvP101 or SL7207 derivatives (P </= 0.05). Interestingly, the three strains induced major histocompatibility complex class I-restricted CD8(+) cytotoxic T cells against beta-Gal; however, cytotoxic T-lymphocyte responses were significantly stronger after immunization with HH104 (P < 0.05). These novel S. typhimurium attenuated strains constitute promising delivery systems for vaccine antigens. The qualitative differences observed in the obtained responses with different carriers may be useful for those applications in which a targeted immunomodulation is required.

Animals↗
PubMed1998

Gene transfer in dendritic cells, induced by oral DNA vaccination with Salmonella typhimurium, results in protective immunity against a murine fibrosarcoma.

A live attenuated AroA- auxotrophic mutant of Salmonella typhimurium (SL7207) has been used as carrier for the pCMVbeta vector that contains the beta-galactosidase (beta-gal) gene under the control of the immediate early promoter of Cytomegalovirus (CMV). We tested whether orally administered bacterial carrier could enter and deliver the transgene to antigen-presenting cells (APCs) through the natural enteric route of infection and whether beta-gal expression could generate a protective response against an aggressive murine fibrosarcoma transduced with the beta-gal gene (F1.A11) that behaves operationally as a tumor-associated antigen. After three courses, at 15-day intervals, mice developed both cell-mediated and systemic humoral responses to beta-gal. Mice vaccinated with the Salmonella harboring pCMVbeta, but not with plasmid-less carrier, showed resistance to a challenge with F1.A11 cells. These experiments suggest that Salmonella-based DNA immunization allows us to specifically target antigen expression in vivo to APCs. To prove that the transgene is actually expressed by APCs as a function of an eukaryotic promoter, the green fluorescent protein (GFP) was placed under the control of either the eukariotic CMV or a prokaryotic promoter. Using cytofluorometric analysis, GFP was detected only in splenocytes of mice receiving a Salmonella carrier harboring GFP under the CMV promoter. These results indicate that transgene expression occurs because of a Salmonella-mediated gene transfer to eukaryotic cells. Finally, approximately 19% of the splenocytes expressed GFP. Among them, F4/80(+) macrophages and CD11cbright dendritic cells (DCs) were scored as positive for GFP expression. Extensive work has been performed trying to optimize the way to transfect DCs, ex vivo, with genes coding for relevant antigens. We show here, for the first time, that DCs can be directly and specifically transduced in vivo such to induce DNA vaccination against tumors.

Administration, Oral↗
PubMed1998

Fibronectin-binding protein I of Streptococcus pyogenes is a promising adjuvant for antigens delivered by mucosal route.

A common problem in human vaccinology is the limited availability of efficient and non-toxic adjuvants capable of promoting mucosal responses. The potential usefulness of fibronectin-binding protein I (Sfbl) of Streptococcus pyogenes as immunological adjuvant was assessed using ovalbumin (OVA) as a model antigen. Mice were immunized by intranasal route, either with soluble OVA or OVA covalently coupled to Sfbl. Immunization with OVA-Sfbl resulted in the elicitation of about 100-fold higher titers of anti-OVA serum IgG than using OVA alone. The anti-OVA IgG subclass pattern was dominated in both groups of mice by IgG1, followed by IgG2b, IgG2a, and IgG3. Immunization with OVA-Sfbl also resulted in the elicitation of OVA-specific IgA in lung washes (24% of the total IgA), which was absent in mice immunized with OVA alone. Spleen cells from OVA-Sfbl-immunized mice also gave a much stronger proliferative response to restimulation with soluble OVA in vitro. Phenotypic analysis of proliferating cells showed an enrichment in CD4+ T cells, producing a pattern of cytokines (IL-4, IL-5, IL-6 and IL-10) characteristic of Th2-type cells. In contrast to immunization with soluble OVA alone, OVA-Sfbl induced the generation of CD8+ OVA-specific cytotoxic cells. These results demonstrate that Sfbl represents a promising mucosal adjuvant able to substantially improve cellular, humoral and mucosal responses when coupled to an antigen administered by intranasal route.

Adhesins, Bacterial↗
PubMed1998

Attenuated Listeria monocytogenes carrier strains can deliver an HIV-1 gp120 T helper epitope to MHC class II-restricted human CD4+ T cells.

Listeria monocytogenes is a facultative intracellular pathogen which, following uptake by macrophages, escapes from the phagosome and replicates in the cytoplasm. This property has been exploited using recombinant L. monocytogenes as a carrier for the intracytoplasmic expression of antigens when MHC class I-restricted cytotoxic T lymphocyte responses are required. Much less is known of the ability of these bacteria to trigger MHC class II-restricted responses. Here, we demonstrate that after ingestion of L. monocytogenes expressing a T helper epitope from the gp120 envelope glycoprotein of HIV, human adherent macrophages and dendritic cells can process and present the epitope to a specific CD4+ T cell line in the context of MHC class II molecules. No significant differences were observed when the attenuated strains were trapped in the phagolysosome or impaired in the capacity to spread intracellularly or from cell to cell. Similar results were obtained using carrier proteins that were either secreted, associated with the bacterial surface, or restricted to the bacterial cytoplasm. A dominant expression of the TCR Vbeta 22 gene subfamily was observed in specific T cell lines generated after stimulation with the recombinant strains or with soluble gp120. Our data show that in this in vitro system L. monocytogenes can efficiently deliver antigens to the MHC class II pathway, in addition to the well-established MHC class I pathway. The eukaryotic cell compartment in which the antigen is synthesized, and the mode of display seem to play a minor role in the overall efficiency of epitope processing and presentation.

Antigen Presentation↗
PubMed1998

How important is Nramp1 in tuberculosis?

The assumption that the antimicrobial resistance gene Nramp1 is a major determinant of resistance of mice to infection with virulent Mycobacterium tuberculosis can now be challenged on the basis of published evidence to the contrary. It is likely that, with tuberculosis, Nramp1-determined defenses are subordinate to other defenses.

Animals↗
PubMed1998

Resistance ranking of some common inbred mouse strains to Mycobacterium tuberculosis and relationship to major histocompatibility complex haplotype and Nramp1 genotype.

Six common inbred strains of mice and their F1 hybrids were examined for resistance to infection with the H37Rv strain of Mycobacterium tuberculosis. According to survival times after inoculation of 10(5) CFU intravenously (i.v.), the mice could be classified as being either highly susceptible (CBA, DBA/2, C3H, 129/SvJ) or highly resistant (BALB/c and C57BL/6). F1 hybrids of susceptible and resistant strains were resistant. Although an examination of a limited number of H-2 congenic strains showed that the H-2k haplotype could confer susceptibility on a resistant strain, it was evident that non-major histocompatibility complex (MHC) genes were much more important. Resistant strains all possessed the susceptibility allele of the anti-microbial resistance gene, Nramp1. Results obtained with selected strains infected with 10(2) CFU of M. tuberculosis by aerosol agreed with the results obtained with mice infected i.v. The size of the bacterial inoculum was important in distinguishing between resistant and susceptible strains, in that a 10(7) inoculum overcame the resistance advantage of one strain over another.

Animals↗
PubMed1998

Fibronectin-binding protein I of Streptococcus pyogenes promotes T cell-independent proliferation of murine B lymphocytes and enhances the expression of MHC class II molecules on antigen-presenting cells.

We have previously shown that fibronectin-binding protein I (SfbI) of Streptococcus pyogenes can act as an adjuvant for mucosal-delivered antigens (Medina, E., Talay, S. R., Chhatwal, G. S. and Guzmán, C. A. 1998. Eur. J. Immunol. 28:1069). To characterize the underlying mechanism of the adjuvancity, we investigated the in vitro stimulating activity of SfbI. The SfbI protein promoted a dose-dependent proliferation of mouse spleen cells. Studies performed using cellular subpopulations showed that proliferation involved B cells and was T cell- and macrophage-independent. SfbI also induced lg production by B cells in a T cell-independent manner. The kinetics of lg isotype accumulation in supernatant fluids and the analysis of Ig-secreting cells suggested that SfbI stimulates B cells expressing different Ig isotypes rather than promoting the isotype switching of single subpopulations. Experiments performed with recombinant proteins encompassing different functional domains of SfbI showed that the fibronectin-binding repeats were responsible for B cell activation. The sera from mice immunized by the intranasal route with SfbI did not react with either double-stranded DNA, cardiolipin or collagen. Interestingly, stimulation with Sfbl also resulted in the up-regulation of MHC class 11 molecules expression by B cells and macrophages. The elucidation of the underlying molecular events to the immunomodulatory effect exerted by SfbI will facilitate the exploitation of the potential of this molecule for the generation of mucosal vaccines.

Adhesins, Bacterial↗
PubMed1998

Monitoring of tacrolimus as rescue therapy in pediatric liver transplantation.

The introduction of tacrolimus as rescue therapy represents a significant advance in the prevention of late graft failure and second liver transplantation. The authors report the blood level monitoring of tacrolimus as a rescue therapy in 21 children who underwent liver transplantation, and they report the dose-concentration relationship in the presence or absence of hepatitis C virus (HCV) in these patients. This was a retrospective study conducted from May 1993 to January 1997. Indication for the conversion from cyclosporine (CsA) to tacrolimus were acute rejection (62%), chronic rejection (33%), and CsA toxicity (5%). Mean daily dose in the first month was 0.32 mg/kg, whereas at the end of the follow-up period it was 0.14 mg/kg. Tacrolimus mean whole blood concentration levels were between 7.1 ng/ml and 9.4 ng/ml, without significant differences over time. Mean daily doses in HCV+ and HCV- patients were 0.08 and 0.24 mg/kg, respectively (p < 0.01), and mean concentrations were 8.3 and 8.4 ng/ml (NS). HCV+ children required a mean dose three times lower than the dose used in HCV- children to obtain the same tacrolimus trough blood level. Therefore, doses in HCV+ children must be decreased to achieve levels within the therapeutic range.

Adolescent↗
PubMed1998

Clinical evaluation of a new 10% carbamide peroxide tooth-whitening agent.

NUPRO Gold Tooth Whitening System was evaluated for efficacy according to the proposed ADA guidelines for acceptance. Sixty participants with discolored anterior teeth participated in a 14-day, double-blind, clinical trial. The participants were matched for age, gender, and oral health status and were given either a placebo gel without the active agent or the NUPRO Gold active gel, which they wore in a custom-fabricated mouth guard for home use. The shade of each participant's maxillary anterior teeth was evaluated using a value-oriented Vita Lumin Vacuum Shade Guide before the study. The same shade guide was used to determine shade changes. Time of use of the agent and potential side effects, such as tooth and gingival hypersensitivity and tissue irritation, were assessed at all recall examinations and were recorded by participants in daily diaries. The average shade change for the placebo users was less than one shade. The average shade change for the NUPRO Gold users was 6.96 shades. Tooth hypersensitivity varied from none to severe. Tissue irritation was minimal. The results of these evaluations indicate that NUPRO Gold is effective as a tooth-whitening system, when administered properly under the supervision of a dentist, with commonly reported side effects of transient tooth sensitivity and minimal gingival sensitivity. Little or no change in tissue health was noted. This study was supported by Dentsply Preventive Care (York, Pennsylvania).

Adolescent↗