Dendrimer-RNA nanoparticles generate protective immunity against lethal Ebola, H1N1 influenza, and Toxoplasma gondii challenges with a single dose.

Vaccines have had broad medical impact, but existing vaccine technologies and production methods are limited in their ability to respond rapidly to evolving and emerging pathogens, or sudden outbreaks. Here, we develop a rapid-response, fully synthetic, single-dose, adjuvant-free dendrimer nanoparticle vaccine platform wherein antigens are encoded by encapsulated mRNA replicons. To our knowledge, this system is the first capable of generating protective immunity against a broad spectrum of lethal pathogen challenges, including H1N1 influenza, Toxoplasma gondii, and Ebola virus. The vaccine can be formed with multiple antigen-expressing replicons, and is capable of eliciting both CD8(+) T-cell and antibody responses. The ability to generate viable, contaminant-free vaccines within days, to single or multiple antigens, may have broad utility for a range of diseases.

Identification of TgCBAP, a novel cytoskeletal protein that localizes to three distinct subcompartments of the Toxoplasma gondii pellicle.

The cytoskeletons of Toxoplasma gondii and related apicomplexan parasites are highly polarized, with apical and basal regions comprised of distinct protein complexes. Components of these complexes are known to play important roles in parasite shape, cell division, and host cell invasion. During an effort to discover the biologically relevant target of a small-molecule inhibitor of T. gondii invasion (Conoidin A), we discovered a novel cytoskeletal protein that we named TgCBAP (Conserved Basal Apical Peripheral protein). Orthologs of TgCBAP are only found in the genomes of other apicomplexans; they contain no identifiable domains or motifs and their function(s) is unknown. As a first step toward elucidating the function of this highly conserved family of proteins, we disrupted the TgCBAP gene by double homologous recombination. Parasites lacking TgCBAP are as sensitive to the effects of Conoidin A as wild-type parasites, demonstrating that TgCBAP is not the biologically relevant target of Conoidin A. However, ΔTgCBAP parasites are significantly shorter than wild-type parasites and have a growth defect in culture. Furthermore, TgCBAP has an unusual subcellular localization, forming small rings at the apical and basal ends of the parasite and localizing to punctate, ring-like structures around the parasite periphery. These data identify a new marker of the apical and basal subcompartments of T. gondii, reveal a potentially novel compartment along the parasite periphery, and identify TgCBAP as a determinant of parasite size that is required for a maximally efficient lytic cycle.

Bacterial resistance to antisense peptide phosphorodiamidate morpholino oligomers.

Peptide phosphorodiamidate morpholino oligomers (PPMOs) are synthetic DNA mimics that bind cRNA and inhibit bacterial gene expression. The PPMO (RFF)(3)RXB-AcpP (where R is arginine, F, phenylalanine, X is 6-aminohexanoic acid, B is ß-alanine, and AcpP is acyl carrier protein) is complementary to 11 bases of the essential gene acpP (which encodes acyl carrier protein). The MIC of (RFF)(3)RXB-AcpP was 2.5 µM (14 µg/ml) in Escherichia coli W3110. The rate of spontaneous resistance of E. coli to (RFF)(3)RXB-AcpP was 4 × 10(-7) mutations/cell division. A spontaneous (RFF)(3)RXB-AcpP-resistant mutant (PR200.1) was isolated. The MIC of (RFF)(3)RXB-AcpP was 40 µM (224 µg/ml) for PR200.1. The MICs of standard antibiotics for PR200.1 and W3110 were identical. The sequence of acpP was identical in PR200.1 and W3110. PR200.1 was also resistant to other PPMOs conjugated to (RFF)(3)RXB or peptides with a similar composition or pattern of cationic and nonpolar residues. Genomic sequencing of PR200.1 identified a mutation in sbmA, which encodes an active transport protein. In separate experiments, a (RFF)(3)RXB-AcpP-resistant isolate (RR3) was selected from a transposome library, and the insertion was mapped to sbmA. Genetic complementation of PR200.1 or RR3 with sbmA restored susceptibility to (RFF)(3)RXB-AcpP. Deletion of sbmA caused resistance to (RFF)(3)RXB-AcpP. We conclude that resistance to (RFF)(3)RXB-AcpP was linked to the peptide and not the phosphorodiamidate morpholino oligomer, dependent on the composition or repeating pattern of amino acids, and caused by mutations in sbmA. The data further suggest that (RFF)(3)R-XB PPMOs may be transported across the plasma membrane by SbmA.

Targeted disruption of TgPhIL1 in Toxoplasma gondii results in altered parasite morphology and fitness.

The inner membrane complex (IMC), a series of flattened vesicles at the periphery of apicomplexan parasites, is thought to be important for parasite shape, motility and replication, but few of the IMC proteins that function in these processes have been identified. TgPhIL1, a Toxoplasma gondii protein that was previously identified through photosensitized labeling with 5-[(125)I] iodonapthaline-1-azide, associates with the IMC and/or underlying cytoskeleton and is concentrated at the apical end of the parasite. Orthologs of TgPhIL1 are found in other apicomplexans, but the function of this conserved protein family is unknown. As a first step towards determining the function of TgPhIL1 and its orthologs, we generated a T. gondii parasite line in which the single copy of TgPhIL1 was disrupted by homologous recombination. The TgPhIL1 knockout parasites have a distinctly different morphology than wild-type parasites, and normal shape is restored in the knockout background after complementation with the wild-type allele. The knockout parasites are outcompeted in culture by parasites expressing functional TgPhIL1, and they generate a reduced parasite load in the spleen and liver of infected mice. These findings demonstrate a role for TgPhIL1 in the morphology, growth and fitness of T. gondii tachyzoites.

Antisense peptide-phosphorodiamidate morpholino oligomer conjugate: dose-response in mice infected with Escherichia coli.

OBJECTIVES: Phosphorodiamidate morpholino oligomers (PMOs) are DNA analogues that inhibit translation by an antisense mechanism. Membrane-penetrating peptides attached to PMOs increase PMO efficacy by enhancing penetration through bacterial membranes. The objectives of these experiments are to demonstrate gene-specific efficacy and establish a dose-response relationship of a peptide-PMO conjugate. METHODS: An 11-base PMO (AcpP) targeted at acpP (an essential gene) of Escherichia coli was synthesized and conjugated with the cell-penetrating peptide RFFRFFRFFRXB (X is 6-aminohexanoic acid and B is beta-alanine). Mice were infected by intraperitoneal (i.p.) injection with K-12 E. coli W3110, and treated i.p. at 15 min and 12 h post-infection with various amounts of AcpP peptide-PMO conjugate, AcpP PMO without attached peptide, scrambled base sequence PMOs or ampicillin. A strain (LT1) of E. coli was constructed by replacing acpP with an allele that has four wobble base substitutions in the region targeted by the PMO. RESULTS: Twelve hours after a single treatment, 30 microg of AcpP peptide-PMO or 3 mg of AcpP PMO reduced bacteraemia by 3 orders of magnitude compared with treatment with water. Neither scrambled base sequence PMO controls nor 30 microg of ampicillin reduced bacteraemia. Two treatments with 30 microg of AcpP peptide-PMO reduced cfu significantly more than four treatments with 15 microg at 15 min, 4, 8 and 12 h. Mice treated with doses of AcpP peptide-PMO > 30 microg showed further reductions in plasma cfu. Survival 48 h after treatment with 2 x 30 microg (3 mg/kg) of AcpP peptide-PMO or 2 x 3 mg (300 mg/kg) of AcpP PMO was 100%, compared with 20% for mice treated with water or scrambled base sequence PMO controls. However, survival was reduced to 75% and 0% for mice treated with 2 x 300 microg and 2 x 1 mg of AcpP peptide-PMO, respectively. A conjugate made from the D-isomeric form of each amino acid was less effective than the L-amino acid equivalent, and required 2 x 300 microg treatments for significant reduction in bacteria and survival. Mice infected with LT1 and treated with AcpP peptide-PMO did not survive and had the same amount of bacteria in the blood as mice treated with water, whereas those treated with 2 x 100 microg of AcpPmut4 peptide-PMO (complementary to the mutated allele) survived, and had a 3 orders of magnitude reduction in bacteria in the blood at 24 h post-infection. CONCLUSIONS: Both AcpP peptide-PMO and AcpP PMO significantly reduced bacteraemia and promoted survival of mice infected with E. coli W3110. The conjugate was about 50-100 times more potent than the PMO without attached peptide. The L-isomeric peptide-PMO was 10 times more potent than the D-isomeric equivalent. The conjugate apparently was toxic at doses > or = 2 x 300 microg/mouse (30 mg/kg). PMOs produced a sequence-specific antibiotic effect and the conjugate had a therapeutic index (toxic dose/effective dose) approximately equal to 10 in a mouse model of infection.

Gene-specific effects of antisense phosphorodiamidate morpholino oligomer-peptide conjugates on Escherichia coli and Salmonella enterica serovar typhimurium in pure culture and in tissue culture.

The objective was to improve efficacy of antisense phosphorodiamidate morpholino oligomers (PMOs) by improving their uptake into bacterial cells. Four different bacterium-permeating peptides, RFFRFFRFFXB, RTRTRFLRRTXB, RXXRXXRXXB, and KFFKFFKFFKXB (X is 6-aminohexanoic acid and B is beta-alanine), were separately coupled to two different PMOs that are complementary to regions near the start codons of a luciferase reporter gene (luc) and a gene required for viability (acpP). Luc peptide-PMOs targeted to luc inhibited luciferase activity 23 to 80% in growing cultures of Escherichia coli. In cell-free translation reactions, Luc RTRTRFLRRTXB-PMO inhibited luciferase synthesis significantly more than the other Luc peptide-PMOs or the Luc PMO not coupled to peptide. AcpP peptide-PMOs targeted to acpP inhibited growth of E. coli or Salmonella enterica serovar Typhimurium to various extents, depending on the strain. The concentrations of AcpP RFFRFFRFFXB-PMO, AcpP RTRTRFLRRTXB-PMO, AcpP KFFKFFKFFKXB-PMO, and ampicillin that reduced CFU/ml by 50% after 8 h of growth (50% inhibitory concentration [IC(50)]) were 3.6, 10.8, 9.5, and 7.5 microM, respectively, in E. coli W3110. Sequence-specific effects of AcpP peptide-PMOs were shown by rescuing growth of a merodiploid strain that expressed acpP with silent mutations in the region targeted by AcpP peptide-PMO. In Caco-2 cultures infected with enteropathogenic E. coli (EPEC), 10 microM AcpP RTRTRFLRRTXB-PMO or AcpP RFFRFFRFFXB-PMO essentially cleared the infection. The IC(50) of either AcpP RTRTRFLRRTXB-PMO or AcpP RFFRFFRFFXB-PMO in EPEC-infected Caco-2 culture was 3 microM. In summary, RFFRFFRFFXB, RTRTRFLRRTXB, or KFFKFFKFFXB, when covalently bonded to PMO, significantly increased inhibition of expression of targeted genes compared to PMOs without attached peptide.