HIV-Infected Lymphocytes Regulate Fibronectin Synthesis by TGFβ1 Secretion

Abstract

Alterations in lymph node architecture occur with HIV infection and contribute to immunological derangements. We previously showed that matrix fibronectin stabilized HIV and increased HIV infection of PBL. We showed increased fibronectin deposition in lymph nodes of HIV-infected patients. However, we did not detect a difference in fibronectin synthesis between uninfected and infected PBL. Therefore, we hypothesized that interactions of HIV-infected cells with fibroblasts resulted in increased fibronectin deposition. We detected increased fibronectin deposition by immunofluorescence on fibroblasts cocultured with HIV-infected PBL. We also found a 6-fold increase in fibronectin mRNA levels in fibroblasts cocultured with HIV-infected PBL by real-time PCR. Furthermore, when HIV-infected PBL were added to reporter fibroblasts stably transfected with a fibronectin promoter, we found a 1.5- to 2-fold increase in promoter activity. Since conditioned medium from HIV-infected PBL also increased fibronectin promoter activity, we hypothesized that a soluble factor such as TGFβ was responsible for increased fibronectin secretion. Pretreatment of supernatant from HIV-infected PBL with a neutralizing Ab to TGFβ1 abrogated the increased fibronectin promoter activity. We confirmed that HIV-infected PBL produced increased TGFβ1 by ELISA. Using Mv1Lu reporter cells, we found a 2- to 3-fold increase in biologically active TGFβ in supernatants of HIV-infected PBL. Finally, we determined that HIV infection did not change the percentage of active TGFβ. Our data suggest that HIV-infected lymphocytes indirectly contribute to lymph node remodeling by secretion of TGFβ1, which increases fibronectin synthesis by fibroblasts.