SURVIVAL OF ORALLY ADMINISTERED ANTIROTAVIRUS ANTIBODIES IN HUMAN GASTROINTESTINAL TRACT

Pacyna, J., Roberton, ES., Terry, S., Whyte, PBD., Davidson, GP. and Johnson, RB.
Northfield Laboratories Pty Ltd, Adelaide, South Australia 5086

INTRODUCTION:  Rotavirus is a major cause of acute gastroenteritis in infants and young children worldwide.  Passive immunisation with hyperimmune bovine colostrum (HBC-R) containing rotavirus antibody is one way to prevent rotavirus infections.  In this study, the survival of rotavirus antibody activity in faeces of children receiving different doses of HBC-R was investigated.

METHODOLOGY:  Hyperimmune colostrum containing different levels of rotavirus antibody was administered to 105 children attending nine Adelaide childcare centres.  There were five experimental groups in the study.  Subjects were asked to drink 100ml of whole milk supplemented with colostrum 3 times a day, for a period of 6 days.  Three groups received specific amounts of HBC-R in a liquid form, one group received a reconstituted powder form of Gastrogard-R_®, and the control group received whole cow's milk.  Stool samples were tested for the presence of rotavirus antigen or antibodies.  Rotavirus activity was determined using a virus reduction and a virus neutralisation assay.

RESULTS:  Rotavirus antibody activity was detected in 521 (86%) of 602 faecal specimens obtained during the study using the virus reduction ELISA.  The antibody activity was detected as early as 8 hrs after ingestion of hyperimmune colostrum and up to 72 hrs after consumption had ceased (figure 1).

Figure 1.
Percentage faecal extract was detected rotavirus antibody after receiving HBC-R.

There was a strong and positive relationship (r = 0.81) between the levels of antibody activity in faeces and the dose of HBC-R ingested. (figure 2).

Figure 2.
Relationship between the amounts of rotavirus antibody administered to subjects in all five groups and the percent reduction of antibody activity excreted in the faeces.

The relationship between the percent reduction of rotavirus by ELISA and the percent of rotavirus neutralisation, using faecal extracts of subjects taking HBC-R, was also investigated. (figure 3).

Figure 3.
Relationship between the rotavirus percent reduction and the rotavirus percent neutralisation by faecal extracts with rotavirus antibody activity.

The results of the two assays correlated strongly (r = 0.96) and were of high functional dependence (R2 = 0.92) and significance (p = 0.004), providing evidence for the rotavirus neutralizing capacity of the faecal extracts.

CONCLUSION:  The results show that approximately 5% of relative rotavirus antibody activity had survived passage through the gut (mean activity, 4 groups, 602 samples).  Therefore, passive immunotherapy may be used to prevent or treat infectious diseases that affect the entire length of the gastrointestinal tract.  Furthermore, it is likely that antibody activity in the small intestine (where most viral and bacterial infections have their major impact) will be considerably higher than the activity in the faeces, thus providing even greater protection and/or treatment against gastrointestinal diseases.