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Existence of virus reservoirs makes the eradication of HIV infection extremely difficult. Current drug therapies neither eliminate these viral reservoirs nor prevent their formation. Consequently, new strategies are needed to target these reservoirs with the aim of decreasing their size. We analysed a series of jatrophane diterpenes isolated from Euphorbia hyberna and we found that one of them, SJ23B, induces the internalization of the HIV-1 receptors CD4, CXCR4 and CCR5 and prevents R5 and X4 viral infection in human primary T cells at the nanomolar range. Moreover, SJ23B is a potent antagonist of HIV-1 latency. Using Jurkat-LAT-GFP cells, a model for HIV-1 latency, we found that prostratin and SJ23B activate HIV-1 gene expression, with SJ23B being at least 10-fold more potent than prostratin. SJ23B did not elicit transforming foci activity in NIH 3T3 cells but is a potent activator of PKCalpha and delta as measured by in vitro kinase assays and by cellular translocation experiments. By using isoform-specific PKC inhibitors we found that cPKCs are critical for SJ23B-induced HIV-1 reactivation. We also showed that both SJ23B-induced IkappaBalpha degradation and NF-kappaB activation were inhibited by the classical PKC inhibitor, Gö6976. Accordingly, SJ23B synergizes with ionomycin to translocate PKCalpha to the plasma membrane and to activate the NF-kappaB pathway. Moreover, SJ23B activates both NF-kappaB and Sp1-dependent transcriptional activities in primary T cells. We have shown that diterpene jatrophanes represent a new member of anti-AIDS agents that could be developed for mitigating HIV reactivation.

The persistence of latent reservoirs of HIV-1 represents a major barrier to virus eradication in patients treated with antiretrovirals. Prostratin is a non-tumor promoting 12-deoxyphorbol monoester capable of up-regulating viral expression from latent provirus and therefore is potentially useful for HIV adjuvant therapy and similar properties might be elicited by related non-tumor promoting phorboids. We have therefore investigated a series of phorbol 13-monoesters for their capacity to reactivate HIV latency. Using a Jurkat T cell line containing latent HIV proviruses, we found that prostratin and phorbol-13-stearate effectively activate HIV-1 gene expression in these latently infected cells, with phorbol-13-stearate being at least 10-fold more potent than prostratin, and its activity rapidly decreasing with a shortening of the acyl side chain. We further demonstrated that phorbol-13-stearate and prostratin stimulate IKK-dependent phosphorylation and degradation of IkappaBalpha, leading to activation of NF-kappaB. Moreover, prostratin, phorbol-13-hexanoate and phorbol-13-stearate also activate the JNK and ERK pathways. Studies with isoform-specific PKC inhibitors suggest that the classical PKCs play a prominent role in the responses elicited by phorbol-13-stearate. Nevertheless, this compound induces a translocation pattern of the PKC isotypes alpha and delta to cellular compartments distinctly different from that elicited by prostratin and PMA.

Transcription of human immunodeficiency virus (HIV-1) is activated by viral Tat protein which regulates HIV-LTR transcription and elongation. In the present report, the evaluation of the anti-Tat activity of a combinatorial library composed of 5120 N-trialkylglycines is reported. The antiviral activity was studied through luciferase-based assays targeting the HIV-1 promoter activation induced by the HIV-1 Tat protein. We identified five peptoids with specific anti-HIV-1 Tat activity; none of these peptoids affected the binding of HIV-1 Tat protein to the viral TAR RNA. Using a recombinant-virus assay in which luciferase activity correlates with the rate of HIV-1 transcription we have detected that one of the five selected peptoids, NC37-37-15C, is a potent inhibitor of HIV-1-LTR transcription in both primary T lymphocytes and transformed cell lines. The inhibitory effect of NC37-37-15C, which is additive with azidothymidine (AZT), correlates with its ability to inhibit CTD phosphorylation and shows a suitable profile for development of novel anti-HIV-1 drugs. Likewise, the structural simplicity of N-alkylglycine oligomers makes these peptidomimetics amenable to structural manipulation, thus facilitating the optimisation of lead molecules for drug-like properties.