Seiichi Tanaka

Genetic Analysis of Rabies Virus Isolates in the Philippines

To determine the genetic characteristics of the rabies virus in the Philippines, 59 rabies virus isolates were obtained from domestic rabid dogs and their partial nucleotide sequences of nucleoprotein (N) gene were compared. Based on comparison with reported sequences, phylogenetic analysis revealed that all isolates from the Philippines had close genetic relations and formed two subgroups. The Philippines isolates belonged to a different lineage from other Asian isolates but were closer to them than to terrestrial isolates and laboratory strains. Several specific nucleotide and amino acid substitutions were observed among the Philippines isolates. Our results suggest that rabies viruses in the Philippines might have a characteristic evolution.

Identification of immunodominant neutralizing epitopes on the hemagglutinin protein of rinderpest virus.

ABSTRACT The immunodominant epitopes on the hemagglutinin protein of rinderpest virus (RPV-H) were determined by analyzing selected monoclonal antibody (MAb)-resistant mutants and estimating the level of antibody against each epitope in five RPV-infected rabbits with the competitive enzyme-linked immunosorbent assay (c-ELISA). Six neutralizing epitopes were identified, at residues 474 (epitope A), 243 (B), 548 to 551 (D), 587 to 592 (E), 310 to 313 (G), and 383 to 387 (H), from the data on the amino acid substitutions of hemagglutinin protein of MAb-resistant mutants and the reactivities of MAbs against RPV-H to the other morbilliviruses. The epitopes identified in this study are all positioned on the loop of the propeller-like structure in a hypothetical three-dimensional model of RPV-H (J. P. M. Langedijk et al., J. Virol. 71:6155-6167, 1997). Polyclonal sera obtained from five rabbits infected experimentally with RPV were examined by c-ELISA using a biotinylated MAb against each epitope as a competitor. Although these rabbit sera hardly blocked binding of each MAb to epitopes A and B, they moderately blocked binding of each MAb to epitopes G and D and strongly blocked binding of each MAb to epitopes E and H. These results suggest that epitopes at residues 383 to 387 and 587 to 592 may be immunodominant in humoral immunity to RPV infection.

Acetylcholine activates latent pseudorabies virus in pigs.

SummaryPseudorabies virus (PrV) was isolated from the nasal swabs and the cultured trigeminal ganglia of latently infected pigs after they were treated with acetylcholine (ACH). These results indicated that ACH activates latent infections of PrV.

Acetylcholine reactivates latent pseudorabies virus in mice

The latency model of pseudorabies virus (PrV) wild strain, YS-81, in mice was established and latent PrV reactivated with acetylcholine. The latent PrV was reactivated from the trigeminal ganglia with acetylcholine. It was found that this model is useful in investigating the mechanism of latent PrV reactivation by acetylcholine.

Establishment of an Alzheimer’s disease model with latent herpesvirus infection using PS2 and Tg2576 double transgenic mice

A relationship between Alzheimer’s disease and herpes simplex virus infection has been pointed out. We established a model of Alzheimer’s disease with a latent herpesvirus infection using a mouse model of Alzheimer’s disease (PS2Tg2576) and examined the changes in amyloid β (Aβ) in the brain. We crossbred female PS2 mice with male Tg2576 hemi mice and chose PS2Tg2576 mice. After priming 5-week-old male mice with anti-pseudorabies virus swine serum, we challenged the mouse with 100 LD50 of YS-81, a wild-type strain of pseudorabies virus. The viral DNA was detected in nasal swabs by a reactivation test and in the trigeminal ganglia. At two months after infection, the Aβ40 and Aβ42 levels in the brains of the mice of the latently infected group were increased; the increase was greater than that observed in the noninfected group. Latent pseudorabies virus infection was established in PS2Tg2576 mice and the level of Aβ increased with the reactivation of the latent virus.

Analysis of the mechanism of reactivation of latently infecting pseudorabies virus by acetylcholine.

ABSTRACT In this study, the effect of cholinergic or adrenergic inhibitors on the reactivation of latent Pseudorabies virus (PRV) was analyzed to clarify the mechanism of the reactivation of latent PRV by acetylcholine. For acetylcholine inhibition, latently infected mice were injected with scopolamine or succynilcholine before acetylcholine stimulation. For sympathetic blocking, mice were preinjected intraperitoneally with phenoxybenzamine or propranolol. The signals to both acetylcholine receptors had no relationship to the reactivation of latent PRV, and both sympathetic blockers showed inhibition of PRV reactivation by acetylcholine. In our reactivation model, a large amount of acetylcholine may stimulate the sympathetic nerve system in some way to reactivate the virus.