A clade C HIV-1 vaccine protects against heterologous SHIV infection by modulating IgG glycosylation and T helper response in macaques

The rising global HIV-1 burden urgently requires vaccines capable of providing heterologous protection. Here, we developed a clade C HIV-1 vaccine consisting of priming with modified vaccinia Ankara (MVA) and boosting with cyclically permuted trimeric gp120 (CycP-gp120) protein, delivered either orally using a needle-free injector or through parenteral injection. We tested protective efficacy of the vaccine against intrarectal challenges with a pathogenic heterologous clade C SHIV infection in rhesus macaques. Both routes of vaccination induced a strong envelope-specific IgG in serum and rectal secretions directed against V1V2 scaffolds from a global panel of viruses with polyfunctional activities. Envelope-specific IgG showed lower fucosylation compared with total IgG at baseline, and most of the vaccine-induced proliferating blood CD4⁺ T cells did not express CCR5 and α4β7, markers associated with HIV target cells. After SHIV challenge, both routes of vaccination conferred significant and equivalent protection, with 40% of animals remaining uninfected at the end of six weekly repeated challenges with an estimated efficacy of 68% per exposure. Induction of envelope-specific IgG correlated positively with G1FB glycosylation, and G2S2F glycosylation correlated negatively with protection. Vaccine-induced TNF-α⁺ IFN-γ⁺ CD8⁺ T cells and TNF-α⁺ CD4⁺ T cells expressing low levels of CCR5 in the rectum at prechallenge were associated with decreased risk of SHIV acquisition. These results demonstrate that the clade C MVA/CycP-gp120 vaccine provides heterologous protection against a tier2 SHIV rectal challenge by inducing a polyfunctional antibody response with distinct Fc glycosylation profile, as well as cytotoxic CD8 T cell response and CCR5-negative T helper response in the rectum.

Comparative Evaluation of Prophylactic SIV Vaccination Modalities Administered to the Oral Cavity

Attempts to develop a protective human immunodeficiency virus (HIV) vaccine have had limited success, especially in terms of inducing protective antibodies capable of neutralizing different viral strains. As HIV transmission occurs mainly via mucosal surfaces, HIV replicates significantly in the gastrointestinal tract, and the oral route of vaccination is a very convenient one to implement worldwide, we explored three SIV vaccine modalities administered orally and composed of simian immunodeficiency virus (SIV) DNA priming with different boosting immunogens, with the goal of evaluating whether they could provide lasting humoral and cellular responses, including at mucosal surfaces that are sites of HIV entry. Twenty-four Cynomolgus macaques (CyM) were primed with replication-incompetent SIV DNA provirus and divided into three groups for the following booster vaccinations, all administered in the oral cavity: Group 1 with recombinant SIV gp140 and Escherichia coli heat-labile toxin adjuvant dmLT, Group 2 with recombinant SIV-Oral Poliovirus (SIV-OPV), and Group 3 with recombinant SIV-modified vaccinia ankara (SIV-MVA). Cell-mediated responses were measured using blood, lymph node, rectal and vaginal mononuclear cells. Significant levels of systemic and mucosal T-cell responses against Gag and Env were observed in all groups. Some SIV-specific plasma IgG, rectal and salivary IgA antibodies were generated, mainly in animals that received SIV DNA + SIV-MVA, but no vaginal IgA was detected. Susceptibility to infection after SIVmac251 challenge was similar in vaccinated and nonvaccinated animals, but acute infection viremia levels were lower in the group that received SIV DNA + SIV-MVA. Nonvaccinated CyM maintained central memory and total CD4+ T-cell levels in the normal range during the 5 months of postinfection follow-up as did the vaccinated animals, precluding evaluation of vaccine impact on disease progression. We conclude that the oral cavity vaccination tested in these regimens can stimulate cell-mediated immunity systemically and mucosally, but humoral response stimulation was limited with the doses and the vaccine platforms used.

Enterotoxigenic Escherichia coli Heat-Stable Toxin Increases the Rate of Zinc Release from Metallothionein and Is a Zinc- and Iron-Binding Peptide

Enterotoxigenic Escherichia coli (ETEC) is a major diarrheal pathogen in children in low- to middle-income countries. Previous studies have identified heat-stable enterotoxin (ST)-producing ETEC as one of the major diarrhea-causing pathogens in children younger than five years. In this study, we examined iron and zinc binding by both human and porcine ST variants and determined how host metallothionein could detoxify ST. We found that ST purified from ETEC culture supernatants eluted as a doublet during C18 reverse-phase chromatography. Leading edge fractions of the ST doublet were found to be devoid of iron, while trailing edge fractions of the ST doublet were found to contain measurable iron. Next, we found that purified ST could be reconstituted with iron under reducing and anaerobic conditions, and iron-bound ST attenuated the induction of cGMP in T84 epithelial cells. Moreover, we demonstrated that supernatants of ETEC 214-4 grown under increasing iron concentrations were only able to induce cGMP at iron concentrations greater than 5 μM. In vitro studies also demonstrated that ST binds zinc, and once bound, zinc removal from ST required denaturing conditions. Zinc-bound ST also failed to induce cGMP. We found that ST contributes disulfide bonds to the perceived oxidized glutathione pool, increases the rate of zinc release from metallothionein, and can be detoxified by metallothionein. Lastly, we showed ST induces transcriptional changes in genes previously shown to be regulated by deferoxamine. These studies demonstrate ST ETEC pathogenesis may be tied intimately to host mucosal metal status.IMPORTANCE Enterotoxigenic Escherichia coli (ETEC) is a major diarrheal pathogen in children in low- to middle-income countries, deployed military personnel, and travelers to regions of endemicity. The heat-stable toxin (ST) is a small nonimmunogenic secreted peptide with 3 disulfide bonds. It has been appreciated that dietary disulfides modulate intestinal redox potential and that ST could be detoxified using exogenous reductants. Using biochemical and spectroscopic approaches, we demonstrated that ST can separately bind iron and zinc under reducing conditions, thereby reducing ST toxicity. Moreover, we demonstrated that ST modulates the glutathione (GSH)/oxidized glutathione (GSSG) ratio and that ST should be considered a toxin oxidant. ST can be detoxified by oxidizing zinc-loaded metallothionine, causing free zinc to be released. These studies help lay a foundation to understand how diarrheal pathogens modulate intestinal redox potential and may impact how we design therapeutics and/or vaccines for the pathogens that produce them.

Live attenuated enterotoxigenic Escherichia coli (ETEC) vaccine with dmLT adjuvant protects human volunteers against virulent experimental ETEC challenge

Background

There is no licensed vaccine against enterotoxigenic Escherichia coli (ETEC), a major cause of diarrhea-associated morbidity and mortality among infants and children in low-income countries and travelers. The results of this vaccination/challenge study demonstrate strong protection by an attenuated ETEC vaccine candidate, ACE527, when co-administered with a mucosal adjuvant, the double-mutant heat-labile toxin (dmLT) of ETEC.

Methods

Sixty healthy adults participated in a randomized, placebo-controlled, double-blind study with three doses of lyophilized ACE527 (∼3 × 10⁹ of each strain per dose) administered orally with or without dmLT adjuvant (25 µg/dose). Six months later, 36 of these volunteers and a control group of 21 unvaccinated volunteers were challenged with virulent ETEC strain H10407. The primary outcome was severe diarrhea, defined as passing >800 g of unformed stools during the inpatient period following challenge.

Findings

The vaccine was well tolerated and induced robust immune responses to key antigens. The protective efficacy (PE) against the primary outcome of severe diarrhea was 65.9% (95% confidence interval [CI] 5.4–87.7, p = 0.003). Among subjects receiving the adjuvanted vaccine, the attack rate of severe diarrhea was 23.1, while in unimmunized controls it was 67.7%. The PE against diarrhea of any severity was 58.5% (95% CI 3.8– 82.1, p = 0.016). There was a strong inverse correlation between shedding of the vaccine strain after either of the first two doses and absence of severe diarrhea upon challenge (RR = 0.29, 95% CI 0.08–1.05, p = 0.041). Challenge strain shedding was 10-fold lower in those receiving the adjuvant than in those receiving vaccine alone. The unadjuvanted vaccine was not protective (PE = 23.1%).

Interpretation

The results of this study support further development of ACE527 + dmLT as a vaccine for children in endemic countries and travelers. This is the first clinical demonstration that dmLT can contribute significantly to vaccine efficacy and may warrant testing with other oral vaccines.

(ClinicalTrials.gov registration: NCT01739231).

Exposure-response analysis of blinatumomab in patients with relapsed/refractory acute lymphoblastic leukaemia and comparison with standard of care chemotherapy

Aims

The relationship between blinatumomab exposure and efficacy endpoints (occurrence of complete remission [CR] and duration of overall survival [OS]) or adverse events (occurrence of cytokine release syndrome [CRS] and neurological events) were investigated in adult patients with relapsed/refractory acute lymphoblastic leukaemia (r/r ALL) receiving blinatumomab or standard of care (SOC) chemotherapy to evaluate appropriateness of the blinatumomab dosing regimen.

Methods

Exposure, efficacy and safety data from adult patients (n = 646) with r/r ALL receiving stepwise (9 then 28 μg/day, 4‐week cycle) continuous intravenous infusion (n = 537) of blinatumomab or SOC (n = 109) chemotherapy were pooled from phase 2 and 3 studies. The occurrence of CR, neurological and CRS events, and duration of OS were analysed using Cox proportional hazards models or logistic regression, as appropriate. Confounding factors were tested multivariately as needed.

Results

Blinatumomab steady‐state concentration following 28 μg/day dosing was associated with the probability of achieving CR (odds ratio and 95% confidence interval: 1.073 [1.033–1.114]), and a longer duration of OS compared to SOC (hazard ratio and 95% confidence interval: 0.954 [0.936–0.973], P < .05) in multivariate analyses. The exposure–safety analyses indicated that blinatumomab steady‐state concentration following the 9 or 28 μg/day dose was not associated with increased probability of CRS or neurological events, after accounting for blinatumomab treatment effect (P > .05).

Conclusions

Blinatumomab step‐dosing regimen of 9/28 μg/day provided treatment benefit in achieving CR and increasing the duration of OS over SOC and was appropriate in management of CRS and neurological events in patients with r/r ALL.

Intradermal vaccination with a Pseudomonas aeruginosa vaccine adjuvanted with a mutant bacterial ADP-ribosylating enterotoxin protects against acute pneumonia

Respiratory infections are a leading cause of morbidity and mortality globally. This is partially due to a lack of effective vaccines and a clear understanding of how vaccination route and formulation influence protective immunity in mucosal tissues such as the lung. Pseudomonas aeruginosa is an opportunistic pathogen capable of causing acute pulmonary infections and is a leading cause of hospital-acquired and ventilator-associated pneumonia. With multidrug-resistant P. aeruginosa infections on the rise, the need for a vaccine against this pathogen is critical. Growing evidence suggests that a successful P. aeruginosa vaccine may require mucosal antibody and Th1- and Th17-type CD4⁺ T cells to prevent pulmonary infection. Intradermal immunization with adjuvants, such as the bacterial ADP-Ribosylating Enterotoxin Adjuvant (BARE) double mutant of E. coli heat-labile toxin (dmLT), can direct protective immune responses to mucosal tissues, including the lungs. We reasoned that intradermal immunization with P. aeruginosa outer membrane proteins (OMPs) adjuvanted with dmLT could drive neutralizing antibodies and migration of CD4⁺ T cells to the lungs and protect against P. aeruginosa pneumonia in a murine model. Here we show that mice immunized with OMPs and dmLT had significantly more antigen-specific IgG and Th1- and Th17-type CD4⁺ memory T cells in the pulmonary environment compared to control groups of mice. Furthermore, OMPs and dmLT immunized mice were significantly protected against an otherwise lethal lung infection. Protection was associated with early IFN-γ and IL-17 production in the lungs of immunized mice. These results indicate that intradermal immunization with dmLT can drive protective immunity to the lung mucosa and may be a viable vaccination strategy for a multitude of respiratory pathogens.

The Mucosal Vaccine Adjuvant LT(R192G/L211A) or dmLT

Perhaps the best-studied mucosal adjuvants are the bacterially derived ADP-ribosylating enterotoxins. This adjuvant family includes heat-labile enterotoxin of Escherichia coli (LT), cholera toxin (CT), and mutants or subunits of LT and CT. These proteins promote a multifaceted antigen-specific response, including inflammatory Th1, Th2, Th17, cytotoxic T lymphocytes (CTLs), and antibodies. However, more uniquely among adjuvant classes, they induce antigen-specific IgA antibodies and long-lasting memory to coadministered antigens when delivered mucosally or even parenterally. The purpose of this minireview is to describe the general properties, history and creation, preclinical studies, clinical studies, mechanisms of action, and considerations for use of the most promising enterotoxin-based adjuvant to date, LT(R192G/L211A) or dmLT. This review is timely due to completed, ongoing, and planned clinical investigations of dmLT in multiple vaccine formulations by government, nonprofit, and industry groups in the United States and abroad.

Adjuvant selection regulates gut migration and phenotypic diversity of antigen-specific CD4+ T cells following parenteral immunization

Infectious diarrheal diseases are the second leading cause of death in children under 5 years, making vaccines against these diseases a high priority. It is known that certain vaccine adjuvants, chiefly bacterial ADP-ribosylating enterotoxins, can induce mucosal antibodies when delivered parenterally. Based on this, we reasoned vaccine-specific mucosal cellular immunity could be induced via parenteral immunization with these adjuvants. Here, we show that, in contrast to the Toll-like receptor-9 agonist CpG, intradermal immunization with non-toxic double-mutant heat-labile toxin (dmLT) from enterotoxigenic Escherichia coli drove endogenous, antigen-specific CD4⁺ T cells to expand and upregulate the gut-homing integrin α4β7. This was followed by T-cell migration into gut-draining lymph nodes and both small and large intestines. We also found that dmLT produces a balanced T-helper 1 and 17 (Th1 and Th17) response, whereas T cells from CpG immunized mice were predominantly Th1. Immunization with dmLT preferentially engaged CD103⁺ dendritic cells (DCs) compared with CpG, and mice deficient in CD103⁺ DCs were unable to fully license antigen-specific T-cell migration to the intestinal mucosae following parenteral immunization. This work has the potential to redirect the design of existing and next generation vaccines to elicit pathogen-specific immunity in the intestinal tract with non-mucosal immunization.

Evaluation in mice of a conjugate vaccine for cholera made from Vibrio cholerae O1 (Ogawa) O-specific polysaccharide

Background

Protective immunity against cholera is serogroup specific. Serogroup specificity in Vibrio cholerae is determined by the O-specific polysaccharide (OSP) of lipopolysaccharide (LPS). Generally, polysaccharides are poorly immunogenic, especially in young children.

Methodology

Here we report the evaluation in mice of a conjugate vaccine for cholera (OSP:TThc) made from V. cholerae O1 Ogawa O-Specific Polysaccharide–core (OSP) and recombinant tetanus toxoid heavy chain fragment (TThc). We immunized mice intramuscularly on days 0, 21, and 42 with OSP:TThc or OSP only, with or without dmLT, a non-toxigenic immunoadjuvant derived from heat labile toxin of Escherichia coli.

Principal Findings

We detected significant serum IgG antibody responses targeting OSP following a single immunization in mice receiving OSP:TThc with or without adjuvant. Anti-LPS IgG responses were detected following a second immunization in these cohorts. No anti-OSP or anti-LPS IgG responses were detected at any time in animals receiving un-conjugated OSP with or without immunoadjuvant, and in animals receiving immunoadjuvant alone. Responses were highest following immunization with adjuvant. Serum anti-OSP IgM responses were detected in mice receiving OSP:TThc with or without immunoadjuvant, and in mice receiving unconjugated OSP. Serum anti-LPS IgM and vibriocidal responses were detected in all vaccine cohorts except in mice receiving immunoadjuvant alone. No significant IgA anti-OSP or anti-LPS responses developed in any group. Administration of OSP:TThc and adjuvant also induced memory B cell responses targeting OSP and resulted in 95% protective efficacy in a mouse lethality cholera challenge model.

Conclusion

We describe a protectively immunogenic cholera conjugate in mice. Development of a cholera conjugate vaccine could assist in inducing long-term protective immunity, especially in young children who respond poorly to polysaccharide antigens.

Cholera is a severe dehydrating diarrheal illness of humans caused by organisms Vibrio cholerae serogroups O1 or O139 serogroup organisms. Protective immunity against cholera is serogroup specific. Serogroup specificity in V. cholerae is determined by the O-specific polysaccharide (OSP) of lipopolysaccharide (LPS). Generally, polysaccharides are poorly immunogenic, especially in young children. Unfortunately, children bear a large burden of cholera globally. Here we describe a novel cholera conjugate vaccine and show that it induces immune responses in mice, including memory responses, to OSP, the T cell-independent antigen that probably is the target of protective immunity to cholera. These responses were highest following immunization of the vaccine with a novel immunoadjuvant, dmLT. We also show that immunization of mice with this conjugate vaccine protects against challenge with wild-type V. cholerae. A protectively immunogenic cholera conjugate vaccine that induces long-term memory responses could have particular utility in young children who are most at risk of cholera.

Serum and mucosal antibody responses to inactivated polio vaccine after sublingual immunization using a thermoresponsive gel delivery system

Administering vaccines directly to mucosal surfaces can induce both serum and mucosal immune responses. Mucosal responses may prevent establishment of initial infection at the port of entry and subsequent dissemination to other sites. The sublingual route is attractive for mucosal vaccination, but both a safe, potent adjuvant and a novel formulation are needed to achieve an adequate immune response. We report the use of a thermoresponsive gel (TRG) combined with a double mutant of a bacterial heat-labile toxin (dmLT) for sublingual immunization with a trivalent inactivated poliovirus vaccine (IPV) in mice. This TRG delivery system, which changes from aqueous solution to viscous gel upon contact with the mucosa at body temperature, helps to retain the formulation at the site of delivery and has functional adjuvant activity from the inclusion of dmLT. IPV was administered to mice either sublingually in the TRG delivery system or intramuscularly in phosphate-buffered saline. We measured poliovirus type-specific serum neutralizing antibodies as well as polio-specific serum Ig and IgA antibodies in serum, saliva, and fecal samples using enzyme-linked immunosorbent assays. Mice receiving sublingual vaccination via the TRG delivery system produced both mucosal and serum antibodies, including IgA. Intramuscularly immunized animals produced only serum neutralizing and binding Ig but no detectable IgA. This study provides proof of concept for sublingual immunization using the TRG delivery system, comprising a thermoresponsive gel and dmLT adjuvant.

Evaluation of immunogenicity and protective efficacy of orally delivered Shigella type III secretion system proteins IpaB and IpaD

Shigella spp. are food- and water-borne pathogens that cause shigellosis, a severe diarrheal and dysenteric disease that is associated with a high morbidity and mortality in resource-poor countries. No licensed vaccine is available to prevent shigellosis. We have recently demonstrated that Shigella invasion plasmid antigens (Ipas), IpaB and IpaD, which are components of the bacterial type III secretion system (TTSS), can prevent infection in a mouse model of intranasal immunization and lethal pulmonary challenge. Because they are conserved across Shigella spp. and highly immunogenic, these proteins are excellent candidates for a cross-protective vaccine. Ideally, such a vaccine could be administered to humans orally to induce mucosal and systemic immunity. In this study, we investigated the immunogenicity and protective efficacy of Shigella IpaB and IpaD administered orally with a double mutant of the Escherichia coli heat labile toxin (dmLT) as a mucosal adjuvant. We characterized the immune responses induced by oral vs. intranasal immunization and the protective efficacy using a mouse pulmonary infection model. Serum IgG and fecal IgA against IpaB were induced after oral immunization. These responses, however, were lower than those obtained after intranasal immunization despite a 100-fold dosage increase. The level of protection induced by oral immunization with IpaB and IpaD was 40%, while intranasal immunization resulted in 90% protective efficacy. IpaB- and IpaD-specific IgA antibody-secreting cells in the lungs and spleen and T-cell-derived IL-2, IL-5, IL-17 and IL-10 were associated with protection. These results demonstrate the immunogenicity of orally administered IpaB and IpaD and support further studies in humans.

Engaging actively with issues in the responsible conduct of science: lessons from international efforts are relevant for undergraduate education in the United States

Numerous studies are demonstrating that engaging undergraduate students in original research can improve their achievement in the science, technology, engineering, and mathematics (STEM) fields and increase the likelihood that some of them will decide to pursue careers in these disciplines. Associated with this increased prominence of research in the undergraduate curriculum are greater expectations from funders, colleges, and universities that faculty mentors will help those students, along with their graduate students and postdoctoral fellows, develop an understanding and sense of personal and collective obligation for responsible conduct of science (RCS). This Feature describes an ongoing National Research Council (NRC) project and a recent report about educating faculty members in culturally diverse settings (Middle East/North Africa and Asia) to employ active-learning strategies to engage their students and colleagues deeply in issues related to RCS. The NRC report describes the first phase of this project, which took place in Aqaba and Amman, Jordan, in September 2012 and April 2013, respectively. Here we highlight the findings from that report and our subsequent experience with a similar interactive institute in Kuala Lumpur, Malaysia. Our work provides insights and perspectives for faculty members in the United States as they engage undergraduate and graduate students, as well as postdoctoral fellows, to help them better understand the intricacies of and connections among various components of RCS. Further, our experiences can provide insights for those who may wish to establish "train-the-trainer" programs at their home institutions.

Mesenchymal stem cells as a novel vaccine platform

Vaccines are the most efficient and cost-effective means of preventing infectious disease. However, traditional vaccine approaches have thus far failed to provide protection against human immunodeficiency virus (HIV), tuberculosis, malaria, and many other diseases. New approaches to vaccine development are needed to address some of these intractable problems. In this report, we review the literature identifying stimulatory effects of mesenchymal stem cells (MSC) on immune responses and explore the potential for MSC as a novel, universal vaccination platform. MSC are unique bone marrow-derived multipotent progenitor cells that are presently being exploited as gene therapy vectors for a variety of conditions, including cancer and autoimmune diseases. Although MSC are predominantly known for anti-inflammatory properties during allogeneic MSC transplant, there is evidence that MSC can actually promote adaptive immunity under certain settings. MSC have also demonstrated some success in anti-cancer therapeutic vaccines and anti-microbial prophylactic vaccines, as we report, for the first time, the ability of modified MSC to express and secrete a viral antigen that stimulates antigen-specific antibody production in vivo. We hypothesize that the unique properties of modified MSC may enable MSC to serve as an unconventional but innovative, vaccine platform. Such a platform would be capable of expressing hundreds of proteins, thereby generating a broad array of epitopes with correct post-translational processing, mimicking natural infection. By stimulating immunity to a combination of epitopes, it may be possible to develop prophylactic and even therapeutic vaccines to tackle major health problems including those of non-microbial and microbial origin, including cancer, or an infectious disease like HIV, where traditional vaccination approaches have failed.

Kinetic analysis and evaluation of the mechanisms involved in the resolution of experimental nontypeable Haemophilus influenzae-induced otitis media after transcutaneous immunization

Transcutaneous immunization (TCI) is a simple and needle-free method with which to induce protective immune responses. Using a chinchilla model of nontypeable Haemophilus influenzae (NTHI)-induced otitis media (OM), we examined the efficacy afforded by TCI with a novel chimeric immunogen called 'chimV4' which targets two critical adhesins expressed by NTHI, outer membrane protein P5 and the majority subunit of NTHI Type IV pilus, PilA. Experimental OM was first established in cohorts of animals, and then TCI performed via a therapeutic immunization regime by rubbing vaccine formulations on hydrated pinnae. The kinetics of resolution of established experimental disease was evaluated by clinically-relevant assessments of OM, bacterial culture of planktonic and adherent NTHI within the middle ear and gross examination of the relative amount of NTHI mucosal biofilms within the middle ear space. Within seven days after primary TCI, a significant reduction in the signs of OM, significantly fewer NTHI adherent to the middle ear mucosa and significant resolution of mucosal biofilms was detected in animals that received chimV4+ the adjuvant LT(R192G-L211A), compared to animals administered LT(R192G-L211A) alone or saline by TCI (p<0.05) with eradication of NTHI within an additional seven days. The mechanism for rapid disease resolution involved efflux of activated dermal dendritic cells from the pinnae after TCI, secretion of factors chemotactic for CD4(+) T-cells, induction of polyfunctional IFNγ- and IL-17-producing CD4(+) T-cells and secretion of host defense peptide within the middle ear. These data support TCI as a therapeutic intervention against experimental NTHI-induced OM and begin to elucidate the host response to immunization by this noninvasive regimen.

Bioencapsulation of the hepatitis B surface antigen and its use as an effective oral immunogen

Hepatitis B remains a major global health problem despite the availability of a safe and effective vaccine. Segments of the population lack access to or respond poorly to the parenteral vaccine, perpetuating the infection-transmission cycle. A low cost, orally delivered vaccine has the potential to alleviate many of these problems. Here we describe the expression of a bioencapsulated hepatitis B surface antigen (HBsAg) in maize and its immunogenicity, demonstrating for the first time a commercially feasible oral subunit vaccine production system for a major disease. This work surmounts previous barriers to plant-produced vaccines by expressing HBsAg at much higher levels and retaining antigen immunogenicity post-processing: factors which facilitated a robust immune response in mice without the need for an adjuvant. This method provides a practical solution to the delivery of a low-cost, stable oral vaccine.

Drug-disease interaction: Crohn's disease elevates verapamil plasma concentrations but reduces response to the drug proportional to disease activity

AIM

Inflammation is involved in the pathogenesis of cardiovascular diseases that includes reduced response to pharmacotherapy due to altered pharmacokinetics and pharmacodynamics. It is not known if these effects exist in general in all inflammatory conditions. It also remains unknown whether in a given population the effect is a function of disease severity. We investigated whether pharmacokinetics and pharmacodynamics of a typical calcium channel inhibitor are influenced by Crohn's disease (CD), a disease for which the disease severity can be readily ranked.

METHODS

We administered 80 mg verapamil orally to (i) healthy control subjects (n= 9), (ii) patients with clinically quiescent CD (n= 22) and (iii) patients with clinically active CD (n= 14). Serial analysis of verapamil enantiomers (total and plasma unbound), blood pressure and electrocardiograms were recorded over 8 h post dose. The severity of CD was measured using the Harvey-Bradshaw Index.

RESULTS

CD substantially and significantly increased plasma verapamil concentration and in a stereoselective fashion (S, 9-fold; R, 2-fold). The elevated verapamil concentration, however, failed to result in an increased verapamil pharmacodynamic effect so that the patients with elevated verapamil concentration demonstrated no significant increase in response measured as PR interval and blood pressure. Instead, the greater the disease severity, the lower was the drug potency to prolong PR interval (r= 0.86, P < 0.0006),

CONCLUSIONS

CD patients with severe disease may not respond to cardiovascular therapy with calcium channel blockers. Reducing the severity increases response despite reduced drug concentration. This observation may have therapeutic implication beyond the disease and the drug studies herein.

Transcutaneous immunization as preventative and therapeutic regimens to protect against experimental otitis media due to nontypeable Haemophilus influenzae

We have developed three nontypeable Haemophilus influenzae (NTHI) adhesin-derived immunogens that are significantly efficacious against experimental otitis media (OM) due to NTHI when delivered parenterally. We now expanded our preventative immunization strategies to include transcutaneous immunization (TCI) as a less invasive, but potentially equally efficacious, regimen to prevent OM due to NTHI. Additionally, we examined the potential of TCI as a therapeutic immunization regimen to resolve ongoing experimental OM. Preventative immunization with NTHI outer membrane protein (OMP) P5- and type IV pilus-targeted immunogens, delivered with the adjuvant LT(R192G-L211A), induced significantly earlier clearance of NTHI from the nasopharynges and middle ears of challenged chinchillas compared with receipt of immunogen or adjuvant alone. Moreover, therapeutic immunization resulted in significant resolution of established NTHI biofilms from the middle ear space of animals compared with controls. These data advocate TCI with the adhesin-directed immunogens as an efficacious regimen for prevention and resolution of experimental NTHI-induced OM.

Induction of increased permeability of polarized enterocyte monolayers by enterotoxigenic Escherichia coli heat-labile enterotoxin

Enterotoxigenic Escherichia coli (ETEC) is a common cause of acute diarrhea in resource-poor settings. We report that some ETEC strains elicit a reduction in trans-epithelial electrical resistance (TER) in polarized T84 epithelial cell monolayers. The effect was irreversible up to 48 hours after a three-hour infection and was observed with heat-labile enterotoxin (LT)-producing strains, but not with heat-stable enterotoxin (ST)-producing strains. Using purified LT, a mutant with reduced ADP-ribosylating activity, and the LT-B subunit alone, we demonstrate that TER reduction requires a functional enterotoxin. Treatment of monolayers with LT or LT-producing strains of ETEC increases paracellular permeability to fluorescein isothiocyanate-dextran. Our data suggest that LT-producing ETEC strains may induce intestinal barrier dysfunction.

Defending the mucosa: adjuvant and carrier formulations for mucosal immunity

A majority of infectious microorganisms either colonize or cross mucosal surfaces to enter the host. A major goal in vaccine design is to induce a protective, lasting immune response against potential pathogens at mucosal surfaces. In addition, mucosal vaccines can offer needle-free delivery, thereby improving accessibility, safety, and cost-effectiveness. Challenges to successful mucosal vaccination include poor induction of mucosal immunity, limited understanding of protective mechanisms and crosstalk between mucosal compartments, and the availability of safe, effective mucosal adjuvants and delivery systems. This review focuses on some key advances in the field of mucosal vaccinology within the past 2-3 years, including reports on promising new formulations and investigations into the mechanisms of established mucosal adjuvants and/or particulate carrier systems.

Unexpected modulation of recall B and T cell responses after immunization with rotavirus-like particles in the presence of LT-R192G

LT-R192G, a mutant of the thermolabile enterotoxin of E. coli, is a potent adjuvant of immunization. Immune responses are generally analyzed at the end of protocols including at least 2 administrations, but rarely after a prime. To investigate this point, we compared B and T cell responses in mice after one and two intrarectal immunizations with 2/6 rotavirus-like particles (2/6-VLP) and LT-R192G. After a boost, we found, an unexpected lower B cell expansion measured by flow cytometry, despite a secondary antibody response. We then analyzed CD4(+)CD25(+)Foxp3(+) regulatory T cells (Tregs) and CD4(+)CD25(+)Foxp3(-) helper T cells after in vitro (re)stimulation of mesenteric lymph node cells with the antigen (2/6-VLP), the adjuvant (LT-R192G) or both. 2/6-VLP did not activate CD4(+)CD25(+)Foxp3(-) nor Foxp3(+) T cells from non-immunized and 2/6-VLP immunized mice, whereas they did activate both subsets from mice immunized with 2/6-VLP in the presence of adjuvant. LT-R192G dramatically decreased CD4(+)CD25(+)Foxp3(+) T cells from non-immunized and 2/6-VLP immunized mice but not from mice immunized with 2/6-VLP and adjuvant. Moreover, in this case, LT-R192G increased Foxp3 expression on CD4(+)CD25(+)Foxp3(+) cells, suggesting specific Treg activation during the recall. Finally, when both 2/6-VLP and LT-R192G were used for restimulation, LT-R192G clearly suppressed both 2/6-VLP-specific CD4(+)CD25(+)Foxp3(-) and Foxp3(+) T cells. All together, these results suggest that LT-R192G exerts different effects on CD4(+)CD25(+)Foxp3(+) T cells, depending on a first or a second contact. The unexpected immunomodulation observed during the recall should be considered in designing vaccination protocols.

Hydration effects on skin microstructure as probed by high-resolution cryo-scanning electron microscopy and mechanistic implications to enhanced transcutaneous delivery of biomacromolecules

Although hydration is long known to improve the permeability of skin, penetration of macromolecules such as proteins is limited and the understanding of enhanced transport is based on empirical observations. This study uses high-resolution cryo-scanning electron microscopy to visualize microstructural changes in the stratum corneum (SC) and enable a mechanistic interpretation of biomacromolecule penetration through highly hydrated porcine skin. Swollen corneocytes, separation of lipid bilayers in the SC intercellular space to form cisternae, and networks of spherical particulates are observed in porcine skin tissue hydrated for a period of 4-10 h. This is explained through compaction of skin lipids when hydrated, a reversal in the conformational transition from unilamellar liposomes in lamellar granules to lamellae between keratinocytes when the SC skin barrier is initially established. Confocal microscopy studies show distinct enhancement in penetration of fluorescein isothiocyanate-bovine serum albumin (FITC-BSA) through skin hydrated for 4-10 h, and limited penetration of FITC-BSA once skin is restored to its natively hydrated structure when exposed to the environment for 2-3 h. These results demonstrate the effectiveness of a 4-10 h hydration period to enhance transcutaneous penetration of large biomacromolecules without permanently damaging the skin.

Norepinephrine Transporter is Involved in Down-Regulation of β1-Adrenergic Receptors Caused by Adjuvant Arthritis

Purpose. Inflammation in forms of rheumatoid and experimental arthritis cause not only joint pain but also excessive cardiovascular mortality. The condition also reduces response to calcium channel and β-adrenergic (β1-AR) antagonists. For calcium channel inhibitors, the reduced response is shown to be due to the reduced expression of target proteins. Hydroxymethylglutaryl CoA reductase inhibitors (statins) restore response to propranolol and verapamil. We tested the effect of adjuvant arthritis on the norepinephrine (NE) transporter (NET) density since altered sympathetic nervous system innervation has been observed in rheumatoid arthritis. Methods. Male Sprague–Dawley rats were divided into the following groups: Healthy/Placebo, Healthy/Statin, Pre-AA/Placebo, and Pre-AA/Statin (n=7-8/group). On Day 0, to the Pre-AA and Healthy groups, was injected Mycobacterium butyricum or saline, respectively. On Days 4-8, Statin and Placebo groups received either pravastatin (6 mg/kg) or placebo twice daily, respectively. On day 8, heart and blood samples were collected. The density of NET and 1-AR in heart homogenate; NE in plasma and heart and inflammatory mediators (nitrite and interferon-γ) in serum were determined. Results. Inflammation was associated with a significant reduction in both β1-AR and NET density with a positive correlation between the two proteins (r=0.978, p

Toward the development of a stable, freeze-dried formulation of Helicobacter pylori killed whole cell vaccine adjuvanted with a novel mutant of Escherichia coli heat-labile toxin

No vaccine exists for the prevention of infection with the ubiquitous gastric pathogen Helicobacter pylori, and drug therapy for the infection is complicated by poor patient compliance, the high cost of treatment, and ineffectiveness against drug-resistant strains. A new medical advancement is required to reduce the incidence of peptic ulcer disease and stomach cancer, two conditions caused by infection with H. pylori. Clinical trials have been performed with a formalin-inactivated H. pylori whole cell (HWC) vaccine, given orally in combination with the mucosal adjuvant mLT(R192G), a mutant of Escherichia coli heat-labile toxin. Following the initial dose of this vaccine, some subjects experienced gastrointestinal side effects. To reduce side effects and potentially further increase the amount of adjuvant that can safely be administered with the HWC vaccine, experiments were performed with a form of LT that carried two mutations in the A subunit, a substitution of G for R at position 192, and A for L at position 211. The double mutant LT (dmLT) adjuvant stimulated immune responses as effectively as the single mutant LT in mice. Additionally, following a challenge infection, the dmLT-adjuvanted vaccine was as effective as single mutant LT in reducing gastric urease levels (diagnostic for H. pylori infection), and H. pylori colonization in the stomach as assessed by quantitative analysis of stomach homogenates. A lyophilized formulation of HWC was developed to improve stability and to potentially reduce reliance on cold chain maintenance. It was observed that a dmLT-adjuvanted lyophilized vaccine was equally as protective in the mouse model as the liquid formulation as assessed by gastric urease analysis and analysis of stomach homogenates for viable H. pylori. No readily detectable effect of tonicity or moisture content was observed for the lyophilized vaccine within the formulation limits evaluated. In an accelerated stability study performed at 37 degrees C the lyophilized vaccine remained equally as protective as vaccine stored at 2-8 degrees C. The formulation selected for clinical development consisted of 2.5 x 10(10) formalin-inactivated cells per ml in 6.5% trehalose, 0.5% mannitol, and 10mM citrate buffer at pH 6.8.

Automated threshold detection for auditory brainstem responses: comparison with visual estimation in a stem cell transplantation study

BACKGROUND

Auditory brainstem responses (ABRs) are used to study auditory acuity in animal-based medical research. ABRs are evoked by acoustic stimuli, and consist of an electrical signal resulting from summated activity in the auditory nerve and brainstem nuclei. ABR analysis determines the sound intensity at which a neural response first appears (hearing threshold). Traditionally, threshold has been assessed by visual estimation of a series of ABRs evoked by different sound intensities. Here we develop an automated threshold detection method that eliminates the variability and subjectivity associated with visual estimation.

RESULTS

The automated method is a robust computational procedure that detects the sound level at which the peak amplitude of the evoked ABR signal first exceeds four times the standard deviation of the baseline noise. Implementation of the procedure was achieved by evoking ABRs in response to click and tone stimuli, under normal and experimental conditions (adult stem cell transplantation into cochlea). Automated detection revealed that the threshold shift from pre- to post-surgery hearing levels was similar in mice receiving stem cell transplantation or sham injection for click and tone stimuli. Visual estimation by independent observers corroborated these results but revealed variability in ABR threshold shifts and significance levels for stem cell-transplanted and sham-injected animals.

CONCLUSION

In summary, the automated detection method avoids the subjectivity of visual analysis and offers a rapid, easily accessible http://axograph.com/source/abr.html approach to measure hearing threshold levels in auditory brainstem response.

IFN-gamma is the only anti-rotavirus cytokine found after in vitro stimulation of memory CD4+ T cells from mice immunized with a chimeric VP6 protein

CD4+ T cells are the only lymphocytes required for protection of mice against rotavirus shedding after mucosal immunization with chimeric VP6 (MBP::VP6) and the adjuvant LT(R192G). One possible effector of protection is CD4+ T-cell cytokines. To determine if memory CD4+ T cells of immunized mice produce cytokines with direct anti-rotavirus activity, an in vitro infection model was developed using mouse CMT-93 cells and rhesus rotavirus (RRV). Spleen and lamina propria (LP) cells, as well as purified splenic CD4T cells obtained after intranasal immunization of BALB/c mice with MBP::VP6/LT(R192G) released large quantities of two cytokines (IL-17 and IFN-gamma) into cell supernatants when stimulated with MBP::VP6. Production of these same cytokines is rapidly upregulated in intestinal lymphocytes after rotavirus inoculation of immunized mice. IL-17 pretreatment of CMT-93 cells had no effect on subsequent RRV replication, but IFN-gamma was the most potent inhibitor within a panel of nine cytokines tested. Supernatants obtained after in vitro stimulation of splenic CD4+ T cells of immunized mice had high levels of anti-RRV activity and their pretreatment with mAb against IFN-gamma caused essentially complete loss of activity. Thus, IFN-gamma was the only cytokine identified in stimulated CD4+ T cells from immunized mice that directly inhibited rotavirus replication.

Effect of adjuvants and route of immunizations on the immune response to recombinant plague antigens

In this study, we compare four different adjuvants, LT(R192G), CpG ODN, MPL((R))TDM, and alum, for their ability to affect the magnitude, distribution, and duration of antibody responses against F1-V, the lead-candidate antigen for the next generation vaccine against plague, in a murine model. In addition, three different routes of immunization-intranasal (IN), transcutaneous (TC), and subcutaneous (SC) were compared with each adjuvant. Since aerosol exposure to biological warfare agents is of primary concern, both serum and bronchioalveolar lavage (BAL) were analyzed for antigen-specific antibody responses. The most significant findings of the study reported here are that (1) the adjuvant influences the Type 1/Type 2 balance of the antibody response in both the serum and BAL, (2) mucosal immunization is not necessary to obtain F1-V-specific BAL responses, (3) non-traditional adjuvants such as LT(R192G) work when delivered subcutaneously, (4) the route of immunization affects the magnitude of the immune response, and (5) F1-V is highly immunogenic by some routes even in the absence of an exogenously applied adjuvant. These studies provide important insights into the influence of different classes of adjuvants on the immune outcome in biodefense vaccines and for development of new-generation vaccines against other pathogens as well.

Identification of an immunodominant CD4+ T cell epitope in the VP6 protein of rotavirus following intranasal immunization of BALB/c mice

The only lymphocytes required for protection against fecal rotavirus shedding after intranasal immunization of BALB/c (H-2(d)) mice with a chimeric rotavirus VP6 protein (MBPColon, two colonsVP6) and the mucosal adjuvant LT(R192G) are CD4(+) T cells. The purpose of this study was to identify CD4(+) T cell epitopes within VP6 that might be responsible for this protection. To make this determination, spleen cells obtained from BALB/c mice following intranasal immunization with MBPColon, two colonsVP6/LT(R192G) were stimulated in vitro with either MBPColon, two colonsVP6 or overlapping VP6 peptides containing <or=30 amino acids (AA). The numbers of memory (CD44(high)) CD4(+) T cells stimulated to produce T(H)1 and T(H)17 cytokines (IFNgamma and IL-17), as well as the quantities of these cytokines released into the cell supernatants, were then measured relative to those produced in mock-stimulated cells from the same animals. One epitope expected to be found was the VP6 14-mer AA(289-302), previously identified as a CD4(+) T cell epitope in H-2(d) mice. This was not observed but instead the only VP6 epitope identified was AA(242-259), the dominant CD4(+) T cell epitope previously reported after oral, live rotavirus immunization.

Intrarectal immunization of mice with VP6 and either LT(R192G) or CTA1-DD as adjuvant protects against fecal rotavirus shedding after EDIM challenge

Intranasal or oral delivery of the chimeric rotavirus VP6 protein MBP::VP6 to mice elicited >90% reductions in fecal rotavirus shedding after murine rotavirus challenge. Protection depended on co-administration of adjuvants, the most effective being bacterial toxins. Because of safety and efficacy concerns following intranasal or oral toxin delivery, protective efficacy of MBP::VP6 after intrarectal delivery with toxin adjuvants was determined and compared to that induced after intranasal and oral immunization. Adult BALB/c mice were orally challenged with the murine rotavirus strain EDIM 4 weeks after their second immunization with MBP::VP6 and either LT(R192G), an attenuated Escherichia coli heat-labile toxin, or CTA1-DD, a cholera toxin derivative. Reductions in fecal rotavirus shedding were then determined relative to mock-immunized mice. Immunization with MBP::VP6 and either adjuvant by any route (except oral immunization with CTA1-DD) significantly (P<0.0001) reduced rotavirus shedding. As was previously found after oral and intranasal immunization, intrarectal immunization with MBP::VP6 and adjuvant was associated with T cell responses (IFNgamma and IL-17) but not B cell (antibody) responses.

Evaluation of combinatorial vaccines against anthrax and plague in a murine model

In this study, we examine the potential of a combinatorial vaccine consisting of the lead-candidate antigens for the next generations of vaccines against anthrax (rPA) and plague (F1-V) with the specific objective of determining synergy or interference between the vaccine components when they are administered separately or together by both traditional parenteral immunization (SC) and mucosal immunization (IN) in the presence of appropriate adjuvants. The most significant findings of the study reported here are that (1) a combinatorial vaccine consisting of equal amounts of F1-V and rPA administered SC is effective at eliciting a robust serum and bronchoalveolar lavage (BAL) antigen-specific IgG and IgG1 response against both antigens in immunized animals, and when administered IN, a robust antigen-specific IgG2a response in the serum and BAL is also induced; (2) there were few instances where either synergy or interference was observed in the combined vaccine administered by either route and those differences occurred soon after the final immunization and were not sustained over time; (3) IN immunization was as effective as SC immunization for induction of antigen-specific serum and BAL antibody responses using the same amount of antigen; (4) the IgG1/IgG2a ratios suggest a strongly biased Type 2 response following SC immunization, while IN immunization produced a more balanced Type 1/Type 2 response; (5) the IgG1/IgG2a ratio was influenced by the route of immunization, the adjuvant employed, and the nature of the antigen. As with previously published studies, there were still detectable levels of circulating anti-F1-V and anti-rPA even 6 months post-primary immunization. These studies provide important insights into the development of new generation biodefense vaccines.

Association of gamma interferon and interleukin-17 production in intestinal CD4+ T cells with protection against rotavirus shedding in mice intranasally immunized with VP6 and the adjuvant LT(R192G)

Mucosal immunization of mice with chimeric, Escherichia coli-expressed VP6, the protein that comprises the intermediate capsid layer of the rotavirus particle, together with attenuated E. coli heat-labile toxin LT(R192G) as an adjuvant, reduces fecal shedding of rotavirus antigen by >95% after murine rotavirus challenge, and the only lymphocytes required for protection are CD4+ T cells. Because these cells produce cytokines with antiviral properties, the cytokines whose expression is upregulated in intestinal memory CD4+ T cells immediately after rotavirus challenge of VP6/LT(R192G)-immunized mice may be directly or indirectly responsible for the rapid suppression of rotavirus shedding. This study was designed to identify which cytokines are significantly upregulated in intestinal effector sites and secondary lymphoid tissues of intranasally immunized BALB/c mice after challenge with murine rotavirus strain EDIM. Initially, this was done by using microarray analysis to quantify mRNAs for 96 murine common cytokines. With this procedure, the synthesis of mRNAs for gamma interferon (IFN-gamma) and interleukin-17 (IL-17) was found to be temporarily upregulated in intestinal lymphoid cells of VP6/LT(R192G)-immunized mice at 12 h after rotavirus challenge. These cytokines were also produced in CD4+ T cells obtained from intestinal sites specific to VP6/LT(R192G)-immunized mice after in vitro exposure to VP6 as determined by intracellular cytokine staining and secretion of cytokines. Although genetically modified mice that lack receptors for either IFN-gamma or IL-17 remained protected after immunization, these results provide suggestive evidence that these cytokines may play direct or indirect roles in protection against rotavirus after mucosal immunization of mice with VP6/LT(R192G).

Protection of mice against rotavirus challenge following intradermal DNA immunization by Biojector needle-free injection

Mucosal administration (intranasal or oral) of a VP6 rotavirus vaccine to mice consistently elicits high levels of protection after rotavirus challenge (93->99% reductions in fecal rotavirus shedding) but only when co-administered with an effective adjuvant such as LT(R192G). Here, we showed that Biojector needle-free injection of VP6-encoded plasmids also induced protection (85-93%) when they were co-administrated with LT(R192G)-encoded plasmids. A reduction in the amount of VP6 plasmid from 50 to 10 microg reduced protection from 93 to 70%, but the immunized mice remained significantly (P<0.05) protected. Intramuscular needle injection of VP6/LT(R192G)-plasmids also induced significant protection (66%).

Single epitope mucosal vaccine delivered via immuno-stimulating complexes induces low level of immunity against simian-HIV

The difficulty in developing an effective vaccine to contain the HIV/AIDS epidemic coupled with the fact that primary HIV-1 infection typically occurs via mucosal sites has increased emphasis on vaccine approaches that protect at mucosal surfaces. In this study we employed HIV and simian-HIV (SHIV)-derived T helper (Th) and cytotoxic T lymphocyte (CTL) single epitopes incorporated into immuno-stimulating complexes (ISCOM) as a candidate immunogens. Immunized rhesus macaques (Macaca mulatta) were challenged with CCR5-tropic SHIV(SF162p4). On the day of challenge, low levels of virus-neutralizing antibodies (Ab) and CTLs were detected in ISCOM-immunized macaques. Greater than 10(5) viral RNA copies per ml of plasma in 2/5 immunized and 3/4 control macaques were detected within 3 weeks post-challenge. Depletion of CD4+ T cells from gut-associated lymphoid tissues (GALT) was observed by post-challenge day (PCD) 14 in all macaques regardless immunization. Nonetheless, lower viral loads and relatively better preservation of peripheral CD4+ T cells following the SHIV infection was observed in ISCOM-immunized macaques. We predict that if coadministered with additional epitopes and/or more efficacious mucosal delivery system or route, HIV/SIV-derived peptide vaccines may have potential to elicit heterologous protection.

Mice develop effective but delayed protective immune responses when immunized as neonates either intranasally with nonliving VP6/LT(R192G) or orally with live rhesus rotavirus vaccine candidates

Rotavirus vaccines are delivered early in life, when the immune system is immature. To determine the effects of immaturity on responses to candidate vaccines, neonatal (7 days old) and adult mice were immunized with single doses of either Escherichia coli-expressed rotavirus VP6 protein and the adjuvant LT(R192G) or live rhesus rotavirus (RRV), and protection against fecal rotavirus shedding following challenge with the murine rotavirus strain EDIM was determined. Neonatal mice immunized intranasally with VP6/LT(R192G) were unprotected at 10 days postimmunization (dpi) and had no detectable rotavirus B-cell (antibody) or CD4(+) CD8(+) T-cell (rotavirus-inducible, Th1 [gamma interferon and interleukin-2 {IL-2}]-, Th2 [IL-5 and IL-4]-, or ThIL-17 [IL-17]-producing spleen cells) responses. However, by 28 and 42 dpi, these mice were significantly (P >or= 0.003) protected and contained memory rotavirus-specific T cells but produced no rotavirus antibody. In contrast, adult mice were nearly fully protected by 10 dpi and contained both rotavirus immunoglobulin G and memory T cells. Neonates immunized orally with RRV were also less protected (P=0.01) than adult mice by 10 dpi and produced correspondingly less rotavirus antibody. Both groups contained few rotavirus-specific memory T cells. Protection levels by 28 dpi for neonates or adults were equal, as were rotavirus antibody levels. This report introduces a neonatal mouse model for active protection studies with rotavirus vaccines. It indicates that, with time, neonatal mice develop full protection after intranasal immunization with VP6/LT(R192G) or oral immunization with a live heterologous rotavirus and supports reports that protection depends on CD4(+) T cells or antibody, respectively.

Impact of vaccine-induced mucosal high-avidity CD8+ CTLs in delay of AIDS viral dissemination from mucosa

Natural HIV transmission occurs through mucosa, but it is debated whether mucosal cytotoxic T lymphocytes (CTLs) can prevent or reduce dissemination from the initial mucosal site to the systemic circulation. Also, the role of CTL avidity in mucosal AIDS viral transmission is unknown. To address these questions, we used delay in acute-phase peak viremia after intrarectal challenge as an indicator of systemic dissemination. We found that a peptide-prime/poxviral boost vaccine inducing high levels of high-avidity mucosal CTLs can have an impact on dissemination of intrarectally administered pathogenic SHIV-ku2 in macaques and that such protection correlates better with mucosal than with systemic CTLs and particularly with levels of high-avidity mucosal CTLs.

Protection against rotavirus shedding after intranasal immunization of mice with a chimeric VP6 protein does not require intestinal IgA

Intranasal immunization of mice with chimeric VP6 and the adjuvant LT(R192G) consistently elicits >95% reductions in fecal rotavirus shedding following challenge. To determine the association between mucosal antibody and protection, we immunized BALB/c wt and J chain knockout (Jch-/-) mice with VP6 and either LT(R192G) or cholera toxin (CT). Both strains developed nearly equal levels of serum rotavirus IgG, but Jch-/- mice, which cannot transport dimeric IgA across epithelial cell surfaces, developed >4-fold higher levels of serum rotavirus IgA. Stool rotavirus IgA was present in wt but undetectable in Jch-/- mice. When challenged with rotavirus strain EDIM, reductions in rotavirus shedding were nearly identical in VP6-immunized wt and Jch-/- mice (i.e., 97% and 92%, respectively; P > 0.01). Th1 CD4 T cell responses were also detected in VP6-immunized animals based on high levels of IFN-gamma and IL-2 found after in vitro VP6 stimulation of spleen cells. Therefore, protection induced by intranasal immunization of mice with VP6 and adjuvant does not depend on intestinal rotavirus IgA antibody but appears to be associated with CD4 T cells.

Induction of serum and mucosal FIV-specific immune responses by intranasal immunization with p24Gag

We examined the ability of FIV p24Gag to induce systemic and mucosal FIV-specific immune responses when delivered as a nasal immunogen alone, or with a mucosal adjuvant, Escherichia coli heat labile toxin LT(R192G). Nasal immunization with p24Gag alone induced FIV-specific immune responses but overall responses were weak, transient, and/or present only in a few animals. Co-administration of LT(R192G) resulted in strong FIV-specific serum IgG and enhanced salivary IgA responses. Moreover, FIV-specific IgA was detected in vaginal wash fluid from 6/6 cats co-immunized with LT(R192G) and p24Gag versus 1/6 immunized with p24Gag alone. This is the first report detailing induction of systemic or mucosal FIV-specific immune responses by nasal immunization alone. As such, this study demonstrates that nasal immunization of cats can be a relevant and effective route for the delivery of candidate vaccines. However, while nasal immunization of cats with p24Gag induces antigen-specific systemic immune responses, development of strong systemic and mucosal immune responses requires co-administration of a mucosal adjuvant, such as LT(R192G).

Effectiveness of the B subunit of cholera toxin in potentiating immune responses to the recombinant hemagglutinin/adhesin domain of the gingipain Kgp from Porphyromonas gingivalis

The hemagglutinin/adhesin HArep domain is present in the gingipains HRgpA and Kgp and in the hemagglutinin HagA of Porphyromonas gingivalis and is felt to be important in the virulence of this bacterium. In the present study, we determined the immunogenicity of recombinant HArep from the gingipain Kgp (termed Kgp-rHArep) and the effectiveness of the B subunit of cholera toxin (CTB), compared to other adjuvants in potentiating a specific response to Kgp-rHArep following intranasal (i.n.) immunization of mice. Furthermore, we determined the effectiveness of anti-Kgp-rHArep antibodies in protection against P. gingivalis invasion of epithelial cells. Evidence is provided that Kgp-rHArep was effective in inducing immune responses following systemic or mucosal immunization. Kgp-rHArep induced both a Th1- and Th2-type response following i.n. immunization. Immunization of mice with Kgp-rHArep and CTB, either admixed or chemically conjugated to the antigen, via the i.n. route, resulted in a significant augmentation of the systemic and mucosal immune response to Kgp-rHArep, which was similar to or higher than the responses seen in mice immunized with antigen and the other adjuvants tested. CTB and the heat-labile toxin of Escherichia coli potentiated a Th1- and Th2-type response to Kgp-rHArep, whereas the adjuvant monophosphoryl lipid A preferentially promoted a Th1-type response to the antigen. Furthermore, anti-Kgp-rHArep antibodies were shown to protect against P. gingivalis invasion of epithelial cells in an in vitro system. These results demonstrate the effectiveness of certain mucosal adjuvants in potentiating and in altering the nature of the immune response to Kgp-rHArep following i.n. immunization, and provide evidence for the potential usefulness of Kgp-rHArep for the development of a vaccine against periodontal disease.

Dynamics of forward and reverse transport by the glial glycine transporter, glyt1b

Glycine is a coagonist at the N-methyl-D-aspartate receptor. Changes in extracellular glycine concentration may modulate N-methyl-D-aspartate receptor function and excitatory synaptic transmission. The GLYT1 glycine transporter is present in glia surrounding excitatory synapses, and plays a key role in regulating extracellular glycine concentration. We investigated the kinetic and other biophysical properties of GLYT1b, stably expressed in CHO cells, using whole-cell patch-clamp techniques. Application of glycine produced an inward current, which decayed within a few seconds to a steady-state level. When glycine was removed, a transient outward current was observed, consistent with reverse transport of accumulated glycine. The outward current was enhanced by elevating intracellular or lowering extracellular [Na(+)], and was modulated by changes in extracellular [glycine] and time of glycine application. We developed a model of GLYT1b function, which accurately describes the time course of the transporter current under a range of experimental conditions. The model predicts that glial uptake of glycine will decay toward zero during a sustained period of elevated glycine concentration. This property of GLYT1b may permit spillover from glycinergic terminals to nearby excitatory terminals during a prolonged burst of inhibitory activity, and reverse transport may extend the period of elevated glycine concentration beyond the end of the inhibitory burst.

Protection against aerosolized Yersinia pestis challenge following homologous and heterologous prime-boost with recombinant plague antigens

A Yersinia pestis-derived fusion protein (F1-V) has shown great promise as a protective antigen against aerosol challenge with Y. pestis in murine studies. In the current study, we examined different prime-boost regimens with F1-V and demonstrate that (i) boosting by a route other than the route used for the priming dose (heterologous boosting) protects mice as well as homologous boosting against aerosol challenge with Y. pestis, (ii) parenteral immunization is not required to protect mice against aerosolized plague challenge, (iii) the route of immunization and choice of adjuvant influence the magnitude of the antibody response as well as the immunoglobulin G1 (IgG1)/IgG2a ratio, and (iv) inclusion of an appropriate adjuvant is critical for nonparenteral immunization.

Mucosal adjuvants

Induction of immune responses following oral immunization is frequently dependent upon the co-administration of appropriate adjuvants that can initiate and support the transition from innate to adaptive immunity. The three bacterial products with the greatest potential to function as mucosal adjuvants are the ADP-ribosylating enterotoxins (cholera toxin and the heat-labile enterotoxin of Escherichia coli), synthetic oligodeoxynucleotides containing unmethylated CpG dinucleotides (CpG ODN), and monophosphoryl lipid A (MPL). The mechanism of adjuvanticity of the ADP-ribosylating enterotoxins is the subject of considerable debate. Our own view is that adjuvanticity is an outcome and not an event. It is likely that these molecules exert their adjuvant function by interacting with a variety of cell types, including epithelial cells, dendritic cells, macrophages, and possibly B- and T-lymphocytes. The adjuvant activities of CpG and MPL are due to several different effects they have on innate and adaptive immune responses and both MPL and CpG act through MyD88-dependent and -independent pathways. This presentation will summarize the probable mechanisms of action of these diverse mucosal adjuvants and discuss potential synergy between these molecules for use in conjunction with plant-derived vaccines.

The 'permeome' of the malaria parasite: an overview of the membrane transport proteins of Plasmodium falciparum

Bioinformatic and expression analyses attribute putative functions to transporters and channels encoded by the Plasmodium falciparum genome. The malaria parasite has substantially more membrane transport proteins than previously thought.

Background

The uptake of nutrients, expulsion of metabolic wastes and maintenance of ion homeostasis by the intraerythrocytic malaria parasite is mediated by membrane transport proteins. Proteins of this type are also implicated in the phenomenon of antimalarial drug resistance. However, the initial annotation of the genome of the human malaria parasite Plasmodium falciparum identified only a limited number of transporters, and no channels. In this study we have used a combination of bioinformatic approaches to identify and attribute putative functions to transporters and channels encoded by the malaria parasite, as well as comparing expression patterns for a subset of these.

Results

A computer program that searches a genome database on the basis of the hydropathy plots of the corresponding proteins was used to identify more than 100 transport proteins encoded by P. falciparum. These include all the transporters previously annotated as such, as well as a similar number of candidate transport proteins that had escaped detection. Detailed sequence analysis enabled the assignment of putative substrate specificities and/or transport mechanisms to all those putative transport proteins previously without. The newly-identified transport proteins include candidate transporters for a range of organic and inorganic nutrients (including sugars, amino acids, nucleosides and vitamins), and several putative ion channels. The stage-dependent expression of RNAs for 34 candidate transport proteins of particular interest are compared.

Conclusion

The malaria parasite possesses substantially more membrane transport proteins than was originally thought, and the analyses presented here provide a range of novel insights into the physiology of this important human pathogen.

Effect of homologous and heterologous prime–boost on the immune response to recombinant plague antigens

Among the pathogens that have been identified as potential agents of biological warfare or bioterrorism, Yersinia pestis is one of the main concerns due to the severity and potential transmissibility of the pneumonic form of the disease in humans. There are no approved vaccines for protection against pneumonic plague, but a Y. pestis-derived fusion protein (F1-V) has shown great promise as a protective antigen in murine studies. In the current study, we examine different prime-boost regimens, including parenteral, mucosal, and transcutaneous delivery, in order to explore the effect of changing the route of prime and boost on the ability of recombinant F1-V to promote the development of long-lasting, high-titer antibodies. The most significant findings of the study reported here are that (1) intranasal and subcutaneous immunizations are both effective and essentially equivalent for induction of serum and bronchioalveolar anti-F1-V IgG1 responses when a single booster dose is administered by the same (homologous) route, (2) heterologous boosting can be as or more effective than homologous boosting for induction of either serum or bronchioalveolar anti-F1-V IgG1 responses, and (3) anti-F1 and anti-V total IgG responses were highest in animals primed intranasally and boosted by any route when compared to animals primed transcutaneously or subcutaneously. As with previously published studies, there were still significant levels of circulating anti-F1-V antibodies 1 year post-primary immunization. These studies provide important insights into the development of new-generation biodefense vaccines.

Intranasal administration of an Escherichia coli-expressed codon-optimized rotavirus VP6 protein induces protection in mice

We are developing rotavirus vaccines based on the VP6 protein of the human G1P[8] [corrected] [J. Virol. 73 (1999) 7574] CJN strain of rotavirus. One prototype candidate consisting of MBP::VP6::His6, a chimeric protein of maltose-binding protein, VP6 and hexahistidine, was expressed mainly as truncated polypeptides in Escherichia coli BL21(DE3) cells. A possible reason for this extensive truncation is the high frequencies of rare bacterial codons within the rotavirus VP6 gene. Expression of truncated recombinant VP6 was found to be reduced, and expression of complete VP6 protein was simultaneously increased, when the protein was expressed in Rosetta(DE3)pLacI E. coli cells that contain increased amounts of transfer RNAs for a selection of rare codons. The same observation was made when a synthetic codon-optimized CJN-VP6 gene was expressed in E. coli BL21 or Rosetta cells. To increase protein recovery, recombinant E. coli cells were treated with 8M urea. Denatured, full-length MBP::VP6::His6 protein was then purified and used for intranasal vaccination of BALB/c mice (2 doses administered with E. coli heat-labile toxin LT(R192G) as adjuvant). Following oral challenge with the G3P[16] [corrected] [J. Virol. 76 (2002) 560] EDIM strain of murine rotavirus, protection levels against fecal rotavirus shedding were comparable (P>0.05) between groups of mice immunized with denatured codon-optimized or native (not codon-optimized) immunogen with values ranging from 87 to 99%. These protection levels were also comparable to those found after immunization with non-denatured CJN VP6. Thus, expression of complete rotavirus VP6 protein was greatly enhanced by codon optimization, and the protection elicited was not affected by denaturation of recombinant VP6.

Adenosine triphosphate acts as both a competitive antagonist and a positive allosteric modulator at recombinant N-methyl-D-aspartate receptors

ATP and glutamate are fast excitatory neurotransmitters in the central nervous system acting primarily on ionotropic P2X and glutamate [N-methyl-D-aspartate (NMDA) and non-NMDA] receptors, respectively. Both neurotransmitters regulate synaptic plasticity and long-term potentiation in hippocampal neurons. NMDA receptors are responsible primarily for the modulatory action of glutamate, but the mechanism underlying the modulatory effect of ATP remains uncertain. In the present study, the effect of ATP on recombinant NR1a + 2A, NR1a + 2B, and NR1a + 2C NMDA receptors expressed in Xenopus laevis oocytes was investigated. ATP inhibited NR1a + 2A and NR1a + 2B receptor currents evoked by low concentrations of glutamate but potentiated currents evoked by saturating glutamate concentrations. In contrast, ATP potentiated NR1a + 2C receptor currents evoked by nonsaturating glutamate concentrations. ATP shifted the glutamate concentration-response curve to the right, indicating a competitive interaction at the agonist binding site. ATP inhibition and potentiation of glutamate-evoked currents was voltage-independent, indicating that ATP acts outside the membrane electric field. Other nucleotides, including ADP, GTP, CTP, and UTP, inhibited glutamate-evoked currents with different potencies, revealing that the inhibition is dependent on both the phosphate chain and nucleotide ring structure. At high concentrations, glutamate outcompetes ATP at the agonist binding site, revealing a potentiation of the current. This effect must be caused by ATP binding at a separate site, where it acts as a positive allosteric modulator of channel gating. A simple model of the NMDA receptor, with ATP acting both as a competitive antagonist at the glutamate binding site and as a positive allosteric modulator at a separate site, reproduced the main features of the data.