A lymphatic mechanism of rotavirus extraintestinal spread in the neonatal mouse

Abstract

We used the neonatal mouse model of rotavirus infection and virus strains SA11-clone 4 (SA11-Cl4) and Rhesus rotavirus (RRV) to examine the mechanism of the extraintestinal spread of viruses following oral inoculation. The spread-competent viruses, RRV and reassortant R7, demonstrated a temporal progression from the intestine, to the terminal ileum, to the mesenteric lymph nodes (MLN), and to the peripheral tissues. SA11-Cl4 was not found outside the intestine. Reassortant virus S7, which was unable to reach the liver in previous studies (E. C. Mossel and R. F. Ramig, J. Virol. 76:6502-6509, 2002), was recovered from 60% of the MLN, suggesting that there are multiple determinants for the spread of virus from the intestine to the MLN. Phenotypic segregation analysis identified RRV genome segment 6 (VP6) as a secondary determinant of the spread of virus to the MLN (P = 0.02) in reassortant viruses containing segment 7 from the spread-incompetent parent. These data suggest that in the orally infected neonatal mouse, the extraintestinal spread of rotavirus occurs via a lymphatic pathway, and the spread phenotype is primarily determined by NSP3 and can be modified by VP6.

FIG. 1.

Virus titers in various tissues following oral inoculation of neonatal mice with (A) RRV, (B) SA11-Cl4, (C) R7, or (D) S7. Five-day-old mice were orally inoculated with 2 × 10⁶ PFU of rotavirus. At the postinoculation times indicated, animals were sacrificed, tissues were harvested, and virus titers were determined by plaque assay. Values indicate mean titers of virus-positive samples. Error bars indicate standard deviations. Gut, large and small intestine less a 2-cm section of terminal ileum; PP, 2-cm section of Peyer's patch-rich terminal ileum. Results for RRV and SA11-Cl4 at 6 hpi and for R7 and S7 are from 5 to 6 animals. Results for RRV and SA11-Cl4 at 12 to 72 hpi are from 9 to 11 animals.

FIG. 2.

Frequency of virus recovery in various tissues following oral inoculation of neonatal mice with (A) RRV, (B) SA11-Cl4, (C) R7, or (D) S7. Five-day-old mice were orally inoculated with 2 × 10⁶ PFU of rotavirus. At the postinoculation times indicated, animals were sacrificed, tissues were harvested, and virus presence was determined by plaque assay. Gut = large and small intestine less 2 cm section of terminal ileum; PP = 2 cm section of Peyer's patch-rich terminal ileum; MLN = mesenteric lymph nodes. Results for RRV and SA11-Cl4 at 6 hpi and for R7 and S7 are from 5 to 6 animals. Results for RRV and SA11-Cl4 at 12 to 72 hpi are from 9 to 11 animals.