Antibodies attenuate the capacity of dendritic cells to stimulate HIV-specific cytotoxic T lymphocytes

Background: Control of HIV is suggested to depend on potent effector functions of the virus-specific CD8(+) T-cell response. Antigen opsonization can modulate the capture of antigen, its presentation, and the priming of specific CD8(+) T-cell responses. Objective: We have previously shown that opsonization of retroviruses acts as anendogenous adjuvant for dendritic cell (DC)mediated induction of specific cytotoxic T lymphocytes (CTLs). However, in some HIV-positive subjects, high levels of antibodies and low levels of complement fragments coat the HIV surface. Methods: Therefore we analyzed the effect of IgGopsonization on the antigen-presenting capacity of DCs by using CD8(+) T-cell proliferation assays after repeated prime boosting, by measuring the antiviral activity againstHIV-infected autologous CD4(+) T cells, and by determining IFN-gsecretion from HIV-specific CTL clones. Results: We find that DCs exposed to IgG-opsonized HIV significantly decreased the HIV-specific CD8(+) T-cell response compared with the earlier described efficient CD8(+) T-cell activation induced by DCs loaded with complement-opsonized HIV. DCs exposed to HIV bearing high surface IgG levels after incubation in plasma from HIV-infected subjects acted as weak stimulators for HIV-specific CTL clones. In contrast, HIV opsonized with plasma from patients exhibiting high complement and low IgG deposition on the viral surface favored significantly higher activation of HIV-specific CD8(+) T-cell clones. Conclusion: Our ex vivo and in vitro observations provide the first evidence that IgG opsonization of HIV is associated with a decreased CTL-stimulatory capacity of DCs. (J Allergy Clin Immunol 2012;130:1368-74.)