Structure and origin of HIV type 1 DNA in persistently infected B lymphoblastoid cell lines

Aberrant life cycle of human immunodeficiency virus type 1 CRF15_01B-like clinical isolates from Thailand in human CD4+ T-cell lines

Human immunodeficiency virus type 1 (HIV-1) is separated into several subtypes and circulating recombinant forms (CRFs). Here, infections of 4 clinical isolates (0-47-1, CU98-26, CU98-28, and CU98-31) from Thailand were examined in human CD4(+) T-cell lines, MT-4 and MOLT-4. The CU98-26 isolates in both cells and 0-47-1 in MT-4 established chronic infections, as in control 2 subtype B isolates from Japan, while 0-47-1 in MOLT-4 caused a latent infection. In contrast, CU98-28 and CU98-31 established aberrant infections in both cells. Integrated provirus was detected in all the chronic infections, including 0-47-1 in both cells. In contrast, extrachromosomal circular forms of HIV-1 DNA were detected in CU98-28- and CU98-31-infected cells, whereas the amount of the integrated form was below the limit of detection. Interestingly, phylogenetic trees and sequencing revealed that all the Thai isolates, except 0-47-1, displayed CRF15_01B-like mosaic structures of CRF01_AE with subtype B-like sequences in several regions that were apparently different from those of the inocula in peripheral blood mononuclear cells. Thus, in the infections of most of the above Thai isolates it was suggested that a minor population with mosaic patterns having multiple breakpoints between CRF01_AE and subtype B in the inocula could be selected by the T-cell lines.

CD4-independent infection of human B cells with HIV type 1: detection of unintegrated viral DNA

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.

Cotransduction of nondividing cells using lentiviral vectors

Diseases such as AIDS and cancers may require the introduction of multiple genes into either stem cells or nondividing cells, among others, for therapeutic purposes. Such genes may act at different points of the disease pathway, or may constitute a regulatory loop to bypass or rectify the defective gene or pathway underpinning the disease. Ideally, the therapeutic genes must be transduced together in diverse combinations, and the introduction should occur without constraints. Since lentiviral vectors can transduce both dividing and nondividing cells, they are ideal vehicles to investigate combinatorial gene transfer into diverse cells. In this study, we demonstrate that by using two independent lentiviral vectors, pseudotyped with the protein g of vesicular stomatitis virus, up to four genes can be introduced simultaneously into single dividing and nondividing cells. Up to 45% and 73% of dividing and nondividing cells, respectively, could be transduced with two lentiviral vectors. The efficiency of cotransducing a single cell was the product of the individual transduction efficiencies and suggested the absence of viral interference. Multiple and combinatorial gene transduction using lentiviral vectors may prove useful in gene therapy.

Unintegrated HIV-1 circular 2-LTR proviral DNA as a marker of recently infected cells: relative effect of recombinant CD4, zidovudine, and saquinavir in vitro

Unintegrated HIV-1 proviral DNA is one of the earliest detectable forms of HIV-1, and the influence of an antiretroviral drug on its appearance may reflect the efficacy of that agent in preventing infection of new cells. We characterized the dynamics of HIV-1 p24 (p24) antigen production, HIV-1 gag DNA, tandem long-terminal-repeat circular unintegrated proviral (2-LTR) HIV-1 DNA, HIV-1 tat mRNA, and cell viability in the presence of three antiretroviral agents: recombinant soluble CD4 (rsCD4), zidovudine, and saquinavir. Interference with HIV-1 entry by rsCD4 decreased p24 antigen levels modestly, decreased HIV-1 gag by twofold, and 2-LTR was detectable at the end of the culture period. Inhibition of reverse transcription by zidovudine decreased p24 antigen levels modestly, decreased HIV-1 gag by 19-fold, and inhibited detection of 2-LTR HIV-1 DNA. The protease inhibitor, saquinavir, had the greatest overall effect, with the lowest levels of p24 antigen and HIV-1 gag, and inhibition of 2-LTR. There was no detection of tat mRNA in the saquinavir-treated cultures. In addition, cell viability was significantly higher in cultures treated with saquinavir. In these experiments, 2-LTR HIV-1 DNA was indicative of the relative inhibitory effects of three antiretroviral agents acting at different steps of the HIV-1 replication cycle. We demonstrated in vitro that 2-LTR HIV-1 DNA was a useful indicator of an antiretroviral drug in preventing new cell infection and could be utilized as a dynamic marker of drug efficacy in HIV-1-infected patients.