Effects Of Exogenous Interleukin-15and Interleukin-21on Cellular Immune Responses In HIV/AIDS-infected Individuals

Human immunodeficiency virus type1can invade directly the body’s immunesystem to destroy cell-mediated immunity and humoral immunity, make the body’simmune system nonresistant to the invasion，and bring difficulty to the developmentof drugs for specific treatment and also vaccines for prevention. In recent years, themorbidity of AIDS shows trend gradually growth, accompanied by more profoundstudies on the therapeutic strategies of AIDS. Highly active anti-retroviral therapy(HAATR) is currently the most widely used and most effective treatment for AIDS.However, because of its own limitation, it can only suppress the viral replication butnot remove the body of HIV-1storage, and may have some side effects, which hindersthe treatment of HIV-1infection. Therefore, it is necessary to look for morediversified treatment，which can enhance immune function of patients by maintainingthe reduction of viral load due to HAART at the same time.Many studies have confirmed that HIV-1infection leads to imbalance ofcytokines，reduction of Th1cytokines but increase of Th2cytokines. Some otherstudies show that HIV-1infection can activate the organic immune system. T cellactivating factor activated and stimulated the proliferation of T cells by affectingRNA transcription and protein synthesis, thereby inducing the expression of HIV-1.This shows that cytokines might be involved in the activation of HIV-1, and play animportant role in regulating immune response and maintaining immune balance.Recently, more and more researchers speculate that selectively blocking the secretionof some cytokines which can up-regulate the expression of HIV-1, or using some cytokines which are inhibited in production, can reconstruct some defected immunefunctions or stimulate their recovering capability, so that it can correct the immuneimbalance. However, this speculation is not explicit, making it a necessity to furtherthe study of considering cytokines as adjuvant therapy for HIV-1infection andadjuvant drugs of vaccines.Recent studies have shown that interleukin-15is a potential cytokine ofanti-HIV-1infection. In the peripheral blood mononuclear cells, IL-15can increasethe IFN-γ production, activate and induce the proliferation of T, B and NK cell, andenhance the cytolytic activity of CD8+T cells, and it is also a key cytokine ingenerating and maintaining CD8+T cell memory.In HIV-infected patients, IL-15isfound to promote lymphocytes in the peripheral blood by producing high levels ofIFN-γand some chemokines which can induce the proliferation of B cells and CD8+cytotoxic T lymphocyte (CTL). Some studies have also shown that IL-15expressionplasmid in combination with HIV-1gag DNA vaccine can significantly enhance thesecretion of IFN-γ by CD8+and CD4+T cells, and promote lymphocyteproliferation. Therefore, it is important to conduct a research on the influence ofexogenous cytokines IL-15on the immune response of HIV-1infected cells.IL-21is known as a modulator of lymphoid proliferation, differentiation andapoptosis. It is a multifunctional and pleiotropic cytokine with significantimmune-enhancing and immune regulation function. Produced by CD4+T cells, IL-21is can directly affect the CD8+T cells accelerate the proliferation and antigen-specificCD8+cytolytic T cell function, and strengthen the anti-virus function of cytotoxicCD8+T cells.A study has reported that peripheral blood lymphocytes and IL-21co-cultured in vitro, can enhance the role of CD8+cytolytic T cells. Another study hasfound that IL-21can stimulate NK cells and T cells to secrete IFN-γand inducetheir proliferation and cytotoxic activity.IL-21can facilitate the conversion of CD4+Tcells into the original Th17cells,inducing inflammation and controlling the attack ofpathogens. Our previous studies have shown that the level of IL-21in HIV-1infectedpersons is lower than normal ones, Therefore, a study is necessary to be conducted onthe influence of exogenous cytokines IL-21on the immune response of HIV-1 infected cells.In the first part, the object was49HIV/AIDS-infected patients in southern area ofChina, including21HIV/AIDS-infected patients who were all treated by highly activeanti-retroviral therapy(HAART) and28HIV/AIDS-infected ones without treatment.The changes of CD45RO, CD38and intracellular cytokines IL-17A, IFN-γoflymphocytes in PBMC from the object were assessed by stimulation with12syntheticspecific peptides of amino acid sequences encoding HIV-1P24region, in whichexogenous cytokine IL-15or IL-21was added respectively, by using fluorescent dyestaining and flow cytometry. The data was then analyzed by statistical methods.In the second part, the object was24HIV/AIDS-infected patients all treated byHAART and28HIV/AIDS-infected ones without treatment. The proliferationpercentage of lymphocytes in PBMC from25cases of HIV/AIDS-infected individualswere assessed by stimulation with12synthetic specific peptides of amino acidsequences encoding HIV-1P24region, in which exogenous cytokine IL-15orIL-21was added respectively，by using Carboxy-fluorescein diacetate, succinimidylester (CFSE) labeling and flow cytometry. The data was then treated by statisticalmethods.In the third part, HIV-1specific CTL response intensity of lymphocytes in PBMCfrom16cases with HAART and15cases with HAART-na ve of HIV/AIDS-infectedindividuals were assessed by stimulation with12synthetic specific peptides of aminoacid sequences encoding HIV-1P24region, in which exogenous cytokine IL-15orIL-21was added respectively，by using the method of enzyme-linked immunosorbentspot (ELISPOT).The data was then analyzed by statistical methods.The main research contents and results are as follows:1. Comparison of the changes of CD45RO, CD38and intracellular cytokines IL-17A, IFN-γ in HAART group and HAART-naive group inter groups andwithin group under different stimulating conditionsAfter cell culture with12synthetic specific peptides of amino acid sequencesencoding HIV-1P24region, the ratio of IL-17A, IFN-γ in intracellular cytokineswas significantly higher than that after cell culture with exogenous cytokine IL-15orIL-21stimulation (P<0.05). In the HAART group, after cell culture with exogenouscytokine IL-15stimulation, the proportions of CD4+CD45RO+、CD8+CD45RO+、CD4+CD38+、CD8+CD38+T cell were significantly higher than that after cell culturewith the epitopes in the regions of HIV-1P24（P<0.05）; after cell culture withexogenous cytokine IL-21stimulation, the proportion of the four cells washigher than that after cell culture with the epitopes in the regions of HIV-1P24, butthe proportion of CD8+CD45RO+T cell was not of statistical significance（P＞0.05）.In the HAART-naive group, after cell culture with exogenous cytokine IL-15stimulation, the proportion of the four cells was higher than that after cell culturewith the epitopes in the regions of HIV-1P24, but the proportion of CD4+CD38+Tcell was not statistically significant（P＞0.05）; after cell culture with exogenouscytokine IL-21stimulation, the proportion of the four cells was higher than that aftercell culture with the epitopes in the regions of HIV-1P24, but the differencebetween the proportions of CD4+CD45RO+、CD4+CD38+T cell was not of statisticalsignificance（P＞0.05）. When HAART group was compared with HAART-naivegroup, the difference between the proportions of CD4+CD45RO+T cell in the fourcells was statistically significant（P<0.05）after cell culture with exogenous cytokineIL-15stimulation, and the difference between the proportion of CD4+CD45RO+、CD4+CD38+、CD8+CD38+T cell in the four cells was of statistical significance（P<0.05）after cell culture with exogenous cytokine IL-21stimulation.2. Comparison of T lymphocytes proliferation in HAART group andHAART-naive group between groups and within groups under differentstimulating conditions After cell culture with exogenous cytokine IL-15or IL-21stimulation, theproportion of CD4+and CD8+T lymphocytes proliferation was significantlyhigher than that after cell culture with the epitopes in12synthetic specificpeptides of amino acid sequences encoding HIV-1P24region. The proportion ofCD4+and CD8+T lymphocytes proliferation after cell culture with exogenous cytokineIL-15stimulation was higher than that after cell culture with exogenous cytokineIL-21stimulation, but the difference was not of statistical significanc（eP>0.05）. Aftercell culture with exogenous cytokine IL-15or IL-21stimulation, compared HAARTgroup with HAART-naive group, the difference of the proportions of CD4+Tlymphocytes proliferation was not statistical significance （P>0.05）,and theproportions of CD4+T lymphocytes proliferation of HAART group were significantlyhigher than HAART-naive group（P<0.05）.3. Comparison of HIV-1specific CTL response intensity in HAART groupand HAART-naive group between groups and within groups under differentstimulating conditionsAfter cell culture with exogenous cytokine IL-15or IL-21stimulation,HIV-1specific CTL response intensity was significantly higher than that after cellculture with12synthetic specific peptides of amino acid sequences encoding HIV-1P24region(P<0.05).HIV-1specific CTL response intensity after cell culture withexogenous cytokine IL-15stimulation was significantly higher than that after cellculture with exogenous cytokine IL-21stimulation(P<0.05). HIV-1specificCTL response intensity of HAART group after cell culture with exogenous cytokineIL-15or IL-21stimulation was significantly higher than HAART-naive group（P<0.05）.Conclusions:1. Exogenous cytokine IL-15or IL-21promoted the production of intracellularcytokines IL-17A, IFN-γ by T lymphocytes in HIV/AIDS infected persons,enhanced the expression of HIV-1-infected CD38T-cell activating factor, andinduced the transformation of CD45RO in memory T cell of HIV/AIDS-infected patients.2. Exogenous cytokines IL-15, IL-21promoted the proliferation of T lymphocytesin HIV/AIDS-infected individuals, and the proliferative effect of CD8+Tlymphocytes caused by both exogenous cytokines in HAART infectedindividuals was significantly greater than the HIV/AIDS-infected individualswho had not HAART.3. Exogenous cytokines IL-15, IL-21promoted HIV-1specific CTL response, byenhancing its intensity. By comparing the promotive functions on the intensity ofHIV-1specific CTL response by both exogenous cytokines inHIV/AIDS-infected individuals, the effect in individuals infected with HAARTwas significantly greater than those without HAART infection.