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Rotavirus genome segment 7 (NSP3) is a determinant of extraintestinal spread in the neonatal mouse
Eric C Mossel1, Robert F Ramig
1Department of Molecular Virology and Microbiology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
Insights
Rotavirus extraintestinal spread was studied in neonatal mice. Rhesus rotavirus (RRV) genome segment 7, encoding NSP3, was crucial for gut growth and spread to peripheral sites.
Area of Science:
- Virology
- Infectious Diseases
- Molecular Biology
Background:
- Rotavirus infections are a major cause of gastroenteritis in infants worldwide.
- Understanding the mechanisms of rotavirus spread is crucial for developing effective interventions.
- Extraintestinal dissemination of rotavirus is not well understood.
Purpose of the Study:
- To investigate the factors influencing extraintestinal spread of rotavirus following oral inoculation in a neonatal mouse model.
- To identify specific rotavirus genome segments responsible for extraintestinal tropism.
- To elucidate the role of viral proteins in rotavirus dissemination.
Main Methods:
- Neonatal mice were orally inoculated with different rotavirus strains (SA11-Cl3, SA11-Cl4, SA11-4F, RRV, B223).
- Virus detection in the liver was used as a proxy for extraintestinal spread.
- Reassortant viruses were generated to map the genetic determinants of spread.
- Intraperitoneal and subcutaneous inoculations were performed to assess barriers to spread.
- Sequence analysis of rotavirus genome segment 7 was conducted.
Main Results:
- Rotavirus strains varied in their ability to spread extraintestinally, with rhesus rotavirus (RRV) showing high frequency spread and SA11-Cl4 showing very low frequency.
- Extraintestinal spread phenotype and gut growth segregated with rotavirus genome segment 7.
- Gut infection was necessary for liver tropism, but gut viral titers did not correlate with liver detection.
- The gut and peripheral inoculation sites presented barriers to rotavirus spread, similar to the gut.
- Sequence analysis indicated that amino acid differences in segment 7 were distributed throughout, and parental sequences were maintained in reassortants.
Conclusions:
- Rotavirus non-structural protein 3 (NSP3), encoded by genome segment 7, plays a significant role in viral growth within the gut and subsequent spread to peripheral sites.
- Genome segment 7 is a key determinant of rotavirus extraintestinal tropism.
- Further investigation into the mechanism of NSP3-mediated tropism is warranted.
Abstract:
We used the neonatal mouse model of rotavirus infection to study extraintestinal spread following oral inoculation. Five-day-old pups were inoculated with either SA11-Cl3, SA11-Cl4, SA11-4F, RRV, or B223. By using virus detection in the liver as a proxy determination for extraintestinal spread, rotavirus strains capable of extraintestinal spread at high frequency (rhesus rotavirus [RRV]) and very low frequency (SA11-Cl4) were identified. Both strains productively infected the gastrointestinal tract. Oral inoculation of mice with RRV/ SA11-Cl4 reassortants and determination of virus titers in the gut and liver revealed that the extraintestinal spread phenotype segregated with RRV genome segment 7 to a high level of significance (P = 10(-3)). RRV segment 7 also segregated with the growth of virus in the gut (P = 10(-5)). Although infection of the gut was clearly required for tropism to the liver, there was no correlation between virus titers in the gut and detection of virus in the liver. Five days after intraperitoneal administration to bypass the gut barrier to virus spread, RRV and SA11-Cl4 both were recovered in the liver. However, only RRV was found in the liver following subcutaneous inoculation, suggesting that this peripheral site presented a similar barrier to virus spread as the gut. Sequence analysis of segment 7 from parental RRV and SA11-Cl4 and selected reassortants showed that (i) amino acid differences were distributed throughout the coding sequences and not concentrated in any particular functional motif and (ii) parental sequence was preserved in reassortants. These data support the hypothesis that NSP3, coded for by genome segment 7, plays a significant role in viral growth in the gut and spread to peripheral sites. The mechanism of NSP3-mediated tropism is under investigation.