Biomedical subjects

R J Debs

Publications and source records attributed to R J Debs.

At least 37 records · Page 2Linked to original sources

PubMed1990

Immunomodulatory and toxic effects of free and liposome-encapsulated tumor necrosis factor alpha in rats.

Tumor necrosis factor alpha has potent immunomodulatory and antitumor activity, but its therapeutic applications may be limited by its significant host toxicity. We showed that liposome-encapsulated recombinant human tumor necrosis factor alpha (rHuTNF-alpha) retained full anticellular activity in vitro. We then assessed the immunomodulatory and toxic effects of two different doses of i.v. free or liposome-encapsulated rHuTNF-alpha in normal rats. Both free and liposome-encapsulated rHuTNF-alpha significantly enhanced alveolar macrophage- and blood monocyte-mediated interleukin 1 release and tumor cell lysis, as well as natural killer cell cytotoxicity, when compared to buffer-treated controls. However, administration of rHuTNF-alpha in liposomes substantially reduced tumor necrosis factor alpha-mediated toxicity. Animals receiving liposome-encapsulated rHuTNF-alpha showed significantly less tissue injury, gastric retention, and circulating leukocyte shifts than animals receiving free rHuTNF-alpha. In addition, liposome-based delivery significantly increased lung and liver uptake of rHuTNF-alpha. Therefore, liposome-encapsulated rHuTNF-alpha retains immunomodulatory activity, significantly reduces toxic inflammatory effects, and may allow targeting of tumor necrosis factor alpha to selected organs after i.v. administration.

Adjuvants, Immunologic↗

PubMed1990

Interaction of antimycobacterial and anti-pneumocystis drugs with phospholipid membranes.

Liposomes can be used as carriers of drugs in the treatment of viral, bacterial and protozoal infections. The potential for liposome-mediated therapy of Mycobacterium avium-intracellulare complex infections, one of the most common opportunistic infections in AIDS, is currently under study. Here, we have investigated the effect of the lipid-soluble antimycobacterial drugs ansamycin, clofazimine and CGP7040 on the thermotropic behavior of liposomes composed of dipalmitoylphosphatidylcholine (DPPC) or dipalmitoylphosphatidylglycerol (DPPG) using differential scanning calorimetry (DSC). In the presence of ansamycin (rifabutine), the peak gel-liquid crystalline phase transition temperature (Tm) of DPPG was reduced, as was the sub-transition temperature (Ts), whereas the Tm of DPPC was reduced only slightly. The temperature of the pre-transition (Tp) of DPPC was lowered, while the pre-transition of DPPG was abolished. Ansamycin also caused the broadening of the transition endotherm of both lipids. Equilibration of the drug/lipid complex for 1 or 5 days produced different thermotropic behavior. In the presence of clofazimine, the cooperativity of the phase transition of DPPG decreased. Above 10 mol% clofazimine formed two complexes with DPPG, as indicated by two distinguishable peaks in DSC thermograms. The Tm of both peaks were lowered as the mole fraction increased. Clofazimine had minimal interaction with DPPC. In contrast, CGP7040 interacted more effectively with DPPC than with DPPG, causing a reduction of the size of the cooperative unit of DPPC even at 2 mol%. The main transition of DPPC split into 3 peaks at 5 mol% drug. The pre-transition was abolished at all drug concentrations and the sub-transition disappeared at 10 mol% CGP7040. These studies suggest that maximal encapsulation of clofazimine in liposomes would require a highly negatively charged membrane, while that of CGP7040 would necessitate a zwitterionic membrane. We have also investigated the interaction of the water-soluble antibiotic pentamidine, which has been used against Pneumocystis carinii, the most lethal of AIDS-related opportunistic pathogens. Aerosol administration of this drug leads to long-term sequestration of the drug in the lungs. The DPPG/pentamidine complex exhibited a pre-transition at 3.5 degrees C, an endothermic peak at 42 degrees C, and an exothermic peak at 44.5 degrees C, followed by another endothermic peak at 55 degrees C. The exotherm depended on the history of the sample, requiring pre-incubation for several minutes below the 42 degrees C transition. These observations suggest that upon melting of the DPPG chains at 42 degrees C, the DPPG crystallizes as a DPPG/pentamidine complex that melts at 55 degrees C.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed1990

Differential effects of free and liposome encapsulated amikacin on the survival of Mycobacterium avium complex in mouse peritoneal macrophages.

Liposome-encapsulated amikacin shows significantly greater inhibitory activity against the survival of Mycobacterium avium complex inside mouse peritoneal macrophages than the free drug. Similar results were obtained whether the drug was added simultaneously with, 48 h prior to, or 48 h after the addition of mycobacteria to the macrophages. These observations support the hypothesis that the in vivo intravenous delivery of liposome-encapsulated amikacin results in the localization of the antibiotic in phagosomes containing mycobacteria inside resident macrophages of the liver and spleen.

Amikacin↗

PubMed1990

Monocyte-mediated lysis of HIV-infected tumor cells.

Peripheral blood monocytes (PBM) can selectively lyse malignant or virus-infected cells. We investigated the effects of target cell infection with HIV-1 on PBM cytolytic function. Cytokine-activated PBM lysed uninfected, HSV-1-infected or vaccinia virus-infected tumor cells, but did not lyse the same cell lines when infected with the human immunodeficiency virus type 1 (HIV-1). HIV did not impair PBM viability, and actinomycin D (Act D) pretreatment of HIV-infected target cells restored their susceptibility to PBM-mediated lysis. Either antibody to CD4 (Leu3a) or a recombinant vaccinia virus that induces expression of the HIV envelope protein, also inhibited target cell lysis by PBM. These studies indicate that CD4 can function as a mediator of PBM cytolytic function, and that target cell expression of the HIV-1 envelope protein may inhibit monocyte-mediated antitumor responses.

Antibodies, Monoclonal↗

PubMed1990

Liposomes modulate human immunodeficiency virus infectivity.

We have investigated the effects of the fusion of liposomes with human immunodeficiency virus type 1 (HIV-1LVA) on the ability of the virus to infect CD4+ and CD4- cells. Fluorescence dequenching measurements indicated that HIV-1 fuses with liposomes composed of either cardiolipin (CL) or N-[2,3-(dioleyloxy) propyl]-N,N,N-trimethyl ammonium chloride (DOTMA) but not appreciably with dioleoylphosphatidylcholine (DOPC) liposomes. Pre-incubation of HIV-1 with DOTMA liposomes enhanced virus production (measured by p24 gag antigen production in the culture medium and in situ) in CD4+ A3.01 and H9 cells in a concentration-dependent manner, but did not mediate the infection of the CD4- cell line, K562. Preincubation of HIV-1 with between 10 and 30 microM-DOTMA liposomes, and subsequent incubation with A3.01 cells, resulted in the production of about 30-fold greater levels of virus than controls. The presence of DOTMA liposomes during the incubation of A3.01 cells with HIV-1 enhanced the infectivity of the virus up to 90-fold compared to controls. Conversely, preincubation of HIV-1 with CL liposomes inhibited infection of A3.01 cells, dependent on the concentration of liposomes; DOPC liposomes did not alter the infectivity of the virus under any of the incubation conditions. Our results thus indicate that fusion of HIV-1 with liposomes alters the ability of the virus to infect its target cells.

CD4 Antigens↗

PubMed1990

Occupational exposure to aerosolized pentamidine.

Occupational exposure to aerosolized pentamidine has raised questions regarding transmission of tuberculosis and the effect of the drug itself. To estimate the exposure of a health care worker, we measured the ambient concentration of aerosolized pentamidine in field conditions in 36 m3 unventilated treatment room. The amount of pentamidine averaged in three different environmental air samples over a four-hour period was 4.5 +/- 3.6 x 10(-5) mg/m3. This amount is very small compared to the doses received by the patients in whom long-term adverse effects are few. The greater risk to health care workers is probably transmission of tuberculosis from undiagnosed cases, especially in populations with an increased incidence of tuberculosis. Tuberculosis control measures such as improved ventilation and masks should also decrease exposure to ambient air pentamidine until toxicity studies determine long-term adverse effects, if any, of aerosolized pentamidine.

Acquired Immunodeficiency Syndrome↗

PubMed1989

Liposome-associated tumor necrosis factor retains bioactivity in the presence of neutralizing anti-tumor necrosis factor antibodies.

Cell-associated TNF-alpha, either bound to its receptor on monocyte membranes or expressed as an integral membrane protein, can exert potent tumor cytolytic activity. We assessed the interaction of TNF with the lipid bilayer membrane system, liposomes, and the effects of membrane association on TNF bioactivity. High levels of TNF can be encapsulated within liposomes. At neutral pH, TNF binds to the surface of preformed liposomes (liposome-associated TNF), but does not partition into the lipid bilayer. TNF appears to bind to negatively charged phospholipid head groups of the outer membrane leaflet. Free TNF, liposome-associated TNF, and liposome-encapsulated TNF display comparable abilities to activate human peripheral blood monocytes and to lyse tumor cells. However, liposome-encapsulated TNF, as well as TNF bound to the outer surface of preformed liposomes, retains bioactivity in the presence of anti-TNF antibodies that neutralize free TNF. The interaction of liposomal TNF with cell surface TNF receptors thus appears to be preserved in the presence of neutralizing antibodies.

Adult↗

PubMed1989

The folate antagonist, methotrexate, is a potent inhibitor of murine and human cytomegalovirus in vitro.

Cytomegalovirus (CMV) is a major source of morbidity for immunocompromised patients, such as AIDS patients. The folic acid antagonists have not been explored as potential antiviral agents against CMV. We examined the effects of methotrexate, compared to acyclovir and ganciclovir, on both murine CMV (MCMV) and human CMV (HCMV) in vitro. Using a plaque assay in mouse embryo cells or human foreskin fibroblasts for MCMV and HCMV respectively, we found that methotrexate, in micromolar concentrations, was a potent inhibitor of both viruses. This effect was due to folic acid antagonism since folinic acid abrogated the antiviral effect of methotrexate, but not ganciclovir. Cellular toxicity due to methotrexate appeared insufficient to account for the antiviral effects. The ability of methotrexate to inhibit CMV in vivo merits exploration.

Acyclovir↗

PubMed1989

Incorporation of recombinant gamma interferon into liposomes enhances its ability to induce peritoneal macrophage antitoxoplasma activity.

In this study we compared the ability of free- and liposome-incorporated murine recombinant gamma interferon (rIFN-gamma) to enhance peritoneal macrophage H2O2 release and antitoxoplasma activity in vitro. rIFN-gamma was efficiently (37 to 47%) incorporated into multilamellar vesicles composed of phosphatidylglycerol/cholesterol in a 2:1 molar ratio. The amount of rIFN-gamma incorporated into multilamellar vesicles and added to macrophages (0.1 to 1,000 U/ml) was quantitated with [3H]rIFN-gamma. The concentration of liposomal rIFN-gamma required to enhance macrophage H2O2 release (1 U/ml) and maximally inhibit Toxoplasma gondii growth (10 U/ml) was one-tenth the concentration required for free rIFN-gamma (10 and 100 U/ml, respectively). This increase in potency was observed in both thioglycolate-elicited and resident peritoneal macrophages. Control liposomes containing encapsulated buffer had no effect on the potency of free rIFN-gamma. The duration of macrophage activation induced by 24 h of liposomal rIFN-gamma treatment was also considerably longer than that induced by free rIFN-gamma (2 days versus less than 1 day). These data indicate that liposomal rIFN-gamma is more active than free rIFN-gamma as an inducer of macrophage microbicidal properties in vitro. This enhanced activity, combined with the potential for selective delivery of liposomal rIFN-gamma to phagocytic cells in vivo, may improve the therapeutic efficacy of rIFN-gamma in infections characterized by parasitization of phagocytes.

Animals↗

PubMed1989

Aerosolized pentamidine as second line therapy in patients with AIDS and Pneumocystis carinii pneumonia.

The use of aerosolized pentamidine was investigated in ten patients with the acquired immunodeficiency syndrome (AIDS) and Pneumocystis carinii pneumonia (PCP) who had previous or concurrent severe adverse reactions or contraindications to trimethoprim-sulfamethoxazole or parenteral pentamidine. A dose of 600 mg pentamidine in 6 ml sterile water, aerosolized in a small-particle producing jet nebulizer was administered for 25 minutes once daily for an average of 10.5 days to these ten patients. All patients improved their arterial O2 saturation and showed clinical and roentgenographic improvement within six to 21 days of aerosol pentamidine therapy. No adverse systemic reactions occurred. The results of this small open trial indicate that aerosolized pentamidine is effective and can be given safely to AIDS patients with PCP who have had adverse reactions to trimethoprim-sulfamethoxazole or parenteral pentamidine.

Acquired Immunodeficiency Syndrome↗

PubMed1988

Liposome-based therapy of human ovarian cancer: parameters determining potency of negatively charged and antibody-targeted liposomes.

Liposomes containing cytotoxic agents may be highly efficacious for intracavitary therapy of malignancies such as ovarian carcinoma, which resides principally in the peritoneal cavity. We have examined in vitro the cytotoxicity of a variety of liposome-drug formulations against OVCAR-3, a human ovarian cancer cell line. Two drugs tested, methotrexate-gamma-aspartate and 5-fluoroorotate, show increased cytotoxicity on various cultured cell lines following encapsulation in liposomes and can be considered liposome-dependent agents. With the optimal lipid composition used in this study, the maximal increase in potency on OVCAR-3 is 2.6-fold for methotrexate-gamma-aspartate and 5.2-fold for 5-fluoroorotate. Studies on liposome-cell association suggest a low capacity of OVCAR-3 to bind and internalize phospholipid vesicles, which limits the in vitro potency of liposomes for these cells. OC-125, a monoclonal antibody recognizing an antigen common to a number of human ovarian cancers (CA-125), has been coupled covalently to the liposome surface. Liposomes bearing OC-125 and containing methotrexate-gamma-aspartate show an 8-fold increase in potency against OVCAR-3 cells in a 96-h growth inhibition assay. Briefer exposure of tumor cells to treatment accentuates the advantage of targeted liposomes. The cytostatic effect of 1 h exposure to OC-125 liposomes is 100-fold greater than the equivalent exposure to free drug and equal to the maximal cytostatic effect achieved with free drug for 96 h. Attachment of OC-125 antibody also confers upon liposomes the capacity to recognize OVCAR-3 cells growing as an ascites tumor in nude mice. After i.p. injection, control liposomes bind tumor cells in relatively low numbers, while fluorescent OC-125 liposomes can be observed bound specifically to tumor cell masses for periods of days.

Antibodies, Monoclonal↗

PubMed1988

Lung-specific delivery of cytokines induces sustained pulmonary and systemic immunomodulation in rats.

The recombinant cytokines IFN-gamma and TNF-alpha stimulate several macrophage-mediated functions important in host defense. However, systemic administration of cytokines may be limited by significant host toxicity. We investigated whether aerosolized cytokines can stimulate alveolar macrophage and blood monocyte function, and whether they induce an inflammatory response in the lungs of normal rats. We found that aerosolized murine rIFN-gamma or recombinant human TNF-alpha increased IL-1 production by both alveolar macrophages and blood monocytes for at least 5 days after administration. Furthermore, murine rIFN-gamma increased the expression of Ia Ag on alveolar macrophages and human rTNF-alpha increased alveolar macrophage- and blood monocyte-mediated tumor lysis. Sequential aerosolization of IFN-gamma and TNF-alpha significantly increased both IL-1 release and Ia expression compared to either cytokine administered alone. Aerosolized human rTNF-alpha achieved lung levels comparable to those produced by an i.v. TNF-alpha dose reported to cause diffuse organ injury and death in rats. However, plasma TNF-alpha levels were several thousand-fold lower after aerosol administration. Aerosolized cytokines did not induce lung edema or an inflammatory cell infiltrate within the airways or alveoli. Aerosolized human rTNF-alpha alone, or murine rIFN-gamma and human rTNF-alpha, induced margination of leukocytes in pulmonary blood vessels 1 day after aerosolization, and a few small foci of pulmonary hemorrhage 5 days later. We conclude that aerosol administration of IFN-gamma or TNF-alpha enhances both pulmonary and systemic monocyte function, and that the combination of IFN-gamma and TNF-alpha produce additive or synergistic effects. Aerosolized cytokines induce only a minimal pulmonary inflammatory response. Aerosolized TNF-alpha produces high cytokine levels in the lung but very low uptake into the circulation.

Adjuvants, Immunologic↗

PubMed1988

Aerosol administration of antiviral agents to treat lung infection due to murine cytomegalovirus.

Cytomegalovirus (CMV) pneumonia causes significant morbidity and mortality in bone marrow transplant recipients and in patients with AIDS. 9-(1,3-Dihydroxy-2-propoxymethyl) guanine (ganciclovir) and phosphonoformic acid (PFA) demonstrate activity against CMV in human infections, although recurrent CMV and systemic drug toxicity frequently develop. We examined the efficacy of aerosol administration of antiviral agents against murine CMV (MCMV) infection. Animals were inoculated with MCMV intranasally and were treated with oral ganciclovir; with aerosolized ganciclovir, PFA, or ribavirin; or with buffer. MCMV in lung and salivary gland homogenates was quantified by plaque assay. Oral ganciclovir (200 mg/kg per day) reduced titers of MCMV in both tissues by greater than 95%. Aerosolized ganciclovir, 100 and 200 mg/kg per day, reduced lung titers of MCMV by 93% and 97%, respectively. Aerosolized PFA, 20 and 200 mg/kg per day, reduced lung titers of MCMV by 60% and 68%, respectively. Aerosolized ganciclovir and PFA inhibited replication of MCMV in salivary glands substantially less than did oral administration of either agent. Our results suggest that aerosol administration of antiviral agents can potently and selectively inhibit replication of MCMV in the lung.

Acyclovir↗

PubMed1988

Enhanced effect of liposome-encapsulated amikacin on Mycobacterium avium-M. intracellulare complex infection in beige mice.

We examined the therapeutic effects of free and liposome-encapsulated amikacin on Mycobacterium avium-M. intracellulare complex infection by using the beige-mouse model of the disease. In the first series of studies, intravenous administration of four weekly doses of 5 mg of amikacin per kg encapsulated in large (approximately 0.4-micron diameter), unilamellar liposomes arrested the growth of M. avium-M. intracellulare complex organisms in the liver, as measured by CFU counts. M. avium-M. intracellulare complex levels in untreated animals and in those treated with the same dose of free amikacin increased by several orders of magnitude over 8 weeks. Liposome-encapsulated amikacin was also effective against M. avium-M. intracellulare complex organisms in the spleen and kidneys, reducing the CFU counts by about 1,000-fold compared with those of both untreated controls and free-drug-treated mice. In the lungs, a slight reduction in CFU was observed in the liposome-encapsulated-amikacin-treated group, but only at the 8-week point. Neither free nor liposome-encapsulated amikacin reduced the colony counts in the lymph nodes compared with those of control animals. Reductions in CFU in all organs greater than those caused by the liposome preparation could be achieved by intramuscular administration of free amikacin, but only at a 10-fold-higher dose given 6 days a week for 8 weeks. In the second series of studies, we investigated the effects of (i) doubling the dose of liposome-encapsulated amikacin and (ii) increasing the size of the liposomes and prolonging the treatment to five injections. Administration of 10 mg of amikacin per kg in liposomes 2 to 3 micrometer in diameter was more effective in the liver than 5 or 10 mg of amikacin per kg in liposomes 0.2 micrometer in diameter. A slight reduction in the CFU levels in the lungs was observed with the higher dose, irrespective of liposome size. Our results indicate that liposome-based delivery of amikacin enhances its anti-M. intracellulare complex activity, particularly in the liver, spleen, and kidney, and may therefore improve the therapy of this disease.

Amikacin↗

PubMed1988

Selective delivery of pentamidine to the lung by aerosol.

In 8 patients with diffuse infiltrates on chest radiograph undergoing fiberoptic bronchoscopy for suspected Pneumocystis carinii pneumonia, bronchoalveolar lavage sediment and supernatant concentrations of pentamidine were compared 18 to 24 h after administration of 4 mg/kg intravenous (n = 3) and aerosolized (n = 5) pentamidine isethionate. Aerosol was inhaled for 35 to 40 min with 300 mg of pentamidine isethionate in a jet nebulizer, baffled to decrease the particle size to 1.42 micron +/- 1.88 (mass median aerodynamic diameter +/- geometric standard deviation). Bronchoalveolar pentamidine concentrations were: In sediment, 9.34 +/- 1.74 postintravenous versus 705 +/- 242 ng/ml postaerosol (mean +/- SEM, p less than 0.05); supernatant, 2.64 +/- 0.73 postintravenous versus 23.2 +/- 7.75 ng/ml postaerosol (mean +/- SEM, p less than 0.05). Serum pentamidine levels were low or undetectable after aerosolization. Aerosol administration delivers significantly higher concentrations of pentamidine to the air spaces than does intravenous delivery in patients with diffuse alveolar infiltrates.

Acquired Immunodeficiency Syndrome↗

PubMed1988

Enhanced human monocyte cytotoxicity by platelet-activating factor.

The capacity of platelet-activating factor (PAF) to enhance human monocyte cytotoxicity for WEHI 164 cells was examined. Spontaneous monocyte cytotoxicity was 24 +/- 2% (mean +/- SEM, n = 9). Preincubation of monocytes with 1 pM-1 nM PAF for 18 hr significantly enhanced cytotoxicity in a dose-related manner, whereas less enhancement was observed at PAF concentrations above 1 nM. Maximal PAF-induced cytotoxicity was 68 +/- 6%, which was similar to that induced by optimal concentrations of tumour necrosis factor (TNF) and interferon-gamma. The specific PAF antagonist kadsurenone inhibited PAF-induced cytotoxicity but not TNF-induced cytotoxicity. The inactive PAF analogues lysoPAF and enantioPAF did not increase monocyte cytotoxicity. Two observations suggest that TNF mediates PAF-induced cytotoxicity: specific anti-TNF antibodies inhibited PAF-induced cytotoxicity toward WEHI 164 cells, and PAF did not enhance cytotoxicity to TNF-resistant cells. PAF represents a distinct class of phospholipid monocyte activators that increase monocyte cytotoxicity by TNF-dependent mechanisms.

Benzofurans↗

PubMed1987

Aerosolised pentamidine as sole therapy for Pneumocystis carinii pneumonia in patients with acquired immunodeficiency syndrome.

15 patients with first episodes of Pneumocystis carinii pneumonia and the acquired immunodeficiency syndrome were treated with only aerosolised pentamidine, which they inhaled for 20 minutes every day for 21 days. 13 of the 15 responded to therapy. Mean PaO2 (mm Hg) and vital capacity (% predicted) were 67.9 and 50.8 before therapy and 80.1 and 67.9 after therapy in patients successfully treated. No systemic side-effects occurred and serum pentamidine concentrations were low in all patients. The only local adverse reaction was cough in 12 patients. Aerosolised pentamidine may be an effective non-toxic treatment for P carinii pneumonia.

Acquired Immunodeficiency Syndrome↗

PubMed1987

Targeting of anti-Thy 1.1 monoclonal antibody conjugated liposomes in Thy 1.1 mice after intravenous administration.

125I-labeled liposomes, conjugated to an anti-Thy 1.1 monoclonal antibody (MRCOX7), demonstrated up to 7.4-fold greater lymph node uptake than liposomes conjugated to non-specific monoclonal antibody (R-10) after intravenous injection into Thy 1.1 (AKR-J) mice. Uptake of anti-Thy 1.1-conjugated liposomes by the lymph nodes of AKR-J mice was 3-times greater than their uptake by lymph nodes of Thy 1.2 (AKR-Cu) mice. Lymph node localization of anti-Thy 1.1-liposomes was equal to that of control monoclonal antibody-liposomes in Thy 1.2 mice. Conjugation to either monoclonal antibody substantially increased liposome clearance by the liver, while decreasing liposome uptake in a number of organs outside the reticuloendothelial system. Changes in liposome size and phospholipid composition did not significantly alter these results. Administration of a large predose of unconjugated liposomes prior to injection of MRCOX7-conjugated liposomes increased blood levels and reduced liver uptake of the monoclonal antibody-liposome conjugates, but did not further enhance lymph node uptake. This study demonstrates that targeting of liposomes by conjugation to the appropriate monoclonal antibody, can significantly increase their uptake in lymph nodes which contain high levels of cells expressing the target antigen. However, conjugation to monoclonal antibody also increases clearance of liposomes by the liver. To increase the uptake of monoclonal antibody-conjugated liposomes in target tissue, substantial reduction of their clearance by the reticuloendothelial system will be required.

Animals↗