Tissue distribution of a plasmid DNA encoding Hsp65 gene is dependent on the dose administered through intramuscular delivery

In order to assess a new strategy of DNA vaccine for a more complete understanding of its action in immune response, it is important to determine the in vivo biodistribution fate and antigen expression. In previous studies, our group focused on the prophylactic and therapeutic use of a plasmid DNA encoding the Mycobacterium leprae 65-kDa heat shock protein (Hsp65) and achieved an efficient immune response induction as well as protection against virulent M. tuberculosis challenge. In the present study, we examined in vivo tissue distribution of naked DNA-Hsp65 vaccine, the Hsp65 message, genome integration and methylation status of plasmid DNA. The DNA-Hsp65 was detectable in several tissue types, indicating that DNA-Hsp65 disseminates widely throughout the body. The biodistribution was dose-dependent. In contrast, RT-PCR detected the Hsp65 message for at least 15 days in muscle or liver tissue from immunized mice. We also analyzed the methylation status and integration of the injected plasmid DNA into the host cellular genome. The bacterial methylation pattern persisted for at least 6 months, indicating that the plasmid DNA-Hsp65 does not replicate in mammalian tissue, and Southern blot analysis showed that plasmid DNA was not integrated. These results have important implications for the use of DNA-Hsp65 vaccine in a clinical setting and open new perspectives for DNA vaccines and new considerations about the inoculation site and delivery system.     

Glutamic acid and gamma-aminobutyric acid neurotransmitters in central control of breathing.

We review recent cross-disciplinary experimental and theoretical investigations on metabolism of the amino acid neurotransmitters glutamic acid and gamma-aminobutyric acid (GABA) in the brain during hypoxia and hypercapnia and their possible role in central control of breathing. The roles of classical modifiers of central chemical drive to breathing (H+ and cholinergic mechanisms) are summarized. A brief perspective on the current widespread interest in GABA and glutamate in central control is given. The basic biochemistry of these amino acids and their roles in ammonia and bicarbonate metabolism are discussed. This review further addresses recent work on central respiratory effects of inhibitory GABA and excitatory glutamate. Current understanding of the sites and mechanisms of action of these amino acids on or near the ventral surface of the medulla is reviewed. We focus particularly on tracer kinetic investigations of glutamatergic and GABAergic mechanisms in hypoxia and hypercapnia and their possible role in the ventilatory response to hypoxia. We conclude with some speculative remarks on the critical importance of these investigations and suggest specific directions of research in central mechanisms of respiratory control.