The Open AIDS Journal




ISSN: 1874-6136 ― Volume 13, 2019
RESEARCH ARTICLE

Correlation of High Interleukin 17A and Interleukin 6 Levels with High Virus Load Among Subtype C HIV-infected, Antiretroviral Therapy-naive Zimbabwean Patients: A Cross-sectional Study



Tommy Mlambo1, Mqondisi Tshabalala1, Tsitsi Bandason2, Kudakwashe Mhandire3, Bonface Mudenge4, Lynn Sodai Zijenah1, *
1 Department of Immunology, University of Zimbabwe College of Health Sciences, Harare, Zimbabwe
2 Biomedical Research and Training Institute, Harare, Zimbabwe
3 Department of Chemical Pathology, University of Zimbabwe College of Health Sciences, Harare, Zimbabwe
4 Flow Cytometry Laboratories and Medical Centre, Harare, Zimbabwe

Abstract

Introduction:

In response to the human immunodeficiency virus (HIV) infection, activated immune cells produce several cytokines that alter the immune response and HIV disease progression. We quantified Th1/Th2/Th17 cytokines in an antiretroviral therapy naïve (ART) cohort to investigate their correlation with traditional markers of HIV disease progression; CD4+ T-lymphocytes and virus load (VL).

Methods:

We enrolled 247 HIV-infected ART-naïve participants into the study. CD4+ T- and CD8+ T-lymphocytes were enumerated using flow cytometry. VL was quantified using the Cavidi ExaVirTM Load assay. IL-2, IL-4, IL-6, IL-10, IL-17A, TNF-α, and IFN-γ levels were quantified using the BD Cytometric Bead Array Human Th1/Th2/Th17 cytokine assay. The Kendall’s rank correlation coefficient was used to determine the correlation between log10 transformed data for cytokine levels and CD4+ T- and CD8+ T-lymphocytes, CD4/CD8 ratio, and VL.

Results:

The median CD4+ T- and CD8+ T-lymphocyte counts were 458 cells/µL (IQR:405-556) and 776 cells/µL (IQR:581-1064), respectively. The median CD4/CD8 ratio was 0.6 (IQR: 0.45-0.86). The median VL was log103.3.copies/mL (IQR:2.74-3.93). Low CD4+ T-lymphocyte counts (p=0.010) and CD4/CD8 ratio (p=0.044) were significantly correlated with high VL. There was no significant correlation of cytokine levels with CD4+ T-, CD8+ T-lymphocyte counts and CD4/CD8 ratio. However, high levels of IL-17A (p=0.012) and IL-6 (p=0.034) were significantly correlated with high VL.

Conclusion:

Our study contributes to the little knowledge available on the role of cytokine profiles in the immune response to subtype C HIV infection.

Keywords: HIV, CD4+ T- and CD8+ T-lymphocytes, CD4/CD8 ratio, Cytokines, IL-6 and IL-17A.


Article Information


Identifiers and Pagination:

Year: 2019
Volume: 13
First Page: 59
Last Page: 64
Publisher Id: TOAIDJ-13-59
DOI: 10.2174/1874613601913010059

Article History:

Received Date: 21/04/2019
Revision Received Date: 05/07/2019
Acceptance Date: 14/07/2019
Electronic publication date: 31/07/2019
Collection year: 2019

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© 2019 Mlambo et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


* Address correspondence to this author at the Department of Immunology, University of Zimbabwe College of Health Sciences, Harare, Zimbabwe; Tel: +263712631198; E-mail: lzijenah@gmail.com





1. INTRODUCTION

Cytokines are crucial to cellular communication and thus may be key elements in turning on and off the immune response [1Reuter MA, Pombo C, Betts MR. Cytokine production and dysregulation in HIV pathogenesis: Lessons for development of therapeutics and vaccines. Cytokine Growth Factor Rev 2012; 23(4-5): 181-91.
[http://dx.doi.org/10.1016/j.cytogfr.2012.05.005] [PMID: 22743036]
]. They play a critical role in immune system homeostasis.

Following HIV infection, immune cells are activated, proliferate and differentiate into effector cells which secrete various cytokines. There is an intense cytokine “storm” during acute HIV infection [2Stacey AR, Norris PJ, Qin L, et al. Induction of a striking systemic cytokine cascade prior to peak viremia in acute human immunodeficiency virus type 1 infection, in contrast to more modest and delayed responses in acute hepatitis B and C virus infections. J Virol 2009; 83(8): 3719-33.
[http://dx.doi.org/10.1128/JVI.01844-08] [PMID: 19176632]
] which might contribute to severe immune activation, rapid CD4+ T-lymphocyte depletion and increase in virus replication leading to high virus load. Although CD4+ T-lymphocytes and virus load are considered as traditional markers of HIV disease progression [3Langford SE, Ananworanich J, Cooper DA. Predictors of disease progression in HIV infection: A review. AIDS Res Ther 2007; 4: 11.
[http://dx.doi.org/10.1186/1742-6405-4-11] [PMID: 17502001]
], changes in the cytokine signature directly affect HIV disease progression [4Breen EC. Pro- and anti-inflammatory cytokines in human immunodeficiency virus infection and acquired immunodeficiency syndrome. Pharmacol Ther 2002; 95(3): 295-304.
[http://dx.doi.org/10.1016/S0163-7258(02)00263-2] [PMID: 12243 799]
]. Interleukin-6 (IL-6) has been reported to potentially increase virus replication [5Fauci AS. Host factors and the pathogenesis of HIV-induced disease. Nature 1996; 384(6609): 529-34.
[http://dx.doi.org/10.1038/384529a0] [PMID: 8955267]
, 6Poli G. European Society for Clinical Investigation. Laureate ESCI award for excellence in clinical science 1999. Cytokines and the human immunodeficiency virus: From bench to bedside. Eur J Clin Invest 1999; 29(8): 723-32.
[http://dx.doi.org/10.1046/j.1365-2362.1999.00525.x] [PMID: 10457 158]
] while interferon (IFN)-α and IFN-β inhibit HIV replication [6Poli G. European Society for Clinical Investigation. Laureate ESCI award for excellence in clinical science 1999. Cytokines and the human immunodeficiency virus: From bench to bedside. Eur J Clin Invest 1999; 29(8): 723-32.
[http://dx.doi.org/10.1046/j.1365-2362.1999.00525.x] [PMID: 10457 158]
, 7Kedzierska K, Crowe SM. Cytokines and HIV-1: Interactions and clinical implications. Antivir Chem Chemother 2001; 12(3): 133-50.
[http://dx.doi.org/10.1177/095632020101200301] [PMID: 12959322]
]. Other cytokines; Transforming Growth Factor (TGF)-β, IL-10, IL-13, and IL-4 have been shown to have both activating and inhibitory roles on HIV replication [7Kedzierska K, Crowe SM. Cytokines and HIV-1: Interactions and clinical implications. Antivir Chem Chemother 2001; 12(3): 133-50.
[http://dx.doi.org/10.1177/095632020101200301] [PMID: 12959322]
].

The balance of Th1 and Th2 cytokines has long been postulated to contribute to HIV disease progression [8Clerici M, Fusi ML, Ruzzante S, et al. Type 1 and type 2 cytokines in HIV infection - A possible role in apoptosis and disease progression. Ann Med 1997; 29(3): 185-8.
[http://dx.doi.org/10.3109/07853899708999334] [PMID: 9240622]
, 9Clerici M, Shearer GM. A TH1-->TH2 switch is a critical step in the etiology of HIV infection. Immunol Today 1993; 14(3): 107-11.
[http://dx.doi.org/10.1016/0167-5699(93)90208-3] [PMID: 8096699]
]. The Th1 to Th2 cytokine shift in HIV immunopathology remains controversial [10Gorenec L, Zidovec Lepej S, Grgic I, et al. The comparison of Th1, Th2, Th9, Th17 and Th22 cytokine profiles in acute and chronic HIV-1 infection. Microb Pathog 2016; 97: 125-30.
[http://dx.doi.org/10.1016/j.micpath.2016.06.008] [PMID: 27268396]
]. In the current study, we measured cytokine concentrations of IL-2, IL-4, IL-6, IL-10, Tumour Necrosis (TNF)-α, IFN-γ, and IL-17A to determine their correlation if any, with CD4+ T-lymphocyte counts and virus load, the traditional biomarkers of HIV disease progression. Additionally, we also investigated the correlation of CD8+ T-lymphocyte count, important in defence against intracellular pathogens and CD4/CD8 ratio with virus load and cytokine levels.

2. METHODS

2.1. Study participants

As summarised in Fig. (1), 450 potential study participants were screened based on their CD4+ T-lymphocyte count. Two hundred and forty seven (247) HIV-infected participants aged ≥ 18 years with a CD4+ T-lymphocyte count ≥ 350 cells/μL were enrolled into the “Virological and immunological investigations of HIV-infected individuals in Harare, Zimbabwe, a prospective study”, conducted at Parirenyatwa Central Hospital Opportunistic Infections Clinic, Harare, Zimbabwe between 2010 and 2013. During this period, the Zimbabwe Ministry of Health under the Zimbabwe National ART program was providing ART to HIV-infected patients with CD4+ T-lymphocyte count <350 cells/μL, based on the WHO recommendations. Prospective participants with active Tuberculosis were excluded from the study irrespective of their CD4+ T-lymphocyte count. Written informed consent was obtained from each participant. Demographic and medical history were collected at enrolment. The study was approved by the Medical Research Council of Zimbabwe (MRCZ/A/1558).

2.2. Enumeration of T-lymphocytes, CD4/CD8 Ratio and Virus Load Quantification

At enrolment, whole blood collected in EDTA tubes was used for enumeration of absolute CD4+ T- and CD8+ T-lymphocytes within 6 hours of blood collection using a Partec Cyflow counter (Cyflow, Partec, Munster, Germany) as previously described [11Manasa J, Musabaike H, Masimirembwa C, Burke E, Luthy R, Mudzori J. Evaluation of the Partec flow cytometer against the BD FACSCalibur system for monitoring immune responses of human immunodeficiency virus-infected patients in Zimbabwe. Clin Vaccine Immunol 2007; 14(3): 293-8.
[http://dx.doi.org/10.1128/CVI.00416-06] [PMID: 17267593]
, 12Zijenah LS, Kadzirange G, Madzime S, et al. Affordable flow cytometry for enumeration of absolute CD4+ T-lymphocytes to identify subtype C HIV-1 infected adults requiring antiretroviral therapy (ART) and monitoring response to ART in a resource-limited setting. J Transl Med 2006; 4: 33.
[http://dx.doi.org/10.1186/1479-5876-4-33] [PMID: 16907973]
].

The remaining whole blood was centrifuged and plasma was aliquoted and stored at -80°C until assayed. Virus load quantification was done using the Cavidi ExaVirTM Load version 3 assay (Cavidi AB, Uppsala Science Park, Sweden) following the manufacturer’s instructions [13Greengrass V, Lohman B, Morris L, et al. Assessment of the low-cost Cavidi ExaVir Load assay for monitoring HIV viral load in pediatric and adult patients. J Acquir Immune Defic Syndr 2009; 52(3): 387-90.
[http://dx.doi.org/10.1097/QAI.0b013e3181b05f62] [PMID: 19617 845]
, 14Greengrass VL, Turnbull SP, Hocking J, et al. Evaluation of a low cost reverse transcriptase assay for plasma HIV-1 viral load monitoring. Curr HIV Res 2005; 3(2): 183-90.
[http://dx.doi.org/10.2174/1570162053506955] [PMID: 15853722]
]. The assay measures the HIV reverse transcriptase activity in patient’s plasma as a marker for virus replication.

2.3. Measurements of Serum Cytokine Levels

Serum was collected at enrolment and stored at -80oC until further use. We used the BD Cytometric Bead Array (CBA) Human Th1/Th2/Th17 Cytokine assays (Becton, Dickson Company, BD Biosciences, CA 95131 USA.) which simultaneous quantification of seven cytokines (IL-2, IL-4, IL6, IL-10, TNF-α, IFN-γ, and IL-17A) following the manufacturer’s instructions.

2.4. Statistical Analysis

The Kendall’s rank correlation coefficient (Ƭ) was used to determine the correlation between log10 transformed data for cytokine levels and CD4+ T- and CD8+ T-lymphocytes, CD4/CD8 ratio, and virus load. All analysis was done using STATA version 13.1 (StataCorp, Texas, USA) and Graph Pad Prism7 (GraphPad Software Inc, California, USA).

3. RESULTS

3.1. Demographics of the Study Population

A total of 450 prospective study participants were screened. Three hundred and one (301) participants with CD4+ T lymphocyte count greater than 350 cells/µL were enrolled the study. Two hundred and forty-seven (247/301), 82% who had sufficient archived serum specimens were included in the current study (Fig. 1).

Fig. (1)
Participants enrolment flow chart.


3.2. T-lymphocytes Counts and Virus Load

The median CD4+ T- and CD8+ T-lymphocyte counts were 458 cells/μL, inter quartile range (IQR): 405-556 cells/μL and 776 cells/μL (IQR:581-1064), respectively, whilst the median CD4/CD8 ratio was 0.6 (IQR:0.45-0.86). The median virus load was 3.3 Log10 copies/mL, IQR (2.74-3.93) (Table 1).

Table 1
Correlation of virus load with CD4+ T- and CD8+ T- lymphocyte counts and CD4/CD8 ratio.


Table 2
Correlation of cytokine levels with CD4+ T-lymphocyte counts and virus load.


3.3. Correlation of CD4+ T-, CD8+ T-lymphocyte Counts, CD4/CD8 Ratio with Viral Load

Low CD4+ T-lymphocyte counts (Ƭ =-0.115, p=0.010) and CD4/CD8 ratio (Ƭ =-0.091, p=0.044) were correlated with high viral load whilst there was no significant correlation between CD8+ T-lymphocyte counts with viral load (Ƭ =0.044, p=0.328), (Table 1).

The Kendall’s rank correlation coefficient (Ƭ) was used to determine the correlation between CD4+ T- and CD8+ T-lymphocytes, CD4/CD8 ratio with virus load. *P-value <0.05 was considered statistically significant.

3.4. Correlation of Cytokines Levels with CD4+ T-, CD8+ T-lymphocyte Counts, CD4/CD8 Ratio and Virus Load

There was no significant correlation between cytokine levels and CD4+ T-, CD8+ T-lymphocyte counts and CD4/CD8 ratio (Table 2 and Fig. 2). However, high concentrations of IL-17A (Ƭ =-0.1107, p=0.012) and IL-6 (Ƭ=-0.0955, p=0.034) were significantly correlated with high virus load.

The Kendall’s rank correlation coefficient (Ƭ) was used to determine the correlation between log10 transformed data for cytokine levels and CD4+ T- and CD8+ T-lymphocytes, CD4/CD8 ratio and virus load.*P-value <0.05 was considered statistically significant.

Based on the medical history collected at enrolment, the median time since the diagnosis of HIV infection was 6.3 years, thus the majority of the participants can be considered as chronically infected.

4. DISCUSSION

Cytokine levels in an ART naïve cohort infected predominantly with HIV subtype C the major subtype in Zimbabwe [15Tien PC, Chiu T, Latif A, et al. Primary subtype C HIV-1 infection in Harare, Zimbabwe. J Acquir Immune Defic Syndr Hum Retrovirol 1999; 20(2): 147-53.
[http://dx.doi.org/10.1097/00042560-199902010-00006] [PMID: 100 48901]
] were measured to investigate their correlation with CD4+ T-lymphocyte counts and virus load, the traditional biomarkers of HIV disease progression. Based on Kendall’s rank correlation, high IL-17A and IL-6 levels were correlated with high viral load. Interestingly, none of the measured cytokines were significantly correlated with CD4+ T- and CD8+ T-lymphocytes counts or CD4/CD8 ratio. However, we confirmed the inverse correlation of low CD+T-lymphocyte counts with high virus load as has been established in previous studies [3Langford SE, Ananworanich J, Cooper DA. Predictors of disease progression in HIV infection: A review. AIDS Res Ther 2007; 4: 11.
[http://dx.doi.org/10.1186/1742-6405-4-11] [PMID: 17502001]
]. We also noted that although CD8+ T-lymphocyte counts were not correlated with viral load, interestingly, low CD4/CD8 ratio was correlated with high virus load and thus may be used as a potential marker of HIV disease progression. It is well established that whilst there is a depletion of CD4+ T-lymphocytes counts in HIV infection, there is a compensatory increase in CD8+T-lymphocyte leading to a reduced CD4/CD8 ratio which is normally greater than 1 [16Isailovic N, Daigo K, Mantovani A, Selmi C. Interleukin-17 and innate immunity in infections and chronic inflammation. J Autoimmun 2015; 60(Suppl C): 1-11.]. The role of CD8+ T-lymphocyte counts in immune response to HIV infections is not fully understood as opposed to its well-studied functional capacity. In a previous study [17Zijenah LS, Katzenstein DA, Nathoo KJ, et al. T lymphocytes among HIV-infected and -uninfected infants: CD4/CD8 ratio as a potential tool in diagnosis of infection in infants under the age of 2 years. J Transl Med 2005; 3(1): 6.
[http://dx.doi.org/10.1186/1479-5876-3-6] [PMID: 15683549]
] we showed that the CD4/CD8 ratio could be used as a potential tool for diagnosis of HIV infection in infants under the age of 18 months and indeed in adults.

IL-17A is a major inflammatory mediator and IL-17A producing CD4+ T-lymphocytes (Th17) are a key subset of cells maintaining mucosal integrity and host defence against pathogens through mucosal barrier [16Isailovic N, Daigo K, Mantovani A, Selmi C. Interleukin-17 and innate immunity in infections and chronic inflammation. J Autoimmun 2015; 60(Suppl C): 1-11., 18Curtis MM, Way SS. Interleukin-17 in host defence against bacterial, mycobacterial and fungal pathogens. Immunology 2009; 126(2): 177-85.
[http://dx.doi.org/10.1111/j.1365-2567.2008.03017.x] [PMID: 1912 5888]
]. IL-17A may induce production of IL-1β and IL-6 pro-inflammatory cytokines [19Miossec P, Kolls JK. Targeting IL-17 and TH17 cells in chronic inflammation. Nat Rev Drug Discov 2012; 11(10): 763-76.
[http://dx.doi.org/10.1038/nrd3794] [PMID: 23023676]
] which are strongly linked to inflammatory disorders [20Challacombe SJ, Sweet SP. Oral mucosal immunity and HIV infection: current status. Oral Dis 2002; 8(Suppl. 2): 55-62.
[http://dx.doi.org/10.1034/j.1601-0825.2002.00013.x] [PMID: 1216 4661]
]. Although the current study did not measure mucosal cytokine levels, there is strong evidence of a critical role mucosal immunity plays in HIV transmission [21Kozlowski PA, Neutra MR. The role of mucosal immunity in prevention of HIV transmission. Curr Mol Med 2003; 3(3): 217-28.
[http://dx.doi.org/10.2174/1566524033479852] [PMID: 12699359]
, 22Hicks DR, Martin LS, Getchell JP, et al. Inactivation of HTLV-III/LAV-infected cultures of normal human lymphocytes by nonoxynol-9 in vitro. Lancet 1985; 2(8469-70): 1422-3.
[http://dx.doi.org/10.1016/S0140-6736(85)92584-X] [PMID: 2867 413]
]. The proposed broken mucosal surfaces imply a weakened immune system which promotes HIV transmission in the mucosal tissue. Mucosal cytokine levels have been used as markers of the effectiveness of microbicides aimed at blocking viral transmission [23Ancuta P, Monteiro P, Sekaly RP. Th17 lineage commitment and HIV-1 pathogenesis. Curr Opin HIV AIDS 2010; 5(2): 158-65.
[http://dx.doi.org/10.1097/COH.0b013e3283364733] [PMID: 20543 594]
]. Th17 are suggested to favour viral replication during acute HIV infection [24El Hed A, Khaitan A, Kozhaya L, et al. Susceptibility of human Th17 cells to human immunodeficiency virus and their perturbation during infection. J Infect Dis 2010; 201(6): 843-54.
[http://dx.doi.org/10.1086/651021] [PMID: 20144043]
, 25Klatt NR, Brenchley JM. Th17 cell dynamics in HIV infection. Curr Opin HIV AIDS 2010; 5(2): 135-40.
[http://dx.doi.org/10.1097/COH.0b013e3283364846] [PMID: 20543 590]
], and accelerated disease progression in chronically infected individuals through inefficient mucosal repair, increased microbial translocation and hyperactivation of the immune system [26Brenchley JM, Douek DC. HIV infection and the gastrointestinal immune system. Mucosal Immunol 2008; 1(1): 23-30.
[http://dx.doi.org/10.1038/mi.2007.1] [PMID: 19079157]
, 27Li Q, Duan L, Estes JD, et al. Peak SIV replication in resting memory CD4+ T cells depletes gut lamina propria CD4+ T cells. Nature 2005; 434(7037): 1148-52.
[http://dx.doi.org/10.1038/nature03513] [PMID: 15793562]
]. These findings may plausibly explain the correlation of IL-17A levels with virus load in the current study.

In addition to IL17, IL-6 levels were significantly correlated with virus load in the current study. IL-6 mediates Th17 generation [28Kimura A, Naka T, Kishimoto T. IL-6-dependent and -independent pathways in the development of interleukin 17-producing T helper cells. Proc Natl Acad Sci USA 2007; 104(29): 12099-104.
[http://dx.doi.org/10.1073/pnas.0705268104] [PMID: 17623780]
, 29Zhou L, Ivanov II, Spolski R, et al. IL-6 programs T(H)-17 cell differentiation by promoting sequential engagement of the IL-21 and IL-23 pathways. Nat Immunol 2007; 8(9): 967-74.
[http://dx.doi.org/10.1038/ni1488] [PMID: 17581537]
] which promotes a pro-inflammatory status and contribute to inflammation through induction of acute-phase proteins like C-reactive protein [30Keating SM, Jacobs ES, Norris PJ. Soluble mediators of inflammation in HIV and their implications for therapeutics and vaccine development. Cytokine Growth Factor Rev 2012; 23(4-5): 193-206.
[http://dx.doi.org/10.1016/j.cytogfr.2012.05.006] [PMID: 22743035]
]. IL-6 has been reported to enhance HIV replication at the transcriptional and post-transcriptional level [6Poli G. European Society for Clinical Investigation. Laureate ESCI award for excellence in clinical science 1999. Cytokines and the human immunodeficiency virus: From bench to bedside. Eur J Clin Invest 1999; 29(8): 723-32.
[http://dx.doi.org/10.1046/j.1365-2362.1999.00525.x] [PMID: 10457 158]
]. It seems the correlation of IL-6 levels with virus load in our study may be explained by the inflammatory environment promoted by IL-6. Generally, inflammation-inducing cytokines (for example IL-17A and IL-6) promote HIV replication coupled with CD4+ T-lymphocyte count decline through enhanced proviral transcription, recruitment, and activation of CD4+ T-lymphocyte, and activation-induced apoptosis by bystander T-lymphocytes [31Lin RH, Hwang YW, Yang BC, Lin CS. TNF receptor-2-triggered apoptosis is associated with the down-regulation of Bcl-xL on activated T cells and can be prevented by CD28 costimulation. J Immunol 1997; 158(2): 598-603.
[PMID: 8992973]
-33Swingler S, Mann A, Jacqué J, et al. HIV-1 Nef mediates lymphocyte chemotaxis and activation by infected macrophages. Nat Med 1999; 5(9): 997-103.
[http://dx.doi.org/10.1038/12433] [PMID: 10470075]
].

Fig. (2)
Correlation of cytokine levels (log10) with viral load (log10).


Although in our study the CD4+ T-lymphocyte counts and virus load did not correlate with IL-2, IL-4, and IFN-γ, others have reported that these cytokines are needed for activation of antiviral T-lymphocyte expansion and humoral immunity which may then increase viral replication through activation of HIV-infected cells [31Lin RH, Hwang YW, Yang BC, Lin CS. TNF receptor-2-triggered apoptosis is associated with the down-regulation of Bcl-xL on activated T cells and can be prevented by CD28 costimulation. J Immunol 1997; 158(2): 598-603.
[PMID: 8992973]
]. During HIV infection, high levels of inflammatory cytokines (IL-12p40, IL-12p70, IFN-γ, IL-7, and IL-15) are associated with high viraemia and a decrease in CD4+ T-lymphocyte counts [34Keating SM, Golub ET, Nowicki M, et al. The effect of HIV infection and HAART on inflammatory biomarkers in a population-based cohort of women. AIDS 2011; 25(15): 1823-32.
[http://dx.doi.org/10.1097/QAD.0b013e3283489d1f] [PMID: 21572 306]
]. In late-stage HIV infection, low levels of IL-2 and IFN-γ plus elevated levels of IL-4 and IL-10 are associated with a poor HIV antigen-specific immunity coupled with emergence of opportunistic infections [11Manasa J, Musabaike H, Masimirembwa C, Burke E, Luthy R, Mudzori J. Evaluation of the Partec flow cytometer against the BD FACSCalibur system for monitoring immune responses of human immunodeficiency virus-infected patients in Zimbabwe. Clin Vaccine Immunol 2007; 14(3): 293-8.
[http://dx.doi.org/10.1128/CVI.00416-06] [PMID: 17267593]
]. Additionally, IL-12p40 has been reported to be a good biomarker for CD4+ T-lymphocyte decline and virus load increase in subtype C infection [35Iketleng T, Moyo S, Gaseitsiwe S, et al. Plasma cytokine levels in chronic asymptomatic HIV-1 subtype C infection as an indicator of disease progression in botswana: A retrospective case control study. AIDS Res Hum Retroviruses 2016; 32(4): 364-9.
[http://dx.doi.org/10.1089/aid.2015.0163] [PMID: 26414751]
]. Conversely, Twizerimana et al. [36Twizerimana AP, Mwatha J, Musabyimana JP, et al. Immunological profiles in HIV positive patients following Haart Initiation in Kigali, Rwanda. East Afr Med J 2014; 91(8): 261-6.
[PMID: 26862650]
] demonstrated IL-10 down-regulation of Th1 cytokines and HIV disease progression associated Th1 to Th2 cytokine shift.

HIV-1 infection is characterized by a marked depletion of CD4+ T-lymphocytes especially in gut-associated lymphoid tissues coupled with immune hyperactivation through microbial translocation [37Valverde-Villegas JM, Matte MC, de Medeiros RM, Chies JA. New insights about Treg and Th17 cells in HIV infection and disease progression. J Immunol Res 2015; 2015647916
[http://dx.doi.org/10.1155/2015/647916] [PMID: 26568963]
]. Although we speculate that the correlation of IL-17A and IL-6 levels with virus load is through impaired mucosal immunity and continuous immune hyperactivation, one of the limits of our study is that we did not investigate the source of these cytokines. Additional study limits include the cross-sectional nature of our study that did not allow repeated measurements of cytokines during the course of participants’ follow-up to correlate with changes of CD4+ T-lymphocyte counts and virus load. Repeated cytokine quantification over time would shed more light on the potential of cytokine profiles as biomarkers of HIV disease progression.

CONCLUSION

Low CD4+ T- lymphocytes and CD4/CD8 ratio were significantly correlated with high VL. Whilst CD4+ and CD8+T-lymphocytes counts were not correlated with cytokine levels, high levels of IL-17A and IL-6 were significantly correlated with VL. Our study contributes to the growing knowledge the role of cytokine profiles in the immune response to HIV infection.

LIST OF ABBREVIATIONS

ART = Antiretroviral Therapy
CD4 = Cluster of Differentiation 4
CD8 = Cluster of Differentiation 8
CI = Confidence Interval
IQR = Interquartile Range
HIV = Human Immunodeficiency Virus
IFN = Interferon
IL = Interleukin
MRCZ = Medical Research Council of Zimbabwe
Th = T helper
TNF = Tumour Necrosis Factor
TGF = Transforming Growth Factor
VL = Virus Load

AUTHORS’ CONTRIBUTIONS

TM and LSZ conceived and designed the study. TM, MT, and BM performed the assays. TB and KM conducted the data analysis. TM wrote the first draft.

All authors reviewed and approved the final version of the manuscript.

ETHICS APPROVAL AND CONSENT TO PARTICIPATE

The study was approved by the Medical Research Council of Zimbabwe (MRCZ/A/1558).

HUMAN AND ANIMAL RIGHTS

No animals were used in this research. All human research procedures followed were in accordance with the ethical standards of the committee responsible for human experimentation (institutional and national), and with the Helsinki Declaration of 1975, as revised in 2013.

CONSENT FOR PUBLICATION

Written informed consent was obtained from each participant.

AVAILABILITY OF DATA AND MATERIALS

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

FUNDING

The study was funded by EDCTP I; TESA I: CG_cb_07_41700 and 1051 TESA II EDCTP-RegNet 2015 part of the EDCTP2 programme (supported under Horizon 2020, the European Union’s Framework Programme for Research and Innovation).

CONFLICT OF INTEREST

The authors declare no conflict of interest, financial or otherwise.

ACKNOWLEDGEMENTS

We acknowledge data entry personnel Brian Nyauzame and Tambudzai Margaret Pswarayi. We thank the study participants for their participation in the study and the Parirenyatwa Opportunistic Infections Clinic staff.

REFERENCES

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