[14] REVERSION KINETICS OF A LIVE ATTENUATED SIV CAN BE IMPAIRED BY THE M184V MUTATION IN THE SIV RT

1st International AIDS Society Conference on HIV Pathogenesis and Treatment

Buenos Aires, Argentina - July 8-11, 2001

[TITLE:] REVERSION KINETICS OF A LIVE ATTENUATED SIV CAN BE IMPAIRED BY THE M184V MUTATION IN THE SIV RT

[AUTHOR(S):] Whitney J
Mcgill AIDS Centre, Montreal, Quebec, Canada

IAS Conf HIV Pathog Treat 2001 Jul 8-11;1st: Abstract No. 14

[ABSTRACT:] Background: The development of an effective HIV vaccine has presented a considerable challenge. Towards this end a significant number of SIV based models have already been developed, most employing deletion of viral accessory genes. In contrast to these approaches our lab has developed a set of novel attenuated SIV mac candidates containing deletions within the 5 region of the leader sequence. These constructs displayed marked attenuation in cell lines and monkey PBMCs.

Methods: An inherent problem of a live attenuated approach is viral reversion accompanied by increased fitness. Over extended passage several deletion constructs exhibited increased replicative capacity in conjunction with the appearance of compensatory mutations. Therefore, in the context of vaccine development, we sought to determine the utility of the M184V in delaying viral reversion. Methods: We have already constructed a series of mutants containing deletions within a 97nt leader sequence downstream of the PBS. Those displaying moderate reversion kinetics (SD2+398-418, SD5+380-397, SD6 +371-379) were selected as candidates for the insertion of the M184V substitution. Replication capacities and reversion characteristics were determined in CEMx174 cells by RT assay. Specific mutations were determined by cloning and sequencing.

Results: The reversion of several SIV mutants can be further delayed by the addition of the M184V mutation. Serial passage two mutants (SD5-M184V, SD6-M184V) eventually resulted in loss of the M184V mutation with a commensurate increase in reversion rates. Interestingly, one mutant in particular, SD2-M184V retained the M184V mutation and also exhibits a different mutational outcome compared to SD2 controls

Conclusions: Sequences downstream of the PBS, near SL1 in conjunction with the M184V mutation can diminish viral fitness, delay reversion kinetics and affect the mutational outcome. Sequences downstream of the PBS, near SL1 in conjunction with the M184V mutation can diminish viral fitness, delay reversion kinetics and affect the mutational outcome.

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