Conslusions
In this retrospective multicentric study of PWH on ART (one-third on first-line therapy and two-thirds ART-experienced), neither PIs use, nor the type of ART regimen were associated with differential odds of CVE after accounting for historical drug resistance genotype. Conversely, an almost 4-fold higher odds of CVE was found in participants with plasma RAMs in HIV-1 RT gene. In line with this finding, unadjusted CPE scores did not associate with CVE, while lower HGRT-adjusted CPE scores associated with increased risk of escape. All these findings were also confirmed by sensitivity analyses in participants with plasma suppression.
In anatomical reservoirs where drugs reach low inhibitory quotients, partially resistant viruses may replicate and favor the selection of further RAMs, eventually leading to CVE. PIs penetrate the CNS less effectively than other ARVs classes17–21. Therefore, RAMs in the RT gene may have exposed patients to functional monotherapy leading to loss of virological control in CNS. In our study, CPE values were similar between participants with and without CVE, suggesting that unadjusted values alone may not discriminate those at risk. However, after RAMs were factored into CPE values, median adjusted CPE scores in CSF were lower in participants with CVE, suggesting that accumulation of RAMs combined with the reduced penetration of ARVs within CNS may lead to local ineffective viral control. These results are not in contradiction with previous larger and longitudinal cohorts reporting association between PI use and CVE, but may be complimentary to the previous lack of genotype resistance assessment12,14,15,29. Indeed, when GRT was available, CVE has been associated with HIV-1 mutant viruses harboring M184 along with other major RAMs that conferred resistance to at least one ARV composing ART at the time of CVE development12.
PIs use was not associated with CVE. Compared to countries where PIs use has been repeatedly associated with CVE, in Europe PIs have been more commonly used as third companion drug also in first-line ART regimens, and therefore larger proportion of ART-naïve patients starting on PIs and individuals proactively switching to PI-based regimen have been enrolled in our study population. This could explain why no strong association between PIs use and CVE has been observed in our sample compared to setting where PIs were reserved to patients with virological failure12,14,15. Indeed, in patients treated with NNRTIs plus non-active companion drugs or with dolutegravir monotherapy, systemic virological failure has been quickly reported31, while in patients on PI-based functional or actual monotherapy, low-level HIV replication in the CSF may occur despite peripheral viral suppression potentially leading to more frequent detections of CVE32–35.
To the best of our knowledge, this study describes the largest sample of data on genotype resistance testing in reverse transcriptase and protease genes linked to the risk of CVE. It is also the largest dataset that assessed factors associated with primary CVE in a clinical setting that adhered to European guidelines for the treatment of HIV infection during the last two decades. While many ART regimens included in this study can be considered currently dismissed by several countries, they are still first-line regimens in many resource-limited countries. Our data should also be useful as framework to understand CVE risk in newer ARVs combinations presenting low CNS penetration as well as to evaluate the efficacy of dual regimens in hard-to-reach compartments. Dual regimens per se may be safe and effective in controlling CNS HIV infection36, but require proper combinations accounting for virus and patients characteristics, that include historical genotype. Furthermore, while it could be debatable any ART change in CVE cases with no RAMs, we observed that most CVE cases occurred in the presence of RAMs affecting at least one of the antiretrovirals composing the current ART regimen; this finding should prompt to an intensification or change of the current ART regimen regardless of concomitant neurological signs or symptoms and of alterations in CSF analysis or in brain imaging. Based on these findings, a prompt reassessment of the HGRT and of potentially newly selected RAMs in both plasma and CSF seems also highly recommended in any case of symptomatic or asymptomatic CVE. The lack of a longitudinal design indeed does not allow us to evaluate how many of the asymptomatic cases can evolve into symptomatic CVE with no change in the ART regimen.
This study has several limitations, including the retrospective design, the long period of inclusion potentially introducing heterogeneity of regimens and clinical management, potential selection bias due to 16.7% of participants undergoing LP for research purposes, and the lack of a complete GRT assessment in CSF. The lack of data on timing of infection limited the possibility to confirm this variable as relevant for CVE and may explain why other time variables such as age or ART duration were found linked with escape. The lack of an assessment of participants ART adherence may limit the causality hypothesis; individuals with poor adherence could experience more episodes of virological failures leading to RAMs and thereby the association between CVE and RT mutations could be mediated by the lack of adherence rather than the mutations themselves. Nevertheless, our findings were confirmed in sensitivity analyses restricted to participants with plasma suppression, where adherence should be deemed of substantial degree to reach such plasma control. Lastly, we could not exclude that some CVE cases were secondary to rare infections or inflammatory processes that were not routinely detected. In this regard, tailored studies are warranted to better identifying other mechanisms underlying the rarer cases of CVE (<10%) occurring in the absence of RAMs.
In conclusion, CVE was not associated with PIs use nor with any other type of ART regimen or ARV class. Viruses harboring mutations may favor CVE and the impact of single drug classes such as PIs may lose significance when adjusted for the presence and effect of specific RAMs as most CVE cases were explained by functional dual or mono-therapies due to the presence of archived RAMs in the RT gene.