Skip to main content

Systemic inflammation and residual viraemia in HIV-positive adults on protease inhibitor monotherapy: a cross-sectional study



Increased levels of markers of systemic inflammation have been associated with serious non-AIDS events even in patients on fully suppressive antiretroviral therapy. We explored residual viremia and systemic inflammation markers in patients effectively treated with ritonavir-boosted protease inhibitor monotherapy (PImono).


HIV-infected adults with persistent HIV-RNA <50 copies/ml and treated with either a) PImono or b) standard triple-drug cART were recruited for this cross-sectional, exploratory study. Plasma samples were tested for high-sensitivity CRP (hsCRP), Serum Amyloid A (SAA), soluble CD14, IL-6, IL-8 and Cytochrome C. HIV-RNA was measured by real-time PCR (detection limit of 10 copies/ml).


81 patients were recruited (31% on PImono). Two out of 25 (8%) and 3 of 56 (5.4%) patients from the PImono and cART groups respectively had detectable HIV-RNA. Significant correlation between SAA and hsCRP was observed (0.804). No difference between groups was found on prevalence of hsCRP >3 mg/l (21% vs 20% in the PImono and cART groups respectively; p = 0.577) or SAA >6.4 mg/l (38% vs 22% in the PImono and cART groups respectively; P = 0.172). In a univariate analysis IL6 and IL8 levels were associated with SAA >6.4 mg/l (OR = 1.74 and 1.46; 95% CI = 1.00 – 3.03 and 1.06 – 2.01; p = 0.051 and 0.02 respectively) and hsCRP >3 mg/l in (OR = 2.00 and 1.37; 95% CI = 1.09 – 3.69 and 1.02 – 1.85; p = 0.026 and 0.039 respectively).


We found no evidence of increased levels of inflammatory biomarkers or higher prevalence of residual viraemia in patients effectively suppressed on PImono as compared with patients on standard cART.

Peer Review reports


Persistent systemic inflammation has been associated with an increased risk of serious non-AIDS defining events, such as cardiovascular disease (CVD), in HIV-positive adults despite effective treatment with antiretroviral therapy (ART) [1,2]. Standard ART regimens usually include three different drugs from at least two drug classes. However, ART simplification strategies have been proposed to reduce long-term toxicity, cost and possible pharmacokinetic interactions, particularly in an aging population that is likely to be prescribed multiple medications [3].

Protease inhibitor monotherapy (PImono) has been explored as treatment simplification strategy in a number of randomised clinical trials [4-6]. However, in clinical practice it seems like patients on PImono show a viral load rebound rate higher than what would be expected in combination ART (cART) treated patients and this has been suggested to be due to persistent residual viraemia below the detection limit of currently used assays [5]. Increased levels of systemic inflammation markers have been reported in patients with HIV low-level viraemia and have been associated with a number of serious non-AIDS defining complications. High-sensitivity C-reactive protein (hsCRP) and Interleukins 6 and 10 (IL-6, IL-10) have been reported as predictors of serious non-AIDS defining events including CVD, cancer and overall mortality [7-9]. Serum Amyloid A (SAA) is a lipoprotein secreted during the acute phase of inflammation which has been considered more sensitive than CRP in some rheumatologic conditions, although the magnitude of increase is often be greater than that of CRP [10,11]. In acute viral infections SAA levels appear to increase more than CRP [12,13].

We have performed a cross-sectional, exploratory study comparing residual viraemia and systemic inflammatory markers in patients free of major co-morbidities and effectively suppressed on either standard cART or PI monotherapy. We also aimed to explore the level of concordance between SAA and hsCRP in the study population.


Study population

HIV-positive adults on ART for at least 48 weeks and with documented HIV-RNA <50 copies/ml for at least 24 weeks, and no change in their ART over the same period immediately prior to enrolment were recruited for this cross-sectional study at a single site in London. At enrolment, patients were taking either a) a ritonavir-boosted protease inhibitor as a single agent (PImono) or b) cART comprising two NRTI and a third anti-retroviral agent and should have had ≥200 CD4 cell/mm3. Because the study aimed to investigate markers of systemic inflammation and immune activation in patients free of major co-morbidities likely to impact on these, patients were considered not eligible if they had a previous history of any autoimmune disease (e.g. systemic lupus erythematous, Addison’s disease, Graves’ disease, multiple sclerosis, myasthenia gravis, rheumatic and reactive arthritis, etc.), CVD (defined as previous myocardial infraction, stroke or coronary revascularisation), treatment for any acute opportunistic infection within three months prior to enrolment, any serious bacterial infection (e.g. pneumonia, meningitis, septicaemia, etc.) in the two months prior to enrolment, any acute infection with fever and systemic symptoms within the last 72 hours before enrolment, any vaccination in the two months prior to enrolment or if they had used systemic corticosteroids or any other immune-modulatory drug within the 12 months prior to enrolment. Patients who were hepatitis B surface antigen (HBsAg) or hepatitis C RNA positive were also excluded. Clinical and epidemiological data, including demographics, date of first HIV antibody positive result, ART history and relevant past medical history was obtained from participants medical records.

Informed consent was obtained from all study participants. The study was reviewed by the National Ethics Research Service Committee London – Queen’s Square (Ref. 11/LO/1102) and the North Central London Research Consortium R&D Office.


Plasma samples were tested for hsCRP (COBAS MIRA; Roche Diagnostics GmbH), SAA (BNII auto-analizer; Dade Behring, Marburg, Germany), sCD14, ILs1b, 6, 8, 10 and 12p70, and TNF-α (BD Biosciences CBA, San Jose, CA, USA) and Cytochrome C (R&D Quantikine, MN, USA). HIV-RNA was measured by real-time PCR with a detection limit of 10 copies/ml (in-house developed assay by UCLH virology department; CPA accredited). Samples were stored at −80°C and tested at the end of the study period in a single batch.

Statistical analysis

Continuous data were summarised and compared using the Mann-Witney test or grouped into categories where Fischer’s exact test was used. Significance level set as p < 0.05 in all analyses. Clinically significant elevation of hsCRP and SAA were defined as >3 and 6.4 mg/l respectively. Simple linear regression was used to explore correlation between hsCRP and SAA levels. Associations with elevated hsCRP and SAA were explored using logistic regression.


A total of 81 treated HIV-infected patients were recruited of whom, 25 (31%) were being treated with PImono. Most of patients on cART were receiving abacavir-containing (96%) and PI-based (57%) combinations. Patients on PImono were mainly receiving DRV/RTV (80%) (Table 1). Median age was 46.2 years (Inter quartile range (IQR) 42.2 – 52.7) and there was no difference between study groups on age distribution. There were more female patients in the cART group (26.8%) compared to the PImono group (4%; p = 0.017). Patients on cART were known with HIV infection for slightly longer (median 11.8; IQR = 8.2-16.7 years) than patients on PImono (median 9.6; IQR = 7.3- 14.3 years) (p = 0.091). Median CD4 count was similar between study groups (550 cell/ml; IQR = 460-740 and 615 cell/ml; IQR = 470-770 for the PImono and the cART groups respectively; p = 0.210). All study participants had HIV-RNA <50 copies/ml at entry. Two out of 25 (8%) and 3 of 56 (5.4%) patients from the PImono and cART groups respectively had residual viraemia (i.e. HIV-RNA 10–50 copies/ml) (p = 0.648). Two of the patients with detectable viraemia were being treated with ritonavir-boosted darunavir monotherapy whereas the other three were on abacavir, lamivudine and either efavirenz or nevirapine.

Table 1 Patients characteristics

There was no difference in the distribution of hsCRP and SAA levels between the study groups (Table 2). Overall, 20% of participants had hsCRP >3 mg/l, but no difference between groups was found (21% vs 20% in the PImono and cART groups respectively; p = 0.577). Similarly, there was no difference between groups in the proportion of participants with SAA >6.4 mg/l (upper limit of normal range) (38% vs 22% in the PImono and cART groups respectively; p = 0.172). We found no difference on the proportion of patients with elevated hsCRP or SAA between patients on PImono or NNRTI-based cART (p = 0.702 and 0.096 respectively). Other markers of inflammation and mitochondrial function did not differ between groups as shown in Table 2.

Table 2 Systemic inflammation and mitochondrial dysfunction markers

A significant correlation between SAA and hsCRP was observed (0.804) with a regression coefficient of 3.507 (95% CI 2.92-4.20; p < 0.001) suggesting an expected increment of 3 mg/l in SAA for each unit increment in hsCRP. A total of 14 participants had hsCRP >3 mg/l and SAA >6.4 mg/l, whereas seven of the 21 patients with SAA >6.4 mg/l (33%) had hsCRP <3 mg/l. In a logistic regression analysis IL6 and IL8 levels were associated with SAA >6.4 mg/l (OR = 1.74 and 1.46; 95% CI 1.00-3.03 and 1.06-2.01; p = 0.051 and 0.02 respectively) whereas younger age and female gender showed an inverse association with SAA >6.4 mg/l (OR = 0.94 and 0.37; 95% CI 0.88-1.00 and 0.12-1.16 respectively). In a multivariate model only age remained independently associated with SAA >6.4 mg/l (OR = 0.92; 95% CI 0.86-0.99; p = 0.038). IL6 and IL8 levels were also associated with hsCRP >3 mg/l in univariate analysis (OR = 2.00 and 1.37; 95% CI 1.09-3.69 and 1.02-1.85; p = 0.026 and 0.039 respectively).


We did not find any evidence of increased levels of inflammatory biomarkers or higher prevalence of residual viraemia in patients with HIV viral loads <50 copies/ml while treated with PImono as compared with patients on cART which is consistent with previous studies where PI monotherapy has been compared to PI-based cART [14,15]. However, Torres et al. have reported higher monocyte activation, inflammation and residual viraemia in patients on PI monotherapy compared to PI-based cART [16]. In our study the majority of subjects showed low plasma levels of hsCRP and SAA as expected in well suppressed patients with no major co-morbidities. However, the levels of CRP and IL6 reported in previous studies with less stringent exclusion criteria were much higher and the proportion of participants with known co-morbidities such as hepatitis C was about 20% [15,16]. Increased monocyte activation, systemic inflammation and immune activation markers have all been associated with a number of inflammatory conditions, including HCV infection [17], and some of these could have been contributed to partially explain controversial results.

Residual viraemia has been observed more frequently in patients on PI-based compared to NNRTI-based cART [18]. However, in our study 40% of the control group were on NNRT-base cART and we still found no difference in residual viraemia between groups. In randomised trials PI monotherapy has been associated with a higher viral load rebound rate compared to cART but ours and previous results appear to suggest that persistent residual viraemia may not be the mechanism for viral load rebounds in patients treated with PI as single agent [4-6].

Because the detection limit of the PCR assay we used, we cannot exclude the possibility of differences in very low level viraemia (i.e. <10 copies/ml) between groups, but if there was any, that does not appeared to have any impact on systemic inflammation. However, we found that 26% of the study population had SAA levels >6.4 mg/l, which are considered elevated, and have been associated with active inflammatory conditions [19]. Furthermore, clinically significant elevations in SAA were associated with IL-6 and IL-8 levels and these have been previously reported to be associated with serious non-AIDS events [20]. Further investigation of SAA as a marker of systemic inflammation in HIV-infected populations may be of interest.

Mitochondrial dysfunction may lead to systemic inflammation and has been reported as an important mechanism in acute response to trauma [21]. NRTIs can induce mitochondrial dysfunction and this could be a mechanism to trigger an inflammatory response locally or systemically. Cytochrome-C (Cyt-C) is a marker of mitochondrial function and integrity and has been associated with inflammation and apoptosis [22] but, in our study, plasma levels of Cyt-C were not different between groups. Most of participants in the cART group (96%) were taking abacavir-based ART which is less likely to cause mitochondrial impairment than other NRTI although it has been associated with an excess risk for cardiovascular events [23,24].

Our study has limitations related to the study design and the small size of the study population. In addition, the study population included a selected group of patients and treatment allocation was not randomised. However, we believe ours is the first study looking at the question of systemic inflammation and low-level viraemia in patients on PI monotherapy compared to PI and NNRTI-based cART in a population free of serious co-morbidities, meaning that the effect of any concomitant morbidity on systemic inflammation can be ruled out.


Our data add further evidence suggesting that patients with persistent HIV-RNA <50 copies/ml while on PI monotherapy are not more likely to have increased levels of systemic inflammation markers circulating in plasma or residual viraemia than patients on standard cART.



Anti-retroviral therapy/Combination Anti-retroviral therapy


C-Reactive Protein/High-sensitivity C-Reactive Protein


Cardiovascular disease






Nucleoside reverse transcriptase inhibitor/Non-nucleoside reverse transcriptase inhibitor


Protease Inhibitor/Protease Inhibitor monotherapy


Serum Amyloid A


  1. Worm SW, Hsue P. Role of biomarkers in predicting CVD risk in the setting of HIV infection? Curr Opin HIV AIDS. 2010;5(6):467–72. Epub 2010/10/28.

    Article  PubMed  Google Scholar 

  2. Tien PC, Choi AI, Zolopa AR, Benson C, Tracy R, Scherzer R, et al. Inflammation and mortality in HIV-infected adults: analysis of the FRAM study cohort. J Acquir Immune Defic Syndr. 2010;55(3):316–22. Epub 2010/06/29.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  3. Nachega JB, Mugavero MJ, Zeier M, Vitoria M, Gallant JE. Treatment simplification in HIV-infected adults as a strategy to prevent toxicity, improve adherence, quality of life and decrease healthcare costs. Patient Preference Adherence. 2011;5:357–67. Epub 2011/08/17.

    Article  PubMed  PubMed Central  Google Scholar 

  4. Arribas JR, Horban A, Gerstoft J, Fatkenheuer G, Nelson M, Clumeck N, et al. The MONET trial: darunavir/ritonavir with or without nucleoside analogues, for patients with HIV RNA below 50 copies/ml. AIDS. 2010;24(2):223–30. Epub 2009/12/17.

    Article  CAS  PubMed  Google Scholar 

  5. Katlama C, Valantin MA, Algarte-Genin M, Duvivier C, Lambert-Niclot S, Girard PM, et al. Efficacy of darunavir/ritonavir maintenance monotherapy in patients with HIV-1 viral suppression: a randomized open-label, noninferiority trial, MONOI-ANRS 136. AIDS. 2010;24(15):2365–74. Epub 2010/08/31.

    CAS  PubMed  Google Scholar 

  6. Pulido F, Delgado R, Perez-Valero I, Gonzalez-Garcia J, Miralles P, Arranz A, et al. Long-term (4 years) efficacy of lopinavir/ritonavir monotherapy for maintenance of HIV suppression. J Antimicrobial Chemotherapy. 2008;61(6):1359–61. Epub 2008/03/18.

    Article  CAS  Google Scholar 

  7. Bastard JP, Soulie C, Fellahi S, Haim-Boukobza S, Simon A, Katlama C, et al. Circulating interleukin-6 levels correlate with residual HIV viraemia and markers of immune dysfunction in treatment-controlled HIV-infected patients. Antivir Ther. 2012;17(5):915–9. Epub 2012/03/23.

    Article  CAS  PubMed  Google Scholar 

  8. Reus S, Portilla J, Sanchez-Paya J, Giner L, Frances R, Such J, et al. Low-level HIV viremia is associated with microbial translocation and inflammation. J Acquir Immune Defic Syndr. 2013;62(2):129–34. Epub 2012/09/29.

    Article  PubMed  Google Scholar 

  9. Borges AH, Silverberg MJ, Wentworth D, Grulich AE, Fatkenheuer G, Mitsuyasu R, et al. Predicting risk of cancer during HIV infection: the role of inflammatory and coagulation biomarkers. AIDS. 2013;27(9):1433–41. Epub 2013/08/16.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  10. Cantarini L, Giani T, Fioravanti A, Iacoponi F, Simonini G, Pagnini I, et al. Serum amyloid A circulating levels and disease activity in patients with juvenile idiopathic arthritis. Yonsei Med J. 2012;53(5):1045–8. Epub 2012/08/08.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  11. King VL, Thompson J, Tannock LR. Serum amyloid A in atherosclerosis. Curr Opin Lipidol. 2011;22(4):302–7. Epub 2011/07/08.

    Article  CAS  PubMed  Google Scholar 

  12. Miwata H, Yamada T, Okada M, Kudo T, Kimura H, Morishima T. Serum amyloid A protein in acute viral infections. Arch Dis Child. 1993;68(2):210–4. Epub 1993/02/01.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  13. Shimetani N, Shimetani K, Mori M. Clinical evaluation of the measurement of serum procalcitonin: comparative study of procalcitonin and serum amyloid A protein in patients with high and low concentrations of serum C-reactive protein. Scand J Clin Lab Invest. 2004;64(5):469–74. Epub 2004/07/28.

    Article  CAS  PubMed  Google Scholar 

  14. McKinnon JE, Arribas JR, Pulido F, Delgado R, Mellors JW. The level of persistent HIV viremia does not increase after successful simplification of maintenance therapy to lopinavir/ritonavir alone. AIDS. 2006;20(18):2331–5. Epub 2006/11/23.

    Article  CAS  PubMed  Google Scholar 

  15. Estebanez M, Stella-Ascariz N, Mingorance J, Perez-Valero I, Bernardino JI, Zamora FX, et al. Inflammatory, procoagulant markers and HIV residual viremia in patients receiving protease inhibitor monotherapy or triple drug therapy: a cross-sectional study. BMC Infect Dis. 2014;14:379. Epub 2014/07/13.

    Article  PubMed  PubMed Central  Google Scholar 

  16. Torres B, Guardo AC, Leal L, Leon A, Lucero C, Alvarez-Martinez MJ, et al. Protease inhibitor monotherapy is associated with a higher level of monocyte activation, bacterial translocation and inflammation. J Int AIDS Soc. 2014;17:19246. Epub 2014/10/05.

    Article  PubMed  PubMed Central  Google Scholar 

  17. Armah KA, Quinn EK, Cheng DM, Tracy RP, Baker JV, Samet JH, et al. Human immunodeficiency virus, hepatitis C, and inflammatory biomarkers in individuals with alcohol problems: a cross-sectional study. BMC Infect Dis. 2013;13:399. Epub 2013/08/31.

    Article  PubMed  PubMed Central  Google Scholar 

  18. Bonora S, Nicastri E, Calcagno A, Gonzalez De Requena D, D'Ettorre G, Sarmati L, et al. Ultrasensitive assessment of residual HIV viraemia in HAART-treated patients with persistently undetectable plasma HIV-RNA: a cross-sectional evaluation. J Med Virol. 2009;81(3):400–5. Epub 2009/01/20.

    Article  CAS  PubMed  Google Scholar 

  19. Hoffman HM, Throne ML, Amar NJ, Cartwright RC, Kivitz AJ, Soo Y, et al. Long-term efficacy and safety profile of rilonacept in the treatment of cryopryin-associated periodic syndromes: results of a 72-week open-label extension study. Clin Ther. 2012;34(10):2091–103. Epub 2012/10/04.

    Article  CAS  PubMed  Google Scholar 

  20. McComsey GA, Kitch D, Sax PE, Tierney C, Jahed NC, Melbourne K, et al. Associations of inflammatory markers with AIDS and non-AIDS clinical events after initiation of antiretroviral therapy: AIDS clinical trials group A5224s, a substudy of ACTG A5202. J Acquir Immune Defic Syndr. 2014;65(2):167–74. Epub 2013/10/15.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  21. Manfredi AA, Rovere-Querini P. The mitochondrion–a Trojan horse that kicks off inflammation? N Engl J Med. 2010;362(22):2132–4. Epub 2010/06/04.

    Article  CAS  PubMed  Google Scholar 

  22. Pullerits R, Bokarewa M, Jonsson IM, Verdrengh M, Tarkowski A. Extracellular cytochrome c, a mitochondrial apoptosis-related protein, induces arthritis. Rheumatology (Oxford). 2005;44(1):32–9. Epub 2004/09/16.

    Article  CAS  Google Scholar 

  23. Birkus G, Hitchcock MJ, Cihlar T. Assessment of mitochondrial toxicity in human cells treated with tenofovir: comparison with other nucleoside reverse transcriptase inhibitors. Antimicrob Agents Chemother. 2002;46(3):716–23. Epub 2002/02/19.

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  24. Worm SW, Sabin C, Weber R, Reiss P, El-Sadr W, Dabis F, et al. Risk of myocardial infarction in patients with HIV infection exposed to specific individual antiretroviral drugs from the 3 major drug classes: the data collection on adverse events of anti-HIV drugs (D:A:D) study. J Infect Dis. 2010;201(3):318–30. Epub 2009/12/31.

    Article  CAS  PubMed  Google Scholar 

Download references


The authors express their gratitude to the patients for their participation in the study. Dr Nancy Wassef performed measurement of SAA and hsCRP at the Clinical Biochemistry Department, Royal Free Hospital, London.

Author information

Authors and Affiliations


Corresponding author

Correspondence to Alejandro Arenas-Pinto.

Additional information

Competing interests

The authors declare that they have no competing interests.

Authors’ contributions

AA-P and AM designed the study. AMc enrolled participants into the study and entered the data. DP and MM carried out the immunoassays. The manuscript was drafted by AA-P, AM and RG. All authors participated in data interpretation. All authors provided input into the report and approved the final version of the manuscript.

Rights and permissions

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.

Reprints and Permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Arenas-Pinto, A., Milinkovic, A., Peppa, D. et al. Systemic inflammation and residual viraemia in HIV-positive adults on protease inhibitor monotherapy: a cross-sectional study. BMC Infect Dis 15, 138 (2015).

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI:


  • PI monotherapy
  • Residual viraemia
  • Systemic inflammation