World-wide variation in HIV-1 phenotypic susceptibility in untreated individuals: biologically relevant values for resistance testing

324

480

Maraviroc is a CCR5 antagonist in clinical development as one of a new class of antiretrovirals targeting human immunodeficiency virus type 1 (HIV-1) coreceptor binding. We investigated the mechanism of HIV resistance to maraviroc by using in vitro sequential passage and site-directed mutagenesis. Serial passage through increasing maraviroc concentrations failed to select maraviroc-resistant variants from some laboratory-adapted and clinical isolates of HIV-1. However, high-level resistance to maraviroc was selected from three of six primary isolates passaged in peripheral blood lymphocytes (PBL). The SF162 strain acquired resistance to maraviroc in both treated and control cultures; all resistant variants were able to use CXCR4 as a coreceptor. In contrast, maraviroc-resistant virus derived from isolates CC1/85 and RU570 remained CCR5 tropic, as evidenced by susceptibility to the CCR5 antagonist SCH-C, resistance to the CXCR4 antagonist AMD3100, and an inability to replicate in CCR5 ⌬32/⌬32 PBL. Strain-specific mutations were identified in the V3 loop of maraviroc-resistant CC1/85 and RU570. The envelope-encoding region of maraviroc-resistant CC1/85 was inserted into an NL4-3 background. This recombinant virus was completely resistant to maraviroc but retained susceptibility to aplaviroc. Reverse mutation of gp120 residues 316 and 323 in the V3 loop (numbering from HXB2) to their original sequence restored wild-type susceptibility to maraviroc, while reversion of either mutation resulted in a partially sensitive virus with reduced maximal inhibition (plateau). The plateaus are consistent with the virus having acquired the ability to utilize maraviroc-bound receptor for entry. This hypothesis was further corroborated by the observation that a high concentration of maraviroc blocks the activity of aplaviroc against maraviroc-resistant virus.

Section: Discussionmentioning

confidence: 99%

Reduced Maximal Inhibition in Phenotypic Susceptibility Assays Indicates that Viral Strains Resistant to the CCR5 Antagonist Maraviroc Utilize Inhibitor-Bound Receptor for Entry

Westby

Smith‐Burchnell

Mori

et al. 2007

324

480

“…There are several variables that affect the potency of these agents, including the impressive genetic variability of Env (15). In general, the potencies with which entry inhibitors fully suppress infection of primary virus strains vary to a greater extent than do those of antiviral agents that target more conserved viral proteins, such as reverse transcriptase, integrase, and protease (20,31). In addition, host cell factors also influence the efficiencies with which entry inhibitors prevent virus infection of primary cells obtained from different individuals (27,35,37).…”

mentioning

confidence: 99%

Baseline Resistance of Primary Human Immunodeficiency Virus Type 1 Strains to the CXCR4 Inhibitor AMD3100

Harrison

Lynch²,

Sierra³

et al. 2008

We screened a panel of R5X4 and X4 human immunodeficiency virus type 1 (HIV-1) strains for their sensitivities to AMD3100, a small-molecule CXCR4 antagonist that blocks HIV-1 infection via this coreceptor. While no longer under clinical development, AMD3100 is a useful tool with which to probe interactions between the viral envelope (Env) protein and CXCR4 and to identify pathways by which HIV-1 may become resistant to this class of antiviral agents. While infection by most virus strains was completely blocked by AMD3100, we identified several R5X4 and X4 isolates that exhibited plateau effects: as the AMD3100 concentration was increased, virus infection and membrane fusion diminished to variable degrees. Once saturating concentrations of AMD3100 were achieved, further inhibition was not observed, indicating a noncompetitive mode of viral resistance to the drug. The magnitude of the plateau varied depending on the virus isolate, as well as the cell type used, with considerable variation observed when primary human T cells from different human donors were used. Structure-function studies indicated that the V1/V2 region of the R5X4 HIV-1 isolate DH12 was necessary for AMD3100 resistance and could confer this property on two heterologous Env proteins. We conclude that some R5X4 and X4 HIV-1 isolates can utilize the AMD3100-bound conformation of CXCR4, with the efficiency being influenced by both viral and host factors. Baseline resistance to this CXCR4 antagonist could influence the clinical use of such compounds.

“…Studies of drug resistance have mainly focused on HIV-1 subtype B, which is dominant in developed countries (26). A paucity of data on the emergence of antiretroviral (ARV) drug resistance in individuals or populations infected with other subtypes (e.g., A, C, D, and CRF01) likely is attributable to limited access to ARV drug treatment in developing countries (1, 2, 13, 15, 30-32, 39, 47, 53).…”

mentioning

confidence: 99%

Characterization of a Subtype D Human Immunodeficiency Virus Type 1 Isolate That Was Obtained from an Untreated Individual and That Is Highly Resistant to Nonnucleoside Reverse Transcriptase Inhibitors

Gao

Paxinos

Galovich

et al. 2004

Human immunodeficiency virus type 1 (HIV-1) isolates derived from HIV-infected, treatment-naive Ugandan infants were propagated and tested for sensitivity to antiretroviral (ARV) drugs. Although most subtype A and D isolates displayed inhibition profiles similar to those of subtype B strains, a subtype D isolate identified as D14-UG displayed high-level resistance to nevirapine in peripheral blood mononuclear cell cultures (>2,000-fold) and in MT4 cell cultures (ϳ800-fold) but weaker resistance to delavirdine (ϳ13-fold) and efavirenz (ϳ8-fold) in MT4 cell cultures. To investigate the possible mechanism for this resistance to nonnucleoside reverse transcriptase (RT) inhibitors (NNRTIs), the RT coding region in pol was sequenced and compared to the consensus RT sequence of NNRTI-resistant and NNRTI-sensitive subtype A, B, and D HIV-1 isolates. D14-UG did not contain the classic amino acid substitutions conferring NNRTI resistance (e.g., Y181C, K103N, and G190A) but did have some putative sites associated with drug resistance, I135L, T139V, and V245T. Wild-type and mutated protease-RT genes from D14-UG and an NNRTI-sensitive subtype D isolate from Uganda (D13-UG) were cloned into pNL4-3 to produce recombinant viruses and to determine the effects of the mutations on susceptibility to ARV drugs, specifically, NNRTIs. The results showed that I135L and/or V245T mutations can confer high-level resistance to nevirapine and delavirdine as well as low level crossresistance to efavirenz. Finally, ex vivo fitness analyses suggested that NNRTI-resistant sites 135L and 245T in wild-type isolate D14-UG may reduce RT fitness but do not have an impact on the fitness of the primary HIV-1 isolate.Current drugs effective at inhibiting human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) are classified as nucleoside RT inhibitors (NRTIs) and nonnucleoside RT inhibitors (NNRTIs) (3,19). NRTIs interfere with enzyme activity following conversion to the triphosphate forms and incorporation into the growing DNA strand, which causes premature chain termination (4,8). In contrast, NNRTIs are noncompetitive inhibitors which bind a hydrophobic pocket adjacent to the polymerase active site, causing an allosteric change which effectively inhibits DNA polymerization (9). One of the impediments to the frequent use of NNRTIs in combination with at least two NRTIs is the rapid emergence of resistance.Studies of drug resistance have mainly focused on HIV-1 subtype B, which is dominant in developed countries (26). A paucity of data on the emergence of antiretroviral (ARV) drug resistance in individuals or populations infected with other subtypes (e.g., A, C, D, and CRF01) likely is attributable to limited access to ARV drug treatment in developing countries (1, 2, 13, 15, 30-32, 39, 47, 53). However, the rapid implementation of new ARV drug treatment programs in these regions likely will precede thorough investigations of ARV drug resistance in non-clade B HIV-1 isolates. Interestingly, nevirapine, as opposed to the more expensive p...