Aihua Mao

Complete Genome Sequence of a Novel Species of Porcine Bocavirus, PBoV5

ABSTRACT Porcine bocavirus 5 is a novel porcine bocavirus species found in a pig with clinical diarrhea from a farm in China. Here, we report the complete genome sequence of strain PBoV5/JS677, which will help toward understanding the molecular and evolutionary characteristics of the porcine bocavirus.

Complete Genome Sequence of a Novel Porcine Circovirus-Like Agent

ABSTRACT We report here the genome sequence of a porcine circovirus-like agent. The sequenced genome of this porcine circovirus-like agent is composed of a 648-nucleotide circular DNA that includes three predicted protein-coding genes, which means the agent should be a novel member of the family Circoviridae.

Subcutaneous and intranasal immunization with Stx2B-Tir-Stx1B-Zot reduces colonization and shedding of Escherichia coli O157:H7 in mice.

The type III secretion system of Escherichia coli O157:H7 is involved in colonization of mammalian hosts by the organism. The translocated intimin receptor (Tir) is inserted into the mammalian host cell plasma membrane in a hairpin loop topology with the central loop of the molecule exposed to the host cell surface and accessible for interaction with an LEE-encoded bacterial outer membrane adhesin called intimin. Shiga toxin type 1 and 2 produced by E. coli O157:H7 are responsible for hemolytic uremic syndrome and able to promote intestinal colonization. Zonula occludens toxin (Zot) is a single polypeptide chain encoded by the filamentous bacteriophage CTXφ of Vibrio cholerae. Zot binds a receptor on intestinal epithelial cells and increases mucosal permeability by affecting the structure of epithelial tight junctions. Because of these properties, Zot is a promising tool for mucosal drug and antigen (Ag) delivery. In the current study, we constructed a novel fusion protein carrying both of the immunogenic B subunits derived from the two toxins, Tir and Zot, designated Stx2B-Tir-Stx1B-Zot, expressed in the E. coli BL21 and harvested the purified protein by a simple GST·Bind Resin chromatography method. We used a streptomycin-treated mouse model to evaluate the efficacy of subcutaneous vs. intranasal administration of the vaccine. Following immunization, mice were infected with E. coli O157:H7 and feces were monitored for shedding. Immune responses against Stx2B-Tir-Stx1B-Zot, Stx2B-Tir-Stx1B and control agent (GST/PBS) were also monitored. Subcutaneous immunization of mice with Stx2B-Tir-Stx1B-Zot induced significant Stx2B-Tir-Stx1B-Zot-specific serum IgG antibodies but did not significantly induce any antigen-specific IgA in feces, whereas intranasal immunization elicited significant Stx2B-Tir-Stx1B-Zot-specific serum IgG antibodies with some animals developing antigen-specific IgA in feces. Mice that were immunized intranasally with Stx2B-Tir-Stx1B-Zot showed dramatically decreased E. coli O157:H7 shedding compared to those of Stx2B-Tir-Stx1B and control agent following experimental infection. Mice immunized subcutaneously with Stx2B-Tir-Stx1B-Zot or Stx2B-Tir-Stx1B both showed reduced shedding in feces, moreover, Stx2B-Tir-Stx1B-Zot did better. These results demonstrate the perspective for the use of Stx2B-Tir-Stx1B-Zot to prevent colonization and shedding of E. coli O157:H7.

Development of a novel TaqMan-based real-time PCR assay for the detection of porcine boca-like virus (Pbo-likeV).

The recently discovered porcine boca-like virus (Pbo-likeV) is a member of the Parvoviridae family, genus Bocavirus, and it is potentially associated with swine disease. Several studies have associated Pbo-likeV with postweaning multisystemic wasting syndrome in pigs, but the full spectrum of clinical disease and the epidemiology of Pbo-likeV infection remain unclear. The availability of rapid and reliable molecular diagnostics would aid future studies of this novel virus. Thus, we developed a sensitive and specific TaqMan-based real-time PCR assay to target the Pbo-likeV NP1 gene. The assay reproducibly detected 20 copies of a recombinant DNA plasmid containing the NP1 gene, with a dynamic range of six orders of magnitude (102-107 copies). The assay did not cross-react with other animal viruses. Clinical evaluation found that Pbo-likeV was present in Chinese swine herds at a frequency of 44.2% (114/258). Higher infection rates were found in diseased pigs (56.1%, 101/180) compared with healthy pigs (16.7%, 13/78) (P < 0.05). Our assay for the diagnosis and quantification of Pbo-likeV was highly sensitive and specific, and should provide a reliable real-time tool for epidemiological and pathogenetic study of Pbo-likeV infection.

Prevalence of porcine circovirus-like agent P1 in Jiangsu, China

Recently, we identified a novel porcine circovirus type 2-like agent P1 isolate from swine. The present study represents the first survey of P1 prevalence in swine herds from Jiangsu, China, by using PCR targeting the complete genome of P1. Prevalences of 50% and 19% were found among 6 herds and 248 animals, respectively. The results indicate a high prevalence of P1 in China pig populations.

A Novel Porcine Circovirus-Like Agent P1 Is Associated with Wasting Syndromes in Pigs

A novel porcine pathogen tentatively named P1, which was obtained from the sera of the pigs exhibiting clinical signs of postweaning multisystemic wasting syndrome (PMWS) experimentally caused the classical clinic signs and pathologic lesions of the disease in pigs by direct in vivo injection with P1 DNA plasmids. Twenty colostrum-fed (CF) pigs that were free of PCV2 and P1 at 1 month of age were randomly designated equally to two groups. Group 1 pigs were each injected with 400 µg of the cloned P1 plasmid DNA into the superficial inguinal lymph nodes and Group 2 were injected with same amount of the empty pSK vector DNA and served as controls. Viremias were positively detected in 8 of 10 P1 infected pigs from 14–21 days post-inoculation (dpi). The 8 infected animals showed pallor of skin and diarrhea. Gross lesions in the pigs euthanized on 35 dpi were similarly characterized by encephalemia, haemorrhage of the bladder mucosa, haemorrhage of the superficial inguinal lymph nodes, lung atrophy and haemorrhage. Histopathological lesions were arteriectasis and telangiectasia of the cavitas subarachnoidealis, interstitial pneumonia, mild atrophy of the cardiac muscle cells, histiocytic hyperplasia of the follicles in the tonsils, and haemorrhage of the inguinal lymph nodes. P1 DNA and antigens were confirmed by PCR and immunohistochemistry in the tissues and organs of the infected pigs, including the pancreas, bladders, testicles/ovaries, brains, lungs and liver. There were no obvious clinical signs and pathological lesions in the control pigs. This study demonstrated that P1 infection is one of the important pathologic agents on pig farms.

Complete Genome Sequence of the Rearranged Porcine Circovirus Type 2

ABSTRACT We first report here the genome sequences of 4 rearranged porcine circovirus type 2 strains, JSTZ, ZJQDH1, ZJQDH2, and JSHM, isolated from porcine sera in China. The complete circular genomes of these isolates are 578, 483, 574, and 772 nucleotides in length, respectively. They are predicted to be defective interfering particles of porcine circovirus type 2. The findings will help us to understand molecular evolution of porcine circovirus type 2 and the relationship between porcine circovirus type 2 and diseases.

Contribution of Eukaryotic-Type Serine/Threonine Kinase to Stress Response and Virulence of Streptococcus suis

Streptococcus suis serotype 2 (SS2) is an important swine and human pathogen responsible for septicemia and meningitis. The bacterial homologues of eukaryotic-type serine/threonine kinases (ESTKs) have been reported to play critical roles in various cellular processes. To investigate the role of STK in SS2, an isogenic stk mutant strain (Δstk) and a complemented strain (CΔstk) were constructed. The Δstk showed a significant decrease in adherence to HEp-2 cells, compared with the wild-type strain, and a reduced survival ratio in whole blood. In addition, the Δstk exhibited a notable reduced tolerance of environmental stresses including high temperature, acidic pH, oxidative stress, and high osmolarity. More importantly, the Δstk was attenuated in both the CD1 mouse and piglet models of infection. The results of quantitative reverse transcription-PCR (qRT-PCR) analysis indicated that the expressions of a few genes involving in adherence, stress response and virulence were clearly decreased in the Δstk mutant strain. Our data suggest that SsSTK is required for virulence and stress response in SS2.

In vitro intragenomic rearrangement of porcine circovirus type 2.

ABSTRACT We report here for the first time the genome sequence of a rearranged porcine circovirus type 2 (PCV2) strain, CH-IVT1, isolated from PCV2-infected PK-15 cells. The complete circular genome of the CH-IVT1 is 605 nucleotides (nt) in length. The finding will help us to understand the molecular evolution of PCV2 and the relationship between PCV2 and PCV-associated diseases.

In Vitro and In Vivo Isolation of a Novel Rearranged Porcine Circovirus Type 2

ABSTRACT Here, we present the first report of a novel rearranged porcine circovirus type 2 (PCV2) strain named BIV, isolated from both in vitro and in vivo sources. The complete circular genome of BIV is 896 nucleotides in length. The data will help us to update current knowledge of the replication of PCV2 viruses in cell culture and of their molecular evolution, as well as their diagnosis.