The specificity of antibody responses in cattle naturally exposed to Fasciola hepatica

Fasciola hepatica causes significant morbidity and mortality in dairy cattle in the Andean region of Cajamarca, Peru, where prevalence of infection of up to 78% has been reported. ELISA and Western blot analyses were used to characterise antibody responses in dairy cattle to adult F. hepatica to excretory-secretory (E/S), somatic (SO) and surface (SU) antigens. Three groups of dairy cattle - calves, heifers and adult cows - naturally exposed to F. hepatica in this region, were monitored every 2 months over a 2-year period. Calves, heifers and adult cows all had antibodies which recognised a 28kDa protein in the SO preparation, whereas only adult cows had antibodies that recognised a 28kDa protein in E/S products. All three groups of cattle responded to a 60-66kDa group of proteins in E/S and SU preparations and a 17kDa antigen in SO products was recognised by antibodies from cows and heifers but not calves. The total antibody response to E/S antigens measured by ELISA, increased over time in calves and remained constantly high over the 2-year period in all three groups of cattle. Slight fluctuations in the antibody response occurred in the group of heifers and cows coinciding with seasonal changes in the level of challenge.     

IMMUNISATION OF CATTLE AGAINST VIBRIOSIS WITH VACCINES PREPARED FROM CAMPYLOBACTER FETUS SUBSP FETUS

Subcutaneous administration of vaccines prepared from cells of Campylobacter fetus subsp fetus strain A28 to heifers gave substantial protection against infertility due to C. fetus subsp venerealis strain B6. Strains A28 and B6 had different heat-stable antigens and conformed respectively to serotype B and serotype A of Berg et al (1971). The results suggested that the protective antigens were heat-labile antigens common to both strains. Although vaccines prepared from serotype B strains of C. fetus subsp fetus could be used to immunise cattle against vibriosis, the results did not suggest that their use in preference to those prepared from C. fetus subsp venerealis would offer any advantages.     

Adaption of ELISA for the detection of Campylobacter antibodies and its application in seroepidemiological studies in sheep and cattle herds

ELISA was adapted for the study of antigenic relations among important Campylobacters and for the presence of anti-campylo-bacter antibodies in 394 sheep and 265 cattle. Rabbit anti-C. jejuni, C. coli, G. fetus subsp. fetus and C. laridis heat-stable antigen sera were evaluated against 29 Campylobacter strains and 6 other bacteria. Anti-C. jejuni and G. coli reacted strongly with homologous antigens and weakly with C. fetus subsp. fetus, C. laridis and C. fecalis antigens. C. fetus subsp. fetus serum reacted mainly with its homologous antigen. C. laridis serum showed closer reactivity to C. jejuni than to C. fetus subsp. fetus, C. coli and C. fecalis. Insignificant cross-reactions were observed with Y. enterocolitica, S. dublin and E. aerogenes heat-stable antigens, Ewes vaccinated with C. fetus subsp. fetus bacterin showed higher ELISA titers against C. fetus subsp. fetus antigens than non-vaccinated ewes or rams. Twenty-five percent of the vaccinated animals showed titers as low as 95 % of the non-vaccinated animals. In cattle the lowest antibody titers against C. fetus subsp. fetus, C. jejuni, C. coli and C. laridis antigens were exhibited by the precolostrum sera followed by the postcolostrum and adult sera. These studies demonstrated the applicability of the ELISA test in seroepidemiological investigations concerning the distribution and significance of Campylobacter antibodies in food animal sera.     

Is there a benefit from an early booster vaccination in the control of equine influenza?

Conventional equine influenza vaccination schedules consist of a primary course of two vaccinations given 4-6 weeks apart followed by a third vaccination (booster) given approximately 5 months later. In between the primary course and the third vaccination, horses are generally considered not to be adequately protected against influenza. This study aimed to investigate whether Thoroughbred foals would benefit from a vaccination schedule in which the third vaccination was given earlier than in conventional vaccination schedules. The vaccines used were an inactivated whole virus equine influenza vaccine and an inactivated whole virus combination vaccine containing equine influenza and equine herpesvirus antigens. Four groups of foals were vaccinated with the two vaccines according to a conventional and an accelerated vaccination schedule in which the third vaccination was given 14 weeks after the first administration. In both groups, the fourth vaccination was given at the normally recommended interval of 26 weeks after the third vaccination for the combination vaccine and 52 weeks after the third vaccination with the influenza only vaccine. The horses were 4-11 months of age and seronegative for influenza. Immunological responses after vaccination were monitored for several months using the single radial haemolysis test. The results indicated that 28 weeks after the first vaccination, antibody levels in horses vaccinated according to the accelerated schedule were not significantly higher than in horses vaccinated according to the conventional schedule. In addition, the total level of antibody production (area under the curve) was not significantly different at that point although antibody titres were slightly higher (but not significantly so) between 16-30 weeks in the accelerated schedule. Between the third and fourth doses, horses vaccinated according to the accelerated schedule had antibodies against influenza below the level required for clinical protection for 39 and 18 weeks for the influenza only and the combination vaccine, respectively, whereas those vaccinated according to the conventional schedule had antibody titres below the level for clinical protection for 9-15 weeks in the corresponding period for both vaccines. Horses vaccinated according to the accelerated schedule with the combination vaccine had lower antibody titres after the fourth vaccination than those vaccinated according to the conventional schedule after the third vaccination, although antibody titres prior to vaccination were similar. For the influenza only vaccine, titres after the accelerated fourth administration were not different to those after the conventional third vaccination. There was no benefit from early booster vaccinations with the vaccines used in this study, so for these vaccines the conventional schedule provided better protection than the selected accelerated alternative. This may contrast with some other vaccine formulations, although a direct comparison using similar protocols has not been made.     

Efficacy of avridine as an adjuvant for Newcastle disease virus antigen in chickens

Avridine, a lipoidal amine with interferon-inducing and adjuvant properties, was an effective adjuvant for Newcastle disease antigen (NDA) in chickens. Eleven vaccine lots were evaluated: 2 commercial water-in-oil vaccines, 4 experimental oil emulsion vaccines, 4 avridine-containing vaccines, and a control lot of nonadjuvanted antigen. Avridine significantly enhanced the immunologic responses of chickens against NDA. Chickens vaccinated with the avridine-containing vaccines had significantly higher antibody titers (hemagglutination inhibition) than did chickens vaccinated with the commercial vaccines. Experimental oil emulsion vaccines prepared from the same antigens as avridine-adjuvanted vaccines induced higher hemagglutination inhibition antibody titers after primary but not after booster vaccination. Use of avridine as an adjuvant for NDA in vaccines for chickens induced immunologic protection rates similar to those induced by oil emulsion vaccines, without causing the reactogenic and tissue residue problems associated with the use of oil vaccines in chickens.     

Effects of vaccination against 18 immunogens in beef replacement heifers at weaning.

Humoral immune responses to vaccination, mean daily body-weight gains, morbidity, and mortality were compared in groups of beef replacement heifers from weaning to 4 months after weaning. The only difference in management among groups of heifers was the number and type of vaccines they received. Heifers were vaccinated at weaning (mean age, 205 days) and again 28 days later against 0, 1, 9, 10, 17, or 18 antigens, using commercially available monovalent and multivalent vaccines. The common vaccine component in all treatment groups was a modified-live bovine respiratory syncytial virus. Mean daily gain, morbidity, mortality, and serum neutralization antibody titers to bovine respiratory syncytial virus did not differ among treatment groups. Although the study revealed the safety of vaccinating beef heifers against 18 antigens at weaning, our data emphasized the need for serial vaccination to induce a measurable serum antibody response.     

Effects of stage of gestation and breed on bovine responses to vaccination with Brucella abortus strain 19.

Eighty-eight cattle were injected SC with 2.5 x 10(8) viable cells of Brucella abortus strain 19. All but 1 heifer became seropositive on the basis of the results of 7 brucellosis tests, and the proportion positive decreased with time. The proportion of cattle that were seropositive during a 20- to 67-week period after vaccination was as follows, in decreasing order: hemolysis-in-gel, 59%; buffered-acid plate antigen, 39%; ELISA, 16%; card, 10%; rivanol, 8%; cold complement-fixation, 7%; and automated complement-fixation, 5%. Using the serologic classification in Uniform Methods and Rules for brucellosis eradication, 7 cattle tested brucellosis-positive (2 suspects and 5 reactors). None of the 27 nonpregnant heifers tested positive. Of 18 heifers that were 84 to 135 days in gestation when vaccinated, 6 (33%) tested positive for brucellosis, compared with 0 of 13 and 1 (3%) of 30 heifers that were 11 to 78 and 145 to 253 days in gestation at vaccination, respectively (X2 = 12.07; 2 df; P less than 0.01). Neither breed (Angus, Hereford, Jersey, and Brahman) nor calf survival was related to brucellosis-positive results. Postpartum milk samples from 61 heifers and 24 tissues from 2 reactor cattle were culture-negative for B abortus.     

Immune responses of infected and vaccinated Hereford cattle to antigens of the cattle tick, Boophilus microplus

Responses of infested and vaccinated Hereford cattle to Boophilus microplus antigens were measured by enzyme-linked immunosorbent assay (ELISA), lymphocyte blastogenesis assay (LBA) and intradermal skin tests. Responses against soluble salivary gland extracts (SGS), salivary gland membrane (SGM), soluble gut extracts (GS), gut membrane (GM), soluble larval extracts (LS) and larval membrane (LM) antigens were tested. In one experiment, cattle infested with up to 160,000 ticks had positive cellular responses to SGS and significant antibodies against LM, GM, SGM, and SGS. Cellular responses to Concanavalin A were not depressed following infestation. Cattle vaccinated with GM, using Quil A as adjuvant, had positive cellular responses to gut and salivary gland antigens and significant antibody responses to all antigens tested. The antibody levels of vaccinated cattle were significantly higher than the antibody levels of infested cattle (P less than 0.05). In a second experiment, immune responses of cattle infested with 40,000 ticks were studied during 38 days. Cellular responses in LBA to several tick antigens were transiently elevated and significant levels of antibody were measured against LM, GM, SGM and SGS, from day 25 (P less than 0.05). Infested cattle had positive skin reactions following intradermal injection of larval and adult tick antigens (P less than 0.05).     

Use of a monovalent leptospiral vaccine to prevent renal colonization and urinary shedding in cattle exposed to Leptospira borgpetersenii serovar hardjo.

OBJECTIVE: To determine whether a monovalent Leptospira borgpetersenii serovar hardjo (type hardjobovis) vaccine commercially available in Australia, New Zealand, Ireland, and the United Kingdom would protect cattle from renal colonization and urinary shedding when exposed to a US strain of Leptospira borgpetersenii serovar hardjo. ANIMALS: 24 Hereford heifers that lacked detectable antibodies against serovar hardjo. PROCEDURE: Heifers received 2 doses, 4 weeks apart, of the commercial hardjo vaccine (n = 8) or a monovalent US reference hardjo vaccine (8) or were not vaccinated (controls; 8). Heifers were challenged 16 weeks later by intraperitoneal inoculation or conjunctival instillation. Serum antibody titers were measured weekly, and urine samples were examined for leptospires. Heifers were euthanatized 11 to 14 weeks after challenge, and kidney tissue was examined for evidence of colonization. RESULTS: All 8 heifers vaccinated with the reference vaccine were found to be shedding leptospires in their urine and had evidence of renal colonization. All 4 control heifers challenged by conjunctival instillation and 2 of 4 control heifers challenged by intraperitoneal inoculation shed leptospires in their urine, and all 8 had evidence of renal colonization. In contrast, leptospires were not detected in the urine or tissues of any of the 8 heifers that received the commercial hardjo vaccine. Heifers that received the commercial hardjo vaccine had significantly higher antibody titers than did heifers that received the reference vaccine. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that cattle that received 2 doses of the commercial hardjo vaccine were protected against renal colonization and urinary shedding when challenged with L borgpetersenii serovar hardjo strain 203 four months after vaccination.     

Evaluation of long-term antibody responses to two inactivated bovine viral diarrhoea virus (BVDV) vaccines

The aim of the present study was to determine the serological response of heifers after vaccination with two inactivated bovine viral diarrhoea virus (BVDV) vaccines by means of various ELISA tests. Three dairy farms were selected from the Galicia region of Spain. In each herd, a batch of heifers to be vaccinated for the first time was selected and followed for 15 months. Heifers from farm 1 (n = 25) were vaccinated with Vaccine A, whereas heifers from farm 2 (n = 16) were vaccinated with Vaccine B. Heifers from farm 3 (n = 17), where no BVDV vaccines were used, acted as controls. Blood samples were analyzed periodically for BVDV antibodies, using five commercial ELISAs, based on BVDV p80 antigen or whole virus.At the end of the study, none of the animals vaccinated with Vaccine A seroconverted according to p80 antibody status, whereas up to 80% tested positive by ELISA against whole virus antigen. For the animals vaccinated with Vaccine B, 2/16 animals seroconverted according to p80 antibody ELISAs, whereas all had seroconverted according to the ELISA against whole virus antigen. In most cases, based on the use of ELISAs to detect specific antibodies against the p80 protein, at 15 months post-vaccination with inactivated BVDV vaccines the responses did not seem to interfere with detection of antibody to BVDV infection. However, the finding of a small proportion of vaccinated animals seropositive against BVDV p80 antigen suggests that antibodies that interfere with diagnosis of BVDV infection within the herd could exist, even when using p80 ELISAs.     

Active immunization of beef heifers against luteinizing hormone: III. Evaluation of dose and longevity

Objectives were to evaluate the dose (Exp. 1) and purity of LH preparations (Exp. 2) on the anti-LH antibody response in heifers. Experiment 3 evaluated the longevity of LH immunization on sterility in heifers. In Exp. 1, 115 crossbred heifers were injected every 3 wk for 6 wk with .1, .33, 1.0, 3.0 or 9.0 mg of LH-ovalbumin. Concentrations of anti-LH antibodies generated were quantified by determining the percentage of binding of [125I]LH in serum. Mena LH binding over wk 0 to 12 was greater in heifers immunized with 1.0 mg conjugate than in heifers immunized with other doses (P less than .05). In Exp. 2, LH-ovalbumin conjugates were made from either LH-1, LH-2 or LH-3, which had relative immunological potencies of 2.1, 1.5 and 1.2 x NIH-LH-S1 units/mg, respectively. Forty-eight crossbred beef heifers were immunized against one of these three LH-ovalbumin conjugates, against LH conjugated without ovalbumin (LH-LH), or against ovalbumin alone (Oval). Estrous cycle activity was monitored by measuring serum progesterone concentration. Potency of the LH preparation used in the LH-ovalbumin conjugate was correlated (r = .94) with its ability to produce LH antibodies. In Exp.3, heifers were injected with 1 mg antigen every 2 wk for 10 wk. Five LH-1 heifers and five control heifers were slaughtered for examination of ovaries 10 wk after the last booster injection. The remaining five LH-I and five control animals were placed with a bull 8 wk after the last booster. All five control heifers conceived by 4 +/- 1 wk after placement with the bull whereas the LH-immunized heifers remained acyclic for 42 to 96 wk.     

Evaluation of an antibody-ELISA using five crude antigen preparations for the diagnosis of Trypanosoma evansi infection in cattle.

Attempts were made to improve the accuracy of an antibody-detection ELISA for the detection of Trypanosoma evansi infection in cattle by improving the method of preparation of the crude antigen used. An IgG-ELISA was performed with five different antigen preparations: crude soluble antigen, soluble and insoluble fractions of crude antigen treated with 0.1% formalin and whole formalin-fixed trypanosomes treated with either trypsin or 2-mercaptoethanol. An IgM-ELISA using crude soluble antigen was also performed. Each ELISA was evaluated using serum from 44 Indonesian cattle infected with T. evansi and 262 uninfected cattle from Australia. There was no significant difference between the sensitivity or specificity of the IgG-ELISA using each of the five antigens. The IgM-ELISA using a crude untreated lysate was significantly less sensitive (p<0.05) than the IgG-ELISA using the same antigen, trypsin-treated antigen or the 0.1% formalin-treated soluble antigen (68, 64 and 64%, respectively). These results show that these modifications to the method of producing crude antigens for the Ab-ELISA does not improve the accuracy of diagnosis of T. evansi infection in cattle.     

Fetal protection against continual exposure to bovine viral diarrhea virus following administration of a vaccine containing an inactivated bovine viral diarrhea virus fraction to cattle

OBJECTIVE: To evaluate the efficacy of a commercially available killed bovine viral diarrhea virus (BVDV) vaccine to protect against fetal infection in pregnant cattle continually exposed to cattle persistently infected with the BVDV. ANIMALS: 60 crossbred beef heifers and 4 cows persistently infected with BVDV. PROCEDURES: Beef heifers were allocated to 2 groups. One group was vaccinated twice (21-day interval between the initial and booster vaccinations) with a commercially available vaccine against BVDV, and the other group served as nonvaccinated control cattle. Estrus was induced, and the heifers were bred. Pregnancy was confirmed by transrectal palpation. Four cows persistently infected with BVDV were housed with 30 pregnant heifers (15 each from the vaccinated and nonvaccinated groups) from day 52 to 150 of gestation. Fetuses were then harvested by cesarean section and tested for evidence of BVDV infection. RESULTS: 1 control heifer aborted after introduction of the persistently infected cows. Bovine viral diarrhea virus was isolated from 14 of 14 fetuses obtained via cesarean section from control heifers but from only 4 of 15 fetuses obtained via cesarean section from vaccinated heifers; these proportions differed significantly. CONCLUSIONS AND CLINICAL RELEVANCE: A commercially available multivalent vaccine containing an inactivated BVDV fraction significantly reduced the risk of fetal infection with BVDV in heifers continually exposed to cattle persistently infected with BVDV. However, not all vaccinated cattle were protected, which emphasizes the need for biosecurity measures and elimination of cattle persistently infected with BVDV in addition to vaccination within a herd.     

Immunization of Cattle Against Rabies Using Inactivated Cell Culture Vaccines

Twenty-one heads of cattle were vaccinated with Madibovin, 31 with Rabdomun and 127 with Rabisin on 4 different farms. Rabies neutralizing antibody titre (≥0.5 IU/ml) was detected in 80% of 163 animals tested about 1 month and in 42% of 133 animals tested about 1 year after primary vaccination. On 3 of the farms 86 animals received booster vaccination about 1 year after primary vaccination. All these animals had antibody titre (≥0.5 IU/ml) about 1 month after booster and antibody levels were higher than after the primary vaccination. Rabies antibody titres (≥0.5 IU/ml) were detected in 96% of 50 animals tested 1 year after the booster. No significant differences (p>0.05) in antibody levels were detected between animals vaccinated with Madibovin or Rabisin (farm C) respectively with Rabisin or Rabdomun (farm D) at any collection time. Responses to rabies vaccines varied considerably between the farms. After primary vaccination of the animals on 2 farms with the same batch of Rabisin, the antibody levels clearly differed (p<0.0001) between the farms.Our results indicate that booster is always necessary after primary vaccination to ensure that all animals are protected.     

Alternative vaccination against equine botulism (BoNT/C)

REASON FOR PERFORMING STUDY: In Europe the incidence of botulism in horses has increased in the last decade due to the growing popularity of haylage feeding. Recombinant vaccines are safer and less expensive to produce and are generally better tolerated than toxoids. OBJECTIVES: To investigate whether the recombinant C-terminal half of the heavy chain of the botulinum neurotoxin C (Hc BoNT/C) in combination with an immunstimulatory adjuvant is an appropriate vaccine candidate for horses by testing its efficacy to induce neutralising antibodies and by comparing its immunogenic properties and adverse reactions to a commercial toxoid vaccine. Formation of oedema and local pain reactions were assessed. ELISA and Western blot assay against Hc BoNT/C and testing of neutralising antibody induction in a mouse protection assay were used to evaluate the immune response. RESULTS: With the recombinant vaccine, only minor local swelling with full recovery after 5 days was noted after brisket injections. The toxoid vaccine produced local, painful reactions with longer recovery periods of up to 2 weeks. Horses vaccinated with either vaccine induced neutralising antibodies after the second booster vaccination, while seroconversion on ELISA and Western blot to Hc BoNT/C was apparent after the first recombinant vaccination, and at various time points in the vaccination schedule in horses that received commercial toxoid vaccine. CONCLUSION: The recombinant vaccine showed fewer adverse reactions compared to the only commercially available vaccine but induced similar concentrations of neutralising antibodies. There was no correlation between the serological response to Hc BoNT/C and the neutralising capacity of serum. POTENTIAL RELEVANCE: Recombinant Hc BoNT/C is an appropriate vaccine candidate to stimulate production of neutralising antibodies against botulinum neurotoxin C in horses and creates only minor local reactions at the injection site.     

Cedivac-FMD can be used according to a marker vaccine principle

In this study, we investigated whether Cedivac-FMD, an emergency vaccine against foot-and-mouth disease (FMD), is suitable for use conjointly with a screening program intended to confirm freedom from disease in vaccinated herds based on evidence of virus replication in vaccinates. Different sets of sera were tested using the Ceditest FMDV-NS ELISA for the detection of antibodies against non-structural proteins (NSPs) of FMD virus. During a vaccine safety study, serum samples were collected from 10 calves, 10 lambs and 10 piglets following administration of a double dose and a repeat dose of high payload trivalent Cedivac-FMD vaccine. All serum samples collected both 2 weeks following the administration of a double dose as well as those collected 2 weeks after the single dose booster (given 2 weeks after the double dose) were negative in the Ceditest FMDV-NS ELISA. In a series of vaccine potency experiments, serum samples were collected from 70 vaccinated cattle prior to and following exposure to infectious, homologous FMD virus. When testing cattle sera collected 4 weeks after vaccination with a regular dose of monovalent >6 PD(50) vaccines, 1 of 70 animals tested positive in the NSP antibody ELISA. After infection with FMD virus, antibodies to NSP were detected in 59 of 70 vaccinated cattle and 27 of 28 non-vaccinated control animals within 7 days. Cedivac-FMD vaccines do not induce NSP antibodies in cattle, pigs or sheep following administration of a double dose or a repeat dose. FMD-exposed animals can be detected in a vaccinated group within 7-14 days. Because Cedivac-FMD does not induce NSP antibodies, the principle of 'marker vaccine' applies.     

A comparison of DNA vaccines expressing the 45W, 18k and 16k host-protective antigens of Taenia ovis in mice and sheep

The immunogenicity of DNA vaccines encoding three different Taenia ovis host-protective antigens was compared in mice and sheep. DNA vaccines encoding the 45W, 18k and 16k antigens of T. ovis were constructed. The ability of DNA vaccines encoding the 45W and 18k genes to express antigen was confirmed by Western blotting of transfected Cos-7 cells. BALB/c mice were vaccinated intramuscularly with 45W, 18k or 16k DNA vaccines and the humoral immune response analysed by ELISA. DNA vaccines expressing 45W, 18k or 16k antigen were immunogenic in mice and generated significant titres of antigen-specific antibody. Intramuscular vaccination of outbred sheep with the T. ovis DNA vaccines generated significantly lower titres of 45W-specific antibody and failed to generate 18k or 16k-specific antibody. The findings of this study show that each of the three T. ovis host-protective antigens are amenable to delivery via DNA vaccines, and that the parameters governing the efficacy of DNA vaccines in sheep require further investigation.     

Protective effects against abortion and fetal infection following exposure to bovine viral diarrhea virus and bovine herpesvirus 1 during pregnancy in beef heifers that received two doses of a multivalent modified-live virus vaccine prior to breeding

Objective-To determine whether administration of 2 doses of a multivalent, modified-live virus vaccine prior to breeding of heifers would provide protection against abortion and fetal infection following exposure of pregnant heifers to cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV) and cattle with acute bovine herpesvirus 1 (BHV1) infection. Design-Randomized controlled clinical trial. Animals-33 crossbred beef heifers, 3 steers, 6 bulls, and 25 calves. Procedures-20 of 22 vaccinated and 10 of 11 unvaccinated heifers became pregnant and were commingled with 3 steers PI with BVDV type 1a, 1b, or 2 for 56 days beginning 102 days after the second vaccination (administered 30 days after the first vaccination). Eighty days following removal of BVDV-PI steers, heifers were commingled with 3 bulls with acute BHV1 infection for 14 days. Results-After BVDV exposure, 1 fetus (not evaluated) was aborted by a vaccinated heifer; BVDV was detected in 0 of 19 calves from vaccinated heifers and in all 4 fetuses (aborted after BHV1 exposure) and 6 calves from unvaccinated heifers. Bovine herpesvirus 1 was not detected in any fetus or calf and associated fetal membranes in either treatment group. Vaccinated heifers had longer gestation periods and calves with greater birth weights, weaning weights, average daily gains, and market value at weaning, compared with those for calves born to unvaccinated heifers. Conclusions and Clinical Relevance-Prebreeding administration of a modified-live virus vaccine to heifers resulted in fewer abortions and BVDV-PI offspring and improved growth and increased market value of weaned calves.     

Immune Effect of Inactivated Vaccines against Foot-and-Mouth Disease and Their Interference on Differential Diagnosis

Vaccination with inactivated vaccine is an important measure to prevent and control foot-and-mouth disease (FMD), however, the immune effect and antigenic purity of inactivated vaccines are two major concerns for the establishment and evaluation of FMD free zones with vaccination. In this study, four groups of FMD type O and type A bivalent inactivated vaccines from 3 FMD vaccine manufacturers (designated as A, B and C) were selected to inoculate healthy juvenile cattle of FMD free. All cattle were immunized 3 or 4 times at a 1-month interval. Serum samples were collected before and after 1 month of every vaccination to determine the level of antibody to structural protein and non-structural protein. Results：(1) The qualified rates of antibody to structural protein: in group a1 (vaccine from company A, different batches), the antibody qualified rate could reach 100% for type O and type A, respectively after each vaccination. In group a2 (vaccines from company A, same batch), the antibody qualified rates were 36.7%, 98.3% and 100% for type O, and 15%, 86.7% and 100% for type A after the first to the third vaccination, respectively. In group b (vaccine from company B, same batch), the antibody qualified rates were 18.3%, 97% and 100% for type O, and 1.7%, 45% and 53.3% for type A after the first to the third vaccination, respectively. In group c (vaccines from company C, same batch), the antibody qualified rates were 26.7%, 96.7% and 100% for type O, and 21.7%, 71.7% and 100% for type A after the first to the third vaccination, respectively. (2) Antibody positive rate to non-structural protein 3ABC (confirmed with second ELISA test): In group a1, the positive rates were 0.7%, 1.4%, 9.5% and 4.8% after the first to the fourth vaccination, respectively; In group a2 and c, no 3ABC antibody-positive animal was detected after 3 repeated vaccination; In Group b, only one animal with a positive rate of 0.6% was detected after the third vaccination. The antibody qualified rates to the structural protein of FMDV in 3 of the 4 groups were far less than 70% after the primary vaccination, however, those were increased significantly after boost and repeated vaccination. The antigen purity of vaccines in three groups (a2, b and c) can meet the requirement of OIE standard on the FMD vaccine, however, the seroconversion to 3ABC antibody was obvious in animals from group a1 after repeated vaccination, which would cause some extent of interference to differential diagnosis. Also, a combination of a primary screening test and a confirmatory ELISA test can further improve the accuracy of differential diagnosis. This study provides an important scientific basis to make a rational program for establishment and evaluation of FMD free zone with vaccination.     

口蹄疫灭活疫苗的免疫效果及其对鉴别诊断的干扰

灭活疫苗免疫是防控口蹄疫的重要措施,但是灭活疫苗的免疫效果及其对感染与免疫鉴别诊断的干扰一直是口蹄疫免疫无疫区建设评估需要明确的重要问题。本研究中选择了3个企业（代号A、B与C）的4组口蹄疫O型与A型二价灭活疫苗,分别免疫口蹄疫抗体阴性健康未成年牛,免疫3～4次,测定免疫前后结构蛋白和非结构蛋白抗体的应答水平。结果显示：（1）结构蛋白抗体合格率：a1组（A企业多批次疫苗）4次免疫后O型和A型均为100%;a2组（A企业同批次疫苗）一~三免O型为36.7%、98.3%与100%,A型为15%、86.7%与100%;b组（B企业疫苗）一~三免O型为18.3%、97%与100%,A型为1.7%、45%与53.3%;c组（C企业疫苗）一~三免O型为26.7%、96.7%与100%,A型为21.7%、71.7%与100%。（2）非结构蛋白3ABC抗体阳性率（两种方法复核结果）：a1组一~四免分别为0.7%、1.4%、9.5%与4.8%;a2组和c组三次免疫均未检测到阳性;b组仅三免后阳性率为0.6%。3组灭活疫苗首次免疫牛的抗体合格率远不及70%,但加强免疫后抗体合格率均显著提高;非结构蛋白抗体检测结果表明有3组疫苗的抗原纯净度符合OIE的要求,但a1组灭活疫苗免疫后,仍然对感染与免疫鉴别诊断存在干扰;采用两种非结构蛋白抗体检测方法进行复核检验,可以提高感染与免疫鉴别诊断的准确性。本研究为口蹄疫免疫无疫评价方案的制定提供了科学依据。