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Abstract

Objective

Baculovirus-expressed transmissible gastroenteritis virus (TGEV) spike (S) glycoprotein vaccines were inoculated parenterally in swine to determine whether such vaccines could induce serum and whey virus-neutralizing (VN) antibodies and protective lactogenic immunity for TGEV-challenge-exposed pigs.

Animals and Procedures

3 recombinant baculoviruses that expressed full or partial length TGEV Miller strain S glycoproteins were inoculated SC in 17 conventionally raised 11-day-old TGEV-seronegative pigs to determine whether the recombinant S glycoproteins would elicit serum VN antibodies. Eleven TGEV-seronegative pregnant sows were inoculated SC or intramammarily with subunit vaccines (R2-2 or R3-5) or control proteins. Pigs born to 9 of the 11 sows were challenge exposed at 4 to 5 days of age with the virulent Miller strain, and passive immunity was assessed. Serum and whey antibody responses to TGEV were analyzed by VN and ELISA testing.

Results

Recombinant S glycoproteins (R2-2 or R3-5) containing the 4 major antigenic sites induced similar VN antibody titers to TGEV in serum and colostrum, but low (some sows) or no VN antibody titer was detected in milk. Subcutaneous inoculation of sows with R2-2 or R3-5 elicited IgG, but not IgA antibodies to TGEV in colostrum. Morbidity was 100%, and mortality ranged from 20 to 80% in TGEV challenge-exposed pigs nursing sows inoculated SC or intramammarily with TGEV S glycoprotein vaccines.

Conclusions and Clinical Relevance

Parenterally administered TGEV S glycoprotein vaccines elicit VN antibodies to TGEV in serum and colostrum that do not fully provide active or passive immunity in swine. (Am J Vet Res 1997;58:242–250)

Free access
in American Journal of Veterinary Research

Abstract

Passive protection provided by sows inoculated with the virulent Miller strain of transmissible gastroenteritis virus (tgev), or the isu-1 strain of porcine respiratory coronavirus (prcv), or both was evaluated in nursing pigs challenge exposed with virulent tgev. Four sows (group B) were inoculated with prcv oro- nasally twice at 4 and 2 weeks before parturition; 1 sow (group C) was inoculated similarly, but in 2 subsequent pregnancies; and 2 sows (group D) were oronasally primed with prcv at 4 weeks before parturition, and 2 weeks later were administered a booster inoculation of virulent tgev. Two additional sows (group E) remained uninoculated and served as seronegative controls, and 1 sow (group A) that had been naturally infected with tgev served as a seropositive control. The degree of passive immunity transferred by these sows to their litters was assessed by challenge exposing the pigs of sows in groups BE (only the second litter of group C) with virulent tgev at 3 to 5 days of age. After challenge exposure, clinical signs of infection and mortality were noted and fecal and nasal shedding of virus was assessed by EUSA. The IgA, IgG, and IgM antibody titers to tgev were quantified in colostrum and milk of the sows by use of an isotype-specific monoclonal antibody-capture ELISA, using biotinylated monoclonal antibodies against each porcine isotype as detecting reagents. A plaque-reduction assay was used to quantify neutralizing antibody titers in serum, colostrum, milk, and fractionated whey (IgG and IgA/ IgM). In the sow naturally infected with tgev (group A), there was a pronounced decrease in IgG antibody titers to tgev in the transition from colostrum to milk, and IgA tgev antibodies became predominant, with high titers maintained throughout lactation. The 4 group-B sows partially protected their pigs after tgev challenge exposure; mean mortality was 67%, compared with 100% in pigs suckling the 2 tgev seronegative control sows (group-E fitters). Although IgA tgev antibodies were detected in colostrum and milk of group-B sows, IgG tgev antibodies were the most abundant. The sow of group C had a marked increase in IgA tgev antibody titers in colostrum and milk after reinoculation with prcv during the second pregnancy, before tgev challenge exposure of the fitter. Its pigs were passively protected to a high degree after tgev challenge exposure (27% litter mortality). The sows in group D, primed with prcv and boosted with tgev, provided the best passive protection after tgev challenge exposure of their pigs. Not only fitter mortality (27%) but also morbidity was reduced, compared with those factors for the other challenge- exposed fitters, and the sows did not become ill. In these swine, the high degree of passive protection observed could not be associated with the presence of only IgA tgev antibodies in the milk, but high IgM tgev antibody titers also were detected in colostrum and milk. Results of this study suggest that prcv- inoculated sows are able to partially protect their pigs from tgev challenge exposure and, on the basis of preliminary data, the degree of protection may increase after multiple prcv exposures or after secondary exposure to tgev during pregnancy. Also, an IgA respiratory tract-mammary gland link may exist as evident by the low titer of IgA tgev antibodies in the milk of prcv-inoculated sows, but may not be as efficient in inducing lactogenic IgA immunity as is the gastrointestinal tract-mammary gland link.

Free access
in American Journal of Veterinary Research

Abstract

Objective

To compare recombinant transmissible gastroenteritis virus (TGEV) spike protein, (SP) R2-2, with attenuated live virus (ALV) vaccine in sows during late pregnancy.

Animals

13 TGEV-seronegative sows and their pigs.

Procedure

At prepartum weeks (PPW) 6 and 4, sows of groups 1 and 2 received ALV via the oral/intranasal (O/IN) route. At PPW 2, group-1 sows received ALV IM and group-2 sows received SPR2-2 IM. Group-3 sows received SPR2-2 IM at PPW 4 and ALV O/IN at PPW 2. Sows of group 4 (negative controls) were inoculated O/IN with mock-infected ST cell fluids at PPW 6 and 4 and IM with Sf9 cell lysates at PPW2 (n = 2), or IM with Sf9 cell lysates at PPW4 and O/IN with mock-infected ST cell fluids at PPW2 (2). Serum, colostrum, and milk samples were tested for antibody to TGEV, and a lymphoproliferative (LP) assay was done on blood mononuclear cells. Suckling pigs were challenge exposed with virulent TGEV.

Results

Sows of groups 1 and 2 had higher IgG and significantly higher antibody titers in colostrum; their pigs had significantly higher serum antibody titer. At challenge exposure of their pigs, LP responses of group-2 sows were significantly higher than those of sows in the other 3 groups. Mean pig mortality ranged from 43 (group 2) to 92% (group 4). Significant negative correlations were observed among litter mortality and sow LP response, colostral titer, and pig serum titer at time of challenge exposure.

Conclusions

In sows vaccinated twice with attenuated live TGEV, the recombinant SPR2-2 administered IM may be comparable to ALV administered IM as a booster. Vaccination failed to provide complete protection to suckling pigs after challenge exposure. (Am J Vet Res 1998;59:1002–1008)

Free access
in American Journal of Veterinary Research