1型和2型外壳蛋白构建的AAV载体携带HIV-1 gag诱导免疫反应的比较研究

Immune Responses Induced by Intramuscular Vaccination with rAAV2 and Pseudotyped rAAV1 Expressing HIV-1 gag

比较两种血清型的腺病毒伴随病毒(Adeno-associated virus,AAV)载体携带HIV-1gag基因肌肉注射诱导小鼠免疫反应的特点。分别制备携带EGFP和HIV-1gag基因的重组AAV2/1(AAV1)和AAV2载体。小鼠肌肉注射rAAV1-EGFP和rAAV2-EGFP,观察注射局部EGFP的表达。将rAAV1-gag和rAAV2-gag分别以0、3周初免/加强方式肌肉注射免疫BALB/c小鼠以及新西兰白兔。ELISA法检测抗HIV-1 Gag P24蛋白的特异性抗体,细胞内细胞因子染色法检测Gag特异性的CTL反应。结果表明,rAAV1-EGFP在小鼠肌肉的表达强度显著高于rAAV2-EGFP;用Western blot法和间接免疫荧光法检测rAAV1-gag和rAAV2-gag体外转染的293细胞,均可检测到HIV-1 Gag蛋白的表达;在小鼠体内rAAV1-gag和rAAV2-gag组均可检测到特异性P24抗体,抗体滴度rAAV1-gag组显著高于rAAV2-gag组;而无论rAAV1-gag组还是rAAV2-gag组,特异性CTL反应均较低,与阴性对照组相比均无显著性差异;两种载体免疫兔子也都可检测到特异性P24抗体,同样地,rAAV1-gag组显著高于rAAV2-gag组。结论:携带HIV-1gag基因的rAAV1或rAAV2以肌肉注射方式免疫小鼠主要诱导特异Gag的体液免疫反应;且rAAV1可诱导很强的抗HIV-1 Gag特异性抗体,抗体水平显著高于rAAV2。

Immune responses against HIV-1 Gag resulting from recombinant adeno-associated virus serotype 2 （rAAV2-gag） and pseudotyped AAV1 （rAAVl-gag） by intramuscular vaccination were compared. At first, BALB/c mice were inoculated with 1 × 10^11 vg of AAV1-EGFP and AAV2-EGFP respectively. The expression of EGFP in muscle was detected under the long wavelenth UV lamp. Secondly, the codon-optimized HIV-1 gag gene was used to construct rAAV1-gag and rAAV2-gag. Gag expression was detected by indirect immunofluorescence assay and Western blot. BALB/c mice and rabbits were immunized with rAAV2-gag and rAAV1-gag in prime/boost scheme at week 0 and 3. The serum specific P24 IgG against HIV-1 Gag was detected by ELISA. Anti-Gag CTL response was detected by intracellular cytokine staining assay. The results showed that the level of EGFP expression was higher in BALB/c mice injected with rAAV1-EGFP than with rAAV2-EGFP. Gag expression was detectable in cultured cells infected with both rAAV2-gag and rAAV1-gag. Significantly higher level of anti-Gag IgG in serum was detectable in BALB/c mice and rabbits immunized with rAAVl-gag than that of animals immunized with rAAV2-gag. However, anti-Gag CTL responses in BALB/c mice were undetectable either with rAAV1-gag or with rAAV2-gag. The experiments suggested that rAAV1 and rAAV2 carrying HIV- 1 gag mainly elicited humoral rather than cellular immune response, and rAAVl-gag elicited significantly higher level of anti-Gag IgG than rAAV2-gag in both BALB/c mice and rabbits.