Anti-toxoplasma activities of 24 quinolones and fluoroquinolones in vitro: prediction of activity by molecular topology and virtual computational techniques

The apicoplast, a plastid-like organelle of Toxoplasma gondii, is thought to be a unique drug target for quinolones. In this study, we assessed the in vitro activity of quinolones against T. gondii and developed new quantitative structure-activity relationship models able to predict this activity. The anti-Toxoplasma activities of 24 quinolones were examined by means of linear discriminant analysis (LDA) using topological indices as structural descriptors. In parallel, in vitro 50% inhibitory concentrations (IC(50)s) were determined in tissue culture. A multilinear regression (MLR) analysis was then performed to establish a model capable of classifying quinolones by in vitro activity. LDA and MLR analysis were applied to virtual structures to identify the influence of each atom or substituent of the quinolone ring on anti-Toxoplasma activity. LDA predicted that 20 of the 24 quinolones would be active against T. gondii. This was confirmed in vitro for most of the quinolones. Trovafloxacin, grepafloxacin, gatifloxacin, and moxifloxacin were the quinolones most potent against T. gondii, with IC(50)s of 0.4, 2.4, 4.1, and 5.1 mg/liter, respectively. Using MLR analysis, a good correlation was found between measured and predicted IC(50)s (r(2) = 0.87, cross-validation r(2) = 0.74). MLR analysis showed that the carboxylic group at position C-3 of the quinolone ring was not essential for anti-Toxoplasma activity. In contrast, activity was totally dependent on the presence of a fluorine at position C-6 and was enhanced by the presence of a methyl group at C-5 or an azabicyclohexane at C-7. A nucleophilic substituent at C-8 was essential for the activity of gatifloxacin and moxifloxacin.

Prediction of quinolone activity against Mycobacterium avium by molecular topology and virtual computational screening

We conducted a quantitative structure-activity relationship study using a database of 158 quinolones previously tested against Mycobacterium avium-M. intracellulare complex in order to develop a model capable of predicting the activity of new quinolones against the M. avium-M. intracellulare complex in vitro. Topological indices were used as structural descriptors and were related to anti-M. avium-M. intracellulare complex activity by using the linear discriminant analysis (LDA) statistical technique. The discriminant equation thus obtained correctly classified 137 of the 158 quinolones, including 37 of a test group of 44 randomly chosen compounds. This model was then applied to 24 quinolones, including recently developed fluoroquinolones, whose MICs were subsequently determined in vitro by using the Alamar blue microplate assay; the biological results confirmed the model's predictions. The MICs of these 24 quinolones were then treated by multilinear regression (MLR) to establish a model capable of classifying them according to their in vitro activities. Using this model, a good correlation between measured and predicted MICs was found (r(2) = 0.88; r(2)(cv) [cross-validation correlation] = 0.82). Moxifloxacin, sparfloxacin, and gatifloxacin were the most potent against the M. avium- M. intracellulare complex, with MICs of 0.2, 0.4, and 0.9 microg/ml, respectively. Finally, virtual modifications of these three drugs were evaluated in LDA and MLR models in order to determine the importance of different substituents in their activity. We conclude that the combination of molecular-topology methods, LDA, and MLR provides an excellent tool for the design of new quinolone structures with enhanced activity.

Factors predictive of disease progression and death in AIDS-related Kaposi's sarcoma

BACKGROUND

The natural history of Kaposi's sarcoma (KS) is poorly documented. We attempted to identify factors predictive of progression and survival in HIV-infected patients with KS and CD4+ cell counts greater than 100/microL.

PATIENTS AND METHODS

We studied retrospectively 78 HIV-infected patients diagnosed as having KS between 1989 and 1995. The following variables were assessed as potential predictors of progression and death, in a Cox proportional hazards model: age, sex, ethnic group, transmission group, site of the first KS lesions, duration of KS, concomitant opportunistic infections or malignancies, antiretroviral drug therapy (excluding protease inhibitors), antiherpes treatments, neutrophil counts, CD4+ and CD8+ cell counts, plasma HIV load, p24 antigenaemia, beta2-microglobulinaemia and immunoglobin A and G serum levels.

RESULTS

During a median follow-up of 22 months (3-81 months), KS progressed in 66 of the 78 patients. The median survival time after progression was 68 months (9-126 months). Multivariate analysis identified only visceral KS, a high neutrophil count and a high serum immunoglobulin (Ig) level as independent predictors of progression (P < 0.05). Previous and concomitant opportunistic diseases (P = 0.003) and low CD4+ cell counts (P = 0.013) were independently associated with shorter survival; in contrast KS therapy did not independently influence survival.

CONCLUSION

Progression of KS is predicted by markers of KS severity, while overall survival is best predicted by markers of immunodeficiency (opportunistic diseases and the CD4+ cell count).

Long-term outcome and treatment modifications in a prospective cohort of human immunodeficiency virus type 1-infected patients on triple-drug antiretroviral regimens. Triest Cohort Investigators

We designed a cohort in order to assess the long-term effects of triple-drug antiretroviral combinations in 608 patients infected with human immunodeficiency virus type 1 (HIV-1). We recruited patients who had been previously treated with nucleoside analogues as well as treatment-naive patients who were starting triple-drug antiretroviral combinations consisting of nucleoside analogues, either alone or in combination with a protease inhibitor. After a median follow-up time of 22 months, the incidence rates of acquired immune deficiency syndrome-defining events and death were, respectively, 6.9 (95% confidence interval [CI], 5.3-8.8) and 2.9 (95% CI, 1.9-4.2) per 100 person-years. Advanced clinical stage of disease (P=.004), a low CD4(+) cell count (P=.002), and a low quality-of-life score (P=.001) at baseline were independent predictors of clinical progression. The initial triple-drug combination was modified a total of 647 times in 321 patients. The only independent predictor of treatment modification was previous exposure to a nucleoside analogue in patients who did not receive a new nucleoside analogue at inclusion (P=.001). Plasma HIV RNA values below 500 copies/mL were obtained in 88% of the treatment-naive patients and in 57% of the previously treated patients (P<.001). Compared with previously treated patients who received > or = 1 new nucleoside analogue at enrollment, previously treated patients who did not receive a new nucleoside analogue at enrollment were twice as likely to have plasma HIV RNA values >500 copies/mL at the last visit (adjusted odds ratio [OR], 1.8; 95% confidence interval [CI], 1.2-2.8), and the antiretroviral-naive patients were significantly less likely to have plasma HIV RNA values >500 copies/mL at the last visit (adjusted OR, 0.2; 95% CI, 0.1-0.4).

Radiosensitivity in Nijmegen Breakage Syndrome cells is attributable to a repair defect and not cell cycle checkpoint defects

Cells derived from Nijmegen Breakage Syndrome (NBS) patients display radiosensitivity and cell cycle checkpoint defects. Here, we examine whether the radiosensitivity of NBS cells is the result of a repair defect or whether it can be attributed to impaired checkpoint arrest. We report a small increased fraction of unrejoined double strand breaks and, more significantly, increased chromosome breaks in noncycling NBS cells at 24 h after irradiation. One of the NBS lines examined (347BR) was atypical in showing a nearly normal checkpoint response. In contrast to the mild checkpoint defect, 347BR displays marked y-ray sensitivity similar to that shown by other NBS lines. Thus, the gamma-ray sensitivity correlates with the repair defect rather than impaired checkpoint control. Taken together, the results provide direct evidence for a repair defect in NBS cells and are inconsistent with the suggestion that the radiosensitivity is attributable only to impaired checkpoint arrest. 347BR also displays elevated spontaneous damage that cannot be attributed to impaired G2-M arrest, suggesting a function of Nbsl in decreasing or limiting the impact of spontaneously arising double strand breaks.

Phase II placebo-controlled trial of fozivudine tidoxil for HIV infection: pharmacokinetics, tolerability, and efficacy

Fozivudine tidoxil (FZD) is a thioether lipid-zidovudine (ZDV) conjugate with anti-HIV activity demonstrated in vitro and in pilot phase I studies. To assess its safety, efficacy and pharmacokinetics, we conducted a multicenter, randomized, double-blind, placebo-controlled trial of FZD monotherapy in 72 HIV-infected patients who had not previously received antiretroviral therapy. In each dosage group (200 mg daily, 400 mg daily, 200 mg twice daily, 800 mg daily, 400 mg twice daily, and 600 mg twice daily), 12 patients were randomized to receive in a 10:2 ratio either FZD or a placebo for 4 weeks. Overall, FZD was well tolerated in all dosage groups; only 1 patient discontinued the drug, because of a moderate rise in aminotransaminase activity. HIV viral load fell in all the patients who were receiving FZD, except in the 200 mg daily group. The largest decrease (-0.67 log10) was observed in the 600 mg twice daily group. The plasma half-life was significantly longer (approximately 3.8 hours) than that of the parent drug ZDV. Exposure to ZDV, as reflected by the area under the time-concentration curve, was much lower after FZD than after ZDV administration. FZD thus appears to be as effective as and potentially better tolerated than ZDV during short-term administration and has the advantage of once daily intake.

Prospective study of CD8+ lymphocyte activation in relation to viral load in HIV-infected patients with > or = 400 CD4+ lymphocytes per microliter

To investigate the temporal relationship between CD8+ lymphocyte phenotypic alterations, the CD4+ T cell decline, and plasma HIV RNA levels during the natural history of HIV infection, 33 treatment-naive HIV-infected patients with > or =400 CD4+ cells/microl were studied prospectively for 3 years. During the study period, 20 patients remained untreated, and only 6 received more than 6 months of therapy. A significant relationship was found between changes in plasma HIV RNA and changes in the proportion of CD38+CD8+ cells. Conversely, the number of CD4+ T cells lost per year was strongly related to the increase in the proportion of CD28-CD8+ T cells. A strong relationship between mean yearly changes in CD4+ T cell numbers and changes in HIV RNA was also observed. CD4+ T cell changes were associated with changes in both viral load and CD8+ T cell activation. These results provide support for the use of both virologic and immunologic parameters for prognosis and management during HIV infection.

Restoration of normal interleukin-2 production by CD4+ T cells of human immunodeficiency virus-infected patients after 9 months of highly active antiretroviral therapy

The present study investigated immune restoration in patients at intermediate stages of human immunodeficiency virus (HIV) disease after initiation of highly active antiretroviral therapy (HAART). A progressive increase in both memory and naive CD4+ T cells was observed from the first weeks of therapy, concomitant with a decrease in the expression of activation markers on CD8+ T cells. The early-activation marker CD69 remained, however, overexpressed on T cells after suboptimal stimulation in vitro, indicative of persistent immune activation. The percentage of interleukin (IL)-2-producing CD4+ T cells significantly increased from 9 months of HAART. In most patients, CD4+ T cells recovered an ability to produce IL-2 on stimulation, similar to that of HIV-seronegative controls. Reversal of T-cell anergy may be a key event in immune restoration for achieving long-term clinical benefit with HAART.

Monocyte expression of adhesion molecules in HIV-infected patients: variations according to disease stage and possible pathogenic role

We used flow cytometry to study the expression of adhesion molecules at the cell surface and actin polymerization of whole-blood monocytes in 35 HIV-infected patients at different stages of the disease. Monocytes were activated in vivo, as demonstrated by increased expression of the adhesion molecule CD11b/CD18, reduced L-selectin antigen expression, and increased actin polymerization. These abnormalities were present in asymptomatic patients with CD4+ cell counts greater than 500/microl and did not increase with disease progression or viral load. Sialyl-Lewis x and CD31 expression at the monocyte surface was normal in asymptomatic and symptomatic non-AIDS patients. In contrast expression of both molecules was strongly reduced in patients with AIDS. This change, despite normal maximal CD11b/CD18 expression and normal maximal actin polymerization, could contribute to the increased susceptibility to bacterial infections in AIDS. In contrast enhanced monocyte activation may promote their transendothelial migration in non-AIDS patients, possibly explaining the macrophage infiltration that can occur early in the disease.

T cell changes after combined nucleoside analogue therapy in HIV primary infection

OBJECTIVE

To characterize the immune changes after treatment of acute HIV-1 infection with triple nucleoside analogue therapy.

DESIGN

Immunological and virological parameters were monitored from day 0 to weeks 36-44 in eight patients [median CD4 cells = 451 cells/microl (range: 149-624), viral load = 4.8 log10 copies/ml (range: 6.5-3.3)] who started at time of primary HIV infection (PHI) a therapy including zidovudine (ZDV), didanosine (ddl), and lamivudine (3TC).

METHODS

Lymphoid subsets were evaluated on peripheral blood lymphocytes by four-colour flow cytometry using a panel of mAbs directed against differentiation and activation markers.

RESULTS

We observed a median -2.1 (range: -1; -3.3) log10 copies/ml viral load decrease and a median +158 cells/microl (range: +7 to +316) CD4 cell count increase at week 4 reaching normal CD4 cell count values of 761 CD4 cells/microl (range: 389-1153) at weeks 36-44. Virus undetectability was obtained at week 24 for all subjects. A rapid CD4 T cell amplification involved both memory and naive CD4 T cells. This was associated with a very rapid and significant decrease in activation markers [human leukocyte antigen-DR (HLA-DR), CD38] on both CD4 and CD8 T cell subsets together with a CD8+CD28+ cell increase as early as week 4.

CONCLUSIONS

These results show that early therapy with nucleoside analogues can correct the immunological abnormalities observed in CD4 and CD8 T cell subsets at the time of PHI. This early kinetics in T cell recovery appears to be faster than in established disease.

Redox and activation status of monocytes from human immunodeficiency virus-infected patients: relationship with viral load

Monocytes are precursors of tissue macrophages, which are major targets of human immunodeficiency virus type 1 (HIV-1) infection. Although few blood monocytes are infected, their resulting activation could play a key role in the pathogenesis of HIV disease by modulating their transendothelial migration and inducing the production of reactive oxygen species (ROS). ROS participate in chronic inflammation, HIV replication, and the apoptosis of immune system cells seen in HIV-infected subjects. Published data on monocyte activation are controversial, possibly because most studies have involved monocytes isolated from their blood environment by various procedures that may alter cell responses. We therefore used flow cytometry to study, in whole blood, the activation and redox status of monocytes from HIV-infected patients at different stages of the disease. We studied the expression of adhesion molecules, actin polymerization, and cellular levels of H2O2, Bcl-2, and thioredoxin. Basal H2O2 production correlated with viral load and was further enhanced by bacterial N-formyl peptides and endotoxin. The enhanced H2O2 production by monocytes from asymptomatic untreated patients with CD4(+) cell counts above 500/microliter was associated with a decrease in the levels of Bcl-2 and thioredoxin. In contrast, in patients with AIDS, Bcl-2 levels returned to normal and thioredoxin levels were higher than in healthy controls. Restoration of these antioxidant and antiapoptotic molecules might explain, at least in part, why monocyte numbers remain relatively stable throughout the disease. Alterations of adhesion molecule expression and increased actin polymerization could play a role in transendothelial migration of these activated monocytes.

AIDS-related primary pulmonary lymphoma

We describe 12 cases of AIDS-related primary pulmonary lymphoma occurring between 1986 and 1996 in a large French cohort of HIV-infected patients. Diagnostic criteria were: (1) histologically proven lymphomatous pulmonary involvement; (2) absence of mediastinal and/or hilar adenopathy on chest radiography; (3) absence of extrathoracic lymphoma extension. All patients were severely immunodeficient at the time of diagnosis. All but one patient presented with B and/or nonspecific respiratory symptoms. Chest radiography showed one or more marginated nodule(s) or large mass. CT scan showed a cavitary lesion in five patients. No lymph node enlargement or specific pleural effusion was detected. Transthoracic needle biopsies were performed in 10 patients and avoided open-lung biopsy for the diagnosis of lymphoma in five patients. All but one of the primary pulmonary lymphoma were high-grade B-cell non-Hodgkin's lymphomas. Using antilatent membrane protein-1 antibodies and an Epstein-Barr-Virus-encoded RNA transcript-specific probe, latent EBV infection of tumor cells was demonstrated in every case. All but one of the patients received chemotherapy. The median survival time was 4 mo, and no patient was still alive at the cut-off date for this analysis. Progessive pulmonary lymphoma was the main cause of death, but infections were also frequent.

Effect of indinavir on HIV-related wasting

OBJECTIVE

To study the effect of the protease inhibitor indinavir on body weight and body composition of subjects with HIV-related wasting.

DESIGN

Prospective measurement of body weight in patients who had wasting and were treated with indinavir. A subgroup of 16 representative patients also underwent a metabolic study that included measurements of body composition (skinfolds and bioelectrical impedance) and food intake. Seven from this subgroup who did not have chronic diarrhoea also underwent indirect calorimetry for measurement of resting energy expenditure; the nine patients with wasting and chronic diarrhoea had measurements of faecal losses and intestinal permeability using the lactulose-mannitol test.

SETTING

A tertiary care university hospital.

PATIENTS

Two hundred and fourteen HIV-infected patients with wasting (less than 95% of usual body weight) had their body weight measured at day 0; 186 patients had a second body weight measurement within the first 100 days of treatment, and 160 patients were weighed a third time, at a median of 176 days.

RESULTS

Body weight increased significantly (P < 0.0001) during treatment, whatever the degree of weight loss at baseline. After a median of 176 days on treatment, body weight had increased in 119 out of the 160 patients followed (74.4%; mean weight gain, 6.3+/-SD 3.8 kg; range, 1-18 kg), had not changed in 13 (8.1%) and had fallen in 28 (17.5%; mean weight loss, 4.2+/-3.0 kg; range, 1-12 kg), relative to baseline. Overall, 119 out of the 214 patients (55.6%) from the initial population gained weight. Fat mass, fat-free mass and body cell mass increased significantly in the 16 patients who underwent metabolic studies, together with energy, protein and lipid intake. In the patients with chronic diarrhoea, intestinal permeability improved but there was no change in intestinal losses. In patients who had wasting but not chronic diarrhoea, resting energy expenditure did not change significantly. Body weight changes correlated with changes in the CD4+ cell count (r = 0.882; P = 0.00001) and, to a lesser extent, with changes in the viral load (r = -0.466; P = 0.047).

CONCLUSION

Indinavir significantly improved the nutritional status of these patients with HIV-related wasting.

Changes in blood CD8+ lymphocyte activation status and plasma HIV RNA levels during antiretroviral therapy

OBJECTIVE

To analyse the relationship between CD8+ lymphocyte phenotype alterations and plasma HIV RNA levels in HIV-infected patients treated with the zidovudine-didanosine combination.

METHODS

A total of 30 HIV-infected patients who had never received antiretroviral therapy and who were starting treatment with a combination of zidovudine and didanosine were prospectively studied. Multiparameter flow cytometric analysis of CD8+ lymphocytes and plasma HIV RNA determination were performed on day 0, day 15 and monthly from months 1 to 6.

RESULTS

Patients were divided into three categories according to the time-course of plasma HIV RNA levels. In 14 patients, an early and sustained fall in plasma HIV RNA to below the detection limit (500 copies/ml) was observed; in 10 patients, the fall was transient; in six patients, plasma HIV RNA was always detectable (non-responders). The mean CD4+ lymphocyte gain was 120 x 10(6)/l at month 6 in sustained and transient responders, and 55 x 10(6)/l in non-responders. A significant fall in the proportion of CD8+ lymphocytes with an activated phenotype was observed only in the two groups of responders, and was higher in the sustained responders (CD38+HLA-DR+, -56.8%; CD38+CD45RO+, -54.0%; HLA-DR+CD45RO+, -48.4%; CD38+CD28-, -47.3%).

CONCLUSION

A fall in the proportion of activated CD8+ lymphocytes is associated with the disappearance of HIV RNA from plasma during antiretroviral therapy. Undetectable plasma HIV RNA is not associated with a return to normal CD8+ lymphocyte activation status after 6 months of treatment, suggesting that viral replication persists in lymphoid tissues.

Opposite base-dependent excision of 7,8-dihydro-8-oxoadenine by the Ogg1 protein of Saccharomyces cerevisiae

The yOgg1 protein of Saccharomyces cerevisiae is a DNA glycosylase/AP lyase that excises guanine lesions such as 7,8-dihydro-8-oxoguanine (8-OxoG) and 2,6-diamino-4-hydroxy-5-N-methylformamidopyrimidine (me-Fapy-G) and incises apurinic/apyrimidinic sites (AP sites) in damaged DNA. The yOgg1 protein displays a marked preference for DNA duplexes containing 8-OxoG or AP sites placed opposite cytosine. In this paper, we show that yOgg1 can also excise an adenine lesion, 7,8-dihydro-8-oxoadenine (8-OxoA), when paired with cytosine or 5-methylcytosine. In contrast, yOgg1 does not release 8-OxoA when placed opposite thymine, adenine, guanine or uracil. The specificity constants (Kcat/Km) for repair of 8-OxoG/C and 8-OxoA/C duplexes are (50 +/- 18) x 10(-3) and (13 +/- 3) x 10(-3)/min/nM, respectively. The catalytic mechanism for strand cleavage at 8-OxoA/C involves excision of 8-OxoA by the DNA glycosylase activity of yOgg1, followed by incision at the newly formed AP site via a beta-elimination reaction. Furthermore, cleavage of 8-OxoA/C involves formation of a reaction intermediate that is converted into a stable covalent adduct in the presence of sodium borohydride (NaBH4). The yOgg1 protein binds strongly to the 8-OxoA/C duplex, as demonstrated by an apparent dissociation constant (Kdapp) value of 45 nM, as determined by gel mobility shift assay. In contrast, the yOgg1 protein has a very low binding affinity for the 8-OxoA/T duplex, a Kdapp value of 680 nM, which in turn can explain the lack of repair of 8-OxoA in this duplex. The capacity of other DNA glycosylases/AP lyases to repair 8-OxoA has also been investigated. The results show that human hOgg1 protein efficiently repairs 8-OxoA placed opposite cytosine or 5-methylcytosine. On the other hand, the Fpg protein of Escherichia coli cleaves 8-OxoA/C at a very slow rate as compared with yOgg1.

Drug evaluation of concurrent Pneumocystis carinii, Toxoplasma gondii, and Mycobacterium avium complex infections in a rat model

We present a new experimental model for the simultaneous evaluation of the activities of drugs against Pneumocystis carinii, Toxoplasma gondii, and Mycobacterium avium complex infections. Rats latently infected with P. carinii were challenged with the MO-1 strain of M. avium and then immunosuppressed with corticosteroids for 7 weeks. At week 5 the RH strain of T. gondii was intraperitoneally injected. Organs were examined for the three pathogens after death or killing of the animals at week 7. Without treatment, rats challenged with T. gondii died with pulmonary P. carinii infection and disseminated T. gondii and M. avium infections. In order to assess the value of the model for evaluation of the activities of drugs, we administered by oral gavage for 7 weeks drugs or combinations of drugs selected for their individual efficacies against at least one pathogen. We found that clarithromycin with sulfamethoxazole, clarithromycin with atovaquone, roxithromycin with sulfamethoxazole or dapsone, and rifabutin with atovaquone were effective against the three infections, whereas PS-15 with dapsone and trimethoprim with sulfamethoxazole were active against Toxoplasma and Pneumocystis infections only. This triple-infection rat model offers a new tool for the simultaneous evaluation of the activities of drugs against three of the major opportunistic infections occurring in immunosuppressed individuals.

Experimental evaluation of roxithromycin combined with dapsone or sulphamethoxazole on Pneumocystis carinii and Toxoplasma gondii dual infections in a rat model

We have developed a dual infection model in immunosuppressed rats for evaluating drugs against Pneumocystis carinii and Toxoplasma gondii, two important opportunistic pathogens in patients with AIDS. Using this model, we reported that the macrolide roxithromycin was effective at a daily dose of 400 mg/kg in preventing the development of T. gondii infection but did not have a prophylactic effect against P. carinii in the same rats. A lower dose (200 mg/kg/day) had only marginal effects. Extending these experiments, we have now shown that roxithromycin at doses of 400 or 200 mg/kg/day combined with dapsone at doses of 5, 25 or 50 mg/kg/day completely prevented the development of T. gondii infection, with no parasites being detected in any of the tissues sampled. Roxithromycin at either dose combined with dapsone at 25 or 50 mg/kg/day was also effective in preventing the development of P. carinii infection in the lungs. The lowest dose of dapsone (5 mg/kg/day) was not fully effective. Pyrimethamine-dapsone, a combination used clinically, was tested in the same experiment, and gave results comparable to those with roxithromycin-dapsone combinations. In a further experiment combining roxithromycin with sulphamethoxazole, roxithromycin was effective in preventing the T. gondii infection, even when given at only 200 mg/kg/day with 20 mg/kg/day of sulphamethoxazole. When the dose of sulphamethoxazole was reduced to 2 mg/kg/day and given with roxithromycin 200 mg/kg/day, T. gondii infection developed in two of the five rats treated. P. carinii infection was prevented by sulphamethoxazole at 20 mg/kg/day but not completely by 2 mg/kg/day. Roxithromycin also has activity against Mycobacterium avium, another important cause of opportunistic infections in AIDS patients, and the compound penetrates mammalian cells well. Taken together with the favourable pharmacokinetic profile of roxithromycin, these results suggest that it may have a clinical utility, when used with other agents, in controlling the development of opportunistic infections caused by M. avium complex, T. gondii and P. carinii in HIV-infected individuals.

Substrate specificity of the Ogg1 protein of Saccharomyces cerevisiae: excision of guanine lesions produced in DNA by ionizing radiation- or hydrogen peroxide/metal ion-generated free radicals

We have investigated the substrate specificity of the Ogg1 protein of Saccharomyces cerevisiae (yOgg1 protein) for excision of modified DNA bases from oxidatively damaged DNA substrates using gas chromatography/isotope dilution mass spectrometry. Four DNA substrates prepared by treatment with H2O2/Fe(III)-EDTA/ascorbic acid, H2O2/Cu(II) and gamma-irradiation under N2O or air were used. The results showed that 8-hydroxyguanine (8-OH-Gua) and 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyGua) were efficiently excised from DNA exposed to ionizing radiation in the presence of N2O or air. On the other hand, 8-OH-Gua and FapyGua were not excised from H2O2/Fe(III)-EDTA/ascorbic acid-treated and H2O2/Cu(II)-treated DNA respectively. Fourteen other lesions, including the adenine lesions 8-hydroxyadenine and 4,6-diamino-5-formamidopyrimidine, were not excised from any of the DNA substrates. Kinetics of excision significantly depended on the nature of the damaged DNA substrates. The findings suggest that, in addition to 8-OH-Gua, FapyGua may also be a primary substrate of yOgg1 in cells. The results also show significant differences between the substrate specificities of yOgg1 protein and its functional analog Fpg protein in Escherichia coli.

Pericardial effusion and AIDS: benefits of surgical drainage

OBJECTIVES

During the last few years, AIDS has been the main cause of large pericardial effusions in urban settings. We have therefore had to perform surgical pericardial drainage for diagnostic and/or therapeutic purposes in AIDS patients. This study was designed to establish the diagnostic and therapeutic yield of pericardial drainage for these patients.

METHODS

We retrospectively reviewed the data of the 13 AIDS patients with a pericardial effusion, referred to our surgical department between December 1989 and December 1996 for surgical drainage and pericardial biopsy.

RESULTS

Cytological studies and searches for bacteria, mycobacteria and parasites were all negative. The histology of the 13 pericardial biopsies disclosed three pericardial locations of a Kaposi's sarcoma (all three patients had a pre-existent extra-cardiac location of this sarcoma) and one pericardial location of an already known immature mediastinal teratoma. In the nine other cases, the lesions were aspecific. Four patients died of multivisceral failure within 30 days of surgery. For the survivors, surgical drainage afforded relief and there were no clinical signs of recurrent effusion.

CONCLUSIONS

The cause of pericardial effusion in AIDS is still often unknown, even after pericardial biopsy. Here, aspecific pericarditis was the most common diagnosis. Although the prognosis of such effusion in these patients is known to be poor, surgical drainage provided relief for those who survived the post-operative period.

Intravenous methotrexate for primary central nervous system non-Hodgkin's lymphoma in AIDS

OBJECTIVE

To evaluate high-dose intravenous methotrexate in primary central nervous system (CNS) lymphoma in HIV-infected patients.

DESIGN

An uncontrolled pilot trial.

SETTING

An infectious diseases department in Paris, France.

PATIENTS

All consecutive AIDS patients with primary CNS lymphoma attending the same unit from August 1994 to March 1996.

INTERVENTIONS

Methotrexate was intravenously administered at a dose of 3 g/m2 every 14 days with leucovorin rescue. A maximum of six cycles was planned. Steroids were given to all patients and haematological growth factors were administered as required.

MAIN OUTCOME MEASURES

Rate of response, time to response and survival.

RESULTS

Fifteen patients (10 with histological documentation) were recruited. The median time since clinical onset was 27 days (range, 7-69 days), median Karnofsky score was 51 (range, 30-70), and mean CD4+ cell count was 30 +/- 19 x 10(6)/l (range, 7-69 x 10(6)/l). Complete responses, defined as clinical improvement and disappearance of contrast-enhancing brain abnormalities on computed tomography or magnetic resonance imaging, were obtained in seven out of 15 patients (three out of 10 patients with histological diagnosis and four out of five patients without histological confirmation). The Karnofsky score of these seven patients improved to 80 +/- 10 (range, 70-100). The mean time taken to respond was 62 +/- 20 days (range, 45-90 days). One patient relapsed at 6 months. Six patients failed to respond, and two died of severe sepsis on days 15 and 45. The median survival time was 290 days (range, 11-570 days): 73 days (range, 11-570 days) in the 10 patients with histological diagnosis, and 347 days (range, 286-409 days) in the five patients without histological confirmation. Side-effects occurred in 10 patients, with gastrointestinal disorders in five, mucositis and skin rash in two, and fever in three patients; however, these events were mild and did not require cycle postponement or dose changes. No cognitive dysfunction occurred.

CONCLUSION

Methotrexate appears to be an attractive alternative to radiation therapy for primary CNS lymphoma and is associated with a far greater improvement in quality of life relative to historical series of radiation therapy.

Repair of oxidized DNA bases in the yeast Saccharomyces cerevisiae

An essential requirement for all organisms is to maintain its genomic integrity. Failure to do so, in multicellular organisms such as man, can lead to degenerative pathologies such as cancer and aging. Indeed, a very low spontaneous mutation rate is observed in eukaryotes, suggesting either an inherent stability of the genome or efficient DNA repair mechanisms. In fact, DNA is subjected to unceasing attacks by a variety of endogenous and environmental reactive chemical species yielding a multiplicity of DNA damage, the deleterious action of which is counteracted by efficient repair enzymes. Reactive oxygen species formed in cell as by-products of normal metabolism are probably the major source of endogenous DNA damage. Amongst oxidative damage, base modifications constitute an important class of lesions whose lethal or mutagenic action has been established. Oxidatively damaged DNA bases are mostly repaired by the base excision repair pathway (BER) in prokaryotes and eukaryotes. However, the nucleotide excision repair pathway (NER) may also play a role in the repair of some oxidized bases in DNA. Here, we describe repair pathways implicated in the removal of oxidized bases in Saccharomyces cerevisiae. Yeast is a simple organism that can be used as a paradigm for DNA repair in all eukaryotic cells. S cerevisiae possesses three DNA glycosylases that catalyze the excision of oxidized bases from damaged DNA: the Ogg1, Ntg1 and Ntg2 proteins. The aim of this review is to summarize recent findings dealing with the formation, the biological consequences and the repair of oxidized DNA bases in S cerevisiae.

Ribavirin therapy for adenovirus pneumonia in an AIDS patient

We report the effectiveness of ribavirin in an AIDS patient with multinodular pneumonia due to adenovirus. A 38-year-old AIDS patient who experienced multiple opportunistic infections and whose CD4 lymphocyte count was 5/mm3 developed bilateral nodular lung opacities. Lung surgical biopsy yielded necrotizing pneumonitis with characteristic nuclear inclusions and positive immunocytology with adenovirus antibodies. Marked clinical and radiological improvement was obtained after intravenous then oral ribavirin. Ribavirin was discontinued after 40 d because of anemia. Relapse of pneumonia with respiratory distress led to death 8 mo later. This observation illustrates a rarely reported pulmonary opportunistic infection in AIDS and the potential value of ribavirin therapy for adenovirus pneumonia.

The Ogg1 protein of Saccharomyces cerevisiae: a 7,8-dihydro-8-oxoguanine DNA glycosylase/AP lyase whose lysine 241 is a critical residue for catalytic activity

The OGG1 gene of Saccharomyces cerevisiae codes for a DNA glycosylase that excises 7,8-dihydro-8- oxoguanine (8-OxoG) and 2,6-diamino-4-hydroxy-5- N -methylformamidopyrimidine (Fapy) from damaged DNA. In this paper, we have analysed the substrate specificity and the catalytic mechanism of the Ogg1 protein acting on DNA subtrates containing 8-OxoG residues or apurinic/apyrimidinic (AP) sites. The Ogg1 protein displays a marked preference for DNA duplexes containing 8-OxoG placed opposite a cytosine, the rank order for excision of 8-OxoG and cleavage efficiencies being 8-OxoG/C >8-OxoG/T >>8-OxoG/G and 8-OxoG/A. The cleavage of the DNA strand implies the excision of 8-OxoG followed by abeta-elimination reaction at the 3'-side of the resulting AP site. The Ogg1 protein efficiently cleaves a DNA duplex where a preformed AP site is placed opposite a cytosine (AP/C). In contrast, AP/T, AP/A or AP/G substrates are incised with a very low efficiency. Furthermore, cleavage of 8-OxoG/C or AP/C substrates implies the formation of a reaction intermediate that is converted into a stable covalent adduct in the presence of sodium borohydre (NaBH4). Therefore, the Ogg1 protein is a eukaryotic DNA glycosylase/AP lyase. Sequence homology searches reveal that Ogg1 probably shares a common ancestor gene with the endonuclease III of Escherichia coli. A consensus sequence indicates a highly conserved lysine residue, K120 of endonuclease III or K241 of Ogg1, respectively. Mutations of K241 to Gln (K241Q) and Arg (K241R) have been obtained after site directed mutagenesis of OGG1. Mutation K241Q completely abolishes DNA glycosylase activity and covalent complex formation in the presence of NaBH4. However, the K241Q mutant still binds DNA duplexes containing 8-OxoG/C. In contrast, K241R mutation results in a catalytically active form of Ogg1. These results strongly suggest that the free amino group of Lys241 is involved in the catalytic mechanism of the Ogg1 protein.