[Determination of acetone in urine by headspace gas chromatography-mass spectrometry]

Objective: To establish a method for determination of acetone in urine by headspace gas chromatography-mass spectrometry. Methods: From March to June 2021, the 3.0 ml urine sample was placed in a headspace bottle with 4.0 g of anhydrous sodium sulfate and sealed. Equilibration time was 30 min at 85 ℃. The separation was carried out on a DB-5MS column. The urine sample was detected by mass spectrometry and quantified by external standard method. Results: The method for the determination of acetone in urine by headspace gas chromatography-mass spectrometry had good linearity in the range of 51.2-1024.0 μg/L, and the correlation coefficient was 0.9995. The detection limit and the lower limit of quantification of acetone were 16.4 μg/L and 54.6 μg/L. The average recoveries of samples ranged from 94.9% to 96.8%. The intra-assay precision and inter-assay precision were both less than 10%. Samples can be stored at least 7 d at 4 ℃ or -20 ℃. Conclusion: This method has simple sample preparation and high sensitivity. It can be used for monitoring and evaluation of urinary acetone in the general population and occupationally exposed populations.

[Survey on the cognition of the "undetectable equals untransmittable" concept among HIV-infected men who have sex with men receiving antiviral treatment]

Objective: To explore the cognition of the "undetectable equals untransmittable" ("U=U") concept and associated factors among HIV-infected men who have sex with men (MSM) receiving antiviral treatment (ART) in Shenzhen, and provide evidence for designing promotion and advocacy strategies for the "U=U" concept. Methods: We recruited HIV-infected MSM receiving ART using convenient sampling method combined with routine follow-up in Shenzhen through conducting observational survey. The sample size was estimated to be 475. A questionnaire was administered to collect socio-demographic characteristics, sexual behaviors, ART, viral load testing and the cognition towards "U=U" in HIV-infected MSM. Logistic regression was used to access factors associated with acceptance of "U=U". Results: A total of 490 HIV-infected MSM receiving ART were recruited. Of whom, 60.2% (295/490) were aware of "U=U" and 50.6% (248/490) accepted "U=U". Multiple logistic regression showed that participants who had an educational level of college or above (aOR=1.76,95%CI: 1.12-2.75) were more likely to accept "U=U". Those who had no local residency (aOR=0.51,95%CI: 0.29-0.92), had viral load >0 copies/ml in the last testing (aOR=0.61,95%CI: 0.38-0.98) and were unaware of "U=U" (aOR=0.13, 95%CI: 0.09-0.21), were less likely to accept "U=U". Conclusions: HIV-infected MSM receiving ART had a low cognition level of "U=U" in Shenzhen. Promotion and advocacy on this concept through healthcare workers should be enhanced in combination with routine follow-up in order to improve their ART adherence and outcome of treatment. Furthermore, developing related guidelines on "U=U" according to the characteristics of HIV-infected individuals is warranted to improve the normalization of promotion and advocacy on "U=U".

[Determination of phenylglyoxylic acid and mandelic acid in urine by ultra high performance liquid chromatography tandem mass spectrometry]

Objective: To develop a method for the analysis of phenylglyoxylic acid (PGA) and mandelic acid (MA) in urine by ultra-high performance liquid chromatography tandem mass spectrometry. Methods: The study was conducted in April 2022. Urine samples were directly diluted with the initial mobile phase, separated by Waters HSS T3 column after passing through the membrane, and analyzed under negative ionization mode (ESI(-)) and multiple reaction monitoring (MRM) conditions, the contents of PGA and MA in human urine were quantitatively determined by external standard method. Results: The determination of PGA and MA showed a good linear relationship within the range of 10-1000 ng/ml, with a correlation coefficient of 0.9999. The linear regression equation of PGA was y=1141.4x+2157.3, the detection limit and lower limit of quantification of the method were 0.081 ng/ml and 0.269 ng/ml, and the recovery rate was 90.47%-99.83%. The linear regression equation of MA was y=62.8x+140.3, the detection limit and lower limit of quantification of the method were 0.551 ng/ml and 1.836 ng/ml, and the recovery rate was 92.75%-101.09%. The intra and inter batch precision of PGA and MA were both<5%. Conclusion: An ultra-high performance liquid chromatography tandem mass spectrometry method for the analysis of PGA and MA in urine was established.The sample pretreatment operation is simple, and the accuracy and precision of the method meet the standard requirements. It can be used for monitoring and evaluating PGA and MA in urine of the general population and occupational contact population.

[Evaluation of effects of comprehensive intervention based on key persons on AIDS-related high-risk behaviors in male sex workers in entertainment venues]

Objective: To evaluate the effect of comprehensive intervention model based on key persons in entertainment venues on the incidence of AIDS-related high-risk behaviors in male sex workers (MSW). Data from this study thus can be used to provide compelling evidence for the wider implementation of the intervention model. Methods: In this randomized controlled trial, MSW were recruited and followed-up from May to December, 2021 in entertainment venues in Wuxi, Jiangsu Province, with an estimated sample size of 320. The MSW in the intervention group were provided with comprehensive interventions via key persons in entertainment venues compared with the control group receiving routine interventions. The effect of the intervention model was assessed by comparing the behavioral differences between these two groups and in the intervention group before and after intervention. Results: A total of 330 MSW were recruited at baseline survey, in which 168 were divided into intervention group and 162 into control group. There was no significant difference in socio-demographic characteristics between two groups (all P>0.05). After intervention for 6 months, the rate of consistent condom use in commercial homosexual activities in the intervention group was 79.5% (101/127), higher than 63.2% (74/117) in the control group, and in the intervention group, 90.1% (73/81) of MSW used condom consistently in heterosexual activities, higher than in the control group (59.6%, 59/99) . Compared with 30.8% (36/117) of MSW with drug abuse history in the control group, a lower proportion of 9.4% (12/127) was observed in the intervention group. Differences in all of aforementioned variables were significant (all P<0.05). After intervention, the incidence of group sex was 3.9% (5/127) in the intervention group and 9.4% (11/117) in the control group, the incidence of anal sex post-alcohol consumption was 40.2% (51/127) in the intervention group and 32.5% (38/117) in control group, the differences were not significant (all P>0.05). Conclusions: The intervention model based on key persons in entertainment venues could promote consistent condom use in MSW in both commercial homosexual and heterosexual activities and help them reduce drug abuse, but had no significant effect on decreasing group sex and anal sex after alcohol consumption. It is crucial to improve the intervention model according to the specific characteristics of MSW in order to enhance the effects of comprehensive intervention.

[A non-targeted metabolomics study on serum of occupational people exposed with nanometer titanium dioxide particles (TiO(2)-NPs)]

Objective: To study the changes of serum metabolic profile of occupational people exposed with nanometer titanium dioxide particles (TiO(2)-NPs), and to explore the biomarkers and injury mechanism of TiO(2)-NPs health effects. Methods: From June 2020 to June 2021, a TiO(2)-NPs production enterprise was selected as the research site by a typical sampling method, 64 people in the TiO(2)-NPs exposure group were selected from the enterprise, and 62 people of the logistics administrative staff in the same enterprise were selected as the control group, and blood samples were collected using non-anticoagulant blood collection tubes. After the samples were methanol-precipitated, the untargeted metabolomic data was collected by ultra-high performance liquid chromatography time-of-flight mass spectrometry, and biomarkers were screened and metabolic pathway analysis was performed. Results: 46 different metabolites were screened out by P<0.05 and variable importance projection index (VIP) value >1, mainly including glycerides, sphingomyelin, glycerophospholipid, fatty acyl, etc.; By ROC analysis to determine 3-hydroxy-4, 5-dimethyl-2 (5H) - furanone, 4-aminobiphenyl, heptanoylcarnitine, Hexadecanedioic acid mono-L-carnitine ester, Ibutilide, LysoPA (18∶1 (9Z) /0∶0), LysoPC (18∶0), PC (16∶0/16∶0), PC (16∶0/20: 4 (5Z, 8Z, 11Z, 14Z) ), PC (P-18∶1 (9Z) /P-18∶1 (9Z) ) 10 candidate biomarkers; involving changes in 4 metabolic pathways, namely glycerophospholipid metabolism, sphingolipid metabolism, phenylalanine, tyrosine and tryptophan acid biosynthesis, linoleic acid metabolism. Conclusion: Occupational exposure to TiO(2)-NPs has a significant impact on serum metabolic profiles.

[Relationships between lead-induced learning and memory impairments and gut microbiota disturbance in mice]

Objective: To explore the effect of lead exposure on the neurobehavior and gut microbiota community structure in mice. Methods: In August 2019, 64 C57BL/6 mice were randomly divided into 4 groups: control group (0 ppm) , low lead exposure group (20 mg/l) , medium lead exposure group (100 mg/l) and high lead exposure group (500 mg/l) . During the experiment, they were free to eat and drink. The drinking water of the lead exposure group was mixed with lead acetate, and sodium acetate was added in the control group. After 10 weeks of exposure, the Morris water maze was used to test the learning and memory ability of each group of mice, and then they were sacrificed for sampling. ICP-MS was used to detect lead content in whole blood and brain tissue. ELISA was used to determine the level of IL-1β in mouse serum. 16S rRNA sequencing was used to detect the structural diversity of the intestinal flora in feces, and then the correlation between the flora and behavior indicators was analyzed. Results: In the Morris water maze experiment, compared with the control group, there was no significant difference in the body weight and swimming speed of the mice in the lead exposure groups. The escape latency of the mice in the 100 mg/l and 500 mg/l dose groups was prolonged, and the number of platform crossings decreased (P<0.05) ; meanwhile, the staying time of the mice in the 500 mg/l Pb-treated group in the target quadrant was lower than that of the control group, and the difference was statistically significant (P<0.05) . Compared with the control group, the blood lead content of the mice in each lead exposure group was significantly increased, and the brain lead content of mice in the 500 mg/l dose group was significantly elevated (P<0.05) . The serum IL-1β levels of mice in each lead exposure group were higher than those of the control group (P<0.05) . At the phylum level, the relative abundance of the Proteobacteria phylum in all of Pb-treated groups was significantly increased (P<0.05) ; at the genus level, Allobaculum, Desulfovibrio, Lachnospiraceae_NK4A136_group, Turicibacter and Ureaplasma were significantly increased (P<0.05) . Among them. The relative abundance of Desuffaoibrio, Turici bacter, and Ureaplasma was negatively correlated with the residence time of mice in the quadrant of the platform (r=-0.32, -0.29, -0.44, P<0.05) . Conclusion: Lead exposure induced learning and memory impairments in mice, which may be related to the disturbance of the gut microbiota.

Downregulation of lncRNA CCHE1 inhibits cell proliferation, migration and invasion by suppressing MEK/ERK/c-MYC pathway in nasopharyngeal carcinoma

OBJECTIVE

The current study was designed to investigate the functionality of lncRNA CCHE1 in nasopharyngeal carcinoma.

MATERIALS AND METHODS

MiRNA levels of lncRNA CCHE1 were examined by RT-qPCR. CCK8 assay and colony formation assay were together performed to detect cell proliferation viability. Furthermore, wound healing assay and transwell assay were respectively conducted to assess cell migration and invasion. In addition, proteins related to MEK/ERK/c-MYC pathway were detected by Western blot.

RESULTS

Elevated levels of CCHE1 were verified in NPC cell lines. Downregulation of CCHE1 significantly inhibited tumor growth and suppressed A549 cell proliferation, migration and invasion. MEK/ERK/c-MYC pathway was activated in nasopharyngeal carcinoma. Treatment of PD98059 (MEK inhibitor) or SCH772984 (ERK inhibitor) reversed the effects of CCHE1 on cell proliferation, migration and invasion in NPC.

CONCLUSIONS

The present study suggested that downregulation of lncRNA CCHE1 could inhibit cell proliferation, migration and invasion by suppressing MEK/ERK/c-MYC pathway in nasopharyngeal carcinoma.

[Metabolomics study of urine with Benzene, Toluene and Xylene combined exposure based on ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry]

Objective: To study the effects of combined occupational exposure of benzene, toluene, and xylene on human metabolism at an overall level, and to screen biomarkers related to the combined occupational exposure of benzene, toluene, and xylene, and to explore the mechanism of early health effects preliminarily caused by combined occupational exposure of benzene, toluene, and xylene by identification of biomarkers and retrieval of metabolic pathways. Methods: A shoe-making company was selected as the research site. Twenty subjects for the exposed group and the control group were selected separately, and urine of the subjects was collected. The metabolic profiles of the samples were collected by liquid chromatography time-of-flight mass spectrometry, and professional metabolomics and multivariate statistical analysis software were used to establish PCA and OPLS-DA analysis models to screen potential biomarkers and identify biomarkers. Finally, based on the dynamic changes and trends of potential biomarkers between groups, the mechanism of body damage caused by benzene, toluene, and xylene was initially explored. Results: Urine metabolomics analysis showed that the metabolic profile of urine samples of the benzene, toluene, and xylene combined exposure group was different from that of the control group. 27 potential biomarkers that were closely related to the combined exposure of benzene, toluene, and xylene were screened and identified. These potential biomarkers were enriched in 16 metabolic pathways, of which 3 pathways were significantly enriched (P<0.05) , respectively, lysine metabolism, amino sugar metabolism, and nucleotide sugar metabolism. Conclusion: The metabonomics method can well reflect the changes in the metabolome of urine samples in the occupational population after the combined exposure of benzene, toluene, and xylene, which will help us better evaluate the risk of combined exposure of benzene, toluene, and xylene and prevent and control their health risks.

Hepatitis B core antigen-based vaccine demonstrates cross-neutralization against heterologous North American Porcine Reproductive and Respiratory Syndrome Virus (PRRSV-2) strains

The U.S. swine industry have been bearing the financial impact of Porcine Reproductive and Respiratory Syndrome (PRRS) for decades. Absent of a safe and efficacious vaccine to combat PRRS virus's genetic heterogeneity, it remains a costly disease on pig farms across the country. We have developed virus-like-particle (VLP) based vaccines that incorporate 4 PRRSV epitopes in the hepatitis B core antigen (HBcAg) backbone. Administration of the vaccines in female BALB/C mice resulted in extremely significant PRRSV epitope specific antibody response. One vaccine candidate GP3-4 was able to mount a significant viral neutralizing response against both parental PRRSV strain VR2385 and heterologous PRRSV strain NADC20, showing a promising potential for cross-protection against PRRSV.

HGF alleviates renal interstitial fibrosis via inhibiting the TGF-β1/SMAD pathway

OBJECTIVE

To study the role of HGF (stem cell growth factor) in renal interstitial fibrosis and to explore its underlying mechanism.

MATERIALS AND METHODS

A unilateral ureteral obstruction (UUO) mouse model was first constructed, and kidney samples of mice were then collected. Fibrosis-related indicators in UUO mice kidney were detected by Western blot. The mRNA and protein levels of HGF in UUO mice were detected by quantitative Real-time-polymerase chain reaction (qRT-PCR) and Western blot, respectively. The HGF overexpression mouse model was established by using UUO mice. For in vitro experiments, fibrosis-related indicators and the expression of HGF were detected in transforming growth factor-β1 (TGF-β1)-induced NRK-52E cells. Finally, a p-SMAD3 knockdown mouse model was established to confirm whether p-SMAD3 was involved in HGF-regulated renal interstitial fibrosis.

RESULTS

The expression levels of HGF and α-SMA (α-smooth muscle actin) were both significantly increased in UUO mice, while E-cadherin expression was significantly decreased, which were consistent with results of in vitro experiments. Overexpression of HGF remarkably decreased the protein and mRNA levels of α-SMA in fibrotic NRK-52E cells. After overexpression of HGF in UUO mice, α-SMA was remarkably downregulated, whereas E-cadherin was significantly upregulated. Further, results also demonstrated that HGF was upregulated and α-SMA was downregulated after p-SMAD3 knockdown in UUO mice.

CONCLUSIONS

HGF is highly expressed during renal interstitial fibrosis, which may suppress renal interstitial fibrosis by inhibiting the TGF-β1/SMAD signaling pathway.

[Determination of seven urinary metabolites of benzene, toluene and xylene by ultra-high performance liquid chromatography-triple quadrupole mass spectrometry]

Objective: To develop a method using ultra-high performance liquid chromatography-triple quadrupole mass spectrometry to determine the urinary metabolites of benzene, toluene and xylene. The selected metabolites are S-phenylmercapturic acid (S-PMA) , trans, trans-muconic acid (t, t-MA) , 8-hydroxy-2 deoxyguanosine (8-OHdG) , hippuric acid (HA) , 2-methylhippuric acid (2-MHA) , 3-methylhippuric acid (3-MHA) and 4-methylhippuric acid (4-MHA) . Methods: The urine sample was pretreated using methanol to precipitate the proteins. HSS T3 chromatographic column was used to separate the metabolites. The mass spectrometric acquisition was carried out using multiple reaction monitoring (MRM) after ionization with ESI source. External standard method was used for quantification. Results: All the standard curves showed good linear relation, and r of the seven metabolites was all above 0.999. The detection limits and quantitative limits of the seven metabolites were 0.01-500 ng/ml and 0.02-1 000 ng/ml (based on the actual dilution ratio) , respectively. The average spiked recoveries of four loadings ranged from 85.8% to 109.9%. The intra-day and inter-day precisions were 0.2%-4.5% and 0.6%-9.5%, respectively. The samples can be kept for at least 14 days at both 4 ℃ and -20 ℃. Conclusion: This method is simple, rapid and highly sensitive with low cost, and its accuracy, precision and stability can meet the daily test requirements. It can be applied for the determination of urinary S-PMA, t, t-MA, 8-OHdG, HA, 2-MHA, 3-MHA and 4-MHA for the occupational population exposed to benzene, toluene and xylene.

[Determination of Cortisol in Saliva by Liquid Chromatography Tandem Mass Spectrometry]

Objective: To establish a liquid chromatography tandem mass spectrometry method to determine the cortisol in saliva. Methods: Take 0.5 ml saliva sample into a 2 ml centrifuge tube, add excess sodium chloride and 1ml acetonitrile to it, then vortex for 3 min, centrifuge for 10 min at 15 000 r/min, and take 800 μl of the upper layer to another centrifuge tube. Finally, the sample was concentrated by a vacuum concentrator and brought to 200 μl with the initial mobile phase. Then, the sample was analyzed by liquid chromatography tandem mass spectrometry. The target compound was quantified by external standard curve method. Results: The linear range of the method was 0.02-5.00 ng/ml, r=0.999 9, the method limit of the detection was 0.002 ng/ml, the method limit of quantitative was 0.02 ng/ml, and the spiked recoveries were 89.60%-98.60%. The intra-assay precision was 1.90%-3.30%, and the inter-assay precision was 4.20%-9.00%; samples could be stored at -20 °C for at least 14 days. The determination of cortisol could not be interfered by other endogenous substances in the sample. Conclusion: The method is simple in pretreatment, high sensitivity, good reproducibility and good recovery, and it is suitable for the quantitative analysis of cortisol in saliva for normal and occupationally stressed populations.

[Analysis on voluntary blood donation and associated factors in men who have sex with men in 3 cities in China]

Objective: To assess the prevalence of blood donation and associated factors in men who have sex with men (MSM) in China. Methods: Our observational study was conducted between January and August, 2017 in 3 cities: Guangzhou, Shenzhen and Wuxi. Eligible participants were MSM (≥18 years old) who had either ≥2 male sex partners or unprotected anal sex with casual partners, or had been diagnosed with STI in the past 6 months. A self-completed tablet-based questionnaire was used to collect the information about MSM's socio-demographic characteristics, sexual behaviors and blood donation history. Results: A total of 603 MSM were enrolled in our study, including 302 in Guangzhou, 152 in Shenzhen and 149 in Wuxi, with a mean age of 27.9 years (SD=7.8). Overall, 29.2% (176/603) of the MSM reported a history of blood donation, and 33.1% (100/302)in Guangzhou, 27.6% (42/152) in Shenzhen and 22.8% (34/149) in Wuxi, the differences were not significant (χ(2)=6.421, P=0.093). Multivariate logistic regression analysis indicated that MSM had ever tested for HIV for ≥2 times in the past 12 months (vs. MSM tested for HIV one time, aOR=1.49, 95%CI: 1.08-2.19) or who had ever used gay dating app (vs. MSM who not used gay dating app, aOR=2.13, 95%CI: 1.12-4.44) were more likely to donate blood. Conclusions: Blood donation was common in MSM in China. Health education about blood donation in MSM should be strengthened to ensure the blood safety.

[Results of sentinel surveillance on men who have sex with men in Jilin province between 2010 and 2015]

Objective: To explore the HIV epidemic and related factors among MSM in Jilin province. Methods: During the implementation of sentinel surveillance program from 2010 to 2015, continuous cross-sectional studies were conducted to monitor the awareness of AIDS, sexual behavior, HIV and syphilis positive rates, with the sample size no less than 400 in each surveillance site. Results: From 2010 to 2015, a total of 7 823 MSM were involved in this study. The overall HIV prevalence among MSM was 5.4% (42/7 823), with an increasing trend during 2010 and 2015 (Trend test χ(2)=110.023, P<0.001). The rates of awareness on AIDS were higher than 90.0%. The proportion of consistent condom use was 27.0% (2 112/7 823) in the last 6 months, and significant differences were found in these years (χ(2)=234.038, P<0.001). Results from multivariate logistic regression analysis showed that the HIV infection related risk factors among MSM in Jilin province would include: residency from other provinces (aOR=1.797, 95%CI: 1.185-2.726), recruitment through internet (aOR=1.717, 95%CI: 1.332-2.215), diagnosed of having sexually transmitted diseases in the previous year (aOR=1.893, 95%CI: 1.356-2.643) and positive testing on syphilis (aOR=4.309, 95%CI: 3.097-5.995). And consistent condom uses in the last 6 months (aOR=0.387, 95%CI: 0.143-0.557), tested HIV in the last year (aOR=0.632, 95%CI: 0.375-0.891) were preventive factors. Conclusions: HIV prevalence was increasing among MSM in Jilin province, but both the proportion of consistent condom use and the former HIV testing rate were at a low level. Aggressive measurement including consistent condom use and periodical HIV testing among MSM was warranted.

Knowledge gaps and research priorities in the prevention and control of hepatitis E virus infection

Hepatitis E virus (HEV), family Hepeviridae, is a main cause of epidemic hepatitis in developing countries and sporadic and cluster cases of hepatitis in industrialized countries. There are an increasing number of reported cases in humans especially in industrialized countries, and there is a high potential for transboundary spread of zoonotic genotypes of the virus through the transport of pigs, pig products and by-products. Bloodborne transmission of the virus has been reported with a significant medical concern. To better coordinate HEV research and design better control measures of HEV infections in animals, a group of HEV experts reviewed the current knowledge on the disease and considered the existing disease control tools. It was concluded that there is a lack of in-depth information about the spread of the virus from pigs to humans. The role of animals other than pigs in the zoonotic transmission of the virus to humans and the extent of foodborne transmission are poorly understood. Factors involved in development of clinical disease such as infectious dose, susceptibility and virulence of virus strains need to be studied more extensively. However, such studies are greatly hindered by the absence of a broadly applicable, efficient and sensitive in vitro cell culture system for HEV. Diagnostic tools for HEV are available but need to be further validated, harmonized and standardized. Commercially available HEV vaccines for the control of HEV infection in animal populations are needed as such vaccines can minimize the zoonotic risk for humans. Anti-HEV drugs for treatment of HEV-infected patients need to be studied more extensively. The detailed expert review can be downloaded from the project website at http://www.discontools.eu/.

ICTV Virus Taxonomy Profile: Hepeviridae

The family Hepeviridae includes enterically transmitted small non-enveloped positive-sense RNA viruses. It includes the genera Piscihepevirus, whose members infect fish, and Orthohepevirus, whose members infect mammals and birds. Members of the genus Orthohepevirus include hepatitis E virus, which is responsible for self-limiting acute hepatitis in humans and several mammalian species; the infection may become chronic in immunocompromised individuals. Extrahepatic manifestations of Guillain–Barré syndrome, neuralgic amyotrophy, glomerulonephritis and pancreatitis have been described in humans. Avian hepatitis E virus causes hepatitis–splenomegaly syndrome in chickens. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the taxonomy of the Hepeviridae, which is available at www.ictv.global/report/hepeviridae.

Characterization of Seven Outbreaks of Hemorrhagic Hepatopathy Syndrome in Commercial Pullets Following the Administration of a Salmonella Enteritidis Bacterin in California

Between April 2013 and April 2015, seven flocks belonging to three different major commercial egg producers inCalifornia experienced a mild increase in mortality 2 to 3 wk after administration of Salmonella Enteritidis bacterins. Strains of chickens involved were H&N (flock A1, A2, B2, C1, C2, and C3) and Lohmann white (flock B1). Vaccination was administered individually through injection either in the breast muscles or subcutis in the legs between 11 and 18 wk of age in all flocks. Clinical signs ranged from inapparent to lameness, reluctance to walk, greenish diarrhea, and retching-like symptoms. The mortality ranged from 0.16% to 1.38% per week, with the highest peaks occurring usually 2 to 3 wk postvaccination, and then declined rapidly. Postmortem examinations revealed enlarged livers with disseminated hemorrhages and pale foci of necrosis. Also, severe extensive hemorrhages in the intestine, heart, and proventriculus were observed in a few birds. Various degrees of productive, exudative giant cell granulomatous myositis were observed invading deeply the muscles and subcutis at the site of vaccination. The myositis was always associated with optically empty vacuoles positive for neutral lipids by Oil Red O stain. Droplets of Oil Red O material were also noticed in the affected livers and intestines. Congo red stain highlighted the presence of amyloid in moderate to severe amounts in the breast muscles and moderate amounts in livers, spleens, and intestines. Salmonella antigens were detected in the injection sites and livers by immunohistochemical staining. No viruses or toxic substances were recovered from the liver, spleen, intestine, and pectoral muscles, and the few bacteria isolated were interpreted as secondary postmortem invaders. In addition, livers and bile tested for hepatitis E virus were negative by reverse-transcriptase polymerase chain reaction.

A porcine reproductive and respiratory syndrome virus candidate vaccine based on the synthetic attenuated virus engineering approach is attenuated and effective in protecting against homologous virus challenge

Current porcine reproductive and respiratory syndrome virus (PRRSV) vaccines sometimes fail to provide adequate immunity to protect pigs from PRRSV-induced disease. This may be due to antigenic differences among PRRSV strains. Rapid production of attenuated farm-specific homologous vaccines is a feasible alternative to commercial vaccines. In this study, attenuation and efficacy of a codon-pair de-optimized candidate vaccine generated by synthetic attenuated virus engineering approach (SAVE5) were tested in a conventional growing pig model. Forty pigs were vaccinated intranasally or intramuscularly with SAVE5 at day 0 (D0). The remaining 28 pigs were sham-vaccinated with saline. At D42, 30 vaccinated and 19 sham-vaccinated pigs were challenged with the homologous PRRSV strain VR2385. The experiment was terminated at D54. The SAVE5 virus was effectively attenuated as evidenced by a low magnitude of SAVE5 viremia for 1-5 consecutive weeks in 35.9% (14/39) of the vaccinated pigs, lack of detectable nasal SAVE5 shedding and failure to transmit the vaccine virus from pig to pig. By D42, all vaccinated pigs with detectable SAVE5 viremia also had detectable anti-PRRSV IgG. Anti-IgG positive vaccinated pigs were protected from subsequent VR2385 challenge as evidenced by lack of VR2385 viremia and nasal shedding, significantly reduced macroscopic and microscopic lung lesions and significantly reduced amount of PRRSV antigen in lungs compared to the non-vaccinated VR2385-challenged positive control pigs. The nasal vaccination route appeared to be more effective in inducing protective immunity in a larger number of pigs compared to the intramuscular route. Vaccinated pigs without detectable SAVE5 viremia did not seroconvert and were fully susceptible to VR2385 challenge. Under the study conditions, the SAVE approach was successful in attenuating PRRSV strain VR2385 and protected against homologous virus challenge. Virus dosage likely needs to be adjusted to induce replication and protection in a higher percentage of vaccinated pigs.

Experimental Reproduction of Postweaning Multisystemic Wasting Syndrome in Pigs by Dual Infection with Mycoplasma hyopneumoniae and Porcine Circovirus Type 2

The objectives of this study were to investigate the interactions between Mycoplasma hyopneumoniae and porcine circovirus type 2 (PCV2) and to establish a model for studying the pathogenesis of and testing intervention strategies for the control of PCV2-associated porcine respiratory disease complex (PRDC). Sixty-seven pigs were randomly assigned to four groups. Group 1 ( n = 17) pigs served as controls, group 2 ( n = 17) pigs were inoculated with M. hyopneumoniae, group 3 ( n = 17) pigs were dual infected with M. hyopneumoniae and PCV2, and group 4 ( n = 16) pigs were inoculated with PCV2. Pigs were inoculated intratracheally with M. hyopneumoniae at 4 weeks of age followed by intranasal inoculation with PCV2 at 6 weeks of age. Dual-infected pigs had moderate dyspnea, lethargy, and reduced weight gain. The overall severity of macroscopic lung lesions, PCV2-associated microscopic lesions in lung and lymphoid tissues, and the amount of PCV2-antigen associated with these lesions were significantly ( P < 0.05) higher in dual-infected pigs compared with all other groups. Four of 17 (23.5%) dual-infected pigs had decreased growth rate and severe lymphoid depletion and granulomatous lymphadenitis associated with high amounts of PCV2-antigen consistent with postweaning multisystemic wasting syndrome (PMWS). PCV2-antigen in lung tissue was most often associated with M. hyopneumoniae-induced peribronchial lymphoid hyperplasia, suggesting that this is an important site for PCV2 replication in the lung. This study indicates that M. hyopneumoniae potentiates the severity of PCV2-associated lung and lymphoid lesions, increases the amount and prolongs the presence of PCV2-antigen, and increases the incidence of PMWS in pigs.

Serological evidence for a hepatitis e virus-related agent in goats in the United States

Hepatitis E virus (HEV) causes an important public health disease in many developing countries and is also endemic in some industrialized countries. In addition to humans, strains of HEV have been genetically identified from pig, chicken, rat, mongoose, deer, rabbit and fish. While the genotypes 1 and 2 HEV are restricted to humans, the genotypes 3 and 4 HEV are zoonotic and infect humans and other animal species. As a part of our ongoing efforts to search for potential animal reservoirs for HEV, we tested goats from Virginia for evidence of HEV infection and showed that 16% (13/80) of goat sera from Virginia herds were positive for IgG anti-HEV. Importantly, we demonstrated that neutralizing antibodies to HEV were present in selected IgG anti-HEV positive goat sera. Subsequently, in an attempt to genetically identify the HEV-related agent from goats, we conducted a prospective study in a closed goat herd with known anti-HEV seropositivity and monitored a total of 11 kids from the time of birth until 14 weeks of age for evidence of HEV infection. Seroconversion to IgG anti-HEV was detected in seven of the 11 kids, although repeated attempts to detect HEV RNA by a broad-spectrum nested RT-PCR from the faecal and serum samples of the goats that had seroconverted were unsuccessful. In addition, we also attempted to experimentally infect laboratory goats with three well-characterized mammalian strains of HEV but with no success. The results indicate that a HEV-related agent is circulating and maintained in the goat population in Virginia and that the goat HEV is likely genetically very divergent from the known HEV strains.

Co-infection of porcine dendritic cells with porcine circovirus type 2a (PCV2a) and genotype II porcine reproductive and respiratory syndrome virus (PRRSV) induces CD4(+)CD25(+)FoxP3(+) T cells in vitro

Porcine circovirus associated disease (PCVAD) is currently one of the most economically important diseases in the global swine industry. Porcine circovirus type 2 (PCV2) is the primary causative agent, however co-infection with other swine pathogens such as porcine reproductive and respiratory syndrome virus (PRRSV) is often required to induce the full spectrum of clinical PCVAD. While the specific mechanisms of viral co-infection that lead to clinical disease are not fully understood, immune modulation by the co-infecting viruses likely plays a critical role. We evaluated the ability of dendritic cells (DC) infected with PRRSV, PCV2, or both to induce regulatory T cells (T_regs) in vitro. DCs infected with PCV2 significantly increased CD4⁺CD25⁺FoxP3⁺ T_regs (p < 0.05) and DCs co-infected with PRRSV and PCV2 induced significantly higher numbers of T_regs than with PCV2 alone (p < 0.05). Cytokine analysis indicated that the induction of T_regs by co-infected DCs may be dependent on TGF-β and not IL-10. Our data support the immunomodulatory role of PCV2/PRRSV co-infection in the pathogenesis of PCVAD, specifically via T_reg-mediated immunosuppression.

Immunogenicity study of plant-made oral subunit vaccine against porcine reproductive and respiratory syndrome virus (PRRSV)

Currently, killed-virus and modified-live PRRSV vaccines are used to control porcine reproductive and respiratory syndrome disease (PRRS). However, very limited efficacy of killed-virus vaccines and serious safety concerns for modified-live virus vaccines demand the development of novel PRRSV vaccines. In this report, we investigated the possibility of using transgenic plants as a cost-effective and scalable system for production and delivery of a viral protein as an oral subunit vaccine against PRRSV. Corn calli were genetically engineered to produce PRRSV viral envelope-associated M protein. Both serum and intestine mucosal antigen-specific antibodies were induced by oral administration of the transgenic plant tissues to mice. In addition, serum and mucosal antibodies showed virus neutralization activity. The neutralization antibody titers after the final boost reached 6.7 in serum and 3.7 in fecal extracts, respectively. A PRRSV-specific IFN-γ response was also detected in splenocytes of vaccinated animals. These results demonstrate that transgenic corn plants are an efficient subunit vaccine production and oral delivery system for generation of both systemic and mucosal immune responses against PRRSV.

Vaccination with inactivated or live-attenuated chimeric PCV1-2 results in decreased viremia in challenge-exposed pigs and may reduce transmission of PCV2

The objectives were to determine transmissibility of PCV2 to naïve contact pigs 140 days after infection of resident pigs and the benefit of vaccination with live-attenuated or inactivated chimeric PCV2 vaccines on chronic PCV2 infection. Twelve 6-week old PCV2 naïve pigs were randomly divided into four groups of three pigs: negative controls, positive controls, and pigs vaccinated with either a live-attenuated or inactivated chimeric PCV1-2 vaccine. All animals were bled weekly and tested for anti-PCV2 antibodies and PCV2 and PCV1-2 DNA and all groups except negative controls were challenged at 10 weeks. Two pigs vaccinated with the live PCV2 vaccine were PCV1-2 viremic at a single observation point. Both vaccine regimens induced an anti-PCV2 antibody response which was detected sooner and reached a higher level with the commercial inactivated vaccine. Both vaccines significantly decreased the concentration and duration of PCV2 viremia compared to the positive controls. PCV2 DNA was detected in lymphoid tissues of 1/3 pigs in the live-attenuated vaccine group and 3/3 positive control pigs. Three, 2-week old, PCV2 naïve contact pigs were comingled with each group at 168 days post-vaccination or 140 days post-challenge. After seven days of co-housing, the resident pigs were removed and the contact pigs remained for six weeks. Evidence of chimeric PCV1-2 vaccine or PCV2 challenge virus transmission to naïve contact pigs was lacking in all groups. The results of this study suggest that 140-day closure of a small pig population in a controlled environment may result in stabilization and elimination of PCV2.

Emerging and re-emerging swine viruses

In the past two decades or so, a number of viruses have emerged in the global swine population. Some, such as porcine reproductive and respiratory syndrome virus (PRRSV) and porcine circovirus type 2 (PCV2), cause economically important diseases in pigs, whereas others such as porcine torque teno virus (TTV), now known as Torque teno sus virus (TTSuV), porcine bocavirus (PBoV) and related novel parvoviruses, porcine kobuvirus, porcine toroviruses (PToV) and porcine lymphotropic herpesviruses (PLHV), are mostly subclinical in swine herds. Although some emerging swine viruses such as swine hepatitis E virus (swine HEV), porcine endogenous retrovirus (PERV) and porcine sapovirus (porcine SaV) may have a limited clinical implication in swine health, they do pose a potential public health concern in humans due to zoonotic (swine HEV) or potential zoonotic (porcine SaV) and xenozoonotic (PERV, PLHV) risks. Other emerging viruses such as Nipah virus, Bungowannah virus and Menangle virus not only cause diseases in pigs but some also pose important zoonotic threat to humans. This article focuses on emerging and re-emerging swine viruses that have a limited or uncertain clinical and economic impact on pig health. The transmission, epidemiology and pathogenic potential of these viruses are discussed. In addition, the two economically important emerging viruses, PRRSV and PCV2, are also briefly discussed to identify important knowledge gaps.

Differences in capabilities of different enzyme immunoassays to detect anti-hepatitis E virus immunoglobulin G in pigs infected experimentally with hepatitis E virus genotype 3 or 4 and in pigs with unknown exposure

Hepatitis E virus (HEV), a major cause of acute viral hepatitis in humans in many developing countries, is highly prevalent in the pig population worldwide. The objective of this study was to assess the capability of three porcine prototypes of a human enzyme-linked immunosorbent assay (ELISA), an in-house ELISA and a line-immunoassay (LIA) to detect anti-HEV antibodies in pigs infected experimentally with HEV (n = 57), known to be negative for HEV infection (n = 27), or with unknown exposure to HEV infection (field samples, n = 90). All 27 samples from non-infected pigs were negative with all five assays. The earliest detection of anti-HEV antibodies occurred at 14 days post-inoculation (dpi) with four of five assays. From 42 dpi, all samples from infected pigs were detected correctly as anti-HEV positive. Kappa analysis demonstrated substantial agreement among tests (0.62-1.00) at 14 dpi and complete agreement (1.00) at 56 dpi. The overall area under the curve for all quantitative tests as determined by receiver operator characteristic analysis ranged from 0.794 to 0.831 indicating moderate accuracy. The results showed that all five assays can detect anti-HEV IgG antibodies accurately in pigs infected experimentally with HEV. In field samples, a higher prevalence of anti-HEV IgG was found in breeding herds than in growing pigs (100% versus 66.7-93.9%). These serological assays should be very useful in veterinary diagnostic labs for HEV diagnosis in swine.

Expression of the putative ORF1 capsid protein of Torque teno sus virus 2 (TTSuV2) and development of Western blot and ELISA serodiagnostic assays: correlation between TTSuV2 viral load and IgG antibody level in pigs

Porcine Torque teno virus (TTV) has a single-stranded circular DNA genome and is currently classified into a new genus Iotatorquevirus with two species in a newly established family Anelloviridae. Viral DNA of both porcine TTV species (TTSuV1 and TTSuV2) has a high prevalence in both healthy and diseased pigs worldwide and multiple infections of TTSuV with distinct genotypes or subtypes of the same species has been documented in the United States and in Europe. However, the prevalence of specific TTSuV antibodies in pigs remains unknown. In this study, the putative ORF1 capsid protein from TTSuV2 isolate PTTV2c-VA was expressed in Escherichia coli. The purified recombinant ORF1 protein was used as the antigen for the development of Western blot and indirect ELISA to detect TTSuV2-specific IgG antibodies in pig sera. The results revealed a relatively high rate of seropositivity to TTSuV2 in conventional pigs from different sources but not in gnotobiotic pigs. Overall, pigs with undetectable TTSuV2 viral load were more likely to have a lower anti-TTSuV2 antibody level. An analysis of 10 conventional pigs during a 2-month period showed that decreased viral loads or presumed virus clearance were associated with elevated anti-ORF1 IgG antibody levels. Interestingly, porcine circovirus associated disease (PCVAD)-affected pigs had a significantly lower level of TTSuV2 antibody than PCVAD-unaffected pigs (p<0.01). This is the first study to establish essential serodiagnostic tools for investigation of TTSuV seroprevalence and infection dynamics, which will help elucidate the potential pathogenicity of TTSuV infection in pigs.

Shedding and infection dynamics of porcine circovirus type 2 (PCV2) after experimental infection

The objective of this study was to determine the amount and infectivity of porcine circovirus type 2 (PCV2) shed in nasal, oral and fecal secretions following experimental infection. Fecal, oral and nasal swabs and blood were collected at regular intervals until 69 days post-inoculation (DPI) from five PCV2-experimentally inoculated pigs (Trial 1). To assess the infectivity of the PCV2 present in excretions, secretions, and on a hypodermic needle, 26 PCV2-naïve pigs (Trial 2) were inoculated with various samples obtained from Trial 1 pigs. In Trial 1, PCV2 DNA was detected in all sample types by 69 DPI. There were no differences in the amount of PCV2 DNA present in different sample types over time. In Trial 2, intraperitoneal inoculation with contaminated fecal, nasal and oral samples; intranasal inoculation of nasal secretions; and feces fed to naïve animals resulted in viremia and seroconversion. Viremia and microscopic lesions were noted in one animal injected using a contaminated needle. In conclusion, experimental PCV2 exposure results in a long term infection. PCV2 is shed in similar amounts by nasal, oral and fecal routes and is infectious to naïve pigs confirming that multiple routes of transmission are likely important in spread of PCV2 between pigs.

The emergence of genotypes 3 and 4 hepatitis E virus in swine and humans: a phylogenetic perspective

To investigate whether there is any phylogenetic evidence to support the hypothesis that swine is the natural host of HEV genotypes 3 and 4, Bayesian analysis of 80 full-length genomic sequences of HEV was performed. The results showed that the strains of genotypes 3 and 4 from swine are paraphyletic with regard to strains of human origin, which are thus phylogenetically nested among the swine strains. Recognition of HEV genotypes 3 and 4 as viruses from swine or swine HEV can provide an evolutionary explanation to the observation of cross-species infection by genotypes 3 and 4 HEV.

Fate and transport of zoonotic, bacterial, viral, and parasitic pathogens during swine manure treatment, storage, and land application

Members of the public are always somewhat aware of foodborne and other zoonotic pathogens; however, recent illnesses traced to produce and the emergence of pandemic H1N1 influenza virus have increased the scrutiny on all areas of food production. The Council for Agricultural Science and Technology has recently published a comprehensive review of the fate and transport of zoonotic pathogens that can be associated with swine manure. The majority of microbes in swine manure are not zoonotic, but several bacterial, viral, and parasitic pathogens have been detected. Awareness of the potential zoonotic pathogens in swine manure and how treatment, storage, and handling affect their survival and their potential to persist in the environment is critical to ensure that producers and consumers are not at risk. This review discusses the primary zoonotic pathogens associated with swine manure, including bacteria, viruses, and parasites, as well as their fate and transport. Because the ecology of microbes in swine waste is still poorly described, several recommendations for future research are made to better understand and reduce human health risks. These recommendations include examination of environmental and ecological conditions that contribute to off-farm transport and development of quantitative risk assessments.

Purification of porcine reproductive and respiratory syndrome virus from cell culture using ultrafiltration and heparin affinity chromatography

Porcine reproductive and respiratory syndrome (PRRS) virus is the causative agent of the most significant infectious disease currently affecting the swine industry worldwide. Density gradient ultracentrifugation remains the most commonly used method for porcine reproductive and respiratory syndrome virus (PRRSV) purification. However, this technique has notable drawbacks including long processing time and limited processing volume in each run. To overcome these limitations, a scalable process was developed. PRRSV propagated in MARC-145 was released by three freeze/thaw cycles. After a low speed centrifugation step, the virus particles in the supernatant were concentrated twice by an ultrafiltration step. The ultrafiltration step concentrated the virions effectively with no detectable loss while some cultural/cellular proteins were removed. The virions in the ultrafiltration retentate were then applied to a heparin affinity column on a fast performance liquid chromatography unit. The combined ultrafiltration and heparin affinity chromatography process removed more than 96% of cellular and medium proteins. During a stepwise elution strategy, the viral particles were eluted at two separate peaks recovering 27.5% and 25.4% of viral particles loaded onto the column with a purity of 194 and 3917 particles/microg protein, respectively.

Recent advances in Hepatitis E virus

Hepatitis E virus (HEV), the causative agent of hepatitis E, belongs to the family Hepeviridae. At least four major genotypes of HEV have been recognized: genotypes 1 and 2 are restricted to humans and associated with epidemics in developing countries, whereas genotypes 3 and 4 are zoonotic and infect humans and several other animals in both developing and industrialized countries. Besides humans, strains of HEV have been genetically identified from swine, chickens, sika deer, mongeese, and rabbits. The genome of HEV consists of three open reading frames (ORFs): ORF1 codes for nonstructural proteins, ORF2 codes for capsid protein, and ORF3 codes for a small multifunctional protein. The ORF2 and ORF3 proteins are translated from a single bicistronic mRNA and overlap each other but neither overlaps ORF1. The recent determination of the 3D crystal structure of the HEV capsid protein should facilitate the development of vaccines and antivirals. The identification and characterization of animal strains of HEV from pigs and chickens and the demonstrated ability of cross-species infection by swine HEV raise public health concerns for zoonosis. Accumulating evidence indicated that hepatitis E is a zoonotic disease and pigs and more likely other animal species are reservoirs for HEV. This article provides an overview of the recent advances in hepatitis E and its causative agent, including nomenclature and genomic organization, gene expression and functions, 3D structure of the virions, changing perspectives on higher mortality during pregnancy and chronic hepatitis E, animal reservoirs, zoonotic risk, food safety, and novel animal models.

Wild boars as sources for infectious diseases in livestock and humans

Wild boars (Sus scrofa) are indigenous in many countries in the world. These free-living swine are known reservoirs for a number of viruses, bacteria and parasites that are transmissible to domestic animals and humans. Changes of human habitation to suburban areas, increased use of lands for agricultural purposes, increased hunting activities and consumption of wild boar meat have increased the chances of exposure of wild boars to domestic animals and humans. Wild boars can act as reservoirs for many important infectious diseases in domestic animals, such as classical swine fever, brucellosis and trichinellosis, and in humans, diseases such as hepatitis E, tuberculosis, leptospirosis and trichinellosis. For examples, wild boars are reservoirs for hepatitis E virus, and cluster cases of hepatitis E have been reported in Japan of humans who consumed wild boar meat. In Canada, an outbreak of trichinellosis was linked to the consumption of wild boar meat. The incidence of tuberculosis owing to Mycobacterium bovis has increased in wild boars, thus posing a potential concern for infections in livestock and humans. It has also been documented that six hunters contracted Brucella suis infections from wild swine in Florida. This article discusses the prevalence and risk of infectious agents in wild boars and their potential transmission to livestock and humans.

Multiple infection of porcine Torque teno virus in a single pig and characterization of the full-length genomic sequences of four U.S. prototype PTTV strains: implication for genotyping of PTTV

Porcine Torque teno virus (PTTV) was recently shown to partially contribute to the experimental induction of porcine dermatitis and nephropathy syndrome and postweaning multisystemic wasting syndrome in pigs in the United States. We report here the identification of four distinct full-length genomic sequences of PTTV strains from a single pig in Virginia. Detailed analyses of the genomic organization, the degree of variability and the characteristics of conserved nucleotide and amino acid motifs of PTTV were conducted. The results showed that these four prototype U.S. strains of PTTV identified from the same pig represent distinct genotypes or subtypes and a revised classification system for PPTV is subsequently proposed. This is the first study documenting multiple PTTV infections with distinct genotypes or subtypes in a single pig. The identification of novel PTTV strains from pigs in the United States also pave the way for future disease characterization and genotyping of PTTV.

Persistent infection of turkeys with an avirulent strain of turkey hemorrhagic enteritis virus

The Virginia avirulent strain (VAS) of turkey hemorrhagic enteritis virus (THEV), which is commonly used in live vaccines for commercial turkeys, was studied to determine characteristics of infection. It has been observed that turkeys infected with the VAS maintain protective antibody levels in excess of 20 wk postvaccination. It is theorized that this immune response is modulated by either a persistent or latent infection. A series of studies have been undertaken to determine changes in virus location and serology over time. A trial was also conducted to evaluate the effect of corticosteroid administration on viral recrudescence, and an attempt was made to isolate live virus from tissues of birds 10 wk postinfection (pi). Antibody titers were determined by enzyme-linked immunosorbent assay, and PCR was used to detect viral DNA. Histopathology was performed on formalin-fixed paraffinized tissues. Viral DNA was detected in various tissues through 15 wk pi in the presence of high antibody titers. Viral DNA was detected at 3-5 days pi in the spleens of susceptible turkeys inoculated with tissues collected from infected birds at 10 wk pi. It is unknown whether the viral DNA is associated with live virus or rather is the result of persistent maintenance of the viral genome within lymphoid/macrophage target cells. Future studies will test for viral RNA in order to confirm the presence of replicating THEV. Regardless of the actual status of the THEV DNA detected at 10-15 wk pi, it is clear that THEV does not cause a simple acute infection. The characteristics of THEV infection are identical to the nonlytic persistent infections seen in human adenoviruses, and therefore THEV may serve as a model for the study of virus-cell interactions mediating persistence.

Porcine circovirus type 2 and porcine circovirus-associated disease

Porcine circovirus type 2 (PCV2) belongs to the viral family Circoviridae and to the genus Circovirus. Circoviruses are small, single-stranded nonenveloped DNA viruses that have an unsegmented circular genome. PCV2 is the primary causative agent of several syndromes collectively known as porcine circovirus-associated disease (PCVAD). Many of the syndromes associated with PCVAD are a result of coinfection with PCV2 virus and other agents such as Mycoplasma and porcine reproductive and respiratory syndrome virus. PCV2 infection is present in every major swine-producing country in the world, and the number of identified cases of PCVAD is rapidly increasing. In the United States, the disease has cost producers an average of 3-4 dollars per pig with peak losses ranging up to 20 dollars per pig. The importance of this disease has stimulated investigations aimed at identifying risk factors associated with infection and minimizing these risks through modified management practices and development of vaccination strategies. This paper provides an overview of current knowledge relating to PCV2 and PCVAD with an emphasis on information relevant to the swine veterinarian.

The open reading frame 3 (ORF3) of porcine circovirus type 2 (PCV2) is dispensable for virus infection but evidence of reduced pathogenicity is limited in pigs infected by an ORF3-null PCV2 mutant

Porcine circovirus type 2 (PCV2) is the primary causative agent of porcine circovirus-associated diseases (PCVAD) in pigs. The open reading frame (ORF) 3 of PCV2 reportedly induces apoptosis and is associated with PCV2 pathogenicity. In this study, we first created an ORF3-null PCV2 mutant (muPCV2) by site-directed mutagenesis and demonstrated that the dimerized plasmid DNA of muPCV2 clone is infectious when injected intramuscularly (I.M.) into pigs. Subsequently, by using a well-characterized pig model we compared the pathogenicity of the muPCV2 and the wildtype PCV2. Thirty-one pigs were divided into 3 groups of 11, 10, and 10 each: group 1 pigs were each inoculated I.M. with PBS buffer as negative controls, group 2 pigs each with 200 microg of muPCV2 infectious DNA clone, and group 3 pigs each with 200 microg of wildtype PCV2 infectious DNA clone. Blood was collected prior to inoculation and weekly thereafter, and tested for PCV2 antibodies by ELISA and serum viral DNA loads by quantitative PCR. All pigs were necropsied at 35 days post-inoculation. The results showed that pigs inoculated with muPCV2 had a delayed seroconversion and lower serum viral load. However, there was no significant difference in the average scores of the histological or gross lesions or the amount of PCV2-specific antigen in tissues between wildtype PCV2- and muPCV2-inoculated groups. Thus, the data from this study do not fully support the conclusion of a previous report regarding PCV2 attenuation by abrogation of ORF3 although the results did show that ORF3 is dispensable for PCV2 replication in pigs.

Effect of natural or vaccine-induced porcine circovirus type 2 (PCV2) immunity on fetal infection after artificial insemination with PCV2 spiked semen

The objectives of this study were to determine if vaccination against porcine circovirus type 2 (PCV2) or previous PCV2 infection of the dam are sufficient to prevent fetal infection when dams are artificially inseminated with PCV2-spiked semen. Nine sows (Sus domestica) were allocated into three groups of three dams each: The PCV2 naïve negative control Group 1 was artificially inseminated with extended PCV2 DNA negative semen during estrus, whereas the extended semen used in the vaccinated Group 2 (PCV2 vaccine was given 8 wk before insemination) and PCV2-exposed Group 3 (infected with PCV2 12 wk before insemination) was spiked with 5 mL of PCV2 inoculum with a titer of 10(4.2) tissue culture infectious dose (TCID(50)) per milliliter at each breeding. The dams in the vaccinated and PCV2-exposed groups were positive for PCV2 antibody but negative for PCV2 DNA in serum at the time of insemination. Three negative control dams, two vaccinated dams, and three dams with previous PCV2 exposure became pregnant and maintained pregnancy to term. After artificial insemination, viremia was detected in one of three vaccinated dams and in two of three dams with previous PCV2 exposure. At farrowing, PCV2 infection was not detected in any piglets or fetuses expelled from the negative control dams or from dams with previous PCV2 exposure. In litters of the vaccinated dams, 15 of 24 live-born piglets were PCV2 viremic at birth, with 6 of 26 fetuses having detectable PCV2 antigen in tissues. In conclusion, vaccine-induced immunity did not prevent fetal infection in this sow model using semen spiked with PCV2.

Comparative pathogenesis in specific-pathogen-free chickens of two strains of avian hepatitis E virus recovered from a chicken with Hepatitis-Splenomegaly syndrome and from a clinically healthy chicken

Avian hepatitis E virus (avian HEV) is the primary causative agent of Hepatitis-Splenomegaly (HS) syndrome in chickens. Recently, a genetically unique strain of avian HEV, designated avian HEV-VA, was recovered from healthy chickens in Virginia. The objective of this study was to experimentally compare the pathogenicity of the prototype strain recovered from a chicken with HS syndrome and the avian HEV-VA strain in specific-pathogen-free chickens. An infectious stock of the avian HEV-VA strain was first generated and its infectivity titer determined in chickens. For the comparative pathogenesis study, 54 chickens of 6-week-old were assigned to 3 groups of 18 chickens each. The group 1 chickens were each intravenously inoculated with 5x10(2.5) 50% chicken infectious dose of the prototype strain. The group 2 received the same dose of the avian HEV-VA strain, and the group 3 served as negative controls. Six chickens from each group were necropsied at 2, 3 and 4 weeks post-inoculation (wpi). Most chickens in both inoculated groups seroconverted by 3wpi, and the mean anti-avian HEV antibody titers were higher for the prototype strain group than the avian HEV-VA strain group. There was no significant difference in the patterns of viremia and fecal virus shedding. Blood analyte profiles did not differ between treatment groups except for serum creatine phosphokinase levels which were higher for prototype avian HEV group than avian HEV-VA group. The hepatic lesion score was higher for the prototype strain group than the other two groups. The results indicated that the avian HEV-VA strain is only slightly attenuated compared to the prototype strain, suggesting that the full spectrum of HS syndrome is likely associated with other co-factors.

Identification and characterization of a porcine monocytic cell line supporting porcine reproductive and respiratory syndrome virus (PRRSV) replication and progeny virion production by using an improved DNA-launched PRRSV reverse genetics system

In this study, an improved DNA-launched (plasmid DNA transfection-based) reverse genetics system with reduced cost and labor was developed for porcine reproductive and respiratory syndrome virus (PRRSV) by introduction of ribozyme elements at both termini of the viral genomic cDNA that were placed under the control of a eukaryotic hybrid promoter. The rescue efficacy of PRRSV with this system was approximately 10-50-fold higher than the in vitro-transcribed RNA-based system and the traditional DNA-launched system without the engineered ribozyme elements, as determined by reporter GFP level in transfected cells and the peak titer of the recovery virus. By using this new reverse genetics system, we identified and characterized a porcine monocytic cell line, 3D4/31, capable of supporting PRRSV replication, progeny virion production, and attachment on the cell surface. The establishment of this improved reverse genetic system and the identification of a porcine monocytic cell line supporting PRRSV replication will aid future studies of host-virus interaction of PRRSV.

Identification of a porcine DC-SIGN-related C-type lectin, porcine CLEC4G (LSECtin), and its order of intron removal during splicing: comparative genomic analyses of the cluster of genes CD23/CLEC4G/DC-SIGN among mammalian species

Human CLEC4G (previously named LSECtin), DC-SIGN, and L-SIGN are three important C-type lectins capable of mediating viral and bacterial pathogen recognitions. These three genes, together with CD23, form a lectin gene cluster at chromosome 19p13.3. In this study, we have experimentally identified the cDNA and the gene encoding porcine CLEC4G (pCLEC4G). Full-length pCLEC4G cDNA encodes a type II transmembrane protein of 290 amino acids. pCLEC4G gene has the same gene structure as the human and the predicted bovine, canis, mouse and rat CLEC4G genes with nine exons. A multi-species-conserved site at the extreme 3'-untranslated region of CLEC4G mRNAs was predicted to be targeted by microRNA miR-350 in domesticated animals and by miR-145 in primates, respectively. We detected pCLEC4G mRNA expression in liver, lymph node and spleen tissues. We also identified a series of sequential intermediate products of pCLEC4G pre-mRNA during splicing from pig liver. The previously unidentified porcine CD23 cDNA containing the complete coding region was subsequently cloned and found to express in spleen, thymus and lymph node. Furthermore, we compared the chromosomal regions syntenic to the human cluster of genes CD23/CLEC4G/DC-SIGN/L-SIGN in representative mammalian species including primates, domesticated animal, rodents and opossum. The L-SIGN homologues do not exist in non-primates mammals. The evolutionary processes of the gene cluster, from marsupials to primates, were proposed based upon their genomic structures and phylogenetic relationships.

Hepatitis E virus: animal reservoirs and zoonotic risk

Hepatitis E virus (HEV) is a small, non-enveloped, single-strand, positive-sense RNA virus of approximately 7.2kb in size. HEV is classified in the family Hepeviridae consisting of four recognized major genotypes that infect humans and other animals. Genotypes 1 and 2 HEV are restricted to humans and often associated with large outbreaks and epidemics in developing countries with poor sanitation conditions, whereas genotypes 3 and 4 HEV infect humans, pigs and other animal species and are responsible for sporadic cases of hepatitis E in both developing and industrialized countries. The avian HEV associated with Hepatitis-Splenomegaly syndrome in chickens is genetically and antigenically related to mammalian HEV, and likely represents a new genus in the family. There exist three open reading frames in HEV genome: ORF1 encodes non-structural proteins, ORF2 encodes the capsid protein, and the ORF3 encodes a small phosphoprotein. ORF2 and ORF3 are translated from a single bicistronic mRNA, and overlap each other but neither overlaps ORF1. Due to the lack of an efficient cell culture system and a practical animal model for HEV, the mechanisms of HEV replication and pathogenesis are poorly understood. The recent identification and characterization of animal strains of HEV from pigs and chickens and the demonstrated ability of cross-species infection by these animal strains raise potential public health concerns for zoonotic HEV transmission. It has been shown that the genotypes 3 and 4 HEV strains from pigs can infect humans, and vice versa. Accumulating evidence indicated that hepatitis E is a zoonotic disease, and swine and perhaps other animal species are reservoirs for HEV. A vaccine against HEV is not yet available.

Reproductive failure experimentally induced in sows via artificial insemination with semen spiked with porcine circovirus type 2

Porcine circovirus type 2 (PCV2) is associated with reproductive failure in female pigs. However, the association of PCV2-positive semen in the pathogenesis has not been elucidated. The objectives of this study were to determine whether semen spiked with PCV2 causes infection in PCV2-naïve, mature female pigs and whether delivery of PCV2 via artificial insemination causes reproductive failure or fetal infection. Nine sows were randomly allocated into 3 groups of 3 sows each and artificially inseminated with PCV2 DNA-negative semen (group 1), PCV2 DNA-negative semen spiked with PCV2a (group 2), or PCV2b (group 3). All sows in groups 2 and 3 developed PCV2 viremia 7 to 14 days after insemination. None of the group 2 sows became pregnant, whereas all group 3 sows (3/3) farrowed at the expected date. At parturition, presuckle serum samples were collected, and live-born piglets, stillborn fetuses, and mummified fetuses were necropsied. All live-born piglets (n = 8) in group 3 were PCV2 viremic at birth. Stillborn fetuses (n = 2) had gross lesions of congestive heart failure. Mummified fetuses (n = 25) varied in crown-rump length from 7 to 27 cm, indicating fetal death between 42 and 105 days of gestation. PCV2 antigen was detected in the myocardium by immunohistochemistry of 7/8 (88%) live-born piglets, 2/2 (100%) of the stillborn fetuses, and 25/25 (100%) of the mummified fetuses. In addition, 4/25 mummified fetuses had PCV2 antigen associated with smooth muscle cells and fibroblasts. The results of this study indicate that intrauterine administration of PCV2 causes reproductive failure in naïve sows.

Difference in severity of porcine circovirus type two-induced pathological lesions between Landrace and Pietrain pigs

Anecdotal information from the field suggests that there are host genetic differences in susceptibility to porcine circovirus type 2 (PCV2) associated disease among Landrace and Pietrain breeds. The objective of this study was to determine if a difference exists in PCV2 susceptibility between Landrace and Pietrain pigs under experimental conditions. Thirty-nine Landrace pigs and 39 Pietrain pigs were blocked by breed, sire, dam, and litter and randomly divided into the following 4 groups: Landrace noninoculated negative control (Landrace-NEG; n = 13), Pietrain noninoculated negative control (Pietrain-NEG; n = 13), Landrace-PCV2 (n = 26; Landrace), and Pietrain-PCV2 (n = 26; Pietrain). After waning of passively acquired anti-PCV2 antibodies, Landrace-PCV2 and Pietrain-PCV2 groups were inoculated with PCV2 isolate ISU-40895. The Landrace-NEG and Pietrain-NEG groups were housed in a separate room, remained noninoculated, and served as negative controls. All pigs in all groups were necropsied at 21 d post PCV2-inoculation. Onset of seroconversion and concentrations of anti-PCV2-IgM, anti-PCV2-IgG, and anti-PCV2 neutralizing antibodies were similar in Landrace-PCV2 and Pietrain-PCV2 groups. Furthermore, the amount of PCV2 DNA and cytokine concentrations in serum and plasma samples were not different between the 2 PCV2-inoculated groups. The severity of PCV2-associated microscopic lesions was different between Landrace and Pietrain pigs; Landrace-PCV2 pigs had significantly (P < 0.05) more severe lymphoid lesions than the Pietrain-PCV2 pigs. Although the pigs originated from the same farm where their dams were commingled, passively acquired anti-PCV2-antibodies waned in Pietrain pigs by approximately 12 wk of age, whereas the majority of the Landrace pigs remained PCV2 seropositive until 18 wk of age and beyond. The results from this study indicate that a genetic difference exists between these 2 breeds of pigs in susceptibility to PCV2-associated lesions.

Cross-species infection of specific-pathogen-free pigs by a genotype 4 strain of human hepatitis E virus

Hepatitis E virus (HEV) is an important pathogen. The animal strain of HEV, swine HEV, is related to human HEV. The genotype 3 swine HEV can infect humans and genotype 3 human HEV can infect pigs. The genotype 4 swine and human HEV strains are genetically related, but it is unknown whether genotype 4 human HEV can infect pigs. A swine bioassay was utilized in this study to determine whether genotype 4 human HEV can infect pigs. Fifteen, 4-week-old, specific-pathogen-free pigs were divided into three groups of five each. Group 1 pigs were each inoculated intravenously with PBS buffer as negative controls, group 2 pigs similarly with genotype 3 human HEV (strain US-2), and group 3 pigs similarly with genotype 4 human HEV (strain TW6196E). Serum and fecal samples were collected at 0, 7, 14, 21, 28, 35, 42, 49, and 56 days postinoculation (dpi) and tested for evidence of HEV infection. All pigs were necropsied at 56 dpi. As expected, the negative control pigs remained negative. The positive control pigs inoculated with genotype 3 human HEV all became infected as evidenced by detection of HEV antibodies, viremia and fecal virus shedding. All five pigs in group 3 inoculated with genotype 4 human HEV also became infected: fecal virus shedding and viremia were detected variably from 7 to 56 dpi, and seroconversion occurred by 28 dpi. The data indicated that genotype 4 human HEV has an expanded host range, and the results have important implications for understanding the natural history and zoonosis of HEV.

Identification of two neutralization epitopes on the capsid protein of avian hepatitis E virus

Avian hepatitis E virus (avian HEV) is genetically and antigenically related to human HEV, the causative agent of hepatitis E. To identify the neutralizing epitopes on the capsid (ORF2) protein of avian HEV, four mAbs (7B2, 1E11, 10A2 and 5G10) against recombinant avian HEV ORF2 protein were generated. mAbs 7B2, 1E11 and 10A2 blocked each other for binding to avian HEV ORF2 protein in a competitive ELISA, whereas 5G10 did not block the other mAbs, suggesting that 7B2, 1E11 and 10A2 recognize the same or overlapping epitopes and 5G10 recognizes a different one. The epitopes recognized by 7B2, 1E11 and 10A2, and by 5G10 were mapped by Western blotting between aa 513 and 570, and between aa 476 and 513, respectively. mAbs 1E11, 10A2 and 5G10 were shown to bind to avian HEV particles in vitro, although only 5G10 reacted to viral antigens in transfected LMH cells. To assess the neutralizing activities of the mAbs, avian HEV was incubated in vitro with each mAb before inoculation into specific-pathogen-free chickens. Both viraemia and faecal virus shedding were delayed in chickens inoculated with the mixtures of avian HEV and 1E11, 10A2 or 5G10, suggesting that these three mAbs partially neutralize avian HEV.

Development and validation of a duplex real-time PCR assay for the simultaneous detection and quantification of porcine circovirus type 2 and an internal control on porcine semen samples

A duplex real-time quantitative PCR (qPCR) method for the simultaneous detection of porcine circovirus type 2 (PCV2) and an exogenous internal positive control (IPC) in porcine semen samples was developed. The IPC was included to monitor DNA extraction and PCR inhibition and consisted of a mutated PCV2 plasmid clone which differed from the target PCV2 in the probe binding region and thus was detected by the use of a second probe with different end-labeling. The sensitivity, specificity and repeatability of the assay were validated by testing semen samples from 12 boars inoculated experimentally with PCV2, 10 boars infected naturally with PCV2, and 3 PCV2 negative control boars. The duplex qPCR assay was found to be more sensitive, specific, rapid, and repeatable than nested PCR (nPCR) methods for the detection of PCV2 DNA in semen. Analysis of separated semen fractions by the duplex qPCR assay showed PCV2 DNA to be present mainly in the cell fraction as opposed to the seminal plasma fraction which is in contrast to previous reports. The duplex qPCR assay was found to be a valuable tool for accurate and quantitative detection of PCV2 DNA in boar semen.

Purification of the major envelop protein GP5 of porcine reproductive and respiratory syndrome virus (PRRSV) from native virions

Porcine reproductive and respiratory syndrome virus (PRRSV) is the cause of an economically important swine disease that has been devastating the global swine industry since the early 1990s. The current PRRSV vaccines are not very effective largely due to heterogeneic nature of the virus. The major envelope protein, GP5, exposes outside the virion, induces neutralizing antibodies, and thus is a primary target for developing a subunit vaccine. In this study, we report a process for purification of GP5 protein from native virions of PRRSV propagated in MARC-145 cells. PRRSV virions were first purified and concentrated through sucrose cushion ultracentrifugation. GP5 protein was subsequently solubilized with Triton X-100 detergent for further processing. Cation exchange chromatography (CEX) was utilized for partial fractionation of GP5, although the viral nucleocapsid protein (N) was a major impurity in CEX elution fractions. During a second chromatographic step, hydrophobic interaction chromatography (HIC) further purified GP5 protein by means of a two-stage elution scheme. Pure GP5 protein was eluted from the HIC resin in the second HIC elution stage by Triton X-100 displacement; however the protein is present as a homodimeric/tetrameric aggregate. This process may be useful in PRRSV subunit vaccine development.