Characterization of prostanoids response to Bordetella pertussis antigen BscF and Tdap in LPS-challenged monocytes

Prostanoids are potent inflammatory mediators that play a regulatory role in the innate immune activation of the adaptive immune response to determine the duration of protection against infection. We aim to quantify the modulation of prostanoids profiles in lipopolysaccharide (LPS)-stimulated THP-1 cells treated with the novel pertussis antigen BscF. We compared the effect with pertussis antigens present in the current Tdap vaccine to understand the immunomodulatory effect that might contribute to the diminished Tdap vaccine effectiveness. The inflammatory challenge with LPS induced a robust elevation of most prostanoid family members compared to the control treatment. Treatment with BscF and Tdap significantly reduced the LPS-stimulated elevation of prostaglandins (PGs) D2, E2, and F2α, as well as thromboxane (TX) A2 levels. An opposite trend was observed for PGI2, as both antigens accelerated the LPS-stimulated upregulation. Further, we quantified cyclooxygenases (COXs) that catalyze the biosynthesis of prostanoids and found that both antigens significantly reduced LPS-stimulated COX-1 and COX-2, demonstrating that the waning of acellular pertussis vaccines' protective immunity may be due to other downstream enzymes not related to COXs. Our present study validates the potential role of BscF as an adjuvant, resulting in the next-generation pertussis vaccine discovery.

Dengue virus specific IgY provides protection following lethal dengue virus challenge and is neutralizing in the absence of inducing antibody dependent enhancement

Dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS) are severe disease manifestations that can occur following sequential infection with different dengue virus serotypes (DENV1-4). At present, there are no licensed therapies to treat DENV-induced disease. DHF and DSS are thought to be mediated by serotype cross-reactive antibodies that facilitate antibody-dependent enhancement (ADE) by binding to viral antigens and then Fcγ receptors (FcγR) on target myeloid cells. Using genetically engineered DENV-specific antibodies, it has been shown that the interaction between the Fc portion of serotype cross-reactive antibodies and FcγR is required to induce ADE. Additionally, it was demonstrated that these antibodies were as neutralizing as their non-modified variants, were incapable of inducing ADE, and were therapeutic following a lethal, antibody-enhanced infection. Therefore, we hypothesized that avian IgY, which do not interact with mammalian FcγR, would provide a novel therapy for DENV-induced disease. We demonstrate here that goose-derived anti-DENV2 IgY neutralized DENV2 and did not induce ADE in vitro. Anti-DENV2 IgY was also protective in vivo when administered 24 hours following a lethal DENV2 infection. We were also able to demonstrate via epitope mapping that both full-length and alternatively spliced anti-DENV2 IgY recognized different epitopes, including epitopes that have not been previously identified. These observations provide evidence for the potential therapeutic applications of goose-derived anti-DENV2 IgY.

Purified type III secretion system needle proteins are novel TLR agonists that induce NF-κB signaling and stimulate NLRP3-dependent IL-1β production by innate cells in vitro

Purified type III secretion (T3S) system needle proteins from a number of Gram-negative bacteria have been identified as protective antigens as well as strong adjuvants in vivo. These proteins have been shown to act as TLR2 and TLR4 agonists, producing robust pro-inflammatory cytokine release in a MyD88-dependant manner from both human and mouse cells in vitro. Additionally, it has been established that TLR agonists alone can stimulate IL-1β through the NLRP3 inflammasome. Interestingly, we have demonstrated that T3S needle proteins induce NF-κB signaling downstream of both TLR2 and TLR4. Given the vaccine potential of T3S needle proteins, it is necessary to further understand the signaling mechanisms underlying their adjuvant properties. Here we characterized the innate signaling pathways engaged by T3S needle proteins. We show T3S needle proteins induce NF-κB signaling and pro-inflammatory cytokine release from mouse macrophages more strongly through TLR4 as compared to TLR2. Utilizing primary cells from inflammasome component knockout mice, we demonstrate that IL-1β secretion from T3S needle protein stimulated cells was dependent on the NLRP3 inflammasome, as well as caspase-1. Interestingly, pre-treatment with cytochalasin D reduced IL-1β secretion and resulted in the accumulation of intracellular pro-IL-1β after T3S needle protein stimulation; suggesting that internalization of T3S needle proteins is critical for inflammasome activation and IL-1β secretion. These findings further identify critical innate signaling pathways engaged by T3S needle proteins. T3S needle proteins have tremendous vaccine potential due to their ability to act as protective antigens and their innate immunity stimulating properties.

Humanized HLA-DQ8αβ transgenic mice treated with SEG/SEI superantigens exhibit long-term CD4+-mediated anti-tumor responses

SEG and SEI are primordial S. aureus superantigens (SAgs) notably unaccompanied by human neutralizing antibodies that have hampered the use of classic SAgs as cancer therapeutics. Here we show SEG/SEI presented from a HLA-DQ8αβ (HLA-DQA*0301 and HLA-DQB*0302) tg platform outperform C57BL/6 mice in achieving long term survival in vaccinated and established Lewis lung carcinoma (LLC) and B16-F10 melanoma. Vaccination of DQ8 tg mice with LLC or B16-F10 melanoma followed by SEG/SEI immunization and subsequent tumor challenge resulted in 100% and 83% survival for >150 days respectively, compared to a median survival of 14 days in unvaccinated DQ8 tg controls (p<0.001). Likewise, SEG/SEI treatment of established melanoma in DQ8 tg mice resulted in 100% survival for 70 days compared to a median survival of 20 days in untreated DQ8 tg controls. Similar vaccinations/challenges in C57BL/6 mice produced a median survival of 23–28 days. SEG/SEI-activated splenocytes from DQ8 tg mice displayed a TH-1/TH-17 cytokine phenotype with a threefold greater T cell proliferative and CD4+-mediated cytotoxicity responses, compared to C57BL/6 mice. These surprising data delineate a clear pathway to translation of an SEG/SEI-HLA-DQ8αβ tg platform for melanoma/lung cancer prophylaxis and treatment.

Expression and Purification of N-Terminally His-Tagged Recombinant Type III Secretion Proteins

The ability to express and purify recombinant needle proteins from the Type III Secretion System (T3SS) of many gram-negative bacteria has allowed us to develop novel experimental approaches, both in vitro and in vivo, to identify unique roles for T3SS in bacterial pathogenesis. In addition, these purified needle proteins have shown to be promising immunotherapies acting as both protective antigens and adjuvants, presumably due to their immune activating properties. Here, we describe the expression and purification of recombinant T3SS needle proteins.

Mouse Immunization with Purified Needle Proteins from Type III Secretion Systems and the Characterization of the Immune Response to These Proteins

Many Gram-negative pathogens utilize a type III secretion (T3S) system to directly deliver effector molecules into host eukaryotic cells to manipulate cellular processes. These surface-exposed syringe-like structures are highly conserved, necessary for pathogenesis, and hence are therapeutic targets against a number of Gram-negative pathogens. Here we describe a protocol for using purified needle proteins to immunize mice, and subsequently, ways to characterize the immune response to immunization.

BscF from Bordetella pertussis provides advantageous adjuvant activity when paired with the acellular pertussis vaccine: enhanced Th1/Th17 pertussis-specific immune response

Incidence of pertussis, a severe respiratory disease caused by Bordetella pertussis, have been on the rise. This resurgence has been linked to antigenic divergence in circulating pertussis strains as well as waning or ineffective immunity induced by the current acellular pertussis (aP) vaccine. The current aP vaccine replaced a whole cell pertussis (wP) vaccine in the 1990s due to adverse events associated with the wP vaccine. Alum-absorbed aP vaccine has been shown to elicit a strong antibody response and considerable Th2 type CD4+ T cells. In contrast, wP vaccine promotes Th1/Th17 type cellular immunity and associated opsonizing antibodies presumably via its PAMPs. We have previously demonstrated that BscF, a B. pertussis needle protein, acts as a strong TLR agonist. Here we characterized the contribution of BscF to a laboratory prepared aP vaccine-induced response. aP + BscF resulted in statistically greater pertussis-specific antibody titers, compared to sham aP + PBS. BscF enhanced long-term aP-specific immunity, compared to either the alum or sham controls, as measured by increased numbers of central memory T cells. Moreover, the addition of BscF resulted in skewing the pertussis-specific immunity toward Th1 and Th17 responses, compared to the addition of alum or PBS which skewed pertussis-specific immunity away from Th1/Th17 responses. Mice immunized with aP + BscF demonstrated significantly reduced bacterial burden in their lungs 5 dpi. These findings suggest that BscF induced a strong Th1 and Th17 anti-pertussis response, potentially may provide protective BscF-specific immunity, and could be a novel additional component in the next generation aP vaccine.

The N terminus of Yersinia pestis’ YscF masks YscF’s naturally occurring PAMP, inhibiting inflammation and allowing for colonization in vivo

Type III secretion (T3S) systems, common to many Gram- bacteria, act as a needle to deliver virulence factors directly into eukaryotic cells, often modulating host immunity. Multimers of YscF polymerize to form the surface-located T3S needle-like structure. We have previously shown that YscF has PAMP properties, acting as both a TLR2 and TLR4 agonist. We have also shown that modulation of this PAMP activity in vitro is located in the N terminus of YscF. We hypothesized that the N terminus of YscF contributes to Y. pestis survival within the eukaryotic host. We generated a 15 amino acid N terminal truncation of YscF (delta15YscF) expressed in Y. pestis. The truncation did not affect T3S system translocation. The delta15YscF Y. pestis strain was able to secrete Yops, albeit at a level lower than wild type (wt) Y. pestis. As expected, wt Y. pestis colonized the spleen and liver, whereas delta15YscF Y. pestis exhibited significantly impaired colonization in both organs. Mice infected with delta15YscF Y. pestis developed significantly more inflammation compared to wt Y. pestis. At 3 days p.i., delta15YscF spleen weights were significantly heavier and spleen inflammation was accompanied by a significant enhancement of macrophage and neutrophil migration compared to wt mice. These data support a role for the N terminus of YscF contributing to host bacterial clearance. Truncating the N terminus may result in a PAMP which is thereby unmasked and able to induce an inflammatory response.

Staphylococcal enterotoxin G and I: augmenting the T cell response to murine melanoma

Staphylococcal enterotoxins (SEs) have been shown to be effectual proteins which demonstrate anti-tumor activity. SEG and SEI, produced from the enterotoxin gene cluster (egc) of Staphylococcal aureus, activate T cells with Vβ specificity to elicit robust T cell proliferation, T helper cell 1 (TH1) and TH2 cytokine secretion, and nitric oxide dependent tumor lysis. Our data highlight the effects of SE stimulated T cells and the subsequent consequence on aggressive, metastatic cancer progression using B16-F10 murine melanoma model. Specifically, we explore the differences between major histocompatibility complex (MHC) and human leukocyte antigen (HLA) SE presentation to the T cells via the T cell receptor (TCR). Our data demonstrates increased survival of B16-F10 tumor bearing mice, C57BL/6 and DQ8 (HLA-DQA1*0301, HLA-DQB1*0302) transgenic mice, after irradiated B16-F10 vaccination and SE stimulation. Interestingly, SEG and SEI induce strong T cell proliferation yet do not induce neutralizing antibodies to the extent of classical SEs, SEA and SEB, nor induce autoimmune pathology. Our findings demonstrate that superantigen administration enhances lymphocytic tumor killing and suggest a potential role for SEG and SEI as potent immunotherapeutics for human cancer.