Comparison of Immune Responses Induced in Mice by Vaccination with DNA Vaccine Constructs Expressing Mycobacterial Antigen 85A and Interleukin-21 and Bacillus Galmette-Guérin

Promising Cytokine Adjuvants for Enhancing Tuberculosis Vaccine Immunity

Tuberculosis, caused by Mycobacterium tuberculosis (M. tuberculosis), remains a formidable global health challenge, affecting a substantial portion of the world's population. The current tuberculosis vaccine, bacille Calmette-Guérin (BCG), offers limited protection against pulmonary tuberculosis in adults, underscoring the critical need for innovative vaccination strategies. Cytokines are pivotal in modulating immune responses and have been explored as potential adjuvants to enhance vaccine efficacy. The strategic inclusion of cytokines as adjuvants in tuberculosis vaccines holds significant promise for augmenting vaccine-induced immune responses and strengthening protection against M. tuberculosis. This review delves into promising cytokines, such as Type I interferons (IFNs), Type II IFN, interleukins such as IL-2, IL-7, IL-15, IL-12, and IL-21, alongside the use of a granulocyte-macrophage colony-stimulating factor (GM-CSF) as an adjuvant, which has shown effectiveness in boosting immune responses and enhancing vaccine efficacy in tuberculosis models.

Cytokines and their role as immunotherapeutics and vaccine Adjuvants: The emerging concepts

Cytokines are a protein family comprising interleukins, lymphokines, chemokines, monokines and interferons. They are significant constituents of the immune system, and they act in accordance with specific cytokine inhibiting compounds and receptors for the regulation of immune responses. Cytokine studies have resulted in the establishment of newer therapies which are being utilized for the treatment of several malignant diseases. The advancement of these therapies has occurred from two distinct strategies. The first strategy involves administrating the recombinant and purified cytokines, and the second strategy involves administrating the therapeutics which inhibits harmful effects of endogenous and overexpressed cytokines. Colony stimulating factors and interferons are two exemplary therapeutics of cytokines. An important effect of cytokine receptor antagonist is that they can serve as anti-inflammatory agents by altering the treatments of inflammation disorder, therefore inhibiting the effects of tumour necrosis factor. In this article, we have highlighted the research behind the establishment of cytokines as therapeutics and vaccine adjuvants, their role of immunotolerance, and their limitations.

IL-21-secreting hUCMSCs combined with miR-200c inhibit tumor growth and metastasis via repression of Wnt/β-catenin signaling and epithelial-mesenchymal transition in epithelial ovarian cancer

Background

Epithelial ovarian cancer (EOC) with insidious characteristic manifests no symptoms in its early onset but most patients have advanced and distant cancer metastasis at diagnosis. Innovative early diagnosis and effective treatment of EOC are urgently needed.

Methods

In the study, we developed a novel agent of IL-21-secreting human umbilical cord mesenchymal stem cells (hUCMSCs) combined with miR-200c to evaluate its effects on SKOV3 EOC in vitro and in vivo.

Results

hUCMSCs-LV-IL-21 combined with miR-200c significantly inhibited the SKOV3 cell mobility and tumorigenesis compared with hUCMSCs-LV-IL-21, hUCMSCs-LV-vector, and hUCMSCs, respectively. These were reflected in decreasing the tumor sizes and elongating the tumor bearing nude mouse survival, accompanied with increasing the serum cytokine levels of IFN-γ, IL-21 and TNF-α as well as the splenocyte cytotoxicity. In addition, the expression of β-catenin, cyclin-D1, Gli1, Gli2, and ZEB1 was decreased but the E-cadherin expression was increased in tumor tissues of mice treated with hUCMSCs-LV-IL-21 plus miR-200c.

Conclusion

We demonstrated that the synergistic effect of fighting SKOV3 EOC is attributable to repression of Wnt/β-catenin signaling and epithelial-mesenchymal transition in SKOV3 EOC. The findings may provide a new strategy for therapy of EOC.

IL-21 Receptor Signaling Is Essential for Optimal CD4+ T Cell Function and Control of Mycobacterium tuberculosis Infection in Mice

In this study, we determined the role of IL-21R signaling in Mycobacterium tuberculosis infection, using IL-21R knockout (KO) mice. A total of 50% of M. tuberculosis H37Rv-infected IL-21R KO mice died in 6 mo compared with no deaths in infected wild type (WT) mice. M. tuberculosis-infected IL-21R KO mice had enhanced bacterial burden and reduced infiltration of Ag-specific T cells in lungs compared with M. tuberculosis-infected WT mice. Ag-specific T cells from the lungs of M. tuberculosis-infected IL-21R KO mice had increased expression of T cell inhibitory receptors, reduced expression of chemokine receptors, proliferated less, and produced less IFN- γ, compared with Ag-specific T cells from the lungs of M. tuberculosis-infected WT mice. T cells from M. tuberculosis-infected IL-21R KO mice were unable to induce optimal macrophage responses to M. tuberculosis. This may be due to a decrease in the Ag-specific T cell population. We also found that IL-21R signaling is associated with reduced expression of a transcriptional factor Eomesodermin and enhanced functional capacity of Ag-specific T cells of M. tuberculosis-infected mice. The sum of our findings suggests that IL-21R signaling is essential for the optimal control of M. tuberculosis infection.

CD226 as a genetic adjuvant to enhance immune efficacy induced by Ag85A DNA vaccination

Antigen-85A (Ag85A) is one of the major proteins secreted by Mycobacterium tuberculosis. Many studies on animal models have shown that vaccination with the recombinant Ag85A-DNA or Ag85A protein induces powerful immune response. However, these vaccines cannot generate sufficient protective immunity in the systemic compartment. CD226, a member of the immunoglobulin superfamily, is expressed in the majority of NK cells, T cells, monocytes, and platelets, and can be served as a co-stimulator that contributes to multiple innate and adaptive responses. However, there has been no study where either CD226 protein or DNA has been used as an adjuvant for vaccine development. The aim of this study was to develop a novel Ag85A DNA vaccine with CD226 as the genetic adjuvant to increase the immune efficacy induced by Ag85A. Oral vaccination with pcDNA3.1-Ag85A-CD226 DNA induced potent immune responses in mice. CD226 was an effective genetic adjuvant that improved the immune efficacy induced by Ag85A and enhanced the activity of cytotoxic T lymphocytes (CTL) and NK cells in mice. Th1 dominant cytokines (i.e. IL-2, IFN-γ and TNF-α), cellular immunity (i.e. CD4(+)IFN-γ(+)T cells and CD8(+)IFN-γ(+)T cells in splenocytes) and MLNs were also significantly elevated by pcDNA3.1-Ag85A-CD226 DNA vaccination. Our results suggest that CD226 is an effective adjuvant to enhance the immune efficacy induced by Ag85A. Our findings provide a new strategy for the development of a DNA vaccine co-expressing Ag85A and CD226.

A novel recombinant DNA vaccine encoding Mycobacterium tuberculosis ESAT-6 and FL protects against Mycobacterium tuberculosis challenge in mice

Mycobacterium tuberculosis 6-kDa early secretory antigenic target (ESAT-6) is a dominant target antigen for cell-mediated immunity in the early phase of tuberculosis. The fms-like tyrosine kinase 3 ligand (FL) that induces potent immune response has been used as an adjuvant in vaccine development. In this study, a new recombinant plasmid (pIRES-epitope-peptides-FL) encoding three T cell epitopes of ESAT-6 and FL was constructed, and the immunogenicity of the DNA vaccine was assessed in C57BL/6 mice immunized with the plasmid DNA vaccine. Additionally, a strategy of intramuscular injection with the DNA vaccine (prime) and intranasal administration of the epitope peptides (boost) was employed to induce higher immune reaction of the mice. The results showed that mice vaccinated with the recombinant plasmid DNA vaccine and boosted with the peptides not only increased the levels of Th1 cytokines (IFN-γ and IL-12), the number of IFN-γ⁺ T cells and activities of cytotoxic T lymphocytes as well as IgG, but also enhanced protection against Mycobacterium tuberculosis challenge. In conclusion, these data indicate that the novel recombinant pIRES-epitope-peptides-FL plasmid is a useful DNA vaccine for preventing Mycobacterium tuberculosis infection.

Tuberculosis vaccine research in China

It is now privately acknowledged that there may be little if any perceptible impact of the national Bacille Calmette-Guerin (BCG) vaccination program on disease prevalence, despite the extensive coverage of the newborn infant population and likely benefit in the early years of life. A better preventive vaccine than BCG is now being sought by Chinese researchers. Urgency has been added to the control problem by the emergence of multidrug-resistant tuberculosis (TB). Furthermore, expensive second-line drugs seem unlikely to be made available by the government to treat drug-resistant cases, so attention in addition has turned to the potential of immunotherapy as an adjunct to chemotherapy. Research trends are summarized here.

Nanoparticle-based adjuvant for enhanced protective efficacy of DNA vaccine Ag85A-ESAT-6-IL-21 against Mycobacterium tuberculosis infection

The goal of this study was to evaluate the protective efficacy of a cationic nanoparticle-based DNA vaccine expressing antigen 85A (Ag85A) and 6-kDa early secretory antigen target (ESAT-6) of Mycobacterium tuberculosis as well as cytokine interleukin-21 (IL-21) against M. tuberculosis infection. The results of this indicated that the anti-M. tuberculosis immune responses were induced in mice that had received the different DNA vaccines. More importantly, compared with using DNA vaccine Ag85A-ESAT-6-IL-21 alone, the nanoparticle-based DNA vaccine Ag85A-ESAT-6-IL-21 showed a statistically significant increase in the protective efficacy against M. tuberculosis infection in the immunized mice. We concluded that the nanoparticle-based DNA vaccine induced a strong immune response and markedly inhibited the growth of the M. tuberculosis in the mice. These findings highlighted the potential utility of Fe3O4-Glu-polyethyleneimine nanoparticles encapsulated with the DNA vaccine as a prophylactic vaccine in the M. tuberculosis-infected mouse model.

FROM THE CLINICAL EDITOR

This study emphasizes the potential utility of Fe3O4-Glu-polyethyleneimine nanoparticles encapsulated with DNA vaccine against TB as a prophylactic vaccine. The authors demonstrated a strong immune response and marked growth inhibition of mycobacterium tuberculosis in the mice.

Interleukin-21 administration to rhesus macaques chronically infected with simian immunodeficiency virus increases cytotoxic effector molecules in T cells and NK cells and enhances B cell function without increasing immune activation or viral replication

We have previously shown that interleukin-21, a pleiotropic C γ-chain signaling cytokine, induces the expression of the cytotoxic molecules granzyme B (GrB) and perforin in vitro in CD8 T cells and NK cells of chronically HIV infected individuals. In this pilot study, four chronically SIV infected rhesus macaques (RM) in late-stage disease were given two doses of recombinant MamuIL-21, 50 μg/kg, intravenously 7 days apart, followed by one subcutaneous dose, 100 μg/kg, 23 days after the second dose. Three animals served as controls. After each dose of IL-21, increases were noted in frequency and mean fluorescence intensity of GrB and perforin expression in memory and effector subsets of CD8 T cells in peripheral blood (PB), in peripheral and mesenteric lymph node (LN) cells, in PB memory and effector CD4 T cells and in NK cells. Frequencies of SIV-gag specific CD107a(+)IFN-γ(+) CD8 T cells increased 3.8-fold in PB and 1.8-fold in LN. In addition, PB CD27(+) memory B cells were 2-fold higher and serum SIV antibodies increased significantly after IL-21 administration. No changes were observed in markers of T cell activation, T cell proliferation or plasma virus load. Thus, administration of IL-21 to chronically SIV infected viremic animals was safe, well tolerated and could augment the cytotoxic potential of T cells and NK cells, promote B cell differentiation with increases in SIV antibody titers without discernable increase in cellular activation. Further studies are warranted to elucidate the effects and potential benefit of IL-21 administration in the context of SIV/HIV infection and in SIV/HIV vaccine design.

Antitumor efficacy induced by a B16F10 tumor cell vaccine treated with mitoxantrone alone or in combination with reserpine and verapamil in mice

An apoptotic tumor cell serves as a potential potent trigger for the initiation of naturally occurring tumor immunity. In the present study, a B16F10 tumor cell vaccine treated with mitoxantrone (MIT) was developed, and its antitumor effect on mice was evaluated. The results indicated that the B16F10 tumor cell vaccine treated with MIT alone or in combination with reserpine (RP) and verapamil (VP) for 12 h triggered apoptosis, and that the expression of CD80, the MHC II class molecule, NKG2D and its ligand were significantly increased compared to the expression levels in the control group. The tumor vaccine immunogenicity was significantly enhanced in the vaccinated mice, resulting in augmented cytotoxicity of splenocytes and NK cells as well as the splenocyte proliferative response compared to the control group mice. Notably, the mice vaccinated with the B16F10 tumor cell vaccine treated with MIT, RP and VP did not generate tumors only after 60 days into the observation, but the mice also generated a powerful immune prophylactic efficiency against the B16F10 tumor cell challenge. These findings demonstrated the safety and efficacy of the B16F10 tumor cell vaccine treated with MIT alone or in combination with RP and VP in the murine model, and suggest that an apoptotic tumor cell vaccine modeled on naturally occurring tumor immune responses in vivo may provide a safe and immunogenic tumor vaccine for potential applications in humans.

Immunization with DNA vaccine expressing herpes simplex virus type 1 gD and IL-21 protects against mouse herpes keratitis

The development of novel vaccines to eradicate herpes simplex virus (HSV) is a global public health priority. In this study, we developed a DNA vaccine expressing HSV-1 glycoprotein D (gD) and mouse interleukin-21(IL-21) and intramuscularly inoculated mice 3 times at 2-week intervals with a total of 300 ?g/mouse. Two weeks after the last immunization the specific antibody, splenocyte proliferative response to gD, IFN-? and IL-4 as well as the cytotoxic activities of splenocytes and natural killer (NK) cells were assayed. Immune protection against herpes keratitis was concurrently evaluated in the immunized mice after HSV-1 challenge of the mouse cornea. The results showed that the DNA vaccine pRSC-gD-IL-21 generated higher levels of antibody, IFN-? and IL-4, and enhanced the splenocyte proliferative response to gD as well as the cytotoxic activity of splenocytes and NK cells to target cells compared with the response in either the pRSC-gD or mock plasmid pRSC immunized mice. Importantly, the pRSC-gD-IL-21 ameliorated herpes keratitis severity and time course after corneal infection with HSV-1. The findings suggest that the DNA vaccine pRSC-gD-IL-21 may induce an immune response that can limit HSV-1 infection and development of herpes keratitis in the immunized mice.

An ocular mucosal administration of nanoparticles containing DNA vaccine pRSC-gD-IL-21 confers protection against mucosal challenge with herpes simplex virus type 1 in mice

Herpes stromal keratitis (HSK) is a chronic inflammatory process caused by the infection of herpes simplex virus type 1 (HSV-1). Development of a HSV-1 vaccine is a priority because these infections are common and cannot be well prevented. It appears that the potential of nanocarriers in DNA vaccination will be required to augment the immune response to DNA vaccines. Therefore, in the study, nanoparticles Fe(3)O(4) coated with glutamic acid, DNA vaccine pRSC-gD-IL-21 and polyethylenimine were prepared and immunized in the mice by ocular mucosal administration. The immune responses and protection efficiency against HSV-1 challenge were also tested. The results showed that the nanoparticles containing DNA vaccine pRSC-gD-IL-21 induced mice to generate higher levels of specific neutralizing antibody, sIgA in tears, and IFN-γ, IL-4 in serum, and to enhance the cytotoxicities of NK cells and splenocytes as well as splenocyte proliferative response to glycoprotein D compared with those of the control mice. More importantly, the mice immunized with the experimental vaccine showed less HSK degree than that of the control mice after HSV-1 challenge of the murine ocular mucosa. In conclusion, an ocular mucosal administration of nanoparticles containing DNA vaccine confers strong specific immune responses and effective inhibition of HSK in a HSV-1 infected murine model.

Immunoprophylaxis of tuberculosis: an update of emerging trends

Developing effective prophylactics to combat tuberculosis is currently in an exploratory stage. The HIV pandemic and emergence of multi- and extensively drug-resistant strains of Mycobacterium tuberculosis indicate that the current preventive measures against this ever-evolving pathogen are inadequate. The currently available vaccine BCG in its present form affords variable protection which usually wanes with aging. Various reasons have been cited to explain the discrepancies in the efficacy of BCG, including generic differences in the different BCG vaccine strains used in immunization program throughout the world. The low efficacy of BCG vaccine has promoted the search for novel vaccines for tuberculosis. The search strategies aim at completely replacing the existing vaccine and/or augmenting/improving the current BCG vaccine. Among new vaccine candidates are live attenuated M. tuberculosis vaccines, recombinant BCG, DNA vaccines, subunit vaccine, and fusion protein-based vaccines. More than 200 new vaccine candidates have been developed as a result of research work over the past few years. To date, at least eight vaccine candidates are undergoing clinical evaluation, with a few of them successfully qualifying in the first phase of clinical testing. These recent advances present an optimistic insight whereby a new tuberculosis vaccine might be expected to be available for public use in the next few years.

Adjuvant activity of cytokines

The activity of several potent adjuvants, including incomplete Freund's adjuvant, CpG oligodeoxynucleotides, and alum, has been shown to be due at least in part to the induction of cytokines, including type I interferons (IFNs), IFN-gamma, interleukin-2 (IL-2), and IL-12, that play key roles in the regulation of innate and adaptive immunity. The relatively short half-life of recombinant homologues of cytokines has limited their use as vaccine adjuvants. These difficulties have been overcome by encapsulation into liposomes and the use of cytokine expression vectors co-administered with DNA vaccines. Although a number of cytokines including IFN-alpha, IFN-gamma, IL-2, IL-12, IL-15, IL-18, IL-21, GM-CSF, and Flt-3 ligand have been shown to potentiate the immune response to vaccination in various experimental models, the full potential of cytokines as vaccine adjuvants remains to be established.

Induction of granulysin in CD8+ T cells by IL-21 and IL-15 is suppressed by human immunodeficiency virus-1

Immunosuppression following infection with HIV-1 predisposes patients to a myriad of opportunistic pathogens, one of the most important of which is Mtb. Granulysin, expressed by NK cells and CTL, exhibits potent antimicrobial activity against Mtb and several other opportunistic pathogens associated with HIV-1 infection. The immune signals that promote granulysin expression in human CTL are not fully understood. Using primary human CD8+ T cells, in this study, we identify IL-21 as a strong inducer of granulysin, demonstrate that IL-21 and IL-15 activate granulysin expression within CD8+ CD45RO+ T cells, and establish a role for Jak/STAT signaling in the regulation of granulysin within CD8+ T cells. We show that infection of PBMC from healthy donors in vitro with HIV-1 suppresses granulysin expression by CD8+ T cells, concomitant with reduced p-STAT3 and p-STAT5, following activation with IL-15 and IL-21. Of note, simultaneous signaling through IL-15 and IL-21 could partially overcome the immunosuppressive effects of HIV-1 on granulysin expression by CD8+ T cells. These results suggest that HIV-1 infection of PBMC may reduce the antimicrobial profile of activated CD8+ T cells by disrupting signaling events that are critical for the induction of granulysin. Understanding the effects of HIV-1 on CD8+ T cell activation is essential to understanding the physiological basis for inadequate cytotoxic lymphocyte activity in HIV+ patients and for informed guidance of cytokine-based therapy to restore T cell function.