While the RNA-dependent RNA polymerase L protein of rabies virus (RABV), a member of the genus of the family, has potential to be a therapeutic target for rabies, the molecular functions of this protein have remained largely unknown. In this study, to obtain a novel experimental tool for molecular function analysis of the RABV L protein, we established by using a reverse genetics approach an L gene-deficient RABV (Nishi-ΔL/Nluc), which infects, propagates, and correspondingly produces NanoLuc luciferase in cultured neuroblastoma cells transfected to express the L protein. -Complementation with wild-type L protein, but not that with a functionally defective L protein mutant, efficiently supported luciferase production by Nishi-ΔL/Nluc, confirming its potential for function analysis of the L protein. Based on the findings obtained from comprehensive genetic analyses of L genes from various RABV and other lyssavirus species, we examined the functional importance of a highly conserved L protein region at positions 1914 to 1933 by a-complementation assay with Nishi-ΔL/Nluc and a series of L protein mutants. The results revealed that the amino acid sequence at positions 1929 to 1933 (NPYNE) is functionally important, and this was supported by other findings that this sequence is critical for binding of the L protein with its essential cofactor, P protein, and thus also for L protein's RNA polymerase activity. Our findings provide useful information for the development of an anti-RABV drug targeting the L-P protein interaction. To the best of our knowledge, this is the first report on the establishment of an L gene-deficient, reporter gene-expressing virus in all species of the order , also highlighting its applicability to a-complementation assay, which is useful for molecular function analyses of their L proteins. Moreover, this study revealed for the first time that the NPYNE sequence at positions 1929 to 1933 in the RABV L protein is important for L protein's interaction with the P protein, consistent with and extending the results of a previous study showing that the P protein-binding domain in the L protein is located in its C-terminal region, at positions 1562 to 2127. This study indicates that the NPYNE sequence is a promising target for the development of an inhibitor of viral RNA synthesis, which has high potential as a therapeutic drug for rabies.

Losses of neutral beam (NB) injected fast ions from the confinement region of a field-reversed configuration (FRC) with a strong magnetic mirror are numerically analyzed for parameters relevant to NB injection experiments on the FIX (FRC injection experiment) device [T. Asai et al., Phys. Plasmas 7, 2294 (2000)]. Ionization processes of beam particles are calculated by the Monte Carlo method. The confinement of beam ions is discussed with the concept of accessible regions that restrict the ion excursion and are determined from two constants of motion, the kinetic energy and canonical angular momentum, in the case of an axisymmetric and a steady state FRC without an electrostatic field. From the calculation of the accessible regions, it is found that all the fast ions suffer from the orbit loss on the wall surface and/or the end loss. Single particle orbits are also calculated to find a difference of confinement properties from the results by employing the accessible regions. The magnetic moment is observed to show nonadiabatic motions of the beam ions, which cause a gradual orbit loss on the wall even in a case that a strong magnetic mirror is applied. The results show that the correlation of the magnetic moment disappears as the fast ions experience the density gradient around the separatrix surface and the field-null points.

The effects of Coulomb collisions on neutral beam (NB) injected fast ions into field-reversed configuration (FRC) plasmas are investigated by calculating the single particle orbits, where the ions are subject to the slowing-down and pitch-angle collisions. The Monte Carlo method is used for the pitch-angle scattering, and the friction term is added to the equation of motion to show the effects of the slowing-down collision, such as the deposited power profile. The calculation parameters used are relevant to the NB injection on the FRC injection experiment device [T. Asai, Y. Suzuki, T. Yoneda, F. Kodera, M. Okubo, and S. Goto, Phys. Plasmas 7, 2294 (2000)]. It is found that the dominant local power deposition occurs in the open field region between the X point and the mirror point because of a concentration of fast ions and a longer duration travel at the mirror reflection point. In the present calculation, the maximum deposited power to the FRC plasma is about 10% of the injected power. Although the pitch-angle scattering by Coulomb collision destroys the mirror confinement of NB injected fast ions, this effect is found to be negligible. The loss mechanism due to nonadiabatic fast ion motion, which is intrinsic in nonuniform FRC plasmas, has a much greater effect than the pitch-angle scattering by Coulomb collision.