New antiretroviral drugs

Implementation and outcomes of a patient tracing programme for HIV in Trinidad and Tobago

A patient tracing programme was implemented at an HIV clinic in Trinidad and Tobago to address the problem of defaulters from HIV care and non-adherence to antiretroviral treatment (ART). The study objective was to evaluate the implementation and outcomes of this programme conducted between April and September 2017. Using patient tracing contact methods, trained social workers attempted to contact 1058 patients lost to follow up (LTFU) between July 2016 and March 2017. Of the 1058 LTFU, 192 were ineligible: 27 (2.5%) were transferred to another clinic, 64 (6%) deceased, 35 (3.3%) hospitalised, 50 (4.7%) migrated and 16 (1.5%) incarcerated. Of the 866 eligible patients for patient tracing, 277 (32%) remained permanently LTFU and 589 (68%) were successfully contacted, re-engaged in care and received adherence counselling. Of the 589 who returned to care, 507 (86%) restarted ART. The three most common barriers reported among the 589 who were reengaged were 'forgetting their appointments' (20%), 'being too busy/work' (16%), and 'not wanting to be seen attending the HIV clinic' (12%). The study findings demonstrated the tracing programme as feasible for re-engaging those who are LTFU and highlighted barriers that can be addressed to further improve retention in HIV care among people living with HIV.

HIV-1 reverse transcriptase (RT) polymorphism 172K suppresses the effect of clinically relevant drug resistance mutations to both nucleoside and non-nucleoside RT inhibitors

Polymorphisms have poorly understood effects on drug susceptibility and may affect the outcome of HIV treatment. We have discovered that an HIV-1 reverse transcriptase (RT) polymorphism (RT(172K)) is present in clinical samples and in widely used laboratory strains (BH10), and it profoundly affects HIV-1 susceptibility to both nucleoside (NRTIs) and non-nucleoside RT inhibitors (NNRTIs) when combined with certain mutations. Polymorphism 172K significantly suppressed zidovudine resistance caused by excision (e.g. thymidine-associated mutations) and not by discrimination mechanism mutations (e.g. Q151M complex). Moreover, it attenuated resistance to nevirapine or efavirenz imparted by NNRTI mutations. Although 172K favored RT-DNA binding at an excisable pre-translocation conformation, it decreased excision by thymidine-associated mutation-containing RT. 172K affected DNA handling and decreased RT processivity without significantly affecting the k(cat)/K(m) values for dNTP. Surface plasmon resonance experiments revealed that RT(172K) decreased DNA binding by increasing the dissociation rate. Hence, the increased zidovudine susceptibility of RT(172K) results from its increased dissociation from the chain-terminated DNA and reduced primer unblocking. We solved a high resolution (2.15 Å) crystal structure of RT mutated at 172 and compared crystal structures of RT(172R) and RT(172K) bound to NNRTIs or DNA/dNTP. Our structural analyses highlight differences in the interactions between α-helix E (where 172 resides) and the active site β9-strand that involve the YMDD loop and the NNRTI binding pocket. Such changes may increase dissociation of DNA, thus suppressing excision-based NRTI resistance and also offset the effect of NNRTI resistance mutations thereby restoring NNRTI binding.

Retention and loss to follow-up in antiretroviral treatment programmes in southeast Nigeria

BACKGROUND

This study generated new information about the outcomes of patients enrolled in antiretroviral treatment programmes, as well as the true outcomes of those lost to follow-up (LTF).

METHODS

Anonymized data were collected for patients enrolled over a 12-month period from two programmes (public and private) in southeast Nigeria. Estimates of retention, LTF, mortality and transfers were computed. All LTF enrollees (defined as patients who had missed three scheduled visits) whose contact information met pre-defined criteria were traced.

RESULTS

A total of 481 (public) and 553 (private) records were included. Median duration of follow-up was about 14 months. Cumulative retention and LTF proportions were 66·5 and 32·8% (public), and 82·6 and 11·0% (private) respectively. LTF rates at third, sixth, ninth and twelfth months were 7·5, 19·3, 25·4 and 29·6% respectively (public), and 4·1, 7·1, 9·0 and 10·0% (private). LTF was higher among males, patients with CD4(+) cell count ≤200 and public programme enrollees. For the public facility, 56·7% of 104 traceable patients were dead and 38·8% were alive; the figures were 34·2 and 60·5% of 46 patients respectively for the private. Most deaths had occurred by the third month.

CONCLUSION

Not all patients enrolled for treatment were retained. Though some died, many were LTF, lived within the community, and could develop and transmit resistant viral stains. Most traced patients were dead by the third month and poor contact information limited the effectiveness of tracing. Antiretroviral treatment programmes need to improve documentation processes and develop and implement tracing strategies.

A genomic and bioinformatics analysis of the integration of HIV in peripheral blood mononuclear cells

The mechanistic basis of the target-site preference of lentivirus DNA integration is not well understood. In the present in silico study, we describe the integrational profile of simultaneous HIV-1 and HIV-2 infection. A total of 352 genomic DNA sequences from human peripheral blood mononuclear cells (PBMCs) obtained from GenBank and possessing the 5' LTR of HIV were used to characterize the structure and composition of local chromatin associated with high frequency integration sites. These sequences were aligned with the draft human genome (hg18) using BLAST (NCBI) and BLAT (UCSC) in order to derive information about chromosome localization, functional aspects of coding protein genes, CpG island number, and repetitive elements flanking integration sites. No significant differences in the integrational profile between HIV-1 and HIV-2 were found. However, we observed a tendency in both lentiviruses to integrate in the vicinity of protein coding genes. Multiple regression analysis showed a strong correlation between the number of genes and the number of CpG islands in regions with high integration frequency, mainly in chromosome 17 (R = 0.95, p < 0.05). Our results provide strong evidence that HIV-1 and HIV-2 have common genomic environments in the local chromatin regions with high gene density and CpG islands. The understanding of local genomic environments with a high frequency of integration would be the starting point to develop novel antiviral strategies for lentiviral infection.

Distinct mutation pathways of non-subtype B HIV-1 during in vitro resistance selection with nonnucleoside reverse transcriptase inhibitors

Studies were conducted to investigate mutation pathways among subtypes A, B, and C of human immunodeficiency virus type 1 (HIV-1) during resistance selection with nonnucleoside reverse transcriptase inhibitors (NNRTIs) in cell culture under low-multiplicity of infection (MOI) conditions. The results showed that distinct pathways were selected by different virus subtypes under increasing selective pressure of NNRTIs. F227C and Y181C were the major mutations selected by MK-4965 in subtype A and C viruses during resistance selection. With efavirenz (EFV), F227C and V106M were the major mutations responsible for viral breakthrough in subtype A viruses, whereas a single pathway (G190A/V106M) accounted for mutation development in subtype C viruses. Y181C was the dominant mutation in the resistance selection with etravirine (ETV) in subtype A, and E138K/H221Y were the mutations detected in the breakthrough viruses from subtype C viruses with ETV. In subtype B viruses, on the other hand, known NNRTI-associated mutations (e.g., Y181C, P236L, L100I, V179D, and K103N) were selected by the NNRTIs. The susceptibility of the subtype A and B mutant viruses to NNRTIs was determined in order to gain insight into the potential mechanisms of mutation development. Collectively, these results suggest that minor differences may exist in conformation of the residues within the NNRTI binding pocket (NNRTIBP) of reverse transcriptase (RT) among the three subtypes of viruses. Thus, the interactions between NNRTIs and the residues in the NNRTIBPs of different subtypes may not be identical, leading to distinct mutation pathways during resistance selection in cell culture.

Bevirimat: a novel maturation inhibitor for the treatment of HIV-1 infection

Existing antiretroviral treatments for HIV type-1 (HIV-1) disease are limited by problems of resistance and drug-drug interactions. Bevirimat is a novel HIV-1 maturation inhibitor with a mechanism of action that is distinct from other antiretroviral agents. Specific inhibition of the final rate-limiting step in Gag processing by bevirimat prevents release of mature capsid protein from its precursor (CA-SP1), resulting in the production of immature, non-infectious virus particles. Bevirimat inhibits replication of both wild-type and drug-resistant HIV-1 isolates in vitro, achieving similar 50% inhibitory concentration values with both categories. Serial drug passage studies have identified six single amino acid substitutions that independently confer bevirimat resistance. These resistance mutations occur at or near the CA-SP1 cleavage site, which is not a known target for resistance to other antiretroviral drugs. Bevirimat has demonstrated a consistent pharmacokinetic profile in healthy volunteers and HIV-infected patients, with peak plasma concentrations attained approximately 1-3 h after dosing. Plasma concentrations decrease in a log-linear manner with a mean plasma elimination halflife of 58-80 h, supporting once-daily dosing. Animal studies suggest that elimination of bevirimat is primarily by hepatic glucuronidation and hepatobiliary excretion. There is minimal renal elimination, with < 1% of the administered dose appearing in the urine. In responsive patients, bevirimat has demonstrated a robust dosedependent reduction in viral load (> 1.5 log10 copies/ml). Short-term administration (< or = 14 days) of bevirimat is well tolerated, even when used in combination with other antiretroviral agents. Further studies to evaluate the long-term efficacy and tolerability of bevirimat are currently underway.

Design and characterization of an HIV-specific ribonuclease zymogen

Ribonucleases are evoking medical interest because of their intrinsic cytotoxic activity. Most notably, ranpirnase, which is an amphibian ribonuclease, is in advanced clinical trials as a chemotherapeutic agent for the treatment of cancer. Here, we describe a strategy to create a novel antiviral agent based on bovine pancreatic ribonuclease (RNase A), a mammalian homologue of ranpirnase. Specifically, we have linked the N- and C-termini of RNase A with an amino acid sequence that is recognized and cleaved by human immunodeficiency virus (HIV) protease. This linkage obstructs the active site, forming an HIV-specific RNase A zymogen. Cleavage by HIV-1 protease increases ribonucleolytic activity by 50-fold. By relying on the proper function of HIV-1 protease, rather than its inhibition, our approach will not engender known mechanisms of resistance. Thus, we report an initial step toward a new class of agents for the treatment of HIV/AIDS.