Analysis of HIV-1 reverse transcriptase and protease sequences in paired plasma and lymphoid tissue specimens from HIV-1 infected individuals

Persistence of drug-resistant HIV-1 and possible implications for antiretroviral therapy

Antiretroviral therapy has significantly reduced the morbidity and mortality of subjects infected with HIV-1. However, the establishment of persistent infection and the development of drug-resistant variants are major obstacles facing the eradication of HIV-1. This review summarizes the current knowledge of the persistence of drug-resistant HIV-1 acquired by transmission, or due to therapy failure and the possible implications for antiretroviral therapeutic strategies.

Diversity, divergence, and evolution of cell-free human immunodeficiency virus type 1 in vaginal secretions and blood of chronically infected women: associations with immune status

Most human immunodeficiency virus type 1 (HIV-1) infections are believed to be the result of exposure to the virus in genital secretions. However, prevention and therapeutic strategies are usually based on characterizations of HIV-1 in blood. To understand better the dynamics between HIV-1 quasispecies in the genital tract and blood, we performed heteroduplex assays on amplified env products from cell-free viral RNA in paired vaginal secretion (VS) and blood plasma (BP) samples of 14 women followed for 1.5 to 3.5 years. Diversity and divergence were less in VS than in BP (P = 0.03 and P < 0.01, respectively), and divergence at both sites was correlated with blood CD4(+) cell levels (VS, P = 0.05; BP, P = 0.01). Evolution of quasispecies was observed in 58% of the women; the loss or gain of quasispecies in VS or BP was always accompanied by such changes at the other site. In addition, sustained compartmentalization of quasispecies in VS was found for four women, even as CD4(+) cell levels decreased to low levels (<50 cells/microl). Quasispecies changes over time were associated with fluctuations in CD4(+) cell levels; concordant increases or decreases in VS and BP divergence had greater CD4(+) cell level changes than intervals with discordant changes (P = 0.05), and women with evolving quasispecies had greater decreases in CD4(+) cell levels compared to that for women who maintained the same quasispecies (P < 0.05). Thus, diversity, divergence, and evolution of cell-free HIV-1 in VS can be different from that in BP, and dynamics between their respective quasispecies are associated with changes in CD4(+) cell levels.

Analysis of the protease sequences of HIV-1 infected individuals after Indinavir monotherapy

BACKGROUND

Protease inhibitors (PI) are an important HIV-1 treatment tool. The HIV-1 genetic diversity as a result of antiretroviral exposure is a potential barrier to successful antiretroviral therapy.

OBJECTIVES

To describe the impact of the selective pressure of the PI Indinavir in the protease region of the pol gene of HIV-1.

STUDY DESIGN

We have examined the extent of protease sequence heterogeneity in previously antiretroviral drug naive HIV-1 infected individuals receiving Indinavir as monotherapy for at least 48 weeks.

RESULTS

Analysis based on the consensus of this group of sequences showed regions with higher and lower polymorphism. The degree of genetic variation was greater in regions less critical for the structure and function of the enzyme. To investigate the selective pressure imposed by drug therapy, we have analyzed the rate of synonymous (ds) and nonsynonymous (dn) substitutions. The three critical regions for enzyme activity showed ds/dn ratio >1. whereas other regions had ds/dn ratio <1. The detected amino acid mutations had a trend to be conservative, thus maintaining the physical chemical amino acid characteristics. Phylogenetic analysis established the presence of subtype B (n=38), subtype F (n=9), and B/F recombinants within the protease region of pol gene (n=3). More prevalent detected mutations, thought to contribute to antiretroviral resistance, were L63P (42%), L10I (35%), M36I (30%), V82A/T/F (26%).

CONCLUSIONS

A great deal of predicted cross-resistance between PIs was observed. Out of the 50 individuals, 34% were considered to have major mutations to Indinavir, and 66% had minor or no mutations to Indinavir. Viral loads were significantly higher among patients with major mutations, compared with patients minor/no mutations, although no differences in the CD4 counts were found. The viral load at baseline and nadir (week 4) was able to predict the group of individuals with greater chances of selecting drug resistance related mutations.

Intermittent administration of high-dose stavudine to nucleoside-experienced individuals infected with HIV-1

To explore a novel method to use nucleosides in heavily treated patients, 4-week cycles of high-dosage (280 mg/d) stavudine were given to 11 asymptomatic patients who had previously received an average of 6 years of nucleoside reverse transcriptase inhibitors (NRTIs). The stavudine dose was targeted to produce a calculated steady-state concentration of 1.5 microM (336 ng/mL). Participants received stavudine for the first 4 weeks, after which it was discontinued for 4 weeks. Additional 4-week drug cycles were given if plasma HIV-1 RNA levels increased to at least 75% of baseline values. The 11 subjects received 38 cycles (average, 3.5 cycles per subject) during the 44-week study. Stavudine was well tolerated. Considering all data, there was a median 0.65 log(10) reduction in viral load as well as a median increase in CD4 cell count of 110/mm3 at the end of the cycles. However, plasma viremia increased and CD4 cell counts decreased between cycles. Viral load and CD4 cell responses were similar for up to 4 successive cycles. This suggested that increasing viral resistance was not a problem, as reflected by the acquisition of only one new nucleoside reverse transcriptase mutation among the participants. Significant relationships between stavudine exposure and changes in plasma HIV RNA levels were observed. A similar approach might be considered using a more potent regimen for patients in whom resistance to nucleosides is a major reason for therapeutic failure.

Mutational patterns of paired blood and rectal biopsies in HIV-infected patients on HAART

Blood and concurrent rectal biopsy samples of human immunodeficiency virus type 1 (HIV-1)-positive highly active antiretroviral therapy (HAART)-treated patients were tested for genotypic resistance by direct sequencing of reverse transcriptase (RT) and protease (PR) regions to compare the patterns of resistance in these compartments. Fourteen subjects (five with undetectable plasma viral load (pVL) and nine persistently viremic) were studied. Four of five patients with undetectable pVL also had undetectable mucosal HIV RNA; sequence analyses from proviral DNA (PBMCs and rectal biopsy) were obtained with none or few resistance-associated mutations and no alteration of susceptibility profile. All viremic patients, and one with negative pVL, had detectable levels of mucosal HIV RNA (1.93-4.21 log(10) copies/mg); sequences of HIV RNA (plasma and/or rectal biopsy) were also obtained, and multiple mutations generally compatible with current/past medications were detected. Overall, 40 HIV-1 PR and 42 RT sequences were analyzed, yielding a total of 42 PR and 47 RT sequence pairs (plasma/tissue-RNA; plasma-RNA/tissue-DNA; PBMC/tissue-DNA; tissue-DNA/RNA; tissue-RNA/PBMC-DNA; PBMC-DNA/plasma-RNA), which almost always differed at the total amino acid level (median percentage discordance 8.08% in the PR, 4.8% in RT). The median percentage of resistance position discordance equaled 88.8% (IQR = 20-100) in the PR and 74.55% (IQR = 31.75-100%) in the RT pairs, respectively. Different resistance levels were detected by means of a computer-assisted interpretation of mutational profiles. The results support the multiform evolution of HIV genotype in various body compartments and emphasize the participation of intestinal mucosa in HIV genotype selection. Samples from diverse tissues should be used for resistance evaluation to obtain a complete picture of drug resistance for antiretroviral-treated patients.

[Recommendations of the Spanish AIDS Study Group (GESIDA) and the National Aids Plan (PNS) for antiretroviral treatment in adult patients with human immunodeficiency virus infection in 2002]

OBJECTIVE

To provide an update of recommendation on antiretroviral treatment (ART) in HIV-infected adults.Methods. These recommendations have been agreed by consensus by a committee of the spanish AIDS Study Group (GESIDA) and the National AIDS Plan. To do so, advances in the physiopathology of AIDS and the results on efficacy and safety in clinical trials, cohort and pharmacokinetics studies published in biomedical journals or presented at congresses in the last few years have been reviewed. Three levels of evidence have been defined according to the data source: randomized studies (level A), case-control or cohort studies (level B) and expert opinion (level C). Whether to recommend, consider, or not to recommend ART has been established for each situation.

RESULTS

Currently, ART with combinations of at least three drugs constitutes the treatment of choice in chronic HIV infection. In patients with symptomatic HIV infection, initiation of ART is recommended. In asymptomatic patients initiation of ART should be based on the CD41/mL lymphocyte count and on the plasma viral load (PVL): a) in patients with CD41 lymphocytes < 200 cells/mL, initiation of ART is recommended; b) in patients with CD41 lymphocytes between 200 and 300 cells/mL, initiation of ART should, in most cases, be recommended; however, it could be delayed when the CD41 lymphocyte count remains close to 350 cells/mL and the PVL is low, and c) in patients with CD41 lymphocytes > 350 cells/mL, initiation of ART can be delayed. The aim of ART is to achieve an undetectable PVL. Adherence to ART plays a role in the durability of the antiviral response. Because of the development of cross-resistance, the therapeutic options in treatment failure are limited. In these cases, genotypic analysis is useful. Toxicity limits ART. The criteria for ART in acute infection, pregnancy and postexposure prophylaxis and in the management of coinfection with HIV and hepatitis C and B virus are controversial.

CONCLUSIONS

The current approach to initiating ART is more conservative than in previous recommendations. In asymptomatic patients, the CD41 lymphocyte count is the most important reference factor for initiating ART. Because of the considerable number of drugs available, more sensitive monitoring methods (PVL) and the possibility of determining resistance, therapeutic strategies have become much more individualized.