Integration of human immunodeficiency virus as a target for antiretroviral therapy

Development and Identification of a Novel Anti-HIV-1 Peptide Derived by Modification of the N-Terminal Domain of HIV-1 Integrase

The viral enzyme integrase (IN) is essential for the replication of human immunodeficiency virus type 1 (HIV-1) and represents an important target for the development of new antiretroviral drugs. In this study, we focused on the N-terminal domain (NTD), which is mainly involved into protein oligomerization process, for the development and synthesis of a library of overlapping peptide sequences, with specific length and specific offset covering the entire native protein sequence NTD IN 1–50. The most potent fragment, VVAKEIVAH (peptide 18), which includes a His residue instead of the natural Ser at position 39, inhibits the HIV-1 IN activity with an IC₅₀ value of 4.5 μM. Amino acid substitution analysis on this peptide revealed essential residues for activity and allowed us to identify two nonapeptides (peptides 24 and 25), that show a potency of inhibition similar to the one of peptide 18. Interestingly, peptide 18 does not interfere with the dynamic interplay between IN subunits, while peptides 24 and 25 modulated these interactions in different manners. In fact, peptide 24 inhibited the IN-IN dimerization, while peptide 25 promoted IN multimerization, with IC₅₀ values of 32 and 4.8 μM, respectively. In addition, peptide 25 has shown to have selective anti-infective cell activity for HIV-1. These results confirmed peptide 25 as a hit for further development of new chemotherapeutic agents against HIV-1.

Discovery and significance of new human T-lymphotropic viruses: HTLV-3 and HTLV-4

Human T-lymphotropic virus type 1 (HTLV-1) and type 2 (HTLV-2) were discovered approximately 30 years ago and they are associated with various lymphoproliferative and neurological diseases. The estimated number of infected people is 10-20 million worldwide. In 2005, two new HTLV-1/HTLV-2-related viruses were detected, HTLV-3 and HTLV-4, from the same geographical area of Africa. In the last 4 years, their complete genomic sequences were determined and some of their characteristic features were studied in detail. These newly discovered retroviruses alongside their human (HTLV-1 and -2) and animal relatives (simian T-lymphotropic virus type 1-3) are reviewed. The potential risks associated with these viruses and the potential antiretroviral therapies are also discussed.

HIV-1 IN inhibitors: 2010 update and perspectives

Integrase (IN) is the newest validated target against AIDS and retroviral infections. The remarkable activity of raltegravir (Isentress((R))) led to its rapid approval by the FDA in 2007 as the first IN inhibitor. Several other IN strand transfer inhibitors (STIs) are in development with the primary goal to overcome resistance due to the rapid occurrence of IN mutations in raltegravir-treated patients. Thus, many scientists and drug companies are actively pursuing clinically useful IN inhibitors. The objective of this review is to provide an update on the IN inhibitors reported in the last two years, including second generation STI, recently developed hydroxylated aromatics, natural products, peptide, antibody and oligonucleotide inhibitors. Additionally, the targeting of IN cofactors such as LEDGF and Vpr will be discussed as novel strategies for the treatment of AIDS.

Human immunodeficiency virus type 1 (HIV-1) integration: a potential target for microbicides to prevent cell-free or cell-associated HIV-1 infection

Conceptually, blocking human immunodeficiency virus type 1 (HIV-1) integration is the last possibility for preventing irreversible cellular infection. Using cocultures of monocyte-derived dendritic cells and CD4(+) T cells, which represent primary targets in sexual transmission, we demonstrated that blocking integration with integrase strand transfer inhibitors (InSTIs), particularly L-870812, could consistently block cell-free and cell-associated HIV-1 infection. In a pretreatment setting in which the compound was present before and during infection and was afterwards gradually diluted during the culture period, the naphthyridine carboxamide L-870812 blocked infection with the cell-free and cell-associated HIV-1 Ba-L strain at concentrations of, respectively, 1,000 and 10,000 nM. The potency of L-870812 was similar to that of the nucleotide reverse transcriptase inhibitor R-9-(2-phosphonylmethoxypropyl) adenine (PMPA) but one or two orders of magnitude lower than those of the nonnucleoside reverse transcriptase inhibitors UC781 and TMC120. In contrast, the diketo acid RDS derivative InSTIs showed clear-cut but weaker antiviral activity than L-870812. Moreover, L-870812 completely blocked subtype C and CRFO2_AG primary isolates, which are prevalent in the African heterosexual epidemic. Furthermore, the addition of micromolar concentrations of L-870812 even 24 h after infection could still block both cell-free and cell-associated Ba-L, opening the prospect of postexposure prophylaxis. Finally, an evaluation of the combined activity of L-870812 with either T20, zidovudine, PMPA, UC781, or TMC120 against replication-deficient HIV-1 Ba-L (env) pseudovirus suggested synergistic activity for all combinations. Importantly, compounds selected for the study by using the coculture model were devoid of acute or delayed cytotoxic effects at HIV-blocking concentrations. Therefore, these findings provide evidence supporting consideration of HIV-1 integration as a target for microbicide development.

Probing HIV-1 integrase inhibitor binding sites with position-specific integrase-DNA cross-linking assays

HIV-1 integrase binds site-specifically to the ends of the viral cDNA. We used two HIV-1 integrase-DNA cross-linking assays to probe the binding sites of integrase inhibitors from different chemical families and with different strand transfer selectivities. The disulfide assay probes cross-linking between the integrase residue 148 and the 5'-terminal cytosine of the viral cDNA, and the Schiff base assay probes cross-linking between an integrase lysine residue and an abasic site placed at selected positions in the viral cDNA. Cross-linking interference by eight integrase inhibitors shows that the most potent cross-linking inhibitors are 3'-processing inhibitors, indicating that cross-linking assays probe the donor viral cDNA (donor binding site). In contrast, strand transfer-selective inhibitors provide weak cross-linking interference, consistent with their binding to a specific acceptor (cellular DNA) site. Docking and crystal structure studies illustrate specific integrase-inhibitor contacts that prevent cross-linking formation. Four inhibitors that prevented Schiff base cross-linking to the conserved 3'-terminal adenine position were examined for inhibition at various positions within the terminal 21 bases of the viral cDNA. Two of them selectively inhibited upper strand cross-linking, whereas the other two had a more global effect on integrase-DNA binding. These findings have implications for elucidating inhibitor binding sites and mechanisms of action. The cross-linking assays also provide clues to the molecular interactions between integrase and the viral cDNA.

Synthesis and HIV-1 integrase inhibitory activity of spiroundecane(ene) derivatives

Fifteen 2,4-dioxaspiro[5.5]undecane ketone and 2,4-dioxa-spiro[5.5]undec-8-ene (spiroundecane(ene)) derivatives were synthesized using the Diels-Alder reaction. Inhibition of human immunodeficiency virus integrase (IN) was examined. Eight spiroundecane(ene) derivatives inhibited both 3'-processing and strand transfer reactions catalyzed by IN. SAR studies showed that the undecane core with at least one furan moiety is preferred for IN inhibition. Moreover, crosslinking experiments showed that spiroundecane derivatives did not affect IN-DNA binding at concentrations that block IN catalytic activity, indicating spiroundecane derivatives inhibit preformed IN-DNA complex. The moderate toxicity of spiroundecane(ene) derivatives encourages the further design of therapeutically relevant analogues based on this novel chemotype of IN inhibitors.