Activation of transgene-specific T cells following lentivirus-mediated gene delivery to mouse lung

Abstract

Integrating lentiviral vectors based on the human immunodeficiency virus type-1 (HIV-1) can transduce quiescent cells, which in lung account for almost 95% of the epithelial cell population. Pseudotyping lentiviral vectors with the envelope glycoprotein from the Ebola Zaire virus, the lymphocytic choriomeningitis virus (LCMV), the Mokola virus, and the vesicular stomatitis virus (VSV-G) resulted in transduction of mouse alveolar epithelium, but gene expression in the lung of C57BL/6 and BALB/c mice waned within 90 days of vector injection. Intratracheal delivery of the four pseudotyped lentiviral vectors resulted in transgene-specific T-cell activation in both mouse strains, albeit lower than that achieved by intramuscular injection of the vectors. We performed an adoptive transfer of luciferase-specific T cells, isolated from spleen or lung of donor mice injected with VSV-G-pseudotyped lentivirus vector expressing luciferase into the muscle or lung, respectively, into recipient recombination-activating gene (RAG)-deficient mice transduced in lung with adenovirus expressing firefly luciferase (ffluc2). Gene expression declined within 7 days of adoptive transfer approaching background levels by day 36. Taken together, our results suggest that the loss of transduced cells in lung is due to VSV-G.HIV vector-mediated activation of transgene-specific T cells rather than as result of normal turnover of airway cells.

Figure 1

GFP gene expression in lung of C57BL/6 and BALB/c mice and subsequent activation of GFP-specific T cells. (a) Representative images of vector-transduced mouse lung from C57BL/6 mice harvested at day 21 and (b) Quantitation of GFP-expressing cells. NTDL6- and VSV-G-pseudotyped vectors were the most efficient vectors at transducing the alveolar epithelium, followed by the Mokola- and LCMV-pseudotyped vectors. (c) Following intratracheal (i.t.) injection only the VSV-G-pseudotyped vector activated GFP-specific and vector-specific T cells. (d) Following intramuscular (i.m.) injection of C57BL/6 mice all four vectors activated significant frequencies of GFP-specific T cells. Interestingly, gag-specific T cells were only observed in C57BL/6 mice injected with the VSV-G-pseudotyped lentivirus vector. (e) Representative images of vector-transduced mouse lung from BALB/c mice harvested at day 21 and (f) Quantitation of GFP-expressing cells. The NTDL6-pseudotyped vector was the most efficient at transducing the alveolar epithelium followed by the LCMV-, Mokola-, and VSV-G-pseudotyped lentiviral vectors. (g) In BALB/c mice, when the pseudotyped lentiviral vectors were injected i.t. there was significant activation of GFP-specific T cells. (h) Following i.m. injection of the four vectors in BALB/c mice a significant GFP-specific T-cell activation was observed for all vectors. T-cell activation was quantified and presented as SFU/10⁶ cells. Results presented are the average of n = 4 ± SD (error bar)*P < 0.05, analysis of variance, Student–Newman–Keuls test. Bar = 100 µm. SFU, spot forming units.

Figure 2

GFP expression in mouse lung and activation of GFP-specific T cells. (a) VSV-G-pseudotyped lentivirus vector was injected i.t. to C57BL/6 mouse lung at day 0. At day 7 GFP-mediated gene expression was observed in the cells of the alveolar epithelium the numbers of which remained stable to day 42. There was a significant decrease in GFP-expressing cells at day 90. (b) GFP-specific T-cell activation was observed at day 7 and remained stable through day 90, with the exception of day 42 in which T-cell activation increased, although not significantly. (c) Vector was delivered to RAG-deficient/C57BL/6 and C57BL/6 mouse lung and GFP expression assessed at days 21 and 90. GFP expression in RAG-deficient/C57BL/6 mice remained stable while for C57BL/6 mice a significant decrease in GFP-expressing cells was observed at day 90. (d) At day 7 after i.t. injection of vector to BALB/c mouse lung only low numbers of GFP-expressing cells were observed in the alveolar epithelium which significantly decreased at day 90. (e) GFP-specific T-cell activation in BALB/c mouse lung was observed at day 7 that increased at day 21 and remained stable through to day 90. T-cell activation was quantified and presented as SFU/10⁶ cells. Results presented are the average of n = 4 ± SD (error bar)* P < 0.05, analysis of variance, Student–Newman–Keuls test, n = 4. **P = 0.02, Student's t-test, n = 5. GFP, green fluorescence protein; SFU, spot forming units.

Figure 3

Impact on ffluc2 expression following adoptive transfer of activated T cells. (a) Schematic diagram of the experimental design. In brief, donor mice consisted of C57BL/6 mice that were injected i.t. or i.m. with either VSVG.HIV.EGFPLuc or Ad.Hu5.ffluc2 vector. Recipient mice were RAG-deficient/C57BL/6 mice that were injected i.n. with Ad.Hu5.ffluc2 vector. At the peak of T-cell activation, lung-lymphocytes and splenocytes were isolated and transferred intravenously (i.v.) to the recipient mice. As controls, RAG-deficient/C57BL/6 mice were i.v. injected with either lung-lymphocytes or splenocytes isolated from naive C57BL/6 mice. Expression of ffluc2 was monitored through to day 36 after adoptive transfer (b) Quantitation (photons/second) of ffluc2 expression before and up to 36 days after adoptive transfer (*P < 0.05, analysis of variance, Student–Newman–Keuls test). DM, donor mice; i.m., intramuscularly; i.n., intranasally; i.t., intratracheally; RM, recipient mice.

Figure 4

Pathology of recipient mouse lung tissue after adoptive transfer of naive or vector-activated lung-lymphocytes or splenocytes. Lungs were harvested and evaluated for signs of cellular infiltration at day 36 after adoptive transfer of (a) naive lung-lymphocytes; (b) VSV-G.HIV.EGFPLuc activated lung-lymphocytes; (c) Ad.Hu5.ffluc2 activated lung-lymphocytes; (d) no adoptive transfer; (e) naive splenocytes; (f) VSV-G.HIV.EGFPLuc activated splenocytes; (g) Ad.Hu5.ffluc2 activated splenocytes; (h) Ad.Hu5.LacZ activated lung-lymphocytes. Representative tissue sections counterstained with hematoxylin and eosin are shown. Bar = 100 µm.