The anti-conformation of 2',3'-dideoxy nucleosides may be essential for anti-HIV activity: evidence from the crystal structure of 2',3'-dideoxy formycin A

The crystal structure of the nucleoside 2',3'-dideoxyformycin A has been determined. The structure shows a syn conformation about the glycosidic bond, stabilised by an intramolecular hydrogen bond between the 05' and N3 atoms. HIV activity was examined in a syncytium inhibition assay. In contrast to the marked decrease in viral titre observed with 2',3'-dideoxycytidine, the formycin analogue produced no effect. It may be concluded that the syn conformation for a dideoxy nucleoside is probably deleterious to HIV inhibition of HIV replication.

Soluble CD4 blocks the infectivity of diverse strains of HIV and SIV for T cells and monocytes but not for brain and muscle cells

The CD4 antigen has been subverted as a receptor by the human and simian immunodeficiency viruses (HIV-1, HIV-2 and SIV). Several groups have reported that recombinant, soluble forms of the CD4 molecule (sCD4) block the infection of T lymphocytes by HIV-1, as CD4 binds the HIV envelope glycoprotein, gp120, with high affinity. We now report that sCD4 blocks diverse strains of HIV-1, HIV-2 and SIV, but is less effective for HIV-2. The blocking effect is apparent even after adsorption of virions to CD4 cells. Soluble CD4 prevents HIV infection of T-lymphocytic and myelomonocytic cell lines, but neither sCD4 nor anti-CD4 antibodies inhibit infection of glioma and rhabdomyosarcoma cell lines.

HIV-2 antisera cross-neutralize HIV-1

The neutralization properties of three independent HIV-2 isolates were examined in comparison with four diverse HIV-1 strains. Human sera containing antibodies specific to HIV-2 can cross-neutralize HIV-1. By contrast, HIV-1 sera are group-specific and have no neutralizing effect on HIV-2. Therefore, HIV-2 antigens may be important components for the development of broadly cross-protective AIDS vaccines.

Human immunodeficiency virus infection of monocytic and T-lymphocytic cells: receptor modulation and differentiation induced by phorbol ester

The monocytic leukemic cell line U937 can be infected with human immunodeficiency virus type 1 (HIV-1) to become permanently infected virus producers. Uninfected U937 cells express T4 (CD4) antigen and form syncytia when mixed with HIV-1 producing cells. Anti-T4 monoclonal antibodies block syncytium formation indicating that the HIV-1 receptors on U937 cells include T4 antigen. The promyelocytic leukemic cell line HL60, while expressing only low amounts of surface T4 and not forming syncytia on exposure to HIV-1, can be infected by HIV-1 at lower efficiency than U937 and T-cell lines. 12-O-Tetradecanoylphorbol-13-acetate (TPA) treatment induces the differentiation of U937 cells into macrophages. HIV-infected U937 cells retain the ability to differentiate, though less efficiently, as shown by the appearance of monocyte/macrophage surface markers. T4 antigen on both U937 and T-cell lines is down regulated by TPA treatment. Functional receptors for HIV-1, assayed by syncytium induction and pseudotype plating, are lost concomitantly with T4 antigen following TPA treatment of U937 cells and T cells.

The scapular flap--an anatomical and clinical study

The scapular flap is a medium-sized flap combining many of the good qualities of others, such as thinness and minimal donor site deficit, with the potentialities of a consistently long pedicle that allows combination with other adjacent flaps. The anatomy of the flap and its application in nine clinical cases is described.