Therapy for human immunodeficiency virus infection

Polio, AIDS, and Ebola: A Recurrent Ethical Dilemma

During the 2014 West African outbreak, a dilemma emerged about the ethics of conducting randomized placebo-controlled trials in the midst of a rapidly spreading, devastating epidemic for which there was no effective treatment. The dilemma has in fact has deep historic roots; it has appeared in several previous fearsome epidemics-during the poliomyelitis epidemic in the 1930s-1950s, and again during the AIDS epidemic in the1980s-1990s. Moreover, ethical and social questions characterizing each of these epidemics-the increased risks of withholding potentially life-saving drugs for people assigned to a control arm and the damaging effect on eroding community trust-were conceptualized beforehand in the 1925 novel Arrowsmith. A historical analysis both reaffirms that rigorous placebo-controlled trials remain indispensable tools in epidemic settings and also provides guidance on how to approach the ethical and social issues that will likely arise when these trials are carried out in future epidemic emergencies.

Inhibition of Human Immunodeficiency Virus Type 1 Reverse Transcriptase by Degradation Products of Ceftazidime

Previous work by Hafkemeyer et al. (1991) [ Nucleic Acids Research19: 4059–4065] indicated that a degradation product of ceftazidime, termed HP 0.35, was active against the RNase H activity of human immunodeficiency virus type 1 (HIV-1) and feline immunodeficiency virus (FIV) reverse transcriptase (RT) in vitro. Attempting to repeat these results, we isolated HP 0.35 from an aqueous degradation of ceftazidime and, after careful purification, we found HP 0.35 to be essentially inactive against both the polymerase and RNase H domains of HIV-1 RT (IC50 of >100 μg mL−1). During the investigation we discovered that polymeric degradation products of ceftazidime inhibited both the polymerase and, to a greater extent, the RNase H activities of HIV-1 RT in vitro (IC50 approximately 0.1 and 0.01 μg mL−1, respectively). Subjecting HP 0.35 to conditions under which it could polymerize induced inhibitory activity similar to that of the polymeric ceftazidime degradation products. It is proposed that the previously reported activity of HP 0.35 may have resulted from the presence of low levels of polymeric material either from incomplete purification or from polymerization of HP 0.35 during storage or in vitro testing.

Efficacy and Toxicity of Long-Term Administration of 2′,3′-dideoxycytidine in the LP-BM5 Murine-Induced Immunodeficiency Model

The LP-BM5 murine retrovirus-induced immunodeficiency model was used to evaluate the efficacy and toxicity of long-term 2′,3′-dideoxycytidine (DDC) therapy. A mean plasma drug concentration of 0.2 + 0.02 μm of DDC for 3 months was found to reduce splenomegaly, lymphoadenopathy and hypergammaglobulinemia in infected mice. However, DDC also reduced spleen weight in control mice and spleen haemopoiesis in both infected and uninfected animals. In the bone marrow the most prominent feature of DDC treatment was a marked reduction of megakariocytes, while in the liver an hepatocellular vacuolation was evident in uninfected animals. DDC reduced, but did not prevent, LP-BM5 integration in lymph node DNA and Pr 60gag expression in spleen lymphocytes and bone marrow cells. Furthermore, DDC reduced the mitochondrial DNA content and restored the mitogen proliferation of T cells but not that of B cells in infected mice. Thus, DDC appears to be of some, but limited, efficacy in murine AIDS, with a toxicity profile involving more cell types than previously thought.

Intracellular Metabolism of 3′-azido-3′-deoxythymidine and 2′,3′-dideoxyinosine in Combination in the Absence and Presence of Ribavirin

We examined the intracellular phosphorylation of 3′-azido-3′-deoxythymidine (AZT) and 2′,3′-dideoxyinosine (ddl) and the effects on rNTP and dNTP pools when AZT and ddl were incubated separately and in combination in lymphocytes. We also compared the effect of adding ribavirin (RBV) to the two-drug combination of AZT + ddl. AZT and ddl, used singly or in combination, had no effect on the dNTP pools of CEM lymphoblastoid cells. Neither did the combination of AZT + ddl have any effect on the rNTP pools. RBV, a known inhibitor of IMP dehydrogenase, caused a decrease in GTP and an increase in dTTP whether incubated alone or with the drug combination of AZT + ddl. The addition of AZT + ddl therefore did not alter the effects of RBV upon cellular nucleotide pools. AZT was phosphorylated to a much greater extent than ddl. The activation of ddl to ddA-TP was increased 2-fold in the presence of AZT, whereas AZT phosphorylation was unchanged when combined with ddl. This increase in ddl activation may explain in part the synergistic antiviral activity of the combination of AZT + ddl. The increased activation was not due to increased phosphorylation of ddl resulting from IMP dehydrogenase inhibition. The addition of 10 μm RBV to the two-drug combination of AZT + ddl did not change the intracellular phosphorylation of AZT or ddl. The activation of ddl to ddA-TP, when combined with AZT, appeared to be maximal and could not be further increased by addition of RBV to this combination.

The Inhibitory Effect of ddC on Human Immunodeficiency Virus Replication Diminishes in Cells that are Chronically Exposed to the Drug

One possible explanation for the failure of human immunodeficiency virus type 1 (HIV-1) antiretroviral inhibitors to block the clinical progression of the infection may be a failure to maintain adequate drug levels at the site of viral replication. We have previously found that exposure of human monoblastoid cells (U937) for several months to a therapeutically relevant concentration (0.1 μM) of 2′,3′-dideoxycytidine (zalcitabine, ddC) allowed the isolation of a drug-resistant cell line characterized by a normal drug transport but a reduced ability to accumulate 2′,3′-dideoxycytidine 5′-triphosphate (the active antiretroviral form of the drug). In this paper we show that the drug-resistant cells were indistinguishable from normal cells in terms of surface CD4 receptors. The susceptibility of parental and ddC-resistant U937 cells to infection by HIV-1 was similar, as measured by proviral DNA formation. However, HIV-1 p24 production and the number of infectious virus particles produced were significantly lower in the drug-resistant compared to control cells. Addition of 0.1 μM ddC inhibited viral production by up to 92% in the control cells but had no effect on ddC-resistant cells. Thus, human cells exposed to therapeutically relevant ddC concentrations for several months show a reduced ddC anabolism and allow ddC-sensitive HIV-1 to replicate in the presence of inhibitory ddC concentrations.

Inhibition of HIV-1 and LP-BM5 Replication in Macrophages by Dideoxycytidine and Dideoxycytidine 5′-Triphosphate

The antiviral agent 2′,3′-dideoxycytidine (ddC) has been shown to be active against HIV-1 infectivity. However, conflicting results have been reported concerning its efficacy in macrophages. Because macrophages possess low levels of the kinase(s) responsible for ddC phosphorylation, we investigated the ability of ddC and 2′,3′-dideoxycytidine 5′-trisphosphate (ddCTP) to suppress HIV-1 and LP-BM5 replication in these cells. Retrovirus replication was only partially inhibited in the two systems investigated by a high (1 μM) ddC concentration. The direct administration of ddCTP, using autologous red blood cells as a delivery system, was found to inhibit HIV-1 and LP-BM5 replication by more than 90% in macrophages without affecting major cell functions. These data, together with those already reported for FIV [Magnani et al. (1994) AIDS Res Hum Retroviruses 10: 1179-1186], suggest that the anabolic phosphorylation of ddC is an important determinant of its anti-HIV activity and that pharmacological interventions that modulate ddC metabolism may be useful for improving its antiretroviral activity in macrophages.

On the Molecular Modeling Analyses of Novel HIV-1 Protease Inhibitors Based on Modified Chitosan Dimer

The molecular modeling studies include quantitative structure activity relationship, IR spectra, and docking calculations, occurring for novel inhibitors based on chitosan dimer which were tried as HIV protease. The inhibitors were investigated with molecular modeling calculations at different level of theories. Each compound has phenol with hydroxymethylcarbonyl (HMC) group which added to chitosan in positions 2, 3, 2′, or 3′. The geometry of studied compounds is optimized with semiempirical PM3 method. Quantitative structure activity relationship (QSAR) properties of the suggested compounds are calculated at the same level of theory. Depending on QSAR calculations, the compounds with positions 2 and 2′ are less hydrophilic. The position 2′ compound makes good docking interaction into HIV protease active site. Calculated IR spectra indicate that the interaction through hydrogen bonding through the hydrogen of OH at positions 3 and 3′ gives rise to two OH bands one for chitosan and the other for phenol and HMC group. While at position 3′ CH band starts to appear.

Electrochemical detection of azidothymidine on modified probes based on chitosan stabilised silver nanoparticles hybrid material

Silver nanoparticle stabilized by chitosan is synthesized for modification of sensing probe for AZT estimation in human plasma.

Mutations in the NS5B region of the hepatitis C virus genome correlate with clinical outcomes of interferon-alpha plus ribavirin combination therapy

BACKGROUND AND AIM

Combination treatments of interferon-alpha (IFN) and ribavirin (RBV) are more effective than those of IFN alone in hepatitis C virus (HCV) infection. However, mechanisms of the action of the combination regimen are not well understood. To elucidate the viral genetic basis of IFN plus RBV combination therapy, genetic variabilities of HCV-1b were analyzed.

METHODS

We performed pair-wise comparisons of full-length HCV genomic sequences in three patients' sera before and after initiation of IFN plus RBV treatment. Subsequently, we analyzed amino acid sequences of the NS5B region, which codes for the viral RNA-dependent RNA polymerase, and compared these with the outcomes of the therapy in 81 patients.

RESULTS

Analysis of the entire HCV sequence in patients who received IFN plus RBV therapy did not show consistent amino acid changes between before and after the initiation of the therapy. NS5B sequence analyses revealed that mutations at positions 300-358 of NS5B, including polymerase motif B to E, occurred more frequently in a group of patients exhibiting a sustained viral response (SVR) or an end-of-treatment response (ETR) compared with a group of patients exhibiting a non-response (NR). Closer examination revealed that mutations at aa 309, 333, 338 and 355 of NS5B occurred significantly more frequently in the SVR plus ETR group than in the NR group (P = 0.0004). Multivariate analysis showed that the number of mutations at these four sites was an independent predictor of SVR plus ETR versus NR.

CONCLUSIONS

Particular amino acid changes in the NS5B region of HCV may correlate with outcomes of IFN plus RBV combination therapy.

Improved obstetric outcomes and few maternal toxicities are associated with antiretroviral therapy, including highly active antiretroviral therapy during pregnancy

Data from 2543 HIV-infected women were analyzed to correlate antiretroviral therapy (ART) used during pregnancy with maternal and pregnancy outcomes. ART was analyzed according to class of agents used and according to monotherapy versus combination ART containing neither protease inhibitors (PIs) nor nonnucleoside reverse transcriptase inhibitors versus highly active ART. Timing of ART was classified according to early (recorded at or before 25-week gestation study visit) and late (recorded at 32-week gestation or delivery visit) use. Maternal outcomes assessed included hematologic, gastrointestinal, neurologic, renal, and dermatologic complications; gestational diabetes; lactic acidosis; and death. Adverse pregnancy outcomes assessed included hypertensive complications; pre-term labor or rupture of membranes; preterm delivery (PTD); low birth weight; and stillbirth. Logistic regression analyses controlling for multiple covariates revealed ART to be independently associated with few maternal complications: ART use was associated with anemia (odds ratio [OR] = 1.6, 95% confidence interval [CI]: 1.1-2.4), and late use of ART was associated with gestational diabetes (OR = 3.5, 95% CI: 1.2-10.1). Logistic regression analyses revealed an increase in PTD at <37 weeks for 10 women with late use of ART not containing zidovudine (ZDV; OR = 7.9, 95% CI: 1.4-44.6) and a decrease in adverse pregnancy outcomes as follows: late use of ART containing ZDV was associated with decreased risk for stillbirth and PTD at <37 weeks (OR = 0.06, 95% CI: 0.02-0.18; OR = 0.5, 95% CI: 0.3-0.8, respectively), and ART containing nucleoside reverse transcriptase inhibitors but not ZDV during early and late pregnancy was associated with decreased risk for PTD at <32 weeks (OR = 0.3, 95% CI: 0.2-0.7). Benefits of ART continue to outweigh observed risks.

Square wave and elimination voltammetric analysis of azidothymidine in the presence of oligonucleotides and chromosomal DNA

Azidothymidine (AZT, 3'-azido-3'-deoxythymidine, Zidovudine, Retrovir) is an approved and widely used antiretroviral drug for the treatment of human immunodeficiency virus (HIV) infection. Dynamic electrochemical methods have been employed for the fast and inexpensive determination of this drug in natural samples. The electrochemical signal of AZT, resulting from the reduction of azido group, was studied by square wave voltammetry (SWV), linear sweep voltammetry (LSV) and elimination voltammetry with linear scan (EVLS) using a hanging mercury drop electrode (HMDE). This paper explores the possibility of determining AZT in the presence of native (dsDNA) or denatured calf thymus DNA (ssDNA), and/or some synthetic oligodeoxynucleotides (ODNs). The detection limit of AZT in the absence and in the presence of ssDNA (10 microg/ml) is 1 and 250 nM, respectively. It was found that the signal of AZT is not substantially affected by the presence of DNA. We can therefore assume that the electrons are transferred through the adsorption layer of nucleic acids. By using the elimination procedure, both irreversible reduction signals of AZT and DNA are augmented. Moreover, the elimination signal in the peak-counterpeak form may indicate the adsorption of the analytes on the electrode surface preceding an electron transfer.

Theoretical mechanistic basis of the toxic effects and efficacy of AZT in HIV: AIDS

Toxic effects and efficacy of azidothymidine (AZT) in human immunodeficiency virus were evaluated by theoretical mechanistic biochemistry (TMB) techniques based on the structure of AZT and on the structure of HIV. AZT was positive (1+) for epoxide; (2+) for hydroxl free radical (*OH); (1+) for (*N(3)) azide free radical and (1+) for azide (N(3-)) generations, respectively. AZT was negative (-) for areneimine, and nitroso generations, respectively, for toxic effects totalling 5+ compared with dideoxycytidine (ddc) of 3+ and artesunate (At) of 0. Therefore for toxic effects the trend is AZT(5+) > ddc(3+) > At(0). TMB efficacy of AZT was based on the generations of *OH from the 1-NH (1+) and the 3(1)-azido (N(3))(1+) and azide free radical (*N(3)), (1+) totalling 3+ compared with ddc of 1+ and At of 1+. Therefore for efficacy, the trend is AZT(3+) > ddc(1+) = At(1+). In combination drug therapy, TMB postulates the following for HIV : AIDS: At(1+) + AZT(3+) + ddc(1+) > AZT(3+) + ddc(1+) = AZT(3+) + At(1+) > AZT(3+) > At(1+) + ddc(1+) > ddc(1+) = At(1+).

Autopsy findings in a human immunodeficiency virus-infected population over 2 decades: influences of gender, ethnicity, risk factors, and time

OBJECTIVES

To examine autopsy pathology in an urban population infected with the human immunodeficiency virus (HIV) and to determine if age at death and disease frequencies are associated with gender, HIV risk factors, ethnicity, and therapeutic era.

DESIGN AND METHODS

Retrospective analysis of autopsy data from 394 HIV-infected adults. The population was divided into 3 therapeutic eras for analysis: group A, 1979-1986; group B, 1987-1995; and group C, 1996-2000.

RESULTS

Women died at significantly younger ages than men (mean +/- SEM age, 38.9 +/- 1.0 years vs 42.5 +/- 0.64 years), even after adjustment for risk factors, ethnicity, and therapeutic era. This age discrepancy occurred despite a lower prevalence of arteriosclerosis, cachexia, and hepatitis B in women and no significant differences in the frequencies of other infectious diseases. Whites had a longer survival than patients of other ethnicities (mean age at death, 44.7 +/- 1.2 years for whites, 39.9 +/- 0.80 years for blacks, and 41.3 +/- 0.87 years for Hispanic individuals). Renal, cardiac, and splenic pathologies, Mycobacterium avium-intracellulare (MAI) infection, and cachexia were more common in blacks than in whites and/or Hispanic individuals, and cytomegalovirus and systemic lymphoma were more common in whites and Hispanic individuals than in blacks. Diseases associated with intravenous drug use were hepatitis C, cirrhosis, and tuberculosis; those with all sexual risk factors, cytomegalovirus infection, herpes simplex virus infection, and Pneumocystis carinii pneumonia; and those with homosexual risk, Kaposi sarcoma and MAI infection. The prevalence of many disease entities changed over time: compared with the other groups, group C had lower prevalences of many viral and fungal illnesses, MAI infection, systemic lymphoma, cachexia, and Kaposi sarcoma and higher prevalences of hepatitis, cirrhosis, arteriosclerosis, staphylococcal and streptococcal infections, and traumatic lesions. When the data were adjusted for changing demographic and risk composition, the only significant changes in disease frequency for period C were decreased prevalences of PCP and Kaposi sarcoma and increased prevalences of cirrhosis and arteriosclerosis.

CONCLUSIONS

Significant gender- and ethnicity-related differences in age of death occurred in this HIV-infected population, and these differences were not explained by the frequencies of diseases. The lower prevalences of PCP and Kaposi sarcoma in group C are likely a reflection of the impact of potent therapies on causes of mortality. The higher prevalences of cirrhosis and arteriosclerosis suggest that entities not targeted by antiretroviral reconstitution of immunity will play an increasingly important role in HIV-related mortality in the future.

Pan-Thames survey of occupational exposure to HIV and the use of post-exposure prophylaxis in 71 NHS trusts

OBJECTIVES

To review the management of occupational exposure to definite or suspected HIV-infected blood, following the introduction of the 1997 UK Department of Health guidelines on the use of post-exposure prophylaxis.

METHODS

Cross-sectional telephone survey of protocols in 71 NHS Trusts in the Pan-Thames region. Retrospective postal survey of the management of each definite or suspected HIV blood exposure between 1 July 1997 and 30 June 1999.

RESULTS

Sixty-two (93%) Trusts had a written protocol, with many specialties involved in exposure management. Twenty-four Trusts reported 171 occupational exposures to definite or suspected HIV-infected blood. Of 97 definite HIV exposures, eight (8%) were discovered on post-incident HIV testing of the source patient; to which most source patients agreed when approached. Seventy-two (74%) exposed health care workers started prophylaxis and 49 (68%) completed the recommended 4-week course. Only half of those whose exposures occurred more than 6 months ago were known to have had a follow-up HIV test.

CONCLUSIONS

Although most Trusts have implemented the Department of Health's guidance, collecting data on individual exposures proved difficult. We suggest that a designated department in each Trust co-ordinates and records HIV exposure management. Routine HIV testing is acceptable to most source patients and is appropriate in areas with a high prevalence of HIV seropositivity.

Evaluation of the efficacy of 2',3'-dideoxycytidine against adenovirus infection in a mouse pneumonia model

The antiviral activity of 2',3'-dideoxycytidine (ddC) has been investigated in a mouse pneumonia model. Consolidation of lung, histopathological changes, DNA synthesis as well as levels of TNFalpha were assayed. In this in vivo model, the oral administration of ddC twice daily over 4 days, displayed an inhibitory effect. The drug significantly reduced histopathologic responses. Analysis indicated that under treatment pulmonary lesions were less severe than those of untreated controls. These data confirm the in vitro activity of ddC against adenovirus. Thus, ddC represents a potential therapeutic approach for inhibiting adenovirus infection and may offer promise as an anti-adenovirus agent for immunocompromised patients in whom serious adenovirus infection may prove fatal.

Combination therapy as a tool to prevent emergence of bacterial resistance

Emergence of resistance is an ever increasing problem. One of the methods by which emergence of resistance may possibly be prevented, or at least delayed, is the use of combination therapy. Since the emergence of resistant mutants is a direct result of selective pressure by antimicrobial therapy, the chance of mutants resistant to two antimicrobials in the parent population being present is a product of mutation frequencies, provided that resistance mechanisms are independent. Comparative studies in in vitro pharmacokinetic models and in vivo indicate that emergence of resistance is less common when combination therapy is used. This is particularly true for microorganisms known to develop resistance relatively quickly, such as Pseudomonas aeruginosa, and resistance mechanisms which occur at a relatively high frequency.

Role of telomerase in normal and cancer cells

Shortening of the telomeric DNA at chromosome ends is postulated to limit the lifespan of human cells. In contrast, activation of telomerase, the enzyme that synthesizes telomeric DNA, is proposed to be an essential step in cancer cell immortalization and cancer progression. This review discusses the structure and function of telomeres and telomerase, the role of telomerase in cell immortalization, and the effects of telomerase inactivation on normal and cancer cells. Moreover, data on the experimental use of telomerase assays for cancer detection and diagnosis are reviewed. Finally, the review considers the evidence regarding whether telomerase inhibitors could be used to treat human cancers.

Inhibition of human immunodeficiency virus type 1 by packageable, multigenic antisense RNA

Viral-based vectors can provide an efficient delivery mechanism for stable expression of antisense RNA. To enhance and propagate the antiviral effect of antisense RNA, two novel human immunodeficiency virus type 1 (HIV-1)-based vector DNAs, designated as pMAG7 and pMAG19, were constructed which contained HIV-1 cis-acting packaging elements and produced multigenic HIV-1 antisense RNA that could target the entire pol, env, vif, vpu, vpr, rev, and tat and portions of gag and nef. The two DNAs were identical except that pMAG19 had additional gag coding sequences. Cotransfection of pMAG DNA and infectious, cloned HIV-1 DNA in 293 cells inhibited virus production (81%-98% reduction in reverse transcriptase activity) of various T cell-tropic and macrophage-tropic clade B isolates, such as NL4-3, YU-2, and JR-CSF. In addition, virion-associated pMAG antisense RNA was detected in residual virus particles produced by pNL4-3 in the presence of pMAG7 DNA, and the antisense sequences were stably transferred by infection of 174 x CEM cells. The results suggest that pMAG DNA may confer broad protection against HIV-1 by reducing initial virus burden due to antisense RNA and subsequent virus spread by propagation of antisense sequences along with wild-type virus.

Intracellular phosphorylation of zidovudine in an in vitro hollow fiber model

Combination antiretroviral therapy that includes zidovudine has proved much better in treating human immunodeficiency virus infection than monotherapy Diminished responses to zidovudine, especially when it was given alone, was likely due to factors including interpatient variability in pharmacokinetics, nonadherence, emergence of resistant mutants, and reduced cellular enzymatic processes to phosphorylate the drug. This study evaluated the intracellular metabolism of zidovudine up to 6 weeks using a hollow fiber cellular model system that simulated exposure of cells to steady-state concentrations achieved in humans. The CEM-T4 lymphocytes were exposed to simulated 200-, 600-, and 1200-mg daily doses of zidovudine. Samples were analyzed for monophosphate, diphosphate, and triphosphate metabolites of zidovudine by high-performance liquid chromatography separation and radiochemical detection. The monophosphate metabolite increased as simulated doses increased, but no corresponding increases in the active triphosphate metabolite occurred. In addition, intracellular metabolism of zidovudine did not change after exposure for 6 weeks. These results suggest that the active triphosphate metabolite of zidovudine does not change much when doses are increased or when exposed for at least 6 weeks. Hollow fiber models may be used effectively to investigate intracellular metabolism of antiviral agents and for some duration of time.

Metabolic characterization of a tripeptide human immunodeficiency virus type 1 protease inhibitor, KNI-272, in rat liver microsomes

KNI-272 is a tripeptide protease inhibitor for treating human immunodeficiency virus type 1 (HIV-1). In in vitro stability studies using rat tissue homogenates, KNI-272 concentrations in the liver, kidney, and brain decreased significantly with time. Moreover, in tissue distribution studies, KNI-272 distributed highly to the liver, kidney, and small intestine in vivo. From these results and reported physiological parameters such as the tissue volume and tissue blood flow rate, we considered the liver to be the main organ which takes part in the metabolic elimination of KNI-272. Then the hepatic metabolism of KNI-272 was more thoroughly investigated by using rat liver microsomes. KNI-272 was metabolized in the rat liver microsomes, and five metabolites were found. The initial metabolic rate constant (kmetabolism) tended to decrease when the KNI-272 concentration in microsomal suspensions increased. The calculated Michaelis-Menten constant (K(m)) and the maximum velocity of KNI-272 metabolism (Vmax), after correction for the unbound drug concentration, were 1.12 +/- 0.09 micrograms/ml (1.68 +/- 0.13 microM) and 0.372 +/- 0.008 microgram/mg of protein/min (0.558 +/- 0.012 nmol/mg of protein per min), respectively. The metabolic clearance (CLint,metabo), calculated as Vmax/K(m), was 0.332 ml/mg of protein per min. Moreover, by using selective cytochrome P-450 inhibitors and recombinant human CYP3A4 fractions, KNI-272 was determined to be metabolized mainly by the CYP3A isoform. In addition, ketoconazole, a representative CYP3A inhibitor, inhibited KNI-272 metabolism competitively, and the inhibition constant (Ki) was 4.32 microM.

Liposome-mediated delivery of antiviral agents to human immunodeficiency virus-infected cells

Intracellular delivery of novel macromolecular drugs against human immunodeficiency virus type-1 (HIV-1), including antisense oligodeoxynucleotides, ribozymes and therapeutic genes, may be achieved by encapsulation in or association with certain types of liposomes. Liposomes may also protect these drugs against nucleases. Low-molecular-weight, charged antiviral drugs may also be delivered more efficiently via liposomes. Liposomes were targeted to HIV-1-infected cells via covalently coupled soluble CD4. An HIV-1 protease inhibitor encapsulated in conventional negatively charged multilamellar liposomes was about 10-fold more effective and had a lower EC90 than the free drug in inhibiting HIV-1 production in human monocyte-derived macrophages. The drug encapsulated in sterically stabilized liposomes was as effective as the free drug. The EC50 of the reverse transcriptase inhibitor 9-(2-phosphonylmethoxyethyl)adenine (PMEA) was reduced by an order of magnitude when delivered to HIV-1-infected macrophages in pH-sensitive liposomes. A 15-mer antisense oligodeoxynucleotide against the Rev response element was ineffective in free form against HIV-1 replication in macrophages, while delivery of the oligonucleotide in pH-sensitive liposomes inhibited virus replication. The oligodeoxynucleotide encapsulated in sterically stabilized pH-sensitive liposomes with prolonged circulation in vivo, which were recently developed in the laboratories of the authors, was also highly effective. A ribozyme complementary to HIV-1 5'-LTR delivered in pH-sensitive liposomes inhibited virus production by 90%, while the free ribozyme caused only a slight inhibition. Cationic liposome-mediated co-transfection of the HIV-regulated diphtheria toxin A fragment gene and a proviral HIV clone into HeLa cells completely inhibited virus production, while the frame-shifted mutant gene was ineffective. Co-transfection of the proviral genome and a gene encoding a Rev-binding aptamer into HeLa cells via transferrin-associated cationic liposomes inhibited virus production. These studies indicate that liposomes can be used to facilitate the intracellular delivery of certain anti-HIV agents and to enhance their therapeutic effects. These properties may be particularly advantageous in the development of novel macromolecular drugs, which may be necessary because of the emergence of virus strains resistant to the currently available drugs.

Human immunodeficiency virus protease inhibitors

Human immunodeficiency virus (HIV) protease inhibitors have revolutionized the treatment of individuals infected with this pathogen. The protease is an enzyme that is essential for viral replication because it cleaves both structural and functional proteins from precursor viral polyprotein strands. Inhibition of this process suppresses viral replication, which produces immature noninfectious virions. When combined with reverse transcriptase inhibitors, these agents are very potent in suppressing viral replication. Pharmacologic properties, toxic profile, drug interactions, and resistance patterns differ among protease inhibitors, and all must be considered when selecting the drugs for therapeutic use in humans. The best combination, sequence of use, durability of response, and magnitude of immune reconstitution and function are issues that have yet to be fully elucidated.

ABT-378, a highly potent inhibitor of the human immunodeficiency virus protease

The valine at position 82 (Val 82) in the active site of the human immunodeficiency virus (HIV) protease mutates in response to therapy with the protease inhibitor ritonavir. By using the X-ray crystal structure of the complex of HIV protease and ritonavir, the potent protease inhibitor ABT-378, which has a diminished interaction with Val 82, was designed. ABT-378 potently inhibited wild-type and mutant HIV protease (Ki = 1.3 to 3.6 pM), blocked the replication of laboratory and clinical strains of HIV type 1 (50% effective concentration [EC50], 0.006 to 0.017 microM), and maintained high potency against mutant HIV selected by ritonavir in vivo (EC50, 50-fold after 8 h. In healthy human volunteers, coadministration of a single 400-mg dose of ABT-378 with 50 mg of ritonavir enhanced the area under the concentration curve of ABT-378 in plasma by 77-fold over that observed after dosing with ABT-378 alone, and mean concentrations of ABT-378 exceeded the EC50 for >24 h. These results demonstrate the potential utility of ABT-378 as a therapeutic intervention against AIDS.

Glucuronidation of 3'-azido-3'-deoxythymidine (zidovudine) by human liver microsomes: relevance to clinical pharmacokinetic interactions with atovaquone, fluconazole, methadone, and valproic acid

Zidovudine (3'-azido-3'-deoxythymidine [AZT]), an antiviral nucleoside analog effective in the treatment of human immunodeficiency virus infection, is primarily metabolized to an inactive glucuronide form, GAZT, via uridine-5'-diphospho-glucuronosyltransferase (UGT) enzymes. UGT enzymes exist as different isoforms, each exhibiting substrate specificity. Published clinical studies have shown that atovaquone, fluconazole, methadone, and valproic acid decreased GAZT formation, presumably due to UGT inhibition. The effect of these drugs on AZT glucuronidation was assessed in vitro by using human hepatic microsomes to begin understanding in vitro-in vivo correlations for UGT metabolism. The concentrations of each drug studied were equal to those reported with the usual clinical doses and at concentrations at least 10 times higher than would be expected with these doses. High-performance liquid chromatography was used to assess the respective metabolism and formation of AZT and GAZT. All four drugs exhibited concentration-dependent inhibition of AZT glucuronidation. The respective concentrations of atovaquone and methadone which caused 50% inhibition of GAZT were > 100 and 8 micrograms/ml, well above their usual clinical concentrations. Fluconazole and valproic acid exhibited 50% inhibition of GAZT at 50 and 100 micrograms/ml, which are within the clinical ranges of 10 to 100 and 50 to 100 micrograms/ml, respectively. These data suggest that inhibition of AZT glucuronidation may be more clinically significant with concomitant fluconazole and valproic acid. Factors such as inter- and intraindividual pharmacokinetic variability and changes in AZT intracellular concentrations should be considered as other mechanisms responsible for changes in AZT pharmacokinetics with concomitant therapies.

Multidose pharmacokinetics of ritonavir and zidovudine in human immunodeficiency virus-infected patients

The effect of coadministration of ritonavir and zidovudine (ZDV) on the pharmacokinetics of these drugs was investigated in a three-period, multidose, crossover study. Eighteen asymptomatic, human immunodeficiency virus-positive men were assigned randomly to six different sequences of the following three regimens: ZDV (200 mg every 8 h [q8h] alone for 4 days, ritonavir (300 mg q6h) alone for 4 days, and ZDV with ritonavir for 4 days. Ritonavir pharmacokinetics were unaffected by coadministration with ZDV. However, ZDV exposure was reduced by about 26% (P < 0.05) in the presence of ritonavir. The maximum concentration in (Cmax) of ZDV plasma decreased from 748 +/- 375 (mean +/- standard deviation) to 546 +/- 296, and area under the concentration-time curve from 0 to 24 h (AUC0-24) decreased from 3,052 +/- 1,007 to 2,261 +/- 715 when coadministered with ritonavir. In contrast, the ZDV elimination rate constant was unaffected by ritonavir, suggesting that there was no change in ZDV systemic metabolism. Correspondingly, differences in ZDV-glucuronide Cmax and AUC were not statistically significantly different between regimens (P > 0.31). Also, there were no apparent differences in the formation of 3'-amino-3'-deoxythymidine or in the adverse event profiles between the regimens. The lack of change in ritonavir pharmacokinetics suggests that dosage adjustment of ritonavir is unnecessary when it is administered concurrently with ZDV. The clinical relevance of a 26% reduction in ZDV exposure when ZDV is administered with ritonavir is unknown. In addition to other multidrug regimens, the long-term safety and efficacy of coadministration of ritonavir and ZDV is being investigated.

Inhibition of Friend virus replication by a compound that reacts with the nucleocapsid zinc finger: anti-retroviral effect demonstrated in vivo

The zinc finger structure that is found in the nucleocapsid protein of nearly all retroviruses has been proposed as a target for antiviral therapy. Since compounds that chemically attack the cysteines of the finger have been shown to inactivate both human immunodeficiency virus type 1 (HIV-1) and murine leukemia virus (MuLV) in vitro, 14 of these compounds were tested in an MuLV-induced Friend disease model to assess their ability to inhibit retroviral replication in vivo. Of the 14 compounds tested, only Aldrithiol-2 clearly exhibited anti-retroviral activity as measured indirectly by the delay of Friend disease onset (P < 0.05). These results were confirmed by quantitative competitive polymerase chain reaction studies which monitored viral spread by measuring the level of viral DNA in the peripheral blood mononuclear cells of treated mice. Comparison of treated mice with untreated mice revealed that Aldrithiol-2 produced a greater than 2-log reduction in virus levels. These results functionally demonstrate that a zinc finger-attacking compound can inhibit viral replication in vivo. Since only 1 of the 14 compounds studied was effective, this study also shows the importance of in vivo testing of these types of antiviral compounds in an animal model. Given the strict conservation of the metal-coordinating cysteine structure within HIV-1 and MuLV zinc fingers, our results support the proposal that anti-retroviral drugs which target the nucleocapsid zinc finger may be clinically useful against HIV-1.

Grapefruit juice enhances the bioavailability of the HIV protease inhibitor saquinavir in man

AIMS

Saquinavir is a potent HIV protease inhibitor whose effectiveness is limited in vivo by its low bioavailability. Since saquinavir is metabolized by CYP3A4, the effect of grapefruit juice, an inhibitor of CYP3A4, was investigated on its bioavailability.

METHODS

After an overnight fast, eight healthy volunteers were treated with either 400 ml grapefruit juice or water before intravenous (12 mg) or oral saquinavir (600 mg) was administered. Serial blood samples were obtained over the following 24 h and standardized meals were served 5 and 10 h after the administration of saquinavir. The plasma concentrations of saquinavir were determined by high-performance liquid chromatography and pharmacokinetic parameters were calculated by routine methods.

RESULTS

The AUC was not affected by grapefruit juice after intravenous administration, but it increased significantly from 76+/-96 (water, mean (s.d.) to 114+/-70 (microg l[-1] h) (grapefruit juice) after oral saquinavir. Similarly, the oral bioavailability of saquinavir increased by a factor of 2 with grapefruit juice (from 0.7% to 1.4%). In contrast, clearance, volume of distribution and elimination half-life of saquinavir were not affected by grapefruit juice. After oral, but not after intravenous administration, the plasma concentration-time curve showed a second peak after lunch irrespective of pretreatment, suggesting enhancement of absorption by food.

CONCLUSIONS

The studies demonstrate that grapefruit juice increases the bioavailability of saquinavir without affecting its clearance, suggesting that inhibition of intestinal CYP3A4 may contribute. Since the antiretroviral effect of saquinavir is dose-dependent, inhibition of CYP3A4 may represent a way to enhance its effectiveness without increasing the dose.

Inhibition of murine AIDS by a new azidothymidine homodinucleotide

A new antiretroviral drug (azidothymidine homodinucleotide, AZTp2AZT), designed for the protection of macrophages against retroviral infection, was evaluated in a murine retrovirus-induced immunodeficiency model of AIDS (MAIDS) alone and in combination with oral azidothymidine (AZT). C57BL/6 mice were infected with the retroviral complex LP-BM5 and treated for 3 months by weekly administrations of 15 nmol of AZTp2AZT encapsulated into autologous erythrocytes for macrophage protection. AZTp2AZT treatment was found to reduce lymphoadenopathy (48%), splenomegaly (26%), and BM5d proviral DNA content in lymph nodes, spleen, and brain of 37%, 40%, and 36%, respectively, compared with untreated animals. AZT administration in drinking water (0.25 mg/ml) was more effective than administration of AZTp2AZT encapsulated into erythrocytes in reducing lymphoadenopathy, splenomegaly, gammaglobulinemia, and proviral DNA content in lymph nodes, but it caused a reduction in erythrocyte count and hematocrit levels. Although combined treatments do not provide additive responses in the several parameters investigated, they were found to be much more effective in reducing the proviral DNA content in brain (67%) than were monotherapies. Furthermore, no apparent signs of hematotoxicity were observed. Thus, macrophage delivery of antiviral drugs may contribute to brain protection from retroviral infections by mechanisms other than those exerted by oral AZT administration.

Antiretroviral therapy in the pregnant woman

The use of antiretroviral agents to treat patients infected with HIV has become increasingly complex. Obstetricians caring for the pregnant woman infected with HIV must, no less than the HIV specialist, be familiar with the various medications now available. This article profiles each of the antiretroviral agents currently available, with a focus on issues relevant to the pregnant patient. Strategies for treating the nonpregnant patient and considerations for the use of these strategies in pregnancy also are discussed. Additional information about prophylaxis for common opportunistic infections is included.

Anti-HIV activity of adefovir (PMEA) and PMPA in combination with antiretroviral compounds: in vitro analyses

Adefovir (PMEA, 9-(2-phosphonomethoxyethyl)adenine), an acyclic nucleoside phosphonate analogue is active against retroviruses, hepadnaviruses and herpesviruses. Adefovir dipivoxil, an orally bioavailable prodrug of adefovir is currently in phase III clinical trials for the treatment of HIV and phase II clinical trials for the treatment of HBV infections. PMPA (9-(2-phosphonomethoxypropyl)adenine) is a related acyclic nucleoside phosphonate analogue that has demonstrated potent anti-SIV activity in rhesus macaques and recently has shown marked anti-HIV activity in a phase I clinical study. Since the standard of care for AIDS patients has become combination therapy, the effects of other antiretroviral compounds (d4T, ddC, AZT, ddI, 3TC, nelfinavir, ritonavir, indinavir, and saquinavir) on the anti-HIV activity of adefovir and PMPA were investigated in vitro. Adefovir and PMPA both demonstrated strong synergistic anti-HIV activity in combination with AZT. Adefovir demonstrated minor to moderate synergistic inhibition of HIV replication in combination with PMPA, d4T, ddC, nelfinavir, ritonavir, and saquinavir. PMPA demonstrated minor synergistic inhibition of HIV replication in combination with ddI and nelfinavir (and adefovir). All other combinations showed additive inhibition of HIV replication in vitro. Importantly, no antagonistic interactions were measured for any of the adefovir or PMPA combinations.

Human immunodeficiency virus protease inhibitors. From drug design to clinical studies

The discovery of human immunodeficiency virus (HIV) protease inhibitors is an example in which pharmacokinetic evaluation was implemented early in the discovery phase to obtain optimal pharmacological and pharmacokinetic properties. Currently, three HIV protease inhibitors, saquinavir, indinavir and ritonavir are clinically available. As a family, these HIV protease inhibitors are characterized pharmacologically by their ability to inhibit the viral protease enzyme. Pharmacokinetically, they are quite different due to their dissimilarity in physicochemical properties. Bioavailability appears to be limited with saquinavir, but not with indinavir and ritonavir. Although all three drugs are metabolized extensively by cytochrome P-450, saquinavir and indinavir are high clearance drugs while ritonavir is a low clearance drug. Despite their significant differences in elimination clearance, all three HIV proteases are given at high oral doses (600-800 mg) either twice or three times daily. These HIV protease inhibitors show superior therapeutic activity and a more favorable safety profile than those reported for the established reverse transcriptase inhibitors. However, the potential for interactions with other drugs metabolized by the CYP 3A4 isoform appears to be considerable. In addition, repeated administration of enzyme inducers results in a substantial decrease of plasma concentrations of protease inhibitors. Therefore, co-administration of drugs, such as rifampicin and rifabutin, must be avoided. HIV protease inhibitors are promising in the treatment of AIDS. Although they are not a cure, they can significantly inhibit that viral replication and improve the quality of life for people who have HIV infection.

Overview of protease inhibitors

PURPOSE

To provide a basic review of the four currently available protease inhibitors: saquinavir, ritonavir, indinavir, and nelfinavir. Included are sections on surrogate markers of HIV disease and resistance to protease inhibitor therapy, as well as dosing information, pharmacokinetics, studies, adverse effects, and drug interaction potential.

DATA SOURCES

Conducted a review of published literature (MEDLINE), abstracts from national meetings and conferences, and product labeling and information available at the time of preparation through July 1997.

STUDY SELECTION AND DATA EXTRACTION

Material was selected for inclusion based on relevance to objectives, publication in English, and presence of useful information for practicing pharmacists.

DATA SYNTHESIS

Limited published information is currently available on the protease inhibitors, especially with regard to randomized, controlled, comparative trials and establishment of guidelines for direct therapy. Much of the available information relies heavily on product information and trials that are published only in abstract form. The evaluation of the protease inhibitors (with regard to place in therapy as well as resistance and toxicities) is an ongoing process.

CONCLUSION

Protease inhibitors have changed opinions about the futility of the treatment of HIV disease. Protease inhibitors dramatically improve patients' surrogate markers and even show mortality benefits, especially when combined with additional antiretroviral agents. The optimism surrounding these new drugs is tempered by the toxicity profile, development of resistance, drug interaction profiles, and added costs to current regimens. Designing tolerable, effective regimens will require careful monitoring for compliance, adverse effects, and potential drug interactions.

Antiretroviral effect of combined zidovudine and reduced glutathione therapy in murine AIDS

A combination of antiretroviral drugs acting at different points in the virus replication cycle was evaluated in a murine retrovirus-induced immunodeficiency model of AIDS (MAIDS). Intramuscular administration of high doses of reduced glutathione (GSH, 100 mg/mouse/day) and AZT (0.25 mg/ml in drinking water) was found to reduce lymphoadenopathy (92%), splenomegaly (80%), and hypergammaglobulinemia (90%) significantly more than AZT alone. Combined treatment resulted in a reduction in proviral DNA content of 69, 66, and 60%, respectively, in lymph nodes, spleen, and bone marrow. Furthermore, the stimulation index of B cells was also significantly higher in animals receiving GSH and AZT whereas additional responses were not observed in the T cell stimulation index and blood lymphocyte phenotype analyses. In conclusion, the administration of high doses of GSH and AZT, a new combination of antiviral drugs, seems to provide additional advantages compared to single-agent therapy.

Comparison of hydroxychloroquine with zidovudine in asymptomatic patients infected with human immunodeficiency virus type 1

Hydroxychloroquine (HCQ), an antimalarial agent used to treat patients with autoimmune diseases, has been shown to suppress human immunodeficiency virus type 1 (HIV-1) replication in T cells and monocytes in vitro by inhibiting posttranscriptional modification of the virus. An initial randomized, placebo-controlled clinical trial conducted in 38 asymptomatic HIV-1-infected patients who had CD4+ counts between 200 and 500 cells/mm3 demonstrated that the amount of recoverable virus declined significantly in the HCQ group compared with the placebo group over the 8-week study period. These preliminary observations were expanded into a second 16-week clinical trial comparing the efficacy of HCQ with that of zidovudine (ZDV) in 72 asymptomatic HIV-1-infected patients with CD4+ counts between 200 and 500 cells/mm3. Patients were randomly assigned to receive either HCQ 800 mg/d (n = 35) or ZDV 500 mg/d (n = 37) for 16 weeks. No adverse reactions to the study medications were observed in either the HCQ or ZDV group. Patients in both groups had reduced levels of recoverable HIV-1 RNA in the plasma, reduced levels of cultured virus, and reduced levels of serum p24 antigen after the 16-week study period. However, no difference was noted in absolute CD4+ counts between the two groups. Interleukin-6 and serum immunoglobulin G levels were significantly reduced in the HCQ group but not in the ZDV group. These findings support the results of the previous clinical trial. Thus HCQ may be potentially useful in the treatment of patients with HIV-1 infection.

Theoretical benefits of mitogen applications for HIV-1 infections

Ideal treatment of HIV-1 infections should include an agent that can reverse the capacity of the virus to evade destruction by hiding in sanctuaries and by frequently mutating the epitopes it displays. The rapid proliferation of virions during the years of symptomatic quiescence obligates rapid replacement of CD4+ lymphocytes that leads to a gradual attrition of the T lymphocytes needed to control infections. In vitro evidences suggest that, given systematically, certain mitogenic lectins would interfere with HIV-1 invasion of CD4+ cells by blocking gp120 molecules on the viral membrane before activating T lymphocytes subsequent to binding with their Ti/CD3 molecules. The nonspecific nature of antiviral effector cells generated by this activation should circumvent HIV-1 mutations at the same time it reconstitutes depleted T lymphocytes, stimulates myelopoiesis, and reinforces resistance to malignancies and infections prevalent with the immunodeficiency state. Properly coordinating these effects with appropriate combinations of reverse transcriptase and protease inhibitors could theoretically expedite complete elimination of HIV in a timely fashion that shorten the required treatment duration and excludes the detrimental effects of virus mutations. The proper sequence of this treatment should be maximum reduction of the HIV-1 load with drug combinations, control of complicating infection by other means to reduce mitogen-induced tissue necrosis, and addition of systemic PHA-L4 administration regulated to maintain a 5-10 micrograms/mL serum concentration. The antiviral regimen should be continued an undetermined time beyond when HIV-1 is no longer detectable, and systemic L4 administration until satisfactory immunologic and hematologic competences are re-established. Partially-matched mitogen-activated adoptive leukocyte therapy might be additionally helpful.

Zidovudine toxicity in uninfected healthcare workers. Italian Registry of Antiretroviral Prophylaxis

To evaluate the toxicity of zidovudine (ZDV) prophylaxis in human immunodeficiency virus (HIV)-exposed healthcare workers (HCWs) in Italy, a national protocol for postexposure prophylaxis has been implemented and a national registry has been established. All Italian clinical centers licensed to dispense ZDV participate. As of December 1995, data from 674 individuals who received ZDV prophylaxis have been collected. In three cases ZDV was used in combination with either didanosine (DDI) or dideoxycytidine (DDC). In 556 cases (82%), the daily dose of ZDV was 1,000 mg/day; 21 HCWs (3%) were treated with 300-800 mg/day, and in 72 persons (11%) the dose was 1,200-3,000 mg/day. A total of 332 (49%) HCWs reported at least one adverse effect; 132 (20%) discontinued prophylaxis because of side effects (40% of those reporting side effects). Nausea was reported in 243 cases; other side effects included vomiting, gastric pain, diarrhea, asthenia, and headache. Most constitutional adverse effects were reported during the first week of prophylaxis. Grade 1 anemia (hemoglobin 9.5-11 g/dL) occurred in 10 cases (3%); in 2 cases, the neutrophil count decreased to <1,000 cells/mm3. A transient increase of serum alanine aminotransferase to three times the upper limit of normal was observed in 7 persons. All side effects were reversible after the prophylaxis was stopped. Among those reporting at least one side effect the mean duration of treatment was 22 days; for HCWs reporting hematologic or liver adverse effects the mean length of treatment was 34 days. A total of 351 HCWs (54.6%) ceased the treatment before the scheduled 1-month period. In the 132 persons who discontinued treatment because of side effects, the mean length of prophylaxis was 8 days. One HCW seroconverted after conjunctival exposure to blood. The short-term toxicity of ZDV prophylaxis is frequent, mild, dose related, and reversible. Further studies are needed to assess the risk of long-term sequelae of this treatment as well as of prophylaxis with combinations of antiretroviral drugs.

Antiviral properties of palinavir, a potent inhibitor of the human immunodeficiency virus type 1 protease

Palinavir is a potent inhibitor of the human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2) proteases. Replication of laboratory strains (HIV-1, HIV-2, and simian immunodeficiency virus) and HIV-1 clinical isolates is inhibited by palinavir with 50% effective concentrations ranging from 0.5 to 30 nM. The average cytotoxic concentration of palinavir (35 microM) in the various target cells indicates a favorable therapeutic index. Potent antiviral activity is retained with increased doses of virus and with clinical isolates resistant to zidovudine (AZT), didanosine (ddI), or nevirapine. Combinations of palinavir with either AZT, ddI, or nevirapine demonstrate synergy or additivity in the inhibition of HIV-1 replication. Palinavir retains anti-HIV-1 activity when administered postinfection until times subsequent to the reverse transcription step. In chronically infected CR-10 cells, palinavir blocks Gag precursor polyprotein processing completely, reducing greater than 99% of infectious particle production. The results indicate that the antiviral activity of palinavir is specific to inhibition of the viral protease and occurs at a late stage in the replicative cycle of HIV-1. On the basis of the potent in vitro activity, low-level cytotoxicity, and other data, palinavir was selected for in-depth preclinical evaluation.

Antiretroviral therapy for pregnant women

Reproductive-age women constitute an increasing percentage of individuals infected with human immunodeficiency virus. As clinical management issues particular to pregnancy become increasingly common, they are also becoming increasingly complex. With the approval of new antiretroviral agents, monotherapy with zidovudine, although still standard for prevention of mother-to-child transmission of human immunodeficiency virus, has become inadequate therapy for treatment of the mother. Clinicians must now consider alternative therapeutic strategies in spite of a dearth of experience in the setting of pregnancy. To facilitate optimal drug treatment of human immunodeficiency virus-infected pregnant women while maintaining a focus on prevention of transmission, we reviewed Medline, Reprotox, personal files, and pharmaceutical industry information about the antiretroviral agents currently approved. After summarizing potential beneficial and detrimental effects in both the pregnant and nonpregnant individual, we suggest clinical strategies and discuss the ethical and legal principles that should guide therapeutic decisions in pregnancy.

New Advances in the Pharmacological Treatment of Human Immunodeficiency Virus (HIV) Infection: Focus on Protease Inhibitors

The introduction of a new class of anti-HIV agents, the protease inhibitors, has given new hope to patients with HIV infection. Use of these agents requires the pharmacist to have a complete knowledge of phar macokinetics, adverse reactions, drug-drug interactions, and resistance profiles. Patient compliance is one of the most important factors affecting the success and failure of protease inhibitor therapy. Pharma cists have the opportunity to positively influence outcomes of HIV therapy.

Intracellular expression of single-chain variable fragments to inhibit early stages of the viral life cycle by targeting human immunodeficiency virus type 1 integrase

Integration of viral DNA into a chromosome of the infected host cell is required for efficient replication of a retroviral genome, and this reaction is mediated by the virus-encoded enzyme integrase (IN). As IN plays a pivotal role in establishing infection during the early stages of the retroviral life cycle, it is an attractive target for therapeutic intervention. However, the lack of effective antiviral drug therapy against this enzyme has led to the testing of other novel approaches towards its inhibition. In these studies, a panel of anti-human immunodeficiency virus type 1 (anti-HIV-1) IN hybridomas has been used in the construction of single-chain variable antibody fragments (SFvs). The monoclonal antibodies produced by these hybridomas, and derived SFvs, bind to different domains within IN. We now demonstrate that intracellular expression of SFvs which bind to IN catalytic and carboxy-terminal domains results in resistance to productive HIV-1 infection. This inhibition of HIV-1 replication is observed with SFvs localized in either the cytoplasmic or nuclear compartment of the cell. The expression of anti-IN SFvs in human T-lymphocytic cells and peripheral blood mononuclear cells appears to specifically neutralize IN activity prior to integration and, thus, has an effect on the integration process itself. These data support our previous studies with an anti-HIV-1 reverse transcriptase SFv and demonstrate further that intracellularly expressed SFvs can gain access to viral proteins of the HIV-1 preintegration complex. This panel of anti-HIV-1 IN SFvs also provides the tools with which to dissect the molecular mechanism(s) directly involved in integration within HIV-1-infected cells.

Effects of recombinant interferon-tau on ovine lentivirus replication

As a pregnancy recognition signal, sheep trophoblast cells secrete a type I interferon, ovine interferon-tau (OvIFN-tau), which has potent antiviral activity. We studied the effects of a recombinant protein (rOv-IFN-tau) on the replication of ovine lentivirus (OvLV) in goat synovial membrane cells. The amount of provirus DNA, as measured by polymerase chain reaction (PCR), the virus titers, and the number of OvLV-induced syncytia were 76.5%, 82%, and 95%, respectively, lower in cultures treated with rOv-IFN-tau than in placebo-treated controls (p < 0.01). rOv-IFN-tau also reduced OvLV reverse transcriptase activity and protected cells from OvLV-induced cell lysis, but the effect was less dramatic. The antiviral activity increased with the concentration up to a maximum with 256 antiviral units of rOv-IFN-tau per ml.

Inhibition of HIV-1 replication by hydroxychloroquine: mechanism of action and comparison with zidovudine

We have previously described the inhibition of human immunodeficiency virus serotype 1 (HIV-1) using the antimalarial hydroxychloroquine (HCQ), a weak base that inhibits the posttranslational modification of glycoprotein 120 (gp 120) in T cells and monocytes. The mechanism of inhibition of gp 120 production was presumed to be the ability of HCQ to increase endosomal pH and therefore alter enzymes required for gp120 production. To further clarify this action, we have determined the effect of HCQ and its enantiomers on endosomal pH. Pretreatment of cells with HCQ and the levo- and dextro-enantiomers at concentrations demonstrated to suppress anti-HIV-1 activity increased endosomal pH to levels similar to increases seen with chloroquine and ammonium chloride, two other weak bases, and decreased gp 120 production. The dextro- and levo-enantiomers suppressed HIV-1 replication to a similar extent and were no more toxic than racemic HCQ. We next compared the anti-HIV-1 effect of HCQ with zidovudine (ZDV) in both newly and chronically HIV-1-infected T-cell and monocytic cell lines (63 and 63HIV). HCQ suppressed HIV-1 replication in a dose-dependent manner in both recently and chronically infected T-cell and monocytic cell lines. In contrast, ZDV pretreatment had potent anti-HIV-1 activity in the newly infected T and monocytic cells but not in chronically infected cells. An additive effect of HCQ with ZDV was observed in the newly infected T and monocytic cells but not in the chronically infected cells. Although the anti-HIV-1 effect of HCQ was less than that of ZDV, HCQ may still be potentially useful either as an alternative HIV-1 treatment or in combination with other anti-HIV-1 agents, especially in patients who have rheumatic manifestations of HIV-1 infection.

Antiretroviral drugs for AIDS

Treatment of HIV disease with antiretroviral agents has changed considerably. We now know that monotherapy is not the best strategy in most cases to combat rapid turnover of virus and development of resistance (the exception being mother-to-child transmission) and various combination drug regimens are being explored. Apart from the main drug groups, consisting of nucleoside analogues, proteinase inhibitors, and reverse-transcriptase inhibitors, many new compounds are under development. The timing of therapy may likewise be important, and the indications of benefit from early initiation of treatment need to be confirmed in randomised trials. Overall, there is far more optimism about the use of drugs in HIV infection than there was several years ago.

Targeting human immunodeficiency virus type 1 reverse transcriptase by intracellular expression of single-chain variable fragments to inhibit early stages of the viral life cycle

Novel molecular approaches to inhibit human immunodeficiency virus type 1 (HIV-1) infection have received increasing attention because of the lack of effective antiviral drug therapies in vivo. We now demonstrate that cells can be intracellularly immunized by cytoplasmic expression of single-chain variable antibody fragments (SFv) which bind to the HIV-1 reverse transcriptase (RT) enzyme. The expression of anti-RT SFv in T-lymphocytic cells specifically neutralizes the RT activity in the preintegration stage and affects the reverse transcription process, an early event of the HIV-1 life cycle. Blocking the virus at these early stages dramatically decreased HIV-1 propagation, as well as the HIV-1-induced cytopathic effects in susceptible human T lymphocytes, by impeding the formation of the proviral DNA. These data also demonstrate that intracellular, complete SFvs may gain access to viral proteins of the HIV-1 preintegration complex. These SFvs will provide a tool with which to better understand the molecular mechanisms involved in restricting viral replication in HIV-1-infected cells.

Zidovudine does not affect transplacental transfer or systemic clearance of stavudine (2',3'-didehydro-3'-deoxythymidine) in the pigtailed macaque (Macaca nemestrina)

Stavudine (22 micrograms/min/kg of body weight) was infused alone (via the femoral vein) or simultaneously with zidovudine (66 micrograms/min/kg) to three near-term pregnant macaques. No significant differences were found between the mean steady-state plasma stavudine concentrations in the dam (Cssd) and fetus (Cssf), the stavudine concentration in the amniotic fluid (Cssa), and the ratios Cssf/Cssd and Cssa/Cssf when stavudine was infused alone or in combination with zidovudine. The data obtained indicate that zidovudine administration does not affect the transfer of stavudine across the placenta in Macaca nemestrina.