Suppression of the Immune Response Against Tuberculosis by Natural T Regulatory Cells

Truncated chicken MDA5 enhances the immune response to inactivated NDV vaccine

A novel DNA vaccine for protective immunity against virulent Mycobacterium bovis in mice

Codon optimization and woodchuck hepatitis virus posttranscriptional regulatory element enhance the immune responses of DNA vaccines against infectious bursal disease virus in chickens

DNA vaccines represent a novel and powerful alternative to conventional vaccine approaches. They are extremely stable and can be produced en masse at low cost; more importantly, DNA vaccines against emerging pathogens or bioterrorism threats can be quickly constructed based solely upon the pathogen's genetic code. The main drawback of DNA vaccines is that they often induce lower immune responses than traditional vaccines, particularly in nonrodent species. Thus, improving the efficacy of DNA vaccines is a critical issue in vaccine development. In this study we have enhanced the efficacy of DNA vaccines by adopting strategies that increase gene expression. We generated influenza-hemagglutinin (HA)-encoding DNA vaccines that contain the hybrid CMV enhancer/chicken beta-actin (CAG) promoter and/or the mRNA-stabilizing post-transcriptional regulatory element from the woodchuck hepatitis virus (WPRE). Mice were immunized with these DNA vaccines, and the influenza-HA-specific cellular and humoral immune responses were compared with a conventional, HA-encoding DNA vaccine whose gene expression was driven by the CMV immediate-early promoter (pCMV-HA). CAG promoter-driven DNA vaccines elicited significantly higher humoral and cellular immune responses compared with the pCMV-HA vaccine. DNA vaccines consisting of both CAG and WPRE elements (pCAG-HA-WPRE) induced the highest level of protective immunity, such that immunization with 10-fold lower DNA doses prevented death in 100% of the mice upon lethal viral challenge, whereas all mice immunized with the conventional pCMV-HA vaccine succumbed to influenza infection.

tuberculosis genetic diversity susceptibility immune responses Tuberculosis remains one of the largest causes of death from an infectious agent, with 8 million new cases and 2 million deaths per annum [1]. It is also estimated that one third of the world's pop-ulation is latently infected with Mycobacterium tuberculosis. The vast majority of these individuals do not develop disease. The improved control of this pathogen will depend on a better under-standing of the many environmental and host genetic factors that determine the progression from latent infection to disease. The most important environmental factor, on a global scale, is HIV infection. Co-infection with HIV increases the risk of developing disease from 10 % in a lifetime to a 10 % annual risk [2]. There is evidence from twin studies of a genetic component to susceptibil-ity to tuberculosis [3] but no single major tuberculosis suscepti-

BALB/c or C57Bl/6 mice immunized with plasmids containing Trypanosoma cruzi genes developed specific immune responses and protective immunity against lethal parasitic infection. In contrast, in the highly susceptible mouse strain A/Sn, DNA vaccination reduced the peak parasitemia but promoted limited mouse survival after challenge. In the present study, we tested whether the immunogenicity and protective efficacy of vaccination could be improved by combining DNA and recombinant protein immunization regimens. A/Sn mice immunized with plasmid p154/13 which harbours the gene encoding Trypanosoma cruzi trans-sialidase developed a predominant type 1 immune response. In contrast, immunization with the recombinant Trypanosoma cruzi trans-sialidase protein adsorbed to alum generated a typical type 2 immune response. Simultaneous administration of both p154/13 and recombinant Trypanosoma cruzi trans-sialidase protein also led to a predominant type 2 immune response. Sequential immunization consisting of two priming doses of p154/13 followed by booster injections with recombinant Trypanosoma cruzi trans-sialidase protein significantly improved specific type 1 immune response, as revealed by a drastic reduction of the serum IgG1/IgG2a ratio and by an increase in the in vitro interferon-gamma secretion by CD4 T cells. Our observations confirm and extend previous data showing that a DNA-priming protein-boosting regimen might be a general strategy to enhance type 1 immune response to DNA vaccines. Upon challenge with Trypanosoma cruzi, no improvement in protective immunity was observed in mice immunized with the DNA-priming protein-boosting regimen when compared to animals that received DNA only. Therefore, our results suggest that in this experimental model there is no correlation between the magnitude of type 1 immune response and protective immunity against Trypanosoma cruzi infection.

Induction of specific humoral and cellular immunity in the lung airways is proposed to be critical for vaccine protection against Mycobacterium tuberculosis (M. tb). To facilitate airway delivery and antigen targeting to the antigen presenting cells in the alveoli, we employed mannosylated chitosan (MCS) to formulate a multi-T-epitope DNA vaccine, pPES, as an intranasal TB vaccine. MCS-DNA nanoparticles appeared spherical with the average particle sizes as 400 nm. HSP65-specific bronchoalveolar lavage fluid SIgA level was significantly elevated by 4 doses of MCS-pPES intranasal immunization as compared to chitosan (CS)-DNA and BCG vaccine. I.n. immunization with MCS-DNA induced a modest peptide-specific Th1(IFN-γ, TNF-α, and IL-2) response in the spleen, while a potent poly-functional CD4+ T response that largely produced TNF-α and IFN-γ, as well as IL-2 in the lung, qualitatively better than that induced by CS-DNA and BCG vaccination. Such response by i.n. immunization with MCS-DNA provided improved protection in the lung against airway Mycobacterial bovis BCG challenge over i.n. CS-DNA and DNA, that is comparable to protection achieved by s.c. BCG vaccination. This enhanced protection was correlated with much greater accessibility of DNA particles to the alveolar macrophages in the lung mediated by man-chitosan. Thus, man-chitosan TB vaccine represents a promising vaccine platform capable of eliciting robust multi-functional T response in the lung mucus and achieving enhanced mucosal immune protection against pulmonary TB.

Cattle vaccination against bovine tuberculosis (bTB) has been proposed as a supplementary method to help control the incidences of this disease. Bacillus Calmette-Guérin (BCG) is currently the only viable candidate vaccine for immunization of cattle against bTB, caused by Mycobacterium bovis (M.bovis). In an attempt to characterize the differences in the immune response following M.bovis infection between BCG-vaccinated and non-vaccinated animals, a combination of gross pathology, histopathology and immunohistochemical (IHC) analyses was used. BCG vaccination was found to significantly reduce the number of gross and microscopic lesions present within the lungs and lymph nodes. Additionally, the microscopically visible bacterial load of stages III and IV granulomas was reduced. IHC using cell surface markers revealed the number of CD68+ (macrophages), CD3+ (T lymphocytes) and WC1+ cells (γδ T cells) to be significantly reduced in lymph node granulomas of BCG-vaccinated animals, when compared to non-vaccinated animals. B lymphocytes (CD79a+) were significantly increased in BCG-vaccinated cattle for granulomas at stages II, III and IV. IHC staining for iNOS showed a higher expression in granulomas from BCG-vaccinated animals compared to non-vaccinated animals for all stages, being statistically significant in stages I and IV. TGFβ expression decreased alongside the granuloma development in non-vaccinated animals, whereas BCG-vaccinated animals showed a slight increase alongside lesion progression. IHC analysis of the cytokines IFN-γ and TNF-α demonstrated significantly increased expression within the lymph node granulomas of BCG-vaccinated cattle. This is suggestive of a protective role for IFN-γ and TNF-α in response to M.bovis infection. Findings shown in this study suggest that the use of BCG vaccine can reduce the number and severity of lesions, induce a different phenotypic response and increase the local expression of key cytokines related to protection.

Live vaccines are gradually replaced by protein-based vaccines given the latter's better safety. But live vaccines seem to be more efficient via stimulation of the innate immune system.

Immunogenicity and protective efficacy of ApxIA and ApxIIA DNA vaccine against Actinobacillus pleuropneumoniae lethal challenge in murine model

MURINE IL-2 SECRETING RECOMBINANT BACILLUS CALMETTE-GUÉRIN AUGMENTS MACROPHAGE-MEDIATED CYTOTOXICITY AGAINST MURINE BLADDER CANCER MBT-2

Background: Bladder cancer is the 5th most common cancer worldwide, with the most common type being non-muscle invasive bladder cancer (NMIBC). Treatment for high grade NMIBC includes resection of the bladder tumor followed by repeated intravesical administration of Bacillus-Calmette Guérin (BCG), the live-attenuated form of Mycobacterium bovis. Unfortunately, 60-70% of patients will experience disease recurrence. Our current understanding is that BCG acts within the local bladder tumor microenvironment and draining lymph nodes, leading to the activation of a systemic immune response. Using a murine model of NMIBC, here we investigated whether different routes of BCG administration alter the systemic immune response to BCG and affect tumor size. Methods: To establish syngeneic orthotopic bladder tumors in a mouse model, female C57Bl/6 mice were catheterized and 2.5 x 105 mouse bladder cancer cells (MB49) were instilled into the bladder. Beginning on day 7, mice received either intravesical, intravenous (IV) or intraperitoneal (IP) BCG (8 mg/ml) or saline once weekly for three weeks and bladders were imaged through ultrasound. At endpoint (day 23), tumors, tumor draining lymph nodes (tdLNs), spleen, and bone marrow were harvested and stored. Immune composition of the various lymphoid organs was evaluated using polychromatic flow cytometry. Ex vivo responsiveness to lipopolysaccharide (LPS) was assessed in bone marrow cells by measuring cytokine levels in culture supernatants. Results: Mice treated with IV BCG had significantly smaller tumor volumes when compared to intravesical BCG treatment. Ex vivo LPS stimulation of bone marrow from BCG-treated mice, regardless of administration route, led to increased release of pro-inflammatory cytokines compared with saline controls. IP and IV BCG treatment skewed immune microenvironments of secondary lymphoid organs towards a cytotoxic phenotype compared with intravesical BCG treatment. Within the lymphoid compartment of tdLNs, the proportion of CD8+ T cells was significantly increased while the proportion of CD4+ T cells was significantly decreased in mice treated with IV and IP BCG compared with intravesical BCG. Conversely, the proportion of CD11b+ dendritic cells (DCs) was significantly increased in tdLNs from mice receiving intravesical BCG compared with BCG administered IV or IP. Within the spleen, the proportion of CD8+CD11b- DCs were significantly increased in the DC compartment following IP BCG treatment compared to other treatment routes. Conclusion: This provides evidence that route of BCG administration affects the immune composition of secondary lymphoid organs that may be associated with anti-tumor responses. A better understanding of the mechanism of BCG immunotherapy will lead to novel approaches to optimize anti-tumor immune responses and, consequently, improved patient outcomes. Citation Format: Arielle Grossman, Aline Atallah, Tiziana Cotechini, Jean-Francois Pare, Robert Siemens, Charles H. Graham. Effect of route of Bacillus-Calmette Guerin administration on systemic immune responses in a murine model of non-muscle invasive bladder cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 2058.

In order to enhance the immune efficacy of DNA vaccination, experiments were conducted to investigate the regulating effects of Bacillus Calmette-Guerin (BCG)-DNA as an adjuvant on immune responses of mice against foot-and-mouth disease (FMD), Aujeszky's disease (AjD) and classical swine fever (CSF). BCG-DNA was purified from BCG by ion-exchange chromatography. Three DNA vaccines (pVSG, pVgD and pVE2) against the respective infection were constructed, and BCG-DNA was coimmunized to mice by muscle injection. The results showed that titres of specific immunoglobulin (Ig)G to the vaccines mounted remarkably in the sera of the adjuvant covaccinated mice (P < 0.01). Antibody isotype IgG2a and IgG1 also increased, respectively, in mice coimmunized with BCG-DNA compared with those of the control groups (P < 0.01). Cellular immune cytokine interferon-gamma and cytotoxic T lymphocytes were detected in coimmunized BCG-DNA groups (P < 0.05). Whereas interleukin-4, humoral immune cytokine, was not significant (P > 0.05). These results suggest that codelivery of BCG-DNA with DNA vaccines against FMD, AjD and CSF can enhance the induction of antigen-specific, especially, cell-mediated immunity.

The effects of CCL3, CCL4, CCL19 and CCL21 as molecular adjuvants on the immune response to VAA DNA vaccine in flounder (Paralichthys olivaceus)

Two bacillus Calmette-Guérin (BCG)-susceptible mouse strains, BALB/c and C57BL/6, were infected intravenously with Mycobacterium intracellulare, M. avium or M. scrofulaceum and monitored during 3 months for mycobacterial replication and antibody and Th1-type cytokine production in response to cytoplasmic and secreted antigens from M. bovis BCG. Whereas initial colony-forming unit (CFU) counts of M. intracellulare and M. avium were higher in lungs than in spleen, the opposite was observed for M. scrofulaceum. Mycobacterium intracellulare was the most virulent species and its replication could not be controlled in either mouse strain. It also induced the strongest antibody response. Mycobacterium avium was eliminated in both mouse strains and M. scrofulaceum finally was eliminated in C57BL/6 but multiplied in spleen from BALB/c mice. Significant sustained interleukin-2 and interferon-gamma production towards BCG antigens was only found in M. scrofulaceum infection. As in BCG-vaccination, M. scrofulaceum-infected C57BL/6 mice demonstrated a higher response towards whole BCG culture filtrate, BCG extract and purified antigen 85 complex (Ag85) from BCG than did BALB/c mice. The data suggest that the presence of M. scrofulaceum in the environment may possibly interfere in genetically predisposed subjects with BCG vaccine and its protective efficacy against M. tuberculosis.