Clinical Science: Concise Communication
Genetic variation at NNRTI resistance-associated positions in patients infected with HIV-1 subtype C
Grossman, Zehava; Istomin, Valerya; Averbuch, Dianab; Lorber, Margalitc; Risenberg, Klarisd; Levi, Itzchake; Chowers, Michalf; Burke, Michaelg; Yaacov, Nimrod Barh; Schapiro, Jonathan Mi; for the Israel AIDS Multi-Center Study Group
From the National HIV Reference Center, Central Virology Lab, Public Health Laboratories, Ministry of Health, aHillel Jaffe Medical Center, Hadera,bHadassah University Hospital, Jerusalem, cRambam Medical Center, Haifa, dSoroka Medical Center and Ben Gurion University, Beer Sheva, eSheba Medical Center, Tel-Hashomer and Tel Aviv University Sackler Medical School, Tel Aviv, fMeir Medical Center, Kfar-Saba, gTel Aviv Sourasky Medical Center and Tel Aviv University Sackler Medical School, Tel Aviv, and the hDepartment of Computer-Science, School of Mathematics, Tel Aviv University, Tel Aviv, Israel. *See Appendix for additional coauthors.
Correspondence to Z. Grossman, National HIV Reference Center, Central Virology Lab, Sheba Medical Center, Tel Hashomer 52621, Israel. E-mail: Grossman@sheba.health.gov.il
Received: 2 February 2003; revised: 6 August 2003; accepted: 8 September 2003.
Objective: Genetic differences between subtypes of HIV-1, even when not associated with key resistance mutations, are known to affect baseline susceptibility to specific antiretroviral drugs and resistance-development pathways. We studied the prevalence and patterns of non-nucleoside reverse transcriptase inhibitor (NNRTI)-associated mutations in HIV-1 subtype C-infected patients.
Method: We analysed the genetic variation at sites associated with NNRTI and nucleoside reverse transcriptase inhibitor resistance in subtype C- versus B-infected patients, both drug-naive and -experienced. We extended the comparison to subtype B records from the Stanford database.
Results: A total of 150 subtype B and 341 subtype C-infected patients were studied. No significant differences were found in treatment and clinical parameters between the groups. In NNRTI-naive patients, changes in NNRTI positions were present in 9.3% of subtype B- versus 33.1% of subtype C-infected patients (P < 0.001). Differences were seen in both drug-naive (subtype B, 10.0% versus subtype C, 50.1%; P < 0.021) and drug-experienced NNRTI-naive patients (subtype B, 9.0% versus subtype C, 23.8%; P < 0.001). In NNRTI experienced patients, the number of A98G/S changes was significantly higher in subtype C patients treated with either efavirenz or nevirapine (P < 0.0001), and V106M was higher in efavirenz-treated subtype C-infected patients (P < 0.0001). The average mutation rates were 1.26 and 1.67 per patient for subtypes B and C, respectively (P = 0.036). The frequency of nucleoside associated mutations, but not M184V, in treated patients was significantly higher in subgroup B-infected patients (P = 0.028).
Conclusion: Collectively, these data indicate that genetic variation at NNRTI resistance-associated positions such as V106M and A98S is substantially greater in subtype C-infected patients than in subtype B-infected patients. The natural structure of each subtype probably affects the frequency and pattern of drug resistance mutations selected under treatment.
Subtype B HIV-1 is the predominant subtype in the developed countries, but most infected people worldwide carry non-B virus [1,2]. HIV subtypes show characteristic patterns of amino acids expressed at specific positions throughout the viral genome [3–8]. Differences between subtypes exist in the protease and reverse transcriptase (RT) genes [9–16].
Non-nucleoside reverse transcriptase inhibitors (NNRTI) are increasingly used in drug combination therapy [1,17–20]. The evolution of resistance to NNRTI, following treatment with these drugs, has been studied almost exclusively in subtype B-infected individuals [18,21,22]; relatively little is known about NNRTI effects on non-subtype B strains [23–25]. It was shown for the protease gene that differences between subtypes in the baseline polymorphisms may lead to the development of unique patterns of resistance to each drug and to differences in efficacy of particular regimens in the treatment of patients infected with different subtypes .
In Israel, subtypes A, B and C are prevalent [26–31], HAART is available to all patients, and genotypic resistance testing is performed to help guide treatment decisions [32,33]. We performed a comparative analysis of genetic variation in the HIV-1 RT genes of subtype B and subtype C, in drug-naive and drug-experienced patients, focusing on the variation at NNRTI resistance-associated positions.
Clinical specimens and database
Samples were sent to the National HIV Reference Laboratory from HIV treatment centres, along with demographic information, detailed antiretroviral treatment history, current and past CD4 cell counts and HIV RNA levels. All subtype B and C samples submitted between August 1999 and May 2003 are included in this study. Data were compared to the large Stanford public database .
HIV-1 RNA extraction and sequencing
Viral RNA was isolated from patient blood plasma using the QIAamp kit (Qiagen, Hiden, Germany) according to manufacturer's instructions. The RT gene (codons 38–247) was sequenced as described previously .
Chi-square test, Fisher's two-tailed exact test and Mann–Whitney test were used in comparing clinical data and mutation frequencies.
A total of 150 subtype B and 341 subtype C patients were divided (Table 1) into drug-naive (30 subtype B and 87 subtype C), NNRTI-naive (drug treated, but not with NNRTI; 78 subtype B and 164 subtype C), and NNRTI treated (42 subtype B and 90 subtype C). Subtype identification was based on comparing the polymerase sequence with consensus sequences .
Patients and treatments
Subtype B and subtype C patients were treated by the same physicians and in the same clinics. Overall usage of antiretroviral drugs was similar in the two groups. Efavirenz (EFV) and nevirapine (NVP) were commonly used in combination regimens, usually with nucleoside reverse transcriptase inhibitors (NRTI) as the first or second regimen.
Most drug-naive patients had recently been diagnosed. The majority of subtype B patients were born and infected in Israel, former Soviet Union and various western countries. The birthplace of most subtype C patients or of their parents was Ethiopia (93%); 30% of the naive and 11% of treated subtype C patients were infected in Israel. Demographic data varied between the subtype B and C groups in a number of additional parameters: 82% of subtype B patients were male compared to 47.8% of those infected with subtype C; in the subtype C group, 19% were vertically infected children compared with 3.3% in the subtype B group. The main risk groups for subtype B HIV transmission consisted of men who have sex with men, heterosexuals, injecting drug users and receivers of blood transfusion (39%, 29%, 19% and 8%, respectively), while subtype C transmission was through heterosexual relations (81%) and mother-to-child transfer (19%). The viral load and CD4 cell counts at time of treatment failure were similar for the two groups (Table 1, upper section).
Mutations and polymorphisms
Frequencies of nucleoside associated mutations (NAM), M184V, and NNRTI associated mutations are shown in Table 1 (lower section) for three groups: drug-naive patients, treated patients who did not receive NNRTI, and those who received NNRTI. Basic polymorphism in naive subtype C virus was found at positions A98G/S, A62V and V179I. These three mutations were found both in drug-naive subtype C patients infected outside Israel, where the population was not subject to drug treatment, and in those infected in Israel. Only in the latter, additional mutations, both NAM and NNRTI associated, were found, illustrating the emerging problem of resistant virus transmission in this population. Altogether, mutations were found in three of 30 drug-naive subtype B-infected patients (0.1 mutations per patient) and in 44 of 87 drug-naive subtype C-infected patients (0.61 mutations per patient; P < 0.021). Of those, 21 patients had only A98S (16), K101R (2) or V179I (3) and 23 had other mutations, with or without A98G/S. Twelve patients had between two and eight mutations associated with two classes of drugs. A high rate of 0.49 mutations per naive subtype C-infected patient is noted even when A98G/S is excluded.
NNRTI associated mutations were also more frequent in treated subtype C-infected patients than in treated subtype B-infected patients. The frequency difference was most prominent in the NNRTI-naive subtype C-infected treated patients (Table 1, lower section). NNRTI resistance-associated mutations (A98G, L100I, K103N, V106M, V108I, Y181C, Y188C, G190A) and polymorphisms (A98S, K101E, V106I, V179I) pre-existed in NNRTI-naive subtype C-infected patients, while in NNRTI-naive subtype B-infected patients only A98G/S and K103N occurred (Table 1, lower section). K103N was the most prevalent mutation in NNRTI-treated patients, 42.9% and 38.9% in subtype B- and subtype C-infected patients, respectively. Average NNRTI mutation rates in the NNRTI treated group were 1.26 and 1.67 per patient in subtype B- and subtype C-infected patients, respectively; P = 0.036. As previously shown , the overall frequency of NAM was higher (about twofold) in subtype B-infected patients and M184V frequency was similar. The overall frequency of mutations associated with NNRTI was significantly higher in C than in B patients (P = 0.019).
EFV versus NVP
Of 90 subtype C-infected patients treated with NNRTI, 47 were treated with EFV and 37 with NVP as the only NNRTI. Similarly, 24 and 10 of 42 subtype B-infected patients were treated with EFV and NVP, respectively. Choice of drugs was made by the physicians. We examined accumulation of mutations under each treatment and, as our NNRTI-treated B cohort was small, compared our subtype B- and subtype C-infected patients to subtype B patients from the large Stanford database (Tables 2 and 3). The most frequent mutation in both subtypes was K103N. Its frequency was significantly lower in subtype C- (44%) than in subtype B-infected patients (62%) following EFV treatment (P = 0.013) but similar in subtype C and B patients following NVP (32% and 38%; P = 0.604). V106M frequency was significantly higher in EFV-treated subtype C-infected patients (24%) than in subtype B patients treated with this drug (0.3%; P < 0.0001). It was found in one subtype C patient treated with NVP. Among the EFV-treated patients 0.1% subtype B- and 4% subtype C-infected EFV-treated patients carried Y188C (P = 0.008). On the other hand, Y188H/L was higher in EFV-treated subtype B patients than in NVP-treated subtype B patients (13% and 4%, respectively; P = 0.008). Y181C was significantly higher in patients treated with NVP in both subtypes (Tables 2 and 3). Even on the background of natural polymorphism, the frequency of A98G/S was higher in NNRTI-treated subtype C patients (31% and 48% in subtype C, and 10% and 14% in subtype B, for EFV and NVP, respectively); in both subtypes, this value almost doubled following NVP treatment. The frequencies of L100I, L101E/L/I, V108I, V179I, G190A and P225H following treatment with either drug were similar in the two subtypes (data not shown). There was no significant difference between the Israeli and Stanford subtype B-infected patients.
The objective of this study was to elucidate patterns evolved under treatment regimens containing NNRTI. To this end, we have comparatively analysed the genetic variation in the RT gene of subtype B and subtype C HIV-1 from drug-naive and drug-experienced patients. We compared the frequency at which individual drug resistance mutations were selected in subtype B and C patients who failed therapy. We further compared our results to a large public-access database.
Patients in our study were not randomized into specific treatment arms. The patients had different ethnic backgrounds, and this may have affected both adherence and pharmacokinetics. Such issues were not studied here. However, patients were treated by the same physicians in the same clinics. The drugs received, follow-up time, baseline viral load and CD4 cell counts were similar (Table 1). Although all the mutations associated with resistance to NNRTI in subtype B-infected patients were found also in subtype C-infected patients, different patterns and frequencies of specific mutations were found in each subtype. Significant differences in frequency of individual mutations were found only for A98G/S, V106M and Y188C. However, the frequency differences for all of the other mutations combined reached significance, with more NNRTI resistance-associated mutations in subtype C patients. This applies to each of the three groups, drug-naive, NNRTI-naive and NNRTI-treated patients. The relatively high frequency of NNRTI resistance-associated mutations in subtype C-infected patients is conspicuous when compared with other RT mutations, the NAM and M184V. As previously reported, the frequency of NAM was higher in B infected patients and that of M184V was equal in subtype B- and subtype C-infected patients. In contrast, NNRTI resistance-associated mutations appear to accumulate rapidly in subtype C patients and to manifest a unique pattern. Even in subtype C patients who were treated with NRTI, and not with NNRTI, there was an increased frequency of mutations associated with resistance to NNRTI. The implied cross-reactivity between NRTI and NNRTI should be further investigated.
Recently, Brenner et al. found that the V106M mutation confers cross-resistance to NNRTI in subtype C virus . This mutation rarely appears in subtype B patients  or in subtype C patients treated with NVP . Our results confirm these findings: 24% of our EFV-treated subtype C patients and only one (2.7%) of the subtype C patients treated with NVP developed V106M (P < 0.01). Y188C/H/L was found among patients treated for longer periods (and was not among the early appearing mutations); Y188C frequency was higher in subtype C-infected patients treated with EFV and Y188L was higher in those treated with NVP.
V106M and K103N can coexist: of 13 patients who developed V106M, five (38.5%) also had K103N. The prevalence of K103N following EFV treatment was significantly lower in EFV-treated subtype C patients than in subtype B patients treated with this drug. It seems that in some cases V106M arose in subtype C-infected patients at the expense of K103N. Our findings confirm Brenner's in vitro evidence that EFV selects preferentially for V106M in subtype C-infected patients.
Although not conclusive, these data suggest that baseline polymorphism in the subtype C RT influences the rate at which certain mutations develop in patients failing therapy and the mutation pattern. This may be the case also for other non-B subtypes. In spite of the higher mutation frequency in NNRTI-associated RT positions in subtype C-infected patients, we cannot conclude at this stage that the efficacy of NNRTI in the treatment of subtype C patients is lower in these patients than in subtype B patients (differences in viral load or CD4 cell count were insignificant). Prospective clinical trials and phenotypic assays are needed to address this issue.
We thank M. Ofir, of VGI, Israel, for excellent technical assistance. M. Amit and Y. Shaked helped in database development. The Stanford HIV database is under the direction of R. Shafer.
Sponsorship: This work was supported by Bristol-Myers Squibb, Israel.
1. Falloon J, Piscitelli S, Vogel S, Sadler B, Mitsuya H, Kavlick MF, et al. Combination therapy with amprenavir, abacavir, and efavirenz in human immunodeficiency virus (HIV)-infected patients failing a protease-inhibitor regimen: pharmacokinetic drug interactions and antiviral activity. Clin Infect Dis
2. UNAIDS. Report on the global HIV/AIDS Epidemic.
Geneva: UNAIDS; 2000.
3. Gonzales MJ, Machekano RN, Shafer RW. Human immunodeficiency virus type 1 reverse-transcriptase and protease subtypes: classification, amino acid mutation patterns, and prevalence in a northern California clinic-based population. J Infect Dis
4. Carr JK, Salminen MO, Albert J, Sanders-Buell E, Gotte D, Birx DL, et al. Full genome sequences of human immunodeficiency virus type 1 subtypes G and A/G intersubtype recombinants. Virology
5. Carr JK, Laukkanen T, Salminen MO, Albert J, Alaeus A, Kim B, et al. Characterization of subtype A HIV-1 from Africa by full genome sequencing. AIDS
6. Buonaguro FM, Buonaguro L, Del Gaudio E, Tornesello ML, Monaco M, Greco D, et al. V3 region genotyping of HIV isolates in northern Uganda: heteroduplex mobility assay, nucleotide sequence and phylogenetic analysis. Italian-Ugandan Cooperation AIDS Program. Antibiot Chemother
7. Cornelissen M, van den Burg R, Zorgdrager F, Lukashov V, Goudsmit J. Pol gene diversity of five human immunodeficiency virus type 1 subtypes: evidence for naturally occurring mutations that contribute to drug resistance, limited recombination patterns, and common ancestry for subtypes B and D. J Virol
8. Quinnan GV, Jr., Zhang PF, Fu DW, Dong M, Alter HJ. Expression and characterization of HIV type 1 envelope protein associated with a broadly reactive neutralizing antibody response. AIDS Res Hum Retroviruses
9. Kantor R, Fessel WJ, Zolopa AR, Israelski D, Shulman N, Montoya JG, et al. Evolution of primary protease inhibitor resistance mutations during protease inhibitor salvage therapy. Antimicrob Agents Chemother
10. Kantor R, Machekano R, Gonzales MJ, Dupnik K, Schapiro JM, Shafer RW. Human Immunodeficiency Virus Reverse Transcriptase and Protease Sequence Database: an expanded data model integrating natural language text and sequence analysis programs. Nucl Acids Res
11. Grossman Z, Vardinon N, Chemtob D, Alkan ML, Bentwich Z, Burke M, et al. Genotypic variation of HIV-1 reverse transcriptase and protease: comparative analysis of clade C and clade B. AIDS
:1453–1460 [erratum appears in AIDS 2001 15
12. Cane PA, de Ruiter A, Rice P, Wiselka M, Fox R, Pillay D. Resistance-associated mutations in the human immunodeficiency virus type 1 subtype c protease gene from treated and untreated patients in the United Kingdom. J Clin Microbiol
13. Grossman Z, Paxinos E, Auerbuch D, Maayan S, Parkin N, Engelhard D, et al. D30N is not the preferred resistance pathway in subtype C patients treated with nelfinavir.
[Abstract] Antiviral Ther
14. Frater AJ, Beardall A, Ariyoshi K, Churchill D, Galpin S, Clarke JR, et al. Impact of baseline polymorphisms in RT and protease on outcome of highly active antiretroviral therapy in HIV-1-infected African patients. AIDS
15. Vergne L, Peeters M, Mpoudi-Ngole E, Bourgeois A, Liegeois F, Toure-Kane C, et al. Genetic diversity of protease and reverse transcriptase sequences in non-subtype-B human immunodeficiency virus type 1 strains: evidence of many minor drug resistance mutations in treatment-naive patients. J Clin Microbiol
16. Pillay C, Bredell H, McIntyre J, Gray G, Morris L. HIV-1 subtype C reverse transcriptase sequences from drug-naive pregnant women in South Africa. AIDS Res Hum Retroviruses
17. Clevenbergh P, Cua E, Dam E, Durant J, Schmit JC, Boulme R, et al. Prevalence of nonnucleoside reverse transcriptase inhibitor (NNRTI) resistance-associated mutations and polymorphisms in NNRTI-naive HIV-infected patients. HIV Clin Trials
18. Conway B. Initial therapy with protease inhibitor-sparing regimens: evaluation of nevirapine and delavirdine. Clin Infect Dis
19. Moyle GJ, Wilkins E, Leen C, Cheesbrough A, Reynolds B, Gazzard BG. Salvage therapy with abacavir plus efavirenz or nevirapine in HIV-1-infected persons with previous nucleoside analogue and protease inhibitor use. AIDS
20. Raboud JM, Rae S, Vella S, Harrigan PR, Bucciardini R, Fragola V, et al. Meta-analysis of two randomized controlled trials comparing combined zidovudine and didanosine therapy with combined zidovudine, didanosine, and nevirapine therapy in patients with HIV. INCAS study team. J Acquir Immune Defic Syndr
21. Smeaton LM, DeGruttola V, Robbins GK, Shafer RW. ACTG (AIDS Clinical Trials Group) 384: a strategy trial comparing consecutive treatments for HIV-1.[comment]. Control Clin Trials
22. Robbins WA, Witt KL, Haseman JK, Dunson DB, Troiani L, Cohen MS, et al. Antiretroviral therapy effects on genetic and morphologic end points in lymphocytes and sperm of men with human immunodeficiency virus infection. J Infect Dis
23. Loemba H, Brenner B, Parniak MA, Ma'ayan S, Spira B, Moisi D, et al. Genetic divergence of human immunodeficiency virus type 1 Ethiopian clade C reverse transcriptase (RT) and rapid development of resistance against nonnucleoside inhibitors of RT. Antimicrob Agents Chemother
24. Brenner B, Turner D, Oliveira M, Moisi D, Detorio M, Carobene M, et al.
A V106M mutation in HIV-1 clade C viruses exposed to efavirenz confers cross-resistance to non-nucleoside reverse transcriptase inhibitors. AIDS
25. Morris L, Pillay C, Chezzi C, Lupondwana P, Ntsala M, Levin L, et al. Low frequency of the V106M mutation among HIV-1 subtype C-infected pregnant women exposed to nevirapine. AIDS
26. Yust I, Maayan S, Burke M, Vardinon N, Moses A, Burstein R, et al. Clinical, epidemiological and natural history study of HIV-1 infection among seropositive homo/bisexuals in Israel, 1986–92. A collaborative study in three medical centers. Isr J Med Sci
27. Slater PE, Costin C. The epidemiology of adult AIDS and HIV infection in Israel. Isr J Med Sci
28. Pollack S, Ben-Porath E, Fuad B, Raz R, Etzioni A. Epidemiological and serological studies in HIV-infected Ethiopian immigrants to Israel. Acta Paediatr Suppl
29. Pollack S. Epidemiological and immunological study of HIV-seropositive Ethiopian immigrants in Israel. The Israel AIDS Study Group. Isr J Med Sci
30. Maayan S, Shinar E, Aefani M, Soughayer M, Alkhoudary R, Barshany S, et al. HIV-1 prevalence among Israeli and Palestinian blood donors. AIDS
31. Kaplan EH, Kedem E, Pollack S. HIV incidence in Ethiopian immigrants to Israel. J Acquir Immune Defic Syndr Hum Retrovirol
32. Hirsch MS, Brun-Vezinet F, D'Aquila RT, Hammer SM, Johnson VA, Kuritzkes DR, et al. Antiretroviral drug resistance testing in adult HIV-1 infection: recommendations of an International AIDS Society-USA Panel. JAMA
33. Yeni PG, Hammer SM, Carpenter CC, Cooper DA, Fischl MA, Gatell JM, et al. Antiretroviral treatment for adult HIV infection in 2002: updated recommendations of the International AIDS Society-USA Panel. JAMA
Additional contributing coauthors
Dan Engelhard, Shlomo Maayan, Hadassah University Hospital, Jerusalem; Zvi Bentwich, Dina Torten, Kaplan Hospital, Hebrew University Hadassah Medical School, Rehovot; Ella Mendelson, Fernando Mileguir, Daniela Ram, Hagit Rudich, National HIV Reference Center, Central Virology Lab, Public Health Laboratories, Ministry of Health; Eduardo Shahar, Einat Kedem, Sholomo Pollack, Rambam Medical Center, Haifa; Bat Sheva Gotessman, Giora Gotessman, Meir Medical Center, Kfar-Saba, Israel. Cited Here...
This article has been cited 41 time(s).
VirologyConnection subdomain mutations in HIV-1 subtype-C treatment-experienced patients enhance NRTI and NNRTI drug resistanceVirology
Antiviral TherapyPrevalence of HIV type-1 drug-associated mutations in pre-therapy patients in the Free State, South AfricaAntiviral Therapy
Plos OneNucleic Acid Template and the Risk of a PCR-Induced HIV-1 Drug Resistance MutationPlos One
Plos MedicineImpact of HIV-1 subtype and antiretroviral therapy on protease and reverse transcriptase genotype: Results of a global collaborationPlos Medicine
Identification of a novel HIV-1 complex circulating recombinant form (CRF18_cpx) of Central African origin in Cuba
HIV-1 subtypes and response to combination antiretroviral therapy in Europe
Antiviral Therapy, 11(6):
AIDS Research and Human RetrovirusesDrug resistance in plasma and breast milk after single-dose nevirapine in subtype C HIV type 1: Population and clonal sequence analysisAIDS Research and Human Retroviruses
Infection Genetics and EvolutionDistinct resistance mutation and polymorphism acquisition in HIV-1 protease of subtypes B and F1 from children and adult patients under virological failureInfection Genetics and Evolution
AIDS Research and Human RetrovirusesGenotypic resistance to antiretroviral drugs in patients infected with several HIV type 1 genetic forms in CubaAIDS Research and Human Retroviruses
Antimicrobial Agents and ChemotherapyMutation D30N is not preferentially selected by human immunodeficiency virus type I subtype C in the development of resistance to nelfinavirAntimicrobial Agents and Chemotherapy
Journal of VirologyCross-clade inhibition of recombinant human immunodeficiency virus type 1 (HIV-1), HIV-2, and simian immunodeficiency virus SIVcpz reverse transcriptases by RNA pseudoknot aptamersJournal of Virology
New England Journal of Medicine
Medical progress: The challenge of HIV-1 subtype diversity
New England Journal of Medicine, 358():
Journal of NeurovirologyImpact of human immunodeficiency virus (HIV) subtypes on HIV associated neurological diseaseJournal of Neurovirology
Journal of Antimicrobial ChemotherapyEfavirenz: a decade of clinical experience in the treatment of HIVJournal of Antimicrobial Chemotherapy
Plos OneDifferential Drug Resistance Acquisition in HIV-1 of Subtypes B and CPlos One
InfectionHIV genetic diversity: Any implications for drug resistance?Infection
Journal of Medical VirologyThe changing epidemiology of HIV/AIDS at a Minnesota hospital: Impact of demographic change and viral diversityJournal of Medical Virology
The Challenge of HIV-1 Antiretroviral Resistance in Africa in the Era of HAART
AIDS Reviews, 11(2):
Antimicrobial Agents and ChemotherapyDrug Resistance Mutation Profile and Accumulation Kinetics in Human Immunodeficiency Virus-Positive Individuals Infected with Subtypes B and F Failing Highly Active Antiretroviral Therapy Are Influenced by Different Viral Codon Usage PatternsAntimicrobial Agents and Chemotherapy
Antimicrobial Agents and ChemotherapyHIV-1 Protease Codon 36 Polymorphisms and Differential Development of Resistance to Nelfinavir, Lopinavir, and Atazanavir in Different HIV-1 SubtypesAntimicrobial Agents and Chemotherapy
Current Opinion in Pharmacology
New non-nucleoside reverse transcriptase inhibitors (NNRTIs) in development for the treatment of HIV infections
Current Opinion in Pharmacology, 4(5):
Efficacy of antiretroviral therapy in individuals infected with HIV-1 non-B subtypes
AIDS Reviews, 8(2):
Antiviral ResearchNon-nucleoside reverse transcriptase inhibitors (NNRTIs), their discovery, development, and use in the treatment of HIV-1 infection: A review of the last 20 years (1989-2009)Antiviral Research
Clinical Infectious Diseases
Web resources for HIV type 1 genotypic-resistance test interpretation
Clinical Infectious Diseases, 42():
Journal of Infectious Diseases
Rationale and uses of a public HIV drug-resistance database
Journal of Infectious Diseases, 194():
Journal of the Chilean Chemical Society
1-benzoyl-2-(2-nitrophenyl)-1H-benzimidazole derivatives: A novel approach to the development of new HIV-1 reverse transcriptase inhibitors
Journal of the Chilean Chemical Society, 52(4):
Characterization and Structural Analysis of HIV-1 Integrase Conservation
AIDS Reviews, 11(1):
Anales De PediatriaHIV-1 genetic variability in non Spaniard infected childrenAnales De Pediatria
AIDS Research and Human RetrovirusesSingle-stranded DNA aptamer RT1t49 inhibits RT polymerase and RNase H functions of HIV type 1, HIV type 2, and SIVCPZ RTsAIDS Research and Human Retroviruses
Consensus drug resistance mutations for epidemiological surveillance: basic principles and potential controversies
Antiviral Therapy, 13():
Bmc Infectious DiseasesHIV-1 drug resistance in recently HIV-infected pregnant mother's naive to antiretroviral therapy in Dodoma urban, TanzaniaBmc Infectious Diseases
Journal of Antimicrobial ChemotherapySubtype-specific differences in the development of accessory mutations associated with high-level resistance to HIV-1 nucleoside reverse transcriptase inhibitorsJournal of Antimicrobial Chemotherapy
Current Opinion in Infectious DiseasesHIV-1 subtypes: epidemiology and significance for HIV managementCurrent Opinion in Infectious Diseases
Therapeutic Drug MonitoringPharmacokinetics of Plasma Efavirenz and CYP2B6 Polymorphism in Southern ChineseTherapeutic Drug Monitoring
JAIDS Journal of Acquired Immune Deficiency SyndromesThe Calculated Genetic Barrier for Antiretroviral Drug Resistance Substitutions Is Largely Similar for Different HIV-1 SubtypesJAIDS Journal of Acquired Immune Deficiency Syndromes
HIV; subtype B; subtype C; NNRTI; drug resistance; V106M mutation; genetic variation; reverse transcriptase
© 2004 Lippincott Williams & Wilkins, Inc.
What does "Remember me" mean?
By checking this box, you'll stay logged in until you logout. You'll get easier access to your articles, collections,
media, and all your other content, even if you close your browser or shut down your
To protect your most sensitive data and activities (like changing your password),
we'll ask you to re-enter your password when you access these services.
What if I'm on a computer that I share with others?
If you're using a public computer or you share this computer with others, we recommend
that you uncheck the "Remember me" box.
Highlight selected keywords in the article text.
Data is temporarily unavailable. Please try again soon.