An attenuated vaccine strain AVR1/08 of Korean respiratory type of infectious bronchitis virus (IBV) was developed by 89th passages of IBV D85/06 strain in chicken eggs. The AVR1/08 strain had higher virus titer at least 20 times (10∨1.3) than the parent virus D85/06 by egg inoculation method. The AVR1/08 strain had a single point mutation (S to Y) at position 56 of spike protein of IBV compared to parent virus IBV D85/06 strain. The mutation was observed consistently at viruses after 47th passage in chicken eggs. The AVR1/08 strain showed no virulence even after 6 passages in chickens and all chickens inoculated induced anti-IBV antibody 14 days after vaccination. The AVR1/08 strain had broad protective efficacy against QX type Korean nephropathogenic virus (Q43/06 strain), KM91 type Korean nephropathogenic virus (KM91 strain) and Korean respiratory virus (D85/06 strain). In contrast, Massachusetts (Mass) type attenuated vaccine strain H120 showed protection of 37.5 to 50% against these three viruses. Our results indicate that the AVR1/08 strain has potential as an attenuated vaccine effective in controlling IBVs circulating in Korea.

Live, avirulent Escherichia coli vaccine strains were constructed and tested for efficacy in preventing colibacillosis in 4-week-old pigs. Either or both of 2 plasmids were inserted into avirulent E coli strain G58-1 (0101:NM). These plasmids were pPMC4, which encodes for LTb subunits of heat-labile enterotoxin, and pDHF1, which encodes for K88ac fimbriae. Litter- and weight-matched pigs were removed from sows when they were 10 days old and vaccinated orally with the constructed strains or with G58-1 (negative control vaccine) when they were 2 weeks old and 5 days later. All pigs were challenge-inoculated with virulent E coli strain 3030-2 (0157:K88, LT+, STb+) 2 weeks after the first vaccination. Only 1 pig vaccinated with G58-1/pPMC4/pDHF1 developed diarrhea and none died following challenge inoculation. Seventeen of 31 control pigs developed diarrhea and 11 died. Of 18 pigs vaccinated with G58-1/pDHF1 then challenge-inoculated with the virulent strain, 5 developed diarrhea and 2 died. Fifteen of 18 litter- and weight-matched controls developed diarrhea and 8 died. When compared with G58-1 (negative control), G58-1/pPMC4 afforded no protection to pigs challenge-inoculated with 3030-2.

This study was conducted to study the UV protective effect against Haemonchus contortus infection in goats. Sixteen male goats were divided into 5 groups, control infected, control uninfected and UV 30minutes; UV 60minutes and UV booster 60minutes exposure. The UV groups were exposed to UV irradiation at wave length 254nm for 30 and 60 minutes. The UV booster 60min was administrated 2 doses of exposed larvae with an interval of one month. All groups except the control negative one were challenged for 42 days from the beginning. In UV booster 60min had reduction in egg count per gram feces and worm burden (93% & 34 % respectively). These parameters were similar in control infected, UV 30min and UV 60min groups. Increases in levels of antibodies were found in goats of UV booster 60min group the other groups. Finally, 2 doses of UV 60min exposure could protect goats from H. contortus.

The purpose of this study was to determine the safety and efficacy of a live Salmonella choleraesuis immunizing strain, obtained by repeated ingestion and recovery through porcine neutrophils. The strain was tested in mice and in pigs. The vaccine was safe and effective in controlled experimental trials, using clinical, pathologic, and microbiologic criteria. Vaccinated pigs were able to maintain normal weight gains during the 4-week observation period following challenge inoculation with a high dose of a virulent strain.

To develop a live vaccine strain against fowl typhoid and paratyphoid caused by Salmonella serovar Gallinarum biovar Gallinarum (Salmonella Gallinarum) and Salmonella serovar Enteritidis (Salmonella Enteritidis), respectively, several nalidixic acid resistant mutants were selected from lipopolysaccharide (LPS) rough strains of Salmonella Gallinarum that escaped from fatal infection of a LPS - binding lytic bacteriophage. A non - virulent and immunogenic vaccine strain of Salmonella Gallinarum, SR2 - N6, was established through in vivo pathogenicity and protection efficacy tests. SR2 - N6 was highly protective against Salmonella Gallinarum and Salmonella Enteritidis and safer than Salmonella Gallinarum vaccine strain SG 9R in the condition of protein-energy malnutrition. Thus, SR2 - N6 may be a safe and efficacious vaccine strain to prevent both fowl typhoid and paratyphoid.

Sixty-nine specific pathogen-free male Wistar rats approximately eight weeks of age were used to evaluate the efficacy of an attentuated strain of sialodacryoadenitis (SDA) virus in providing protection against infection on subsequent challenge with virulent SDA virus. Fifty-four animals were inoculated intranasally with approximately 10-1.5 median cell culture infectious doses of the 25th passage of SDA virus in L-2 cells. Randomly-selected vaccinated animals were killed in order to evaluate the safety and efficacy of attenuated virus by histopathological examination of the salivary glands, lacrimal glands, and lower respiratory tract, and titration of sera for antibody to SDA virus. At three months and six months post-vaccination (pv), animals were selected at random and challenged with virulent SDA virus. Seronegative, age-matched animals were also challenged, and served as controls. In animals examined at six to ten days pv, lesions were absent in submandibular and parotid salivary glands and lacrimal glands, but transient lesions were present in major airways of the lower respiratory tract. In a comparison of the incidence and extent of lesions, and antibody titers in challenged vaccinates and seronegative controls, lesions were minimal or absent in vaccinates compared to challenged naive rats, particularly in animals inoculated at three months pv. In addition, antibody titers in challenged vaccinates were much higher than were postinoculation titers in inoculated controls. In a comparison of lesions in salivary and lacrimal glands in vaccinated and control animals challenged at six months pv, there was a significant reduction in the number of animals without lesions in the vaccinated group (p = < 0.0001). Based on the incidence of lesions in target tissues and the marked antibody response in vaccinates on challenge with virulent SDA virus, it was concluded that prior inoculation with the attenuated strain of SDA virus provided a significant level of protection for up to six months postvaccination.

Pleuropneumonia is an important disease of swine caused by Actinobacillus pleuropneumoniae. Putative virulence determinants include capsule, lipopolysaccharide, and cytotoxin. We studied the virulence and virulence determinants of 2 strains: CM5 and CM5A of serotype 1. Strain CM5 was isolated from a pig with pleuropneumonia and passaged once in vitro; strain CM5A was a substrain of CM5 passaged 70 times in vitro. Pigs challenge exposed to an aerosol of 1.3 x 10(7) colony-forming units of CM5/ml died within 30 hours; pigs challenge exposed to an aerosol of 1.6 X 10(8) colony-forming units of CM5A/ml survived. The average thickness of the capsular layer was 137 nm in strain CM5 and 53 nm in strain CM5A in bacteria treated with homologous antibody and examined by transmission electron microscopy. Similarly, capsular material binding polycationic ferritin was found in colonies of strain CM5, but not in strain CM5A. The ratio of hexosamine to protein in extracted capsule of CM5 was more than twice that of CM5A. The polyacrylamide gel electrophoretic profile of the lipopolysaccharide, outer membrane proteins, and whole cell proteins did not differ between the 2 strains. Also, the amount of cytotoxin or endotoxin produced by the 2 strains during the logarithmic growth phase was not different. The electrophoretic profile of restriction endonuclease digested DNA was similar, with the exception of bands in the 750- and 620-basepair regions. It was concluded that attenuation of strain CM5A during in vitro passage was a result of reduced capsule production and that encapsulation is an important virulence determinant of A pleuropneumoniae, serotype 1.