Plasmid-only rescue of influenza A virus vaccine candidates

The potential threat of another influenza virus pandemic stimulates discussion on how to prepare for such an event. The most reasonable prophylactic approach appears to be the use of effective vaccines. Since influenza and other negative-stranded RNA viruses are amenable to genetic manipulation using transfection by plasmids, it is possible to outline new reverse genetics-based approaches for vaccination against influenza viruses. We suggest three approaches. First, we use a plasmid-only rescue system that allows the rapid generation of high-yield recombinant vaccine strains. Second, we propose developing second-generation live influenza virus vaccines by constructing an attenuated master strain with deletions in the NS1 protein, which acts as an interferon antagonist. Third, we suggest the use of Newcastle disease virus recombinants expressing influenza virus haemagglutinin proteins of pandemic (epizootic) strains as novel vaccine vectors for use in animals and possibly humans.

Expression of the purported sigma(1) (sigma(1)) receptor in the mammalian brain and its possible relevance in deficits induced by antagonism of the NMDA receptor complex as revealed using an antisense strategy

Sigma (sigma) receptors have generated a great deal of interest on the basis of their possible role in psychosis, neuroprotection and various other behaviors including learning processes. The existence of at least two classes of sigma receptor binding sites (sigma(1) and sigma(2)) is now well established. The recent cloning of the mouse, guinea pig and human sigma(1) receptors has allowed the study of the discrete distribution of the sigma(1) receptor mRNA in rodent and human brain tissues using in situ hybridization. Overall, the sites of expression of specific sigma(1) receptor mRNA signals were in accordance to the anatomical distribution of sigma(1) receptor protein first established by quantitative receptor autoradiography. Specific sigma(1) receptor hybridization signals were found to be widely, but discretely distributed, in mouse and guinea pig brain tissues. The highest levels of transcripts were seen in various cranial nerve nuclei. Lower, but still high hybridization signals were observed in mesencephalic structures such as the red nucleus, periaqueductal gray matter and substantia nigra, as well as in some diencephalic structures including such as the habenula and the arcuate, paraventricular and ventromedial hypothalamic nuclei. Superficial (I-II) and deeper (IV-VI) cortical laminae were moderately labeled in the mouse brain. Moderate levels of sigma(1) receptor mRNA were also found in the pyramidal cell layer and the dentate gyrus of the hippocampal formation. Other structures such as the thalamus and amygdaloid body also expressed the sigma(1) receptor mRNA although to a lesser extent. In murine peripheral tissues, strong hybridization signals were observed in the liver, white pulp of the spleen and the adrenal gland. In the postmortem human brain, moderate levels of sigma(1) receptor mRNA, distributed in a laminar fashion, were detected in the temporal cortex with the deeper laminae (IV-VI) being particularly enriched. In the hippocampal formation, the strongest hybridization signals were observed in the dentate gyrus while all other subfields of the human hippocampal formation expressed lower levels of the sigma(1) receptor mRNA. Antisense oligodeoxynucleotides against the purported sigma(1) receptor were used next to investigate the possible role of this receptor in dizocilpine (MK-801)/NMDA receptor blockade-induced amnesia. Following a continuous intracerebroventricular infusion of a specific sigma(1) receptor antisense into the third ventricle (0.4 nmol/h for 5 days), sigma(1)/[3H](+)pentazocine binding was significantly reduced in mouse brain membrane homogenates while a scrambled antisense control was without effect. Moreover, the sigma(1) receptor antisense treatments (5 nmol/injection, every 12 hx3 or 0.4 nmol/h for 5 days) attenuated (+)MK-801/NMDA receptor blockade-induced cognitive deficits in the treated mice while a scrambled antisense control had no effect. Taken together, these results demonstrate the widespread, but discrete, distribution of the sigma(1) receptor mRNA in the mammalian central nervous system. Moreover, antisense treatments against the purported sigma(1) receptor gene reduced specific sigma(1)/[3H](+)pentazocine binding and modulated cognitive behaviors associated with NMDA receptor blockade providing further evidence for the functional relevance of the cloned gene.

Purification, molecular cloning, and expression of the mammalian sigma1-binding site

Sigma-ligands comprise several chemically unrelated drugs such as haloperidol, pentazocine, and ditolylguanidine, which bind to a family of low molecular mass proteins in the endoplasmic reticulum. These so-called sigma-receptors are believed to mediate various pharmacological effects of sigma-ligands by as yet unknown mechanisms. Based on their opposite enantioselectivity for benzomorphans and different molecular masses, two subtypes are differentiated. We purified the sigma1-binding site as a single 30-kDa protein from guinea pig liver employing the benzomorphan(+)[3H]pentazocine and the arylazide (-)[3H]azidopamil as specific probes. The purified (+)[3H]pentazocine-binding protein retained its high affinity for haloperidol, pentazocine, and ditolylguanidine. Partial amino acid sequence obtained after trypsinolysis revealed no homology to known proteins. Radiation inactivation of the pentazocine-labeled sigma1-binding site yielded a molecular mass of 24 +/- 2 kDa. The corresponding cDNA was cloned using degenerate oligonucleotides and cDNA library screening. Its open reading frame encoded a 25.3-kDa protein with at least one putative transmembrane segment. The protein expressed in yeast cells transformed with the cDNA showed the pharmacological characteristics of the brain and liver sigma1-binding site. The deduced amino acid sequence was structurally unrelated to known mammalian proteins but it shared homology with fungal proteins involved in sterol synthesis. Northern blots showed high densities of the sigma1-binding site mRNA in sterol-producing tissues. This is also in agreement with the known ability of sigma1-binding sites to interact with steroids, such as progesterone.