Pre-Clinical Evaluation of a Novel Nanoemulsion-Based Hepatitis B Mucosal Vaccine

Hepatitis B virus infection remains an important global health concern despite the availability of safe and effective prophylactic vaccines. Limitations to these vaccines include requirement for refrigeration and three immunizations thereby restricting use in the developing world. A new nasal hepatitis B vaccine composed of recombinant hepatitis B surface antigen (HBsAg) in a novel nanoemulsion (NE) adjuvant (HBsAg-NE) could be effective with fewer administrations.Physical characterization indicated that HBsAg-NE consists of uniform lipid droplets (349+/-17 nm) associated with HBsAg through electrostatic and hydrophobic interactions. Immunogenicity of HBsAg-NE vaccine was evaluated in mice, rats and guinea pigs. Animals immunized intranasally developed robust and sustained systemic IgG, mucosal IgA and strong antigen-specific cellular immune responses. Serum IgG reached > or = 10(6) titers and was comparable to intramuscular vaccination with alum-adjuvanted vaccine (HBsAg-Alu). Normalization showed that HBsAg-NE vaccination correlates with a protective immunity equivalent or greater than 1000 IU/ml. Th1 polarized immune response was indicated by IFN-gamma and TNF-alpha cytokine production and elevated levels of IgG(2) subclass of HBsAg-specific antibodies. The vaccine retains full immunogenicity for a year at 4 degrees C, 6 months at 25 degrees C and 6 weeks at 40 degrees C. Comprehensive pre-clinical toxicology evaluation demonstrated that HBsAg-NE vaccine is safe and well tolerated in multiple animal models.Our results suggest that needle-free nasal immunization with HBsAg-NE could be a safe and effective hepatitis B vaccine, or provide an alternative booster administration for the parenteral hepatitis B vaccines. This vaccine induces a Th1 associated cellular immunity and also may provide therapeutic benefit to patients with chronic hepatitis B infection who lack cellular immune responses to adequately control viral replication. Long-term stability of this vaccine formulation at elevated temperatures suggests a direct advantage in the field, since potential excursions from cold chain maintenance could be tolerated without a loss in therapeutic efficacy

Does Host Complement Kill Borrelia burgdorferi within Ticks?

The Lyme disease spirochete, Borrelia burgdorferi, inhabits the gut lumen of the tick vector. At this location the spirochete is exposed to host blood when a tick feeds. We report here on studies that were done with normal and complement-deficient (C3-knockout) mice to determine if the host complement system killed spirochetes within the vector. We found that spirochete numbers within feeding nymphs were not influenced by complement, most likely because host complement was inactivated within the vector. The Lyme disease outer surface protein A (OspA) vaccine is a transmission-blocking vaccine that targets spirochetes in the vector. In experiments with mice hyperimmunized with OspA, complement was not required to kill spirochetes within nymphs and to block transmission from nymphs to the vaccinated host. However, host complement did enhance the ability of OspA antibody to block larvae from acquiring spirochetes. Thus, the effects of OspA antibody on nymphal transmission and larval acquisition appear to be based on different mechanisms

In Vitro Activities of a Novel Nanoemulsion against Burkholderia and Other Multidrug-Resistant Cystic Fibrosis-Associated Bacterial Species▿

Respiratory tract infection, most often involving opportunistic bacterial species with broad-spectrum antibiotic resistance, is the primary cause of death in persons with cystic fibrosis (CF). Species within the Burkholderia cepacia complex are especially problematic in this patient population. We investigated a novel surfactant-stabilized oil-in-water nanoemulsion (NB-401) for activity against 150 bacterial isolates recovered primarily from CF respiratory tract specimens. These specimens included 75 Burkholderia isolates and 75 isolates belonging to other CF-relevant species including Pseudomonas, Achromobacter, Pandoraea, Ralstonia, Stenotrophomonas, and Acinetobacter. Nearly one-third of the isolates were multidrug resistant, and 20 (13%) were panresistant based on standard antibiotic testing. All isolates belonging to the same species were genotyped to ensure that each isolate was a distinct strain. The MIC90 of NB-401 was 125 μg/ml. We found no decrease in activity against multidrug-resistant or panresistant strains. MBC testing showed no evidence of tolerance to NB-401. We investigated the activity of NB-401 against a subset of strains grown as a biofilm and against planktonic strains in the presence of CF sputum. Although the activity of NB-401 was decreased under both conditions, the nanoemulsion remained bactericidal for all strains tested. These results support NB-401's potential role as a novel antimicrobial agent for the treatment of infection due to CF-related opportunistic pathogens

In vivo analyses of HBsAg-NE stability.

<p>HBsAg specific antibody responses to freshly prepared HBsAg-NE or HBsAg-NE stored under real-time (4°C), accelerated (25°C) and stressed (40°C) temperature conditions are depicted. CD-1 mice were vaccinated with either freshly prepared or stored HBsAg-NE and boosted at 6 weeks. Serum anti-HBsAg IgG antibody concentrations are presented as a mean of endpoint titers in individual sera +/− SD. Comparison of serum IgG elicited by freshly prepared HBsAg-NE to formulation stored for (A) 6 weeks, (B) 3 months, (C) 6 months or (D) 1 year at indicated temperatures. * indicates a statistical difference (<i>p value<0.05</i>) in the anti-HBsAg IgG titers between freshly mixed and stored formulation. Arrows indicate vaccine administration.</p

Histopathological analysis of nasal tissue exposed to NE adjuvant or HBsAg-NE.

<p>Mice: CD-1 mice were vaccinated with HBsAg-NE and primed at 2 weeks. (A–B) Photomicrographs of H&E stained nasal epithelium collected from mice 14 days following the boost vaccination. Only normal tissue architecture was recorded which indicates a lack of (sub) chronic cytotoxicity or inflammation. (C) Nasal epithelium collected 24 hours following boost vaccination with HBsAg-NE scored as a +1 grade change according to methodology as described is shown as an example of architectural change. The arrow indicates a single microscopic focus of accumulation of mucoid material and debris in the nasal passages. However, no evidence of epithelial necrosis or inflammatory infiltration of the nasal epithelium is detected. (D) Nasal epithelium collected 24 hours following boost vaccination with HBsAg-NE scored as a +2 grade. The arrow indicates a single microscopic focus of accumulation of mucoid material and debris in the nasal passages in the absence of inflammatory changes. Architectural change demonstrated in C and D are considered incidental and can be observed in non-vaccinated mice. Rats and guinea pigs: Nasal epithelium was collected 14 days following final boost vaccination from rats (E–F) and guinea pigs (G–H) treated a total of 3 doses of HBsAg-NE administered 14 days apart. Normal tissue architecture is observed suggesting lack of toxicity or inflammation. Dogs: Nasal biopsies were collected 24 hours following the final dose in dogs treated with a total of three doses of NE adjuvant. NE was delivered using a Pfeiffer multidose wide angle sprayer pump in 200 μl/dose (I) or 400 μl/dose (J). No evidence of inflammation or cytotoxicity was detected.</p

Pre-clinical toxicology evaluation.

a<p>- The number of animals used for analysis: CD-1 (n = 10), BALB/c, Wistar rats and Hartley guinea pigs (n = 5) and Beagles (n = 1) per group.</p>b<p>- Histological lesions were evaluated on a scale from 0 to 10 with +1 single microscopic focus, +2 at least 2 microscopic foci, +3 more than 3 foci or multiple locally extensive areas of pathology, +4 to +6 were associated increasing severity and more extensive distribution (these lesions could be associated with morbidity), +7 and above had increasing degrees of inflammation (+10 associated with mortality).</p>c<p>- Other tissues evaluated include heart, liver, kidneys, spleen, esophagus, trachea, stomach, intestines, pancreas, and adrenals.</p>d<p>- Metabolic analysis evaluated by standard biochemical serum profile analysis on a IDEXX Vet Test Analyzer™ and performed at the Animal Diagnostic Laboratory through the Unit for Laboratory Animal Medicine at the University of Michigan. Normal indicates all analytes fell within normal expected distributions per species.</p>e<p>- Administered every 2 weeks.</p>f<p>- Administered every 15 minutes.</p>g<p>- Administered every 4 hours.</p>h<p>- Administered every 4 weeks.</p