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J Kovarik

Publications and source records attributed to J Kovarik.

At least 19 recordsLinked to original sources
PubMed1999

CpG oligodeoxynucleotides can circumvent the Th2 polarization of neonatal responses to vaccines but may fail to fully redirect Th2 responses established by neonatal priming.

Neonatal murine responses to a panel of conventional vaccines differ qualitatively from adult responses by a particular polarization toward a Th2 pattern and a frequent limitation of the Th1 and CTL responses required for protection against intracellular microorganisms. In contrast, DNA vaccines induce adult-like Th1/CTL neonatal responses against the same vaccine Ags. In this report, we show that this can be related to their content in unmethylated CpG motifs. Oligodeoxynucleotides (ODN) containing CpG motifs activate neonatal APCs to produce IL-12 in vitro and induce adult-like Th1 responses to tetanus toxoid and measles Ags in vivo, with production of IgG2a-specific Abs and adult-like secretion of IFN-gamma and IL-5 by Ag-specific T cells. However, in spite of their capacity to trigger neonatal B cell proliferation in vitro, CpG-ODN only partially enhanced early life Ab responses. Finally, using Th1-driving CpG-ODN with the boosting dose of a protein vaccine was sufficient to redirect adult but not neonatally primed Th2 responses. These observations could be important for the development of novel vaccines that will have to be effective early in life.

Animals↗
PubMed1998

Chronic gastrointestinal symptoms in hemodialysis patients.

INTRODUCTION: Gastrointestinal disorders occur frequently in dialysis patients. Few data are available on the prevalence of symptoms originating from the gastrointestinal tract in this group of patients. Our aim was to obtain data on the prevalence of chronic gastrointestinal symptoms in patients undergoing hemodialysis. METHODS: All 109 patients of our dialysis unit were given a questionnaire to complete which was previously validated and designed to measure the occurrence of gastrointestinal, and some general symptoms during the preceding year. 105 subjects responded (96% response rate). RESULTS: 79% of dialysis patients had at least one of the following chronic gastrointestinal symptoms: Esophageal symptoms were reported in 21% abdominal pain in 28% and dyspeptic symptoms in 48%. The irritable bowel syndrome was diagnosed in 12 patients (11%), 40% had chronic constipation and 24% had chronic diarrhoea. Colonic pain was described in 20% of patients. Frequent general symptoms (such as weakness, headaches, insomnia and fatigue) were described in up to 51%, and patients were severely bothered by symptoms in up to 33% of cases. CONCLUSION: Although patients on hemodialysis generally report a good quality of life, the prevalence of gastrointestinal symptoms and of general symptoms is high and many dialysis patients consider these symptoms to cause major impairment of daily life.

Adult↗
PubMed1998

Influence of maternal antibodies on vaccine responses: inhibition of antibody but not T cell responses allows successful early prime-boost strategies in mice.

The transfer of maternal antibodies to the offspring and their inhibitory effects on active infant immunization is an important factor hampering the use of certain vaccines, such as measles or respiratory syncytial virus vaccine, in early infancy. The resulting delay in protection by conventional or novel vaccines may have significant public health consequences. To define immunization approaches which may circumvent this phenomenon, experiments were set up to further elucidate its immunological bases. The influence of maternal antibodies on antibody and T cell responses to measles hemagglutinin (MV-HA) were analyzed following MV-HA immunization of pups born to immune or control BALB/c mothers using four different antigen delivery systems: live or inactivated conventional measles vaccine, a live recombinant canarypox vector and a DNA vaccine. High levels (> 5 log10) of maternal anti-HA antibodies totally inhibited antibody responses to each of the vaccine constructs, whereas normal antibody responses were elicited in presence of lower titers of maternal antibodies. However, even high titers of maternal antibodies affected neither the induction of vaccine-specific Th1/Th2 responses, as assessed by proliferation and levels of IFN-gamma and IL-5 production, nor CTL responses in infant mice. On the basis of these unaltered T cell responses, very early priming and boosting (at 1 and 3 weeks of age, respectively) with live measles vaccine allowed to circumvent maternal antibody inhibition of antibody responses in pups of immune mothers. This was confirmed in another immunization model (tetanus toxoid). It suggests that effective vaccine responses may be obtained earlier in presence of maternal antibodies through the use of appropriate immunization strategies using conventional or novel vaccines for early priming.

Animals↗
PubMed1998

Conservative treatment of anorectal tumors.

PURPOSE: To evaluate the results of interstitial radiotherapy of anorectal tumors. PATIENTS AND METHODS: From 1972 to 1993, one of the authors treated 45 patients by an interstitial implant for anorectal tumors. Of these, 33 patients suffered from primary tumors, 19 from squamous carcinoma, 2 from basaloid carcinoma of the anus and the other 12 from primary adenocarcinoma of the rectum. Of 12 patients treated for local recurrence, 10 had adenocarcinoma and 2 squamous cell carcinoma. Of the 33 patients with primary tumors, 27 received a course of external-beam radiotherapy before the implant. The median follow-up was 35 months. RESULTS: Local response depended on the tumor volume treated. All 21 anal tumors showed complete response, 5 patients developed local recurrence and 4 distant metastases: 3 died from their disease. Of 12 rectal adenocarcinomas, 9 responded completely, 4 patients developed local recurrence and 4 distant metastases; 6 died from active disease. In the last group of 12 patients who were treated for recurrent tumors, 7 responded completely. One patient developed local recurrence and 9 distant metastases, only 4 are alive. CONCLUSIONS: A combination of external-beam and interstitial radiotherapy is a relatively simple, non-mutilating, but well-tolerated and very effective method of treatment for early carcinoma of the lower rectum and anus.

Adenocarcinoma↗
PubMed1998

Disposition and immunodynamics of basiliximab in liver allograft recipients.

A randomized, open-label prospective study was conducted with recipients of primary cadaveric liver allografts to characterize the disposition and immunodynamics of basiliximab, an interleukin-2 receptor, alpha-chain chimeric monoclonal antibody for immunoprophylaxis of acute rejection. Patients received a total intravenous dose of 40 mg basiliximab in addition to baseline dual immunosuppression consisting of cyclosporine (INN, ciclosporin) and steroids. The central distribution volume was 5.6 +/- 1.7 L with a steady-state volume of 7.5 +/- 2.5 L. It was cleared slowly with a total body clearance of 75 +/- 24 ml/hr and an elimination half-life of 4.1 +/- 2.1 days. Basiliximab was measurable in drained ascites fluid, and clearance by this route was an average of 20% of total clearance. Total body clearance correlated positively with volume of postoperative blood loss (r = 0.5253, p = 0.0101), suggesting that bleeding may represent an additional route of drug removal. A threshold relation was observed between serum concentration of basiliximab and CD25 expression on T lymphocytes whereby complete saturation of interleukin-2 receptor alpha-chain was maintained as long as serum concentrations exceeded 0.1 microgram/ml. The duration of receptor saturation was 23 +/- 7 days after transplantation (range, 13 to 41 days).

Adolescent↗
PubMed1998

Operations on the thoracic aorta and hypothermic circulatory arrest: is aprotinin safe?

INTRODUCTION: The safety of aprotinin, especially when used with profound hypothermic circulatory arrest, is still a matter of intense debate despite its presumed salutary effects on blood loss. Many investigators have reported toxic renal effects of high-dose aprotinin in such patients, but no prospective, randomized study has been conducted. To assess the potential detrimental effect of aprotinin on renal function and its putative reduction of blood loss, 50 patients undergoing thoracic aortic operations with the use of profound hypothermic circulatory arrest were randomly assigned to receive either low-dose aprotinin (1 x 10(6) kallikrein activation units) or placebo. METHODS: The specific renal tubular markers beta-2-microglobulin and beta-N-acetyl-D-glucosaminidase, as well as serum creatinine and blood urea nitrogen, creatinine clearance, sodium excretion, and potassium excretion, were measured to evaluate renal function preoperatively, immediately after the procedure, and 24 hours and 48 hours later. RESULTS: No statistically significant difference was found in any measured renal parameter between the two groups (analysis of variance). Renal dysfunction, defined as an elevation of serum creatinine early postoperatively (> or = 1.5 times the preoperative value), occurred in two patients who received aprotinin and in one patient in the control group. Temporary dialysis (hemodialysis or continuous venovenous hemofiltration) was needed in two patients in the aprotinin group versus one in the control group. Furthermore, patients treated with aprotinin had significantly less total postoperative blood loss (718 +/- 340 ml vs 920 +/- 387 ml, p = 0.04). The aprotinin recipients also had a significantly lower transfusion requirement (p < 0.05). CONCLUSION: This controlled trial of low-dose aprotinin in patients undergoing thoracic aortic operations using profound hypothermic circulatory arrest demonstrated no detectable deleterious effects on renal function; moreover, the use of aprotinin was associated with significantly lower need for transfusion.

Aged↗
PubMed1998

Ofloxacin clearance during hemodialysis: a comparison of polysulfone and cellulose acetate hemodialyzers.

The pharmacokinetics of ofloxacin were studied in 13 patients with end-stage renal disease during hemodialysis using two different dialyzers: a polysulfone membrane (Fresenius F6) and a cellulose acetate dialyzer (Nissho Nipro FB-150T). All patients received 100 mg ofloxacin orally per day before dialysis. The hemodialysis clearance per square meter surface area was significantly different, with 5.0+/-0.7 L/h and 3.7+/-1.6 L/h, respectively. The serum concentration was reduced by a 3-hour hemodialysis by 49.6%+/-5.8% per square meter surface area and 45.5%+/-4.8% per square meter surface area. The half-life was 4.2+/-1.8 hours and 4.8+/-1.6 hours during the hemodialysis period and 22.8+/-2.2 hours and 23.3+/-1.7 hours between the dialysis sessions, respectively. Comparing polysulfone and cellulose acetate dialyzers, the material of the membrane influences the half-life, the dialysis clearance, and the percentage of drug extracted during hemodialysis. We conclude that the type of dialyzer used has to be taken into account in dosage recommendations for antimicrobial therapy in hemodialysis patients.

Adult↗
PubMed1998

Optimization of vaccine responses in early life: the role of delivery systems and immunomodulators.

Infant immunization is a particularly important field with multiple challenges for vaccine research and development. There is, together with a high susceptibility to infections, a lower efficacy of most vaccinations in newborns and young infants, compared to those performed later in life. In the present review, the authors focus on problems arising from the attempt to vaccinate against pathogens very early in life, and on the role of selective adjuvants (i.e. antigen delivery systems or immunomodulators) that could be used to: (i) rapidly induce strong antibody responses of the appropriate isotypes; (ii) elicit sustained antibody responses extending beyond infancy; (iii) induce efficient Th1 and CTL responses in spite of the preferential Th2 polarization of early life responses; (iv) escape from maternal antibody mediated inhibition of vaccine responses; (v) show acceptable reactogenicity in early life; and (vi) allow incorporation of several vaccine antigens into a single formulation so as to reduce the number of required injections. How such objectives might be achieved by several of the vaccine formulations currently in development is illustrated by reviewing data from experimental models and clinical studies, when available.

Adjuvants, Immunologic↗
PubMed1998

Cyclophosphamide, but not CTLA4Ig, prolongs survival of fetal pig islet grafts in anti-T cell monoclonal antibody-treated NOD mice.

Fetal pig islets, xenografted after organ culture into non-immunosuppressed prediabetic NOD mice, are rejected within 10 days. Immunosuppression with anti-T cell (anti-CD4 and anti-CD3) monoclonal antibodies alone is highly effective in delaying graft rejection in this discordant model, but rejection eventually occurs, usually within 80 days, despite marked depletion of T cells. In an attempt to prevent rejection, we used cyclophosphamide (CP), a powerful anti-B cell agent, or CTLA4Ig, an inhibitor of T-cell co-stimulation [via B7-1 (CD80) and B7-2 (CD86)], either given in combination with anti-CD4 (GK1.5) or anti-CD3 (KT3) MAb to the recipient mice. The addition of cyclophosphamide in a dose that significantly depleted B cells in peripheral blood was highly effective in preventing rejection, with xenografts surviving for at least 112 days, when the experiment was terminated. CTLA4Ig, administered alone, did not prevent delayed rejection (rejection occurred in <60 days) and, in contrast to CP, did not prevent delayed rejection when used in combination with GK1.5 and KT3 treatment. Thus, immunosuppressive agents found to be highly effective in other strains, e.g., CTLA4Ig and anti-T cell MAbs, had a lesser effect in NOD mice but the addition of an anti-B cell drug, CP, was useful. This finding may be applicable to patients with IDDM.

Abatacept↗
PubMed1997

Disposition of basiliximab, an interleukin-2 receptor monoclonal antibody, in recipients of mismatched cadaver renal allografts.

BACKGROUND: Basiliximab is an interleukin-2 receptor (IL-2R; CD25) chimeric monoclonal antibody for immunoprophylaxis against acute rejection in renal transplantation. Its pharmacokinetics were characterized in a multicenter open-label, prospective dose-escalation study to identify a single-dose regimen providing IL-2R-saturating serum concentrations in the critical first posttransplant month. METHODS: Thirty-two recipients of primary, mismatched cadaver kidneys were enrolled: 20 men and 12 women, who were 47+/-11 years old and weighed 65+/-12 kg. The immunosuppression regimen consisted of steroids and azathioprine from day 0 and cyclosporine from day 10. Basiliximab was infused over 30 min as a single dose preoperatively. RESULTS: Thirty patients were evaluable for basiliximab pharmacokinetics: 24 received 40 mg and 6 received 60 mg. Basiliximab was well tolerated without evidence of cytokine-release syndrome, hypersensitivity reactions, or anti-idiotype antibody response. Peak concentration and area under the concentration curve increased proportionally with dose. Postinfusion concentrations declined in a biphasic manner with a terminal half-life of 6.5+/-2.1 days. Weak, widely dispersed correlations were noted between body weight versus distribution volume (r=0.29) and versus clearance (r=0.45), suggesting no clinical relevance for weight-adjusted dosing. There were no apparent gender-related differences in basiliximab disposition. Previous phase II data indicated that serum concentrations in excess of 0.2 microg/ml are sufficient to saturate IL-2R epitopes on circulating T lymphocytes. Concentrations were above this threshold for 26+/-8 days (range 16 to 46) at the 40-mg dose level and for 32+/-11 days (range 22 to 51) at the 60-mg dose level. CONCLUSIONS: Total basiliximab doses of 40-60 mg were well tolerated, nonimmunogenic, and estimated to provide immunoprophylaxis to cover the first posttransplant month.

Adult↗
PubMed1997

Up-regulation of Fas (CD95) in human p53wild-type cancer cells treated with ionizing radiation.

Fas is a cell-surface protein which belongs to the tumor-necrosis-factor-receptor family. Signals through Fas are able to induce apoptosis in sensitive cells, and thus modalities for regulating the level of Fas expression on tumor cells are needed. We have studied cellular responses to gamma irradiation. The level of p53 tumor-suppressor protein was found to be elevated 3 hr after irradiation of p53wild-type MCF-7 breast-carcinoma cells. Interestingly, accumulation of p53 was followed by up-regulation of surface Fas levels between 4 and 8 hr after irradiation. The level of Fas up-regulation was dependent on dose and, whereas elevation in the level of p53 was transient, enhancement of Fas expression was stable. Fas up-regulation occurred coincidentally with induction of G1 cell-cycle arrest, a post-irradiation phenomenon known to be dependent on wild-type-p53 activity. We studied 9 other tumor lines, 2 with wild-type p53, 5 with mutant p53, and 2 expressing no p53. All lines expressing wild-type p53 were found to arrest in G1 and to up-regulate Fas after irradiation. In contrast, all 7 p53null and p53mutant lines failed not only to arrest their cell cycles in G1 phase, but also to up-regulate Fas levels in response to treatment. These findings demonstrate a direct correlation between wild-type-p53 activity and Fas up-regulation after treatment with ionizing radiation, strongly suggesting that post-irradiation Fas up-regulation is dependent on wild-type-p53 activity. Since low doses of radiation were sufficient to modulate Fas expression, up-regulation of the Fas death receptor may have clinical implications following radiotherapy.

Breast Neoplasms↗
PubMed1997

The role of cytokines during rejection of foetal pig and foetal mouse pancreas grafts in nonobese diabetic mice.

The rejection of discordant foetal pig islet xenografts in nonimmunosuppressed nonobese diabetic (NOD) mice is dominated by polymorphonuclear cell infiltration whereas allografts are almost exclusively infiltrated by mononuclear cells. To determine if this variation is due to different proinflammatory factors generated at the graft site, we analysed graft-site mRNA expression of various cytokines, and the eosinophil attractant chemokine, eotaxin, in a renal subcapsular islet transplant model using organ cultured foetal pig (xenograft) and foetal BALB/c (allograft) pancreas in prediabetic NOD mice. Using semiquantitative RT-PCR on samples recovered at multiple time points during the first 15 post-transplantation days from mice transplanted with either allogeneic or xenogeneic tissue, we found increased expression of IL-2, IL-4. TNF-beta and IL-10 mRNAs at the peak of the cellular infiltrate (on day 5) in both xenografts and allografts but, in contrast to the allografts, no enhanced transcription of IFN-gamma mRNA in the rejecting xenografts. When an allograft and a xenograft were placed at the opposite pole of the same kidney the histological appearance of the rejecting allograft site resembled the xenograft site with significant numbers of eosinophils in both, and enhanced expression of eotaxin and iNOS. Additionally, the xenograft response, unlike the allograft response, was marked by an early increased expression of TNF-alpha and IL-S (day 3) and an almost complete absence of IFN-gamma expression. The results suggest a distinct cell-mediated mechanism for rejection of foetal pancrease xenografts compared to the rejection of foetal pancreas allografts.

Animals↗
PubMed1997

Expression of both Th1 and Th2 cytokines correlates with the histological rejection of MHC-matched and MHC-mismatched foetal pancreas allografts in mice.

Foetal mouse pancreatic islet grafts were used to investigate differences in the histological appearance and cytokine expression pattern during acute rejection of fully MHC-mismatched, and MHC-matched but minor histocompatibility-mismatched (mH) allografts. Grafts of foetal islet tissue from non-obese diabetic mice under the kidney capsule of non-immunosuppressed MHC and mH-disparate BALB/c mice were rejected by day 9, whereas the rejection of only mH-disparate C3H tissue into CBA mice occurred between 11 and 15 days. In both situations enhanced expression of transcripts for Th1 (IL-2, IFN-gamma, TNF-beta) and Th2 cytokines (IL-4, IL-6, IL-10) was demonstrable at the peak of infiltration of immune cells into the graft site, indicating a close association of these cytokines with graft destruction. Besides these kinetic differences no variation in the expression pattern of the tested cytokines could be demonstrated, indicating that the allograft response in either combination leads to enhanced expression of pro-inflammatory cytokines which could contribute to graft destruction.

Animals↗
PubMed1997

Cytokines and autoimmune beta cell destruction in NOD mouse fetal pancreas isografts in cyclophosphamide-induced diabetes.

The role of cytokines in a model of cyclophosphamide (CP)-accelerated beta cell destruction in fetal pancreas isografts transplanted into NOD mice was studied. One group of prediabetic NOD mice was injected with CP at a dose of 300 mg/kg i.p. and 7 days later isografts of organ cultured fetal pancreas (FP) were transplanted under the kidney capsule of these and untreated control mice. The mice were killed at several time points post-transplantation and the histological appearance of the host pancreas used to evaluate the disease progress in the grafts since previous studies had shown good correlation between isograft and native pancreas pathology. Intragraft cytokine gene expression was monitored by reverse-transcriptase polymerase chain reaction (RT-PCR) at the same time points and the expression levels between the experimental groups compared to normal kidney tissue. In comparison to isografts from non-CP injected mice, isografts from CP-treated mice showed increased expression of IFN-gamma, TNF-alpha, TNF-beta, IL-5, and eotaxin but no increase in IL-10 expression. The enhanced transcription of these cytokines correlated with massive infiltration of immune cells and ongoing beta cell destruction in the host pancreas of the CP-treated recipients.

Animals↗
PubMed1996

Induction of alloantigen-specific hyporesponsiveness in vitro by n-butyrate: antagonistic effect of cyclosporin A.

The short-chain fatty acid n-butyrate has recently been shown in vitro to specifically downregulate T cell reactivity to nominal antigen or to alloantigen, which possibly results from inhibition of cell cycle progression in early G1 phase during antigen contact. In the present study, we investigated the effect of cyclosporin A (CyA) on the modulation of alloreactivity in human mixed lymphocyte culture (MLC) by n-butyrate. Whereas in primary culture, CyA additively enhanced inhibition of DNA synthesis by n-butyrate, the effect of this agent on secondary T cell reactivity was clearly antagonized by CyA. Thus, specific downregulation of proliferative responsiveness to restimulation with antigen from the original donor, observed in cultures pretreated with n-butyrate alone, was at least partially prevented by the addition of CyA to the primary culture. Our in vitro finding indicates that specific downregulation of T cell alloreactivity by n-butyrate might depend on a calcium-dependent T cell receptor (TCR)-mediated signal sensitive to the immunosuppressive action of CyA.

Butyrates↗