A fusion-inhibiting peptide against Rift Valley fever virus inhibits multiple, diverse viruses.

For enveloped viruses, fusion of the viral envelope with a cellular membrane is critical for a productive infection to occur. This fusion process is mediated by at least three classes of fusion proteins (Class I, II, and III) based on the protein sequence and structure. For Rift Valley fever virus (RVFV), the glycoprotein Gc (Class II fusion protein) mediates this fusion event following entry into the endocytic pathway, allowing the viral genome access to the cell cytoplasm. Here, we show that peptides analogous to the RVFV Gc stem region inhibited RVFV infectivity in cell culture by inhibiting the fusion process. Further, we show that infectivity can be inhibited for diverse, unrelated RNA viruses that have Class I (Ebola virus), Class II (Andes virus), or Class III (vesicular stomatitis virus) fusion proteins using this single peptide. Our findings are consistent with an inhibition mechanism similar to that proposed for stem peptide fusion inhibitors of dengue virus in which the RVFV inhibitory peptide first binds to both the virion and cell membranes, allowing it to traffic with the virus into the endocytic pathway. Upon acidification and rearrangement of Gc, the peptide is then able to specifically bind to Gc and prevent fusion of the viral and endocytic membranes, thus inhibiting viral infection. These results could provide novel insights into conserved features among the three classes of viral fusion proteins and offer direction for the future development of broadly active fusion inhibitors.

Application of the Ibis-T5000 pan-Orthopoxvirus assay to quantitatively detect monkeypox viral loads in clinical specimens from macaques experimentally infected with aerosolized monkeypox virus.

Monkeypox virus (MPXV), a member of the family Poxviridae and genus Orthopoxvirus, causes a smallpox-like disease in humans. A previously described pan-Orthopoxvirus assay, based on a broad-range polymerase chain reaction (PCR) coupled with electrospray ionization mass spectrometry (PCR/ESI-MS), was evaluated for its ability to detect MPXV from spiked human and aerosol-infected cynomolgous macaque (Macaca fascicularis) samples. Detection of MPXV DNA from macaque tissue, blood, and spiked human blood by the PCR/ESI-MS pan-Orthopoxvirus assay was comparable, albeit at slightly higher levels, to the current gold standard method of real-time PCR with the pan-Orthopoxvirus assay and had a limit of detection of 200 plaque-forming units. Furthermore, the platform was able to distinguish MPXV and vaccinia viruses that were spiked into macaque blood samples at various concentrations. This platform provides a new tool for the diagnosis and monitoring of orthopoxviral loads during vaccine or antiviral studies, but also could provide rapid identification during natural outbreaks or bioterrorism attacks.

Expression from baculovirus and serological reactivity of the nucleocapsid protein of dolphin morbillivirus.

The nucleocapsid (N) protein of dolphin morbillivirus (DMV) was expressed from a baculovirus (Autographa californica nuclear polyhedrosis virus) vector and shown by SDS-PAGE and Western blot analysis to be about 57 kDa. Transmission electron microscopy revealed fully assembled nucleocapsid-like particles (NLPs) exhibiting the typical helical herringbone morphology. These NLPs were approximately 20-22 nm in diameter and varied in length from 50 to 100 nm. Purified DMV-N protein was used as antigen in an indirect ELISA (iELISA) and shown to react with rabbit and human antisera to measles virus (MV) and dog sera with antibodies to canine distemper virus (CDV). The iELISA was used for the demonstration of morbillivirus antibodies in the serum of cetaceans and manatees, showing potential as a serological tool for the mass screening of morbillivirus antibodies in marine mammals.

Real-time RT-PCR assays for the rapid and differential detection of dolphin and porpoise morbilliviruses.

Real-time RT-PCR (rtRT-PCR) assays for identifying and differentiating infections caused by dolphin morbillivirus (DMV) and porpoise morbillivirus (PMV) were developed by targeting the hypervariable C-terminal domain of the nucleocapsid (N) gene. Total DMV and PMV RNA extracted from infected Vero cells expressing the canine signaling lymphocyte-activation molecule (SLAM) produced positive cycle threshold (C(T)) values after the 17th and 25th cycles, respectively. The assays were then validated using infected cetacean tissue RNA. The assays were specific for either DMV or PMV and did not cross-react with canine distemper virus (CDV), phocid distemper virus (PDV), rinderpest virus (RPV), peste des petits ruminants virus (PPRV) and measles virus (MV). The glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene was targeted as control for RNA quality, and a consensus GAPDH probe that reacted with 11 different marine mammal species, generating positive C(T) values ranging from the 21st to the 37th cycle was used. The rtRT-PCR assays have advantages over conventional assays in that they are rapid, easier to scale up, and are less prone to cross-contamination and have improved the limit of detection and specificity.

Sequence of the nucleocapsid gene and genome and antigenome promoters for an isolate of porpoise morbillivirus.

We have determined the first complete sequence of the nucleocapsid (N) gene of the porpoise morbillivirus (PMV) as well as the genome leader and trailer sequences which encode the genome and antigenome promoters, respectively. The PMV N gene is 1686 nucleotides long with a single open reading frame (ORF) encoding a protein of 523 amino acids with a predicted molecular weight of 57.39kDa. The nucleotide sequence of the N gene shows the closest identity (89%) to that of another cetacean morbillivirus, dolphin morbillivirus (DMV). Lower degrees of identity were found with the other members of the morbilliviruses genus; 67% identity to PDV and RPV, 68% to PPRV, 69% to CDV and 70% to MV. The distance from the 3' end of the genome up to the start of the N ORF is 107 nucleotides, identical to that found in all other morbilliviruses, and encompasses the genome promoter (GP) sequence. This promoter shows the same regions of conservation as found in other morbilliviruses with repeated CXXXXX motifs at positions 79-84, 85-90, and 91-96, the same bi-partite promoter arrangement found in many paramyxoviruses. The antigenome promoter (AGP) shows a similar arrangement, indicating a high degree of conservation in these functionally important regions.

Intracranial self-stimulation of the dorsal raphe sensitizes psychostimulant locomotion.

The authors hypothesized that repeated rewarding electrical stimulation of the dorsal raphe can produce behavioral sensitization to psychostimulants. Groups of male rats were implanted with a stimulation electrode and preexposed to brain stimulation at parameters set to equate rewarding effectiveness across rats. Control groups were implanted with an electrode but never stimulated, or not implanted at all. Twenty-four hours after the 12th self-stimulation session, all groups were challenged with amphetamine (0.5 mg/kg, ip), nicotine (0.2 mg/kg, sc), or saline, and locomotor activity was measured for 1 hr. Locomotor responses to amphetamine and to nicotine were significantly greater in rats preexposed to brain stimulation. These findings suggest at least partial overlap of underlying substrates. ((c) 2007 APA, all rights reserved).

Peripubertal environmental enrichment reverses the effects of maternal care on hippocampal development and glutamate receptor subunit expression.

Maternal care in the rat influences the development of cognitive function in the offspring through neural systems known to mediate activity-dependent synaptic plasticity. The offspring of mothers that exhibit increased levels of pup licking/grooming (high-LG mothers) show increased hippocampal N-methyl-D-aspartate (NMDA) subunit mRNA expression, enhanced synaptogenesis and improved hippocampal-dependent spatial learning in comparison with animals reared by low-LG mothers. The effects of reduced maternal care on cognitive function are reversed with peripubertal environmental enrichment; however, the neural mechanisms mediating this effect are not known. In these studies we exposed the offspring of high- and low-LG mothers to environmental enrichment from days 22 to 70 of life, and measured the expression of genes encoding for glutamate receptor subunits and synaptophysin expression as a measure of synaptic density. Environmental enrichment reversed the effects of maternal care on synaptic density and this effect was, in turn, associated with a reversal of the effect of maternal care on the NR2A and NR2B subunits of the NMDA receptor, as well as effects on (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits. Finally, direct infusion of an NR2B-specific NMDA receptor antagonist into the hippocampus eliminated the effects of maternal care on spatial learning/memory in the Morris water maze. These findings suggest that: (1) the effects of maternal care are mediated by changes in NR2B gene expression; and (2) that environmental enrichment reverses the effects of reduced maternal care through the same genomic target, the NR2B gene, and possibly effects on other subunits of the NMDA and AMPA receptors.

Maternal care influences neuronal survival in the hippocampus of the rat.

Maternal care during the first week of postnatal life influences hippocampal development and function (Liu et al., 2000; Nature Neurosci., 3, 799-806). Offspring reared by mothers who exhibit increased levels of pup licking/grooming (LG) show increased hippocampal synaptic density and enhanced spatial learning and memory. Using 5-bromo-2'-deoxyuridine (BrdU), a thymidine analogue incorporated into cells during DNA synthesis, we examined the effects of early maternal care on hippocampal cell proliferation and neuronal survival in the rat. Twenty-four hours following injection on day 7 of life (P7) there were no differences in BrdU labelling in the offspring of high- compared with low-LG mothers, suggesting no maternal effect on the rate of proliferation at this age. However, 14 and 83 days following injection (P21 and P90), the offspring of high-LG mothers had significantly more surviving BrdU-labelled cells and BrdU-NeuN+-colabelled neurons in the dentate gyrus subgranular zone and granule cell layer. At P21, the offspring of high-LG mothers showed increased protein expression of basic fibroblast growth factor and significantly decreased levels of pyknosis. These findings suggest an influence of maternal care on neuronal survival in the hippocampus. Conversely, at the same time point there was a significantly higher level of hippocampal glial fibrillary acidic protein expression in the offspring of low-LG mothers. These findings emphasize the importance of early maternal care for hippocampal development.

Maternal behavior regulates long-term hippocampal expression of BAX and apoptosis in the offspring.

Naturally occurring variations in maternal care influence hippocampal development in the rat. In the present study we found that variations in maternal licking/grooming (LG) during the first week of life are associated with altered hippocampal expression of BAX (group-1 tumor necrosis factor family mediated cell death effector) in 90-day-old male offspring. BAX-like immunoreactivity on western blots is significantly increased in the adult offspring of low-level LG mothers. There is no effect of maternal care on levels of either B-cell lymphoma-2 (BCL-2) (group-II mitochondria mediated cell death suppressor) or BAD (group-III endoplasmic reticulum mediated cell death effector). The most striking biochemical event in apoptosis is DNA fragmentation. Terminal deoxynucleotidyl transerferase (Tdt)-mediated dUTP-biotin nick-end labeling (TUNEL) and 4',6'-diamidino-2-phenylindole hydrochloride (DAPI) staining showed that the number of TUNEL-positive cells in both the dentate gyrus and CA1 region of the hippocampus is significantly increased in the adult offspring of low-level LG mothers. In conclusion, we propose that hippocampal neurons in the offspring of low-level LG mothers may be more vulnerable to loss through apoptosis.

Evidence for sequence-dependent and reversible nonspecific effects of PS-capped antisense treatment after intracerebral administration.

Phosphorothioate (PS)-capped phosphodiester (PE) oligodeoxynucleotides (ODNs) were used to determine whether the dopamine-dependent locomotor-stimulant effect of nicotine is mediated via a4 subunit-containing nicotinic receptors. To this end, rats received direct intraventral tegmental area infusion of a4 antisense via osmotic minipump, and their locomotor response to nicotine (0.2 mg/kg, s.c.) was tested. Eight antisense ODNs were screened, but only one inhibited nicotine-induced locomotion. This inhibition was reversible and selective, insofar as basal (saline) activity was unaffected, and a mismatch ODN was without effect. However, antisense treatment also caused sequence-dependent toxic effects, including neuronal degeneration in the ventral tegmental area, dopaminergic denervation, and weight loss. We conclude that despite previous reports, PS-capped PE-ODNs can cause severe neurotoxicity on chronic infusion into brain tissue. Moreover, sequence dependence and temporal reversibility, two generally accepted criteria of antisense action, may sometimes reflect the occurrence of toxic effects and resultant functional compensation.