Recombinant adeno-associated virus vectors induce functionally impaired transgene product–specific CD8+ T cells in mice
Shih-Wen Lin, Scott E. Hensley, Nia Tatsis, Marcio O. Lasaro, Hildegund C.J. Ertl
Shih-Wen Lin, Scott E. Hensley, Nia Tatsis, Marcio O. Lasaro, Hildegund C.J. Ertl
View: Text | PDF
Research Article

Recombinant adeno-associated virus vectors induce functionally impaired transgene product–specific CD8+ T cells in mice

Abstract

Recombinant adeno-associated virus (rAAV) vectors were used in human trials as carriers of vaccines for HIV-1 after encouraging preclinical results. However, the clinical trials yielded disappointing results. Here we demonstrated that in mice, rAAV vectors expressing the gene encoding HIV-1 gag stimulated gag-specific CD8+ T cells, but these T cells failed to expand after a booster immunization with a replication-defective adenoviral (Ad) vector also expressing gag. We tested rAAV vectors of different serotypes expressing HIV-1 gag for induction of transgene product–specific CD8+ T cells and found that the immunoinhibitory effect of rAAV priming observed with different AAV serotypes was transgene product specific, was independent of the interval between prime and boost, and extended to boosts with vaccine modalities other than Ad vectors. rAAV vector–induced CD8+ T cells proliferated poorly, produced low levels of IFN-γ in response to gag stimulation, and upregulated immunoinhibitory molecules. These T cells did not protect efficiently against challenge with a surrogate pathogen. Finally, we showed that the impaired proliferative capacity of the T cells was caused by persistence of the antigen-encoding rAAV vectors and could be reversed by placing the CD8+ T cells in an antigen-free environment. Our data suggest that rAAV vectors induce functionally impaired T cells and could dampen the immune response to a natural infection.

Authors

Shih-Wen Lin, Scott E. Hensley, Nia Tatsis, Marcio O. Lasaro, Hildegund C.J. Ertl

×

Figure 7

rAAV vectors increase regulatory cells, which do not cause impairment of the proliferative capacity of rAAV-induced CD8+ T cells.

Options: View larger image (or click on image) Download as PowerPoint
rAAV vectors increase regulatory cells, which do not cause impairment of...
(A and B) BALB/c mice were immunized with 1011 gc rAAV2/7gag and 1 month later boosted with 1010 vp AdC68gag; control mice received rAAV2/7gag or AdC68gag. At 10 days after the boost, splenocytes were analyzed for percentage of CD4+CD25+FoxP3+ cells (A) and CD4+CD25+GITR+ cells (B). (C) Mice immunized with 1011 gc rAAV2/7gag were treated 3 days before the 1010 vp AdC68gag boost with 200 μg antibody to CD25 i.p.; control mice were treated with 200 mg of control antibody. (D) For adoptive transfer, 2 × 106 CD4+, CD8+, B220+, or other cells were sorted from splenocytes of BALB/c mice immunized with 1011 gc rAAV2/7gag 1 month earlier and injected through the tail vein into naive mice. Recipient mice were immunized 1 day later with 1010 vp AdC68gag; control mice did not receive cells but did receive the 1011 gc rAAV2/7gag prime and 1010 vp AdC68gag boost. (E) Serum (200 μl) from naive mice or mice receiving an immunization of 1011 gc rAAV2/7gag was transferred i.v. into naive mice, and then 1 day later recipient mice were immunized with 1010 vp AdC68gag vector; control mice received no serum but were immunized with 1011 gc rAAV2/7gag followed by a 1010 vp AdC68gag boost. At 10 days after the boost, splenocytes were analyzed by ICS. In C–E, frequency of gag-specific IFN-γ–secreting CD8+ T cells is shown. Background values (less than 0.1%) were subtracted prior to plotting. Error bars represent SD for 5 mice.