CD4-Independent Infection of Human B Cells with HIV Type 1: Detection of Unintegrated Viral DNA

Abstract

Although B lymphocytes are a major constituent of lymphoid organs and acquire a significantly altered phenotype and function in HIV-infected individuals, it remains unclear whether CD4-negative B cells are a susceptible host for viral entry and long-term productive infection. We screened a number of Epstein-Barr virus (EBV)-positive and-negative Burkitt's lymphoma (BL) B cell lines as well as subpopulations of normal B cells that include tonsillar naive and germinal center/memory B cells for the expression of HIV-1 receptors CD4, CXCR4, and CCR5. Cell lines and resting or activated normal B cells lacked CD4 and CCR5 but expressed CXCR4. We demonstrate HIV-1 infection of a CD4-negative, EBV-negative (BL) cell line, CA46, which remained productively infected yet noncytopathic for more than 36 months in culture. HIV-1 (HTLV-III(B)) infection of CA46 cells was mediated through CXCR4 in a CD4-independent manner and correlated with upregulation of the expression of B cell activation markers CD23 and CD95 (Fas receptor). Despite Fas receptor expression, HIV-1-infected CA46 cells remained resistant to Fas-mediated cell death. CA46-derived, CD4-independent viral isolates were proficient in infecting and causing syncytium formation in Molt4 T cells. The HIV-1 genomic organization in persistently infected CA46 clones was found to be predominantly unintegrated linear and circular DNA. Importantly, naive and germinal center/memory B cells could also be infected by HIV-1 in a CD4-independent manner. Although these B cell subpopulations expressed moderate to high levels of CXCR4, they required activation through CD40 and interleukin 4 receptor for infection. These findings point to B cells as an additional HIV-1 target and suggest a structural evolution of the HIV-1 genome responsible for CD4-independent and noncytopathic infections.

Productive Human Immunodeficiency Virus Type 1 Infection in Peripheral Blood Predominantly Takes Place in CD4/CD8 Double-Negative T Lymphocytes

“…Although dendritic cells (35), natural killer cells (68), and B cells (14,45) have also been reported to harbor infectious provirus, T-helper lymphocytes play a pivotal role as sites of both HIV-1 production and viral persistence in PBMC. Resting memory CD4 ϩ T cells, the predominantly infected cellular subset (5), represent the major latent reservoir harboring replication-competent provirus (13,17,73), whereas activated CD4 ϩ T cells are the main targets for HIV-1 infection and show enhanced levels of viral gene expression in lymph nodes (77).…”

Discovery of Small-Molecule Human Immunodeficiency Virus Type 1 Entry Inhibitors That Target the gp120-Binding Domain of CD4

“…It is possible that NSC 13778 binds to positively charged domains of gp120, such as the V3 loop, a critical determinant of chemokine receptor specificity, and thus inhibits the interaction of gp120 and coreceptor. However, the inhibition of V3 loop-chemokine receptor interaction does not seem to be a primary mode of viral entry inhibition by NSC 13778, which did not block entry of wild-type HIV into CD4 Ϫ cells (20).…”

“…In order to ascertain whether NSC 13778 blocked HIV-1 cell entry by binding to Env domain(s) critical for viral attachment or fusion process or by masking CD4, we opted to compare its antiviral activity in CD4 ϩ versus CD4 Ϫ cells in parallel, with both infected with the same unmodified wild-type HIV-1. Some CD4-negative human B cells have previously been shown to be susceptible to HIV-1 entry via CXCR4 (20). Of various B-cell lines screened for in vitro susceptibility, we selected a Burkitt's lymphoma cell line, Akata (61,68), which lacked detectable cell surface CD4 expression, as determined by flow cytometry (data not shown).…”

“…Various B-cell lines have been reported to be susceptible to CD4-independent HIV-1 entry via chemokine receptor CXCR4 in vitro (20). Of various B-cell lines screened, CD4-negative Akata cells (EBVϩ), a Burkitt's lymphoma cell line (61, 68) (kindly provided by K. Takada), were selected to evaluate inhibitory activity of NSC 13778 against wild-type HIV-1 RF .…”

Viral surface glycoproteins, gp120 and gp41, as potential drug targets against HIV-1: Brief overview one quarter of a century past the approval of zidovudine, the first anti-retroviral drug

“…We know that HIV-1 infects preferably the cells that express CD4 and one of the co-receptors (CCR5 or CXCR4). However, some studies show that HIV-1 would also have the ability to infect cells lacking CD4, including B lymphocytes [26], astrocytes [27,28], thymocytes [29], CD8þ T lymphocytes [30], denditric cells [31] and epithelial cells, namely trophoblasts [32].…”