Dolutegravir Monotherapy of Simian Immunodeficiency Virus-Infected Macaques Selects for Several Patterns of Resistance Mutations with Variable Virological Outcomes

Abstract

Drug resistance remains a major concern for human immunodeficiency virus (HIV) treatment. To date, very few resistance mutations have emerged in first-line combination therapy that includes the integrase strand transfer inhibitor (INSTI) dolutegravir (DTG). In vitro, DTG selects for several primary mutations that induce low-level DTG resistance; secondary mutations, while increasing the level of resistance, however, further impair replication fitness, which raised the idea that DTG monotherapy may be feasible. The simian immunodeficiency virus (SIV) rhesus macaque model of HIV infection can be useful to explore this concept. Nine macaques were infected with virulent SIVmac251 and started on DTG monotherapy during either acute (n = 2) or chronic infection (n = 7). Within 4 weeks of treatment, all animals demonstrated a reduction in viremia of 0.8 to 3.5 log RNA copies/ml plasma. Continued treatment led to overall sustained benefits, but the outcome after 10 to 50 weeks of treatment was highly variable and ranged from viral rebound to near pretreatment levels to sustained suppression, with viremia being 0.5 to 5 logs lower than expected based on pretreatment viremia. A variety of mutations previously described to confer low-level resistance of HIV-1 to DTG or other INSTI were detected, and these were sometimes followed by mutations believed to be compensatory. Some mutations, such as G118R, previously shown to severely impair the replication capacity in vitro, were associated with more sustained virological and immunological benefits of continued DTG therapy, while other mutations, such as E92Q and G140A/Q148K, were associated with more variable outcomes. The observed variability of the outcomes in macaques warrants avoidance of DTG monotherapy in HIV-infected people. IMPORTANCE A growing number of anti-HIV drug combinations are effective in suppressing virus replication in HIV-infected persons. However, to reduce their cost and risk for toxicity, there is considerable interest in simplifying drug regimens. A major concern with single-drug regimens is the emergence of drug-resistant viral mutants. It has been speculated that DTG monotherapy may be a feasible option, because DTG may have a higher genetic barrier for the development of drug resistance than other commonly used antiretrovirals. To explore treatment initiation with DTG monotherapy, we started SIV-infected macaques on DTG during either acute or chronic infection. Although DTG initially reduced virus replication, continued treatment led to the emergence of a variety of viral mutations previously described to confer low-level resistance of HIV-1 to DTG, and this was associated with variable clinical outcomes. This unpredictability of mutational pathways and outcomes warns against using DTG monotherapy as initial treatment for HIV-infected people.

Insertion as a Resistance Mechanism Against Integrase Inhibitors in Several Retroviruses

“…In agreement with this hypothesis, all insertions reported to date also contained the small amino acid glycine (G), which could contribute to loop flexibility. Importantly, in our study, insertions could be found in circulating strains as well as proviruses, indicating that both replicative capacity and integration were conserved [5]. The replicative competence of retroviruses carrying integrase insertions is now confirmed by Le Hingrat et al's report of evolution from 2 to 5 amino acid insertions in 1 patient [1].…”

“…The insertion consisted of 5 amino acids after position 232 in the integrase of SIVmac251, and could not be introduced in either SIVmac239 or HIV-1 without severely impairing fitness [4]. More recently, we also reported the frequent emergence of various 5 or 6 amino acid insertions in the SIVmac251 integrase in rhesus macaques treated with dolutegravir monotherapy [5]. Integrase insertions in this setting were heterogeneous in sequence, but all contained 2 positively charged amino acids, and all were found in the immediate vicinity of arginine (R) 231, a residue that was shown by cryogenic electron microscopy (cryo-EM) to be the only one outside of integrase catalytic domain to interact with host target DNA strongly [6].…”

“…The G625R mutation identified by Das et al is yet neither a validated nor a candidate marker for artemisinin partial resistance [4]. In vitro resistance assessed by ring-stage survival assay (RSA) 0-3h is defined by persistence of a parasite survival rate >1% [2] (and not 10% as used in a previous version of the article and in another publication of this study [5].…”

Mutations in the HIV-1 envelope glycoprotein can broadly rescue blocks at multiple steps in the virus replication cycle

“…However, to our knowledge, we present a unique instance of de novo selection of Env mutations that confer resistance to DTG in vitro. Ongoing studies should determine whether the Env mutations described here confer resistance to other classes of ARVs, and whether mutations in Env can contribute to escape from ARV therapy in infected individuals (86). The results of this work will provide fundamental insights into mechanisms of drug resistance and viral spread in vivo.…”

Antiretroviral therapy does not reduce tuberculosis reactivation in a tuberculosis-HIV coinfection model

“…These antiretroviral drugs were administered in a formulation of a 3-drug cocktail dissolved in the vehicle kleptose following previously published doses for each drug. Each milliliter of formulation contained the reverse transcriptase inhibitors PMPA (20 mg/mL) (50-52) and FTC (30 mg/mL) (53) and the integrase inhibitor DTG (2.5 mg/mL) (54,55).…”