Objective. We evaluated the construct validity Spanish version of knowledge, stigma, norms, and self-efficacy scales regarding PrEP in MSM. Methods. Sample of 287 MSM. Exploratory confirmatory factor ...analysis and item response theory were used to validate the constructs. Correlations and confidence interval-based estimation of relevance analyses were conducted to correlate the scales with willingness and intention to use PrEP. Results. Attitude, stigma, and descriptive and subjective norms scales showed good construct validity and were related to intention and willingness to use PrEP. However, the knowledge scale and self-efficacy scales require further refinement. Conclusions. The study provides useful information for assessing information, motivation, and self-efficacy related to PrEP use. Our results could be used to test the scales and the theoretical model in other contexts to confirm their usefulness.
Transgender women TGW in Colombia are disproportionately affected by HIV due to their low sociodemographic conditions, varied risk behaviours, difficulty accessing health services, and ...discrimination. Offering pre-exposure prophylaxis PrEP as part of a combination of prevention strategies is an appropriate option for this population to reduce their risk of HIV infection. However, little is known about how to implement a PrEP program for TGW in Colombia. Between June and October 2020, we conducted individual interviews with 16 TGW from four different cities in Colombia. The interviews assessed contextual influences, knowledge, skills, perceptions, and beliefs. We used qualitative thematic analysis to identify themes and the Capability, Opportunity, Motivation, and Behavior framework to further delineate barriers and possible interventions. After delineating the main themes across the three subdomains of the model, nine barriers were identified: one related to capability, knowledge, and perception of PrEP; six related to opportunity, which includes, family relations, sexual work environment, stable partner relations, interactions with healthcare workers, health service provision, and community interactions and opportunities; and two related to motivation, mental health, and concerns about medication side effects. Mapping barriers with interventions generated the following intervention functions: education, training, enablement, and environmental structure; and the following policy functions: communication/marketing, legislation, and changes in service provision. Examples of possible interventions are presented and discussed.
Numerous studies have suggested that the K65R reverse transcriptase (RT) mutation develops more readily in subtype C than subtype B HIV-1. We recently showed that this discrepancy lies partly in the ...subtype C template coding sequence that predisposes RT to pause at the site of K65R mutagenesis. However, the mechanism underlying this observation and the elevated rates of K65R development remained unknown. Here, we report that DNA synthesis performed with subtype C templates consistently produced more K65R-containing transcripts than subtype B templates, regardless of the subtype-origin of the RT enzymes employed. These findings confirm that the mechanism involved is template-specific and RT-independent. In addition, a pattern of DNA synthesis characteristic of site-specific primer/template slippage and dislocation was only observed with the subtype C sequence. Analysis of RNA secondary structure suggested that the latter was unlikely to impact on K65R development between subtypes and that Streisinger strand slippage during DNA synthesis at the homopolymeric nucleotide stretch of the subtype C K65 region might occur, resulting in misalignment of the primer and template. Consequently, slippage would lead to a deletion of the middle adenine of codon K65 and the production of a -1 frameshift mutation, which upon dislocation and realignment of the primer and template, would lead to development of the K65R mutation. These findings provide additional mechanistic evidence for the facilitated development of the K65R mutation in subtype C HIV-1.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Ninety percent of HIV‐1‐infected people worldwide harbour non‐subtype B variants of HIV‐1. Yet knowledge of resistance mutations in non‐B HIV‐1 and their clinical relevance is limited. Although a few ...reviews, editorials and perspectives have been published alluding to this lack of data among non‐B subtypes, no systematic review has been performed to date.
With this in mind, we conducted a systematic review (1996–2008) of all published studies performed on the basis of non‐subtype B HIV‐1 infections treated with antiretroviral drugs that reported genotype resistance tests. Using an established search string, 50 studies were deemed relevant for this review.
These studies reported genotyping data from non‐B HIV‐1 infections that had been treated with either reverse transcriptase inhibitors or protease inhibitors. While most major resistance mutations in subtype B were also found in non‐B subtypes, a few novel mutations in non‐B subtypes were recognized. The main differences are reflected in the discoveries that: (i) the non‐nucleoside reverse transcriptase inhibitor resistance mutation, V106M, has been seen in subtype C and CRF01_AE, but not in subtype B, (ii) the protease inhibitor mutations L89I/V have been reported in C, F and G subtypes, but not in B, (iii) a nelfinavir selected non‐D30N containing pathway predominated in CRF01_AE and CRF02_AG, while the emergence of D30N is favoured in subtypes B and D, (iv) studies on thymidine analog‐treated subtype C infections from South Africa, Botswana and Malawi have reported a higher frequency of the K65R resistance mutation than that typically seen with subtype B.
Additionally, some substitutions that seem to impact non‐B viruses differentially are: reverse transcriptase mutations G196E, A98G/S, and V75M; and protease mutations M89I/V and I93L.
Polymorphisms that were common in non‐B subtypes and that may contribute to resistance tended to persist or become more frequent after drug exposure. Some, but not all, are recognized as minor resistance mutations in B subtypes. These observed differences in resistance pathways may impact cross‐resistance and the selection of second‐line regimens with protease inhibitors. Attention to newer drug combinations, as well as baseline genotyping of non‐B isolates, in well‐designed longitudinal studies with long duration of follow up are needed.
The genetic diversity of HIV-1 has required its classification into types and subtypes. There is controversy as to how and to what extent genetic diversity may affect the emergence of antiretroviral ...drug resistance in HIV-1 subtypes other than B. To better understand the impact of genetic diversity (represented by different HIV-1 subtypes) on resistance to reverse transcriptase and protease inhibitor drugs, a systematic review was conducted on virologic and biochemical evidence obtained from work with non-B HIV-1 subtypes. We searched 11 databases and retrieved 3,486 citations on all aspects of non-B subtype-related resistance research. Twenty-seven studies with virologic and/or biochemical data met the eligibility criteria for our systematic review. Nineteen studies were found that reported phenotypes in non-B subtypes (304 from naive isolates and 242 from drug-exposed isolates) and 11 studies that used molecular biology techniques to study non-B resistance to antiretroviral drugs. Compared to the NL4-3 laboratory strain, lower baseline susceptibilities of recombinant A/G subtype virus to protease inhibitors were observed and a substantial proportion of subtype C isolates displayed higher IC50 at baseline for atazanavir. Some A/G isolates were found to have reduced susceptibility to abacavir. Mutations not typical of B subtypes include the reverse transcriptase mutation V106M and the protease mutations M89I/V and N83T. Virologic and biochemical data suggest that K65R is more likely to emerge in subtype C HIV-1. There is evidence to suggest differential effects of other mutations according to subtype, e.g. the protease inhibitor mutations I93L and M89I/V. Importantly, the most widely used commercial phenotyping systems do not take into account gag variations among natural isolates, which could limit the accuracy of measured susceptibility. Enzymatic and virologic data support the concept that naturally occurring polymorphisms in different non-B subtypes can affect the susceptibility of HIV-1 to different antiretroviral drugs, the magnitude of resistance conferred by major mutations, and the propensity to acquire some resistance mutations. Tools may need to be optimized to accurately measure drug susceptibility of non-B subtypes, especially for protease inhibitors.
Antiretroviral Therapy Martinez-Cajas, Jorge L.; Wainberg, Mark A.
Drugs (New York, N.Y.),
2008/1, Letnik:
68, Številka:
1
Journal Article
Recenzirano
In the second decade of highly active antiretroviral therapy, drug regimens offer more potent, less toxic and more durable choices. However, strategies addressing convenient sequential use of active ...antiretroviral combinations are rarely presented in the literature. Studies have seldom directly addressed this issue, despite it being a matter of daily use in clinical practice. This is, in part, because of the complexity of HIV-1 resistance information as well as the complexity of designing these types of studies. Nevertheless, several principles can effectively assist the planning of antiretroviral drug sequencing. The introduction of tenofovir disoproxil fumarate, abacavir and emtricitabine into current nucleoside backbone options, with each of them selecting for an individual pattern of resistance mutations, now permits sequencing in the context of previously popular thymidine analogues (zidovudine and stavudine). Similarly, newer ritonavir-boosted protease inhibitors could potentially be sequenced in a manner that uses the least cross-resistance prone protease inhibitor at the start of therapy, while leaving the most cross-resistance prone drugs for later, as long as there is rationale to employ such a compound because of its utility against commonly observed drug-resistant forms of HIV-1.
We investigated the effects of mutations K65R and K65R plus M184V on enzymatic function and mechanisms of drug resistance in subtype C reverse transcriptase (RT).
Recombinant subtype C HIV-1 RTs ...containing K65R or K65R+M184V were purified from Escherichia coli. Enzyme activities and tenofovir (TFV) incorporation efficiency by wild-type (WT) and mutant RTs of both subtypes were determined in cell-free assays. Efficiency of (-) ssDNA synthesis and initiation by subtype C RTs was measured using gel-based assays with HIV-1 PBS RNA template and tRNA3Lys as primer. Single-cycle processivity was assayed under variable dNTP concentrations. Steady-state analysis was performed to measure the relative inhibitory capacity (ki/km) of TFV-disphosphate (TFV-DP). ATP-dependent excision and rescue of TFV-or ZDV-terminated DNA synthesis was monitored in time-course experiments.
The efficiency of tRNA-primed (-)ssDNA synthesis by subtype C RTs was: WT > K65R > K65R+M184V RT. At low dNTP concentration, K65R RT exhibited lower activity in single-cycle processivity assays while the K65R+M184V mutant showed diminished processivity independent of dNTP concentration. ATP-mediated excision of TFV-or ZDV-terminated primer was decreased for K65R and for K65R+M184V RT compared to WT RT. K65R and K65R+M184V displayed 9.8-and 5-fold increases in IC50 for TFV-DP compared to WT RT. The Ki/Km of TFV was increased by 4.1-and 7.2-fold, respectively, for K65R and K65R+M184V compared to WT RT.
The diminished initiation efficiency of K65R-containing RTs at low dNTP concentrations have been confirmed for subtype C as well as subtype B. Despite decreased excision, this decreased binding/incorporation results in diminished susceptibility of K65R and K65R+M184 RT to TFV-DP.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Objectives
Relatively little is known about the development of resistance to protease inhibitors (PIs) in non-B subtypes. In subtype B viruses, L89 is commonly found at position 89 in the HIV ...protease (PR) gene, whereas M89 is commonly observed as a polymorphism in other subtypes. We compared the frequencies of substitutions at position 89 in PR in tissue culture selections and in clinical databases of PI-naive and PI-experienced populations.
Methods
Representative subtype A/CRF01_AE (n = 2 and 3) and subtype C (n = 5) isolates were cultured in MT-2 cells and cord blood mononuclear cells (CBMCs), respectively, under increasing drug pressure with PIs, and drug resistance mutations were identified.
Results
The M89 natural polymorphism in non-B subtypes commonly led to the appearance of an M89T mutation in selections with atazanavir in subtypes A/AE and C, and was accompanied by other previously recognized atazanavir mutations. The M89T mutation contributed to phenotypic resistance to atazanavir and cross-resistance to lopinavir and nelfinavir, but not to other PIs. A shift from a L89 natural polymorphism to L89I/M arose in two of five subtype C selections with PIs. M89I/V/T mutations were acquired by 10%-11% of individuals harbouring non-B subtypes who were failing PI-based regimens, but were rarely observed in drug-naive persons and in patients failing non-PI-based regimens.
Conclusions
The M/L89 natural polymorphism present in non-B subtypes may lead to the M89T mutational pathway conferring resistance to atazanavir, lopinavir and nelfinavir.
The problem of HIV-1 drug resistance has established a need for new compounds that retain activity against mutated resistant viral isolates. Fortunately, a number of new compounds have recently been ...developed that possess excellent activity against HIV-1 strains that contain as many as eight relevant drug-resistance mutations in the viral protease (PR) gene. These newer protease inhibitors (PI) are characterized by higher genetic barrier for drug resistance, meaning that higher numbers of mutations are required for resistance to develop in comparison with older members of the PI family of drugs. Thus, different PIs can be used sequentially in HIV therapy in a manner that can overcome previous drug resistance and potentially forestall the development of additional resistance mutations in the viral PR. All currently used PIs, in general, require ritonavir to be used as a pharmalogical boosting agent. There is a need to develop novel PIs, that will not require such boosting, and that are also characterized by potent antiviral activity and a high genetic barrier for resistance.
HIV-1 protease inhibitors (PIs) are key components of HIV therapy. PL-100 is a novel lysine sulphonamide that demonstrates potent antiviral activity against multiresistant HIV-1 strains as well as a ...higher genetic barrier for development of resistance mutations compared with first-generation PIs. In the present study, we compared the antiviral activity of PL-100 against HIV-1 subtype B with that of darunavir.
We used tissue culture experiments to evaluate the in vitro development of resistance to PL-100 and tested the antiviral activity of several clinically approved PIs against PL-100-selected resistant variants. Structural modelling was also used to compare the binding of PL-100 and darunavir to the HIV-1 protease (PR) enzyme.
PL-100-resistant variants that emerged within 8-48 weeks showed low- to high-level resistance (3.5- to 21.6-fold) to PL-100, but commonly retained susceptibility to darunavir, which, in contrast, did not select for resistance mutations over a period of 40 weeks. Structural modelling demonstrated that binding of PL-100 was predominantly based on polar interactions and delocalized hydrophobic interactions through its diphenyl groups, while darunavir has numerous interactions with PR that include hydrogen bonding to PR backbone oxygens at amino acid positions A28, D29 and D30 via di-tetrahydrofuran (di-THF) groups.
Hydrogen-bonding contacts and the di-THF group in darunavir, as well as the hydrophobic nature of PL-100, contribute to PI binding and a high genetic barrier for resistance. Redesigning the structure of PL-100 to include a di-THF group might improve it.
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