9TH EUROPEAN AIDS CONFERENCE (EACS) 1st EACS RESISTANCE & PHARMACOLOGY WORKSHOP October 25 - 29, 2003 Warsaw, Poland

Background of Study: As drug resistant HIV is less fit than wild type in vitro, individuals infected with such virus may have different disease progression.

Objectives: To compare the CD4 profiles following seroconversion of ART-naïve individuals with and without transmitted drug resistance (TDR).

Methods: CD4 following seroconversion was modelled in the UK Register of HIV Seroconverters using a piecewise-linear mixed model, allowing the rate of decline to change after one year, and censoring follow-up at ART initiation. We considered effects of TDR (³1 key mutations detected in a genotypic resistance test performed within 18 months of negative HIV test), adjusting for age at seroconversion, exposure category, and presentation during acute infection.

Results: 1521 individuals were included, of whom 122 (seroconverting between 1995-2002) were genotyped close to seroconversion. The 21 (17%) with TDR appeared to have initially higher CD4 counts but a steeper decline in the first year (p=0.08). Thereafter we found no evidence of a difference in the rate of CD4 decline (p=0.54) between those with and without TDR. Estimated rates were 0.81 (95% CI -0.68-2.30) and 1.31 (0.67-1.97) √CD4 per year for TDR and no TDR respectively. For an individual at a CD4 count of 500 cells/mm³, these rates correspond to an annual CD4 loss of 36 and 57 cells/mm³ respectively.

Conclusions: We found no evidence of a difference in the rate of CD4 decline between those with and without TDR after the first year following seroconversion. Longer follow-up is required and the possible differences in the first year after seroconversion should be investigated further.

Presenting Author: Krishnan Bhaskaran, MRC Clinical Trials Unit, 222 Euston Road, NW1 2DN, London, United Kingdom, Phone: 02076704730

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