Antiviral Therapy

The study was carried out to evaluate the therapeutic effects of zanamivir, a highly selective, potent and specific inhibitor of influenza A and B virus neuraminidases, in adult patients with acute influenzalike illness. Patients who presented within 36 h of the onset of influenza-like symptoms were randomly assigned to receive one of three treatments, twice daily, for 5 days: 10 mg zanamivir powder for inhalation (zanamivir inhalation group), 10 mg zanamivir powder for inhalation plus 6.4 mg zanamivir nasal spray (zanamivir inhalation plus intranasal group) or placebo (placebo group). The primary end point was the time to alleviation of the three major symptoms (fever, headache and myalgia). The secondary end point was the time to alleviation of five influenza symptoms (fever, headache, myalgia, cough and sore throat). One hundred and sixteen patients with influenza-like illness were recruited to the study. No differences were observed between the two groups of patients who received zanamivir (inhalation group or inhalation plus intranasal group). Patients who received zanamivir recovered significantly faster (median 3 days to recovery) than the patients in the placebo group (median 4 days to recovery; P<0.01). Topically administered zanamivir was well tolerated. This study confirms that in adults, topically administered zanamivir is well tolerated and is effective in reducing the time to alleviation of influenza symptoms.

The objective of this randomized double-blind, placebo-controlled trial was to investigate the effect of combination antiretroviral therapy on plasma HIV-1 RNA as measured by HIV RNA PCR and to assess the safety and tolerability of such regimens. The trial was carried out in seven European countries, Australia and Canada and involved antiretroviral-naive patients (n=106) with CD4 counts between 150–300 cells/mm³ (CDC group A) and 150–500 cells/mm³ (CDC group B/C). Patients were randomly assigned to zidovudine (200 mg three times daily) plus lamivudine (300 mg twice daily) or to zidovudine plus lamivudine plus loviride (100 mg three times daily) for 52 weeks. The main outcome measures were degree and duration of reduction of plasma HIV-1 RNA as measured by RNA PCR and the development of drug-related toxicities sufficiently severe to warrant dose modification, interruption or permanent discontinuation. A mild, though statistically significant difference in favour of zidovudine plus lamivudine plus loviride for log₁₀ plasma HIV-1 RNA (P=0.022), as compared to zidovudine plus lamivudine, was observed using area-under-the-curve minus baseline (AUCMB). An increase in CD4 cell count in the zidovudine plus lamivudine plus loviride group was observed with a median improvement of 124 cells/mm³ at week 52 compared with 70 cells/mm³ in the zidovudine plus lamivudine group (P=0.06). Both treatment regimens were well tolerated.

9-(2-phosphonomethoxypropyl)adenine (PMPA) has demonstrated remarkable anti-simian immunodeficiency virus (SIV) activity in macaque models of SIV infection and transmission prevention. Recently, PMPA and its oral prodrug, bis-POC PMPA, have also shown potent anti-human immunodeficiency virus type 1 (HIV-1) activity in Phase I clinical studies. In vitro experiments were performed to address the resistance properties of PMPA. After eight passages in increasing concentrations of PMPA, HIV-1_IIIB was able to grow in the presence of 2 μM PMPA, fivefold above the IC₅₀ of PMPA for wild-type parental virus. Sequence analysis of the reverse transcriptase (RT) genes from four of 15 RT clones demonstrated the presence of a K65R substitution in RT and recombinant HIV expressing the K65R RT mutation showed a threefold to fourfold increase in IC₅₀ value for PMPA as compared to wild-type. Additional experiments demonstrated that viruses expressing other nucleoside-associated RT resistance mutations all showed wild-type or <threefold reduced susceptibility to PMPA in vitro. Interestingly, lamivudine-resistant viruses expressing the M184V RT mutation showed wild-type to slightly increased susceptibility to PMPA in vitro and addition of the M184V mutation to HIV with the K65R mutation resulted in reversion to wild-type susceptibility for PMPA. In agreement with the cell culture findings, Escherichia coli-expressed K65R RT showed fivefold reduced susceptibility to PMPA diphosphate, the active moiety of PMPA. Furthermore, in combination experiments, PMPA with hydroxyurea showed synergistic inhibition of HIV replication in vitro. The potent anti-retroviral activity and favourable resistance profile of PMPA and bis-POC PMPA are being further investigated in ongoing clinical trials.

Direct contact with semen is the major route of sexual acquisition of human immunodeficiency virus (HIV) in homosexual and heterosexual partners of seropositive men. In this study, we show that concentrations of HIV-1 RNA molecules in plasma and semen of seropositive patients are related to the duration and type of anti-retroviral agents used in treatment. In patients treated with zidovudine alone, 1, 3 and 6 months after the start of therapy, the mean HIV-1 load in plasma was reduced by 0.57, 0.38 and 0.21 log₁₀ and in semen by 0.66, 0.50 and 0.15 log₁₀, respectively. In patients treated with zidovudine plus didanosine at months 1, 3 and 6, the mean decrease in plasma HIV-1 RNA was 1.40, 1.25 and 1.12 log₁₀ and in semen 1.10, 1.41 and 1.32 log₁₀, respectively. In patients treated with a combination of a protease inhibitor and two nucleoside analogues the mean log₁₀ decrease was 1.77, 1.83, 1.71 and 2.38 log₁₀ in plasma and 1.17, 1.74, 2.19 and 3.02 log₁₀ in semen at 1, 2, 3 and 4 months, respectively. Treatment with a combination of a protease inhibitor and two nucleoside analogues caused a dramatic decrease in cell-free HIV-1 RNA in semen, which is a reliable measure of viral load. These findings could have implications for the sexual transmission of HIV-1.

The compound 9-(2-phosphonylmethoxyethyl)adenine (adefovir; PMEA) is a potent inhibitor of a number of viruses in vitro, such as human immunodeficiency virus (HIV) type 1 and 2, herpes simplex virus (HSV) type 1 and 2, human papillomavirus virus (HBV) and Epstein–Barr virus (EBV). Adefovir also proved to be effective in vivo against feline immunodeficiency virus (FIV) in cats and simian immunodeficiency virus (SIV) in rhesus monkeys. In an open, non-placebo-controlled trial the antiviral activity of weekly doses of adefovir in nine patients with AIDS or AIDS-related complex was studied for a period of 11 weeks. CD4 cell counts at baseline were between 10 and 450 cells/mm³, HIV-1 RNA levels at baseline were between 24210 copies/ml and 406197 copies/ml. The drug was administered intravenously at a dose of 1000 mg every week and plasma viral load was assessed at multiple points during the study. Administration of adefovir was tolerated well and no severe side effects were seen. The response to adefovir treatment differed widely between patients. The increase in CD4 cell count at end point ranged from -40 to 120 cell/mm³. The lowest HIV RNA levels were measured after 3–5 days, showing an increase thereafter. The nadir in viral load was achieved after 2 weeks, with a mean viral load decline of 0.7 from baseline. The decrease of the HIV RNA level at end point ranged from -0.3 log₁₀ to 1.8 log₁₀, with a mean decrease of 0.4 log₁₀. Our results indicate that adefovir given intravenously once weekly has a short-lasting initial antiviral effect. The effect of more frequent dosing requires further evaluation. If adefovir is to be useful clinically, it needs to be combined with other antiviral agents.

Chemokines are pro-inflammatory cytokines that inhibit human immunodeficiency virus type 1 (HIV-1) replication in vitro. We studied the kinetics of the β-chemokines, macrophage inhibitory protein (MIP)-1α, MIP-1β, RANTES, and monocyte chemotactic protein (MCP)-1 in plasma during 12 months of antiretroviral therapy in 26 HIV-1-infected patients and in 11 untreated subjects. Eleven patients with moderate immunodeficiency had HIV-1 RNA levels <50 copies/ml after 1 year, whereas 12 out of 15 patients with severe immunodeficiency had detectable virus. At baseline, MCP-1 levels correlated positively with HIV-1 RNA and DNA levels and inversely with CD4 cell counts. A reverse pattern was seen for the MIP-1β levels. No correlation was seen between MIP-1α or RANTES and any of the parameters. Also, there was a dichotomy between the different β-chemokines in response to therapy. Decreases of MCP-1 and RANTES levels were found, but no durable changes of MIP-1α and MIP-1β. The MCP-1 levels rebounded back to baseline after 1 year in the patients who responded virologically, which could possibly reflect an increased immune activation. The biological consequences of the changes in β-chemokines levels during antiretroviral treatment are still unknown and deserve further studies.

Sequential use of antiretroviral therapy with protease inhibitors (PI) is frequently prescribed owing to failure or intolerance of the first selected agent. Controversial data exist about the virological and immunological outcome of patients in whom a change to a second PI regimen is needed. A prospective study of 113 HIV-positive patients (male, 84%; mean age 36 years; previous AIDS-defining event, 35%; previous antiretroviral therapy with nucleoside analogues, 94%) who started a saquinavir-containing regimen between March 1996 and March 1997 and had to change to indinavir (n=79) owing to intolerance, failure or medical criteria was performed. At the time of the switch, median CD4 cell count was 221 cells/mm³ and the HIV RNA level was 3.98 log₁₀ copies/ml. The rate of viral suppression (HIV RNA levels below 200 copies/ml) was 40% at 3 months and 28% at month 6 after indinavir was instituted. In a logistic regression analysis, only the baseline viral load [relative risk (RR), 2.85; 95% confidence interval (CI), 1.31–6.05; P=0.007] was statistically associated with the lack of viral suppresion on indinavir. Although there are not sufficient data about the best therapeutic option if a change in PI-containing regimens therapy is considered, this study supports the recommendation of an early change of the PI-containing regimens, before the HIV-1 viral load reaches high levels.

The early recognition of resistance to antiretroviral agents could allow a rapid switch in therapy and therefore avoid the accumulation of mutations and reduce the risk of cross-resistance. However, the efficiency of genotypic tests in specimens with low viral load (VL) is severely compromised since human immunodeficiency virus (HIV) RNA in these samples often goes unrecognized. The frequency of results provided by a line probe assay (LiPA, Murex), a commercially available drug resistance test and a home-made point mutation assay (PMA) for recognizing the codon 151 multidrug-resistance mutation was examined in 664 plasma samples stratified with respect to VL values. Overall, 421 (63%) samples could be interpreted by both LiPA and PMA. The sensitivity decreased as plasma VL lowered: 89% for samples with VL >10000 HIV RNA copies/ml, 77% for those with VL between 500 and 10000 HIV RNA copies/ml and 37% for specimens with VL <500 HIV RNA copies/ml. A good agreement existed comparing the sensitivity of the home-made PMA and LiPA. Although the former tends to produce more results, the difference did not achieve statistical significance. Our results support that new, more sensitive, HIV RNA extraction methods need to be implemented for the rapid recognition of drug-resistant mutants in patients experiencing an early rebound in plasma viraemia.

A novel multidrug-resistance mechanism has been described in human immunodeficiency virus type 1 (HIV-1), which involves the insertion of 6 bp between codons 69 and 70 in the reverse transcriptase (RT) gene. Herein, we report the first two patients in Spain carrying viral populations with the 69-SS insert coupled to the T69S mutation. Both patients were selected because of the lack of signal at positions 69/70 in the LiPA RT test despite being reactive to the remaining probes on the LiPA strip. The presence of the T69SSS complex was confirmed by sequence analysis. A common feature for both subjects was their past history with zidovudine monotherapy and zidovudine plus either didanosine or zalcitabine later on in the presence of persistent virus replication. Remarkably, the introduction of triple therapy in patient 1 soon after the emergence of the insert-containing viral strain produced its total displacement, which correlated with a sustained suppression in viral load.