Susceptibilities of rickettsiae to antimicrobials.
BENABDELLAH A, BENSSADOUN F-Z, BENSSAD M, KOUIDAD-BELKADI S-A
Service des maladies infectieuses et tropicales, CHU.Oran, Oran 31000, Algeria
Abstract:
Rickettsiae grow only intracellularly. The antibiotic susceptibility is assessed by plaque,dye uptake or IF assays. Rickettsiae are susceptible to doxycycline, thiamphenicol and fluroquinolones. Betalactams, aminoglycosides and cotrimoxazole are not active. Typhus group rickettsiae are susceptible to all macrolides,whereas the spotted fever are more resistant to rifampicin than the other rickettsiae. Rickettsiae felis is not susceptible to gentamicin, erythromycine, amoxicilline or cotrimoxazole. we present an overview of susceptibility of rickettsiae to antimicrobials.
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Immunogenicity of Biopharmaceuticals - An Inconvenient Truth.
BENDTZEN K
Institute for Inflammation Research, Rigshospitalet, and BioMonitor Ltd., Copenhagen, Denmark.
Background: Today, recombinant gene technology permits the use of drugs which are almost identical with natural human proteins, including antibodies (Abs). Many assume that these drugs pose little or no risk of triggering specific immune responses, because patients according to dogma are tolerant towards their own proteins. Unfortunately, this is not the case, and even so-called 100% human biologicals may be immunogenic. I shall focus on the immunogenicity of anti-TNF Ab constructs plus the largely ignored problem of individual variations in drug bioavailability (BA) and pharmacokinetics (PK).
Methods: Several methods have been used to assess circulating levels of anti-TNF biologicals as well as Abs to these drugs. Most are based on solid-phase technology, e.g. ELISA, with their inherent problems of low sensitivity, false positivity and susceptibility to nonspecific interference, fx by rheumatoid factors. We have developed fluid-phase radioimmunoassays (RIAs) for monitoring patients on anti-TNF biologicals, one for functional blood levels of the drugs, and one for anti-drug Abs.
Results: We measured BA/PK and anti-drug Abs developed in 'anti-TNF-immunized' patients with rheumatoid arthritis; most of these were treated with infliximab. The most sensitive anti-drug Ab assay involved binding to soluble and intact infliximab rather than to plastic-immobilized drug. Indeed, data obtained by solid-phase assay using cross-binding of plastic-fixed and soluble infliximab were inconsistent with results obtained with fluid-phase RIA. Despite intravenous administration, there were sizable interindividual variations in serum trough levels of the drugs even at time-points where anti-drug Abs had not yet developed; these levels diminished or disappeared in parallel with Ab induction (30% and 44% of patients on infliximab were Ab-positive at 3 and 6 months, respectively). Abs were 'neutralizing' in that their levels were positively associated with inhibition of TNF binding to the drugs. There were highly significant correlations between high levels of anti-drug Abs and later dose increases, side-effects and cessation of therapy.
Conclusions: To prevent prolonged use of inadequate anti-TNF biotherapies, individualized assessments of BA/PK and Abs seem essential (personalized medicine). In our hands, fluid-phase assays are superior to solid-phase assays.
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The Path from Colles’ Law to the “Magic Bullet”
BENEDEK TG
University of Pittsburgh, Pittsburgh, Pennsylvania
The hypothesis that syphilis might be counteracted immunologically can be traced to the Irish surgeon, Abraham Colles, who noted in 1837 that a congenitally syphilitic infant may be born of a mother who showed no signs of syphilis. He interpreted this to indicate that the infant, infected by a diseased fertilizing sperm, immunizes its mother against syphilis, even though it can infect other caretakers. This talk will sketch the disappointing investigations that led from “Colles’ law” to the reception of Ehrlich’s “magic bullet.”
The first line of serologic investigation, initiated by Joseph Auziaz-Turenne in the 1840s was called “syphilization.” In this controversial therapy the patient was “saturated” over several months with hundreds of subcutaneous injections of “syphilitic toxin,” based on the hypothesis that when saturation was reached new manifestations of the disease were prevented, after which cure might be achieved. Saturation had been achieved when injections no longer elicited a local inflammatory reaction. Syphilis and chancroid had not been differentiated at this time. Thus the misinterpretation of “saturation” of syphilitic patients was frequently compounded by the injection of chancroidal rather than syphilitic serum. Most responsible for perpetuating this technique until about 1870 was the Norwegian venereologist, Caesar Boeck.
With the advent of bacteriology it became of interest why certain species were resistant to a pathogen that was lethal to another. Could this “resistance factor” be transferred, either as prophylaxis or therapy? The first injections of serum from animals that could not be made syphilitic were undertaken in 1890 on patients with secondary syphilis and were recognized to be ineffective. Further trials were stimulated by favorable reports by an Italian venereologist who in 1892 gave subcutaneous injections of lambs’ blood. Various investigators used serum from dogs, rabbits, sheep, and horses. When the use of serum from untreated animals became recognized as useless, donor animals were pre-treated with syphilitic “toxin” or mercury. The greatest stimulus to experimentation with serum therapy came in 1893 with the announcement of successful serum treatment of diphtheria and tetanus. The lack of a proven pathogen of syphilis added confusion to the search for an anti-syphilitic serum.
The immediate acceptance of the discovery in 1905 of the Spirochaeta pallida as the pathogen, rapidly followed by discovery of a practical diagnostic method, may explain why, in the midst of the belief that a curative serum for all microbial diseases was about to be discovered, Ehrlich’s announcement in 1910 of the therapeutic efficacy of medicinal “Salvarsan” was received so enthusiastically. Ehrlich was more circumspect regarding the usefulness of Salvarsan than many of its early advocates.
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Water Channel Proteins (Aquaporins): From their Discovery in 1985 in Cluj-Napoca, Romania (By the use of a Doping Nmr Method and Specific Labeling) to the use of their Inhibitors as Magic Bullets
BENGA G
Dept. of Cell and Molecular Biology, "Iuliu Hatieganu" University of Medicine and Pharmacy, Cluj-Napoca, Romania
Water channels or water channel proteins (WCPs) are transmembrane proteins that have a specific three-dimensional structure with a pore that can be permeated by water molecules. The first WCP was discovered in the human red blood cell membrane in Cluj-Napoca, Romania, in 1985 by Benga’s group. We have measured the water permeability of human red blood cells (RBCs) by a doping NMR method. We showed for the first time by NMR that the parameters characterizing diffusional water permeability are the same in RBCs and resealed ghosts and reported the largest series of determinations of water diffusional permeability of RBCs available in literature.
The first water channel protein (WCP), later called aquaporin 1 (AQP1) was discovered in the RBC membrane by my group in 1985 in Cluj-Napoca, Romania, reported in publications in 1986 (Benga et al., Biochemistry, 25, 1535-1538, 1986; Benga et al., Eur. J. Cell Biol., 41, 252-262, 1986) and reviewed in the following years. This discovery was achieved by specific labelling of the RBC membranes with the known water transport inhibitor 203Hg - p-chloromercuribenzenesulfonate (PCMBS). In parallel, the water permeability was measured by the doping NMR technique and the inhibition induced by PCMBS was calculated. The priority of Benga in the discovery of the first WCP was acknowledged by many outstanding scientists.
We also have a world priority in the discovery of the implications of water channel proteins in epilepsy (Benga and Morariu, Nature, 265, 636-638, 1977) and Duchenne muscular dystrophy (Serbu et al., Muscle & Nerve, 9, 243-247, 1986). These findings were interpreted as an expression of generalized membrane defects affecting water permeability in epilepsy and Duchenne muscular dystrophy. In recent years this idea was confirmed.
Since the discovery of WCPs tremendous progress in understanding their role in physiology and pathology. Based on these advances it became clear that inhbitors of AQPs can be used as magic bullets in a variety of diseases, including cancer. The doping NMR method should be used to compare the effects of inhibitors of WCPs as magic bullets. Examples of this approach will be given.
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