Publications

BACKGROUND

There is intense interest in the role of programmed death 1 (PD-1) in causing persistent T-cell dysfunction in HIV infection. However, the impact of HIV infection and antiretroviral treatment (ART) on the expression of PD-1 on T cells is still poorly defined.

METHODS

PD-1 was measured longitudinally in a cohort of recently HIV-infected individuals (n = 121) who started ART early (<6 months after infection) vs. later (≥2 years after infection). PD-1 was also measured cross-sectionally in a diverse cohort of chronically HIV-infected adults (n = 206).

RESULTS

PD-1 expression levels were high on CD8⁺ T cells during early HIV infection. PD-1 levels increased on both CD4⁺ and CD8⁺ T cells populations in those who delayed therapy (11 and 10%/year, respectively). PD-1 levels declined and were similar in those treated early vs. late after 1 year of ART. In both cohorts, PD-1 expression on CD4⁺ T cells was associated with CD4⁺ T-cell activation (CD38⁺HLA-DR⁺) and inversely with CD4⁺ cell count. In contrast, PD-1 expression on CD8⁺ T cells was most strongly associated with CD8⁺ T-cell activation and with plasma viral load in viremic individuals.

CONCLUSION

Across two large cohorts of untreated and treated individuals, we found consistent associations between HIV RNA levels, CD8⁺ T-cell activation and PD-1 expression on CD8⁺ T cells. In contrast, CD4⁺ T-cell counts and CD4⁺ T-cell activation were more consistent correlates of PD-1 expression on CD4⁺ T cells. PD-1 expression appears to be driven by both direct antigen and homeostatic pathways.

Few reports have examined the impact of HIV-1 transmitted drug resistance (TDR) in resource-limited settings where there are fewer regimen choices and limited pretherapy/posttherapy resistance testing. In this study, we examined TDR prevalence in Kampala and Mbarara, Uganda and assessed its virologic consequences after antiretroviral therapy initiation. We sequenced the HIV-1 protease/reverse transcriptase from n=81 and n=491 treatment-naive participants of the Uganda AIDS Rural Treatment Outcomes (UARTO) pilot study in Kampala (AMU 2002-2004) and main cohort in Mbarara (MBA 2005-2010). TDR-associated mutations were defined by the WHO 2009 surveillance mutation list. Posttreatment viral load data were available for both populations. Overall TDR prevalence was 7% (Kampala) and 3% (Mbarara) with no significant time trend. There was a slight but statistically nonsignificant trend indicating that the presence of TDR was associated with a worse treatment outcome. Virologic suppression (≤400 copies/ml within 6 months posttherapy initiation) was achieved in 87% and 96% of participants with wildtype viruses versus 67% and 83% of participants with TDR (AMU, MBA p=0.2 and 0.1); time to suppression (log-rank p=0.3 and p=0.05). Overall, 85% and 96% of study participants achieved suppression regardless of TDR status. Surprisingly, among the TDR cases, approximately half still achieved suppression; the presence of pretherapy K103N while on nevirapine and fewer active drugs in the first regimen were most often observed with failures. The majority of patients benefited from the local HIV care system even without resistance monitoring. Overall, TDR prevalence was relatively low and its presence did not always imply treatment failure.

We conducted a longitudinal study of tobacco use among adults initiating antiretroviral therapy (ART) in Mbarara, Uganda where 11 % of men and 3 % of women use tobacco according to the 2011 Demographic and Health Survey. In a prospective cohort, self-reported tobacco use was assessed before starting ART and reassessed every 3-4 months. Plasma cotinine, a nicotine metabolite, was measured in a subset of adults pre-ART to verify self-report. Among 496 subjects, 50 (10 %) reported current tobacco use (20 % of men, 6 % of women). Most (53 %) adults with elevated cotinine levels (>15 ng/mL) reported no tobacco use. By 6 months after ART initiation, 33 % of tobacco users had quit (95 % CI 20-46 %). By 5 years, 64 % quit (95 % CI 47-77 %). Self-reported tobacco use among rural Ugandans starting ART was twice as common as among the local background population and use may be underreported. ART initiation could be an opportunity for tobacco cessation interventions.

PURPOSE OF REVIEW

It is now widely accepted that HIV-infected individuals remain at a higher risk for mortality and age-related morbidities than the general population, but several unresolved issues need to be addressed by the research community in the coming years to further improve the health of HIV-infected individuals in the modern treatment era.

RECENT FINDINGS

Although recent studies have helped to better define the contribution of HIV to life expectancy and morbidity in the modern antiretroviral therapy (ART) era, questions remain about the generalizability of these findings to a future HIV-infected population that is expected to be much older. Furthermore, although a consensus has emerged that the persistent inflammatory state contributes to morbidity and mortality in this setting, the relative contributions of this process, health-related behaviours, comorbidities and medication toxicities remain incompletely understood. Lastly, significant uncertainty remains over the root causes of the persistent inflammatory state, the specific immunologic pathways to target with interventions and the most appropriate biomarkers to use for surrogate outcomes in pilot trials of immune-based interventions.

SUMMARY

Each of these issues will be addressed in this review, highlighting recently published and presented studies that inform the discussion, and recommendations will be made for prioritizing the future research agenda.