Preserved MHC Class II Antigen Processing in Monocytes from HIV-Infected Individuals

Background: MHC-II restricted CD4+ T cells are dependent on antigen presenting cells (APC) for their activation. APC dysfunction in HIV-infected individuals could accelerate or exacerbate CD4+ T cell dysfunction and may contribute to increased levels of immunodeficiency seen in some patients regardless of their CD4+ T cell numbers. Here we test the hypothesis that APC from HIV-infected individuals have diminished antigen processing and presentation capacity. Methodology/Principal Findings: Monocytes (MN) were purified by immuno-magnetic bead isolation techniques from HLA-DR1.01+ or DR15.01+ HIV-infected and uninfected individuals. MN were analyzed for surface MHC-II expression and for antigen processing and presentation capacity after overnight incubation with soluble antigen or peptide and HLA-DR matched T cell hybridomas. Surface expression of HLA-DR was 20 % reduced (p,0.03) on MN from HIV-infected individuals. In spite of this, there was no significant difference in antigen processing and presentation by MN from 14 HIV-infected donors (8 HLA-DR1.01+ and 6 HLA-DR15.01+) compared to 24 HIV-uninfected HLA-matched subjects. Conclusions/Significance: We demonstrated that MHC class II antigen processing and presentation is preserved in MN from HIV-infected individuals. This further supports the concept that this aspect of APC function does not further contribute t

Antigen presentation by HLA-DR1+ MN from individual HIV-infected and uninfected subjects.

<p>In all four panels, MN (5×10⁴/well) were incubated with soluble antigen or peptide and T cell hybridoma (1×10⁵/well) for 24 hrs. Viremic HIV-infected individuals with VL>1000 are High VL and VL<1000 are Low VL. A. Control MN and soluble RT, B. HIV+ MN and soluble RT, C. Combined data on soluble RT presentation, D. Control MN and peptide, E. HIV+ MN and peptide, F. Combined data on peptide presentation.</p

Relationship between HLA-DR level and antigen presentation.

<p>Data from all 38 subjects in the study were normalized. The individual's ratio of presentation was calculated by dividing their IL-2 level for the middle concentration of RT, HEL or peptide by the mean IL-2 level from the control subjects at the same middle concentration of antigen or peptide. Open red diamonds are data from HIV-infected individuals and closed black diamonds for uninfected controls.</p

Characterization of T cell hybridoma clone 15HEL.

<p>MN (5×10⁴/well) were incubated with antigen (intact HEL for A and C, HEL peptides for B) and 15HEL (1×10⁵/well) for 24 hrs. Supernatants were harvested, and IL-2 measured by ELISA. A. Effect of anti-HLA-DR or isotype on response. B. Identification of HEL peptide epitope recognized by 15HEL. C. Effect of anti-CD80 and CD86 antibodies together (5 µg/ml of each) or isotype control (10 µg/ml) on responses. Results of A and C represent triplicate wells and error bars SEM.</p

Antigen presentation by HLA-DR15+ MN from individual HIV-infected and uninfected subjects.

<p>MN (5×10⁴/well) were incubated with soluble HEL or peptide and T cell hybridoma (1×10⁵/well) for 24 hrs. Viremic HIV-infected individuals with VL>1000 are High VL and VL<1000 are Low VL. A. Control MN and soluble HEL, B. HIV+ MN and soluble HEL, C. Combined data on soluble HEL presentation, D. Control MN and peptide, E. HIV+ MN and peptide, F. Combined data on peptide presentation.</p