Dietary supplementation of beta-glucan-rich molasses yeast powder on antibody response to swine fever virus and hematology of starter-grower pigs.

This research investigated the impact of dietary beta-glucan-rich molasses yeast powder (MYP) supplementation on the antibody response to swine fever virus (Titer) and hematology of starter-grower pig. Sixteen cross pigs (30 kg body weight) were equally split into four groups; each group with four replicates and fed four dietary treatments that consisted of basal diets (control) and the basal diets added with 2.5, 5.0, and 7.5% MYP. Feed and water were consumed ad libitum for 44 days. Feed intake (FI), MYP intake (MYPI), beta-glucan intake (BGI), and Mannan-oligosaccharide intake (MOSI) were recorded daily. Titer was evaluated after 15 (Titer15) and 30 (Titer30) days after vaccination, while hematology was analyzed at the end of the experiment. The results indicated that it was unchangeable for ADFI (P > 0.05). No impacts were observed on hematological variables and Titer15 in MYP fed pigs (P > 0.05). However, supplementation with 7.5% MYP increased platelet count (PC) and Titer30 (P < 0.01), but decreased hematocrit (Hct) (P < 0.05). Titer 30 and titer 15 were linked to MYPI, BGI, and MOSI (P < 0.05). Based on the study, feeding starter-grower pigs diets supplemented with 7.5% MYP might enhance the antibody response to swine fever virus 30 days after vaccination, and it has a potential role in the application in prevention of swine fever virus disease.

Dietary Supplementation of Astragalus Polysaccharides Enhanced Immune Components and Growth Factors EGF and IGF-1 in Sow Colostrum.

Colostrum is the main external resource providing piglets with nutrients and maternal immune molecules. Astragalus polysaccharides (APS) have been used as immunopotentiators in vitro and several animal models. This study aimed to determine the effects of APS on immune factors in sow colostrum and milk. The sow diet was supplemented with APS one week before the expected delivery date. Colostrum and milk were collected and designated as 0 h- (onset of parturition), 12 h-, and 24 h-colostrum and 36 h-milk postpartum. Samples were measured using porcine immunoglobulin (Ig) G, IgM, classical swine fever virus antibody (CSFV Ab), epidermal growth factor (EGF), and insulin-like growth factor- (IGF-) 1 ELISA Quantitation Kits. Dietary supplementation of APS significantly enhanced the presence of IgG, IgM, EGF, and IGF-1 in 0 h-colostrum (P < 0.001). The blocking rates of CSFV Ab were increased in samples from APS-supplemented sow when compared to those from the matched samples without APS treatment. The results indicate that supplement of APS could improve the immune components in sow colostrum and/or milk; and status of some specific vaccination could be determined through using colostrum or early milk in sow.

Glycoprotein E2 of classical swine fever virus expressed by baculovirus induces the protective immune responses in rabbits.

Classical swine fever (CSF) caused by CSF virus (CSFV) is a highly contagious and devastating disease that affects the pig industry worldwide. The glycoprotein E2 of CSFV is the principal immunogenic protein that induces neutralizing antibodies and protective immunity. Several CSFV genotypes, including 1.1, 2.1, 2.2, and 2.3, have been identified in Mainland China. The glycoprotein E2 of genotypes 1.1 and 2.1 was expressed by using a baculovirus system and tested for its protective immunity in rabbits to develop novel CSF vaccines that elicit a broad immune response. Twenty CSFV seronegative rabbits were randomly divided into five groups. Each rabbit was intramuscularly immunized with E2 of genotypes 1.1 (CSFV-1.1E2), 2.1 (CSFV-2.1E2), or their combination (CSFV-1.1 + 2.1E2). A commercial CSF vaccine (C-strain) and phosphate-buffered saline (PBS) were used as positive or negative controls, respectively. All animals were challenged with CSFV C-strain at 4 weeks and then boosted with the same dose. All rabbits inoculated with CSFV-1.1E2, CSFV-2.1E2, and CSFV-1.1 + 2.1E2 elicited high levels of ELISA antibody, neutralizing antibody, and lymphocyte proliferative responses to CSFV. The rabbits inoculated with CSFV-1.1E2 and CSFV-1.1 + 2.1E2 received complete protection against CSFV C-strain. Two of the four rabbits vaccinated with CSFV-2.1E2 were completely protected. These results demonstrate that CSFV-1.1E2 and CSFV-1.1 + 2.1E2 not only elicit humoral and cell-mediated immune responses but also confer complete protection against CSFV C-strain in rabbits. Therefore, CSFV-1.1E2 and CSFV-1.1 + 2.1E2 are promising candidate subunit vaccines against CSF.

Generation of a recombinant classical swine fever virus stably expressing the firefly luciferase gene for quantitative antiviral assay.

Classical swine fever (CSF), caused by classical swine fever virus (CSFV), is a highly contagious swine disease leading to significant economic losses worldwide. Vaccines are widely used to control the disease, and no CSFV-specific antivirals are currently available. To facilitate anti-CSFV molecule discovery, we developed a reporter virus CSFV-N(pro)Fluc stably expressing the firefly luciferase (Fluc) gene in the N(pro) gene. The reporter virus enabled more sensitive and convenient detection of the N(pro) protein expression and the viral replication by luciferase reporter assay than by traditional methods. The CSFV N(pro) protein was detectable as early as 4.5h post-infection. As a proof-of-concept for its utility in rapid antiviral screening, this reporter virus was used to quantify anti-CSFV neutralizing antibodies of 50 swine sera and to assess 12 small interfering RNAs targeting different regions of the CSFV genome. The results were comparable to those obtained by traditional methods. Taken together, the reporter virus CSFV-N(pro)Fluc represents a useful tool for rapid and quantitative screening and evaluation of antivirals against CSFV.

Enhancement of peripheral blood CD8+ T cells and classical swine fever antibodies by dietary beta-1,3/1,6-glucan supplementation in weaned piglets.

The experiment was conducted to evaluate the effect of dietary supplementation with 0, 50, 100 and 200 mg/kg of beta-1,3/1,6-glucan extracted from Saccharomyces cerevisiae on cellular immune responses and classical swine fever virus (CSFV) antibody production of weaned piglets. Thirty-two (Landrace x Large White; 26 days old; 7.05+/-0.25 kg body weight) castrated male piglets were randomly allocated to four treatments, eight pigs per treatment. All piglets were vaccinated with live-attenuated Chinese strain cell vaccines at 26 days of age. The results showed that dietary supplementation with beta-1,3/1,6-glucan could significantly (P<0.01) enhance peripheral blood lymphocyte proliferation activity in weaned piglets after 14 days administration, whereas no significant effect (P>0.05) was observed on day 28. Dietary beta-1,3/1,6-glucan supplementation could significantly enhance CSFV antibody blocking rate (P<0.05) on days 14 and 21 after inoculation. Although dietary beta-1,3/1,6-glucan supplementation did not significantly influence (P>0.05) lymphocyte subgroups on day 14, high levels of beta-1,3/1,6-glucan (100 and 200 mg/kg) increased the percentage of cytotoxic/suppressor lymphocytes (CD8(+)) significantly (P<0.05), decreased the ratio of CD4(+)/CD8(+) significantly (P<0.05) and increased the percentage of total T lymphocytes (CD3(+)) on day 28. These results suggest that beta-1,3/1,6-glucan may have a beneficial effect on the immune system of swine, and dietary beta-1,3/1,6-glucan supplementation had a transient impact on lymphocyte proliferation activity. The CSFV antibody blocking rate and the percentage of peripheral blood CD8(+) T cells could be enhanced by continuous beta-1,3/1,6-glucan supplementation. These findings support the potential application of beta-1,3/1,6-glucan as a prophylactic agent in increasing animal immune functions and controlling CSF disease.

Chimeric pestiviruses: candidates for live-attenuated classical swine fever marker vaccines.

The use of attenuated classical swine fever virus (CSFV) strains as live vaccines is no longer allowed for the control of classical swine fever in Europe, due to the inability to differentiate between infected and vaccinated animals (Differentiating Infected from Vaccinated Animals; DIVA), except as emergency vaccines or as bait vaccines for wild boars. Thus, the establishment of a DIVA vaccine(s) is of pivotal importance for the control of this infectious disease. In this study, recombinant versions of the live-attenuated vaccine strain CSFV Riems were generated by replacing parts of the E2 gene with the corresponding sequence of border disease virus strain Gifhorn. Three cDNA clones were constructed: pRiems-ABC-Gif, pRiems-A-Gif and pRiems-BC-Gif. Infectious particles were obtained from clones pRiems-ABC-Gif and pRiems-BC-Gif only, whereas transfected RNA from clone pRiems-A-Gif behaved like a replicon. Based on its ability to be differentiated in vitro from wild-type CSFV by mAbs, vRiems-ABC-Gif was assessed for immunogenicity and protection against challenge infection in pigs. Before challenge, no CSFV-specific anti-E2 antibodies could be detected with commercial E2-blocking ELISAs in vRiems-ABC-Gif-vaccinated animals, whereas vRiems-vaccinated pigs developed high titres of anti-E2 antibodies, confirming the marker properties of this vaccine candidate. After oral vaccination, only partial protection against challenge infection was observed in the vRiems-ABC-Gif vaccinees, whereas all intramuscularly vaccinated animals and all vRiems-vaccinated animals were fully protected. These experiments suggest that the strategy of exchanging specific antigenic epitopes among pestiviruses is a promising tool for the development of new CSFV marker vaccines.

Adsorption of colostral antibodies against classical swine fever, persistence of maternal antibodies, and effect on response to vaccination in baby pigs.

OBJECTIVE: To determine kinetics of antibody absorption, persistence of antibody concentrations, and influence of titers on vaccination of baby pigs with a vaccine against classical swine fever (CSF). ANIMALS: 15 sows and their litters. PROCEDURE: Farrowings were supervised. Initial time of suckling was recorded. In the first experiment, blood samples were collected at farrowing, 2 and 4 hours after suckling, and hourly until 10 hours after initial suckling. Samples were assayed for CSF antibodies, using a serum neutralizing (SN) test. A second experiment included 33 baby pigs vaccinated as follows: 10 prior to ingestion of colostrum, 18 between 1 and 4 hours after ingestion of colostrum, and 5 at 12 hours after ingestion of colostrum. Fourteen pigs were vaccinated when 7 weeks old, and 15 pigs were not vaccinated. At 10 weeks of age, pigs were challenge-exposed with virulent CSF virus. Blood samples were collected and assayed for CSF antibodies and p125 antigen and p125 antibodies. RESULTS: CSF antibodies were detected in pigs beginning 2 hours after suckling. Colostral antibodies persisted for > 7 weeks (half-life, 79 days). Vaccination of pigs before suckling provided effective protection from severe disease after challenge-exposure. However, vaccination of neonates with antibody titers was not effective, because 19 of 23 (82%) pigs succumbed after challenge-exposure. All pigs vaccinated when 7 weeks old resisted challenge-exposure, whereas all unvaccinated control pigs succumbed. CONCLUSIONS AND CLINICAL RELEVANCE: Vaccination before ingestion of colostrum conferred good protection against CSF in baby pigs. Vaccination of 7-week-old pigs that had decreasing concentrations of passively acquired antibodies was efficacious.

Transient classical swine fever virus infection in wild boar piglets partially protected by maternal antibodies.

An experimental study was conducted to investigate the clinical course of classical swine fever (CSF) in wild boar piglets partially protected by maternal antibodies. Five healthy wild boar piglets with a low serum titre of colostral antibodies against CSF virus were challenged with virulent CSF virus at the age of three months. Apart of reduced food intake and diarrhoea no major clinical symptoms were noticed after challenge. These signs were seen during the second and third week of infection, afterwards the piglets recovered completely. CSF virus could be re-isolated from blood samples taken on day 12 and day 19 post challenge. From blood samples taken later on and from the organ material taken at post mortem examinations no CSF virus could be isolated anymore. It can be concluded that the presence of maternal antibodies influences the clinical course of CSF in terms that the outcome is rather transient than lethal. Such wild boar could play a crucial role in the spread of CSF virus and might contribute to the maintenance of long lasting epizootics.

Relation between lymphocyte subpopulations of peripheral blood and immune responses of modified live hog cholera virus vaccine in pigs treated with an ionized alkali mineral complex.

Thirty-nine healthy pigs (28-32 days old) were purchased from a commercial swine farm and housed at swine pens of the College. The animals were vaccinated intramuscularly (1 ml) with an attenuated live hog cholera virus (HCV, LOM strain) and then boostered at 5 weeks after the first vaccination. The animals were divided into 4 experimental groups: 0.05% (w/w) PowerFeel-supplemented diet (T-1, n = 10); 3% (w/w) SuperFeed-supplemented diet (T-2, n = 10); diluted PowerFeel solution (1 : 500, v/v) as drinking water (T-3, n=9); control (n=10). PowerFeel is an original form of ionized alkali mineral complex (IAMC) and SuperFeed is a commercial product of IAMC. The subpopulation of lymphocyte in blood was assayed by a flow cytometry and HCV-specific antibody was determined by an indirect immunofluorescence assay. In IMAC-treated groups, the proportions of subpopulation expressing MHC-class II, CD2+, CD4+, CD8+, and surface IgM+ B lymphocytes were significantly decreased at 5-weeks after the first vaccination. Significant decreases were also observed in the proportions of MHC-class II, CD2+ and CD8+ lymphocyte at 3-weeks after the booster injection. The humoral immune responses in T-1 and T-2 groups were greater than those in T-3 or control group. These results suggest that IAMC-supplemented diets may have an HCV-specific immunostimulatory effect in pigs.

Relation between lymphocyte subpopulations of peripheral blood and immune responses of modified live hog cholera virus vaccine in pigs treated with an ionized alkali mineral complex

Thirty-nine healthy pigs (28-32 days old) were purchased from a commercial swine farm and housed at swine pens of the College. The animals were vaccinated intramuscularly (1 ml) with an attenuated live hog cholera virus (HCV, LOM strain) and then boostered at 5 weeks after the first vaccination. The animals were divided into 4 experimental groups: 0.05% (w/w) PowerFeel-supplemented diet (T-1, n = 10); 3% (w/w) SuperFeed-supplemented diet (T-2, n = 10); diluted PowerFeel solution (1 : 500, v/v) as drinking water (T-3, n=9); control (n=10). PowerFeel is an original form of ionized alkali mineral complex (IAMC) and SuperFeed is a commercial product of IAMC. The subpopulation of lymphocyte in blood was assayed by a flow cytometry and HCV-specific antibody was determined by an indirect immunofluorescence assay. In IMAC-treated groups, the proportions of subpopulation expressing MHC-class II, CD2+, CD4+, CD8+, and surface IgM+ B lymphocytes were significantly decreased at 5-weeks after the first vaccination. Significant decreases were also observed in the proportions of MHC-class II, CD2+ and CD8+ lymphocyte at 3-weeks after the booster injection. The humoral immune responses in T-1 and T-2 groups were greater than those in T-3 or control group. These results suggest that IAMC-supplemented diets may have an HCV-specific immunostimulatory effect in pigs.

Protection of piglets born from ruminant pestivirus experimentally infected sows, and their contacts, to the challenge with hog cholera virus.

Two groups, A and B, of two specific pathogen-free pregnant sows were experimentally infected between the 25th and 29th days post-breeding with two strains of ruminant pestivirus: NADL cytopathic bovine viral diarrhoea virus for group A and Aveyron non-cytopathic border disease virus French strain for group B. Two other pregnant sows (group C) were kept uninoculated as control. When 7 weeks old, 8 piglets of group C were put in contact with 4 piglets of group A (group D), and 8 other piglets of group C with 4 piglets of group B (group E) in two separate pens with the purpose of testing the horizontal transmission of the viruses. All animals were kept under observation and serologically controlled at weekly intervals; two pigs of each group were finally submitted to a challenge with hog cholera virus. The two pigs of group E which were put in contact with the offspring of the border disease virus infected sow were protected; all other animals developed typical hog cholera symptoms and died. The relation between neutralizing titres of the sera to ruminant pestiviruses and protection to the challenge with hog cholera virus is discussed. The two protected pigs had high neutralizing antibody titres to border disease virus but no antibody to hog cholera virus at the time of the challenge. Though the two viruses look serologically distant, we surprisingly observed that infection with border disease virus protects against a superinfection with hog cholera virus.

[Oral immunization of suckling piglets against classic swine fever]. / Oralna imunizatsiia na bozaeshti praseta protiv klasichna chuma pri svinete.

Attempts were made to immunize suckling pigs against classic swine fever. The pigs were treated orally, originating from sows which were immunized on the 30th-40th and the 90th-100th day of pregnancy, as well as from sows which were vaccinated one month prior to impregnation. A Bulgarian lapinized K vaccine and a Soviet LK-VNIIVViM cell culture were used (immunization being carried out 1-2 hours before the newborns were allowed to suck) at the rate of 150 doses for both vaccines. It was demonstrated that the application of a live vaccine, which was patterned as cited above, eliminated the inhibiting action of colostral antibodies and induced stable postvaccinal immunity. However, the effectiveness of the immunity conferred depended on the vaccine used in each specific case. The Soviet vaccine, in which the amount of the virus per vaccinal dose was five times as much, was shown to be more appropriate to the needs for oral immunization of suckling pigs of sows that were immune to classic swine fever than the lapinized K vaccine.

Swine fever. Immunisation of piglets.

Vaccination against Swine Fever using the CL Chinese strain can be done in 7-day-old piglets if they are born of non-immune sows. The simultaneous weaning and vaccination emphasises the safety of this strain. The excellent immunity observed confirms the immunocompetence of 7-day-old piglets. In piglets born of immune sows and also weaned at 7 days, passive protection can extend beyond the age of 2 months if the sow is vaccinated several months prior to gestation. The immune level of the piglets would seem to depend on the interval between vaccination of the sow and farrowing and can be attributed to the quality of the antibodies transmitted by the colostrum. Piglets born of sows vaccinated 10 months prior to farrowing can be vaccinated as early as 5 weeks; the protection percentage observed at the age of about 6 months is over 80%. A booster injection at this age then confers immunity to future breeders throughout their economic life, i.e. 4 years in the reported experiment.

Possible factors influencing immunoglobulin A concentration in swine colostrum.

The immunoglobulin (Ig) A concentration in swine colostrum was determined by the single radial immunodiffusion method, using 157 samples collected from the same number of farm-raised sows in the Yamaguchi Prefecture of Japan during 1976 and 1977. The mean IgA value was 12.26 +/- 3.30 mg/ml, and the maximum and minimum values were 28.14 mg/ml and 5.63 mg/ml, respectively. To determine factors influencing the IgA concentration in swine colostrum, the following items were analyzed in the present study: season, district, breed, number of parturitions, udder section from which samples were collected, kind of feed, vaccinations of swine (erysipelas live-organism vaccine, hog cholera live-virus vaccine, Japanese encephalitis live-virus vaccine, and transmissible gastroenteritis live-virus vaccine), type of farming, and number of sows raised on a farm. Relationships between the IgA concentration in swine colostrum and each of these 12 items were analyzed. Of the 12 items, breed and number of parturitions were the most influential on the IgA concentration in colostra of farm-raised sows. Season, district, and vaccination with transmissible gastroenteritis live-virus vaccine were moderately influential. Udder section, kind of feed, vaccinations of swine (erysipelas live-organism vaccine, hog cholera live-virus vaccine, and Japanese encephalitis live-virus vaccine), type of farming, and number of farm-raised sows were slightly influential. The multiple correlation coefficient obtained was 0.5887 (P greater than 0.05).

Possible factors influencing the immunoglobulin G concentration in swine colostrum.

The immunoglobulin (Ig) G concentration in swine colostrum was determined by the single radial immunodiffusion method, using 157 samples collected from farm-raised sows in the Yamaguchi Prefecture of Japan during 1976 and 1977. The mean IgG value was 53.03 mg/ml, and the maximum and minimum values were 101.39 mg/ml and 11.74 mg/ml, respectively. The amount of IgG varied greatly among sows. To clarify the possible factors influencing the amount of IgG in colostrum, the following items were surveyed: season, district, breed, age of sows, number of parturitions, udder section from which samples were collected, kind of feed, vaccinations of swine erysipelas live-organism vaccine, hog cholera live-virus vaccine, Japanese encephalitis live-virus vaccine, tramsmissible gastroenteritis liver-virus vaccine, type of farming, and number of sows raised on a farm. Relationships between the amount of IgG in colostrum and each of these 13 items were analyzed. Seemingly, strong correlations with the amounts if IgG in colostrum were found with five items (district, number of parturitions, kind of feed, type of farming, and number of sows). To the contrary, five items (age, udder section, and vaccinations of swine erysipelas live-organism vaccine, hog cholera live-virus vaccine, and Japanese encephalitis live-virus vaccine) had poor correlations. Other items had moderate correlations. The multiple correlation coefficient obtained was 0.5499.