Mechanism of HIV drug resistance. Rodrigo Brindeiro / Amilcar Tanuri Laboratório de Virologia Molecular UFRJ 2 -Asso ciate Research Scientist, Internatio nal Center fo r Aids Care and Treatment Programs-ICAP, Mailman Scho ol of Public Health, Co lumbia Univ ersity, NY, USA. HIV virus and infected CD4+ T cells Sic Transit Gloria Mundi. Ad Majorem Dei Gloriam In Hoc Signo Vinces. Nobel 2008 Harald zur Hausen Françoise Barré-Sinoussi Luc Montagnier Ciclo replicativo do HIV HIV life cycle and Classes of ARV Available 25 drugs approved to treat HIV/AIDS HPV HIV Fusion Inhibitors Protease Inhibitors CCR5 Inhibitors NRTI and NNRTI Inhibitors Integrase Inhibitors Mortality Rate Tendency Related to Aids Brazil, 1990-1999. 14,0 12,0 (x 100.000 hab.) 10,0 8,0 6,0 4,0 Hunt R at all 2002 Microbiol & Immun 2,0 0,0 90 91 92 93 94 95 96 97 98 99 Year R 2 = 0,8156 1
List of ARV FDA Approved Nucleoside/Nucleotide Analogues Abacavir (Ziagen, ABC) Didanosine (Videx, ddi) Emtricitabine (Emtriva, FTC) Lamivudine (Epivir, 3TC) Stavudine (Zerit, d4t) Tenofovir (Viread, TDF) Zalcitabine (Hivid, ddc) Discontinued by manufacturer 12/31/06 Zidovudine (Retrovir, AZT, ZDV) Nonnucleoside Reverse Transcriptase Inhibitors Delavirdine (Rescriptor, DLV) Efavirenz (Sustiva, Stocrin, EFV) Etravirine (Intelence, TMC 125) Nevirapine (Viramune, NVP) Rilpivirine (Edurant, TMC 278) Protease Inhibitors Amprenavir (Agenerase, APV) Discontinued by manufacturer 10/07 Atazanavir (Reyataz, ATV) Darunavir (Prezista, DRV, TMC 114) Fosamprenavir (Lexiva, Telzir, FPV) Indinavir (Crixivan, IDV) Lopinavir/Ritonavir (Kaletra) Nelfinavir (Viracept, NFV) Ritonavir (Norvir, RTV) Saquinavir (Invirase, SQV) Tipranavir (Aptivus, TPV) Fusion Inhibitors Enfuvirtide (Fuzeon, ENF, T-20) Chemokine Coreceptor Antagonists Maraviroc (Selzentry, Celsentri, MVC) Integrase Inhibitors Raltegravir (Isentress, RAL) HIV Genetic Diversity HIV quasispecies HIV displays large genetic variability and two viruses can be causative agent of AIDS (HIV-1 and HIV-2). RT has no proofreading mechanisms and poses a mutations rate of 1 error per 10000 nt synthesized. Every day in a infected individual we have a huge replication burden (10 10 particles daily) and all kind mutations appears. Most of them are lost and few are fixed in the viral population. HIV-2 can differ from HIV-1 in 50% of the aa of the main genes (gag, pol, and env). HIV-2 is less pathogenic and less transmissible by horizontal and vertical routes. Why HIV get resistant to ARV? The drug does not produce or induce DR it just select pre-existing mutant viruses Low aderance to treatment. On-and-off ARV therapy. Infection with a isolate carrying DRM. The main message here is: HIV needs to replicate to accumulate mutations. The best way to prevent DR is keeping the VL undetectable during ARV treatment. WT MUT 2
In vitro selection B and C virus with 3TC. Types of HIV Resistance HIV viral load 10 11 10 10 10 9 10 8 10 7 10 6 10 5 RT C RT B 3TC M184I M184I M184VV Days in culture 7 14 21 28 35 42 49 56 63 70 77 84 91 98 0.02 0.04 0.08 0.16 0.32 0.64 1.2 2.4 4.8 9.6 19.2 38.4 76.8 3TC concentrations (µm) M184V Primary or transmitted drug resistance: Drug resistance in previously untreated persons. Primary drug resistance implies that a virus with drug resistance mutations was transmitted either directly, or through one or more intermediates, from a person with acquired drug resistance. In the first case, primary is used to describe persons who have recently been infected. In the second case, primary is used to describe persons with transmitted resistance. Types of HIV Resistance Acquired or secondary drug resistance: Drug resistance developing in a person who has received antiretroviral therapy. Acquired drug resistance results from the generation of genetic variation in the population of viruses within a person followed by the selection of drug-resistant variants during HAART therapy. Types of HIV Resistance Polymorphism: Polymorphisms are mutations occurring frequently in viruses not exposed to selective drug pressure. A nonpolymorphic mutation is one that does rarely occur in the absence of therapy. How ARV drugs work? NRTI 3
HIV-1 RT linked with RNA, DNA and primer How NRTI are activated? Nucleotide p66 p51 Active site Mechanism of action of AZT How RT becomes resistant to NRTI inhibitors? We have two distinct mechanisms: Discrimination of the NRTI Excision of the incorporated NRTI NRTI discrimination Some RT mutations augment its capacity to discriminate between the natural nucleotides and the analogs. Mutations in RT leading to NRTI discrimination NNRTI MDR Mutation 4
Other multidrug resistant mutations in RT Two or more amino acid insertion S-A, S- S or S-G at HIV-1 RT codon 69(S) in conjunction with other RT mutations are associated with phenotypic resistance to multiple NRTIs T69 Pos TAM mutations Resistance to zidovudine (ZDV) results from thymidine analogue resistance mutations (TAMs) at HIV-1 reverse transcriptase (RT) codons 41, 67, 70, 210, 215 and 219. Two mutations are possible at codon 215: Y or F. Whereas 215Y occurs alone or with 41L and 210W (TAM-1), 215F rarely occurs with these mutations or by itself; it is usually found with 67N, 70R and 219Q (TAM-2). The 210W mutation most often occurs with 41L and 215Y and rarely occurs with 215F or TAM-2 mutations. We previously demonstrated that the 215F mutant is less fit than T215 wild-type or 215Y (Hu et al., Antiviral Therapy 2004; 9:S68). In the present study, we explored the virological basis for clustering of 210W with other TAM-1 but not TAM-2 mutants, and the clustering of 215F, but not 215Y, with TAM-2 mutants. What is excision? What is pyrophosphorolisis? How NRTI excision mechanism works? For isolates carrying TAM How TAM works in excision mechanism? Nucleotide inhibitor (Tenofovir, Gilead) Tenofovir was approved by FDA in 2001. This modification enables TDF to jump the 1 st phosphorylation step making a favorable PK profile. 5
Main TDF Resistance Mutation NRTI mutation list Does K65R accumulatem ore often in subtype C? NNRTI NNRTI mechanism of action. HIV-1 RT Linked with Nevirapine (NNRTI) Active site NNRTI Nevirapine HIV-1 RT linked with Nevirapine with mutations related with NNRTI mutations Entravirine and its capability to inhibit NNRTI resistant strains specifically K103N Active sites NNRTI DR Mutations Nevirapine In Brazil The prevalence of 13 specific ETR RAMs in subtype B samples was V179T 2%, G190S 3.7%, Y181V 0,5%, V106I 6%, V179D 2.6%, K101P 3.0%, K101E 5.3%, Y181C 12%, A98G 6.9%, V90I 6.9%,Y181I 3.6%, G190A 15% and L100I 6.1%. 6
NNRTI mutation list HIV GAG Maturation process How protease inhibitors work Sampling of Minor PI HIV Protease Major Mutations Positions 30, 32, 33, 46, 48, 50, Mutations commonly 54, 76, 82, 84, 88, 90 present in non-b isolates as natural polymorphism Mutations Positions 20, 36, 63, 71, 77, 93 Protease inhibitor HIV Drug Resistance Database, Los Alamos National Laboratory http://resdb.lanl.gov/resist_db 7
New PIs Ritonavir enhances the blood levels of other protease inhibitors Atazanavir Tipranavir Darunavir (mg/ml) 10 1 Without ritonavir Saquinavir Indinavir Amprenavir Nelfinavir (mg/ml) 10 1 With ritonavir.1.1 DRV interacts with more aa in protease active site.01 0 1 2 3 4 5 6 7 8 Hours.01 0 1 2 3 4 5 6 7 8 Hours Kempf, et al, 1997 Genetic Barrier How a MDR protease looks like NRTI PI RTV/PI Genotipic Res PI mutation list New classes of ARV drugs 8
Integrase inhibitors Mutations N155H, alone and combinations with Q148K/H/R and Y143R/C/H Fuseon T20 Maraviroc Final Remarks The best way to prevent the spread of HIV DR is to prevent HIV infection. The best other way to prevent the spread of HIV DR is to keep the patients in ARV with undetectable VL. In RLS the VL is not available in large scale. 2nd line potent regimens are not available in RLS. We need to make an effort to implement VL and make available potent 2nd line regimens to curb the spread of HIV DR. 9