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Detection of p24 erythrocyte associated antigen in HIV positive patients with previous undetectable plasma viral load
Presented by María Sol dos Ramos Farías, Argentina.
dos Ramos Farías M.S.1, Garcia M.N.1, Schvachsa N.1, Rabinovich R.D.1, Ávila M.M.1
1National Reference Center for AIDS, Department of Microbiology, School of Medicine, University of Buenos Aires, Buenos Aires, Argentina
Objectives: Although detection of HIV-1 RNA is the “gold standard” marker for monitoring disease in patients under HAART, it remains unaffordable in poor settings and restricted to a low number of determinations. The present study is focused on the possibility to use detection of p24 antigen associated to erythrocytes (p24-E) in patients with consecutive undetectable viral load under HAART in order to reduce follow-up costs.
Methods: 41 patients with undetectable viral load in plasma (pVL<50copies/ml) -for at least three determinations prior to the study- were recruited. pVL was also determined at the moment of the study. Erythrocytes were obtained by Dextran sedimentation, later treated with Glicine-ClH pH=3.2 and centrifuged in order to separate viral antigens. The supernatant was used for p24 antigen quantitation. Plasma p24 antigen was also quantified.
Results: Eight out of 41 patients showed detectable pVL (range: 67-3966 copies/ml, median: 112 copies/ml). These eight patients also presented p24-E (median: 26.55 pg/ml, range: <22 to >152pg/ml). In 5 out of the 33 patients with undetectable pVL, p24-E was also detected (median: 38.26pg/ml, range: 30 to >152 pg/ml). By comparing both groups (undetectable and detectable pVL) regarding the presence or absence of p24-E, a significant relationship between detectable pVL and the presence of p24 antigen was found in erythrocytes (Fisher exact test p=0,0000135).
Conclusions: Every patient with a first detectable pVL after a period of pVL<50copies/ml presented p24-E. On the contrary no one with undetected p24-E has pVL<50copies/ml. These results suggest the possibility to follow-up this kind of patients through p24-E and to assess pVL only when this antigen is present in that fraction. Thus, monitoring costs would be dramatically reduced. A follow up study in patients with and without p24-E would allow us to evaluate whether these patients differ in the evolution of the infection.
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