Protective efficacy of a sulfated sialyl lipid (NMSO3) against human rotavirus-induced diarrhea in a mouse model

Abstract

Antiviral activity of sulfated sialyl lipid (NMSO3) against human rotavirus (RV) was examined in vitro and in vivo. NMSO3 inhibited the replication of four major serotypes (G1 to G4) of human rotavirus with a low 50% effective concentration of 1 to 5 microg/ml and 50% cytotoxic concentration of 153 microg/ml when determined by plaque assays with MA104 cells. Exposure of NMSO3 to HCl (pH 2.0) for 30 min exhibited no loss of anti-RV activity. Time-of-addition experiments revealed that NMSO3 inhibited the adsorption of four serotypes of RV to MA104 cells. Furthermore, an assay of virus binding with radiolabeled RVs revealed that NMSO3 inhibited the binding of virus to MA104 cells, suggesting that NMSO3 may bind to VP4 and/or VP7. Prophylactic oral administration of NMSO3 (10 microg three times per day, 4 days) to five suckling mice starting 30 min before inoculation of MO strain (3 x 10(6) PFU/mouse) prevented the development of diarrhea. Four of five mice showed no stool or brown formed stool, and only one mouse showed brown soft stool, while water treatment caused watery diarrhea in all five mice. The mean titer of antibody to RV in mice which received NMSO3 at 10 microg three times per day for 4 days was significantly lower than that of untreated, infected mice. NMSO3 is a promising candidate for the prophylactic treatment of human RVs.

FIG. 1.

Chemical structure of NMSO3, sodium [2,2-bis(docosyl-oxymethyl)propyl-5-acetoamido-3,5-dideoxyl-4,7,8,9-tetra-O-(sodium-oxy sulfonyl)-d-glycero-d-galacto-2-nonulopyranosid]onate. M. W.,molecular weight.

FIG. 2.

Effect of NMSO3 on binding of the Wa strain to MA104 cells. Triplicate cultures of MA104 cells were incubated with ³⁵S-labeled Wa strain in various concentrations of NMSO3. Data represent mean percentages (± standard deviations) of membrane-bound virus.

FIG. 3.

Protective effect of NMSO3 on HRV-induced diarrhea in suckling mice. Litters of 7-day-old mice were given orally either water (A) or 50 (B), 10 (C), 2 (D), or 0.4 (E) μg of NMSO3 three times a day for 4 days starting 30 min before virus inoculation with 3 × 10⁶ PFU (MO strain)/mouse. A six-point rating system was used to characterize diarrhea: 1, no stool; 2, brown formed stool; 3, soft brown stool; 4, soft-mucous brown-yellow stool; 5, muddy-mucous yellow stool; 6, liquid yellow stool.

FIG. 4.

Effect of NMSO3 on HRV-induced diarrhea in suckling mice. Seven-day-old mice were given orally either water (A) or 10 μg of NMSO3 (B) three times a day for 4 days starting 30 min before virus inoculation with 3 × 10⁶ PFU (MO strain)/mouse. Stool was inspected 2 days after virus inoculation.