Viral escape and outcome of infection linked to SIV Gag KP9-specific CD8 T cells at transmission

1. Viral escape and outcome of infection linked to SIV Gag KP9-specific CD8 T cells at transmission Caroline Fernandez Department of Microbiology and ImmunologyUniversity of Melbourne Australia

2. SIV/ SHIV infection of pigtail macaques (Macaca nemestrina) as a model for HIV/AIDS Studied DNA and poxvirus vaccinations as a means of inducing T cell responses (C.J. Dale et al JVI 2004) Common and immunodominant SIV Gag CD8+ T cell response KP9164-172(M. Smith et al JVI 2005) KP9 epitope presented by MHC Class I Mane-A*10 allele(M. Smith et al JVI 2005) T cell escape occurs at KP9 in Mane-A*10 positive animals(C. Fernandez, I. Stratov et al JVI 2005) Tetramer of Mane-A*10 to quantify KP9-specific CD8+ T cell response(M. Smith et al J Med Prim 2005)

3. K K F G A E V V P . R . . . . . . . . . . . . . . . . SIVmac239 Escape mutant virus SHIVmn229 91% (40/44) (4/44) Reversion of T cell escape mutant strain in Mane-A*10 negative animals • T cell escape mutants may revert to wild-type sequence when passaged to a new host unable to respond to that epitope (Friedrich et al, Leslie et al, Nat Med 2004) • We found a challenge stock (SHIVmn229), previously passaged in pigtail macaques with Mane-A*10 that had escaped at the KP9 epitope

4. 100 90 80 Rate of reversion (over 14 days) suggests high fitness cost of escape mutation in the absence of immune pressure 70 60 % WT KP9 sequence 50 40 1.7105 30 Mane-A*10 -ve 4194 H20 20 H21 10 0 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36- 46 Weeks post SHIV challenge mn229 Rapid reversion of escape mutant strain in Mane-A*10 negative animals

5. What happens when DNA/FPV vaccinated Mane-A*10 positive animals are given the escape mutant virus

6. Mane-A*10 + Retention of escape mutantat late time points….

7. What happens during acute infection?

8. 100 80 4386 60 Mane-A*10 + 4241 % WT sequence at KP9 4299 40 20 0 0 1 2 3 4 5 6 Weeks post SHIV challenge mn229 High levels of reversion then re-escape in some animals

9. 4277 4382 4295 % WT sequence at KP9 Mane-A*10 + Low levels of reversion in other animals

10. % WT sequence at KP9 Mane-A*10 + Variable degrees of early transient reversion then re-escape. Why?

11. Do vaccine induced KP9-specific T cells at transmission impact on reversion to wild-type - measured KP9-specific T cells by MHC Class I tetramer

12. 100 90 r = -0.77 80 70 p = 0.001 60 % WT KP9 at Day 10 post challenge 50 40 30 20 10 0 0.00 0.10 0.20 0.30 0.40 % KP9-specific CD8 T cells at transmission Vaccine-induced T cell immunity at transmission linked to subsequent reversion to wild-type virus

13. 100 90 r = -0.65 80 70 p = 0.02 60 % WT KP9 at Day 14 post challenge 50 40 30 20 10 0 0.00 0.20 0.40 0.60 0.80 % KP9-specific CD8 T cells at transmission T cell immunity linked to reversion to wild-type- confirmed in second vaccine study

14. Does reversion to wild-type impact viral load- wild-type virus fitter, but ….- wild-type virus can be eliminated by CTL

15. r = -0.45 P = 0.03 Reversion to wild-type linked to earlier peak in viral load- wild-type virus fitter

16. r = -0.46 P = 0.03 But reversion to wild-type reduces viral load!- elimination of wild-type virus highly advantageous

17. Conclusions KP9-specific T cells at transmission limit the degree of reversion to wild-type virus during acute infection Reversion to wild-type correlates with earlier peak in viral load But early reversion linked to lower set point viral load, probably reflecting CTL killing of wild-type cells CTL killing more beneficial to host than fitness cost of escape - reduced viral load in animals with more reversion to wild-type virus Perhaps inducing a strong immunodominant T cell response may not be useful upon exposure to escape mutant virus

18. Acknowledgements University of Melbourne: Stephen Kent Miranda Smith Jane Batten Rob De Rose Jeanette Reece Erik Rollman Sheilajen Alcantara Jie Lin Andrew Brooks University of NSW: Miles Davenport Vanessa Venturi