Identification of 3 neutralizing linear epitopes on the VP8 outer capsid protein of group A equine rotavirus.

OBJECTIVE: To identify protective equine rotavirus group A (ERVA) VP8 epitopes and demonstrate that immunizing hens with synthetic peptides based on these epitopes would yield high-titered, neutralizing egg yolk antibodies for potential application in foals. ANIMALS: 26 rotavirus-positive, client-owned foals were included in the study. Five white leghorn hens were used for antibody production. METHODS: Chicken antibodies were raised against 3 synthetic epitope peptides from the VP8 protein of the common ERVA P-type, P4[12] using CD40-targeted streptavidin-peptide complexes. Antipeptide serum- and egg yolk antibodies were subject to ELISA and in vitro virus neutralization assays to evaluate binding and neutralization activities. Lyophilized anti-VP8 egg yolk antibodies were orally administered (30 g; q 24 h for 5 days) to foals with rotaviral diarrhea. Physical examinations were performed daily. The duration of diarrhea and any adverse effects were recorded. RESULTS: CD40-targeted vaccination of hens generated high titers of anti-VP8 serum and egg yolk antibodies after just 3 immunizations. These antibodies prevented in vitro infection of ERVA with titers of 128 in the serum and 94.5 in the yolk. Oral administration (30 g; q 24 h for 5 days) of lyophilized hyperimmune egg yolk to foals with rotaviral diarrhea did not reveal any adverse effects of the treatment. CLINICAL RELEVANCE: This study demonstrated that antibodies raised against neutralizing epitopes of the ERVA VP8 protein could prevent ERVA infection in vitro. Based on these results and previous work in other animals, in vivo evaluation of the therapeutic efficacy of anti-VP8 egg yolk antibodies is warranted.

Randomized, controlled trial comparing Rhodococcus equi and poly-N-acetyl glucosamine hyperimmune plasma to prevent R equi pneumonia in foals.

BACKGROUND: Hyperimmune plasma raised against ß-1→6-poly-N-acetyl glucosamine (PNAG HIP) mediates more opsonophagocytic killing of Rhodococcus equi (R equi) than does R equi hyperimmune plasma (RE HIP) in vitro. The relative efficacy of PNAG HIP and RE HIP to protect foals against R equi pneumonia, however, has not been evaluated. HYPOTHESIS: Transfusion with PNAG HIP will be superior to RE HIP in foals for protection against R equi pneumonia in a randomized, controlled, blinded clinical trial. ANIMALS: Four hundred sixty Quarter Horse and Thoroughbred foals at 5 large breeding farms in the United States. METHODS: A randomized, controlled, blinded clinical trial was conducted in which foals were transfused within 24 hours after birth with 2 L of either RE HIP or PNAG HIP. Study foals were monitored through weaning for clinical signs of pneumonia by farm veterinarians. The primary outcome was the proportion of foals that developed pneumonia after receiving each type of plasma. RESULTS: The proportion of foals that developed pneumonia was the same between foals transfused with RE HIP (14%; 32/228) and PNAG HIP (14%; 30/215). CONCLUSIONS AND CLINICAL IMPORTANCE: Results indicate that PNAG HIP was not superior to a commercially available, United States Department of Agriculture-licensed RE HIP product for protecting foals against R equi pneumonia under field conditions.