Prophylactic Active Tau Immunization Leads to Sustained Reduction in Both Tau and Amyloid-β Pathologies in 3xTg Mice - PubMed (original) (raw)

Prophylactic Active Tau Immunization Leads to Sustained Reduction in Both Tau and Amyloid-β Pathologies in 3xTg Mice

Hameetha Rajamohamedsait et al. Sci Rep. 2017.

Abstract

Amyloid-β (Aβ) and tau pathologies are intertwined in Alzheimer's disease, and various immunotherapies targeting these hallmarks are in clinical trials. To determine if tau pathology influences Aβ burden and to assess prophylactic benefits, 3xTg and wild-type mice received tau immunization from 2-6 months of age. The mice developed a high IgG titer that was maintained at 22 months of age. Pronounced tau and Aβ pathologies were primarily detected in the subiculum/CA1 region, which was therefore the focus of analysis. The therapy reduced histopathological tau aggregates by 70-74% overall (68% in males and 78-86% in females), compared to 3xTg controls. Likewise, western blot analysis revealed a 41% clearance of soluble tau (38-76% in males and 48% in females) and 42-47% clearance of insoluble tau (47-58% in males and 49% in females) in the immunized mice. Furthermore, Aβ burden was reduced by 84% overall (61% in males and 97% in females). These benefits were associated with reductions in microgliosis and microhemorrhages. In summary, prophylactic tau immunization not only prevents tau pathology but also Aβ deposition and related pathologies in a sustained manner, indicating that tau pathology can promote Aβ deposition, and that a short immunization regimen can have a long-lasting beneficial effect.

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Conflict of interest statement

E.M.S. is an inventor on patents on tau immunotherapy and related diagnostics that are assigned to New York University. This technology is licensed to and is being co-developed with H. Lundbeck A/S.

Figures

Figure 1

Figure 1

The tau immunogen Tau379–408[P-Ser396, 404] elicits a robust and sustained antibody response. (A–C) IgG response towards the immunogen was strong and long-lasting, and comparable in males vs. females. It was strong at T1 (1 week after the 3rd immunization), peaked at T2 (2 months after the 4th and last immunization) and remained strong thereafter (T3-Tf: 5, 8, 11, and 16 months after the 4th immunization). Higher IgG levels were detected in wt mice compared to 3xTg mice. (D–F) IgM response was not as strong as the IgG response but showed a similar pattern as the IgG response except that the IgM response was comparable in the wt vs. the 3xTg mice. (G,H) Plasma (1:100) obtained from a high titer mouse at the end of the study (Tf) stained tau aggregates in a control 3xTg mouse, whereas plasma from a low titer control mouse did not. Scale bar: 125 μm.

Figure 2

Figure 2

Tau immunization prevents phospho-tau histopathology. (A–D) PHF1 immunostaining revealed extensive tau pathology in the hippocampus (A: 5X objective, B: 20X objective) of 3xTg mice, that was greatly reduced in immunized mice (C,D). (E–H) Only background staining was seen in the wt mice. (I–K) Quantitative analysis of the PHF1 staining revealed significant reduction in tau aggregates in the combined group (I: 74%, p = 0.0008) as well as in males (J: 68%, p = 0.0437) and females (K: 78%, p = 0.0120) analyzed separately. Scale bar: 250 μm (A), 125 µm (B). *p < 0.05; ***p < 0.001 compared to 3xTg control. See text for exact p-values.

Figure 3

Figure 3

Tau immunization prevents conformational tau histopathology. (A–D) MC1 immunostaining revealed extensive tau pathology in the hippocampus (A: 5X objective, B: 20X objective) of 3xTg mice, that was greatly decreased in immunized 3xTg mice (C-D). (E–H) Only background staining was seen in the wt mice. (I–K) Quantitative analysis of the MC1 staining revealed significant reduction in tau aggregates in the combined group (I: 70%, p = 0.0057) as well as in females (K: 86%, p = 0.0070). Scale bar: 250 μm (A), 125 µm (B). **p < 0.01 compared to 3xTg control. See text for exact p-values.

Figure 4

Figure 4

Tau immunization decreases soluble and insoluble human tau protein. (A,B) Representative blots are shown in A. Note that lanes that appear empty are from mice that did not express human tau and were, therefore, omitted from all analysis. Western blot analysis revealed that soluble and insoluble CP27-reactive human tau were reduced in the immunized 3xTg mice (soluble tau: 41%, p = 0.0103; insoluble tau: 47%, p = 0.0008). (C–F) Comparable tau reductions were observed in males (soluble tau: 38%, p = 0.0322; insoluble tau: 47%, p = 0.0165) vs. females (soluble tau: 48%, p = 0.0616; insoluble tau: 49%, p = 0.0477). *p < 0.05; **p < 0.01; ***p < 0.001 compared to 3xTg control. See text for exact p-values.

Figure 5

Figure 5

Tau immunization reduces soluble and insoluble phospho-tau protein. (A,B) Representative blots are shown in A. Western blot analysis revealed that insoluble PHF1-reactive human tau was decreased in the immunized 3xTg mice (42%, p = 0.0003). (C,D) Both soluble (76%, p = 0.0001) and insoluble tau (58%, p = 0.0018) were decreased in the males but not in the females (E,F). **p < 0.01; ***p < 0.001 compared to 3xTg control. See text for exact p-values.

Figure 6

Figure 6

Tau immunization diminishes Aβ burden. (A–D) Aβ immunostaining revealed extensive Aβ plaque burden in subiculum region of the hippocampus (A: 5X objective, B: 20X objective) of 3xTg mice, that was greatly reduced in immunized mice (C,D). (E–H) Only background staining was seen in the wt mice. (I–K) Quantitative analysis of the Aβ staining revealed significant reduction in Aβ plaque burden in the combined group (I: 84%, p < 0.0001) as well as in males (J: 61%, p = 0.0033) and females (K: 97%, p = 0.0001) analyzed separately. Scale bar: 250 μm (A), 125 µm (B). **p < 0.01; ****p < 0.0001 compared to 3xTg control. See text for exact p-values.

Figure 7

Figure 7

3xTg mice have more astrogliosis than wt mice. (A–D) GFAP immunostaining revealed extensive astrogliosis in subiculum region of the hippocampus (A: 5X objective, B: 10X objective) of 3xTg mice, that was much less in WT mice (C,D). Scale bar: 250 μm.

Figure 8

Figure 8

3xTg mice have more astrogliosis than wt mice. (A–C) Semi-quantitative analysis of GFAP immunoreactivity in the subiculum revealed that 3xTg mice had more astrogliosis than wt mice (p = 0.0139) that was also significantly increased in the males (p = 0.0286). However, astrogliosis was not significantly affected by the tau immunotherapy in the combined group (A) or in the males (B) and females (C) analyzed separately. #p < 0.05 compared to wt control. See text for exact p-values.

Figure 9

Figure 9

Tau immunization reduces microgliosis in 3xTg mice to wt levels. (A–F) Iba1 immunostaining revealed extensive microgliosis in the subiculum region of the hippocampus in 3xTg mice (A: 5X objective; B: 10X objective) that was greatly reduced in tau immunized mice (C,D) rendering these animals indistinguishable from wt mice (E,F). Scale bar: 250 μm.

Figure 10

Figure 10

Tau immunization reduces microgliosis in 3xTg mice to wt levels. (A–C) Semi-quantitative analysis of Iba1 immunoreactivity in the subiculum revealed that 3xTg mice had more microgliosis than wt mice (males and females: p = 0.0013; males: p = 0.0286; females: p = 0.0310), and the tau immunotherapy reduced microgliosis in 3xTg mice to wt levels (males and females: p = 0.0056; males: p = 0.0699; females: p = 0.0294). #p < 0.05; ##p < 0.01 compared to wt control. *p < 0.05; **p < 0.01 compared to 3xTg control. See text for exact p-values.

Figure 11

Figure 11

Tau immunization diminishes microbleeds in 3xTg mice to wt levels. (A–D) A few microbleeds (blue) were primarily detected in the hippocampus (A: 20X objective) of the 3xTg control mice (males and females: p = 0.0088 compared to wt control; females: p = 0.0165), and their numbers were significantly reduced in the tau immunized 3xTg mice (males and females: p = 0.0095; females: p = 0.0078) to wt levels. Scale bar: 125 μm. #p < 0.05; ##p < 0.01 compared to wt control. **p < 0.01 compared to 3xTg control. See text for exact p-values.

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