Plasmid Interleukin-23 (IL-23), but Not Plasmid IL-27, Enhances the Protective Efficacy of a DNA Vaccine againstMycobacterium tuberculosisInfection

Abstract

Protection against intracellular pathogens such asTuberculosis (TB) is a global health emergency, with an estimated nine million new cases of active disease and approximately 2 million deaths per year (11a). The development of more effective vaccines than the current vaccine Mycobacterium bovis bacillus Calmette-Guérin (BCG) may improve the control of this pandemic. New approaches to the design of TB vaccines include the preparation of recombinant BCG oversecreting mycobacterial antigens (32), attenuated strains of M. tuberculosis (54), and subunit vaccines based on DNA or protein antigens (33, 55). DNA vaccines encoding M. tuberculosis proteins, such as antigen 85A (Ag85A) or Ag85B (DNA85), induce partial protection against experimental TB (34, 36). However, the degree of protection gained from DNA vaccination alone is less than that afforded by BCG vaccination. Strategies to improve antimycobacterial immunity from subunit vaccines include the development of fusion proteins containing multiple protective antigens (46) and the use of immunostimulatory molecules as adjuvants (50).The development of acquired cellular immunity is critical for the control of M. tuberculosis infection. The key cytokine required for cell-mediated immunity is gamma interferon (IFN-␥), which functions by stimulating infected macrophages to induce phagolysosomal fusion and killing of intracellular bacteria (10,20). The heterodimeric cytokines interleukin-12 (IL-12) and IL-18 are critical for the induction of Th1-like CD4 ϩ cells and are produced primarily by dendritic cells (DCs) (44,59,67). Humans and mice lacking the p40 chain of IL-12 or its receptors are highly susceptibility to M. tuberculosis infection (6, 11). Plasmids expressing either IL-12 or IL-18 have been used as adjuvants in several infectious models (42,45,50). Coadministration of plasmids expressing IL-12 or IL-18 increased the IFN-␥ T-cell response in DNA vaccination to Ag85B, but only plasmids expressing IL-12 increased protective efficacy (62).Recently, two further cytokines, IL-23 and IL-27, have been found to contribute to the development of Th1-like CD4 ϩ T-cell responses. The heterodimeric cytokine IL-23 is secreted by activated macrophages and DCs and induces clonal expansion of memory CD4 ϩ T cells (49). IL-23 is composed of a p40 subunit, shared with IL-12, and a unique p19 subunit, signaling through the receptor IL-12R␤, and a unique IL-23R chain (49). In addition to its direct action on T cells, IL-23 also induces the secretion of IL-12 and IFN-␥ by DCs in vitro (4). This suggests that IL-23 has indirect involvement in the activation of antigen-presenting cells (APCs). Studies with genedeficient mice reveal that a number of roles that were previously accredited to IL-12 may be dependent on IL-23 (12). In

Lactoferrin enhanced efficacy of the BCG vaccine to generate host protective responses against challenge with virulent Mycobacterium tuberculosis

“…BCG antigen stimulated splenocytes from non-immunized mice (38 +/− 17 pg/mL) had similar level of IL-1β compared to mice immunized with BCG/ lactoferrin (44 +/− 21 pg/mL); production of IL-1β was significantly decreased in splenocytes from the BCG immunized group (24 +/− 13 pg/mL) compared to the BCG/lactoferrin group. TB vaccines are useful when given as a one time injection or when administered using various schedules of prime-boost protocols [10,14,15,[43][44][45][46][47][48][49]. The next experiments examined the BCG/lactoferrin saline immunization protocol to generate protection against MTB infection when mice were immunized once (Protocol C), or when boosted prior to infection (Protocol D).…”

Interleukin-23 Restores Immunity to Mycobacterium tuberculosis Infection in IL-12p40-Deficient Mice and Is Not Required for the Development of IL-17-Secreting T Cell Responses

“…This suggested that IL-23 was not essential for the development of resistance during the acute stage of infection. By contrast, during immunization with a DNA vaccine expressing Ag 85B (DNA85B), plasmid-expressing IL-23 was as effective as plasmid IL-12 as an adjuvant to increase the frequency of IFN-␥-secreting T cells and protection against aerosol M. tuberculosis infection (23).…”

“…The blunt ends were self-ligated to yield IL-12p40 and the sequence integrity confirmed. The bioactivity of plasmids expressing IL-12 or IL-23 was confirmed previously (23,25). The DNA used in immunizations was prepared by equilibrium centrifugation in a continuous CsCl-ethidium bromide gradient.…”

“…The construction of DNA vaccines encoding M. tuberculosis Ag85B (DNA85B), murine IL-12 (p2AIL-12) and murine IL-23 (p2AIL-23) has been described previously (23,24). The plasmid expressing murine IL12p40 as a monomer was constructed by excising the IL-12p35 subunit and the 2A fragment from p2AIL-12 with the use of restriction enzymes Mlu and Apa, resulting in a 5Ј overhang that was end filled using T4 polymerase.…”

Improved Protection against Disseminated Tuberculosis by Mycobacterium bovis Bacillus Calmette-Guérin Secreting Murine GM-CSF Is Associated with Expansion and Activation of APCs

“…Bone marrow progenitor cells were generated as previously described (30). For in vitro studies, rBCG strains were grown in 7H9 broth supplemented with 10% ADC (without albumin) for 14 days.…”