Intramuscular immunization with poliovirus replicons primes for a humoral and cellular immune response to soluble antigen

CD34+ hematopoietic stem cells support entry and replication of poliovirus: a potential new gene introduction route

Pluripotent hematopoietic stem cells (HSC) are critical in sustaining and constantly renewing the blood and immune system. The ability to alter biological characteristics of HSC by introducing and expressing genes would have enormous therapeutic possibilities. Previous unpublished work suggested that human HSC co-express CD34 (cluster of differentiation 34; an HSC marker) and CD155 (poliovirus receptor; also called Necl-5/Tage4/PVR/CD155). In the present study, we demonstrate the co-expression of CD34 and CD155 in primary human HSC. In addition, we demonstrate that poliovirus infects and replicates in human hematopoietic progenitor cell lines. Finally, we show that poliovirus replicates in CD34+ enriched primary HSC. CD34+ enriched HSC co-express CD155 and support poliovirus replication. These data may help further understanding of poliovirus spread in vivo and also demonstrate that human HSC may be amenable for gene therapy via poliovirus-capsid-based vectors. They may also help elucidate the normal function of Necl-5/Tage4/PVR/CD155.

Immunization with non-replicating E. coli minicells delivering both protein antigen and DNA protects mice from lethal challenge with lymphocytic choriomeningitis virus

In the midst of new investigations into the mechanisms of both delivery and protection of new vaccines and vaccine carriers, it has become clear that immunization with delivery mechanisms that do not involve living, replicating organisms are vastly preferred. In this report, non-replicating bacterial minicells simultaneously co-delivering the nucleoprotein (NP) of lymphocytic choriomeningitis virus (LCMV) and the corresponding DNA vaccine were tested for the ability to generate protective cellular immune responses in mice. It was found that good protection (89%) was achieved after intramuscular administration, moderate protection (31%) was achieved after intranasal administration, and less protection (7%) was achieved following gastric immunization. These results provide a solid foundation on which to pursue the use of bacterial minicells as a non-replicating vaccine delivery platform.

Immune responses elicited by bacterial minicells capable of simultaneous DNA and protein antigen delivery

Recent events surrounding emerging infectious diseases, bioterrorism and increasing multidrug antibiotic resistance in bacteria have drastically increased current needs for effective vaccines. Many years of study have shown that live, attenuated pathogens are often more effective at delivering heterologous protein or DNA to induce protective immune responses. However, these vaccine carriers have inherent safety concerns that have limited their development and their use in many patient populations. Studies using nonliving delivery mechanisms have shown that providing both protein antigen and DNA encoding the antigen to an individual induces an improved, more protective immune response but rarely, if ever, are both delivered simultaneously. Here, non-replicating bacterial minicells derived from a commensal E. coli strain are shown to effectively induce antigen-specific immune responses after simultaneous protein and DNA delivery. These data demonstrate the potential use of achromosomal bacterial minicells as a vaccine carrier.

Gene expression in the muscle and central nervous system following intramuscular inoculation of encapsidated or naked poliovirus replicons

The spread of intramuscularly inoculated poliovirus to the central nervous system (CNS) has been documented in humans, monkeys, and mice transgenic for the human poliovirus receptor. Poliovirus spread is thought to be due to infection of the peripheral nerve and retrograde transport of poliovirus through the axon to the neuron cell body, where final virus uncoating occurs and translation/replication ensues. In previous studies, we have shown that polio-based vectors (replicons) can be used for gene delivery to motor neurons of the CNS. Using a replicon that encodes green fluorescent protein (GFP), we found that following intrathecal inoculation, GFP expression was confined to motorneurons of the spinal cord. To further characterize the gene expression of poliovirus in the periphery and CNS, we have intramuscularly inoculated transgenic mice with poliovirus replicons encoding GFP. Expression of GFP was demonstrated in the muscle, sciatic nerve, dorsal root ganglion, and the ventral horn motorneurons following intramuscular inoculation. There was no evidence of paralysis or behavioral abnormalities in the mice following intramuscular inoculation of the replicon encoding GFP. Injection of replicon RNA alone (naked RNA) into the muscle of transgenic mice or rats, which do not express the poliovirus receptor, also resulted in expression of GFP in the muscle, sciatic nerve, dorsal root ganglion, and ventral horn motorneurons, indicating that transport of the replicon RNA from the periphery to CNS had occurred. GFP expression was found in the muscles and sciatic nerve as early as 6 h after injection of replicons or replicon RNA, even after sciatic nerve section. Analysis at longer times postinjection revealed GFP expression similar to 6 h levels in the cut sciatic nerves and robust expression in the nerves of uncut animals. The infection and expression of GFP in the CNS following intramuscular inoculation of encapsidated replicons encoding GFP occurred in juvenile or adult animals. The expression of GFP in the CNS of juvenile animals was more intense and lasted for up to 5 weeks, in contrast to the duration of expression of approximately 96 h for adult animals. The results of these studies establish that poliovirus replicon RNA is expressed locally within the sciatic nerve and transported from the periphery to the CNS via axonal transport and support the potential of replicons for gene delivery to the CNS.