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Biomedical subjects

L Polonelli

Publications and source records attributed to L Polonelli.

At least 37 records · Page 2Linked to original sources
PubMed2000

In vitro activity of monoclonal and recombinant yeast killer toxin-like antibodies against antibiotic-resistant gram-positive cocci.

BACKGROUND: Monoclonal (mAbKT) and recombinant single-chain (scFvKT) anti-idiotypic antibodies were produced to represent the internal image of a yeast killer toxin (KT) characterized by a wide spectrum of antimicrobial activity, including gram-positive cocci. Pathogenic eukaryotic and prokaryotic microorganisms, such as Candida albicans, Pneumocystis carinii, and a multidrug-resistant strain of Mycobacterium tuberculosis, presenting specific, although yet undefined, KT-cell wall receptors (KTR), have proven to be killed in vitro by mAbKT and scFvKT. mAbKT and scFvKT exert a therapeutic effect in vivo in experimental models of candidiasis and pneumocystosis by mimicking the functional activity of protective antibodies naturally produced in humans against KTR of infecting microorganisms. The swelling tide of concern over increasing bacterial resistance to antibiotic drugs gives the impetus to develop new therapeutic compounds against microbial threat. Thus, the in vitro bactericidal activity of mAbKT and scFvKT against gram-positive, drug-resistant cocci of major epidemiological interest was investigated. MATERIALS AND METHODS: mAbKT and scFvKT generated by hybridoma and DNA recombinant technology from the spleen lymphocytes of mice immunized with a KT-neutralizing monoclonal antibody (mAb KT4) were used in a conventional colony forming unit (CFU) assay to determine, from a qualitative point of view, their bactericidal activity against Staphylococcus aureus, S. haemolyticus, Enterococcus faecalis, E. faecium, and Streptococcus pneumoniae strains. These bacterial strains are characterized by different patterns of resistance to antibiotics, including methicillin, vancomycin, and penicillin. RESULTS: According to the experimental conditions adopted, no bacterial isolate proved to be resistant to the activity of mAbKT and scFvKT. CONCLUSIONS: scFvKT exerted a microbicidal activity against multidrug resistant bacteria, which may represent the basis for the drug modeling of new antibiotics with broad antibacterial spectra to tackle the emergence of microbial resistance.

Animals↗
PubMed2000

The efficacy of acquired humoral and cellular immunity in the prevention and therapy of experimental fungal infections.

In the past two decades, numerous studies have documented the importance of acquired immunity for host defense against invasive fungal infections. There is widespread consensus in the field of medical mycology that cellular immunity is critical for successful host defense against fungi. However, in recent years several studies have established the potential efficacy of humoral immunity in host protection against two major fungal pathogens: Candida albicans and Cryptococcus neoformans. For C. albicans, antibodies to mannan, proteases and a heat shock proteins have been associated with protection against infection. Furthermore, anti-idiotypic antibodies to antibodies recognizing killer toxin from Pichia anomala and mimicking natural anti-killer toxin receptor antibodies can protect against C. albicans and other microorganisms. For C. neoformans, antibodies to the capsular glucuronoxylomannan have been shown to mediate protection in animal models of infection. Vaccines that induce protective antibodies have been shown to protect against experimental C. albicans and C. neoformans infection. In contrast, humoral immunity has not yet been demonstrated to mediate protection against Coccidioides immitis. For C. immitis, protection against infection is thought to rely on T cell mediated immunity, and the emphasis is on identifying the antigens that stimulate protective cellular immune responses and several candidate vaccines have been identified. These results provide encouragement for the view that acquired immune responses can be mobilized for the prevention and treatment of fungal infections.

Animals↗
PubMed1999

Tetanus toxin impairs accessory and secretory functions in interferon-gamma-treated murine macrophages.

Tetanus neurotoxin (TT), a product of microbial origin, acts as a zinc endopeptidase on vesicle-associated membrane proteins (VAMP). We have demonstrated that TT displays inhibitory effects on secretory and accessory functions in the murine macrophage (Mphi) cell line GG2EE. Nitric oxide (NO) secretion was decreased when interferon (IFN)-gamma-pretreated GG2EE Mphis were coincubated with a fungal costimulus (SMP200) and TT. When heat-inactivated TT was used this effect was not evident. The TT-mediated phenomenon was dose-dependent and specific since, under the same experimental conditions, it did not affect interleukin-6 or tumor necrosis factor-alpha secretion. Furthermore, IFN-gamma-induced major histocompatibility complex class II molecule expression and GG2EE accessory function, assessed by SMP200-stimulated lymphoproliferation, were also inhibited by TT. Such inhibition was incomplete, in line with our previous results showing that TT partially cleaves VAMP proteins in murine Mφ.

Animals↗
PubMed1999

Novel strategies for treating candidiasis.

In this review the recent achievements in the field of chemotherapy and immunotherapy of candidiasis are outlined. The current limitations of chemotherapeutic approaches and the lack of well defined preventive tools and strategies make it imperative to exploit the potential of novel immunotherapeutic venues. In this prospect the rather extensive work performed on cytokine patterns in experimental models and the upsurge of antibodies as one mechanism of anti-Candida protection raises great promise for the clinical use of immunotherapy possibly in conjunction with chemotherapy to improve the fight against this increasingly prevalent human opportunistic infection.

Journal Article↗
PubMed1998

Factors influencing the expression in vitro of Candida albicans stress mannoproteins reactive with salivary secretory IgA.

We have examined the influence of subinhibitory concentrations of several antifungals, the different glucose and ammonium sulphate concentrations in the culture medium as well as the strain variability on the expression in vitro of stress mannoproteins reactive with salivary sIgA in C. albicans and other Candida spp isolates. Irrespective of the conditions used, no reactivity with salivary sIgA was observed in yeast cells grown at 25 degrees C. However, when grown at 37 degrees C, all of the 10 C. albicans strains, but only 9 out of 28 non-C. albicans isolates studied showed reactivity with salivary sIgA. Cells grown at 37 degrees C in medium containing maximum concentrations of glucose and ammonium sulphate expressed the antigens reactive with sIgA during longer periods of time than the cells grown in medium with minimal concentrations of the same compounds. The regulatory role showed by the concentration of glucose and ammonium sulphate on the antigenic expression was subordinated, nevertheless, to the most important factor, the temperature of incubation. Only isolates showing low susceptibility expressed the antigens reactive with sIgA under the influence of subinhibitory concentration of antifungals. However, induced resistance to one of the antifungals tested (5 fluorocytosine) allowed the antigenic expression at elevated subinhibitory concentrations even in previous susceptible strains. In conclusion, in addition to the temperature, factors such as characteristics of the strain, the concentration of glucose and ammonium sulphate in the culture medium and the resistance to antifungals played a role on the expression of C. albicans antigens reactive with sIgA, which could be of clinical relevance in the course of infection.

Antifungal Agents↗
PubMed1998

Neonatal mouse immunity against group B streptococcal infection by maternal vaccination with recombinant anti-idiotypes.

We investigated whether immunization with recombinant anti-idiotypic antibody fragments mimicking the conformation of the capsular antigen can protect against infection by group B streptococcus, an important neonatal pathogen. Single-chain fragment-variable anti-idiotypes competed with the type III carbohydrate for binding to type-specific antibodies and elicited, in mice, the production of protective immunoglobulins reacting against the type III polysaccharide. Moreover, maternal immunization with soluble or phage-displayed fragments protected neonatal mice against streptococcal infection. These data indicate that recombinant anti-idiotypic antibodies may be useful in developing protein images of relevant carbohydrate epitopes and, ultimately, in preventing infections by encapsulated bacteria.

Agglutination↗
PubMed1998

Mycobactericidal activity of human natural, monoclonal, and recombinant yeast killer toxin-like antibodies.

Human natural (KTAb), murine monoclonal (KTMAb), and single-chain recombinant (KTScFv) candidacidal antibodies representing the internal image of a killer toxin from the yeast Pichia anomala (KT), characterized by a wide spectrum of antibiotic activity, exerted a lethal effect against a KT-sensitive multidrug-resistant isolate of Mycobacterium tuberculosis. KTMAb and KTScFv were produced by the hybridoma and DNA technologies, respectively, from the spleen lymphocytes of animals immunized with the idiotype of a KT-neutralizing MAb (MAb KT4), while KTAb were purified against MAb KT4 from the vaginal fluid of women infected with Candida albicans cells bearing an idiotype-like KT cell wall receptor. Mycobactericidal activity was related to the binding of KTAb, KTMAb, and KTScFv to the cell surface of KT-sensitive bacterial cells and was prevented by specific absorption of KT-like antibodies onto MAb KT4. These data identify a novel potentially useful immunotherapeutic approach to tuberculosis.

Antibodies, Anti-Idiotypic↗
PubMed1998

Effect of a killer toxin of Pichia anomala to Pneumocystis. Perspectives in the control of pneumocystosis.

Despite the development of drugs in the prophylaxis of pneumocystosis, Pneumocystis carinii remains a major opportunistic microorganism in immunosuppressed individuals, especially in human immunodeficiency virus-infected patients. Since side effects were frequently observed after administration of trimethoprim-sulfamethoxazole or pentamidine, the drugs which are mainly used in treating human P. carinii pneumonia (PCP), new therapeutic strategies should be developed. Over the last years, the inhibitory effect of a Pichia anomala killer toxin (PaKT), a molecule with a wide spectrum of antimicrobial activity, was characterized on P. carinii. The susceptibility of mouse and rat-derived Pneumocystis to PaKT has been demonstrated by in vitro attachment tests and in vivo infectivity assays. Nevertheless, PaKT is strongly antigenic, toxic and could not be used directly as a therapeutic agent. Then, a new strategy using killer toxin-like anti-idiotypic antibodies (KT-antiIds) mimicking the fungal toxin activity has been developed. Different KT-antiIds were obtained by idiotypic immunization with a monoclonal antibody (mabKT4). This mabKT4 neutralized the killer properties of the PaKT. KT-antiIds were produced by immunization against the variable domain (idiotype) of mAbKT4 (internal image of the killer toxin receptor), or they were obtained directly from vaginal fluid of patients affected by recurrent vaginal candidiosis. In this last case, such natural KT-antiIds were immunopurified by affinity-chromatography with mAbKT4 and their anti-P. carinii activity was then evaluated. Our results showed that both the in vitro attachment of rat-derived parasites and their infectivity to nude rats were inhibited by the KT-antiIds. With regard to KT-antiIds obtained by immunization, the antimicrobial activity of a monoclonal KT-antiIds (mAbK10) has been evaluated by using a PCP experimental nude rat model treated by mAbK10 administered by aerosol. The pneumocystosis extension was significantly reduced in this model. The monoclonal KT-antiIds were effective against P. carinii in reducing parasite proliferation in lungs of nude rats. Further experiments are in progress to study the in vivo anti-P. carinii activity of KT-antiIds by using recombinant single-chain of the variable fragment of KT-antiIds. Yeast killer toxin-like recombinant molecules could provide the basis for a new therapeutic strategy towards the control of pneumocystosis.

Animals↗
PubMed1998

A transphyletic anti-infectious control strategy based on the killer phenomenon.

A strategy for the prevention and control of candidiasis, pneumocystosis, and tuberculosis, based on the idiotypic network of the yeast killer effect has been envisaged. Anti-idiotypic antibodies representing the internal image of a candidacidal, pneumocysticidal, and mycobactericidal killer toxin from Pichia anomala and idiotypes of killer toxin-neutralizing monoclonal antibodies mimicking the specific cell wall receptor of sensitive microorganisms might provide a unique approach for engineering innovative antibiotics and vaccines active against taxonomically unrelated pathogenic microorganisms. The rationale of the strategy relies on a phenomenon of microbial competition which has been mutated by the immune system in the response to natural infections.

Animals↗
PubMed1998

Evaluation of the Abbott LCx Mycobacterium tuberculosis assay in comparison with culture methods in selected Italian patients.

A ligase chain reaction (LCR) DNA amplification method for the molecular diagnosis of Mycobacterium tuberculosis (Abbott LCx MTB) was evaluated in comparison with solid and liquid phase culture on 622 selected samples collected in two large Italian hospitals, of which 310 obtained from HIV-1 positive patients and 312 from HIV-negative individuals. The overall prevalence of mycobacteria by culture was 22% (137/622), and the apparent sensitivity and specificity of LCx vs. culture were 87.6% and 98.2%. Of the 26 culture positive/LCx negative samples, 22 were positive for MOTT and 4 for M. tuberculosis. All 9 samples positive by LCx and negative by culture were classified as true positive by clinical criteria. The final values of sensitivity, specificity, positive predictive value and negative predictive value for LCx rose to 96.8%, 100%, 100% and 99.2%, respectively. The adjusted sensitivity of culture methods was 89.5% for solid phase and 92.7% for Bactec. In view of the high sensitivity on both smear-positive (100%) and smear-negative (92.4%) samples and of the high negative predictive value, the LCR-based amplification method appears suitable as a routine screening method for the rapid diagnosis of M. tuberculosis in high-risk patients.

DNA, Bacterial↗
PubMed1998

Effect of Pichia anomala killer toxin on Candida albicans.

The effect of a Pichia anomala killer toxin upon a Candida albicans-sensitive strain was studied. Yeast and hyphae, after treatment with the toxin, were less capable of uptaking either [3H]-uridine or [35S]-methionine. In addition, the hyphal form of the fungus appeared to be less capable of DNA synthesis after toxin treatment. No effect of the killer toxin was shown upon a natural resistant mutant of the source strain. These data suggest that, similar to other killer yeast toxins, the toxin of P. anomala can produce a number of quantifiable effects upon sensitive C. albicans cells.

Candida albicans↗
PubMed1998

Stress proteins in fungal diseases.

Heat shock proteins (hsps) are ubiquitous families of proteins, found in all organisms studied so far. They are highly conserved across the species barrier and serve fundamental functions in cell physiology. The term 'heat shock' was adopted because of the early observation of the heat-inducible nature of these proteins, although, as it is now realized that they can be induced by a variety of stressful stimuli, it is probably more appropriate to call them 'stress proteins'. The nomenclature of many hsps, for example hsp90, hsp70 and hsp60, reflects the approximate molecular mass of hsps within each of these families. For many bacterial and parasitic infections, hsps were first recognized as immunodominant antigens on immunoblots of extracts from the organism probed with immune sera, or in T-cell proliferation assays. They have now been identified in a range of fungal pathogens, again often linked to an immune response. In this symposium, we review the association of hsps with humoral immunity to candidosis and aspergillosis, cellular immunity to histoplasmosis, and the identification of hsp70 in another dimorphic fungus, Paracoccidioides brasiliensis. Finally, the crucial role of the membrane in setting the temperature of the heat shock response in yeasts is discussed.

Animals↗
PubMed1998

Antibody and/or cell-mediated immunity, protective mechanisms in fungal disease: an ongoing dilemma or an unnecessary dispute?

Historically there has been controversy on the relative importance of antibody- and cell-mediated immune responses in the protection against fungal pathogens. The controversy was fuelled by the difficulties encountered in obtaining consistent results with polyclonal antibody experiments and I inducing long-lasting immune protection by vaccinations with induce stron cell-mediated responses. Recent studies indicate that both antibody- and cell-mediated immune responses can contribute to host protection against Candida albicans and C. neoformans. At the present time the major issue is not the relative importance of antibody- and cell-mediated immune responses but rather, the mechanisms by which the two arms of the immune system function and cooperate.

Animals↗
PubMed1997

Therapeutic potential of antiidiotypic single chain antibodies with yeast killer toxin activity.

Single chain fragment (ScFv) antiidiotypic antibodies (antilds) of a killer toxin (KT) from the yeast Pichia anomala have been produced by recombinant DNA methodology from the splenic lymphocytes of mice immunized by idiotypic vaccination with a KT-neutralizing monoclonal antibody (Mab KT4). ScFv KT-like antilds (KTIdAb) react with specific Candida albicans KT cell wall receptors (KTR) exerting a candidacidal activity in vitro could be neutralized by adsorption with Mab KT4. ScFv KTIdAb displayed an effective therapeutic activity in an experimental model of rat candidal vaginitis.

Animals↗
PubMed1997

Monoclonal yeast killer toxin-like candidacidal anti-idiotypic antibodies.

Rat monoclonal yeast killer toxin (KT)-like immunoglobulin M (IgM) anti-idiotypic antibodies (KT-IdAbs) were produced by idiotypic vaccination with a mouse monoclonal antibody (MAb; MAb KT4) that neutralized a Pichia anomala KT characterized by a wide spectrum of antimicrobial activity. The characteristics of the KT-IdAbs were demonstrated by their capacity to compete with the KT to the idiotype of MAb KT4 and to interact with putative KT cell wall receptors (KTRs) of sensitive Candida albicans cells. The internal-image properties of KT-IdAbs were proven by their killer activity against KT-sensitive yeasts. This lethal effect was abolished by prior adsorption of KT-IdAbs with MAb KT4. These findings stressed the potential importance of antibody-mediated immunoprotection against candidiasis and suggested a feasible experimental approach for producing antimicrobial receptor antibodies without purifying the receptor. KT-IdAbs might represent the basis for producing engineered derivatives with a high potential for effective therapeutic antifungal activity.

Animals↗
PubMed1997

Yeast killer systems.

The killer phenomenon in yeasts has been revealed to be a multicentric model for molecular biologists, virologists, phytopathologists, epidemiologists, industrial and medical microbiologists, mycologists, and pharmacologists. The surprisingly widespread occurrence of the killer phenomenon among taxonomically unrelated microorganisms, including prokaryotic and eukaryotic pathogens, has engendered a new interest in its biological significance as well as its theoretical and practical applications. The search for therapeutic opportunities by using yeast killer systems has conceptually opened new avenues for the prevention and control of life-threatening fungal diseases through the idiotypic network that is apparently exploited by the immune system in the course of natural infections. In this review, the biology, ecology, epidemiology, therapeutics, serology, and idiotypy of yeast killer systems are discussed.

Antibodies, Monoclonal↗