A peptide derived from bee venom-secreted phospholipase A2 inhibits replication of T-cell tropic HIV-1 strains via interaction with the CXCR4 chemokine receptor.

We have previously shown that secreted phospholipases A2 (sPLA2) from bee and snake venoms have potent anti-human immunodeficiency virus (HIV) activity. These sPLA2s block HIV-1 entry into host cells through a mechanism linked to sPLA2 binding to cells. In this study, 12 synthetic peptides derived from bee venom sPLA2 (bvPLA2) have been tested for inhibition of HIV-1 infection. The p3bv peptide (amino acids 21 to 35 of bvPLA2) was found to inhibit the replication of T-lymphotropic (T-tropic) HIV-1 isolates (ID(50) = 2 microM) but was without effect on monocytotropic (M-tropic) HIV-1 isolates. p3bv was also found capable of preventing the cell-cell fusion process mediated by T-tropic HIV-1 envelope. Finally, p3bv can inhibit the binding of radiolabeled stromal cell-derived factor (SDF)-1alpha, the natural ligand of CXCR4, and the binding of 12G5, an anti-CXCR4 monoclonal antibody. Taken together, these results indicate that p3bv blocks the replication of T-tropic HIV-1 strains by interacting with CXCR4. Its mechanism of action however appears distinct from that of bvPLA2 because the latter inhibits replication of both T-tropic and M-tropic isolates and does not compete with SDF-1alpha and 12G5 binding to CXCR4.

Secreted phospholipases A(2), a new class of HIV inhibitors that block virus entry into host cells.

Mammalian and venom secreted phospholipases A(2) (sPLA(2)s) have been associated with a variety of biological effects. Here we show that several sPLA(2)s protect human primary blood leukocytes from the replication of various macrophage and T cell-tropic HIV-1 strains. Inhibition by sPLA(2)s results neither from a virucidal effect nor from a cytotoxic effect on host cells, but it involves a more specific mechanism. sPLA(2)s have no effect on virus binding to cells nor on syncytia formation, but they prevent the intracellular release of the viral capsid protein, suggesting that sPLA(2)s block viral entry into cells before virion uncoating and independently of the coreceptor usage. Various inhibitors and catalytic products of sPLA(2) have no effect on HIV-1 infection, suggesting that sPLA(2) catalytic activity is not involved in the antiviral effect. Instead, the antiviral activity appears to involve a specific interaction of sPLA(2)s to host cells. Indeed, of 11 sPLA(2)s from venom and mammalian tissues assayed, 4 venom sPLA(2)s were found to be very potent HIV-1 inhibitors (ID(50) < 1 nM) and also to bind specifically to host cells with high affinities (K(0.5) < 1 nM). Although mammalian pancreatic group IB and inflammatory-type group IIA sPLA(2)s were inactive against HIV-1 replication, our results could be of physiological interest, as novel sPLA(2)s are being characterized in humans.

3'-End modification of the adenoviral VA1 gene affects its expression in human cells: consequences for the design of chimeric VA1 RNA ribozymes.

Polymerase III (pol III)-dependent genes, like the adenoviral VA1 gene, are of particular interest for expressing small therapeutic RNAs into cells. A new VA1 RNA carrier molecule was generated through the deletion of the VA1 RNA central domain to give rise to the VAdeltaIV RNA vector that was devoid of undesirable physiologic activity (i.e., inhibition of the interferon-induced protein kinase, PKR). This vector was used to express in human cells hammerhead ribozymes targeted against the human immunodeficiency virus (HIV). Eight anti-HIV ribozymes were inserted at the 3'-end of this vector immediately before the four T-residues that serve as a transcription termination signal. Although the constructs were active in vitro, they failed to inhibit HIV replication in transient assays. Analysis of the intracellular ribozyme expression in cells revealed several anomalies. First, using mutant derivatives, we showed that the presence of two or three consecutive T-residues in the ribozyme portion was sufficient to promote the release of anomalous short transcripts. Second, when the ribozyme did not contain T-rich sequence, full-length transcripts were produced, but these transcripts were very unstable and were retained in the cell nucleus. In contrast, insertion of the ribozyme in place of the central domain of VA1 RNA led to production of full-length transcripts that were stable and located in the cytoplasm but that were not found to be active in vitro. Taken together, these results have important consequences for the future design of active intracellular ribozymes based on the use of pol III-transcribed genes.

[Comparative study of ultrasonography and scintigraphy in liver metastases detection (author's transl)]. / Etude comparative de l'échographie et de la scintigraphie dans la détection des métastases hépatiques.

The sensitivity and specificity of ultrasonography and scintigraphy for detecting the presence of liver metastases were compared in 250 patients with cancer. In the 80 cases with metastases, the sensitivity of ultrasonography was 95%, that of scintigraphy being 75%. In 170 cases without metastases the specificity of ultrasonography was 96%, that of scintigraphy being 92%. These results, confirmed by reports in the published literature, show that ultrasonography should be the first morphological-detecting examination for suspected hepatic metastases, with scintigraphy as a second option.