Lipid peptide nanocomplexes for gene delivery and magnetic resonance imaging in the brain.

Gadolinium-labelled nanocomplexes offer prospects for the development of real-time, non-invasive imaging strategies to visualise the location of gene delivery by MRI. In this study, targeted nanoparticle formulations were prepared comprising a cationic liposome (L) containing a Gd-chelated lipid at 10, 15 and 20% by weight of total lipid, a receptor-targeted, DNA-binding peptide (P) and plasmid DNA (D), which electrostatically self-assembled into LPD nanocomplexes. The LPD formulation containing the liposome with 15% Gd-chelated lipid displayed optimal peptide-targeted, transfection efficiency. MRI conspicuity peaked at 4h after incubation of the nanocomplexes with cells, suggesting enhancement by cellular uptake and trafficking. This was supported by time course confocal microscopy analysis of transfections with fluorescently-labelled LPD nanocomplexes. Gd-LPD nanocomplexes delivered to rat brains by convection-enhanced delivery were visible by MRI at 6 h, 24 h and 48 h after administration. Histological brain sections analysed by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) confirmed that the MRI signal was associated with the distribution of Gd(3+) moieties and differentiated MRI signals due to haemorrhage. The transfected brain cells near the injection site appeared to be mostly microglial. This study shows the potential of Gd-LPD nanocomplexes for simultaneous delivery of contrast agents and genes for real-time monitoring of gene therapy in the brain.

Immune response in humans to a nasal boost with Streptococcus mutans antigens.

We previously reported that a Streptococcus mutans enriched-glucosytransferase (E-GTF) preparation induces an immune response following intranasal, but not tonsillar, immunization of humans. In this study, we determined whether intranasal immunization of these subjects 2 years later resulted in augmented immune responses compared to those seen in control subjects. Subjects previously immunized via the intranasal (IN, n = 7) or tonsillar (IT, n = 7) route and control (n = 12) subjects were immunized via the intranasal route with E-GTF. Nasal wash, saliva, and serum were collected before immunization and then weekly for 3 months after immunization. Significant (P < 0.05) mucosal and serum immunoglobulin A (IgA) anti-E-GTF responses were observed in all three groups. Nasal and serum IgA anti-E-GTF responses were significantly higher (P < 0.05) in the IN group. The salivary responses in the three groups were, in general, similar. These results indicate that intranasal immunization primes the immune system for a localized secondary response to S. mutans antigens.