Protection In Murine Model Research Articles

Abstract P127: Protective Effects Of Protocatechuic Acid In Murine Model Of UUO-induced Renal Injury

Chronic kidney disease (CKD) is a global public health problem, affecting millions of people worldwide. CKD can result from obstructive nephropathy; a condition that arises from urinary flow obstruction in the kidneys, leading to renal inflammation and injury. Protocatechuic acid (PCA) is a natural phenolic compound that showed a promising protective effect in cardiovascular diseases. In the current study, we investigated the reno-protective effects of PCA in mice model of unilateral ureteral obstruction (UUO). Male C57BL/6J mice (10-12 weeks old) were divided into 4 groups (n=6-8/group). Sham control, Sham/P (sham plus PCA (50 mg/kg IP daily for two weeks), UUO, and UUO plus PCA. Induction of UUO significantly decreased creatinine clearance (CrCl) and increased pulse wave velocity (PWV), a marker of arterial stiffness, relative to sham control (CrCl; sham control: 60.6 ± 14 vs. UUO: 24.5 ± 6.0 ml/day and PWV; sham control: 1.58 ± 0.1 vs. UUO: 3.35 ± 0.22 m/s). Immuno-histochemical analysis revealed that KIM-1 expression, a marker of tubular injury, was elevated in UUO mice vs. sham control and PCA reduced this elevation, however there was no significance difference in urinary KIM-1 excretion. Moreover, UUO significantly increased renal oxidative stress and inflammation as evidenced by elevation in renal TBARs, IL-6, active caspase-1 and active MMP2 compared to sham control (TBARs; sham control: 8.3 ± 0.9 vs. UUO: 30.5 ± 3.33 nmol/mg protein, renal IL-6; sham control: 1 ± 0.07 vs. UUO: 24.35 ± 8.55 pg/mg protein, active caspase-1; sham control: 1.7 x 10 3 ± 95 vs. UUO: 2.79 x 10 3 ± 145 cpm/μg protein and MMP2; sham control: 1.6 ± 0.4 vs. UUO: 6 ± 0.6 ng/μg protein). PCA treatment significantly improved the UUO-induced decline in creatinine clearance (52.5 ± 10.2 ml/day) and attenuated UUO-induced elevation in renal PWV (1.95 ± 0.1 m/s). Furthermore, PCA treatment significantly decreased renal TBARs (5.2 ± 1.12 nmol/mg protein), IL-6 (5.39 ± 1.4 pg/mg protein) and active MMP2 (1.1 ± 0.3 ng/μg protein) in UUO-induced renal injury. Collectively, these data suggests that PCA provides renal protection in murine model of UUO via reduction of renal oxidative stress, inflammation and fibrosis.

CpG 1018 Is an Effective Adjuvant for Influenza Nucleoprotein.

Current influenza vaccines mainly induce neutralizing antibodies against the highly variable surface antigen hemagglutinin and require annual manufacturing and immunization. Different from surface antigens, intracellular nucleoprotein (NP) is highly conserved and has been an attractive target to develop universal T cell vaccines against influenza. Yet, influenza NP protein mainly induces humoral immune responses and lacks the ability to induce potent cytotoxic T lymphocyte (CTL) responses, key for the success of universal T cell vaccines. This study compared CpG 1018 and AddaVax to enhance recombinant NP-induced CTL responses and protection in murine models. CpG 1018 was explored to boost intradermal NP immunization, while AddaVax was explored to boost intramuscular NP immunization due to the high risk of AddaVax adjuvant to induce significant local reactions following intradermal delivery. We found CpG 1018 was highly effective to enhance NP-induced humoral and cellular immune responses superior to AddaVax adjuvant. Furthermore, CpG 1018 potentiated Th1-biased antibody responses, while AddaVax enhanced Th1/Th2-balanced antibody responses. CpG 1018 significantly enhanced IFNγ-secreting Th1 cells, while AddaVax adjuvant significantly increased IL4-secreting Th2 cells. Influenza NP immunization in the presence of CpG 1018 induced significant protection against lethal viral challenges, while influenza NP immunization in the presence of AddaVax failed to elicit significant protection. Our data validated CpG 1018 as an effective adjuvant to enhance influenza NP-induced CTL responses and protection.

Effective adjuvantation of nanograms of influenza vaccine and induction of cross-protective immunity by physical radiofrequency adjuvant.

Novel adjuvants are highly demanded to aid in development of improved or new vaccines against existing or emerging infectious diseases. Considering commonly used Alum and MF59 adjuvants induce tissue stress and release of endogenous danger signals to mediate their adjuvant effects, physical modalities may be used to induce tissue stress and endogenous danger signal release to enhance vaccine-induced immune responses. Furthermore, physical adjuvants are less likely to induce significant systemic adverse reactions due to their localized effects. Recently we found non-invasive radiofrequency (RF) pretreatment of the skin could significantly enhance intradermal vaccine-induced immune responses in murine models that included pandemic influenza vaccine, pre-pandemic vaccine, and influenza internal antigen vaccine. It remained to be explored whether the physical RF adjuvant (RFA) could be used to boost seasonal influenza vaccination, spare vaccine doses, and induce cross-protective immunity. This study found the physical RFA could significantly enhance seasonal influenza vaccine-induced immune responses against each viral strain and robustly enhance low-dose (nanograms) H3N2 vaccine-induced immune responses and protection in murine models. RFA also induced cross-protective immunity against heterologous and heterosubtypic influenza viruses. Further studies found heat shock protein 70 (inducible endogenous danger signal) and myeloid differentiation primary response 88 adaptor played a crucial role in dose-sparing effects of RFA. These data strongly support further development of the physical RFA to boost influenza vaccination.

Activation of the transcription factor NRF2 mediates the anti-inflammatory properties of a subset of over-the-counter and prescription NSAIDs

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit cyclooxygenase (COX) enzymes and are ubiquitously used for their anti-inflammatory properties. However, COX inhibition alone fails to explain numerous clinical outcomes of NSAID usage. Screening commonly used NSAIDs in primary human and murine myeloid cells demonstrated that NSAIDs could be differentiated by their ability to induce growth/differentiation factor 15 (GDF15), independent of COX specificity. Using genetic and pharmacologic approaches, NSAID-mediated GDF15 induction was dependent on the activation of nuclear factor erythroid 2-related factor 2 (NRF2) in myeloid cells. Sensing by Cysteine 151 of the NRF2 chaperone, Kelch-like ECH-associated protein 1 (KEAP1) was required for NSAID activation of NRF2 and subsequent anti-inflammatory effects both invitro and invivo. Myeloid-specific deletion of NRF2 abolished NSAID-mediated tissue protection in murine models of gout and endotoxemia. This highlights a noncanonical NRF2-dependent mechanism of action for the anti-inflammatory activity of a subset of commonly used NSAIDs.

Vaccination with chimeric protein induces protection in murine model against ascariasis

An estimated 400 million people are infected by parasites of the genus Ascaris and the existing control measures are inefficient. Vaccine development using B cell antigens is a promising strategy for increased protection against this parasite. The present study aimed at developing a chimeric protein capable of conferring protection against infection by Ascaris sp. For this purpose, we performed B-cell epitope predictions on previously described vaccine candidate proteins from Ascaris suum and the corresponding peptides were used to construct a chimeric protein. Female BALB / c mice were immunized subcutaneously in three doses at 10 day intervals with a vaccine formulation comprised of the chimeric protein together with monophosphoryl lipid A (MPLA). Control groups included protein alone, MPLA, or PBS. After challenge infection, animals vaccinated with chimeric protein plus MPLA showed a reduction of 73.54% of larval load in the lung compared to control group animals. Animals immunized with chimeric protein plus MPLA also display higher IgG response and a reduction in lung inflammation. Our study highlights how chimeric proteins containing more than one B cell epitope can enhance immune protection against helminthic infection and offer new approaches to the development of Ascaris vaccines.

Cross-lineage protection by human antibodies binding the influenza B hemagglutinin

Influenza B viruses (IBV) drive a significant proportion of influenza-related hospitalisations yet are understudied compared to influenza A. Current vaccines target the head of the viral hemagglutinin (HA) which undergoes rapid mutation, significantly reducing vaccine effectiveness. Improved vaccines to control IBV are needed. Here we developed novel IBV HA probes to interrogate humoral responses to IBV in humans. A significant proportion of IBV HA-specific B cells recognise both B/Victoria/2/87-like and B/Yamagata/16/88-like lineages in a distinct pattern of cross-reactivity. Monoclonal antibodies (mAbs) were reconstituted from IBV HA-specific B cells, including mAbs providing broad protection in murine models of lethal IBV infection. Protection was mediated by neutralising antibodies targeting the receptor binding domain, or via Fc-mediated functions of non-neutralising antibodies binding alternative epitopes including the IBV HA stem. This work defines antigenic cross-recognition between IBV lineages and provides guidance for the rational design of improved IBV vaccines for broad and durable protection.

Oral carbon monoxide therapy in murine sickle cell disease: Beneficial effects on vaso-occlusion, inflammation and anemia.

Carbon monoxide (CO) at low, non-toxic concentrations has been previously demonstrated to exert anti-inflammatory protection in murine models of sickle cell disease (SCD). However CO delivery by inhalation, CO-hemoglobin infusion or CO-releasing molecules presents problems for daily CO administration. Oral administration of a CO-saturated liquid avoids many of these issues and potentially provides a platform for self-administration to SCD patients. To test if orally-delivered CO could modulate SCD vaso-occlusion and inflammation, a liquid CO formulation (HBI-002) was administered by gavage (10 ml/kg) once-daily to NY1DD and Townes-SS transgenic mouse models of SCD. Baseline CO-hemoglobin (CO-Hb) levels were 1.6% and 1.8% in NY1DD and Townes-SS sickle mice and 0.6% in Townes-AS control mice. CO-Hb levels reached 5.4%, 4.7% and 3.0% within 5 minutes in NY1DD, SS and AS mice respectively after gavage with HBI-002. After ten treatments, each once-daily, hemoglobin levels rose from 5.3g/dL in vehicle-treated Townes-SS mice to 6.3g/dL in HBI-002-treated. Similarly, red blood cell (RBC) counts rose from 2.36 x 106/μL in vehicle-treated SS mice to 2.89 x 106/μL in HBI-002-treated mice. In concordance with these findings, hematocrits rose from 26.3% in vehicle-treated mice to 30.0% in HBI-002-treated mice. Reticulocyte counts were not significantly different between vehicle and HBI-002-treated SS mice implying less hemolysis and not an increase in RBC production. White blood cell counts decreased from 29.1 x 103/μL in vehicle-treated versus 20.3 x 103/μL in HBI-002-treated SS mice. Townes-SS mice treated with HBI-002 had markedly increased Nrf2 and HO-1 expression and decreased NF-κB activation compared to vehicle-treated mice. These anti-inflammatory effects were examined for the ability of HBI-002 (administered orally once-daily for up to 5 days) to inhibit vaso-occlusion induced by hypoxia-reoxygenation. In NY1DD and Townes-SS sickle mice, HBI-002 decreased microvascular stasis in a duration-dependent manner. Collectively, these findings support HBI-002 as a useful anti-inflammatory agent to treat SCD and warrants further development as a therapeutic.

HU-Lacking Mutants of Salmonella enterica Enteritidis Are Highly Attenuated and Can Induce Protection in Murine Model of Infection.

Salmonella enterica infection is a major public health concern worldwide, particularly when associated with other medical conditions. The serovars Typhimurium and Enteritidis are frequently associated with an invasive illness that primarily affects immunocompromised adults and children with HIV, malaria, or malnutrition. These serovars can also cause infections in a variety of animal hosts, and they are the most common isolates in poultry materials. Here, we described S. Enteritidis mutants, where hupA and hupB genes were deleted, and evaluated their potential use as live-attenuated vaccine candidates. In vitro, the mutants behaved like S. Typhimurium described previously, but there were some particularities in macrophage invasion and survival experiments. The virulence and immunogenicity of the mutant lacking both hupA and hupB (PT4ΔhupAB) were evaluated in a BALB/c mice model. This mutant was highly attenuated and could, therefore, be administrated at doses higher than 109 CFU/treatment, which was sufficient to protect all treated mice challenged with the wild-type parental strain with a single dose. Additionally, the PT4ΔhupAB strain induced production of specific IgG and IgA antibodies against Salmonella and TH1-related cytokines (IFN-γ and TNF-α), indicating that this strain can induce systemic and mucosal protection in the murine model. Additional studies are needed to better understand the mechanisms that lead to attenuation of the double-mutant PT4ΔhupAB and to elucidate the immune response induced by immunization using this strain. However, our data allow us to state that hupAB mutants could be potential candidates to be explore as live-attenuated vaccines.

Safety and biodistribution of sulfated archaeal glycolipid archaeosomes as vaccine adjuvants

ABSTRACTArchaeosomes are liposomes comprised of ether lipids derived from various archaea. Unlike conventional ester-linked liposomes, archaeosomes exhibit high pH and thermal stability. As adjuvants, archaeosomes can induce robust, long-lasting humoral and cell-mediated immune responses and enhance protection in murine models of infectious disease and cancer. Archaeosomes constituted with total polar lipids (TPL) of various archaea are relatively complex, comprising >10 different lipid compounds. Archaeosomes can be constituted with semi-synthetic glycerolipids built on ether-linked isoprenoid phytanyl cores with varied synthetic glycol- and amino-head groups. However, such semi-synthetic archaeosomes involve many synthetic steps to arrive at the final desired glycolipid composition. We have developed a novel archaeosome formulation comprising a sulfated saccharide group covalently linked to the free sn-1 hydroxyl backbone of an archaeal core lipid (sulfated S-lactosylarchaeol, SLA) mixed with uncharged glycolipid (lactosylarchaeol, LA). This new class of adjuvants can be easily synthesized and retains strong immunostimulatory activity for induction of cell-mediated immunity following systemic immunization. Herein, we demonstrate the safety of SLA/LA archaeosomes following intramuscular injection to mice and evaluate the immunogenicity, in vivo distribution and cellular uptake of antigen (ovalbumin) encapsulated into SLA/LA archaeosomes. Overall, we have found that semi-synthetic sulfated glycolipid archaeosomes are a safe and effective novel class of adjuvants capable of inducing strong antigen-specific immune responses in mice and protection against subsequent B16 melanoma tumor challenge. A key step in their mechanism of action appears to be the recruitment of immune cells to the injection site and the subsequent trafficking of antigen to local draining lymph nodes.

Abstract A65: In vivo neutralization of IL-10 enhances the antitumor effects of a therapeutic vaccine against HPV-associated tumor

Abstract Although experimental therapeutic vaccines against HPV-induced tumors are capable of activating systemic E6 and E7-specific CD8+ T cells and inducing high levels of antitumor protection in murine model, they do not always correlate with clinical efficacy once these vaccines are tested in clinical settings. This observed discrepancy can be attributed to an immunosuppressive microenvironment elicited by the tumor that limits the efficacy of immunotherapeutic approaches. Solid evidence shows that IL-10 cytokine secretion is a relevant mediator of tumor immune evasion mechanisms, which inhibits the function of CD8+ T cells. Our group has sought alternatives to potentiate the effect of a DNA-based therapeutic vaccine (pgDE7h), which encodes the HPV-16 E7 protein fused to the herpes simplex virus type 1 (HSV-1) glycoprotein D (gD), previously developed in our laboratory. The present study aimed to investigate the potential role of immunossupression restriction using a plasmid encoding the soluble IL-10 receptor (pIL10R) to enhance the pgDE7h vaccine potency in the control of tumors expressing HPV-16 E6 and E7 proteins in a murine model (TC-1 cells). Our results showed a tumor growth delay after combining the vaccine with pIL-10R. Additionally, the use of in vivo electroporation as the plasmids delivery method conferred a therapeutic protection of 90% and 60% when the animals were immunized 5 or 14 days after challenge, respectively. The combination of the plasmids was also capable of increasing substantially the numbers of activated E7-specific CD8+ T lymphocytes both systemically and at the tumor site. Altogether, the results obtained are promising for the development of new strategies to increase the antitumor therapeutic effects of the pgDE7h vaccine and may contribute to its use under clinical conditions. Note: This abstract was not presented at the conference. Citation Format: Jamile Ramos da Silva, Natiely Silva Sales, Mariangela de Oliveira Silva, Luana M. M. Aps, Luis Carlos de Souza Ferreira, Mariana de Oliveira Diniz. In vivo neutralization of IL-10 enhances the antitumor effects of a therapeutic vaccine against HPV-associated tumor [abstract]. In: Proceedings of the AACR International Conference held in cooperation with the Latin American Cooperative Oncology Group (LACOG) on Translational Cancer Medicine; May 4-6, 2017; São Paulo, Brazil. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(1_Suppl):Abstract nr A65.

In vitro evaluation of archaeosome vehicles for transdermal vaccine delivery

Archaeosomes composed of archaeal total polar lipids (TPL) or semi-synthetic analog vesicles have been used as vaccine adjuvants and delivery systems in animal models for many years. Typically administered by intramuscular or subcutaneous injections, archaeosomes can induce robust, long-lasting humoral and cell-mediated immune responses against entrapped antigens and provide protection in murine models of infectious disease and cancer. Herein, we evaluated various archaeosomes for transdermal delivery, since this route may help eliminate needle-stick injuries and needle re-use, and therefore increase patient compliance. Archaeosomes composed of TPL from different archaea (Halobacterium salinarum, Methanobrevibacter smithii, Haloferax volcanii) and various semi-synthetic glycolipid combinations were evaluated for their ability to diffuse across the skin barrier using an ex vivo pig skin model and the results were compared to conventional synthetic ester liposomes. Physicochemical characteristics were determined for selected formulations including vesicle size, size distribution, zeta potential, fluidity, antigen (ovalbumin) incorporation efficiency and release. Archaeosomes, in particular those composed of M. smithii TPL or the synthetic glycolipid sulfated S-lactosylarchaeol (SLA) mixed with uncharged glycolipid lactosyl archaeol (LA), appeared to be effective carriers for ovalbumin, achieving much better antigen distribution and vesicle accumulation in the skin epidermis than conventional liposomes. The enhanced skin permeation of archaeosomes may be attributed to their chemical structure and physicochemical properties such as particle size, surface charge, stability, and fluidity of their lipid bilayer.

Sulfated archaeal glycolipid archaeosomes as a safe and effective vaccine adjuvant for induction of cell-mediated immunity

ABSTRACTArchaeosomes are liposomal vesicles composed of ether glycerolipids unique to the domain of Archaea. Unlike conventional ester-linked liposomes, archaeosomes exhibit high stability and possess strong adjuvant and immunostimulatory properties making them an attractive vaccine delivery vehicle. Traditionally comprised of total polar lipids (TPL) or semi-synthetic phospho-glycerolipids of ether-linked isoprenoid phytanyl cores with varied glycol- and amino-head groups, archaeosomes can induce robust and long-lasting humoral and cell-mediated immune responses against antigenic cargo and provide protection in murine models of infectious disease and cancer. However, traditional TPL archaeosome formulations are relatively complex comprising several lipid species. Semi-synthetic archaeosomes tested previously contain a combination of several phospho-glycolipids (negative and neutral charged) to produce a stable, uniform-sized liposome formulation. Moreover, they involve many synthetic steps to arrive at the final desired glycolipid composition. Herein, we present a novel adjuvant formulation comprising a sulfated saccharide group covalently linked to the free sn-1 hydroxyl backbone of an archaeal core lipid (sulfated S-lactosylarchaeol, SLA). SLA individually or mixed with uncharged glyolipid (lactosylarchaeol, LA) constituted efficacious carrier vesicles for entrapped antigens (ovalbumin or melanoma associated tyrosinase-related protein 2 [TRP-2]) and induction of strong cell-mediated responses in mice and protection against subsequent B16 melanoma tumor challenge. Thus, semi-synthetic sulfated glycolipid archaeosomes represent a new class of adjuvants that will potentially ease manufacturing and scale-up, while retaining immunostimulatory activity.

Dendritic cells provide a therapeutic target for synthetic small molecule analogues of the parasitic worm product, ES-62

ES-62, a glycoprotein secreted by the parasitic filarial nematode Acanthocheilonema viteae, subverts host immune responses towards anti-inflammatory phenotypes by virtue of covalently attached phosphorylcholine (PC). The PC dictates that ES-62 exhibits protection in murine models of inflammatory disease and hence a library of drug-like PC-based small molecule analogues (SMAs) was synthesised. Four sulfone-containing SMAs termed 11a, 11e, 11i and 12b were found to reduce mouse bone marrow-derived dendritic cell (DC) pathogen-associated molecular pattern (PAMP)-induced pro-inflammatory cytokine production, inhibit NF-κB p65 activation, and suppress LPS-induced up-regulation of CD40 and CD86. Active SMAs also resulted in a DC phenotype that exhibited reduced capacity to prime antigen (Ag)-specific IFN-γ production during co-culture with naïve transgenic TCR DO.11.10 T cells in vitro and reduced their ability, following adoptive transfer, to prime the expansion of Ag-specific T lymphocytes, specifically TH17 cells, in vivo. Consistent with this, mice receiving DCs treated with SMAs exhibited significantly reduced severity of collagen-induced arthritis and this was accompanied by a significant reduction in IL-17+ cells in the draining lymph nodes. Collectively, these studies indicate that drug-like compounds that target DCs can be designed from parasitic worm products and demonstrate the potential for ES-62 SMA-based DC therapy in inflammatory disease.

Dietary Supplementation With Nonfermentable Fiber Alters the Gut Microbiota and Confers Protection in Murine Models of Sepsis.

Links between microbial alterations and systemic inflammation have been demonstrated in chronic disease, but little is known about these interactions during acute inflammation. This study investigates the effect of dietary supplementation with cellulose, a nonfermentable fiber, on the gut microbiota, inflammatory markers, and survival in two murine models of sepsis. Prospective experimental study. University laboratory. Six-week-old male C57BL/6 wild-type mice. Mice were assigned to low-fiber, normal-fiber, or high-fiber diets with or without antibiotics for 2 weeks and then subjected to sepsis by cecal ligation and puncture or endotoxin injection. Fecal samples were collected for microbiota analyses before and after dietary interventions. Mice that received a high-fiber diet demonstrated increased survival after cecal ligation and puncture relative to mice receiving low-fiber or normal-fiber diets. The survival benefit was associated with decreased serum concentration of pro-inflammatory cytokines, reduced neutrophil infiltration in the lungs, and diminished hepatic inflammation. The high-fiber diet also increased survival after endotoxin injection. Bacterial 16S ribosomal RNA gene sequences from each sample were amplified, sequenced, and analyzed. Fiber supplementation yielded an increase in relative abundance of the genera Akkermansia and Lachnospiraceae, taxa commonly associated with metabolic health. Administration of antibiotics to mice on the high-fiber diet negated the enrichment of Akkermansia species and the survival benefit after cecal ligation and puncture. Dietary supplementation with cellulose offers a microbe-mediated survival advantage in murine models of sepsis. Improved understanding of the link between diet, the microbiota, and systemic illness may yield new therapeutic strategies for patients with sepsis.

Immunogenicity and protective efficacy induced by self-amplifying mRNA vaccines encoding bacterial antigens

Nucleic acid vaccines represent an attractive approach to vaccination, combining the positive attributes of both viral vectors and live-attenuated vaccines, without the inherent limitations of each technology. We have developed a novel technology, the Self-Amplifying mRNA (SAM) platform, which is based on the synthesis of self-amplifying mRNA formulated and delivered as a vaccine. SAM vaccines have been shown to stimulate robust innate and adaptive immune responses in small animals and non-human primates against a variety of viral antigens, thus representing a safe and versatile tool against viral infections. To assess whether the SAM technology could be used for a broader range of targets, we investigated the immunogenicity and efficacy of SAM vaccines expressing antigens from Group A (GAS) and Group B (GBS) Streptococci, as models of bacterial pathogens. Two prototype bacterial antigens (the double-mutated GAS Streptolysin-O (SLOdm) and the GBS pilus 2a backbone protein (BP-2a)) were successfully expressed by SAM vectors. Mice immunized with both vaccines produced significant amounts of fully functional serum antibodies. The antibody responses generated by SAM vaccines were capable of conferring consistent protection in murine models of GAS and GBS infections. Inclusion of a eukaryotic secretion signal or boosting with the recombinant protein resulted in higher specific-antibody levels and protection. Our results support the concept of using SAM vaccines as potential solution for a wide range of both viral and bacterial pathogens, due to the versatility of the manufacturing processes and the broad spectrum of elicited protective immune response.

Zika meets its match

Both DNA and inactivated virus vaccines against Zika afford full, antibody-mediated protection in murine models.

The road to toxin-targeted therapeutic antibodies.

ABSTRACTOnce an infection by a toxin-producing bacterium is well established, therapies such as antibiotics that target bacterial growth may have little impact on the ultimate patient outcome. In such cases, toxin-neutralizing antibodies offer an opportunity to block key virulence factors. New work by A. K. Varshney, X. Wang, J. L. Aguilar, M. D. Scharff, and B. C. Fries [mBio 5(3):e01007-14, 2014, doi:10.1128/mBio.01007-14] highlights the role of the antibody isotype in determining the efficacy of toxin-neutralizing antibodies in vivo. Varshney et al. examined the role of antibody isotype for protection in murine models of staphylococcal enterotoxin B (SEB)-induced lethal shock and sepsis produced by SEB-producing Staphylococcus aureus. Murine antibodies of the IgG2a isotype were more protective than antibodies of the IgG1 and IgG2b isotypes that have identical variable regions and binding activity. These results add to the complexity inherent in the selection and optimization of antibodies for anti-infective passive immunization and emphasize the need to use relevant in vivo models to evaluate potential therapeutic monoclonal antibodies.

Although the induction of INF-γ+ CD8 T cells by radiation-attenuated Plasmodium berghei sporozoites is TAP-independent, the recall of protective effector CD8 T cells during infection requires TAP machinery (MPF6P.740)

Abstract Multiple exposures of humans and laboratory rodents to radiation-attenuated Plasmodium sporozoites (γ-spz) induce sterile and long-lasting protection that is thought to be directed mainly to liver-stage antigens (LS-Ags). Although protection involves B cells and CD4 T cells, MHC class I-dependent liver IFN-γ+ CD8 T cells are the key effectors against LS-Ags. Recently several LS-Ags have been shown to induce protection in murine models; nevertheless, the mechanism of processing and presentation of LS-Ag to CD8 T cells has not been investigated. We tested liver CD8 T cell responses induced by Plasmodium berghei (Pb) γ-spz in TAP-/- mice to inquire whether processing/presentation of the exogenous LS-Ags was TAP-dependent or -independent. Immunization with Pb γ-spz induced proliferation and IFN-γ production by liver CD8 T cells. Also, TAP-/- CD8 T cells eliminated hepatocytes infected with Pb sporozoites in vitro. Despite these effector activities, Pb γ-spz immunized TAP-/- mice were not protected against sporozoite infection, mainly because liver CD8 T effector cells failed to produce IFN-γ in response to infectious sporozoite challenge. Our results demonstrate that although TAP-independent vacuolar pathway operates efficiently during immunization with γ-spz, the TAP-associated phagosomal-to-cytosol antigen processing mechanism appears to be required for effective recall of effector CD8 T cells during infection. The implications of these findings will be discussed.

Irradiated wild-type andSpamutantStaphylococcus aureusinduce anti-S. aureusimmune responses in mice which do not protect against subsequent intravenous challenge

Staphylococcus aureus remains an important human and animal pathogen. Its pathogenicity is determined in part by expression of the Spa-immune subversion protein, neutralising the activity of which provides partial protection in murine models, as does experimental infection with live S. aureus with Spa gene deletions followed by antibiotic-mediated cure in mice. Together, these data raise the question of whether Spa mutant S. aureus might represent a viable vaccine. Here, we find that gamma-irradiated S. aureus strains, both wild-type and null mutant of spa, are immunogenic in mice when administered intramuscularly, eliciting large amounts of anti-S. aureus antibodies, as judged by whole-cell immunoassay on fixed microorganisms. We used an intravenous challenge system to assess vaccine efficacy, the sensitivity of which was increased by studying renal bacterial concentrations in both kidneys. Despite this, protection from intravenous challenge was not observed (mean difference between vaccinated and unvaccinated mice 0.27 log(10) with 95% confidence interval -0.922 to 1.467). Surprisingly, antibody responses elicited against a panel of protective cell surface proteins were very low, indicating that most antibody induced is not protective. Additionally, these data suggest a limited role for irradiated wild-type or spa mutant S. aureus as vaccines.

Abstract 1240: A flexible antibody-based strategy targeting CD71 for the treatment of AIDS-related non-Hodgkin's lymphoma.

Abstract AIDS related non-Hodgkin's lymphoma (AIDS-NHL) remains a significant clinical problem in the era of effective multiple-agent highly active anti-retroviral therapy (HAART). While an overall decrease in the incidence of AIDS-NHL has been seen in the HAART era, the risk for AIDS-NHL remains elevated, and not all AIDS-NHL subtypes have decreased in incidence, with the incidence of Burkitt's lymphoma (BL) remaining unchanged. In fact, AIDS-NHL is now the most common AIDS-related cancer in developed countries, where NHL accounts for 23-30% of all AIDS-related deaths. We have previously developed an antibody-avidin fusion protein (ch128.1Av) specific for the human transferrin receptor 1 (TfR1/CD71), a receptor that is overexpressed on cancer cells due to their high demand for iron. This fusion protein exhibits an increased in vitro cytotoxicity against malignant hematopoietic cells compared to the parental antibody without avidin (ch128.1). This cytotoxicity is due to the ability of ch128.1Av to decrease cell surface TfR1, triggering its intracellular sequestration and degradation, with the subsequent induction of lethal iron deprivation. However, both ch128.1Av and ch128.1 confer protection in murine models of human disseminated multiple myeloma. ch128.1Av is also a universal delivery system and its cytotoxicity can be further enhanced by its conjugation with biotinylated drugs making it a unique molecule capable of a two-pronged attack against malignant cells through drug delivery and direct cytotoxic activity through iron starvation. The main goal of this study is to evaluate the potential use of ch128.1Av alone and as a delivery vehicle as a possible AIDS-NHL therapy. We found that, when used alone, ch128.1Av exhibits significant cytotoxic activity against two representative AIDS-NHL cell lines: 2F7 (AIDS-Burkitt's NHL) and RRBL (AIDS-diffuse large B-cell lymphoma). Importantly, the level of cytotoxicity was similar to that observed using the highly sensitive human B lymphoblastoid cell line IM-9. In addition, the cytotoxicity dramatically increases when this fusion protein is conjugated to biotinylated saporin 6 (b-SO6), a plant ribosome inactivating protein that blocks protein synthesis, resulting in an immunotoxin. We also found that non-activated (resting) B cells isolated from the peripheral blood of healthy individuals are resistant to ch128.1Av, but sensitive to ch128.1Av complexed to b-SO6, which can be explained by the different mechanisms of action of the fusion protein alone (iron starvation) and that of the immunotoxin (protein synthesis inhibition). We have previously reported ch128.1Av alone, or complexed to b-SO6, are not toxic to normal human hematopoietic stem cells, which can be explained by the lack of TfR1 expression on such cells. Our results suggest the potential use of anti-TfR1 antibody-mediated approaches as therapeutic interventions against AIDS-NHL. Citation Format: Tracy R. Daniels-Wells, Lai Sum Leoh, Daniel Widney, Dharma R. Thapa, Jose Leon Merino, Larry Magpantay, Otoniel Martínez-Maza, Manuel L. Penichet. A flexible antibody-based strategy targeting CD71 for the treatment of AIDS-related non-Hodgkin's lymphoma. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1240. doi:10.1158/1538-7445.AM2013-1240