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HIV Drug Resistance is Inevitable

HIV Drug Resistance is Inevitable. HIV DR is an inevitable consequence of ART, influenced by: Removal of barriers to access to care Availability/continuity of drug supply Ability of regimens to suppress replication completely Adherence and tolerability of regimens

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HIV Drug Resistance is Inevitable

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  1. HIV Drug Resistance is Inevitable • HIV DR is an inevitable consequence of ART, influenced by: • Removal of barriers to access to care • Availability/continuity of drug supply • Ability of regimens to suppress replication completely • Adherence and tolerability of regimens • "Genetic barrier" to resistance • Relative fitness of resistant variant(s) • Pharmacokinetics (IQ) • Therefore, efforts to prevent HIVDR should be focused on these factors

  2. HIV DR Testing in Resource Rich Settings Prevalence of HIVDR at baseline Prevalence of HIVDR at baseline Resistance developing on therapy Resistance developing on therapy Utility of resistance testing before initiating therapy Resistance testing before switching therapy (SOC) Individualization of 1st line regimen Individualization of 2nd line and subsequent regimens 24+ drugs from 6 classes

  3. HIV DR Testing in Resource Poor Settings Prevalence of HIVDR at baseline Prevalence of HIVDR at baseline Resistance developing on therapy Resistance developing on therapy Will standard 1st line regimens be effective? Prevalence and patterns of resistance in population Determination of standard 1st line regimen Determination of standard 2nd line regimens ~6 drugs from 3 classes

  4. HIVDR Early Warning Indicators (EWI) Proportion lost to follow-up during the first 12 months of ART Prescribing practices Patient retention on first-line ART Site-level ART Program Function Drug supply continuity On-time ARV drug pick up ART appointment-keeping Viral load suppression @12 months Pill count/ adherence

  5. Percentage of genotyped first-line HAART failures with NNRTI, M184V, TAMS and PI resistanceGenotypes analysis 6 Gupta et al CROI 2008

  6. VIRAL EVOLUTION in NON-B SUBTYPES of HIV-1

  7. URF 4.2% A 12% AE 3.1% AG 6.7% G 5% B 10% D3.6% Global distribution of HIV-1 subtypes 2 million 1.3 million 4.8 million

  8. Do Differences Exist among HIV Subtypes in the Development of Drug Resistance?

  9. HIV-1 RT Subtype B Subtype C Wild type codon at position 106 V(GTA) V(GTG) Silent Mutation at Codon 106 responsible for the V106M mutation in clade CRT with NNRTIs In clade C, V106M arises two codon changes M(ATG) In clade B, V106A occurs A(GCA) two codon changes

  10. Marconi et al showed that V106M is the second most common NNRTI mutation after K103N in subtype C patients. In contrast, V106A/M is very rarely seen with subtype B isolates. Clinical Infectious Diseases 15:1589, 2008

  11. Rapid Selection of K65R Resistance in Subtype C Isolates

  12. History of 23 Botswana Patients Treated with ddI/d4T plus 3TC or NVP No. Patients 23 No. Patients failing 15 No. Patients with K65R 7 No. Patients with L74V 0

  13. Hosseinipour MC, van Oosterhout JJ, Weigel R, Phiri S, Kamwendo D, Parkin N, Fiscus SA, Nelson JA, Eron JJ, Kumwenda J. The public health approach to identify antiretroviral therapy failure: high-level nucleoside reverse transcriptase inhibitor resistance among Malawians failing first-line antiretroviral therapy. AIDS. 2009. 1;23(9):1127-34

  14. Background The Malawi ART program scale-up: >150,000 patients started on d4T/3TC/NVP A substantial minority with have virologic failure and eventually clinical failure. In failing patients resistance will be present Few data from Africa on resistance patterns

  15. Characteristics of 101 Patients that Initiated Second-Line ART in Malawi d4T/3TC/NVP failures based on clinical/immunological criteria, confirmed by HIV-RNA >400 Hosseinipour et al. AIDS 23(9):1127-34 2009

  16. CONFIRMATION • Similar findings have now been obtained in Capetown,South Africa by C. Orrell et al working with subtype C infected populations • In India, it now appears as though K65R will also be an important mutation among first-line treatment failures who received d4T/3TC/NVP

  17. Rationale Does the nucleotide sequence trigger an increased probability of the development of the K65R resistance mutation in subtypeC ? Biochemical analysis of the syntheses of (-)strand DNA from viral RNA and (+)strand DNA from viral (-)strand DNA by the RTs of subtypes B and C.

  18. (+)strand DNA synthesis (1) Only the subtype C sequence triggers a pausing site that increases the probability of a nucleotide misincorporation event which in turn leads to the K65R mutation.

  19. (+)strand DNA synthesis (2) The pausing patterns are driven by the nucleotide templates and are independent of the RT enzymes used (subtype B vs C).

  20. Validation in cell culture What is the propensity of different recombinant viruses to develop the K65R resistance mutation under N(t)RTI treatment ? 64 65 66 5‘-... AAG AAA AAA ...-3‘ NL4-3 (wt) 5‘-... AAA AAA AAA ...-3‘ NL4-3 (K64K) 5‘-... AAG AAG AAA ...-3‘ NL4-3 (K65K) 5‘-... AAA AAG AAA ...-3‘ NL4-3 (K64K/K65K) G K65R Infections of MT-2 cells and CBMCs with these viruses followed by treatment with different N(t)RTIs (single drugs or in combination).

  21. Selections in CBMCs The double mutant NL4-3 (64/65) acquires K65R more rapidly in CBMCs than wild-type NL4-3.

  22. Mutations in MT-2 Cells after 10 Weeks

  23. Conclusion K65R will be a more important mutation in subtype C than subtype B viruses. This may affect both prevention research strategies as well as treatment options over time in areas in which subtype C viruses are predominant

  24. Sexual Transmission of Drug Resistance Mutations • Approximately 5-10% of all new HIV infections in developed countries now include at least one drug-resistance related mutation. • Transmitted drug resistance is now increasingly being reported in developing countries. • No information is yet available on whether K65R may be sexually transmitted.

  25. CONCLUSION • HIV genotyping should be performed on all patients prior to prescription of ARVs • HIV genotyping should be performed on all patients prior to switching to a second-line regimen. • The above considerations are not yet practical in terms of being implemented in many developing country settings.

  26. REMERCIEMENTS • Dimitrios Coutsinos • Cedric Invernizzi • Maureen Oliveira • Daniela Moisi • Bluma Brenner

  27. MERCI BEAUCOUP

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