Small-Molecule HIV Entry Inhibitors Targeting gp120 and gp41.

Interrupting early events in the virus life cycle, such as those prior to the formation of provirus, could effectively prevent HIV-1 infection. HIV-1 entry into host cells is mediated by the envelope glycoprotein (Env) trimer, which is composed of three gp120 exterior glycoproteins and three gp41 transmembrane glycoproteins. Hence, the development of novel inhibitors targeting these two glycoproteins could hold the key to early inhibition of HIV-1 infection. Small-molecule entry inhibitors targeting early events in the virus life cycle comprise a well-established class of useful drugs. Many libraries of small-molecule inhibitors have been established to screen potential drug candidates for a variety of targets based on computer docking, FRET, or peptide-linked assay. This chapter reviews the mechanisms of some small-molecule inhibitors targeting HIV-1 gp120 and gp41 and corresponding high-efficiency screening strategies for potential small-molecule inhibitors.

A first-in-human study of the novel HIV-fusion inhibitor C34-PEG4-Chol.

Long-acting injectable antiretroviral (LA-ARV) drugs with low toxicity profiles and propensity for drug-drug interactions are a goal for future ARV regimens. C34-PEG4-Chol is a novel cholesterol tagged LA HIV-fusion-inhibitor (FI). We assessed pre-clinical toxicology and first-in-human administration of C34-PEG4-Chol. Pre-clinical toxicology was conducted in 2 species. HIV-positive men were randomised to a single subcutaneous dose of C34-PEG4-Chol at incrementing doses or placebo. Detailed clinical (including injection site reaction (ISR) grading), plasma pharmacokinetic (time-to-minimum-effective-concentration (MEC, 25 ng/mL) and pharmacodynamic (plasma HIV RNA) parameters were assessed. In both mice and dogs, no-observed-adverse effect level (NOAEL) was observed at a 12 mg/kg/dose after two weeks. Of 5 men enrolled, 3 received active drug (10 mg, 10 mg and 20 mg). In 2 individuals grade 3 ISR occurred and the study was halted. Both ISR emerged within 12 hours of active drug dosing. No systemic toxicities were observed. The time-to-MEC was >72 and >96 hours after 10 and 20 mg dose, respectively, and mean change in HIV RNA was -0.9 log10 copies/mL. These human pharmacodynamic and pharmacokinetic data, although limited to 3 subjects, of C34-PEG-4-Chol suggest continuing evaluation of this agent as a LA-ARV. However, alternative administration routes must be explored.

A Lipopeptide HIV-1/2 Fusion Inhibitor with Highly Potent In Vitro, Ex Vivo, and In Vivo Antiviral Activity.

Peptides derived from the C-terminal heptad repeat (CHR) region of the human immunodeficiency virus type 1 (HIV-1) fusogenic protein gp41 are potent viral entry inhibitors, and currently, enfuvirtide (T-20) is the only one approved for clinical use; however, emerging drug resistance largely limits its efficacy. In this study, we generated a novel lipopeptide inhibitor, named LP-19, by integrating multiple design strategies, including an N-terminal M-T hook structure, an HIV-2 sequence, intrahelical salt bridges, and a membrane-anchoring lipid tail. LP-19 showed stable binding affinity and highly potent, broad, and long-lasting antiviral activity. In in vitro studies, LP-19 efficiently inhibited HIV-1-, HIV-2-, and simian immunodeficiency virus (SIV)-mediated cell fusion, viral entry, and infection, and it was highly active against diverse subtypes of primary HIV-1 isolates and inhibitor-resistant mutants. Ex vivo studies demonstrated that LP-19 exhibited dramatically increased anti-HIV activity and an extended half-life in rhesus macaques. In short-term monotherapy, LP-19 reduced viral loads to undetectable levels in acutely and chronically simian-human immunodeficiency virus (SHIV)-infected monkeys. Therefore, this study offers an ideal HIV-1/2 fusion inhibitor for clinical development and emphasizes the importance of the viral fusion step as a drug target.IMPORTANCE The peptide drug T-20 is the only viral fusion inhibitor in the clinic, which is used for combination therapy of HIV-1 infection; however, it requires a high dosage and easily induces drug resistance, calling for a new drug with significantly improved pharmaceutical profiles. Here, we have developed a short-lipopeptide-based fusion inhibitor, termed LP-19, which mainly targets the conserved gp41 pocket site and shows highly potent inhibitory activity against HIV-1, HIV-2, and even SIV isolates. LP-19 exhibits dramatically increased antiviral activity and an extended half-life in rhesus macaques, and it has potent therapeutic efficacy in SHIV-infected monkeys, highlighting its high potential as a new viral fusion inhibitor for clinical use.

Incidence and risk factors for liver enzymes elevations in highly treatment-experienced patients switching from enfuvirtide to raltegravir: a sub-study of the ANRS-138 EASIER trial.

BACKGROUND: In the ANRS EASIER trial where treatment-experienced patients switched from enfuvirtide (ENF) to raltegravir (RAL), a high incidence of transaminase elevation was reported in the RAL arm. METHODS: We compared the incidence of emergent liver enzyme elevations (LEE) of grade 2 or more among patients randomized to the maintenance ENF arm or the switch RAL arm up to W24. We also assessed the overall incidence of LEE over the 48-week duration of the trial and baseline risk factors for grade 2 or more alanine aminotransferase (ALT) elevation using univariate and multivariate analyses. RESULTS: During the first 24 weeks, 6/84 (7.1 %) and 2/85 patients (2.4 %) presented with ALT elevation of grade 2 or more in the RAL and ENF arms, respectively (p = 0.21). Grade 2 or more γGT and ALP elevations were seen in 18 and 11 % (p = 0.35), and 5 and 1 % (p = 0.14) of patients in the RAL and ENF arms, respectively. The 48-week incidence of grade 2 or more LEE was 11.6 per 100-pts-years for ALT, 24.5 per 100-pts-years for γ-GT and 4.5 per 100-pts-years for ALP, respectively. In the multivariate analysis, tipranavir/ritonavir use (OR 3.66; 95 % CI [1.20-11.1], p = 0.022) and elevated ALT at baseline (OR 10.3; 95 % CI [2.67-39.6], p < 10(-3)) were significantly associated with a grade 2 or more ALT elevation during follow-up. CONCLUSION: The incidence of LEE was relatively high in these highly treatment-experienced patients switching to a RAL-based regimen. Both tipranavir/ritonavir use and high baseline ALT levels were associated with an increased risk of ALT. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT00454337.

Functional characteristics of the natural polymorphisms of HIV-1 gp41 in HIV-1 isolates from enfuvirtide-naïve Korean patients.

HIV-1 gp41 plays a key role in viral entry. The insertion of Thr at position 4 and Met/Val/Phe substitutions at position 7 are frequently observed in the fusion peptide (FP) motif of gp41 without major enfuvirtide resistance associated with mutation in heptad repeats 1/2 (HR1/2) of HIV-1 isolates from Korean patients. Here, the influence of these mutations on their biological function was evaluated by employing HIV-1 variants with mutant FPs as shown previously and with recombinant HIV-1 using the env genes of 20 HIV-1 isolates from Korean patients. In an infectivity assay, all FP mutants showed lower infectivity than the wild-type NL4-3. In particular, the substitutions at position 7 led to much greater reductions in infectivity than the insertions at position 4. Nevertheless, the replication kinetics of most mutants were similar to those of the wild type, except that the FP mutants with an Ile insertion at position 4 and a Phe substitution at position 7 showed reduced replication. Moreover, most point mutants showed lower IC50 values for enfuvirtide than the wild type, whereas the L7M substitution resulted in a slightly increased IC50 value. The infectivity using the HIV-1 env recombinant viruses decreased in 14 cases but increased slightly in six cases compared with the wild type. Most recombinants were more susceptible to enfuvirtide than the wild type, except for three recombinants that showed slight resistance. Our findings may help to explain the potential mechanisms corresponding to the natural polymorphism of gp41 and to predict the efficiency of enfuvirtide in treatment of HIV-1-infected patients in Korea.

Regimen selection in the OPTIONS trial of HIV salvage therapy: drug resistance, prior therapy, and race-ethnicity determine the degree of regimen complexity.

BACKGROUND: Regimen selection for highly treatment-experienced patients is complicated. METHODS: Using a web-based utility, study team members reviewed antiretroviral (ARV) history and resistance data and recommended individual ARV regimens and nucleoside reverse transcriptase inhibitor (NRTI) options for treatment-experienced participants consisting of 3-4 of the following agents: raltegravir (RAL), darunavir (DRV)/ritonavir, tipranavir (TPV)/ritonavir, etravirine (ETR), maraviroc (MVC), and enfuvirtide (ENF). We evaluated team recommendations and site selection of regimen and NRTIs. Associations between baseline factors and the selection of a complex regimen (defined as including four ARV agents or ENF) were explored with logistic regression. RESULTS: A total of 413 participants entered the study. Participants initiated the first or second recommended regimen 86% of the time and 21% of participants started a complex regimen. In a multivariable model, ARV resistance to NRTI (odds ratio [OR] = 2.2), non-nucleoside reverse transcriptase inhibitor (NNRTI, OR = 6.2) or boosted protease inhibitor (PI, OR = 6.6), prior use of integrase strand transfer inhibitor (INSTI, OR = 25), and race-ethnicity (all P ≤ 0.01) were associated with selection of a complex regimen. Black non-Hispanic (OR = 0.5) and Hispanic participants from the continental US (OR = 0.2) were less likely to start a complex regimen, compared to white non-Hispanics. CONCLUSIONS: In this multi-center trial, we developed a web-based utility that facilitated treatment recommendations for highly treatment-experienced patients. Drug resistance, prior INSTI use, and race-ethnicity were key factors in decisions to select a more complex regimen.

Use of new antiretroviral drugs and classes in Bahia, Brazil: a real life experience on salvage therapy of AIDS patients.

Antiretroviral therapy has significantly evolved in the last decade, with an increasing number of new drugs and classes. Currently, even heavily experienced patients can be successfully treated with new regimens. In Brazil, the recent incorporation of some new antiretroviral drugs made it possible to suppress HIV plasma viremia in most treated patients, with significant benefits in terms of quality of life and survival. However, little has been published on outcomes of patients under new drugs-based regimens. We reviewed the safety and efficacy of antiretroviral regimens using recently introduced drugs in Bahia. Our results confirm that patients using darunavir, raltegravir, enfuvirtide, or etravirine presented with a high rate of virological suppression without significant adverse events, after one year of follow-up.

Pharmacokinetics of sifuvirtide in treatment-naive and treatment-experienced HIV-infected patients.

The pharmacokinetics assessment in two clinical studies of sifuvirtide (a novel HIV fusion inhibitor) was first reported in Chinese HIV patients. Nineteen treatment-naive HIV patients were treated with s.c.(subcutaneous injection) sifuvirtide [10 or 20 mg q.d.(quaque die)] for 28 days in study 1, and eight treatment-experienced HIV patients were treated with s.c. sifuvirtide (20 mg q.d.) in combination with HAART drugs (lamivudine, didanosine, and Kaletra) for 168 days in study 2. In study 1, T1/2 was 17.8 ± 3.7 h for 10 mg group and 39.0 ± 3.5 h for 20 mg group; the mean Cmax of last dose was 498 ± 54 ng/mL for 10 mg group and 897 ± 136 ng/mL for 20 mg group. In study 2, T1/2 was 6.71 ± 2.17 h in treatment-experienced patients. Cmax was 765 ± 288 ng/mL after last 168th dosage. Sifuvirtide showed improved clinical pharmacokinetics characteristics compared with Enfuvirtide, and showed very different pharmacokinetic characteristics between treatment-naive and treatment-experienced patients. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 103:4038-4047, 2014.

Genetic analysis and natural polymorphisms in HIV-1 gp41 isolates from Maputo City, Mozambique.

Enfuvirtide was the first fusion inhibitor approved by the Food and Drug Administration (FDA) in 2003 for HIV-1 infection in treatment-experienced patient. It is the first approved antiviral agent to attack the HIV life cycle in its early stages. For HIV fusion to occur, the HR1 and HR2 domains in the gp41 region need to interact. Enfuvirtide is a synthetic peptide that corresponds to 36 amino acids of the HR2, which competitively binds to HR1 inhibiting the interaction with the HR2 domain thus preventing fusogenic conformation and inhibiting viral entry into host cells. Resistance to enfuvirtide is conferred by mutations occurring in the HR1 region involving residues 36-45. Mozambique, a sub-Saharan country, with an HIV prevalence of 11.5%, provides first line and second line antiretroviral therapy (ART)-based treatment. In poor resource settings such as Mozambique the lack of adequate infrastructures, the high costs of viral load tests, and the availability of salvage treatment have hindered the intended objective of monitoring HIV treatment, suggesting an important concern regarding the development of drug resistance. The general aim of this study was to evaluate naturally occurring polymorphisms and resistance-associated mutations in the gp41 region of HIV-1 isolates from Mozambique. The study included 78 patients naive to ARV treatment and 28 patients failing first line regimen recruited from Centro de Saúde Alto-Maé situated in Maputo. The gp41 gene from 103 patients was sequenced and resistance-associated mutations for enfuvirtide were screened. Subtype analysis revealed that 96% of the sequences were classified as subtype C, 2% as subtype G, 1% as subtype A1, and the other 1% as a mosaic form composed of A1/C. No enfuvirtide resistance-associated mutations in HR1 of gp41 were detected. The major polymorphisms in the HR1 were N42S, L54M, A67T, and V72I. This study suggests that this new class of antiviral drug may be effective as a salvage therapy in patients failing first line regimens in Mozambique. However, further phenotypic studies are required to determine the clinical relevance of the polymorphisms detected in this study.

Virological and immunological response to antiretroviral regimens containing maraviroc in HIV type 1-infected patients in clinical practice: role of different tropism testing results and of concomitant treatments.

We assessed the immunovirological response to antiretroviral regimens containing maraviroc in HIV-infected viremic patients with viral tropism predicted by different assays. We selected antiretroviral treatment-experienced HIV-1-infected patients initiating regimens containing maraviroc after different phenotypic or genotypic viral tropism assays, with at least one HIV-1 RNA determination during follow-up. Survival analysis was employed to assess the virological response as time to HIV-1 RNA <50 copies/ml and immunological response as time to a CD4 cell count increase of ≥ 100/µl from baseline. Predictors of these outcomes were analyzed by multivariate Cox regression models. In 191 treatments with maraviroc, virological response was achieved in 65.4% and the response was modestly influenced by the baseline viral load and concomitant drug activity but not influenced by the type of tropism assay employed. Immunological response was achieved in 58.1%; independent predictors were baseline HIV-1 RNA (per log10 higher: HR 1.29, 95% CI 1.05-1.60) and concomitant therapy with enfuvirtide (HR 2.05, 0.96-4.39) but not tropism assay results. Of 17 patients with baseline R5-tropic virus and available tropism results while viremic during follow-up on maraviroc, seven (41%) showed a tropism switch to non-R5 virus. A significant proportion of experienced patients treated with regimens containing maraviroc achieved virological response. The tropism test type used was not associated with immunovirological response and concomitant treatment with enfuvirtide increased the chance of immunological response. More than half of virological failures with maraviroc were not accompanied by tropism switch.

Updating the use of synthetic peptides as inhibitors of HIV-1 entry.

The use of synthetic peptides as HIV-1 inhibitors has been the object of research over recent years. A large number of peptides that affect different stages of the HIV-1 life cycle have been and continue to be studied due to their possible clinical application in the fight against HIV-1 infection. The main advantages of synthetic peptides as therapeutic agents are their low systemic toxicity, the fact that structural modifications can be made to them and their resulting capacity to mimic certain substrates or epitopes. HIV-1-inhibiting peptides have been identified and/or developed using different methods. Some therapeutic peptides such as enfuvirtide-already approved for clinical use-are derived from HIV-1 itself. Others are natural peptides such as chemokines, defensins or the "virus inhibitory peptide"; while still others have been designed and synthesized based on crystallographic data on HIV-1 proteins or from peptide libraries. Initial attempts at therapeutic applications focused on HIV-coded enzymes (reverse transcriptase, protease and, more recently, integrase). However, structural HIV proteins and, more specifically, the mechanisms that involve the virus in cell infection and replication are now also considered therapeutic targets. Several chemical strategies to improve both the stability of peptides and their pharmacokinetics, including prolonging their half-life, have recently been described in the literature. There is growing an interest in inhibitors that prevent HIV entry into the host cell (fusion inhibitors) which could lead to the development of new antiviral agents. Knowledge of the mechanism of action of fusion inhibitors is essential not only for the development of future generations of entry inhibitors, but also to gain an understanding of the form and kinetics of membrane fusion induced by the virus. The physico-chemical processes involved at the interface between the lipid surface of cells and enveloped viruses (such as HIV-1) are essential to the action of peptides that prevent HIV-1 entry into the host cell. The interaction of these peptides with biological membranes may be related to their inhibition efficiency and to their mechanism of action, as the HIV-1 gp41 glycoprotein is bound and confined between the cellular membrane and the viral envelope.

Short communication: Effectiveness at 48 weeks of switching from enfuvirtide to raltegravir in virologically suppressed multidrug-resistant HIV type 1-infected patients in a Brazilian cohort.

The effectiveness of switching from enfuvirtide to raltegravir in HIV-1-infected patients on a suppressive antiretroviral regimen has been poorly studied in the clinical practice of developing countries. We conducted a multicenter retrospective cohort study in HIV-1-infected, multidrug-experienced adults (≥18 years old) with plasma HIV-1-RNA <400 copies/ml for at least 4 months on an enfuvirtide-containing therapy between 2005 and 2010, in whom the attending physician switched from enfuvirtide to raltegravir. Effectiveness endpoints were measured at week 48 after switch. Analyses were conducted on an intent-to-treat basis and two strategies for handling missing outcome data were used (hereafter, strategies 1 and 2). Overall, 87 patients were eligible for analysis. At baseline, the median CD4(+) T cell count was 400 cells/µl and 91.9% of patients had <50 HIV-1-RNA copies/ml. At week 48, the proportions of patients with plasma HIV-1-RNA <50 and <400 copies/ml were, respectively, 86.2% (95% CI=77.1; 92.7%) and 88.5% (95% CI=79.9; 94.3%) (strategies 1 and 2) and 89.7% (95% CI=81.3; 95.2%) and 90.8% (95% CI=82.7; 95.9%) (strategies 1 and 2). This was a -10.3% (95% CI=-2.8; -17.9%) and -9.2% (95% CI=-2; -16.4%) difference from baseline in the proportion of patients with plasma HIV-1-RNA <400 copies/ml. The median increase in CD4(+) T cell counts was 41 and 64 cells/µl (p<0.001) (strategies 1 and 2). No patient withdrew raltegravir or developed opportunistic infections, but one was diagnosed with HIV-related dementia. In conclusion, switching from enfuvirtide to raltegravir in patients on a virologically suppressive regimen is an effective strategy even in a Brazilian clinical setting.

Decreases in inflammatory and coagulation biomarkers levels in HIV-infected patients switching from enfuvirtide to raltegravir: ANRS 138 substudy.

Stored plasma specimens from 164 participants in the ANRS 138 trial were analyzed to determine interleukin 6 (IL-6), high-sensitivity C-reactive protein (hsCRP), and D-dimer levels at baseline and weeks 24 and 48. These virologically suppressed, treatment-experienced patients were randomly assigned to undergo an immediate switch (IS) or a deferred switch (DS; at week 24) from an enfuvirtide-based antiretroviral therapy (ART) regimen to a raltegravir-based regimen. At week 24, a significant decrease from baseline was observed in the IS arm, compared with the DS arm, for IL-6 level (-30% vs +10%; P < .002), hsCRP level (-46% vs +15%; P < .0001), and D-dimer level (-40% vs +6%; P < .0001). At week 48, there was a reproducible decrease in levels of all biomarkers in the DS arm.

Residual plasma viraemia and infectious HIV-1 recovery from resting memory CD4 cells in patients on antiretroviral therapy: results from ACTG A5173.

BACKGROUND: In HIV-1-infected patients receiving antiretroviral therapy (ART), the relationship between residual viraemia and ex vivo recovery of infectious virus from latently infected CD4 cells is uncertain. METHODS: We measured residual viraemia (HIV-1 RNA copies/ml) by single-copy assay (SCA) and the latent reservoir by infectious virus recovery from resting memory CD4 cells (infectious units per million cells [IUPM]) in patients who initiated ART. We assessed immune activation by measuring CD38 expression on T-cells. RESULTS: Ten patients who initiated ART and maintained a plasma HIV-1 RNA level < 200 copies/ml had residual viraemia and IUPM measured every 24 weeks. Five of 10 patients had longitudinal IUPM measured at weeks 24-96; the remainder had IUPM measured 1-3 times over 24-72 weeks. Analyses of 29 paired measurements revealed a positive association between level of residual viraemia and IUPM (0.56 higher log10 HIV-1 RNA copies/ml per 1 log10 higher IUPM; P = 0.005). Residual viraemia level was positively associated with CD38 density and percentage on CD8+ T-cells in concurrent samples and with pre-ART HIV-1 RNA levels. CONCLUSIONS: In patients with HIV-1 RNA levels < 200 copies/ml 24-96 weeks after initiating ART, the level of viraemia is positively associated with infectious virus recovery from resting memory CD4 cells. Whether this association persists after longer-term suppressive ART needs to be determined. If additional studies show that residual viraemia measured by SCA reflects the size of the latent reservoir in patients who have had virological suppression for longer periods of time, this could facilitate testing of potentially curative strategies to reduce this important reservoir.

Intensification of antiretroviral therapy through addition of enfuvirtide in naive HIV-1-infected patients with severe immunosuppression does not improve immunological response: results of a randomized multicenter trial (ANRS 130 Apollo).

We studied whether addition of enfuvirtide (ENF) to a background combination antiretroviral therapy (cART) would improve the CD4 cell count response at week 24 in naive patients with advanced HIV disease. ANRS 130 Apollo is a randomized study, conducted in naive HIV-1-infected patients, either asymptomatic with CD4 counts of <100/mm(3) or stage B/C disease with CD4 counts of <200/mm(3). Patients received tenofovir-emtricitabine with lopinavir-ritonavir (LPV/r) or efavirenz and were randomized to receive ENF for 24 weeks (ENF arm) or not (control arm). The primary endpoint was the proportion of patients with CD4 counts of ≥ 200/mm(3) at week 24. A total of 195 patients were randomized: 73% had stage C disease, 78% were male, the mean age was 44 years, the median CD4 count was 30/mm(3), and the median HIV-1 RNA load was 5.4 log(10) copies/ml. Eighty-one percent of patients received LPV/r. One patient was lost to follow-up, and eight discontinued the study (four in each arm). The proportions of patients with CD4 counts of ≥ 200/mm(3) at week 24 were 34% and 38% in the ENF and control arms, respectively (P = 0.53). The proportions of patients with HIV-1 RNA loads of <50 copies/ml were 74% and 58% at week 24 in the ENF and control arms, respectively (P < 0.02), and the proportion reached 79% in both arms at week 48. Twenty (20%) and 12 patients (13%) in the ENF and control arms, respectively, experienced at least one AIDS event during follow-up (P = 0.17). Although inducing a more rapid virological response, addition of ENF to a standard cART does not improve the immunological outcome in naive HIV-infected patients with severe immunosuppression.

Enfuvirtide and cutaneous injection-site reactions.

Enfuvirtide belongs to a newer class of antiretroviral (ARV) agents called fusion inhibitors for the treatment of human immunodeficiency virus type 1 (HIV-1) infection. Enfuvirtide blocks attachment, binding, and entry of the viral capsid into the host CD4+ cell. Administration is only available subcutaneously in a twice-daily regimen particularly for those patients who have previously failed more than one ARV regimen. Common side effects of enfuvirtide administration include fatigue, insomnia, nausea, and diarrhea; however, injection-site reactions are the most common side effect and present in nearly all individuals undergoing treatment. The spectrum of cutaneous manifestations ranges from little to no reaction to cysts, nodules, induration, or sclerodermalike lesions. These reactions are mostly variants of iatrogenically induced hypersensitivity and are self-limited.

Monitoring the emergence of resistance mutations in patients infected with HIV-1 under salvage therapy with raltegravir in Rio de Janeiro, Brazil: a follow-up study.

The present study describes a follow-up of a prospective and observational cohort of patients infected with HIV-1 and treated with raltegravir for salvage therapy in Brazil. Two groups of patients were analyzed: switching from T20 to RAL (Group 1, n = 9) and salvage therapy containing RAL (Group 2, n = 10). Blood samples were drawn for CD4(+) T-cell counts and HIV-1 viral load determinations. Protease, reverse transcriptase, and integrase genotyping were performed at baseline and at the time of virologic failure. CD4(+) T-cells increased at 6 and 12 months in both groups; HIV-1 viral load was continuously suppressed for Group 1, and for Group 2 it significantly decreased after starting a RAL-containing regimen. Three out of 10 patients from Group 2 could not suppress HIV-1 viral load. The mutations Q148H + G140S were observed for two patients and for the third patient only mutations to PR/RT inhibitors were detected. The genotypic sensitivity score (GSS) was analyzed for all patients of Group 2 and both patients who developed resistance to raltegravir presented a GSS < 2.0 for the RAL-containing scheme, which could be associated to the lack of effectiveness of the proposed scheme. The present study describes, for the first time in Brazil, the close follow-up of a series of patients using a raltegravir-containing HAART, showing the safety of the enfuvirtide switch to RAL and the effectiveness of a therapeutic regimen with RAL in promoting immune reconstitution and suppressing HIV replication, as well as documenting the occurrence of resistance to integrase inhibitors in the country.

[Analysis of the polymorphism of the genome region of HIV-1 encoding the fusion protein].

The prevalence of the mutations associated with HIV fusion inhibitor enfuvirtide resistance in Russia and CIS countries was studied. Enfuvirtide resistance mutations were not observed among studied viruses in Russia and CIS countries so far. It was found that high rate (35%) of natural polymorphism mutations were associated with enfuvirtide hypersusceptibility. It was also found that high frequency of accessory mutations N126K and E137K were observed in the HR2 region (27.5%). The accessory mutations in HR2 can contribute to increased resistance and improve viral fitness. Our data were compared with those obtained in similar previous studies.