The HBV surface proteins envelop nucleocapsids to form virions. In addition, noninfectious spherical and filamentous subviral particles, denoted HBsAg, are secreted and can exceed the HBV virion level by at least 1,000-fold. HIV has been shown to infect multiple cells in the liver, including selleck Imatinib Mesylate hepatocytes (reviewed in reference 3). HIV DNA has been detected by PCR and HIV RNA detected by in situ hybridization in hepatocytes and Kupffer cells, and HIV capsid antigen (p24) has been detected in Kupffer cells by immunohistochemistry in liver specimens from HIV-infected individuals (7). HIV RNA has also been detected in Kupffer cells, sinusoidal cells, and portal mononuclear inflammatory cells, in addition to hepatocytes (7).

In vitro studies of HIV infection of liver cells support the in vivo findings using primary human Kupffer cells, primary endothelial cells, and a number of hepatic cell lines (derived from hepatoma and hepatoblastoma cells) (8). Few studies have examined the interaction between HIV and HBV in vitro. We hypothesized that HIV infection of hepatocytes has a direct effect on the HBV viral life cycle. To examine this, we developed an in vitro model to assess the interaction of HIV and HBV in hepatic cell lines and found that HIV coinfection of an HBV-expressing hepatic cell line led to an increase in intracellular HBsAg. Given that intracellular HBsAg can facilitate hepatocyte toxicity, this interaction may potentially explain enhanced liver disease progression in HIV-HBV coinfection. MATERIALS AND METHODS Cell lines.

The human hepatic cell lines expressing HBV antigens (Hep3B cells, which express HBsAg, and AD38 cells, which express proteins, RNA, and DNA intermediates characteristic of HBV replication [including HBsAg, HBcAg, and HBV DNA, although HBeAg production is reduced] [18]) or not expressing HBV (Huh7, HepG2, and AD43 cells) were cultured at 37��C in minimal essential media (MEM) or Dulbecco’s modified Eagle medium (DMEM) (Gibco, Invitrogen, Grand Island, NY). The medium was supplemented with 10% heat-inactivated fetal calf serum (Progen, Darra, Australia), 100 U/ml penicillin G, 100 U/ml streptomycin, and l-glutamine (Gibco, Invitrogen). AD38 and AD43 cells were grown in DMEM with nutrient mixture F-12 (DMEM/F-12) with 400 ��g/ml G418 (Geneticin; Gibco-BRL) and 2 ��g/ml tetracycline (Sigma, St. Louis, MO).

TZM-bl cells (a HeLa-derived indicator cell line which express Dacomitinib surface CD4, CXCR4, CCR5, and the ��-galactosidase and luciferase genes under the control of the HIV-1 promoter) were obtained through the NIH AIDS Research and Reference Reagent Program (Division of AIDS, NIAID, NIH) (provided by John C. Kappes, Xiaoyun Wu, and Tranzyme Inc.). TZM-bl cells, a nonhepatic cell line, were used as a positive control for HIV replication.