Acrylamide concentration affects the relative position of VP7 gene of serotype G2 strains as determined by polyacrylamide gel electrophoresis

Molecular and biological characterization of the human-bovine rotavirus-based reassortant rotavirus

Rotaviruses (RV) are the leading cause of acute infantile gastroenteritis, associated with elevated mortality in low-income countries. Morbidity and mortality, length and rates of hospitalization due to RV gastroenteritis are dropping. Improving the quality of newborns life is an ongoing challenge for health-care providers. In this study, homemade reassortant human-bovine rotavirus was developed and biological activity and molecular characterization of candidate vaccine were evaluated for the vaccine stability. Virus titration and purification of reassortant rotavirus strains were evaluated by plaque assays, electropherotyping. The genetic stability after first, third and sixth passage was by sequencing. Due to WHO recommendation, developingment of national capacity for vaccine production in appropriate quantities and at affordable prices is the cornerstone of developing global vaccination policies. Such studies are critical to producing national vaccines and modeling herd protection.

Distribution of rotavirus VP7 and VP4 genotypes circulating in Tunisia from 2009 to 2014: Emergence of the genotype G12

Group A rotavirus (RVA) represents the most important aetiological agent of diarrhoea in children worldwide. From January 2009 to December 2014, a multi-centre study realized through 11 Tunisian cities was undertaken among children aged <5 years consulting or hospitalized for acute gastroenteritis. A total of 1127 faecal samples were collected. All samples were screened by ELISA for the presence of RVA antigen. RVA-positive samples were further analyzed by PAGE and used for G/P-genotyping by semi-nested multiplex RT-PCR. Globally, 270 specimens (24 %) were RVA-positive, with peaks observed annually between November and March. Nine different electropherotypes could be visualized by PAGE, six with a long profile (173 cases) and two with a short one (seven cases). Mixed profiles were detected in two cases. Among the 267 VP7 genotyped strains, the predominant G- genotype was G1 (39.6 %) followed by G3 (22.2 %), G4 (13 %), G9 (11.5 %), G2 (5.2 %) and G12 (5.2 %). Among the 260 VP4 genotyped strains, P[8] genotype was the predominant (74.5 %) followed by P[6] (10.4 %) and P[4] (5.5 %). A total of 257 strains (95.2 %) could be successfully G- and P-genotyped. G1P[8] was the most prevalent combination (34.4 %), followed by G3P[8] (16.3 %), G9P[8] (10.3 %), G4P[8] (8.9 %), G2P[4] (4 %), G12P[6] (2.6 %) and G12P[8] (1.9 %). Uncommon G/Pgenotype combinations, mixed infections and untypeable strains were also detected. This is the first report, in Tunisia, of multiple detection of an emerging human RVA strain, G12 genotype. This study highlighted the need for maintaining active surveillance of emerging strains in Northern Africa.

Dual selection mechanisms drive efficient single-gene reverse genetics for rotavirus

Current methods for engineering the segmented double-stranded RNA genome of rotavirus (RV) are limited by inefficient recovery of the recombinant virus. In an effort to expand the utility of RV reverse genetics, we developed a method to recover recombinant viruses in which independent selection strategies are used to engineer single-gene replacements. We coupled a mutant SA11 RV encoding a temperature-sensitive (ts) defect in the NSP2 protein with RNAi-mediated degradation of NSP2 mRNAs to isolate a virus containing a single recombinant gene that evades both selection mechanisms. Recovery is rapid and simple; after two rounds of selective passage the recombinant virus reaches titers of ≥10(4) pfu/mL. We used this reverse genetics method to generate a panel of viruses with chimeric NSP2 genes. For one of the chimeric viruses, the introduced NSP2 sequence was obtained from a pathogenic, noncultivated human RV isolate, demonstrating that this reverse genetics system can be used to study the molecular biology of circulating RVs. Combining characterized RV ts mutants and validated siRNA targets should permit the extension of this "two-hit" reverse genetics methodology to other RV genes. Furthermore, application of a dual selection strategy to previously reported reverse genetics methods for RV may enhance the efficiency of recombinant virus recovery.

Concentration of acrylamide in a polyacrylamide gel affects VP4 gene coding assignment of group A equine rotavirus strains with P[12] specificity

BACKGROUND

It is universally acknowledged that genome segment 4 of group A rotavirus, the major etiologic agent of severe diarrhea in infants and neonatal farm animals, encodes outer capsid neutralization and protective antigen VP4.

RESULTS

To determine which genome segment of three group A equine rotavirus strains (H-2, FI-14 and FI-23) with P[12] specificity encodes the VP4, we analyzed dsRNAs of strains H-2, FI-14 and FI-23 as well as their reassortants by polyacrylamide gel electrophoresis (PAGE) at varying concentrations of acrylamide. The relative position of the VP4 gene of the three equine P[12] strains varied (either genome segment 3 or 4) depending upon the concentration of acrylamide. The VP4 gene bearing P[3], P[4], P[6], P[7], P[8] or P[18] specificity did not exhibit this phenomenon when the PAGE running conditions were varied.

CONCLUSIONS

The concentration of acrylamide in a PAGE gel affected VP4 gene coding assignment of equine rotavirus strains bearing P[12] specificity.