Suppression of HIV infection in AZT-treated SCID-hu mice

The SCID-hu mouse, engrafted with human hematolymphoid organs, is permissive for infection with the human immunodeficiency virus (HIV). This mouse model was used to test compounds for antiviral efficacy. Two weeks after infection with HIV, 100 percent (40/40) of SCID-hu mice were positive for HIV by the polymerase chain reaction. When first treated with 3'-azido-3'-deoxythymidine (AZT), none (0/17) were HIV-positive by this assay. However, AZT-treated SCID-hu mice did have a few infected cells; after AZT treatment was stopped, viral spread was detected by polymerase chain reaction in such mice. Thus, the SCID-hu mouse provides a means to directly compare new antiviral compounds with AZT and to further improve antiviral efficacy.     

Expanded HIV-1 cellular tropism by phenotypic mixing with murine endogenous retroviruses

In view of the current interest in in vivo murine models for acquired immunodeficiency syndrome (AIDS), the interaction between human immunodeficiency virus type 1 (HIV-1) and endogenous murine leukemia virus (MuLV)-related retroviruses was investigated with a human leukemic T cell line (PF-382x) that acquired xenotropic MuLV (X-MuLV) after in vivo passage in immunosuppressed mice. Despite similar levels of membrane CD4 expression and HIV-1 125I-labeled gp 120 binding, a dramatic acceleration in the time course of HIV-1 infection was observed in PF-382x compared to its X-MuLV-negative counterpart (PF-382). Moreover, PF-382 cells coinfected by X-MuLV and HIV-1 generated a progeny of phenotypically mixed viral particles, enabling HIV-1 to productively infect a panel of CD4- human cells, including B lymphoid cells and purified normal peripheral blood CD4-/CD8+ T lymphocytes. Mixed viral phenotypes were also produced by human CD4+ T cells coinfected with an amphotropic MuLV-related retrovirus (A-MuLV) and HIV-1. These data show that endogenous MuLV acquired by human cells transplanted into mice can significantly interact with HIV-1, thereby inducing important alterations of HIV-1 biological properties.     

Differential effects of nef on HIV replication: implications for viral pathogenesis in the host

Stable lymphoid cell lines expressing the human immunodeficiency virus type 1 (HIV-1) nef gene product, p27, were established. The presence of p27 in the lymphoid cells suppressed replication of some strains of both HIV-1 and HIV-2. This observation indicates that nef could be important in the establishment of HIV latency. In contrast, fast replicating and highly cytopathic HIV-1 isolates recovered from patients with advanced disease states were not affected by the negative effect of nef present in these lymphoid cell lines. This lack of response to nef appears to constitute another viral feature that correlates with disease progression. Thus, manipulating expression of the nef gene in vivo might influence pathogenesis in the host.     

Secretion of neurotoxins by mononuclear phagocytes infected with HIV-1

Mononuclear phagocytes (microglia, macrophages, and macrophage-like giant cells) are the principal cellular targets for human immunodeficiency virus-1 (HIV-1) in the central nervous system (CNS). Since HIV-1 does not directly infect neurons, the causes for CNS dysfunction in acquired immunodeficiency syndrome (AIDS) remain uncertain. HIV-1-infected human monocytoid cells, but not infected human lymphoid cells, released toxic agents that destroy chick and rat neurons in culture. These neurotoxins were small, heat-stable, protease-resistant molecules that act by way of N-methyl-D-aspartate receptors. Macrophages and microglia infected with HIV-1 may produce neurologic disease through chronic secretion of neurotoxic factors.     

Unexpectedly high levels of HIV-1 RNA and protein synthesis in a cytocidal infection

The expression of a laboratory strain of HIV-1 (HTLV-IIIB) has been studied in mitogen-stimulated peripheral blood lymphocytes (PBLs) and in two lymphoid cell lines (CEM cells and C8166 cells). HIV-expressing cells contained from 300,000 to 2,500,000 copies of viral RNA per cell. Near-synchronous expression of an active infection could be achieved in C8166 cells. In these cells, the high copy numbers of viral RNA used as much as 40% of total protein synthesis for the production of viral gag protein, with high levels of viral RNA and protein synthesis preceding cell death by 2 to 4 days.     

Sexual transmission and propagation of SIV and HIV in resting and activated CD4+ T cells

In sexual transmission of simian immunodeficiency virus, and early and later stages of human immunodeficiency virus-type 1 (HIV-1) infection, both viruses were found to replicate predominantly in CD4(+) T cells at the portal of entry and in lymphoid tissues. Infection was propagated not only in activated and proliferating T cells but also, surprisingly, in resting T cells. The infected proliferating cells correspond to the short-lived population that produces the bulk of HIV-1. Most of the HIV-1-infected resting T cells persisted after antiretroviral therapy. Latently and chronically infected cells that may be derived from this population pose challenges to eradicating infection and developing an effective vaccine.     

Quiescent T lymphocytes as an inducible virus reservoir in HIV-1 infection

To better understand the basis for human immunodeficiency virus type 1 (HIV-1) persistence and latency, the form in which viral DNA exists in the peripheral T lymphocyte reservoir of infected individuals was investigated. In asymptomatic individuals, HIV-1 was harbored predominantly as full-length, unintegrated complementary DNA. These extrachromosomal DNA forms retained the ability to integrate upon T cell activation in vitro. In patients with acquired immunodeficiency syndrome (AIDS), there was an increase in integrated relative to extrachromosomal DNA forms. By analysis of DNA from patient lymphocyte subpopulations depleted of human lymphocyte antigen-Dr receptor-positive cells, quiescent T cells were identified as the source of extrachromosomal HIV-1 DNA. Thus quiescent T lymphocytes may be a major and inducible HIV-1 reservoir in infected individuals.     

Biologic features of HIV-1 that correlate with virulence in the host

Individuals infected with the human immunodeficiency virus type 1 (HIV-1) may be asymptomatic or have AIDS-related complex or the acquired immuno deficiency syndrome (AIDS). Little is known about the factors that influence progression of infection to AIDS. In this study of isolates of HIV-1 obtained at intervals during the infection of four individuals, the development of disease was found to be correlated with the emergence of HIV-1 variants that were more cytopathic in vitro as the disease progressed and that replicated more efficiently in a wide variety of different human cells. The biologic properties of HIV-1 in vitro thus appear to reflect its virulence in the host. Further studies of such sequentially isolated viruses may lead to the identification of viral genes that govern pathogenesis.     

A synthetic HIV-1 protease inhibitor with antiviral activity arrests HIV-like particle maturation

A synthetic peptidemimetic substrate of the human immunodeficiency virus 1 (HIV-1) protease with a nonhydrolyzable pseudodipeptidyl insert at the protease cleavage site was prepared. The peptide U-81749 inhibited recombinant HIV-1 protease in vitro (inhibition constant Ki of 70 nanomolar) and HIV-1 replication in human peripheral blood lymphocytes (inhibitory concentration IC50 of 0.1 to 1 micromolar). Moreover, 10 micromolar concentrations of U-81749 significantly inhibited proteolysis of the HIV-1 gag polyprotein (p55) to the mature viral structural proteins p24 and p17 in cells infected with a recombinant vaccinia virus expressing the HIV-1 gag-pol genes. The HIV-1 like particles released from inhibitor-treated cells contained almost exclusively p55 and other gag precursors, but not p24. Incubation of HIV-like particles recovered from drug-treated cultures in drug-free medium indicated that inhibition of p55 proteolysis was at least partially reversible, suggesting that U-81749 was present within the particles.     

Blocking of HIV-1 infectivity by a soluble, secreted form of the CD4 antigen

The initial event in the infection of human T lymphocytes, macrophages, and other cells by human immunodeficiency virus (HIV-1) is the attachment of the HIV-1 envelope glycoprotein gp120 to its cellular receptor, CD4. As a step toward designing antagonists of this binding event, soluble, secreted forms of CD4 were produced by transfection of mammalian cells with vectors encoding versions of CD4 lacking its transmembrane and cytoplasmic domains. The soluble CD4 so produced binds gp120 with an affinity and specificity comparable to intact CD4 and is capable of neutralizing the infectivity of HIV-1. These studies reveal that the high-affinity CD4-gp120 interaction does not require other cell or viral components and may establish a novel basis for therapeutic intervention in the acquired immune deficiency syndrome (AIDS).     

Human immunodeficiency virus infection of human-PBL-SCID mice

Severe combined immunodeficient (SCID) mice reconstituted with human peripheral blood leukocytes (hu-PBL-SCID mice) have inducible human immune function and may be useful as a small animal model for acquired immunodeficiency syndrome (AIDS) research. Hu-PBL-SCID mice infected with human immunodeficiency virus-1 (HIV-1) contained virus that was recoverable by culture from the peritoneal cavity, spleen, peripheral blood, and lymph nodes for up to 16 weeks after infection; viral sequences were also detected by in situ hybridization and by amplification with the polymerase chain reaction (PCR). Mice could be infected with multiple strains of HIV-1, including LAV-1/Bru, IIIB, MN, SF2, and SF13. HIV-1 infection affected the concentration of human immunoglobulin and the number of CD4+ T cells in the mice. These results support the use of the hu-PBL-SCID mouse for studies of the pathogenesis and treatment of AIDS.     

Control of early viral and bacterial distribution and disease by natural antibodies

Natural antibodies are often dismissed from immunological analysis as "background," but they may play an important role in conferring immunity against infections. In antibody-free mice infected with various viruses or with Listeria monocytogenes, viral or bacterial titers in peripheral organs, including the kidney and brain, were 10 to 100 times greater than in antibody-competent mice (and enhanced their susceptibility to some infections), and titers in secondary lymphoid organs were 10 to 100 times lower than in antibody-competent mice. Thus, natural antibodies play a crucial role by preventing pathogen dissemination to vital organs and by improving immunogenicity through enhanced antigen-trapping in secondary lymphoid organs.     

Effect of Zinc Toxicity on Lymphoid Organs in Chickens

The experiment was conducted with the objective of studies on effects of zinc toxicity on lymphoid organs by the methods of experimental pathology and flow cytometry (FCM). 200one-day-old Avian broilers were divided into four groups randomly, and fed on diets as follows: controls (Zn 100mg kg-1)and zinc toxic (Zn 1 500mg kg-1, zinc toxic group Ⅰ; Zn 2 000 mg kg-1, zinc toxic group Ⅱ; Zn 2 500 mg kg-1, zinc toxic group Ⅲ) for seven weeks. The weight and growth index of the thymus, spleen and bursa of Fabricius were reduced in both zinc toxic group Ⅱ and zinc toxic group Ⅲ when compared with those of control group. The G0/G1 phase of the cell cycles of the lymphoid organs was higher, and S, G2+M phases lower in zinc toxic groups Ⅱ and Ⅲ than in control group. Lymphocytes were depleted and degenerate in the lymphoid organs. The reticular cells of the bursa of Fabricius proliferated and the reticular cells of the thymus were also degenerate and necrotic,particularly in zinc toxic groups Ⅱ and Ⅲ. The results demonstrated that more than 1 500 mg kg-1 impaired the progression of lymphocytes from the G0/G1 phase to S phase obviously, inhibited the development of lymphoid organs and caused marked pathological changes in the lymphoid organs. Potential mechanisms underlying these observations are also discussed.     

Prevention of HIV-1 infection and preservation of CD4 function by the binding of CPFs to gp120

Infection by human immunodeficiency virus type-1 (HIV-1) is initiated when its envelope protein, gp120, binds to its receptor, the cell surface glycoprotein CD4. Small molecules, termed N-carbomethoxycarbonyl-prolyl-phenylalanyl benzyl esters (CPFs), blocked this binding. CPFs interacted with gp120 and did not interfere with the binding of CD4 to class II major histocompatibility complex molecules. One CPF isomer, CPF(DD), preserved CD4-dependent T cell function while inhibiting HIV-1 infection of H9 tumor cells and human T cells. Although the production of viral proteins in infected T cells is unaltered by CPF(DD), this compound prevents the spread of infection in an in vitro model system.     

Effect of Copper Toxicity on Lymphoid Organs in Ducklings

210 one-day-old Tianfu meat ducklings ware divided into three groups,and fed on diets as follows: (1) control (Cu 12.16 mg kg-1),(2) copper toxic Ⅰ (Cu 850 mg kg-1) and (3)copper toxic Ⅱ( Cu 1 050 mg kg-1) for studies on effects of copper toxicity on lymphoid organs in duckling with the methods of experimental pathology and flow cytometry (FCM).The weight and growth index of the thymus,spleen and bursa of Fabricius were markedly reduced (P＜ 0.05 or P＜ 0.01) in both copper toxic group Ⅰ and Cu toxic group Ⅱ when compared with control group.The G0/G1 phase of the cell cycle of the thymus,spleen and bursa of Fabricius was much higher,and S,G2+M phases lower in Cu toxic groups Ⅰ and Ⅱ than in the control group.There were lymphocyte degeneration and depletion of lymphoid organs,and the reticular cells of spleen and bursa of Fabricius proliferated and the reticular cells of thymus were also degenerate and necrotic in Cu toxic groups.The results demonstrated that Cu toxicity seriously impaired the progression of lymphocytes from the G0/G1 phase to S phase,inhibited the development of lymphoid organs and caused marked pathological injury in lymphoid organs.The results also showed that the effect of Cu toxicity on the primary lymphoid organs occurred stronger than on the secondary lymphoid organs.The effect of Cu toxicity was the greatest on the bursa of Fabricius,followed hy the thymus,and then the spleen.Potential mechanisms underlying aforementioned observation were also discussed.key words: Copper toxicity,Lesion,Cell cycle,Lymphoid organ,Duckling     

Selective elimination of HIV-1-infected cells with an interleukin-2 receptor-specific cytotoxin

Infection by human immunodeficiency virus type 1 (HIV-1) is associated with cellular activation and expression of the interleukin-2 (IL-2) receptor. A genetically engineered fusion toxin, DAB486 IL-2, that contains the enzymatic site and translocation domain of diphtheria toxin and the receptor binding domain of IL-2 specifically kills cells that express high-affinity IL-2 receptors. This toxin selectively eliminated the HIV-1-infected cells from mixed cultures of infected and uninfected cells and inhibited production of viral proteins and infectious virus. Thus, cellular activation antigens present a target for early antiviral intervention.     

Rational design of peptide-based HIV proteinase inhibitors

A series of peptide derivatives based on the transition-state mimetic concept has been designed that inhibit the proteinase from the human immunodeficiency virus (HIV). The more active compounds inhibit both HIV-1 and HIV-2 proteinases in the nanomolar range with little effect at 10 micromolar against the structurally related human aspartic proteinases. Proteolytic cleavage of the HIV-1 gag polyprotein (p55) to the viral structural protein p24 was inhibited in chronically infected CEM cells. Antiviral activity was observed in the nanomolar range (with one compound active below 10 nanomolar) in three different cell systems, as assessed by p24 antigen and syncytium formation. Cytotoxicity was not detected at 10 and 5 micromolar in C8166 and JM cells, respectively, indicating a high therapeutic index for this new class of HIV proteinase inhibitors.