Biomedical subjects

H Mitsuya

Publications and source records attributed to H Mitsuya.

At least 109 records · Page 6Linked to original sources

PubMed1995

Vertical transmission of human immunodeficiency virus type 1: autologous neutralizing antibody, virus load, and virus phenotype.

OBJECTIVE: To evaluate immunologic and virologic correlates of vertical transmission of human immunodeficiency virus type 1 (HIV-1). DESIGN: Case-control study. PATIENTS: Women who were prospectively enrolled in a natural history study of HIV-1 infection in women and infants. Sixteen HIV-1-infected women whose infants became infected were matched by CD4+ cell percentage and use of zidovudine during pregnancy with women whose infants did not become infected. MEASUREMENTS: Maternal autologous neutralizing antibody, virus load determined by RNA-polymerase chain reaction (RNA-PCR), and virus phenotype. RESULTS: Most women in both groups had low titers of autologous neutralizing antibody, and no difference in neutralizing titers was observed (range, < 4 to 181 in both groups). The HIV-1 copy number in maternal plasma was not significantly different in the two groups but was inversely correlated with maternal CD4+ cell percentage (p < 0.005). Five women in the transmitting group and four in the non-transmitting group had syncytium-inducing (SI) phenotype virus. Two infected infants had SI phenotype virus. The SI phenotype virus was associated with a greater HIV-1 copy number in maternal plasma (p < 0.05) and an increase in the mortality rate for the infants (p < 0.01). CONCLUSIONS: In women matched for CD4+ cell percentage, low titers of autologous neutralizing antibody, high virus load, and SI phenotype virus were not associated with an increased risk of transmission of HIV-1 to their infants.

Acquired Immunodeficiency Syndrome↗

PubMed1995

Human immunodeficiency virus type 1 (HIV-1) viremia changes and development of drug-related mutations in patients with symptomatic HIV-1 infection receiving alternating or simultaneous zidovudine and didanosine therapy.

The changes in viremia levels and the development of drug-related mutations were examined in 26 patients with symptomatic human immunodeficiency virus type 1 (HIV-1) infection participating in a randomized trial comparing alternating (A) and simultaneous (S) regimens of zidovudine and didanosine therapy. Patients on both arms had significant reduction in serum RNA copies from baseline throughout the 2 years of study. Significant differences between the two arms were demonstrated over the first 2-3 months of therapy. Analyses with nested polymerase chain reaction revealed that the emergence of the didanosine-related position 74 Leu-->Val mutation was significantly blocked in both regimens, while the zidovudine-related mutation at codon 215 was not affected. Determination of the overall durability of the antiviremic effect of the A and S regimens of zidovudine and didanosine and clinical implications of the results require further research.

Adult↗

PubMed1995

Five-year follow-up of a phase I study of didanosine in patients with advanced human immunodeficiency virus infection.

Starting in 1988, 72 patients with advanced human immunodeficiency virus (HIV) infection were enrolled in a phase I study of didanosine at the National Cancer Institute. Beginning in 1992, patients with decreases in CD4 cell counts could switch to a combination of zidovudine and didanosine. The estimated median survival for all patients was 28 months (95% confidence interval, 23-46). However, for patients whose entry CD4 cell counts were 100-300/mm3, the estimated 4-year survival was 80%. Baseline CD4 and CD8 cell counts, hemoglobin, lymphocytes, sedimentation rates, diagnosis of AIDS, and fever were significant predictors of overall survival. Principal toxicities were pancreatitis and peripheral neuropathy; no new toxicities were seen with extended didanosine treatment that had not been observed in shorter-term studies. This 5-year follow-up shows that didanosine can be tolerated for > 4 years in some patients with advanced HIV infection and may have particular long-term utility in patients with moderately advanced immunosuppression.

Adult↗

PubMed1995

Comparative analysis of anti-human immunodeficiency virus type 1 activities of dideoxynucleoside analogs in resting and activated peripheral blood mononuclear cells.

We determined the anti-human immunodeficiency virus type 1 (anti-HIV-1) activities of various dideoxy-nucleoside analogs by using phytohemagglutinin-activated peripheral blood mononuclear cells (PHA-PBMs) and resting PBMs (R-PBMs) as target cells. The comparative order of anti-HIV-1 activity in PHA-PBMs was azidothymidine (AZT) > dideoxycytidine (ddC) > dideoxythymidinene (d4T) > dideoxyinosine (ddI) and 9-(2-phosphonylmethoxyethyl)adenine (PMEA) > 2'-beta-fluoro-dideoxyadenosine (F-ara-ddA), while that in R-PBMs was ddC > ddI, PMEA, and F-ara-ddA, >> AZT and d4T. A pronucleotide, bis-(S-acetylthioethanol)phosphotriester-ddAMP, which bypasses the anabolic monophosphorylation step for the intracellular delivery of ddAMP, was highly active both in PHA-PBMs and R-PBMs. These data may have basic and clinical relevance in the design of anti-HIV chemotherapy, particularly combination chemotherapy with dideoxynucleosides, and in the development of active pronucleotides.

Antiviral Agents↗

PubMed1995

Pharmacokinetics of dideoxypurine nucleoside analogs in plasma and cerebrospinal fluid of rhesus monkeys.

The pharmacokinetics of 2',3'-dideoxyadenosine (ddA), didanosine, 2',3'-dideoxyguanosine (ddG), and 6-halogenated prodrugs of ddG, 6-chloro-ddG and 6-iodo-ddG, in plasma and cerebrospinal fluid (CSF) were studied in a non-human primate model. ddA was rapidly and completely deaminated to didanosine, such that didanosine concentration profiles in plasma and CSF were identical following administration of ddA and didanosine. The mean clearance of didanosine was 0.50 liters/h/kg, the terminal half-life was 1.8 h, and the CSF-to-plasma ratio was 4.8%. The disposition of ddG was similar, with a clearance of 0.70 liters/h/kg and a half-life of 1.7 h. The adenosine deaminase-mediated conversion of the 6-halogenated-ddG prodrugs to ddG was rapid but incomplete (48% for 6-chloro-ddG and 29% for 6-iodo-ddG). The CSF-to-plasma ratios of ddG with equimolar doses of ddG, 6-chloro-ddG, and 6-iodo-ddG were 8.5, 24, and 17%, respectively, but the actual ddG exposures in CSF (area under the CSF concentration-time curve) were comparable for ddG (12.1 microM.h) and the 6-halogenated-ddG prodrugs (18.8 microM.h for 6-chloro-ddG, 9.3 microM.h for 6-iodo-ddG).6-Chloro-ddG was not detectable in plasma or CSF, and the CSF-to-plasma ratio of 6-iodo-ddG was 9.4%, so the higher CSF-to-plasma ratios of ddG with the administration of the 6-halogenated-ddG prodrugs does not appear to be the result of enhanced penetration of the prodrug and subsequent dehalogenation to ddG. The penetration of ddG into CSF exceeds that of didanosine and is enhanced by administration of the 6-halogenated prodrugs, although the mechanism of this enhanced penetration is unclear.

Animals↗

PubMed1994

Conformationally locked nucleoside analogues. Synthesis of dideoxycarbocyclic nucleoside analogues structurally related to neplanocin C.

The glycon moiety of nucleosides in solution is known to exist in a rapid dynamic equilibrium between extreme northern and southern conformations as defined by the pseudorotation cycle. The concept of preparing rigid nucleoside analogues with the glycon conformation locked in one of these two extremes was tested with the synthesis of some cyclopropane-fused dideoxycarbocyclic nucleosides, similar to the well-known class of anti-HIV active dideoxynucleosides. The new compounds described here are dideoxynucleoside analogues of the fermentation product neplanocin C (6) which exhibits a typical northern geometry for its 6-oxabicyclo[3.1.0]hexane pseudosugar moiety. However, in view of the lability of the epoxide ring in this system, the equivalent cyclopropane-fused bicyclo[3.1.0]hexane system was used instead to prepare the corresponding dideoxynucleoside analogues bearing all the common bases [(+/-)-9-13]. Due to the well-documented preference of unrestricted bicyclo[3.1.0]hexane systems to exist exclusively in a boat conformation, the resulting nucleosides are structurally locked in a typical northern conformation similar to that of neplanocin C. The locked northern conformation in these nucleosides remained unchanged in solution in the 20-80 degrees C temperature range according to variable temperature 1H NMR studies. For the synthesis of these compounds, racemic trans-1-[(benzyloxy)methyl]-4-hydroxybicyclo[3.1.0]hexane [(+/-)-18] was prepared by a samarium-promoted cyclopropanation reaction with the antecedent cyclopentenol. All of the bases were incorporated under Mitsunobu conditions and converted to the desired final products following a standard methodology. Anti-HIV evaluation revealed that only the adenosine analogue (+/-)-9 possessed enough activity to warrant resolution into its optical antipodes. This was realized by chiral HPLC chromatography to give the individual enantiomers (-)-32 and (+)-33. Adenosine deaminase was used to identify isomer (+)-33 as the enantiomer with the "natural" configuration which was solely responsible for the observed biological activity and toxicity of (+/-)-9. It is possible that the exclusive northern conformation adopted by these nucleosides reduces their substrate affinity for the various activating kinases, except in the case of the adenosine analogue.

Adenine↗

PubMed1994

Divergent anti-human immunodeficiency virus activity and anabolic phosphorylation of 2',3'-dideoxynucleoside analogs in resting and activated human cells.

The mechanism of divergent anti-human immunodeficiency virus type 1 (HIV-1) activity of various 2',3'-dideoxynucleoside analogs (ddNs) in peripheral blood mononuclear cells (PBM) was studied. We demonstrate that the in vitro anti-HIV-1 activity of various ddNs varies profoundly and that the divergent antiviral activity is related to the extent of anabolic phosphorylation of each ddN and its counterpart 2'-deoxynucleoside (dN). We also show that certain ddNs cause a reduction of their counterpart dNTP formation in PBM in the following order: 2',3'-dideoxycytidine (ddC) >> 2',3'-didehydro-2',3'-dideoxythymidine (d4T), 3'-thia-2',3'-dideoxycytidine (3TC), 2',3'-dideoxyinosine (ddI), 2',3'-dideoxyguanosine (ddG) > 3'-azido-2',3'-dideoxythymidine (AZT) > 2'-beta-fluoro-2',3'-dideoxyadenosine (F-ara-ddA). Based on the phosphorylation profiles, anti-HIV-1 ddNs can be classified into two groups: (i) cell-activation-dependent ddNs such as AZT and d4T that are preferentially phosphorylated, yield higher ratios of ddNTP/dNTP, and exert more potent anti-HIV-1 activity in activated cells than in resting cells; and (ii) cell-activation-independent ddNs including ddI (and 2',3'-dideoxyadenosine), F-ara-ddA, ddG, ddC, and 3TC that produce higher ratios of ddNTP/dNTP and exert more potent anti-HIV-1 activity in resting cells. These data should provide a basis for the elucidation of the mechanism of the divergent antiretroviral activity of ddNs.

Cells, Cultured↗

PubMed1994

Enzymatic assay for quantification of deoxynucleoside triphosphates in human cells exposed to antiretroviral 2',3'-dideoxynucleosides.

Quantification of intracellular 2'-deoxynucleoside-5'-triphosphates (dNTPs) is of importance in studies of antiretroviral 2',3'-dideoxynucleoside analogs (ddNs) and a highly sensitive enzymatic assay for dNTPs has frequently been used for this purpose. However, the susceptibility of the assay to interference from the corresponding substrate analogs, ddNTPs, is still undefined. Ideally, DNA polymerases used in the assay should meet at least two criteria: (i) high fidelity to the template even in the presence of ddNTPs and (ii) low affinity for ddNTPs. None of the currently used exonuclease-free Klenow and Sequenase enzymes met both criteria. However, Sequenase had higher fidelity to the template than did the Klenow enzyme in the presence of pyrimidine-ddNTPs, and its reaction followed first order kinetics. We have, therefore relying primarily on Sequenase, designed a dNTP proportional reduction assay to correct the ddN-induced deviation in the enzymatic assay. With the use of high-fidelity exonuclease-free DNA polymerase and the application of correction factors, we now can accurately quantify dNTPs with a minimum detection limit as low as 0.1 pmol, using as few as 1 x 10(4) peripheral blood mononuclear cells. The method described should be useful in the study and development of antiretroviral ddNs.

Antiviral Agents↗

PubMed1994

Identification of drug-related genotypic changes in HIV-1 from serum using the selective polymerase chain reaction.

We attempted to detect drug-related HIV-1 pol gene mutations by selective polymerase chain reaction (PCR) using both proviral DNA and viral RNA isolated from patients (pts) with AIDS or ARC receiving antiretroviral therapy. Peripheral blood mononuclear cell (PBM)-associated proviral DNA and serum-derived viral RNA were obtained from eight patients before and after receiving an alternating regimen of AZT and ddC for 15-41 months or ddI monotherapy for 12-26 months. These specimens were examined for the presence of mutations at positions 70, 74, 215 and 219. We noted that selective PCR results can be ambiguous depending on the quantity of DNA template employed. We, therefore, used the minimal quantity of DNA templates that yielded evaluable PCR products in this study. For all the eight pairs of pre- and post-therapy proviral DNA samples, selective PCR results agreed with independently determined nucleotide sequences. Results of reverse transcription of serum-derived viral RNA followed by selective PCR differed in some cases from those using the proviral DNA. In particular, the use of serum viral RNA appeared to allow earlier detection of changes in drug-related mutations than the use of PBM-associated proviral DNA. We conclude that (i) selective PCR using the minimum and sufficient number of PBM-associated proviral DNA and serum viral RNA copies successfully detects the presence of known pol gene mutations; (ii) drug-related mutations may be distinguished earlier in virions in serum (or plasma) than in proviral DNA in PBM; and (iii) quantification of HIV-1 prior to selective PCR may be an important component in monitoring the therapy of HIV-1 infection.

Antiviral Agents↗

PubMed1994

A C2 symmetry-based HIV protease inhibitor, A77003, irreversibly inhibits infectivity of HIV-1 in vitro.

A C2 symmetry-based HIV protease inhibitor, A77003, exerts potent antiviral activity against a wide spectrum of HIV isolates in vitro. In this study, we asked whether A77003 could cause irreversible conformational changes to HIV-1, whether the amounts of viral RNA and p24 capsid protein per virion were altered, and how the infectivity of the virus produced in the presence of the drug was affected. We found that the number of viral particles and per-virion viral RNA content of the virus produced in the presence of A77003 did not significantly differ from those of the virus produced in the absence of the drug, whereas significant morphological changes were observed as assessed by transmission electron microscopy. However, the virus produced in the presence of A77003 contained substantially less p24gag protein per virion particle as compared to those produced in the absence of the drug or in the presence of AZT. Virions produced in the presence of A77003 showed up to 50-fold less infectious capability in subsequent tissue culture than control virions produced in the absence of drug or in the presence of AZT. This reduction in infectivity was maintained for at least 10 days in culture. The present data suggest that A77003 impairs HIV-1 protease-mediated Gag processing, interferes with the assembly and maturation of the virus, and leads to an irreversible loss of the infectivity of the virus, although a low but positive level of reversion to infectivity during the 10-day assay occurs. These features of A77003 (and perhaps similar HIV protease inhibitors as well) anti-HIV activity should represent desirable properties for antiviral therapy of AIDS and related diseases.

Antiviral Agents↗

PubMed1994

Purified GPI-anchored CD4DAF as a receptor for HIV-mediated gene transfer.

CD4 is the major cellular receptor for the human immunodeficiency virus (HIV). A hybrid gene encoding the extracellular domains of CD4, linked to the sequence encoding the membrane attachment region of the glycosylphosphatidylinositol (GPI)-anchored protein decay accelerating factor (DAF) was stably transfected into HeLa cells. The resultant cell line (T4HD) expressed GPI-anchored CD4DAF at high levels and was susceptible to gene transfer with a recombinant HIV vector. In an effort to expand the spectrum of cells susceptible to HIV gene transfer, CD4DAF was released from the surface of the T4HD cell line by detergent lysis, purified by immunoaffinity chromatography, and reincorporated into native HeLa cells. Incorporation occurred via the GPI anchor as evidenced by cleavage with phosphatidylinositol-specific phospholipase C. More than 95% of the CD4DAF-treated HeLa cells were CD4-positive by flow cytometry, and kinetic analysis demonstrated that over 75% of the fusion protein remained anchored to the cell membrane after 90 min at 37 degrees C. The purified protein retained its ability to bind the envelope protein of HIV. When incorporated, it bound fluorescein isothiocyanate (FITC)-conjugated gp120, and in its soluble form blocked transduction of CD4-positive cells incubated with an HIV-derived vector containing the Neo gene. In contrast to the T4HD cells, exposure of CD4DAF-treated cells to the Neo HIV vector yielded only transient neomycin-resistant colonies. These results suggest that endogenous synthesis of the CD4 molecule may be necessary for successful HIV genomic integration.

Antigens, CD↗

PubMed1994

A randomized pilot study of alternating or simultaneous zidovudine and didanosine therapy in patients with symptomatic human immunodeficiency virus infection.

A randomized pilot study comparing alternating and simultaneous regimens of zidovudine and didanosine (ddl) was conducted in 41 patients with AIDS or symptomatic human immunodeficiency virus (HIV) infection. Patients on each regimen received the same overall amounts of zidovudine and didanosine over time. CD4 cell counts in patients on the simultaneous regimen reached a maximum (mean +/- SE) of 108 +/- 16/mm3 above baseline (two-tailed P < or = .0001) and were significantly higher than in patients on the alternating regimen at all time points during weeks 6-45. At 54 weeks, the CD4 cell counts in the patients on the simultaneous regimen were still 40 +/- 19/mm3 above baseline. Patients on the simultaneous regimen also had significantly greater weight gain. While toxicities were generally mild and comparable between the regimens, 1 patient on the simultaneous regimen died of pancreatitis and lactic acidosis. Thus, simultaneous therapy provided more sustained elevations in CD4 cells than alternating therapy over 1 year and may be worth exploring in larger controlled trials.

AIDS-Related Opportunistic Infections↗

PubMed1994

Quantitative analysis of viral burden in tissues from adults and children with symptomatic human immunodeficiency virus type 1 infection assessed by polymerase chain reaction.

The amount of human immunodeficiency virus type 1 (HIV-1) in various tissues was investigated by polymerase chain reaction (PCR) in 16 patients with end-stage HIV-1 infection and 7 patients with symptomatic but less advanced disease. During postmortem study of the 16 end-stage patients, HIV-1 DNA was found most often in lymph nodes and the spleen (both 100%), lung (93.8%), and colon (87.5%). Biopsied lymph nodes from the 7 symptomatic patients contained substantially higher copy numbers of HIV-1 RNA and DNA than did peripheral blood mononuclear cells (PBMC). Plasma viral RNA levels correlated significantly with the amount of HIV-1 RNA in PBMC (r2 = .86, P = .0025) but not with the level of viral RNA in lymph nodes in patients with symptomatic HIV-1 infection. These data suggest that although lymph nodes represent the main site for HIV-1 infection and replication, the level of circulating viral burden may not be solely determined by the magnitude of active HIV-1 replication in lymph nodes.

Acquired Immunodeficiency Syndrome↗

PubMed1994

Protein binding of human immunodeficiency virus protease inhibitor KNI-272 and alteration of its in vitro antiretroviral activity in the presence of high concentrations of proteins.

KNI-272 represents a peptide-based protease inhibitor having potent antiretroviral activity against human immunodeficiency virus (HIV) in vitro. The structure contains allophenylnorstatine [(2S,3S)-3-amino-2-hydroxy-4-phenylbutyric acid] with a hydroxymethylcarbonyl isostere. We asked whether this experimental anti-HIV agent could exert its activity in vitro in the presence of relatively high concentrations of fetal calf serum (FCS) and assessed its protein-binding properties by using fresh human plasma preparations. The 50 and 75% inhibitory concentrations of KNI-272 against HIV type 1 replication in vitro were 3- to 5-fold and 5-fold higher in the presence of 50% FCS and 15- to 25-fold and 25- to 100-fold higher in the presence of 80% ECS, respectively, than those with 15% FCS, whereas the antiviral activity of 2',3'-dideoxyinosine was not significantly affected by FCS concentrations in the culture. Detailed studies of the protein binding of KNI-272 suggest that in human plasma binding occurs predominantly to alpha 1-acid glycoprotein and that KNI-272 is probably extensively (approximately 98 to 99%) protein bound at concentrations likely to be achieved in the circulation. Thus, higher levels of KNI-272 in plasma may be required when this compound undergoes clinical trials relative to those inferred from in vitro data involving the use of 10 to 15% FCS-containing culture media. The current data may have a relevance to other antiretroviral drugs that are under development and that have a high protein-binding capacity.

Animals↗

PubMed1994

Anti-human immunodeficiency virus type 1 activity of hydroxyurea in combination with 2',3'-dideoxynucleosides.

The effects of hydroxyurea (HU), an inhibitor of ribonucleotide reductase, on the replication of human immunodeficiency virus type 1 (HIV-1) in activated peripheral blood mononuclear cells were studied. The inhibition of HIV-1 replication by HU alone was dose dependent, with a 90% inhibitory concentration of 0.4 mM, a plasma concentration tolerated by patients with oncological diseases. HU at lower concentrations (< 0.1 mM) was found to potentiate the antiviral activity of 2',3'-dideoxyinosine (ddl), 3'-azido-2',3'- dideoxythymidine, and 2',3'-dideoxycytidine against HIV-1, with the potentiation being ddl greater than 3'-azido-2',3'- dideoxythymidine = 2',3'-dideoxycytidine. In the presence of 0.1 mM HU, the 90% inhibitory concentration of ddl was reduced by 6-fold in activated peripheral blood mononuclear cells. The potentiating effect of HU on ddl action was time dependent, with the greatest inhibition of HIV-1 growth being seen when HU was present during and after virus adsorption, i.e., apparently coinciding with the time of proviral DNA synthesis. A brief incubation of activated cells with HU and ddl at low concentrations before virus exposure reduced p24 production by > 50%. Analyses using high performance liquid chromatography and enzymatic assays suggested that the greater degree of potentiation by HU of the action of ddl, compared with the other dideoxynucleosides, is due to the more effective inhibition by HU of dATP synthesis, compared with the synthesis of the other deoxynucleoside triphosphates (dGTP, dTTP, and dCTP). The present study suggests that, for appropriate agents, pharmacological reduction of deoxynucleoside triphosphate levels represents a potential therapeutic approach for inhibition of HIV-1 replication.

Antiviral Agents↗

PubMed1994

Enhancement by 2'-deoxycoformycin of the 5'-phosphorylation and anti-human immunodeficiency virus activity of 2',3'-dideoxyadenosine and 2'-beta-fluoro-2',3'-dideoxyadenosine.

The anti-human immunodeficiency virus agents 2',3'-dideoxyadenosine (ddAdo) and 2'-beta-fluoro-2',3'-dideoxyadenosine (2'-beta-F-ddAdo) are rapidly converted, both in vitro and in vivo, to the corresponding inosine analogs by the widely distributed enzyme adenosine deaminase (EC 3.5.4.4). We have determined the effects of the potent adenosine deaminase inhibitor 2'-deoxycoformycin (2'-dCF) on ddAdo and 2'-beta-F-ddAdo metabolism in MOLT-4 cells and on ddAdo antiviral activity in the ATH8 test system. At levels as low as 5 nM in the incubation medium, 2'-dCF effectively blocks the extracellular deamination of both agents, thus permitting their rapid cellular uptake as the unchanged parent compounds, rather than as the less lipid-soluble 2',3'-dideoxyinosine or 2'-beta-fluoro-2',3'-dideoxyinosine. The result is a significant increase in intracellular levels of the pharmacologically active forms 2',3'-dideoxyadenosine-5'-triphosphate and 2'-beta-fluoro-2',3'-dideoxyadenosine-5'-triphosphate. The effect becomes maximal over the range of 50-250 nM 2'-dCF and declines to control levels when extracellular 2'-dCF levels exceed 1 microM. This decrease in ddAdo and 2'-beta-F-ddAdo phosphorylation with higher levels of the inhibitor appears to result from intracellular penetration of 2'-dCF and consequent inhibition of intracellular deamination, a critical step in the activation of both agents through the 5'-nucleotidase pathway. In anti-human immunodeficiency virus assays, a 2.2-fold increase in ddAdo antiviral potency was seen at 2'-dCF levels of 20 and 50 nM.

Adenosine Deaminase Inhibitors↗

PubMed1993

Changes in drug sensitivity of human immunodeficiency virus type 1 during therapy with azidothymidine, dideoxycytidine, and dideoxyinosine: an in vitro comparative study.

Human immunodeficiency virus type 1 (HIV-1) strains were isolated from nine patients before and after prolonged therapy with either an alternating regimen of 3'-azido-3'-deoxythymidine (AZT) and 2',3'-dideoxycytidine (ddC) (AZT/ddC) or 2',3'-dideoxyinosine (ddI) alone. All strains obtained from four patients who received AZT/ddC for up to 41 mo were highly insensitive to AZT in vitro. Only one strain obtained after AZT/ddC therapy showed reduced susceptibility to ddC in addition to AZT and had previously unreported amino acid substitutions in the viral polymerase-encoding pol region, whereas three other strains had one or more of the five previously reported AZT-related mutations. In five HIV-1 strains from patients who received ddI for up to 29 mo, no appreciable decrease in sensitivity to ddI was detected. Two strains isolated after ddI therapy had no significant amino acid mutations, although three strains had a mutation reportedly associated with ddI administration. These data suggest that HIV-1 develops reduced susceptibility to AZT more readily than to ddC and ddI and/or that the reduced susceptibility to ddC and ddI is modest in degree. Moreover, the present data suggest that an alternating regimen of AZT and ddC does not block the emergence of AZT-insensitive variants. It should be noted, however, that the current results do not provide a basis for concluding that AZT/ddC or ddI is inferior, equivalent, or superior to AZT as therapy of AIDS.

Acquired Immunodeficiency Syndrome↗

PubMed1993

Challenges in the therapy of HIV infection.

Drugs that inhibit human immunodeficiency virus (HIV) replication have been shown to have clinical utility in patients with HIV infection. However, the immunological improvement induced by available anti-HIV therapies in patients with acquired immune deficiency syndrome (AIDS) is incomplete and transient. Explanations for this may include immunological barriers to complete reconstitution, low therapeutic indices of the available drugs, and the development of viral resistance. An understanding of these processes, as discussed here by Robert Yarchoan and colleagues, may provide important leads for the development of improved therapy for AIDS.

Acquired Immunodeficiency Syndrome↗