Generation of a novel chimeric PALFn antigen of Bacillus anthracis and its immunological characterization in mouse model

Abstract

Bacillus anthracis chimeric molecule PALFn, comprising the immunodominant domains of protective antigen (PA) and lethal factor (LF), has been developed in the past and has been shown to confer enhanced protection against anthrax in mouse model when challenged with anthrax lethal toxin (LeTx). However, the immunological correlates for this chimeric antigen, both in terms of humoral as well as cell-mediated immune responses, have not been described in detail. To address this gap, we have determined the immunological responses both at humoral as well as cellular levels for the protection conferred by the novel chimeric antigen PALFn constructed in our laboratory in comparison to PA antigen. The biological functionality of the chimeric antigen was ascertained by the trypsin digestion assay. The trypsin cleavage activated the functionality of PALFn and rendered it to interact and bind with the LF molecule. Similarly, the LFn component in the chimera could independently interact and bind to the trypsin-activated wild-type PA. Further, it was observed that the PALFn-immunized mice sera could readily react to both PA and LF antigens while PA-immunized mice sera showed reaction to PA and PALFn alone and not to the individual LF antigen. The in vitro toxin neutralizing ability of PALFn antisera on macrophage cell line J774.1 was robust but with 1.3-fold lesser titer than PA-immunized antisera. PALFn-immunized mouse splenocytes showed a significant lymphocyte proliferation when stimulated with PALFn. There was a remarkable increase in the level of interleukin-2 (IL-2), interleukin-4 (IL-4), interleukin 10 (IL-10), interferon-γ (IFN- γ), and tumor necrosis factor α (TNFα) from PALFn- and PA-stimulated splenocytes. In addition, there was a significant increase in antigen-specific CD4+ and CD8+ T-cell counts from both PALFn- and PA-immunized mouse splenocytes. The results clearly demonstrate the ability of chimeric molecule PALFn in eliciting robust humoral and cell-mediated immune responses in mouse model that is parallel to the wild-type PA but has additional anti-LF antibody response. Considering the enhanced protection offered by the chimera PALFn, we can conclude that it can be a better alternative to the wild-type PA-based recombinant vaccine against anthrax.

A novel role of the miR‐152‐3p/ERRFI1/STAT3 pathway modulates the apoptosis and inflammatory response after acute kidney injury

“…At present, the relationship between ERRFI1 and STAT3 has only been reported by Yoo JY et al, whose research results revealed that in endometrial cancer ERRFI1 has a negative regulatory effect on the phosphorylation of STAT3 in uterine epithelial cells, thereby causing a tumor suppressive effect. [26] Over-activation of STAT3 can increase the levels of inflammatory cytokines, proapoptotic proteins, and antiapoptotic proteins in AKI mice. [27] In addition, studies in a VAN drives-AKI-to-CKD mouse model have described that EGFR/STAT3 signal-mediated VAN induces HIPK2 expression, but inhibition of HIPK2 attenuates the progression of VAN-driven AKI to CKD, which shows that STAT3 can also promote AKI to CKD.…”

Efficacy assessment of a triple anthrax chimeric antigen as a vaccine candidate in guinea pigs: challenge test with Bacillus anthracis 17 JB strain spores

“…Other study showed that a chimeric vaccine comprising LFD1 and the C-terminal domain of PA (PAD4) would offer a broader spectrum of protection compared to PA alone [4]. Another study displayed that the use of PA-LFD1 chimeric protein enhanced the humoral and cellular immune response in mice, and concluded that this protein could be a better alternative to the PA-based recombinant anthrax vaccine [12].…”

“…PA comprises a basis for all anthrax vaccines [1]. Furthermore, LF and EF also induce the production of toxin neutralizing antibodies [11][12][13]. Live attenuated vaccines, such as vaccines based on the Sterne strain (34F2), have been approved for veterinary anthrax vaccines since the 1930s while they were only used for human vaccination in the past.…”

Anthrax Vaccines in the 21st Century

“…An epitope-based vaccine comprising the D1 LF domain and PA domain 4 was found to be very protective [ 37 ]. Similarly, a chimeric vaccine containing the N-terminal region of LF and segments from PA induced the formation of antibodies recognizing PA, LF, and EF, which was similarly effective to a simple PA vaccine and also more stable [ 38 ]; a different formulation of an LF-PA vaccine was found to elicit a robust humoral response in a mouse model [ 39 ]. Finally, a triple-chimeric vaccine has been designed using the N-terminal domains of LF and EF and the C-terminal domain of PA, tested in guinea pigs with strong humoral results [ 40 ].…”