The study of novel DNA vaccines against tuberculosis: induction of pathogen-specific CTL in the mouse and monkey models of tuberculosis

Prospective Subunit Nanovaccine against Mycobacterium tuberculosis Infection─Cubosome Lipid Nanocarriers of Cord Factor, Trehalose 6,6' Dimycolate

An improved vaccine is urgently needed to replace the now more than 100-year-old Bacillus Calmette-Guérin (BCG) vaccine against tuberculosis (TB) disease, which represents a significant burden on global public health. Mycolic acid, or cord factor trehalose 6,6' dimycolate (TDM), a lipid component abundant in the cell wall of the pathogen Mycobacterium tuberculosis (MTB), has been shown to have strong immunostimulatory activity but remains underexplored due to its high toxicity and poor solubility. Herein, we employed a novel strategy to encapsulate TDM within a cubosome lipid nanocarrier as a potential subunit nanovaccine candidate against TB. This strategy not only increased the solubility and reduced the toxicity of TDM but also elicited a protective immune response to control MTB growth in macrophages. Both pre-treatment and concurrent treatment of the TDM encapsulated in lipid monoolein (MO) cubosomes (MO-TDM) (1 mol %) induced a strong proinflammatory cytokine response in MTB-infected macrophages, due to epigenetic changes at the promoters of tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6) in comparison to the untreated control. Furthermore, treatment with MO-TDM (1 mol %) cubosomes significantly improved antigen processing and presentation capabilities of MTB-infected macrophages to CD4 T cells. The ability of MO-TDM (1 mol %) cubosomes to induce a robust innate and adaptive response in vitro was further supported by a mathematical modeling study predicting the vaccine efficacy in vivo. Overall, these results indicate a strong immunostimulatory effect of TDM when delivered through the lipid nanocarrier, suggesting its potential as a novel TB vaccine.

A new DNA vaccine expressing HspX-PPE44-EsxV fusion antigens of Mycobacterium tuberculosis induced strong immune responses

OBJECTIVES

Infection with tuberculosis (TB) is regarded as a major health issue. Due to the emergence of antibiotic resistance during TB treatment, prevention via vaccination is one of the most effective ways of controlling the infection. DNA vaccines are developed at a greater pace due to their ability in generating a long-lasting immune response, higher safety compared to the live vaccines, and relatively lower cost of production. In the present study, we evaluated a new DNA vaccine encoding the fusion HspX-PPE44-EsxV antigens, separately, and in combination with Bacillus Calmette-Guérin (BCG) administration, in a prime-boost method in mice.

MATERIALS AND METHODS

A novel DNA vaccine encoding HspX-PPE44-EsxV fusion antigen of Mycobacterium tuberculosis was constructed, and RT-PCR and Western blot analysis were performed to verify the expression of the antigen. Female BALB/c mice were divided into five groups (PBS, BCG, pcDNA3.1 (+) vector, pDNA/HspX-PPE44-EsxV vaccine, and the BCG-prime boost groups). In order to evaluate the immunogenicity of the recombinant vector, BALB/c mice were injected with 100 μg of pDNA at 2-week intervals. Then, cytokine assay was conducted using eBioscience ELISA kits (Ebioscience, AUT) according to manufacturers' instructions to evaluate the concentrations of IL-4, IL-12, TGF-β, and IFN-γ.

RESULTS

The concentrations of INF-γ, IL-12, and TGF-beta were significantly increased compared to the control groups (P<0.001). INF-γ and IL-12 production were increased significantly in pDNA/HspX-PPE44-EsxV+BCG group compared to pDNA/HspX-PPE44-EsxV group (P<0.001).

CONCLUSION

This study showed that the present DNA vaccine could induce a high level of specific cytokines in mice. It was also shown that using this DNA vaccine in a BCG prime-boost protocol can produce significant amounts of IFN-γ, IL-12, and TGF-β.

Finding New Ways to Combat Multidrug-Resistant Tuberculosis

Tuberculosis (TB) is a major issue in global health and affects millions of people each year. Multidrug-resistant tuberculosis (MDR-TB) annually causes many deaths worldwide. Development of a way to diagnose and treat patients with MDR-TB can potentially reduce the incidence of the disease. The current study reviews the risk factors, pattern of progression, mechanism of resistance, and interaction between bacteria and the host immune system, which disrupts the immune response. It also targets the components of Mycobacterium tuberculosis (Mtb) and diagnosis and treatment options that could be available for clinical use in the near future. Mutations play an important role in development of MDR-TB and the selection of appropriate mutations can help to understand the type of resistance in patients to anti-TB drugs. In this way, they can be initially treated with proper and effective therapeutic choices, which can accelerate the course of treatment and improve patient health. Targeting the components and enzymes of Mtb is necessary for understanding bacterial survival and finding a way to destroy the pathogen and allow patients to recover faster and prevent the spread of disease, especially resistant strains.

Preclinical study and clinical trial of a novel therapeutic vaccine against multi-drug resistant tuberculosis

[Purpose] Multi-drug resistant (MDR), Mycobacterium tuberculosis (TB) is a big problem in the world. We have developed novel TB therapeutic vaccine (HVJ-E/HSP65 DNA +IL-12 DNA). [Methods and Results] DNA vaccine expressing TB heat shock protein 65 and IL-12 was delivered by the hemagglutinating virus of Japan (HVJ)-envelope. This vaccine provided remarkable protective efficacy and strong therapeutic efficacy against MDR-TB and XDR-TB in murine models. Furthermore, this vaccine provided therapeutic efficacy of prolongation of survival time of TB infected monkeys and augmented the immune responses. Therefore, the preclinical tests were studied for clinical trial. The injection of 100 μg of the vaccine /mouse i.m. three times in two weeks induced significantly strong production of IFN-γ and IL-2. 100 μg and 200 μg DNA vaccine/mouse i.m. augmented the production of these cytokines compared with 25 μg DNA vaccine/mouse i.m.. The ratio of 100 μg pDNA to 1AU HVJ-E enhanced the production of IFN-γ and IL-2. The decrease in the number of M. tuberculosis in liver of mice was observed by the vaccination of 100μg pDNA. By using these conditions, safety pharmacology study and toxicology test is being studied in monkeys administered by GMP level DNA vaccines. By the toxicology test using monkeys, high dose GMP level vaccine/ monkey is administrated. Safety pharmacological study of repeated administration is also being investigated in GLP level. Furthermore, we have planned to do clinical phase I trial. Targets are human patients with MDR-TB. The safety and tolerability of the vaccine will be evaluated. [Conclusion and recommendations] These data indicate that our novel vaccine might be useful against tuberculosis including XDR-TB and MDR-TB for human therapeutic clinical applications.

Flaviviruses, an expanding threat in public health: focus on dengue, West Nile, and Japanese encephalitis virus

The flaviviruses dengue, West Nile, and Japanese encephalitis represent three major mosquito-borne viruses worldwide. These pathogens impact the lives of millions of individuals and potentially could affect non-endemic areas already colonized by mosquito vectors. Unintentional transport of infected vectors (Aedes and Culex spp.), traveling within endemic areas, rapid adaptation of the insects into new geographic locations, climate change, and lack of medical surveillance have greatly contributed to the increase in flaviviral infections worldwide. The mechanisms by which flaviviruses alter the immune and the central nervous system have only recently been examined despite the alarming number of infections, related deaths, and increasing global distribution. In this review, we will discuss the expansion of the geographic areas affected by flaviviruses, the potential threats to previously unaffected countries, the mechanisms of pathogenesis, and the potential therapeutic interventions to limit the devastating consequences of these viruses.