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Defining CD4 specific immune response in seroconverters enrolled in an RCT of primary HIV infection
Presented by Rodney Phillips, United Kingdom.
Phillips R.1, Lee K.2, Robinson N.1, Brown H.1, Ohm Laursen L.1, Fidler S.3, Scriba T.1, Oxenius A.1, Porter K.2, Weber J.3, SPARTAC Trial Investigators
1University of Oxford, The Peter Medawar Building for Pathogen Research, Oxford, United Kingdom, 2MRC Clinical Trials Unit, London, United Kingdom, 3Imperial College, London, United Kingdom
Objectives: To define CD4+ T cell response within the context of an RCT in primary HIV infection (PHI), describe the proportion with such a response at baseline and over time, and examine the association between response and baseline CD4 count and HIV RNA.
Methods: Data from the SPARTAC trial of participants randomised to receive 12 weeks, 48 weeks of HAART or no therapy at PHI, combining all 3 arms, were used to estimate the proportion with positive response to gag p24, using ELISPOT assays, at randomisation and scheduled visits to week 108. The impact of a number of definitions on proportion positive was assessed. Using linear regression we examined the relationship between magnitude of response and CD4 count and HIV RNA (using mean count at screening and randomisation), adjusting for age and sex.
Results: Of 127 participants seroconverting 2003-2006 in whom data were available, 73 (65%) demonstrated a positive response at baseline using a definition of ³3 times SD of baculovirus background and ignoring background >50 SFCs/106 CD8-depleted peripheral blood lymphocytes. Median (IQR) response was 40 SFCs (14-102) and median CD4 and HIV RNA were 538 cells/ml and 73741 copies/ml. The proportion with positive response remained stable at 66%, 65%, 69%, 73% and 67% at weeks 12, 24, 48, 60 and 108 respectively. This proportion varied, however, from 38% to 81% at baseline depending on whether definition used was based on magnitude of difference from, or variability of, background measurements. We found no evidence of an association between magnitude of response and either CD4 (p=0.58) or viral load (p=0.52) at baseline.
Conclusions: The blinded data demonstrate a preservation of measurable HIV-specific CD4+ T cell responses over time. There was no correlation between the magnitude of HIVp24 -specific CD4+ T cell IFNg production and baseline CD4+ T cell count or plasma viral load.
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