Objective: To evaluate the effects of immunization with a DNA-hsp65 vaccine in an experimental model of pulmonary fibrosis. Methods: A total of 120 male C57BL/6 mice were distributed into four groups: SS, injected with saline (placebo) and then receiving intratracheal (IT) instillation of saline; SB, injected with saline (placebo) and then receiving IT instillation of bleomycin; PB, treated with plasmid only, without bacterial genome, and then receiving IT instillation of bleomycin; and BB, treated with the vaccine and then receiving IT instillation of bleomycin. Bleomycin was instilled 15 days after the last immunization, and the animals were killed six weeks thereafter. The left and right lungs were removed, the former for morphological analysis and the latter for hydroxyproline measurements. Results: The proportion of deaths within the first 48 h after the IT instillation (deaths attributed to the surgical procedure) was higher in the SB group than in the SS group (57.7% vs. 11.1%). The mean area of pulmonary interstitial septa was greater in the SB and PB groups (53.1 ± 8.6% and 53.6 ± 9.3%, respectively) than in the SS and BB groups (32.9 ± 2.7% and 34.3 ± 6.1%, respectively). The mean area of interstitial septa stained by picrosirius was greater in the SB, PB and BB groups than in the SS group (8.2 ± 4.9%, 7.2 ± 4.2% and 6.6 ± 4.1%, respectively, vs. 2.0 ± 1.4%). The total hydroxyproline content in the lung was significantly lower in the SS group (104.9 ± 20.9 pg/lung) than in the other groups (SB: 160.4 ± 47.8 pg/lung; PB: 170.0 ± 72.0 pg/lung; and BB: 162.5 ± 39.7 pg/lung). Conclusions: Immunization with the DNA-hsp65 vaccine reduced the deposition of noncollagen matrix in a model of bleomycin-induced lung lesion.

Keywords: Pulmonary fibrosis; Bleomycin; Collagen.

The DNA vaccines currently under pre-clinical and clinical development may prove to be important tools in combating infectious diseases, such as tuberculosis, for which no safe and effective form of prevention has yet been developed. In recent years, several studies have aimed to develop a DNA vaccine encoding mycobacterial proteins such as antigen 85 (Ag85) and the 65-kDa mycobacterial heat shock protein (hsp65). The latter is protective against virulent infection with Mycobacterium tuberculosis (including multidrugresistant strains). The hsp65 DNA vaccine, currently under clinical evaluation in Brazil for cancer therapy, is able to induce the secretion of Th1 cytokines, such as gamma-interferon, associated with disease control. Furthermore, this vaccine stimulates cytotoxic CD8 and CD4 T-cell clones that can be characterized as memory cells, which are responsible for effective and longlasting immunity against tuberculosis. When used as a therapeutic agent in inoculated mice, the hsp65 DNA vaccine promotes changes in the immunity profile, triggering the secretion of Th1 cytokines and establishing a favorable environment for the elimination of bacilli. The results also demonstrate that the route of administration, as well as the formulation in which the vaccine is administered, fundamentally influence the pattern and duration of the immune response induced. Taking all currently available data into account, we can conclude that a DNA vaccine against tuberculosis could contribute significantly to the control of the disease.

Keywords: Tuberculosis/epidemiology. Vaccines, DNA/therapeutic use. Heat shock proteins. Auto-immunity.