Shuichi Tono-oka

Effect of MDP-Lys(L18) as a mucosal immunoadjuvant on protection of mucosal infections by Sendai virus and rotavirus

To examine the effect of MDP-Lys(L18), a derivative of muramyl dipeptide (MDP), as a mucosal immunoadjuvant, we investigated its activity to augment host resistance against mucosal infections by Sendai virus and rotavirus in mice. In an experimental infection model using suckling mice (10-day-old) inoculated perorally (p.o.) with 1.5 x 10(6) p.f.u. mouse-1 of rotavirus strain SA11, intrarectal (i.r.) as well as p.o. administration of MDP-Lys(L18) (50 micrograms mouse-1) prior to virus infection markedly reduced rotavirus-induced diarrhea. Furthermore, when MDP-Lys(L18) was administered p.o. (1 mg mouse-1), i.r. (300 micrograms mouse-1) or intranasally (i.n., 100 micrograms mouse-1) various days before Sendai virus infection (2.6 x 10(4) HAD mouse-1), all the mucosal administration of MDP-Lys(L18) significantly protected a lethal infection of Sendai virus, showing a dose-dependent manner. However, the efficacy of MDP-Lys(L18) to induce the prophylactic activity against the viruses somewhat varied according to the administration route and timing. In time course analysis of virus isolation in vivo, the mice administered with MDP-Lys(L18) exhibited a significant reduction of both viruses in the lungs for Sendai virus and in the bowels for rotavirus. These results suggest that MDP-Lys(L18) is a potent mucosal immunoadjuvant to enhance nonspecific host resistance against two mucosal infectious viruses, Sendai virus and rotavirus.

Characterization of neutralizing monoclonal antibody escape mutants of Hantaan virus 76118

SummaryNeutralizing monoclonal antibody (MAb) escape mutants of Hantaan virus were generated using MAbs to envelope protein G1 (16D2) and G2 (11E10). The mutant viruses (mu16D2 and mu11E10), lacked reactivity only to the selecting MAb, or a MAb belonging to the same antigenic site. Both mutants had a single amino acid (a.a.) substitution. The a.a. substitution, found in mu16D2, was different from that found in another mutant selected with the same MAb (16D2). Although MAb 11E10 immunoprecipitated G2 protein, a deduced a.a. substitution was located in the G1 region. These results suggest that antigenic sites defined by neutralizing MAbs are composed of discontinuous epitopes over the G1 and G2 proteins. Mutant 11E10 showed a significant decrease in virulence in suckling mice. A virulence revertant of mu11E10, selected through passages in suckling mice brain, showed exactly the same deduced a.a. sequence as mu11E10 and still was not neutralized by MAb 11E10. Since mutant 16D2 was virulent for suckling mice, neutralization related epitopes found with MAbs 11E10 and 16D2 were independent of pathogenicity in BALB/c mice.

Tolerance to the anti-metastatic effect of lipopolysaccharide against liver metastasis in mice

We describe the involvement of endotoxin tolerance in the refractoriness of its anti‐metastatic effect against murine syngeneic tumors. Three i.v. administrations of LPS at intervals of 4 days after tumor inoculation inhibited liver metastasis of L5178Y‐ML25 cells, whereas 3 consecutive i.v. administrations of LPS showed only a slight suppressive effect. Multiple i.v. administrations of LPS, synthetic lipid A, its synthetic derivative DT‐5461, Staphylococcus aureus (S. aureus) BioParticles or Staphylococcal enterotoxin B (SEB) on days 1, 5 and 9 after tumor inoculation inhibited liver metastasis of T‐lymphoma cells in normal mice. The anti‐metastatic effects of LPS, synthetic lipid A or DT‐5461 but not S. aureus BioParticles or SEB were diminished in mice injected with LPS at daily intervals for 7 days before tumor inoculation. Mice receiving 3 consecutive i.v. administrations of LPS at daily intervals exhibited suppression of LPS‐induced production of endogenous tumor necrosis factor‐α (TNF‐α), tumoricidal activity of macrophages, and natural‐killer (NK) activity of splenocytes when compared with those of normal mice. Macrophages from mice receiving consecutive daily i.v. administrations of LPS for 3 days showed reduction of LPS‐induced tyrosine phosphorylation of several intracellular proteins, including p42mapk/ERK2 when compared with that of the cells obtained from normal mice. These data suggest that the LPS‐induced anergic state of monocytes/macrophages plays a crucial role in endotoxin tolerance with respect to the metastasis of T lymphoma in the liver.

Effect of MDP-Lys(L18), a derivative of MDP, on enhancing host resistance against Hantaan virus infection in newborn mice

We examined the effect of MDP-Lys(L18), a lipophilic derivative of muramyl dipeptide, on the enhancement of host resistance against virus infection in newborn mice. Newborn mice were inoculated with 4 LD50/mouse of Hantaan virus strain 76-118 (HTN) one day after birth. Mice given 100 micrograms/mouse of MDP-Lys(L18) before infection exhibited significantly higher survival rates than those of non-treated mice. The effect of MDP-Lys(L18) was also restorative when given to the mice 4 or 7 days after infection. The titers of virus isolated from the lungs and spleens 12 days after infection, were about 30-times lower in MDP-Lys(L18)-treated (lung: 1.0 x 10(3) FFU; spleen: 6.8 x 10(1) FFU/mouse), than those of non-treated mice (lung: 3.4 x 10(4) FFU; spleen: 1.9 x 10(3) FFU/mouse). Furthermore, the virus was undetectable in the brains of MDP-Lys(L18)-treated mice, whereas viruses were isolated from 3 of 6 non-treated mice. MDP-Lys(L18) augmented the number of peripheral leukocytes and splenocytes, as well as mitogenic responses of the cells from bone marrow and spleen of newborn mice. These results suggest that MDP-Lys(L18) enhanced the resistance of newborn mice against HTN virus in a systemic infection model, and that this mechanism is involved in the enhancement of hematopoiesis and responsiveness of immune-related cells to mitogens.

Terminal Diols as Efficient Substrates for Transglycosylational Activity of NAD Glycohydrolase

Linear terminal alkane-diols have been shown to function as more efficient substrates of the transglycosylational activity of NAD+ glycohydrolase (NADase) than the corresponding respective 1-alkanols. A series of eight alkane-diols from ethane-1,2- to nonane-1,9-diols underwent an O-ADP-ribosylation in the incubation reaction with NAD/NADase to provide the corresponding ribosylated products. The structural properties of these products were characterized by 1H NMR and MS spectrometries. No substantial double ADP-ribosylation of the two hydroxy functions was observed which was initially expected in the diols of higher carbon number.