疫苗佐劑對於具抗原專一性調節性T細胞及宿主的T細胞免疫力之影響

The effects of vaccine adjuvants on influenza antigen-specific regulatory T cell and T cell immunity

謝孟頻(Meng-Ping Hsieh)

指導教授 ： 楊宏志

國立臺灣大學/醫學院/微生物學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.02180

摘要

流行性感冒病毒為流行性感冒的病源，一般可分為A, B, C三型， 而其中的A型流感病毒更因為其流行病學上的特性-抗原漂變(主要造成季節性流感) 和抗原移型 (會造成流感的大流行)而產生出許多不同亞型的流感病毒。
　　目前主要利用流感疫苗來預防流感病毒感染，現行使用的流感疫苗可以分成去活化疫苗與減毒性疫苗兩大類。大部分流感疫苗為去活化疫苗，主要引發體液免疫反應。由於流感病毒的抗原漂變特性，每年會依據前一年流行的亞型預測下一年流感季節的病毒種類並製作新的疫苗，並需重新施打新的流感疫苗來預防，而目前疫苗發展方向便希望能找到一個可以對抗所有亞型流感病毒感染的疫苗
　 過去已經有研究找到抗體可以專一性辨識流感病毒表面抗原的根部或是流感病毒表面較不易產生突變的區域，另外也有研究指出T細胞免疫在對抗造成大流行的流感是重要的，可以保護宿主協助抵抗病毒感染。
　　在影響T細胞免疫的因素中，除了樹突細胞和細胞激素等因子外，有一群細胞稱為調節性T細胞，也會參與在調控T細胞免疫上。調節性T細胞可以分成在胸腺產生且會辨認自體抗原的thymus-derived Treg (tTreg)，以及在周邊的初始T細胞辨識外來抗原活化產生之peripheral-derived Treg(pTreg )。調節性T細胞的功能主要會藉由分泌IL-10和TGF-β或是與其他T細胞爭奪IL-2等不同方式抑制免疫反應。
　　目前的研究指出，當流感病毒感染或是施打流感疫苗時宿主會產生出專一性辨識流感病毒的pTreg，並且使再次感染病毒時的細胞免疫反應被抑制。而已有研究發現在特定的細胞激素刺激下或是在發炎的環境中，已分化的Treg會再轉變成其他的輔助型T細胞。
因此，我們想要藉由施打疫苗，同時將先前感染或施打疫苗時產生的專一性pTreg減少或轉變成其他的輔助型細胞，使宿主的T細胞免疫力提升，進而增加疫苗對抗不同型流感病毒的能力。我們的研究著重在佐劑對於pTreg的影響，佐劑是我們在施打不活化疫苗中除了病原本身的抗原外，額外加入的成分，用以促進免疫反應。一般常用在流感疫苗的佐劑像是鋁鹽、MF59、AS03等，其中像是鋁鹽佐劑可以刺激Th2反應，使施打疫苗後產生的抗體增加等。另外也有許多正在試驗中的佐劑可以藉由刺激類鐸受體增強體液免疫的效用。而在我們的研究中，我們想要測試在施打疫苗時加入不同的佐劑，是否可以藉由這些佐劑去減少施打對象體內已經存在的ｐTreg，進而增加打疫苗所產生的細胞免疫反應。
　　我們的實驗中會使用過繼幸轉移的系統，將OT-II這個會專一性辨識OVA323-339的T細胞受器基因轉殖的CD4+T細胞打入接受者老鼠中，看看在施打疫苗時佐劑對抗原專一性Treg產生的影響。從我們的實驗結果中可以看到不管是在初次施打疫苗或是第二次施打疫苗，老鼠體內的Treg的確會在施打疫苗時產生，其產生的比例受到疫苗裡的佐劑種類所影響，且這些被疫苗所引發出來的Treg具有抑制免疫反應的能力。我們的實驗結果證明不同的佐劑的確可以藉由減少Treg進而增加T細胞免疫力，增強疫苗效果。

關鍵字

佐劑 ； 疫苗 ； 抗原專一性調節性T細胞 ； 流行性感冒病毒

並列摘要

Influenza A virus causes seasonal flu and pandemic because of the antigenic drift and antigenic shift. The inactivated influenza vaccine is the most effective way to prevent influenza virus infection. However, it needs to be reformulated every year and because the induced humoral immunity cannot prevent the host from the pandemic influenza virus infection. Recently, scientists attempt to develop a universal vaccine that can broadly recognize various subtypes of influenza A virus. The neutralizing antibodies specific for the stem of hemagglutinin( HA), the surface antigen of influenza A virus, is one of the universal vaccine candidates. The enhancement of the suppressive T cell immunity also can protect the host against pandemic infection.
Regulatory T cells ( Tregs), have recently CD4 T cell that inhibit immunity, and been shown to be induced by vaccination or virus infection, and convert into other types of T helper T cells( Th) by the pro-inflammatory cytokine milieu.
The vaccine adjuvant plays an important role in vaccination by triggering the antigen-specific immune response and immunogenicity. We attempt to investigate in this study the adjuvants and the potential enhancement of T cell- mediated immunity by diminishing the Treg population via vaccination.
The adoptive transfer experiments were carried out to examine the effect of various adjuvants on influenza vaccine. The OT-II cells were adoptively transferred to the recipient mice, pre-immunized with the adjuvants, to realize the effect of adjuvants by analysis of the immune response after the primary and secondary vaccination. The DEREG( depletion of regulatory T cell) mice were used to confirm the function of the induced Tregs in vivo. Our results showed that the vaccine adjuvants, including CpG(TLR9 ligand), R848(TLR7/8 ligand) and CFA reduced the Treg induction after the primary vaccination; treatment of mice with CpG prevented the expansion of Tregs after the secondary vaccination. The Tregs induced by immunization could inhibit the T cell immunity after the secondary vaccination. Treatment of mice with OVA+CpG reduced the generation of Tregs. In conclusion, we demonstrated that some adjuvants, such as CpG and R848, can be used to reduce Tregs and enhance the T cell immunity.

並列關鍵字

adjuvant ； vaccine ； antigen-specific Treg ； influenza

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