Phenotypic HIV-1 resistance correlates with treatment outcome of nelfinavir salvage therapy

In order to analyse whether drug sensitivity testing would be beneficial for clinical decision-making in heavily pretreated patients, we retrospectively studied viral genotype and phenotypic drug resistance in 12 HIV-1-infected patients, each of them with a history of failing at least one therapeutic regimen including one or two protease inhibitors (PIs). The salvage therapy included nelfinavir as new PI in all cases. Four patients showed a sustained and five patients a transient viral load decrease. Three patients failed to show a significant decline of plasma HIV-1 RNA. In the baseline samples of these cases, resistance against all components of their combination therapy could be detected, whereas at least one antiretroviral drug was still active in the cases with transient treatment response. All patients with sustained therapy response harboured viruses that were either fully sensitive or resistant to only one of the drugs administered. In our study, phenotypic drug resistance was predictive for the success of antiretroviral salvage regimens.     

Persistence of viral HLA-DR- CD4 T-cell reservoir during prolonged treatment of HIV-1 infection with a five-drug regimen

During sustained suppression of plasma viraemia using a standard triple-drug regimen, replication-competent HIV-1 can still be recovered from resting memory CD4 T cells. In an attempt to accelerate the clearance of this pool of infected CD4 T cells, eight antiretroviral therapy-naive HIV-1-infected patients were treated with a five-drug regimen. While plasma HIV-1 RNA levels generally remained below the level of detection (< 5 copies/ml), replication competent HIV-1 was isolated from HLA-DR- CD4 T cells from all patients on multiple occasions throughout treatment. Decay slopes of infected CD4 T cells ranged from -0.061/week (half-life=2.6 months) to +0.003/week (half-life = infinite). Virus was still detectable at the last time point analysed (80-173 weeks) in all patients. Although more intensive treatment results in improved suppression of plasma viraemia compared with standard drug regimens, it does not result in clearance of the viral reservoir in this timeframe. Strategies other than treatment with a combination of five of the currently available drugs need to be pursued in order to achieve eradication of HIV-1 from this cellular reservoir.     

Cerebrospinal fluid HIV-1 infection usually responds well to antiretroviral treatment

The primary objective of this retrospective study was to determine how many patients in routine practice who were treated with combination antiretroviral treatment reached HIV-1 RNA levels below 50-400 copies/ml in cerebrospinal fluid (CSF). Seventy-four antiretroviral-naive HIV-1-infected patients from five different centres in Germany, Italy, Sweden and the USA were included. Thirty-nine percent of the patients had a HIV-1-associated neurological disease and 53% of the patients had AIDS. HIV-1 RNA in CSF and plasma were quantified before and after approximately 3 months of treatment. At baseline, the median value of HIV-1 RNA in CSF was 4.12 log copies/ml (interquartile range (IQR): 3.28-4.85) and it decreased to < 1.70 log copies/ml (IQR: < 1.70-2.48; P < 0.001) after in median 3 months of treatment. Seventy-six percent of the patients had HIV-1 RNA levels below the limits of detection in CSF at follow-up, and 85% reached below 400 copies/ml. In plasma, 45% of the patients had levels of HIV-1 RNA below the limits of detection at follow-up and 80% reached below 400 copies/ml. The group of patients with a neurological disease had a significantly higher CSF viral load both at baseline and at follow-up compared with the neurologically asymptomatic patients. We conclude that the central nervous system (CNS) is usually not a 'sanctuary site', difficult to reach with combination antiretroviral treatment.     

HIV-1 replication cycle

The HIV-1 is a formidable pathogen with establishment of a persistent infection based on the ability to integrate the proviral genome into chronically infected cells, and by the rapid evolution made possible by a high mutation rate and frequent recombination during the viral replication. HIV-1 has a variety of novel genes that facilitate viral persistence and regulation of HIV replication, but this virus also usurps cellular machinery for HIV replication, particularly during gene expression and virion assembly and budding. Recent success with antiretroviral therapy may be limited by the emergence HIV drug resistance and by toxicities and other requirements for successful long-term therapy. Further investigation of HIV-1 replication may allow identification of novel targets of antiretroviral therapy that may allow continued virus suppression in patients of failing current regiments, particularly drugs that target HIV-1 entry and HIV-1 integration.     

Early therapy in HIV-1-infected children: effect on HIV-1 dynamics and HIV-1-specific immune response

BACKGROUND: Perinatal HIV-1 infection is acquired in the milieu of a developing immune system, leading to high levels of uncontrolled viral replication. Few data have been reported that address the viral dynamics and immunological response in infants who initiated aggressive antiretroviral therapy (ART) shortly after birth. METHODS: Six HIV-1-infected infants who started ART within 3 months of age were studied. The median followup was 61 months. Plasma HIV-1 RNA, cell-associated HIV-1 DNA, unspliced and multiply spliced HIV-1 mRNAs, HIV-1 antibodies, and CD4+ and CD8+ T-cell subsets were assessed in sequential peripheral blood samples. HIV-1 cellular immune response was measured by EliSpot assay. RESULTS: All children showed a decline in plasma viraemia to undetectable levels. HIV-1 DNA persisted in four children, but only two of these had detectable HIV-1 mRNA. All viral parameters remained persistently negative in two children. Only two children produced HIV-1 antibodies, while the others, after having lost maternal antibodies, remained seronegative. No HIV-1 cellular immune response was observed in any child. Therapy interruption was performed in two children: one HIV-1-seropositive and one HIV-1-seronegative with persistently undetectable levels of all viral parameters. Rebound of HIV-1 plasma viraemia in the seronegative child was more rapid and higher than that observed in the seropositive child. CONCLUSIONS: Early ART treatment in infants modifies the natural course of infection by controlling HIV-1 replication and reducing viral load to below the threshold levels required for onset of HIV-1 immune response, but does not prevent the establishment of a reservoir of latently infected cells that precludes virus eradication.     

alpha-Tocopherol as an antiretroviral therapy supplement for HIV-1-infected patients for increased lymphocyte viability.

The aim of our study was to evaluate the benefits of supplementation with 800 mg/day of alpha-tocopherol with regard to cellular viability in HIV-1 seropositive patients undergoing anti-retroviral therapy. A total of 29 patients participated in the study, of whom 14 were given the supplement and 15 a placebo. The analyses were carried out before treatment commenced and after 60, 120 and 180 days. The plasma levels of HIV-1 RNA showed a significant decrease as a consequence of treatment time in the groups studied (p = 0.0001), although the difference between the treatments over time was not verified (p = 0.7343). The percentage of viable lymphocytes showed a significant increase as a consequence of treatment time in both groups studied (p = 0.0002) and a significant difference between the treatments over time (p = 0.0472). The percentage of lymphocytes in apoptosis showed a significant reduction over time (p = 0.0003), as well as a significant difference between the treatments over time (p = 0.0321). The significant increase in cellular viability indicates that supplementation with alpha-tocopherol offers an additional positive effect on cellular preservation in HIV-1 individuals undergoing anti-retroviral therapy; however, it represents an additional risk of anti-retroviral therapeutic failure, possibly due to drug-drug interaction involving up-regulation of metabolic clearance.     

HIV-1 integrase inhibitors: 2005-2006 update

HIV-1 integrase (IN) catalyzes the integration of proviral DNA into the host genome, an essential step for viral replication. Inhibition of IN catalytic activity provides an attractive strategy for antiretroviral drug design. Currently two IN inhibitors, MK-0518 and GS-9137, are in advanced stages of human clinical trials. The IN inhibitors in clinical evaluation demonstrate excellent antiretroviral efficacy alone or in combination regimens as compared to previously used clinical antiretroviral agents in naive and treatment-experienced HIV-1 infected patients. However, the emergence of viral strains resistant to clinically studied IN inhibitors and the dynamic nature of the HIV-1 genome demand a continued effort toward the discovery of novel inhibitors to keep a therapeutic advantage over the virus. Continued efforts in the field have resulted in the discovery of compounds from diverse chemical classes. In this review, we provide a comprehensive report of all IN inhibitors discovered in the years 2005 and 2006.     

A combination of nucleoside analogues and a protease inhibitor reduces HIV-1 RNA levels in semen: implications for sexual transmission of HIV infection

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 antiretroviral 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.     

Short-term anti-HIV activity of the combination of didanosine and hydroxyurea

The synergistic action of hydroxyurea with some other antiretroviral drugs led us to evaluate the effect of therapy with the combination of didanosine and hydroxyurea in HIV-1-infected patients. We aimed to assess the anti-HIV activity of therapy with this combination by measuring variations in viral load and in CD4 cell counts. We also evaluated the potential side effects of this drug combination in HIV-1-positive patients with advanced disease. A total of 15 HIV-1-seropositive homosexual men with a mean baseline CD4 cell count of 149 cells/mm3 (range: 1-430 cells/mm3) were recruited to the study, and received didanosine (200 mg) plus hydroxyurea (500 mg) twice daily for 12 weeks. Ten patients were didanosine naive and five had previously received didanosine (for > 3 months). The combination therapy was well tolerated, although grade 2-3 alopecia appeared in four patients who had very low CD4 cell counts (< 50 cells/mm3). No significant variation in renal, hepatic and pancreatic functions occurred. A significant reduction in the plasma HIV-1 RNA (> 0.5 logs) was observed in seven of ten patients naive to didanosine after weeks 4 and 12 of the study; five of these patients had a decrease in plasma HIV-1 RNA of > 1.5 logs, with two having a decrease of > 2.0 logs. The viral load became undetectable (below 200 copies/ml) in three patients. The patients whose plasma HIV-1 RNA levels were not significantly reduced by the combination therapy had a higher baseline viral load. CD4 cell counts did not increase significantly in most patients. We observed a better response in those patients who had virus of the non-syncytium-inducing phenotype. In conclusion, hydroxyurea in combination with didanosine was well tolerated and led to a reduction in viral load mainly in patients who were initially naive to didanosine.     

Relationship between changes in thymic emigrants and cell-associated HIV-1 DNA in HIV-1-infected children initiating antiretroviral therapy

OBJECTIVES AND METHODS: To investigate the relationship between cell-associated HIV-1 dynamics and recent thymic T-cell emigrants, HIV-1 DNA and T-cell receptor rearrangement excision circles (TREC, a marker of recent thymic emigrants) were measured in peripheral blood mononuclear cells in 181 samples from 33 HIV-1-infected children followed for 96 weeks after antiretroviral therapy (ART) initiation. RESULTS: At baseline, HIV-1 DNA was higher in children with higher TREC (P=0.02) and was not related to age, CD4 or HIV-1 RNA in multivariate analyses (P>0.3). Overall, TREC increased and HIV-1 DNA decreased significantly after ART initiation, with faster HIV-1 DNA declines in children with higher baseline TREC (P=0.009). The greatest decreases in HIV-1 DNA occurred in children with the smallest increases in TREC levels during ART (P=0.002). However, this inverse relationship between changes in HIV-1 DNA and TREC tended to vary according to the phase of HIV-1 RNA decline (P=0.13); for the same increase in TREC, HIV-1 DNA decline was much smaller during persistent or transient viraemia compared with stable HIV-1 RNA suppression. CONCLUSIONS: Overall, these findings indicate that TREC levels predict HIV-1 DNA response to ART and suggest that immune repopulation by thymic emigrants adversely affects HIV-1 DNA decline in the absence of persistent viral suppression, possibly by providing a cellular source for viral infection and replication.     

Human monoclonal antibodies to HIV-1 infection

HIV-1, which causes AIDS, has infected over 50 million and killed over 20 million individuals world wide since the beginning of the epidemic two decades ago. The introduction of highly active anti-retroviral therapy(HAART) has resulted in the control of the disease progression. Furthermore, supervised treatment interruption(STI) of HAART might be expected significantly to boost immune function and slow the progression of AIDS. On the other hand, several combinations of human monoclonal antibodies(hu-mo-Ab) against HIV-1 has been identified, and demonstrates the efficacy of the triple combination of hu-mo-Ab with neutralizing activity in macaque model. Therefore, a combination of chemotherapy and immunotherapy, such as hu-mo-Ab will be prove to be the most effective route for HIV-1 therapy.     

Evaluation of two commercial procedures for quantification of human immunodeficiency virus type 1 RNA with respect to HIV-1 viral subtype and antiviral treatment

To determine the reliability of two commercial assays for quantifying the human immunodeficiency type 1 (HIV-1) RNA levels in patients infected with different HIV-1 subtypes and managed with various drug regimens, blind testing of 127 plasma samples from 57 patients infected with HIV-1 subtypes A, B, C and E was performed using the Amplicor HIV-1 Monitor Test (Roche) and Quantiplex HIV-1 RNA 3.0 Assay (Chiron). Included were time course studies in 7 patients in whom the virus load was correlated with CD4+ cell counts and therapy. Both assays were accurate and precise to measure standardized amounts of viral load and displayed high correlation coefficients that were independent of gender and treatment modality, even though some assay-specific differences may exist in the quantification of viral subtype RNA. Time course studies showed comparable inverse associations between the CD4+ count and viral load measured by the two assays. Hence, both the Amplicor HIV-1 Monitor Test and the Quantiplex HIV-1 RNA 3.0 Assay promise to be useful for the management of HIV-1 infected patients.     

Cytotoxic T lymphocytes and viral evolution in primary HIV-1 infection

Efforts to develop immune-based therapies for HIV infection have been impeded by incomplete definition of the immunological correlates of protection. Despite many precedents demonstrating that CD8(+) cytotoxic T lymphocytes are key mediators of protective anti-viral immunity in non-human animal models, direct evidence that these effector cells control viral replication in HIV-1 infection has remained elusive. The first part of this paper describes a detailed immunological and genetic study founded on evolutionary considerations. Following infection with HIV-1, virus variants which escaped recognition by autologous cytotoxic T lymphocytes were shown to possess a selection advantage within the host environment. Cytotoxic T lymphocytes therefore exert anti-viral pressure in vivo. This observation provides compelling evidence that cytotoxic T lymphocytes comprise a significant element of anti-retroviral immunity. Subsequently, the quantification of peripheral cytotoxic T lymphocyte frequencies utilizing peptide-(human leucocyte antigen class I) tetrameric complexes is described. Five patients with qualitatively similar immunodominant cytotoxic T lymphocyte responses during symptomatic primary HIV-1 infection were studied longitudinally. Expansions of virus-specific CD8(+) lymphocytes comprising up to 2% of the total CD8(+) T cell population were observed in the acute phase of infection. Antigenic load was identified as an important determinant of circulating HIV-1-specific CD8(+) lymphocyte levels; however, significant numbers of such cells were also found to persist following prolonged therapeutic suppression of plasma viraemia. In addition, an analysis of antigenic sequence variation with time in this case series suggests that the early administration of combination anti-retroviral therapy may limit HIV-1 mutational escape from host cytolytic specificities. The implications of these preliminary data are discussed. The data presented suggest that vaccination protocols should aim to elicit vigorous cytotoxic T lymphocyte responses to HIV-1. Attempts to stimulate polyvalent responses to mutationally intolerant epitopes are likely to be most effective. Optimal management of HIV-1 infection requires an understanding of dynamic host-virus interactions, and may involve strategies designed to enhance cytotoxic T lymphocyte activity following periods of anti-retroviral drug therapy.