Preventive effects of Mycobacterium tuberculosis DNA vaccines on the mouse model with latent tuberculosis infection

Abstract

BackgroundAbout a quarter of the world’s population with latent tuberculosis infection (LTBI) are the main source of active tuberculosis. Bacillus Calmette Guerin (BCG) cannot effectively control LTBI individuals from developing diseases. Latency-related antigens can induce T lymphocytes of LTBI individuals to produce higher IFN-γ levels than tuberculosis patients and normal subjects. Herein, we firstly compared the effects of M. tuberculosis (MTB) ag85ab and 7 latent DNA vaccines on clearing latent MTB and preventing its activation in the mouse LTBI model.MethodsA mouse LTBI model was established, and then immunized respectively with PBS, pVAX1 vector, Vaccae vaccine, ag85ab DNA and 7 kinds of latent DNAs (including rv1733c, rv2660c, rv1813c, rv2029c, rv2628, rv2659c and rv3407) for three times. The mice with LTBI were injected with hydroprednisone to activate the latent MTB. Then, the mice were sacrificed for the bacterial count, histopathological examination, and immunological evaluation.ResultsUsing chemotherapy made the MTB latent in the infected mice, and then using hormone treatment reactivated the latent MTB, indicating that the mouse LTBI model was successfully established. After the mouse LTBI model was immunized with the vaccines, the lung colony-forming units (CFUs) and lesion degree of mice in all vaccines group were significantly decreased than those in the PBS group and vector group (P<0.0001, P<0.05). These vaccines could induce antigen-specific cellular immune responses. The number of IFN-γ effector T cells spots secreted by spleen lymphocytes in the ag85ab DNA group was significantly increased than those in the control groups (P<0.05). In the splenocyte culture supernatant, IFN-γ and IL-2 levels in the ag85ab, rv2029c, and rv2659c DNA groups significantly increased (P<0.05), and IL-17A levels in ag85ab and rv2659c DNA groups also significantly increased (P<0.05). Compared with the PBS and vector groups, the proportion of CD4+CD25+FOXP3+ regulatory T cells in spleen lymphocytes of ag85ab, rv2660c, rv2029c, and rv3407 DNA groups were significantly reduced (P<0.05).ConclusionsMTB ag85ab and 7 kinds of latent DNA vaccines showed immune preventive efficacies on a mouse model of LTBI, especially the rv2659c, and rv1733c DNA. Our findings will provide candidates for the development of new multi-stage vaccines against TB.

Bioinformatics analysis and immunogenicity assessment of the novel multi-stage DNA vaccine W541 against Mycobacterium tuberculosis

“…Reece et al engineered therv3407 gene into the BCG vaccine and immunized mice with the recombinant BCG vaccine, and found that this modified BCG vaccine stimulated high levels of IFN-γ production in mice and markedly enhanced protection against TB (30). Our research group also found through animal experiments that the mice immunized with the rv3407 DNA vaccine could produce higher levels of antigen-specific IFN-γ in the culture supernatant of splenic lymphocytes, had more Th1 cells and an increased Th1/Th2 cells ratio in the whole blood, could reduce the bacterial load in the lungs of mouse models with acute infection or LTBI, and alleviate the degree of lung lesions (31,32).…”

“…Mice were divided into three groups (8 mice per group) and treated as follows: 1) Control group: each mouse was injected intramuscularly with 100 μl of saline; 2) pVAX1 group: each mouse was injected intramuscularly with 100 μg pVAX1 plasmid diluted in 100 μl saline; 3) Vaccine group: each mouse was injected intramuscularly with 100 μg W541 DNA vaccine diluted in 100 μl saline (32). Mice received injections every two weeks for a total of 3 injections.…”

“…Zhang W et al immunized mice with a DNA vaccine encoding Rv1733cand exhibited higher splenocyte stimulation index and IFN-γ, IL-2, and IL-4 levels than those injected with saline (34). Our research group used animal experiments to compare the preventive and therapeutic effects of MTB ag85ab and 7 types of LTBI DNA vaccines on a mouse LTBI model, and it showed that the ag85ab, rv2659c , andrv1733c DNA vaccines reduced the bacterial load and degree of lung lesions in the mouse LTBI model (32). Additionally, Coppola M et al immunized mice with synthetic Rv1733c long peptides (28 amino acid sequences located at positions 57-84, IPFAAAAGTAVQDSRSHVYAHQAQTRHP) and exhibited significantly increased expression of IFN-γ, TNF-α, and specific antibody, and reduced the pulmonaryM.tb load.…”

Optimizing antigen selection for the development of tuberculosis vaccines

“…Furthermore, clinical studies have demonstrated that using Vaccae™ as an adjunctive immunotherapy, significantly enhances the sputum smear negative conversion rate (68%), facilitates lesion improvement, and cavity closure, shortens treatment duration, and mitigates chemotherapy-related damage ( Bourinbaiar et al., 2020 ; Yang et al., 2011 ). As a prophylactic vaccine, Vaccae™ can effectively suppress the proliferation and activation of Mtb , hinder the progression of LTBI, and decrease the rate of infection ( Liang et al., 2023 ; Sun ZhaoPing et al., 2013 ).…”

Advances in understanding immune homeostasis in latent tuberculosis infection

“…Liang et al employed a drug‐activated mouse LTBI animal model to evaluate the protective effects of a DNA vaccine constructed with Mtb ag85ab and seven latency‐associated antigens (rv1733c, rv2660c, rv1813c, rv2029c, rv2628, rv2659c, rv3407). They found that antigens rv2659c and rv1733c could significantly enhance the protective efficacy in LTBI mice (Liang et al, 2023).…”