Rescue of retroviral envelope fusion deficiencies by cationic liposomes

Abstract

These data have implications for the development of retroviral vector targeting strategies from the perspectives of the specificity of target cell interaction and compensating for chimaeric envelope fusion deficiency.

Design of Hybrid Lipid/Retroviral-Like Particle Gene Delivery Vectors

“…M-VLP were either incubated with these reagents prior to transfection or were added to target cells that were pre-incubated with the transfection reagents. Other similar work employed DOTAP and DC-Chol:DOPE (3:2) liposomes 18,41 . In the present study, we expanded upon these previous attempts in two ways.…”

Targeted retroviral gene delivery using ultrasound

“…Envelope‐deficient retrovirus carrying the nuclear‐localised β‐galactosidase marker gene was added to TE671 cells with cationic lipid microbubbles for exposure to ultrasound. Cationic microbubbles were chosen in anticipation of their electrostatic association with retroviral particles, comparable to the use of the former for binding plasmid DNA 19 and the association of retroviruses with cationic liposomes 26. Ultrasound pulses that consisted of ten identical cycles of a sinusoidal wave of 1 MHz frequency (Figure 1C) were generated with a repetition frequency of 1 kHz, amounting to 50 ms of ultrasound ‘on time’ during the 5 s exposure.…”

“…There was a low background level of transduction with sham ultrasound exposure and at positions exposed to < 0.2 MPa; however, ultrasound‐mediated delivery was > 100‐fold in excess of this background for pressure > 0.4 MPa. (Being microbubble‐ and incubation time‐dependent, the low background was attributed to the cationicity of the microbubbles directly aiding virus entry 26. )…”

“…With few exceptions, envelope engineering for retargeted binding and entry has not been successful 2. MLV particles lacking the envelope protein are incapable of infection, although the cores are still competent if the block to entry can be overcome by other means 26. Since, in respect of their systemic utility and capacity for being targeted, microbubbles possess the properties that have been sought for retroviral vectors, and since they can additionally achieve DNA entry dependent on ultrasound exposure, we investigated whether microbubbles could be used to effect targeted, ultrasound‐dependent entry of the core of an envelope‐deficient retroviral vector.…”

Changing Viral Tropism Using Immunoliposomes Alters the Stability of Gene Expression: Implications for Viral Vector Design

“…Since the initial description of lipofection as a mean of DNA transfection (39), cationic liposomes have been widely used for gene delivery both in vitro and in vivo (40,41). We, like others, have used liposomes to package viral particles to increase the infectivity (17,18,42).…”