Secretory Leukocyte Protease Inhibitor Binds to Annexin II, a Cofactor for Macrophage HIV-1 Infection

Ma, Ge; Greenwell-Wild, Teresa; Lei, Kejian; Jin, Wenwen; Swisher, Jennifer; Hardegen, Neil; Wild, Carl T.; Wahl, Sharon M.

Annexin II Is a Cofactor for HIV Infection. Based on the link between SLPI, a known antagonist of HIV-1 infection (2, 3) , and annexin II, we attempted to abort infection by directly blocking annexin II. A single treatment of adherent macrophages with an antibody targeting the NH 2 -terminal tail of annexin II (Fig. 4, A and B) , but not the carboxy terminus (not depicted) nor an IgG isotype control (Fig. 4 B) , during the initial infection process resulted in significant (Ͼ90%) and durable (Ͼ14 d) suppression of R5 HIV-1 BaL infection. Infection was monitored by HIV-1 p24 antigen levels (Fig. 4) and by ultrastructural evidence of viral replication (not depicted). Furthermore, decreased expression of annexin II using RNA-mediated interference (RNAi; Fig. 4 C, inset) dramatically suppressed macrophage viral infection (Fig. 4 C) . Although suppression of annexin II protein by RNAi was not absolute, likely related to inability to transfect all cells and/or due to stability of intracellular annexin II, the reduced levels of annexin II were sufficient to interrupt the HIV-1 infection process, with the implication that there might be a threshold level of annexin II necessary for optimal infection. Furthermore, to establish that the suppression of viral infection was specific to annexin II levels, we monitored the macrophages treated with annexin II RNAi for CD4 and CCR5 expression in parallel. As evident by Western analysis (Fig. 4 D) and by flow cytometry (not depicted), no substantive change in these essential viral recognition and binding receptors was evident, consistent with a contributing role for annexin II in the macrophage infection process.