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Intersubtype differences in the effect of a rare p24 Gag mutation on viral replicative fitness

Intersubtype differences in the effect of a rare p24 Gag mutation on viral replicative fitness. Denis Chopera. Background.

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Intersubtype differences in the effect of a rare p24 Gag mutation on viral replicative fitness

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  1. Intersubtype differences in the effect of a rare p24 Gag mutation on viral replicative fitness Denis Chopera

  2. Background • Certain immune-driven mutations that occur in conserved regions of the HIV-1proteome often affect viral replication [Brockman et. al., 2010; Crawford et. al., 2007; Miura et. al., 2009] • Rare mutations occurring in p24 Gag were identified in elite controllers in subtype B infections and these have a severe fitness cost to viral replication [Miura et. al., 2009] • The extent to which these mutations affect viral fitness in other HIV-1 subtypes has not been explored.

  3. Study Objectives • This study examined the impact of a rare Gag mutation, M250I, on subtype B and C viral replicative fitness • Rationale: -M250I is one of the mutations identified in elite controllers in subtype B [Miura et. al., 2009] -The mutation is negatively associated with a common HLA-B*57 escape mutation, T242N [Martinez- Picadoet. al., 2006; Choperaet. al., 2011]

  4. Distribution of M250I by cohort and HLA in subtype B -M250I associated with HLA-B58 supertype and is enriched in elite controllers in subtype B infections

  5. M250I and subtype B replication -M250I impairs viral replication in vitro

  6. Distribution of M250I by cohort in subtype C -M250I more common in subtype C viruses

  7. Subtype C replication capacity -Impairs viral replication in site-directed mutants but not in patient-derived isolates

  8. Why is the M250I mutation more common in subtype C infections and why is it not associated with a fitness cost in plasma-derived viruses????? • Secondary mutations have been shown to fully or partially restore viral fitness incurred by CTL escape mutations [Brockman et. al., 2007; Crawford et. al., 2007; Schneidewind et. al., 2007] • We applied phylogentically-corrected methods to detect amino acids that co-vary with the M250I mutation

  9. Covariation between codon 250 and other Gag sites in the chronic subtype C cohort

  10. M250I compensation in subtype C and B viruses -There is compensation of M250I mutation in subtype C but not subtype B viruses

  11. Effect of M250I mutation on p24 helix-6 -M250I destabilizes capsid helix 6 in subtype B viruses

  12. Summary • In subtype B infections, the M250I mutation is very rare and enriched in elite controllers expressing HLA-B58 supertype • The mutation is associated with a reduction in viral replication in subtype B viruses • M250I is not associated with a fitness cost in patient-derived (subtype C) isolates • In subtype C, the associated mutations, S252G and D260E partially restore viral replication • M250I destabilizes helix 6 of the capsid and this effect is more pronounced in subtype B

  13. Conclusion • Understanding the selection mechanism for the M250I mutation may be useful for HIV vaccine immunogen design • Vaccine designing strategies need to take into consideration the inter-subtype differences in the specific mutations selected by under immune pressure and their relative impact on viral fitness

  14. Acknowledgements Dr. Carolyn Williamson Dr. Clive Gray Dr. Zenda Woodman Dr. Darren Martin Dr. NobubeloNgandu Dr. Roman Ntale Dr. ZabrinaBrumme Dr. Mark Brockman Eric Martin Laura Cotton Dr. Jonathan Carlson Dr. Bruce Walker Dr. Toshiyuki Miura Dr. FlorenciaPereyra Dr. ThumbiNdung’u Dr. Jaclyn Mann (Wright) Dr. SalimAbdool-Karim Dr. KolekaMlisana CAPRISA 002 Study Team Dr. Richard Harrigan

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