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Chang S.,U.S. Department of Agriculture | Chang S.,Michigan State University | Chang S.,Guangdong Wens Foodstuff Group Co. | Xie Q.,U.S. Department of Agriculture | And 6 more authors.

Marek's disease (MD) remains a continual threat to the poultry industry worldwide as the MD virus continues evolving in virulence. MD has been controlled primarily by intensive use of vaccines since 1969. Based on the antigenic and pathogenic differences of the viruses that the vaccines were derived from, commercially available MD vaccines are classified into three categories, MDV-1, -2, and -3 vaccines. This study was designed to compare the protective efficacy of MDV-1 (CVI988/Rispens) and MDV-3 (HVT) vaccines against challenge of a very virulent plus strain of Marek's disease virus (vv+MDV) in experimental and commercial egg-layer lines of chickens under controlled experimental conditions. The two experimental lines (63 and 72) of chickens carry a uniform MHC B*2 haplotype and are known to differ in resistance to MD. One of the two commercial egg-layer lines (WL and BL) segregates for three MHC haplotypes (B*2, B*15, and B*21); the other is unclear. MD incidences of the unvaccinated groups of both experimental lines and both commercial lines were 100% or close to 100% induced by the vv+MDV, 648A. Survived day patterns of the unvaccinated groups significantly differed between the two experimental lines, but did not between the two commercial lines, which suggested the two experimental lines do differ in resistance to MD but not between the two commercial lines. At manufacturers' recommended vaccine dosage, two HVTs conveyed comparable protection for the MD resistant line 63 chickens as did both CVI988/Rispens used in this study. The two HVTs also conveyed comparable protection for both commercial lines of chickens as did one of two CVI988/Rispens (CVI988/Rispens-A). At a 2000PFU uniform dose, HVT and CVI988/Rispens again conveyed comparable protection for the MD resistant experimental line of chickens. The findings suggest vaccine protective efficacy is modulated by factors including the types and the sources of vaccines and the genetic backgrounds of chickens. The findings also suggest HVT delivers equal protection in MD resistant lines of chickens as does the industry-recognized golden standard of MD vaccine, CVI988/Rispens. © 2014. Source

Lu W.H.,South China Agricultural University | Tun H.M.,University of Hong Kong | Tun H.M.,University of Manitoba | Sun B.L.,South China Agricultural University | And 7 more authors.
Veterinary Microbiology

Porcine reproductive and respiratory syndrome virus (PRRSV) was first reported in China since late 1995 and several variants were further reported in subsequence years, causing huge economic losses to the Chinese swine industry. To date, three major lineages (lineage 3, 5.1 and 8.7) of Type 2 PRRSV were reported in China based on our global genotyping. The present study provides the epidemiology of the PRRSV in South China based on the isolates collected during 2009-2012, indicating three lineages (lineage 3, 5.1 and 8.7) of Type 2 PRRSV were still circulating in this area. Our phylogenetic reconstruction indicated that lineage 3 re-emerged in 2010 formed a huge cluster with closely related to the 2004 isolates from Hong Kong. Furthermore, the inter-lineage genomic recombination between MLV vaccine strain (lineage 5) and a recently re-emerged lineage 3 virus (QYYZ) has also been found in a farm practicing MLV vaccination. Our in vivo experiment comparing the pathogenicity and clinical presentations among currently isolated viruses indicated that pigs infected with recombinant lineage 3 virus (GM2) showed persistent higher fever compared to pigs infected by its wild counterpart (QYYZ). This study enhanced our understanding on potential importance of the recombination of PRRSV along with their evolution. © 2014 Elsevier B.V. Source

Li Z.-L.,South China Agricultural University | Li Z.-L.,Guangdong Wens Foodstuff Group Co. | Zhu L.,South China Agricultural University | Ma J.-Y.,South China Agricultural University | And 8 more authors.
Virus Genes

A total of 127 porcine samples were collected from 48 farms in six provinces in south China. The positive rate of porcine epidemic diarrhea virus (PEDV) was 43.0 % (55/127), and the co-infection rate of PEDV and transmissible gastroenteritis virus (TGEV) was 12.0 % (15/ 127). The partial S gene and complete M gene were amplified from PEDV-positive strains by RT-PCR, cloned, sequenced and compared with each other, as well as with the reference strains in GenBank. Sequence homology results of the partial S gene and complete M gene showed that all south China field PEDV strains had nucleotide (deduced amino acid) sequence identities of 86.7-98.7 % (83.2-99.3 %) and 96.1-100 % (95.0-100%), respectively, with the foreign reference strains reported in GenBank. Phylogenetic analysis of the partial S gene showed that all the south China PEDV strains and two Thailand strains (08UB01 and 08RB07) belong to the same group and differ genetically from European strains and early domestic strains. Phylogenetic analysis of the complete M gene showed that all south China PEDV strains have a close relationship with most of the strains in Korea and Thailand, but differ genetically from the vaccine strain (CV777). © Springer Science+Business Media, LLC 2012. Source

Lu W.,South China Agricultural University | Sun B.,South China Agricultural University | Mo J.,South China Agricultural University | Zeng X.,South China Agricultural University | And 9 more authors.
Journal of Immunology Research

A porcine reproductive and respiratory syndrome virus (PRRSV) QY1 was serially passed on Marc-145 cells. Virulence of different intermediate derivatives of QY1 (P5, P60, P80, and P100) were determined. The study found that QY1 had been gradually attenuated during the in vitro process. Pathogenicity study showed that pigs inoculated with QY1 P100 and P80 did not develop any significant PRRS clinic symptoms. However, mild-to-moderate clinical signs and acute HP-PRRSV symptoms of infection were observed in pigs inoculated with QY1 P60 and P5, respectively. Furthermore, we determined the whole genome sequences of these four intermediate viruses. The results showed that after 100 passages, compared to QY1 P5, a total of 32 amino acid mutations were found. Moreover, there were one nucleotide deletion and a unique 34-amino acid deletion found at 5′UTR and in nsp2 gene during the attenuation process, respectively. Such deletions were genetically stable in vivo. Following PRRSV experimental challenge, pigs inoculated with a single dose of QY1 P100 developed no significant clinic symptoms and well tolerated lethal challenge, while QY1 P80 group still developed mild fever in the clinic trial after challenge. Thus, we concluded that QY1 P100 was a promising and highly attenuated PRRSV vaccine candidate. © 2014 Wenhui Lu et al. Source

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