Bhattacharya Parna, Dey Ranadhir, Dagur Pradeep K, Joshi Amritanshu B, Ismail Nevien, Gannavaram Sreenivas, Debrabant Alain, Akue Adovi D, KuKuruga Mark A, Selvapandiyan Angamuthu, McCoy John Philip, Nakhasi Hira L
Division of Emerging and Transfusion Transmitted Disease, Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland, United States of America.
Flow Cytometry Core, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland, United States of America.
PLoS Negl Trop Dis. 2016 Aug 31;10(8):e0004963. doi: 10.1371/journal.pntd.0004963. eCollection 2016 Aug.
Visceral leishmaniasis (VL) caused by the protozoan parasite Leishmania donovani causes severe disease. Age appears to be critical in determining the clinical outcome of VL and at present there is no effective vaccine available against VL for any age group. Previously, we showed that genetically modified live attenuated L. donovani parasites (LdCen-/-) induced a strong protective innate and adaptive immune response in young mice. In this study we analyzed LdCen-/- parasite mediated modulation of innate and adaptive immune response in aged mice (18 months) and compared to young (2 months) mice.
Analysis of innate immune response in bone marrow derived dendritic cells (BMDCs) from both young and aged mice upon infection with LdCen-/- parasites, showed significant enhancement of innate effector responses, which consequently augmented CD4+ Th1 cell effector function compared to LdWT infected BMDCs in vitro. Similarly, parasitized splenic dendritic cells from LdCen-/- infected young and aged mice also revealed induction of proinflammatory cytokines (IL-12, IL-6, IFN-γ and TNF) and subsequent down regulation of anti-inflammatory cytokine (IL-10) genes compared to LdWT infected mice. We also evaluated in vivo protection of the LdCen-/- immunized young and aged mice against virulent L. donovani challenge. Immunization with LdCen-/- induced higher IgG2a antibodies, lymphoproliferative response, pro- and anti-inflammatory cytokine responses and stimulated splenocytes for heightened leishmanicidal activity associated with nitric oxide production in young and aged mice. Furthermore, upon virulent L. donovani challenge, LdCen-/- immunized mice from both age groups displayed multifunctional Th1-type CD4 and cytotoxic CD8 T cells correlating to a significantly reduced parasite burden in the spleen and liver compared to naïve mice. It is interesting to note that even though there was no difference in the LdCen-/- induced innate response in dendritic cells between aged and young mice; the adaptive response specifically in terms of T cell and B cell activation in aged animals was reduced compared to young mice which correlated with less protection in old mice compared to young mice.
Taken together, LdCen-/- immunization induced a significant but diminished host protective response in aged mice after challenge with virulent L. donovani parasites compared to young mice.
由原生动物寄生虫杜氏利什曼原虫引起的内脏利什曼病（VL）会导致严重疾病。年龄似乎在决定VL的临床结果方面至关重要，目前尚无针对任何年龄组的有效VL疫苗。此前，我们发现基因改造的减毒活杜氏利什曼原虫寄生虫（LdCen-/-）在幼鼠中诱导了强烈的保护性先天和适应性免疫反应。在本研究中，我们分析了LdCen-/-寄生虫介导的老年小鼠（18个月）先天和适应性免疫反应的调节，并与年轻小鼠（2个月）进行了比较。
分析来自年轻和老年小鼠的骨髓来源树突状细胞（BMDCs）在感染LdCen-/-寄生虫后的先天免疫反应，结果显示先天效应反应显著增强，因此与体外感染LdWT的BMDCs相比，CD4+ Th1细胞效应功能增强。同样，与感染LdWT的小鼠相比，来自LdCen-/-感染的年轻和老年小鼠的寄生脾树突状细胞也显示促炎细胞因子（IL-12、IL-6、IFN-γ和TNF）的诱导以及抗炎细胞因子（IL-10）基因的随后下调。我们还评估了LdCen-/-免疫的年轻和老年小鼠对强毒杜氏利什曼原虫攻击的体内保护作用。用LdCen-/-免疫诱导了更高的IgG2a抗体、淋巴细胞增殖反应、促炎和抗炎细胞因子反应，并刺激脾细胞增强与一氧化氮产生相关的杀利什曼活性，在年轻和老年小鼠中均如此。此外，在受到强毒杜氏利什曼原虫攻击后，两个年龄组的LdCen-/-免疫小鼠均表现出多功能Th1型CD4和细胞毒性CD8 T细胞，与未免疫小鼠相比，脾和肝中的寄生虫负荷显著降低。有趣的是，尽管老年和年轻小鼠的树突状细胞中LdCen-/-诱导的先天反应没有差异；但与年轻小鼠相比，老年动物中特别是T细胞和B细胞活化方面的适应性反应有所降低，这与老年小鼠比年轻小鼠的保护作用较小相关。
综上所述，与年轻小鼠相比，用LdCen-/-免疫的老年小鼠在受到强毒杜氏利什曼原虫攻击后诱导了显著但减弱的宿主保护反应。
