It has been known that HIV-1 infection alters the course of Mycobacterium tuberculosis infection and substantially increases the risk of active tuberculosis (TB). Various cytokines play different roles in HIV-1 and TB individually and in a co-infection stage of disease. IL-2 play CD4+ proliferation, IL-4 activate B cells, CD4 cell IL-6/IL-10 dysregulate and CD4+ T (Th17) cell subset lost during HIV-1 infection. IL-22 and IL-27-producing CD4 (+) T cells play immune reconstitution inflammatory syndrome (IRIS) following the commencement of antiretroviral therapy (ART). Higher values of IFN-γ, IL-2, IL-6 and IL-10 were observed in HIV-positive during anti-tuberculous treatment. Combination antiretroviral therapy in tuberculosis (TB) and HIV-1 infection is associated with an immune reconstitution inflammatory syndrome (TB-IRIS). Based on different roles of each cytokine in HIV-1 and TB individually and co-infection, changes occur in therapy is described in the present review.

TB: Tuberculosis;

TB: Tuberculosis;

TPE: Tuberculous pleural effusion;

TB-IRIS: TB-associated immune reconstitution inflammatory syndrome IRIS: immune reconstitution inflammatory syndrome;

MTB: Mycobacterium tuberculosis;

HIV-1: human immunodeficiency virus type 1;

DC-SIGN: Dendritic Cell-Specific Intercellular adhesion molecule-3- Grabbing Non-integrin; 

ART: antiretroviral therapy;

HAART: Highly active antiretroviral therapy;

JAK/STAT: Janus kinase/signal transducers and activators of transcription;

PAMPs: pathogen-associated molecular patterns; 

HLA-DR: Human Leukocyte Antigen–DR isotype; 

AIDS: Acquired immunodeficiency syndrome; 

NKT: Natural killer T cells;

PBMC: peripheral blood mononuclear cell; 

LTB: Latent tuberculosis;

MDR-TB: Multidrug-resistant tuberculosis; 

MDSC: Myeloid-derived suppressor cells;

EFV: Efavirenz;

RAL: Raltegravir;

7-oxoDHEA: 7-oxodehydroepiandrosterone; 

NRTIs: Nucleoside reverse transcriptase inhibitors; 

TLR: Toll-like receptor;

RNAi: RNA interference;

MYD88: Myeloid differentiation primary response 88; 

IRAK1: Interleukin-1 receptor-associated kinase 1; 

NRTIs: Nucleoside reverse transcriptase inhibitors;

NNRTIs: Non-nucleoside Reverse Transcriptase Inhibitors; 

TRAF6: Tumor necrosis factor receptor-associated factor 6; 

TREM-1: Triggering receptor expressed on myeloid cells 1; 

MDR-TB: Multidrug-resistant tuberculosis;

The World Health Organization (WHO) estimated approximately one- third of the world’s population is infected with Mycobacterium tuberculosis (MTB) and active disease with human immunodeficiency virus type 1 (HIV-1) infection, mainly in Africa. HIV co-infection is known risk factor for progression of M. tuberculosis infection to active disease and increasing the risk of latent TB reactivation. HIV and tuberculosis (TB) co-infections have an immense health problem in diagnostic and therapeutic challenges [1-4]. In M. tuberculosis and HIV co infection, both potentiate and accelerating one another in deterioration of immunological functions resulting in premature death of infected host, ifuntreated.

HIV infection is the depletion of CD4+ T cells. The immunopathogenic features together systemic and chronic state of immune activation accelerated T cell contribute to the progression of HIV disease and the loss of immune balance between Th17 and regulatory T cells (Treg) during HIV disease. Cell-mediated immunity during M. tuberculosis infection is essential for control of activation of both CD4+ and CD8+ T cells [5-7]. T cells recruited to the infected lung are thought to control infection by producing IFN-γ in response to mycobacterial antigens presented by macrophages. It has been reported that DC-SIGN, a dendritic cell-specific HIV-1-binding protein that enhances trans- infection of T cells [8]. An immune reconstitution inflammatory syndrome (IRIS) develops in M. tuberculosis and HIV co- infected patients undergo anti-TB treatment and antiretroviral therapy (ART) [9, 10]. TB patients present with an exacerbation of symptoms and radiological manifestations recognize predictors of IRIS in low CD4+ T lymphocyte counts and high plasma viral load prior to initiation of ART. CD4+ counts increase after highly active antiretroviral therapy (HAART) onset.

Though combination antiretroviral therapy (ART) has significantly improved the clinical outcome, they develop hyper inflammatory reactions. Antiretroviral treatment (ART) reduces the risk of developing active tuberculosis (TB) in HIV-1 co-infected patients. RNAseq analysis of whole blood-derived RNA from individuals with latent TB infection co-infected with HIV-1, a significant fall in RNA sequence abundance of the Hallmark IFN-α, IFN-γ, IL-6/JAK/STAT3 signaling to indicate reduced immune activation and inflammation. ART-induced decrease in immune activation combined with the improved antigen responsiveness, contributes to reduced susceptibility to tuberculosis in HIV-1/Mtb co- infected persons.

Based on different roles of cytokines in HIV-1, tuberculosis (TB) and co- infection during the disease and the therapy is described in the present review.

Cytokine roles in HIV, Tuberculosis and HIV-1 Tuberculosis co-infection

Interleukin-2 (IL-2) role. IL-2 cytokine is a glycoprotein that stimulates the growth of T cell lymphocytes. The major sources of IL-2 are activated CD4+ and CD8+ T cells. HIV-1 interactions implicate the gradual loss of IL-2 secretionand proliferation. It is an early sign of T cell exhaustion in HIV-1 infection. T-helper type 1 (Th1) cytokines such as IL-2 and the antiviral IFN-γ decrease duringthe course of HIV-1 infection [11]. IL-2 can simultaneously activate T effectorcells and Foxp3(+) Treg populations. It confers resistance to severe TB without enhancing M. tuberculosis infection. IL-2-producing Mtb-specific CD4 T cells Th1 cytokines IFN-γ and/or TNF-α are associated with individuals with latent tuberculosis. The Mtb containment high proportion of Mtb-specific CD4 T cells producing Th1 cytokines in the absence of IL-2 are associated with patients suffering from active TB disease [12]. HIV/TB co-infected patients of TB latency targeted by HIV-1 infection, resulting in early peripheral depletion of MTB-specific CD4+ T cells after HIV infection. Anti-tubercular treatment (ATT) associated with changes in the phenotype of Mtb-specific CD4 T cells with decreased expression of HLA-DR and increased CD27 and CD153 expression [13]. Polyfunctional T cell responses of IFN-γ (+) IL-2 (+) TNF-α (+) to TB antigens has been observed in HIV-1-infected patients dependent on their TB status, CD4 counts, and anti-retroviral exposure [14].

Interleukin-4 (IL-4) role. IL-4 is a cytokine that stimulates the proliferation of activated B-cells. It inducesdifferentiation of naivehelper T cells (Th0 cells) to Th-2 cells.IL-4 stimulates the expression of all HIV-

1 isolates via a transcriptional activation mechanism. HIV infection functionally impairs Mycobacterium tuberculosis-specific CD4 and CD8 T-cell responses. HIV infection significantly reduced the Th2 (interleukin 4 [IL-4]/IL-5/IL-13) producingM. tuberculosis-specific CD4 T cells [15]. Blocking IL-4 cause significantly neutralized Mycobacterium containment and CD4+ IFNγ+ levels Treg expression. IL-4 can subvert mycobacterial containment in human macrophages, probably via perturbations in Treg and Th1-linked pathways[16].

Interleukin-6 (IL-6) role. IL-6 interleukin acts as both a pro- inflammatory cytokine and an anti-inflammatory myokine. IL-6 is secreted by macrophages in response to specific microbial molecules, referred to as pathogen-associated molecular patterns (PAMPs). In HIV- 1 antibody positive patients, no correlation between IL-6 concentrations and CD4 positive cell numbers but a correlation with IgG. HIV-induced IL-6/IL-10 dysregulation of CD4 cells is associated with defective B cell help and autoantibody formation against CD4 cells [17]. In anti-TB treatment, a reduction in the percentage of CD4+ T cells showed a significant restoration similar to that of controls.Moreover, after intensive anti-TB treatment, serum levels of IL-1β, soluble interleukin-2 receptor, IL-6, and tumour necrosisfactor-α were significantly decreased compared with before treatment [18]. The HIV envelope glycoprotein gp160 support B cell differentiation. T cell dependence for gp160-induced B cell differentiation responses requires contact-dependent interaction of several cell surface molecules and IL-6 secretion [19].

Interleukin-10 (IL-10) role. IL-10 is an anti-inflammatory cytokine, which is primarily produced by monocytes, and lesser extent by type-II T helper cells (TH2) lymphocytes, mast cells, CD4+CD25+Foxp3+ regulatory T cells and certain subset of activated T cells and B cells. The inhibitory effectsof IL-10 on HIV-1 replication become more pronounced in late stages of disease when CD4+ lymphocytes are depleted and replication in macrophages and monocytes. Interleukin-10 induced by human immunodeficiency virus type 1 and its gp120 protein in human monocytes/macrophages. Interleukin-10 influenced promoter polymorphisms on HIV-1 susceptibility pathogenesis and play a role by transcriptional regulation [20-22].

HIV induces the immunosuppressive IL-10 production in monocytes that interferes with HIV entry through CD4 molecules. IL-10 is a more potent inhibitor than TGF-β for both T-cell subsets CD4 (+) and CD8 (+) T-cell responses to M. tuberculosis infection control [23].

IL 10 production by macrophages and T-cells during the course of Mtb is observed to increaseCD4 T cell counts and suppression of HIV viral load for all patients under HAART and TB treatment. Descendent trajectories were observed for the activated CD8 (+)/CD38 (+) and CD3 (+)/HLA- DR (+) T cell subsets, and for plasma concentration of gamma- interferon (IFN-γ) in tuberculosis and HIV-positive individuals during antituberculous treatment [24].

Interleukin-12(IL-12) role. IL-12 is a naturally produced by dendritic cells, macrophages, neutrophils, and human B-lymphoblastoid. IL-12 family is unique heterodimeric cytokines, which includes IL-12, IL-23, IL-27 and IL-35. HIV-1 infection dysregulate regulatory pathways are characterized by decreased production of IL-12 and IFN-γ pro- inflammatory cytokines. The inhibition of IL-12 production by accessory cells after HIV-1 infection has been identified as a potential factor responsible for impairedinnate and Th1 cell-mediated responses in AIDS patients. There was found a decreased CD40 ligand in CD4 T cells dependent IL-12 production in HIV-1 infection [25]. Human IL-12 and IL-23 are both required for optimal IFN-γ-dependent immunity to mycobacteria [26]. Systemic immune activation is critical to the pathogenesis of HIV-1 disease, and is accentuated in HIV/TB co-infected patients. The contribution of immune activation at sites of HIV/TB co- infection to viral activity, CD4 T cell count, and productive HIV-1 infection were measured markers of immune activation both in pleural fluid and plasma in HIV/TB co-infected subjects.

Interleukin-15 (IL-15) role. IL-15 is a cytokine similar to IL-2. IL-15 binds to signals through IL-2/IL-15 receptor beta chain (CD122) and the common gamma chain (gamma-C, CD132). IL-15 is secreted by mononuclear phagocytes. IL-15 regulates susceptibility of CD4 + T cells to HIV infection. IL-15 level was significantly elevated viral loads in HIV-1 infected patients compared to uninfected controls, suggesting a significant direct correlation between IL-15 and HIV-1 viraemia and an inverse correlation between IL-15 levels and CD4+ T cell counts [27]. NK cells produce not only IFN-γ but also IL-22 induced by IL-15 and DAP-10. Many invariant natural killer T (iNKT) cells are CD4+ and few iNKT cells are CD8+. Other iNKT cells are negative for both CD4 and CD8. Gamma Delta (γδ) T cells represents an early innate defense anti- mycobacterial immunity [28]. As NK cells are a significant source of the bactericidal effector molecule granulysin, infection of PBMC (peripheral blood mononuclear cell) with HIV-1 suppresses NK cell induction of granulysin by IL-15, but does not impair activation by BCG. This study suggests that HIV impair the anti-bacterial function of NK cells and have implications for clinical use of IL-15 to augment innate cell mediated immunity in HIV positive patients [29].

Interleukin-17 (IL-17) role. IL-17 is a pro-inflammatory cytokine. IL- 17 is a unique CD4+ T (Th17)cell subset play a role in host defense. Th17 cells are lost duringHIV infection, althoughthere is also a beneficial role of HIV-specific CD4 cells. Patients with lower immune activation exhibited higher frequency of bulk CD4 T-cells producing IFN-γ or IL-

17 which change higher effector-to-regulatory cell ratios [30, 31]. Although initial studies suggested that γδ T cells are a primary source of IL-17 in response to M. tuberculosis infection [32]. Th17 cells are the major IL-17–producing cells and participate in the protective immunity against M. tuberculosis. The high proportion of CD4 (+) IFN-γ (+) IL- 17(+) cells were detected in low responder TB patients with severe pulmonary lesions [33]. The cytokine frequency and polyfunctionality profile of Mycobacterium tuberculosis (MTB)-specific CD4+ T cells in HIV-infected persons with latent TB infection (LTBI) or Pulmonary TB (PTB) is comparable. This similarity suggests that LTBI represent a smoldering state of persistent MTB replication rather than dormant infection [34].

Interleukin-18 (IL-18) role. IL-18 is a pro-inflammatory cytokine. It is also known as IFN-γ inducing factor. Both hematopoietic cells and non- hematopoietic cells have the potential to produce IL-18. IL-18 brings an alteration in the immune response to tuberculosis (TB). Mycobacterial antigen-induced production plasma levels of inflammatory cytokine IFN- γand its regulatory cytokines IL-18, and IL-12, IL-10 in HIV co-infected with TB patients. Patients with multidrug-resistant TB (MDRTB) have dysregulated IL-12, IL-18 and IL-10 production during Mycobacterium tuberculosis.

Interleukin-22 (IL-22) role. HIV infection indicates a gradual loss of CD4+ T-cellswith progressive impairment of immunity lead ultimately to death. Study of IL-22+ cells of HIV-1 co-infected with Mycobacterium tuberculosis patients detect the levels of peripheral blood membrane- bound IL-22+ T cell subsets. Antigen-specific membrane-bound IL-22+ T cells are highly expressed in MTB co-infection of HIV-1 infected individuals, and play an important role in anti-TB immune response during co-infection with HIV-1 [35]. In multidrug-resistant TB (MDR- TB), low systemic and Mtb-induced Th22 responses associated with a high sputum bacillary load and bilateralism of lung lesions, suggesting that Th22 response could be influencing the ability of MDR-TB patients to control bacillary growth and tissue damage. The level of IL-22 and IFN-γ were significantly lower in the pleural fluid of HIV-1 co-infected TB than the TB patients. Antigen-specific membrane-bound IL-22+ T cells are highly expressed in MTB co-infection of HIV-1 and play anti- TB immune response. Proteomics analyses revealed the enrichment of HIF-1α, galectins and Hsp90 host factors, which promoted HIV-1 reactivation M. tuberculosis-specific exosomes [36]. Tuberculosis (TB) and AIDS are the leading causes of death, but in some TB-HIV co- infected individuals treated for both diseases simultaneously, an inflammatory reaction termed immune reconstitution inflammatory syndrome (IRIS) occur.

Interleukin-27 (IL-27) role. IL-27 is a heterodimeric cytokine and a member of the IL-12 family. IL-27 has been shown to be a potent inhibitor of HIV-1 infection in CD4+ T cells and macrophages. IL-27 treated dendritic cells (DCs) have shown highly potent inhibitors of HIV- 1, whereas IL-12, IL-23 and IL-35 have no effect on HIV-1 replication. IL-27-producing CD4 (+) T cells represent a distinct T cell subset in tuberculosis pleural effusion (TPE). Both the numbers of IL-27- producing CD4 (+) T cells and concentration of soluble IL-27 have been found to be increased in tuberculous pleural effusion (TPE). In HIV- infected, the plasma IL-27 level correlates positively with CD4+ T-cell count and negatively with HIV- viral load. IL-27 in HIV- M. tuberculosis co-infection acts on MDSC both in autocrine and paracrine manner. HIV-infected individuals with virologic suppression have increased levels of circulating IL-27 and myeloid-derived suppressor cells (MDSC). IL-27/IL-27R and MDSC provide attractive biomarkers to assess tuberculosis prognosis during HIV-infection[37].

Interleukin-32 (IL-32) role. IL-32 is inflammatory and clinical markers, expressed during HIV-1 infection in CD4+ T cells, B cells, macrophages, and dendritic cells. Increased expression of IL-32 seen with IFN-γ, Th1 and Tc1 in virologically suppressed HIV-1-infected patients. IL-32 is highly expressed in the mucosal epithelium of HIV-1- infected gut. IL-32's action on IFN-γ and IFN-γ secreting T cell subsets help sustain the immune activation and dysregulation found in patients with HIV-1 achieving viral suppression. Both IL-32 and IFN-γ genes were also more strongly expressed in CD4+ T cells than in CD14+ monocytes. IL-32 levels remain elevated in treating HIV-1-infected patients [38].

Interleukin-35 (IL-35) role. IL-35 is anti-inflammatory cytokine from the IL-12 family. IL-35 is produced by a wide range of regulatory lymphocytes and plays a role in immunesuppression. IL-35 can block the development of Th1 and Th17 cells by limiting early T cell proliferation. Little is known for IL-35 response in patients with active tuberculosis (ATB). Active tuberculosis patients exhibited increases in serum IL-35 and in mRNA expression of both subunits of IL-35 (p35 and EBI3) in white blood cells and peripheral blood mononuclear cells. TB infection was associated with expression of p35 or EBI3 proteinin CD4 (+) but not CD8 (+) T cells. Most p35 (+) CD4 (+) T cells and EBI3 (+) CD4 (+) T cells expressed Treg-associated marker CD25. IL-35 in the blood serves as a biomarker for immune status and prognosis in TB [39].

Immune mechanism in HIV co-infection Tuberculosis therapy

Tuberculosis is a serious health threat, especially for people living with HIV. HIV virus increases the potency of the tuberculosis bacterium (Mtb) by affecting a central function of the immune system. In HIV infected individuals, CD38 and HLA-DR on CD4 and CD8 T lymphocytes are elevated immune reconstitution inflammatory syndrome (IRIS). In  response  to antiretroviral therapy-mediated  recovery   of the immune system in HIV-infected patients, it was seen effects of initiating efavirenz (EFV) or raltegravir (RAL)-based antiretroviral therapy (ART) regimens HIV-1 deoxyribonucleic acid (DNA) levels and inflammation biomarkers in the highly inflammatory setting of advanced HIV-1 disease with tuberculosis (TB) co-infection [40].

TB treatment in HIV-TB co-infected persons have a prolonged duration due to the immune system fails to provide an adequate support for the therapy. 7-oxo-DHEA modifies the cytokine balance and the phenotype of CD4 + T cells more favorable to mycobacteria control where novel treatment approaches as co-adjuvant for the treatment of TB [41]. Thalidomide, which inhibits monocyte TNF-α production and co- stimulates T cells, was tested for immune modulation in patients with human immunodeficiency virus HIV infection and TB. Thalidomide therapy resulted in increased levelsof plasma IL-2 receptor, solubleCD8, IFN-γ, and IL-12. Thalidomide treatment increased CD4+ and CD8+ T cell counts and increased viral replication [42].

Combination antiretroviral therapy in tuberculosis (TB) and HIV-1 infection is associated with an immune reconstitution inflammatory syndrome (TB-IRIS). In serum, higher concentrations of TNF, IL-6, and IFN-γ were observed with TB-IRIS patients. Serum IL-6 and TNF-α decreased during prednisone therapy in TB-IRIS patients. It also showed increased IL-1β, IL-2, IL-6, IL-8, IL-10, IL-12p40, IFN-γ, GM-CSF and

TNF in TB-IRIS cultures in peripheral blood mononuclear cell culture in the presence of heat-killed Mycobacterium tuberculosis [43].

HIV-1 patients co-infected with some pathogens are at risk ofdeveloping the IRIS when initiating antiretroviral therapy (ART). HIV-TB co- infected patients prescribed with anti-tuberculosis treatment and ART develop TB-IRIS [44].TB-IRIS patients and controls had similar CD4 counts, levels of T-cell-associated immune activation, and frequencies of IFN-γ(+)/IL-2(+)/TNF-α(+),CD4(+) T-cells prior to ART initiation. After ART initiation, cellular immune activation and T-cell subsets also were similar in TB-IRIS patients and controls. In contrast, TB-IRIS patients had significantly greater early increases in the IFN-γ (+)/IL-2 (+)/TNF-α (+)CD4(+) T-cells in ART and increases IL-6 is associated with the development of paradoxical TB-IRIS [45].

There is a high prevalence of drug-resistant mutations in HIV and HIV- TB co-infected patients. In the HIV-TB group had mutations to nucleoside reverse transcriptase inhibitors (NRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), and protease inhibitors (PIs), respectively.Silencing of the expression of the nuclearfactor of activated T cells 5 (NFAT5) by RNA interference (RNAi) inhibits Mycobacterium tuberculosis (MTb)-stimulated HIV-1 replication in co-infected macrophages. NFAT5 gene and protein expression are stronglyinduced by MTb, which is a Toll-like receptor (TLR) ligand RNAi key components of the TLR pathway in human monocytes, including the downstream signaling molecules MyD88, IRAK1, and TRAF6, significantly inhibits MTb-induced NFAT5 gene expression [46]. SOCS1 factor or IL-27 down-regulate the IFN-γ/IL-12 axis, thereby impairing control are mainly anti-inflammatory but indirectly inhibit efficient bacterial clearance. Increased replication of the virus was demonstrated in the lungs and within activated lymphocytes and CD14+ macrophages of the pleural space in M. tuberculosis infection. The suppressor of cytokine signaling 1 (SOCS1) is an inducible host factor during HIV-1 infection and regulates the late stages of the HIV-1 replication pathway. The function of many immune cells, including macrophages and DCs, is modulated by both HIV and M. tuberculosis. Increased replication of the virus was demonstrated locally, at sites of M tuberculosis infection in the lung, and within activated cells, including lymphocytes and CD14 + macrophages, of the pleural space of co-infected patients [47,48].

Impaired balance between pro-inflammatory and anti-inflammatory cytokines and apoptosis-induced depletion of immune effector cells accounts for the dissemination of both the pathogens and for a poor granulomatous reaction in Mtb-HIV co-infected patients [49]. Patients with HIV-associated tuberculosis (TB) initiating antiretroviral therapy (ART) develop an immune reconstitution inflammatory syndrome (TB- IRIS), the signature is characterized by over-representation of TLR signalling and TREM-1 activation of the inflammasome. Inhibition of MyD88 adaptor and group 1 caspases reduces secretion of IL-1 in TB- IRIS patients [50].

Various cytokines play different roles in HIV-1 and TB individually and in a co-infection stage of disease during infection. IL-2 play CD4+ proliferation, IL-4 activate B cells, CD4 cell IL-6/IL-10 dysregulate in HIV-1, CD4+ T (Th17) cell subset lost during HIV-1, IL-22 and IL-27- producing CD4(+) T cells represent a distinct T cell subset in tuberculous pleural effusion (TPE). It was seeing the effects of initiating efavirenz (EFV) or raltegravir (RAL)-based antiretroviral therapy (ART) regimens on human immunodeficiency virus (HIV)-1 deoxyribonucleic acid (DNA) levels and inflammation biomarkers in the highly inflammatory setting of advanced HIV-1 disease with tuberculosis (TB) co-infection.

HIV co infected TB patients have prolonged treatmentduration due to the immune system failing to provide support for the therapy. HIV co- infected TB patients have mutations to nucleoside reverse transcriptase, inhibits MTb-induced NFAT5 gene expression. It was noted that bacteria are not completely eradicated despite of a seemingly robust Th1 immune response in the latent phase of tuberculosis. A failure of the protective adaptive immune responses leads to reactivation of infection.

Gratefully acknowledged to Dr. V. K. Mahadik,Director, and R. D. Gardi Medical College for the encouragements, and to establish and develop research in biomedical sciences.