In vitro Concanavalin A and rotavirus-specific proliferation of spleen cells. Part 2
Statistical analysis
Power calculation indicated a group size of at least 13 animals to find significant differences in diarrheal score (detectable difference in diarrheal score = 20%, expected CV = 15%, α = 0.05, β = 0.20). All statistical analyses were performed using the statistical software package GraphPad Prism, version 4.03. A two-sample t test was used when two groups were compared. Values of P less than 0.05 were considered significant.
Results
Diarrhea and severity of illness score of RRV infected pups
Diarrhea and severity of illness was monitored daily during the first RRV infection from day 8 (1 day p.i.) until day 14 of age. Diarrhea in mice inoculated with RRV (group A and C combined) appeared at day 9 with 63% of the pups having symptoms of diarrhea, rising to a maximum of 70% at day 10 and declining to zero at day 13. When the mice were supplemented with rotavirus-specific antibodies (Gastrogard-R®) orally (group D) prior and during the RRV infection, no signs of diarrhea occurred indicating a complete protection against RRV induced diarrhea.
A high score indicates severe illness, minimum score is 2 (18.2%) and maximum score is 11 (100%). Illness in mice inoculated with RRV (group A and C combined) appeared at day 9 with an average severity score of 38.6%, reaching a maximum of 52.3% at day 10 and declining after day 11. Mice supplemented with Gastrogard-R® orally prior and during the RRV infection showed no signs of illness.
Viral shedding of RRV in feces
Viral shedding in the feces was detected by measuring the amount of virus antigen shed after the RRV inoculation at day 7. Rotavirus in the feces after RRV inoculation was detectable but in low levels (between 15-130 ng/ml) during RRV infection (group A and C), but no rotavirus was detected in the Gastrogard-R® group (group D) (data not shown).
Viral shedding of EDIM in feces
Viral shedding in the feces was detected by measuring the amount of virus antigen shed after the EDIM inoculation at day 17. The results of the viral shedding after the EDIM inoculation are depicted in Figure 3. A primary infection with RRV decreased viral shedding by 81% during a secondary infection with EDIM (Figure 3B) compared to infection with EDIM alone. Similar findings have previously been described with heterologous rotavirus infection in mice. Intervention with Gastrogard-R® had 100% protected the mice against RRV induced diarrhea, but viral shedding during the secondary infection with EDIM showed no significant difference compared to the EDIM alone group. However, in the EDIM group, shedding of rotavirus was measured up until day 27, whereas in the Gastrogard-R® group, no rotavirus was detected in the feces after day 24. This might indicate that passive protection against a primary illness does not protect against viral shedding during a secondary infection, though clearing of rotavirus seemed more rapid in the Gastrogard-R® group than in mice inoculated with EDIM alone.