Unusual locations of involvement by malignancies: Case 2. Metastatic pheochromocytoma to the colon.
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Adult↗
Biomedical subjects
A Louie
Publications and source records attributed to A Louie.
Impact of the order of initiation of fluconazole and amphotericin B in sequential or combination therapy on killing of Candida albicans in vitro and in a rabbit model of endocarditis and pyelonephritis.
In vitro time-kill studies and a rabbit model of endocarditis and pyelonephritis were used to define the impact that the order of exposure of Candida albicans to fluconazole (FLC) and amphotericin B (AMB), as sequential and combination therapies, had on the susceptibility of C. albicans to AMB and on the outcome. The contribution of FLC-induced resistance to AMB for C. albicans also was assessed. In vitro, AMB monotherapy rapidly killed each of four C. albicans strains; FLC alone was fungistatic. Preincubation of these fungi with FLC for 18 h prior to exposure to AMB decreased their susceptibilities to AMB for 8 to >40 h. Induced resistance to AMB was transient, but the duration of resistance increased with the length of FLC preincubation. Yeast sequentially incubated with FLC followed by AMB plus FLC (FLC-->AMB+FLC) showed fungistatic growth kinetics similar to that of fungi that were exposed to FLC alone. This antagonistic effect persisted for at least 24 h. Simultaneous exposure of C. albicans to AMB and FLC [AMB+FLC(simult)] demonstrated activity similar to that with AMB alone for AMB concentrations of > or =1 microg/ml; antagonism was seen using an AMB concentration of 0.5 microg/ml. The in vitro findings accurately predicted outcomes in our rabbit infection model. In vivo, AMB monotherapy and treatment with AMB for 24 h followed by AMB plus FLC (AMB-->AMB+FLC) rapidly sterilized kidneys and cardiac vegetations. AMB+FLC(simult) and FLC-->AMB treatments were slower in clearing fungi from infected tissues. FLC monotherapy and FLC-->AMB+FLC were both fungistatic and were the least active regimens. No adverse interaction was observed between AMB and FLC for the AMB-->FLC regimen. However, FLC-->AMB treatment was slower than AMB alone in clearing fungi from tissues. Thus, our in vitro and in vivo studies both demonstrate that preexposure of C. albicans to FLC reduces fungal susceptibility to AMB. The length of FLC preexposure and whether AMB is subsequently used alone or in combination with FLC determine the duration of induced resistance to AMB.
Amphotericin B↗
Pharmacodynamics of daptomycin in a murine thigh model of Staphylococcus aureus infection.
Daptomycin is a lipopeptide antibiotic with activity against gram-positive bacteria, including Staphylococcus aureus. We defined the pharmacodynamic parameters that determine the activity of daptomycin for S. aureus using in vitro methods and the Craig (W. A. Craig, J. Redington, and S. C. Ebert, J. Antimicrob. Chemother. 27[Suppl. C]:29--40, 1991) neutropenic mouse thigh infection model. In Mueller-Hinton broth, the MICs for three S. aureus isolates were 0.1 to 0.2 microg/ml. In mouse serum, the MICs were 1.0 microg/ml. The protein binding of daptomycin was 90 to 92.5% in mouse serum. Single-dose intraperitoneal (i.p.) pharmacokinetic studies with infected mice showed a linear relationship between dose versus the maximum concentration of drug in serum and dose versus the area under the concentration-time curve (AUC). The serum half-life of daptomycin in infected mice was approximately 1.8 h. In single-dose, dose-ranging studies using mice, daptomycin showed a dose-response effect described by an inhibitory sigmoid E(max) (maximum effect) curve (r = 0.974; P << 0.001). The density of S. aureus in untreated controls was 8.26 log(10) CFU/g, and the E(max) was 3.97 log(10) CFU/g. The 50% effective dose (ED(50)) was 3.7 mg/kg of body weight i.p. and the stasis dose was 7.1 mg/kg. Dose fractionation studies at schedules of Q6h, Q12h, and Q24h, for total 24-h ED(30), ED(60), and ED(80) doses of 2.5, 5.6, and 15 mg/kg i.p., showed no difference in effect at each total 24-h dose level by schedule, indicating that the AUC/MIC ratio is the dynamically linked variable.
Animals↗
Phase I and pharmacologic study of PN401 and fluorouracil in patients with advanced solid malignancies.
PURPOSE: To assess the feasibility of administering PN401, an oral uridine prodrug, as a rescue agent for the toxic effects of fluorouracil (5-FU), and to determine the maximum-tolerated dose of 5-FU when given with PN401, with an 8-hour treatment interval between these agents. PATIENTS AND METHODS: Patients with advanced solid malignancies were treated with escalating doses of 5-FU, given as a rapid intravenous infusion weekly for 3 consecutive weeks every 4 weeks. PN401 was administered orally 8 hours after 5-FU administration, to achieve sustained plasma uridine concentrations of at least 50 micromol/L. Initially, patients received 6 g of PN401 orally every 8 hours for eight doses (schedule 1). When dose-limiting toxicity (DLT) was consistently noted, patients then received 6 g of PN401 every 2 hours for three doses and every 6 hours thereafter for 15 doses (schedule 2). RESULTS: Twenty-three patients received 50 courses of 5-FU and PN401. Among patients on schedule 1, DLT (grade 4 neutropenia complicated by fever and diarrhea) occurred in those receiving 5-FU 1,250 mg/m(2)/wk. Among patients on schedule 2, 5-FU 1,250 mg/m(2)/wk was well tolerated, but grade 4, protracted (> 5 days) neutropenia was consistently noted in those treated with higher doses of the drugs. Nonhematologic effects were uncommon and rarely severe. The pharmacokinetics of 5-FU, assessed in 12 patients on schedule 2, were nonlinear, with the mean area under the time-versus-concentration curve (AUC) increasing from 298 +/- 44 to 962 +/- 23 micromol/L and mean clearance decreasing from 34 +/- 4 to 15.6 +/- 0.38 L/h/m(2) as the dose of 5-FU was increased from 1,250 to 1,950 mg/m(2)/wk. 5-FU AUCs achieved with 5-FU 1,250 mg/m(2)/wk for 6 weeks along with the intensified PN401 dose schedule were approximately five-fold higher than those achieved with 5-FU alone. Plasma uridine concentrations increased with each of the three PN401 doses given every 2 hours, and uridine steady-state concentrations were greater than 50 micromol/L. CONCLUSION: Treatment with oral PN401 beginning 8 hours after 5-FU administration is well tolerated and results in sustained plasma uridine concentrations above therapeutic-relevant levels. The recommended 5-FU dosage for phase II evaluations is 1,250 mg/m(2)/wk for 3 weeks every 4 weeks with the intensified PN401 dose schedule (schedule 2). At this dose, systemic exposure to 5-FU as measured by AUC was five-fold higher than that observed after administration of a conventional 5-FU bolus.
Acetates↗
Efficacies of high-dose fluconazole plus amphotericin B and high-dose fluconazole plus 5-fluorocytosine versus amphotericin B, fluconazole, and 5-fluorocytosine monotherapies in treatment of experimental endocarditis, endophthalmitis, and pyelonephritis due to Candida albicans.
We compared the efficacies of fluconazole (Flu), amphotericin B (AmB), and 5-fluorocytosine (5FC) monotherapies with the combination of Flu plus 5FC and Flu plus AmB in a rabbit model of Candida albicans endocarditis, endophthalmitis, and pyelonephritis. The dose of Flu used was that which resulted in an area under the concentration-time curve in rabbits equivalent to that seen in humans who receive Flu at 1,600 mg/day, the highest dose not associated with central nervous system toxicity in humans. Quantitative cultures of heart valve vegetations, the choroid-retina, vitreous humor, and kidney were conducted after 1, 5, 14, and 21 days of therapy. All untreated controls died within 6 days of infection; animals treated with 5FC monotherapy all died within 18 days. In contrast, 93% of animals in the other treatment groups appeared well and survived until they were sacrificed. At day 5, the relative decreases in CFU per gram in the vitreous humor were greater in groups that received Flu alone and in combination with 5FC or AmB than in groups receiving AmB or 5FC monotherapies (P < 0. 005) but were similar thereafter. In the choroid-retina, 5FC was the least-active drug. However, there were no differences in choroidal fungal densities between the other treatment groups. On days 5 and 14 of therapy, fungal densities in kidneys of AmB recipients were lower than those resulting from the other therapies (P < 0.001 and P < or = 0.038, respectively) and AmB-plus-Flu therapy was antagonistic; however, all therapies for fungal pyelonephritis were similar by treatment day 21. While fungal counts in cardiac valves of Flu recipients were similar to those of controls on day 5 of therapy and did not change from days 1 to 21, AmB therapy significantly decreased valvular CFUs versus Flu at days 5, 14, and 21 (P < 0.005 at each time point). 5FC plus Flu demonstrated enhanced killing in cardiac vegetations compared with Flu or 5FC as monotherapies (P < 0. 03). Similarly, the combination of AmB and Flu was more active than Flu in reducing the fungal density in cardiac vegetations (P < 0.03). However, as in the kidney, AmB plus Flu demonstrated antagonism versus AmB monotherapy in the treatment of C. albicans endocarditis (P < 0.05, P = 0.036, and P < 0.008 on days 5, 14, and 21, respectively).
Amphotericin B↗
Interaction between fluconazole and amphotericin B in mice with systemic infection due to fluconazole-susceptible or -resistant strains of Candida albicans.
The interaction between fluconazole (Flu) and amphotericin B (AmB) was evaluated in a murine model of systemic candidiasis for one Flu-susceptible strain (MIC, 0.5 microg/ml), two strains with intermediate Flu resistance (Flu mid-resistant strains) (MIC, 64 and 128 microg/ml), and one highly Flu-resistant strain (MIC, 512 microg/ml) of Candida albicans. Differences in fungal densities in kidneys of infected mice after 24 h of therapy and in survival rates at 62 days of mice treated with an antifungal drug or a combination of antifungal drugs for 4 days were compared. For the Flu-susceptible and Flu mid-resistant strains, the combination of Flu and AmB was antagonistic, as shown by both quantitative culture results and survival. The interaction was additive for the highly Flu-resistant strain. These results suggest that the combination of Flu and AmB should be used with caution in infections due to fungi that are usually susceptible to both antifungal agents and as empirical antifungal drug therapy.
Amphotericin B↗
Comparison of fluconazole pharmacokinetics in serum, aqueous humor, vitreous humor, and cerebrospinal fluid following a single dose and at steady state.
The objective of this study was to characterize the pharmacokinetic parameters and penetration of fluconazole following a single dose in the serum, aqueous humor, vitreous humor and cerebrospinal fluid (CSF) of non pigmented rabbits using serial sampling techniques and to determine if the pharmacokinetic parameters in the eye and CSF are similar. Twenty healthy male rabbits received intravenous fluconazole 20 mg/kg as a single dose or 20 mg/kg every 12 hours for 4 doses. Serum, aqueous humor, vitreous humor and CSF samples were taken 15 minutes after the initial intravenous injection and hourly thereafter for six hours. Fluconazole concentrations were determined by microbiological assay. Pharmacokinetic analyses were performed using a nonlinear least-square regression program. Fluconazole's penetration in all anatomical compartments was > 70% than in the serum. Similar elimination half-lives and time to reach maximum concentrations were noted in all compartments. While mean concentrations in each anatomical compartment were similar in animals receiving a single dose or among those at serum steady state, the mean concentrations achieved in the serum, aqueous and vitreous humors and CSF were between 1.82 and 2.17 times higher at serum steady state than following a single dose. At serum concentrations that are comparable to those in humans, the penetration of fluconazole into the noninflamed aqueous and vitreous humors and CSF were > or = 70%. The CSF and ocular pharmacokinetic parameters closely resembled each other, so that either could be used as a surrogate for the other.
Animals↗
Pharmacodynamics of fluconazole in a murine model of systemic candidiasis.
In this study we defined the pharmacodynamic parameter that optimizes outcome in deep-seated Candida albicans infections treated with fluconazole. Using a murine model of systemic candidiasis, we conducted single-dose dose-ranging studies with fluconazole to determine the dosage of this drug that resulted in a 50% reduction in fungal densities (50% effective dose [ED50]) in kidneys versus the fungal densities in the kidneys of untreated controls. We found that the ED50 of fluconazole given intraperitoneally was 4.56 mg/kg of body weight/day (95% confidence interval, 3.60 to 5.53 mg/kg/day), and the dose-response relationship was best described by an inhibitory sigmoid maximal effect (Emax) curve. To define the pharmacodynamics of fluconazole, we gave dosages lower than, approximating, and higher than the ED50 of fluconazole (range, 3.5 to 5.5 mg/kg/day, equivalent to the ED16 to the ED75) to various groups of infected animals using three dose-fractionation schedules. For each total dose of fluconazole examined, the dose-fractionation schedules optimized the ratio of the area under the concentration-time curve (AUC) to the MIC (the AUC/MIC ratio), the ratio of the maximum concentration of drug in serum (Cmax) to the MIC, and the time that the drug remained above the MIC for the infecting C. albicans isolate. Similar reductions in fungal densities in kidneys were seen between groups that received the same total dose of fluconazole in one, two, or four equally divided doses. Thus, dose-fractionation studies demonstrated that the pharmacodynamic parameter of fluconazole that best predicted outcome was the AUC/MIC ratio.
Animals↗
Pharmacokinetics of sparfloxacin in the serum and vitreous humor of rabbits: physicochemical properties that regulate penetration of quinolone antimicrobials.
We have used a recently described animal model to characterize the ocular pharmacokinetics of sparfloxacin in vitreous humor of uninfected albino rabbits following systemic administration and direct intraocular injection. The relationships of lipophilicity, protein binding, and molecular weight to the penetration and elimination of sparfloxacin were compared to those of ciprofloxacin, fleroxacin, and ofloxacin. To determine whether elimination was active, elimination rates following direct injection with and without probenecid or heat-killed bacteria were compared. Sparfloxacin concentrations were measured in the serum and vitreous humor by a biological assay. Protein binding and lipophilicity were determined, respectively, by ultrafiltration and oil-water partitioning. Pharmacokinetic parameters were characterized with RSTRIP, an iterative, nonlinear, weighted, least-squares-regression program. The relationship between each independent variable and mean quinolone concentration or elimination rate in the vitreous humor was determined by multiple linear regression. The mean concentration of sparfloxacin in the vitreous humor was 59.4% +/- 12.2% of that in serum. Penetration of sparfloxacin, ciprofloxacin, fleroxacin, and ofloxacin into, and elimination from, the vitreous humor correlated with lipophilicity (r2 > 0.999). The linear-regression equation describing this relationship was not improved by including the inverse of the square root of the molecular weight and/or the degree of protein binding. Elimination rates for each quinolone were decreased by the intraocular administration of probenecid. Heat-killed Staphylococcus epidermidis decreased the rate of elimination of fleroxacin. Penetration of sparfloxacin into the noninflamed vitreous humor was greater than that of any quinolone previously examined. There was an excellent correlation between lipophilicity and vitreous entry or elimination for sparfloxacin as well as ciprofloxacin, fleroxacin, and ofloxacin. There are two modes of quinolone translocation into and out of the vitreous humor: diffusion into the eye and both diffusion and carrier-mediated elimination out of the vitreous humor.
Animals↗
Pharmacokinetic studies of fluconazole in rabbits characterizing doses which achieve peak levels in serum and area under the concentration-time curve values which mimic those of high-dose fluconazole in humans.
We conducted steady-state pharmacokinetic studies with high-dose fluconazole with rabbits and human volunteers. We then derived mathematical equations that predict the doses of fluconazole that should be given to rabbits to produce 24-h area under the concentration-time curve values and maximum concentrations in serum that are similar to those measured for humans given 800 to 2,000 mg of fluconazole per day. These equations provide a rational basis for designing future efficacy studies with rabbits and in evaluating the strength with which results of previously conducted studies using rabbit infection models can be extrapolated to the clinic.
Animals↗
Pharmacokinetics of pentoxifylline and its metabolites in healthy mice and in mice infected with Candida albicans.
Pentoxifylline has immunomodulatory properties and has been shown to decrease organ damage and improve survival in animals with gram-negative sepsis or endotoxemia. This effect is mediated by a reduction in endotoxin-induced production of tumor necrosis factor alpha (TNF-alpha) by the host. In earlier studies, we observed an unexpected increase in mortality in mice infected with Candida albicans that were given pentoxifylline even though concentrations of TNF-alpha in serum were not affected. The current study was designed to determine whether the pharmacokinetics of pentoxifylline and its metabolites were altered in C. albicans-infected mice and, if so, whether these changes could have contributed to the increased mortality. Noninfected mice and mice infected with C. albicans were treated with pentoxifylline (60 mg/kg of body weight) intraperitoneally every 8 h. Serum was collected from animals after one (day 0), four (day 1), or seven (day 2) injections of pentoxifylline or saline (controls). The first dose was administered 6 h after C. albicans infection. Serum was pooled. Concentrations of pentoxifylline and metabolites I, IV, and V were determined by capillary gas chromatography. Renal function and hepatic profiles were assessed. Pharmacokinetic parameters (maximum concentration of pentoxifylline in serum, half-life, and area under the concentration-time curve from 0 h to infinity [AUC(0)-infinity]) for all noninfected mice were similar and did not differ from those for day 0-infected mice. For day 1-infected mice, values of these three pharmacokinetic parameters for pentoxifylline and metabolite I were increased two- to fourfold over values for noninfected and day 0-infected mice. For metabolites IV and V, the AUC(0)-infinity was increased approximately eightfold over control values. In addition, day 1-infected mice demonstrated evidence of renal and hepatic dysfunction. In summary, C. albicans infection produced marked changes in the pharmacokinetics of pentoxifylline and its metabolites in the mice. The high concentrations of pentoxifylline and its metabolites in serum attained in infected mice may have contributed to the increased mortality of mice with systemic candidiasis.
Adjuvants, Immunologic↗
Predictive value of several signs of infection as surrogate markers for mortality in a neutropenic guinea pig model of Pseudomonas aeruginosa sepsis.
Infected, neutropenic animals are used as experimental models to evaluate the relative efficacies of antimicrobial agents and host-pathogen-antibiotic interactions. In the past, these models used death as the study end point. Because of the concern about use of death as an end point, we evaluated the accuracy with which various signs of infection predicted mortality in a neutropenic guinea pig model of treated and untreated Pseudomonas aeruginosa sepsis. The potential surrogate markers studied included ruffled fur, respiratory distress, diarrhea, hunched posture, lethargy, abnormal neurologic movements (twitching, paralysis of a limb), inappetence for > 48 h, the inability to ambulate, and the inability of a supine animal to stand. In addition, we evaluated whether percentage of weight loss or change in daily food and water consumption were predictive of mortality. Animals were inspected for these signs at least every 4 h during the day and every 8 h in the evening. In treated and untreated animals, 100% of subjects that were unable to ambulate or to rise from the supine position died (positive predictive value for death was 100% for either sign). Guinea pigs that could not rise from a supine position expired between 1 and 8 h after this sign was observed. Those that could not ambulate died between 4 and 40 h after that sign was observed. In treated and untreated animals, none of the survivors manifested either sign of disease (100% specificity for each sign). However, 59% of untreated and 69% of treated animals that were ambulatory were found dead at the next observation period, underscoring the rapidity with which this infection progresses to death when it enters its final stage. No other signs of infection distinguished animals that survived or died. Thus, the inability of neutropenic, infected guinea pigs to rise from a supine position and the inability to ambulate were the only signs that accurately predicted death and, therefore, are the only signs that can be used as surrogates for death in this experimental model of P. aeruginosa sepsis.
Animals↗
Effect of pentoxifylline on the course of systemic Candida albicans infection in mice.
Pentoxifylline can decrease the production of tumour necrosis factor alpha (TNF alpha) by endotoxin-stimulated macrophages and may improve survival in animals with overwhelming bacterial sepsis. In this study various doses of pentoxifylline were administered to mice with systemic Candida albicans infection to determine its effect on serum TNF alpha levels, organ fungal burden, and host survival. Intraperitoneal injections of pentoxifylline at 20 mg/kg every 8 h did not affect these endpoints. However, fungal counts were significantly higher in kidneys of animals that received 30 and 60 mg/kg of pentoxifylline every 8 h when compared to controls. Injection of 60 mg/kg of pentoxifylline at 8 h intervals also significantly shortened mean survival from 5.8 to 3.8 days (P = 0.01). Pentoxifylline did not affect peripheral WBC counts, serum TNF alpha and interleukin-6 levels, or the density of neutrophils in tissues. In vitro, pentoxifylline decreased the production of TNF alpha by C. albicans-stimulated macrophages in a dose-dependent manner, but only at concentrations greater than 100 mg/L. In contrast, pentoxifylline suppressed TNF alpha production by endotoxin-stimulated macrophages at concentrations as low as 10 mg/L. Thus, higher doses of pentoxifylline are detrimental in systemic C. albicans infection. However, the detrimental effect is not mediated by alterations in serum TNF alpha or interleukin-6 levels or the aggregation of neutrophils in tissues.
Animals↗
Affect, attachment, memory: contributions toward psychobiologic integration.
Recent decades have seen a marked expansion in knowledge regarding human neurophysiology, and psychiatry is currently challenged with the task of integrating this information with a psychodynamic understanding of emotional life. In this paper we review portions of the relevant literature regarding the basic brain functions of affect, memory, and attachment, and we consider the implications of these data for integrated psychobiologic conceptualizations of emotional dysfunction and its treatment. In particular, data from these three areas of study point to the possibility that implicit memory of the early attachment relationship, communicated via the language of affect, is an enduring neural structure that influences both emotional self-regulation and behavior related to relatedness. Finally, we consider the implications of this proposition for the nature of psychotherapy, which from a psychobiologic view might be profitably conceptualized as a directed attachment relationship whose purpose is the revision of the implicit emotional memory of attachment.
Affect↗
Multiple determinants for growth of human immunodeficiency virus type 1 in monocyte-macrophages.
Attempts to define the genetic determinants required for efficient growth of human immunodeficiency virus type 1 (HIV-1) in monocyte-macrophages were made by constructing chimeras between two infectious clones of HIV-1 (HXB2 and LW/C), which despite only minor differences in their DNA sequence have striking differences in cell tropism. Although both of them replicate efficiently in peripheral blood mononuclear cells, HXB2 replicates extensively in permanent T cell lines but poorly in primary monocyte macrophages (T cell line tropic); the reverse is true for LW/C (macrophage tropic). The envelope proved to contain the major determinants of macrophage tropism. However, tropism determinants appeared to be scattered along the envelope. In particular, the V3 loop alone appeared to be neither necessary nor sufficient for growth in macrophages. Both vpr and nef genes appeared to play a less significant role to improve viral replication in macrophages, but only in the presence of the proper envelope sequences. HIV-1 macrophage tropism thus appears to result from the contribution of several different determinants.
Amino Acid Sequence↗
Fluconazole and amphotericin B antifungal therapies do not negate the protective effect of endogenous tumor necrosis factor in a murine model of fatal disseminated candidiasis.
In systemic candidiasis, endogenously produced tumor necrosis factor (TNF)-alpha prolongs survival of the infected host. To determine whether endogenously produced TNF-alpha has a beneficial effect beyond that provided by antifungal therapy, survival was assessed in infected mice that received fluconazole or amphotericin B alone and in combination with anti-TNF-alpha antibody. Neutralization of serum TNF-alpha did not affect survival in fluconazole recipients; however, for amphotericin B recipients, it significantly shortened mean survival. For both fluconazole and amphotericin B recipients, colony counts in organs were significantly higher in animals that also received anti-TNF-alpha antibody. Administration of anti-TNF-alpha antibody with amphotericin B or fluconazole did not affect the morphology of fungi or the inflammatory response in kidneys. This study suggests that exogenous TNF-alpha and drugs that increase the endogenous production of TNF-alpha by the host may be useful adjuncts to fluconazole and amphotericin B for the treatment of systemic candidiasis.
Amphotericin B↗
Growth of macrophage-tropic and primary human immunodeficiency virus type 1 (HIV-1) isolates in a unique CD4+ T-cell clone (PM1): failure to downregulate CD4 and to interfere with cell-line-tropic HIV-1.
Human immunodeficiency virus type 1 (HIV-1) isolates derived directly from clinical samples are usually unable to grow in cytokine-independent continuous cell lines, thus hindering the study of their biological features and their sensitivity to humoral and cellular protective immunity. To overcome these limitations, we have derived from the Hut78 T-cell line a CD4+ clone (PM1) characterized by a unique susceptibility to a wide range of HIV-1 isolates, including primary and biologically pure macrophage (M phi)-tropic isolates (e.g., HIV-1BaL), which are unable to infect other human T- or promonocytic cell lines. Both primary and M phi-tropic HIV-1 establish persistent infection in PM1, with sustained levels of virus replication for prolonged periods. Experiments with chimeric viruses containing envelope fragments of HIV-1BAL inserted into the genetic framework of HXB2, a molecular clone derived from the cell-line-tropic isolate HIV-1IIIB, showed the third hypervariable domain (V3) of gp120 to be a critical determinant of the cell line tropism of HIV-1. Nevertheless, the V3 loop of HIV-1BaL was not sufficient to confer on the chimeras a bona fide M phi tropism. The biological characteristics of HIV-1BaL and of a primary isolate (HIV-1(573)) were investigated by using the PM1 clone. Infection of PM1 by HIV-1BaL was critically dependent on the CD4 receptor, as shown by competition experiments with an anti-CD4 monoclonal antibody (OKT4a) or with soluble CD4. However, the amount of soluble CD4 required for inhibition of HIV-1BaL was approximately 100-fold higher than for HIV-1IIIB, suggesting that the affinity of HIV-1BaL for CD4 is significantly lower. Infection of PM1 with either HIV-1BaL or HIV-1(573) failed to induce downregulation of surface CD4 expression and syncytium formation. Analogous results were obtained with a chimeric virus (HXB2[BaL PvuII-BamHI]) encompassing a large portion of gp120 and gp41 of HIV-1BaL, indicating that the env genes contain critical determinants for CD4 downregulation and syncytium formation. Consistent with the lack of CD4 downregulation, persistent infection of PM1 by HIV-1BaL or HIV-1(573) failed to interfere with HIV-1IIIB superinfection, as revealed by the expression of a type-specific V3 loop epitope (M77) and by the induction of extensive syncytium formation. This lack of interference suggests that a direct viral interaction may occur in vivo between biologically diverse HIV-1 strains.(ABSTRACT TRUNCATED AT 400 WORDS)
Amino Acid Sequence↗
Comparative capacity of four antifungal agents to stimulate murine macrophages to produce tumour necrosis factor alpha: an effect that is attenuated by pentoxifylline, liposomal vesicles, and dexamethasone.
The efficacy and toxicity of certain antifungal agents may be related to their ability to induce the production of cytokines by mononuclear phagocytes. The capacity of incremental concentrations of fluconazole, 5-fluorocytosine (5-FC), amphotericin B (AmB), and liposomal AmB (LAB) to stimulate murine peritoneal and RAW 264.7 macrophages to secrete tumour necrosis factor alpha (TNF alpha) after 3, 6 and 24 h incubation was assessed by L929 cytotoxic bioassay. Fluconazole (2.5-40 mg/L) and 5-FC (25-100 mg/L) did not have a stimulatory effect. However, AmB (0.25-10 mg/L) elicited TNF alpha production by macrophages. This response was concentration-dependent, and peak TNF alpha levels were detected between 3 and 6 h. This effect was attenuated by incorporation of AmB into liposomal vesicles and by pretreating macrophages with pentoxifylline or dexamethasone. AmB I mg/L in combination with 1 x 10(6) cfu of Candida albicans stimulated peritoneal macrophages to produce similar quantities of TNF alpha as AmB alone, and two- to four-fold more TNF alpha than C. albicans alone. Thus, this study suggests that: (1) the immunomodulatory activity and toxicities of AmB, in part, may be attributed to the capacity of this drug to stimulate macrophages to secrete TNF alpha, (2) the TNF alpha that is produced by macrophages in response to AmB may have clinical relevance even in the face of C. albicans infection, and (3) the failure of fluconazole, 5-FC, and LAB to elicit a TNF alpha response may explain their improved side-effect profiles.
Amphotericin B↗