Browsing by Author "Pelzer, Kevin D."
Now showing 1 - 18 of 18
Results Per Page
Sort Options
- Characterization of seasonal reproduction in Virginia Tech Selection Line, St. Croix, and Suffolk ewesJordan, Katherine Mead (Virginia Tech, 2008-08-04)This dissertation research contained three studies. The first two studies were conducted to investigate the ability of ewes to rebreed while lactating during seasonal anestrus. Breeds studied included the Virginia Tech Out-of-season (OOS) Line, which is a wool line genetically selected to lamb in the fall, and the St. Croix, a hair breed of tropical origin thought to be lowly seasonal. When January-lambing ewes were exposed to rams while lactating in April, significantly more OOS than St. Croix ewes were marked by rams in the first 21 d and total 39 d of ram exposure (58.3 vs. 8.7%, P = 0.0003 and 95.8 vs. 43.5%, P < 0.0001). Percentages of ewes diagnosed pregnant (53.2%) and percentages of ewes lambing (41.3%) were not different between breeds. When March-lambing OOS ewes were exposed to rams while lactating in May, 52.9% of ewes were marked though only 20% of ewes exposed to rams gave birth to viable lambs. Both OOS and St. Croix ewes appear to be well suited to accelerated production systems involving 7 to 8 mo lambing intervals. However, reduction of lambing intervals to 6 to 7 mo appeared to have detrimental effects on fetal survival in OOS ewes. In a third study, alterations in endocrine profiles associated with differing degrees of hypothalamic sensitivity to estradiol-negative feedback and changing daylength in OOS, St. Croix, and Suffolk ewes in the absence of rams were investigated for 1 yr. The results show for the first time that based on progesterone profiles from intact ewes, St. Croix ewes do not have shorter anestrous periods than ewes of wool breeds, as previously thought. Based on luteinizing hormone profiles from ovariectomized ewes treated with estradiol implants, the duration of luteinizing hormone inhibition was shorter in OOS than Suffolk ewes (68 vs. 170.2 d, P = 0.02), but was not different from that found in St. Croix ewes (124.8 d). Specific roles for thyroxine and prolactin in timing the breeding season could not be assigned. This study was the first known use of the ovariectomized, estradiol-implanted ewe model to compare degree of reproductive seasonality in different breeds.
- Club Lamb FungusCurrin, Nancy; Pelzer, Kevin D. (Virginia Cooperative Extension, 2009)Club lamb fungus affects the skin of sheep and is also known as woolrot, lumpy wool, sheep ringworm, and sheep dermatophytosis. It is highly contagious, and is contagious to humans.
- Comparison of Neospora seroprevalence in Virginia dairy herds with high and low abortion ratesMurphy, Julia M. (Virginia Tech, 1998-06-30)Neospora has become a commonly recognized infectious cause of abortion in dairy cattle. The organism is associated with mid to late term abortion outbreaks with rates exceeding 30% in some herds. Cows infected with this organism exhibit no other clinical signs. While this disease has been reported in other parts of the country, no assessment of Neospora seroprevalence has been undertaken in the Southeast. This study sampled commercial dairy herds to assess Neospora seroprevalence in dairy cows and investigate its significance as an abortifacient agent in Virginia. Twenty four herds participated in the study. Twelve herds had DHIA reported annual abortion rates of 6% or greater (high abortion rate herds) and twelve herds had abortion rates of 2% or less (low abortion rate herds). High abortion rate herds were each paired to a low abortion rate herd (control) herd within the same county. A single blood sample was collected from all cows confirmed to be 90 to 240 days pregnant, with a maximum of thirty samples per herd. A random sample of cows was selected in herds with more than 30 pregnant cows between 90 and 240 days gestation. Neospora antibody titers were determined using a serum ELISA test at the California Veterinary Diagnostic Laboratory. Both mean and median seroprevalence of high and low abortion rate herds were compared using the Mann-Whitney Rank Sum test and the Median test, respectively. No significant difference was found in either case (p=0.56, p=0.41). These findings suggest that Neospora does not contribute significantly to the average abortion rate in Virginia's dairy cattle.
- Correlation of Environmental Temperature, Precipitation, and Humidity with Salmonella Culture Results from Cattle in VirginiaKanistanon, Kwankate (Virginia Tech, 1997-03-11)Records of bovine samples submitted for salmonella cultures at four regional diagnostic laboratories in the state of Virginia were used to investigate the association of weather conditions and the diagnosis of salmonellosis in cattle. Spearman's correlation coefficients were calculated for the correlations between the monthly number of samples positive for salmonella culture and weather parameters: temperature, precipitation, and relative humidity. Significant correlation coefficients between the monthly average temperature and the monthly number of positive samples were found to be negative in one laboratory (rs= -0.38, p=0.03) and positive in one laboratory (rs=0.30, p=0.02). The latter correlation coefficient was found between the monthly average temperature and the monthly number of positive samples the following month. The same laboratories that had significant correlation of the monthly number of positive samples and the monthly average temperature also had significant correlation with the monthly average relative humidity (rs= -0.39, p=0.03 and rs=0.37, p=0.004). The monthly average relative humidity was more highly correlated to the number of positive samples reported in the same month for both laboratories that had significant correlation coefficients. None of the correlations between the monthly precipitation and the monthly number of positive samples were significant (p>0.05). The inconsistent directions of correlation coefficients need to be investigated further to find a reason for the discrepancy between regions of the state.
- Development of core-shell nanostructure encapsulating gentamicin as efficient drug delivery system against intracellular SalmonellaRanjan, Ashish (Virginia Tech, 2009-09-10)Intracellular pathogens like Salmonella have developed various mechanisms to evade host defenses, and they can establish infections. Treatment and eradication are difficult due to our inability in achieving the optimum concentrations of cell-impermeable aminoglycosides like gentamicin within these cells. In this dissertation, we hypothesize that developing a novel core-shell methodology for incorporating high amounts of gentamicin into the cores with either hydrophilic or amphiphilic shell will be more effective than the free gentamicin in clearing intracellular Salmonella infection. Hydrophilic core-shell nanostructures (N1) were made with block co-polymers of poly (ethylene oxide-b-sodium acrylate) blended with sodium polyacrylate (PAA-+Na) and complexed with the polycationic antibiotic gentamicin. N1 showed 20-25 fold higher gentamicin loading than the currently existing materials and reduced numbers of viable Salmonella in the liver and spleen compared to free gentamicin. To further improve the rate and route of uptake, the shell of the nanostructures were made amphiphilic by incorporating pluronics F68 (PPO)₆₈ in the block copolymer. We showed that core-shell nanostructures encapsulating gentamicin having (PPO)₆₈ in the shell (N2) enhances the rate and modulates the route of uptake into macrophages, thus promoting significant reduction in the intracellular Salmonella in-vitro and in-vivo. The main drawback of N2 was its poor stability at physiological pH of 7.4, 0.1 M NaCl. Therefore, core-shell nanostructures encapsulating gentamicin containing pluronic P85 (PPO)₈₅ in the shell (N3) with improved colloidal and ionic stability were designed. N3 achieved significant intracellular reduction of vacuolar Salmonella (0.53 log₁₀) and cytoplasm resident Listeria (3.11 log₁₀) compared to free gentamicin in-vitro. However, greater reduction of Listeria suggested that sub-cellular localization of bacterium influences targeting by N3. Even though oral administration of N3 was not effective compared to free gentamicin, parenteral (I.P.) administration significantly reduced the intracellular Salmonella from liver and spleen compared to free gentamicin and appeared to have no abnormal in-vivo toxicity. In summary, core-shell nanostructures encapsulating gentamicin (N) with improved encapsulation efficiency and different shell chemistry (N1, N2 and N3) were developed with enhanced efficacy against intracellular Salmonella. The novel gentamicin delivery approach developed in this study may be applicable for therapy of many intracellular infections.
- Effects of antemortem ingestion of ethanol on insect successional patterns and development of Phormia regina (Diptera : Calliphoridae)Tabor, Kimberly L.; Fell, Richard D.; Brewster, Carlyle C.; Pelzer, Kevin D.; Behonick, George S. (Oxford University Press, 2005-05-01)The effects of antemortem ingestion of ethanol by domestic pigs, Sus scrofa L., on postmortem insect successional patterns and the development of Phormia regina (Meigen) were studied during summer 2003 in Blacksburg, VA. Insect samples were collected from the carcasses of ethanol-treated and untreated pigs for 10 d postmortem during two successional studies. In total, 32 insect taxa were collected during the two studies, with 29 and 27 taxa observed on the carcasses of ethanol-treated and untreated pigs, respectively. The earliest arrivers to both carcass types were dipterans. This group was represented by six families, with P. regina and Phaenicia coeruleiviridis (Macquart) being the most common calliphorids. Beetles in six families were collected on the carcasses of ethanol-treated pigs, but only three of the families were collected on carcasses of the untreated pigs. Permutation analyses to test the null hypothesis of no similarity between successional patterns of insect taxa from carcasses of ethanol-treated and untreated pigs showed that the successional patterns were similar between carcass types in the first (P = 0.003) and the second (P = 0.01) studies. The results of the development study of P. regina maggots in the field show that there was a significant difference between the distributions of length for maggots reared on loin tissue from ethanol-treated and untreated pigs. Maggots that fed on tissue from ethanol-treated pigs took approximate to 11.9 11 longer to reach the pupal stage than maggots that fed on tissue from untreated pigs. The longer developmental time for maggots on tissue from ethanol-treated pigs was due mainly to the longer postfeeding period of the third instar.
- Entomotoxicological and Thermal Factors Affecting the Development of Forensically Important FliesMonthei, Derek Reed (Virginia Tech, 2009-02-06)Studies were conducted on the effects of alcohol and opioids on the development of forensically important flies. In addition different methods of degree-day calculations and development thresholds were used to determine the effects on PMI estimates. The first study determined the effects of ethanol on the development of Phormia regina in vitro. Ground pork loin was treated with a 1, 5, or 10% ethanol solution to give an equivalent Blood Alcohol Concentration (BAC) of 0.01, 0.04, and 0.8 % w/v. A significant difference in the time for second instars to complete the stage was seen between the 1% treated and control. Significant differences were also found among pupal and adult weights between all treatments and the control. A significant difference was shown between growth curves of the 5% treated and control for third instar larvae using the Kolmogorov-Smirnov test. The ethanol content of Phormia regina in migrating third instar larvae that fed on treated meat was examined using headspace-gas chromatography (HSGC). All larvae had a content of 0.01% w/v, including the control. The effects of ante-mortem injection of oxycodone in pigs were examined with respect to insect succession patterns and the development rates of Phormia regina. Pigs were given a subcutaneous injection of oxycodone hydrochloride (3 mg/kg by weight) and antemortem blood samples were collected prior to and following drug injection. Shortly after death the carcasses were placed at an open field site and allowed to decompose in a field cage. Insect samples were collected from carcasses for seven days post-mortem and the collected data were used to develop occurrence matrices. The Simple Matching Coefficient showed that successional patterns were similar between treated and untreated animals. Loin and liver from the carcasses were used as rearing media for in vitro development studies of Phormia regina. Kolmogorov-Smirnov test showed that third instar P. regina maggots from treated loin tissue were significantly longer in length than maggots feeding on untreated loin tissue. A significant difference in time was found among larvae on loin for the time from eclosion to completion of the second instar. Significant differences were seen in the weight of adults reared on liver and loin. A chi-square for homogeneity showed that adults were biased towards males (2:1) from untreated loin tissue. A final study compared weather data sources, Accumulated Degree-Day (ADD) methods, and postmortem interval (PMI) estimations based on threshold and developmental data source. Four pigs were used for statistical comparisons. Pigs were taken to a test site and allowed to decompose in an experimental cage. Probes recorded ambient temperatures and body temperatures. Maggot sampling was completed every day for each pig. A three way factorial linear fit model was used to test for statistical differences. Significant differences were seen in the calculated ADD based on probe location and the development threshold used. The ADD calculated from local weather station locations: Kentland Farm, Moore Farm, and Blacksburg Airport were also compared. A significant difference in ADD was found in the main effects among locations (Airport 44.1 ADD, Kentland 37.5 ADD, Moore 48.6 ADD), as well as among the thresholds used (10,12.2, and 14°C). Different PMI estimations also resulted when using development data from different development studies on Phormia regina.
- Evaluation of systematic breeding programs in lactating dairy cowsJobst, Shelly Marie (Virginia Tech, 1998-11-04)Observing cows in estrus and inseminating them at the optimal time are necessary steps for effective reproductive management of a dairy herd. However, increasing herd sizes can lead to reproductive inefficiency resulting in decreased profits on dairy herds. Synchronization of estrus, through pharmacological control, has been used to improve reproductive efficiency. Systematic breeding programs provide an organized approach for administering artificial insemination (AI) at first service. Moreover, reproductive management is based on a methodical approach for the entire herd rather than for the individual cow. Seven-hundred and thirty four Holstein cows from 16 commercial dairy herds were used to conduct this study evaluating three systematic breeding protocols; 14-d PGF2a, timed AI (TAI), and GnRH-PGF2α, in comparison with an untreated control group. Eight herds relied on visual observation as their primary method for detection of estrus, and 8 herds utilized the HeatWatch® (DDx, Inc., Denver, CO) electronic estrus detection system. The average days to first postpartum AI were longer for untreated control cows when compared to the other breeding protocols. First AI conception rates did not differ among control, 14-d PGF2a, or GnRH-PGF2a protocols, but were higher than the TAI protocol. However, first AI pregnancy rates were higher for untreated controls versus hormonally treated cows. Estrus characteristics associated with each protocol were also evaluated and no difference was detected across treatments. An economic analysis determining cost per pregnancy for each protocol when considering drug costs, and pregnancy rates, resulted in the highest cost per pregnancy for TAI followed by GnRH-PGF2a and 14-d PGF2a. These programs should be considered as tools for convenience and efficiency of estrus detection; however, reduced labor costs from less time spent on estrus detection may be offset by the cost of the drug protocols. Cost effectiveness must be calculated on an individual herd basis when deciding whether a systematic breeding program is the appropriate choice.
- A farm-based prospective study for equine colic risk factors and risk associated eventsTinker, Mary Kay (Virginia Tech, 1995)Improved definition of risk factors for equine colic is necessary to develop effective interventions to reduce colic incidence. A one-year prospective study was conducted to estimate colic incidence and to identify risk factors. Farms with greater than 20 horses were randomly selected from two adjacent counties of Virginia and Maryland. Management information was recorded by questionnaire for 31 farms with 1427 horses. Owners kept calendars to record occurrence of specified events. Colic was reported by the owner when a horse exhibited signs of abdominal pain. The incidence of colic was 10.6 colic cases per 100 horse-years, based on 104 cases per 983.5 horse-years. Twenty-five deaths occurred from all causes, the proportional mortality rate of colic was 7/25 (28%). Risk factors were analyzed by logistic regression at the farm-level and the horse-level with farm as a random effects variable. No farm-level variables were significant. Significant horse variables were: age 2-10 years, odds ratio (OR)=2.8 (95% confidence interval, 1.2-6.5); previous colic, OR=3.6(1.9-6.8); changes in concentrate feeding during the year, OR=3.6(1.6-5.4); more than one change in hay feeding during the year, OR=2.1(1.2-3.8); feeding high levels of concentrate (>2.5 kg/day dry matter, OR=4.8(1.4-16), >5 kg/day dry matter, OR=6.3(1.8-22)); and vaccination with monocytic ehrlichiosis vaccine during the study, OR=2.0(1.8-22). Feeding whole grain with or without other concentrates had less risk than diets without whole grain included. Variables related to concentrate feeding frequency or concentrate type could be substituted for the concentrate level variable. A nested analysis examined risk for the time period following an event. The odds ratio was determined for the proportion of cases with an event within 14 days prior to the colic-date, relative to the proportion of horses without colic with an event within 14 days of a date chosen at random from the observation time. Weather events were analyzed for the three days before the colic or assigned date. Foaling was analyzed for three time periods: before, 0-60 and 60-150 days post-foaling. Significant events were recent vaccination, OR=3.31(1.9-6.0); recent transport, OR=3.3(1.2-5.5); 60-150 days post-foaling, OR=5.9(1.8-13); and recent fever, OR=20(2.5-169). Snow on the day of the colic, OR=2.8(1.0-7) and humidity <50% the day before the colic OR=1.6(1.0-2.9) were marginally significant.
- Finding Typhoid Mary: Identifying Latent Carriers of Salmonella enterica serovar TyphimuriumSchroeder, Betsy (Virginia Tech, 2020-09-16)Salmonella enterica serovar Typhimurium (S. Typhimurium) is an important human pathogen. The Centers for Disease Control and Prevention (CDC) estimates that 1,027,561 people become ill with nontyphoidal Salmonellosis annually, and S. Typhimurium is one of the most common disease causing serovars. Quantification of the true number of cases of salmonellosis is hampered by the presence of a carrier state. These carriers are animals and humans that carry the pathogens for a variable period of time without showing any clinical signs. One of the biggest barriers to controlling and preventing salmonellosis in a population is identification of these carriers. Identifying these latent carriers of chronic infections is vital to preventing such disease transmission and creating avenues for novel control and treatments. In my dissertation research, we developed a cell culture model to study latent Salmonella infections. By activating human monocytes with retinoic acid and vitamin D3, we were able to isolate Salmonella from such cells 45 days after inoculation. We subsequently used this model to identify genes that were upregulated in this chronic infection model. We found that aceA, a gene that codes for isocitrate lyase, is significantly upregulated on days 10 and 30 post infection. Isocitrate lyase is part of the glyloxylate cycle. Some bacterial species have developed a mechanism to utilize acetone as a carbon source to synthesize tricarboxylic acid (TCA) cycle intermediates. This anaplerotic reaction allows organisms to conserve carbon and use alternative carbon sources. This cycle is one way in which bacteria can adapt and survive in an intracellular environment. This intracellular survival is key to latent infections persisting within a host. It is biologically plausible that, in order to survive in a latent state, S. Typhimurium would up-regulate genes that would facilitate intracellular survival. After establishing the cell culture model, we tested the hypothesis that aceA is upregulated in latent infections of S. Typhimurium in a mouse model. We orally challenged mice that were resistant to Salmonella infection, collected their feces, and collected tissue specimens at several time points up to 135 days post-challenge. These samples were cultured and tested using quantitative polymerase chain reaction (qPCR). The qPCR results showed that tissue samples from inoculated mice had increased aceA expression 95 days after challenge. Finally, we examined whether aceA expression could be detected in cattle lymph node samples. Supra-mammary lymph nodes from 40 dairy cattle and mesenteric lymph nodes from 100 culled cattle were sampled and submitted for culture and qPCR. None of the supra-mammary lymph nodes were positive for Salmonella via culture or aceA qPCR; however, 11 mesenteric lymph nodes showed increased aceA expression in qPCR compared to 5 culture positive lymph nodes. Further research is necessary, but these results demonstrate some of the advantages of using genetic primers to identify latent Salmonella infections in clinically normal cattle. In addition, the assay may be able to differentiate between latent and active salmonellosis, and could be used to provide targeted drug delivery.
- Goat-Herd Health CalendarWhittier, W. Dee; Pelzer, Kevin D.; Currin, Nancy (Virginia Cooperative Extension, 2009)Provides a calendar of herd health procedures for adult goats and kids
- A neonatal gnotobiotic pig model of human enterovirus 71 infection and associated immune responsesYang, Xingdong; Li, Guohua; Wen, Ke; Bui, Tammy; Liu, Fangning; Kocher, Jacob; Jortner, Bernard S.; Vonck, Marlice; Pelzer, Kevin D.; Deng, Jie; Zhu, Runan; Li, Yuyun; Qian, Yuan; Yuan, Lijuan (Nature Publishing Group, 2014-05-21)Vaccine development and pathogenesis studies for human enterovirus 71 are limited by a lack of suitable animal models. Here, we report the development of a novel neonatal gnotobiotic pig model using the non-pig-adapted neurovirulent human enterovirus 71 strain BJ110, which has a C4 genotype. Porcine small intestinal epithelial cells, peripheral blood mononuclear cells and neural cells were infected in vitro. Oral and combined oral–nasal infection of 5-day-old neonatal gnotobiotic pigs with 53108 fluorescence forming units (FFU) resulted in shedding up to 18 days post-infection, with viral titers in rectal swab samples peaking at 2.223108 viral RNA copies/mL. Viral capsid proteins were detected in enterocytes within the small intestines on post-infection days (PIDs) 7 and 14. Additionally, viral RNA was detected in intestinal and extra-intestinal tissues, including the central nervous system, the lung and cardiac muscle. The infected neonatal gnotobiotic pigs developed fever, forelimb weakness, rapid breathing and some hand, foot and mouth disease symptoms. Flow cytometry analysis revealed increased frequencies of both CD41 and CD81 IFN-c-producing T cells in the brain and the blood on PID 14, but reduced frequencies were observed in the lung. Furthermore, high titers of serum virus-neutralizing antibodies were generated in both orally and combined oral–nasally infected pigs on PIDs 7, 14, 21 and 28. Together, these results demonstrate that neonatal gnotobiotic pigs represent a novel animal model for evaluating vaccines for human enterovirus 71 and for understanding the pathogenesis of this virus and the associated immune responses.
- Novel approaches towards vaccine developments against porcine circovirus type 2 and porcine reproductive and respiratory syndrome virusPineyro Pineiro, Pablo Enrique (Virginia Tech, 2015-11-06)Porcine circovirus type 2 (PCV2) is the causative agent of porcine circovirus-associated disease (PCVAD). Porcine reproductive and respiratory syndrome (PRRS) is caused by PRRS virus (PRRSV). Both PCV2 and PRRSV have caused devastating diseases in the swine industry worldwide, resulting in immense economic losses. One of the most common co-infections in the swine industry is PCV2 and PRRSV. The aim of this dissertation research is to explore different experimental approaches to develop novel vaccines against the two major pathogens affecting swine production and study the basic mechanisms that may be involved in viral pathogenesis. Two types of porcine circovirus (PCV), PCV1 and PCV2, have been identified thus far. PCV1, first identified as a contaminant of the PK-15 cell line, is non-pathogenic and has a low prevalence in swine herds. PCV2 is highly prevalent in most swine-producing countries and is associated with clinical PCVAD. The non-pathogenic PCV1 shares similar genomic organization with PCV2. Previously, it has been demonstrated that a genetically modified infectious chimeric PCV1-2a virus can tolerate up to a 27 aa insertion in the C-terminus of the ORF2 without affecting infectivity and produce a dual immune response against PCV2cap and the inserted epitope tag. Therefore, we evaluated the use of the non-pathogenic PCV1 wild-type (wt) virus and chimeric PCV1-2a vaccine virus (vs) to express four known B-cell epitopes of PRRSV. Peptide epitopes of PRRSV-VR2385, including GP2II (aa 40–51, ASPSHVGWWSFA), GP3I (aa 61–72, QAAAEAYEPGRS), GP5I (aa 35–46, SSSNLQLIYNLT), and GP5IV (aa 187–200, TPVTRVSAEQWGRP) were inserted in frame into the C-terminus of the ORF2 of PCV1wt as well as the PCV1-2avs. Four PCV1-PRRSVEPI chimeric viruses and four PCV1-2a-PRRSVEPI chimeric viruses were successfully rescued and shown to be infectious in vitro and co-expressed PCV1cap or PCV2cap with each specific PRRSV epitope. Two independent animal studies were conducted to evaluate whether the non-pathogenic PCV1 can serve as a vaccine delivery vector and whether the PCV1-2a vaccine virus can be used to develop a bivalent vaccine against both PCV2 and PRRSV. We demonstrated that three PCV1-PRRSVEPI chimeric viruses and two PCV1-2a-PRRSVEPI chimeric viruses were infectious in pigs. Importantly, we demonstrated that the PCV1-PRRSVEPI and PCV1-2a-PRRSVEPI chimeric viruses not only induced specific PCV1 or PCV2 IgG antibody but also specific anti-PRRSV epitope antibody responses as well. Regardless of the PCV backbone used, we showed that the PCV-PRRSV chimeric viruses elicited neutralizing antibodies against PRRSV-VR2385. These results provided a proof of concept for the potential use of the non-pathogenic PCV1 as a vaccine delivery system for PRRSV or other swine pathogens and the use of PCV1-2a vaccine virus to generate a bivalent vaccine against both PCV2 and PRRSV. PRRSV causes a persistent infection and immunosuppression. Immunomodulation of the host immune system is caused by modulation of numerous interleukins, such as type I interferons, tumor necrosis factor alpha (TNF-α), interleukin-1 (IL-1), interleukin-6 (IL-6), and interleukin-12 (IL-12) in infected pigs. Antigen-presenting cells (APCs) are the first line of defense, and their infection plays an important role in innate-mediated immune regulation during early immune responses. Among the APCs, pulmonary alveolar macrophages (PAMs), pulmonary interstitial macrophages (PIMs), and dendritic cells (DCs) are the main targets for PRRSV replication. The role of PRRSV-DCs interaction is not fully understood, and current research focuses on the production and regulation of interferons through DC-SIGN receptors. In this study, we evaluated the immunomodulation of MoDCs by PRRSV through interactions with the pDC-SIGN receptor, by blocking pDC-SIGN with recombinant hICAM-3-Fc or anti-pDC-SIGN mAb. Our results indicate that recombinant hICAM-3-Fc enhances mRNA expression of proinflammatory cytokines and that anti-pDC-SIGN mAb inhibits mRNA expression of TNF-α and IL-1α and enhances the expression of IL-12 induced by PRRSV in MoDCs. The results will help understand the molecular mechanisms of PRRSV pathogenesis.
- Plasma amino acid and metabolite changes in pigs during endotoxemiaPrice, Kathryn Leigh (Virginia Tech, 2011-11-15)The nutritional status, especially circulating amino acid (AA) levels, can drastically change during a non-infectious (i.e., LPS) or infectious (e.g., Salmonella) challenge. Thus, study 1 examined the effect of LPS treatment (N = 9, 26.9 ± 1.07 kg BW) on plasma AA and metabolite levels in pigs. Data were used to generate prediction equations establishing mathematical relationships between plasma AA levels and numerous blood metabolites (e.g., total lipid, LDL, HDL, blood urea nitrogen, etc). These equations have the potential to improve the nutritional treatment and recovery of acute and chronically ill patients. Study 2 (19.1 ± 0.37 kg) was a continuation of study 1 except the sampling time was increased from 12 to 24 h. One-half of the pigs in study 2 were treated with LPS (N=15) and the other one-half were saline treated control animals (N = 16). This design allows for monitoring changes in plasma AA and their catabolism in response to endotoxemia. Area under the curve (AUC) was calculated for a selected AA to report AA balances. During the induction phase of an acute challenge (t = -2 to 12 h), analyzed AA were in a negative balance indicating heavy AA catabolism. However, during the recovery phase (t = 12 to 24 h) half of the AA were in a positive balance while the other half were still negative. The ability of equations to accurately predict AA concentrations was tested. Results indicate poor performance possibly due to heavy term biases. Thus, it was concluded that equations need to be revisited and non-linear terms need to be evaluated. Nonetheless, routine clinical blood metabolites can be used to estimate plasma AA levels during immune activation. We successfully established a porcine Salmonella enterica serovar Typhimurium model. Pigs infected with Salmonella had a febrile response for 4 d and exhibited marked changes in their fecal bacterial populations Finally, we investigated plasma changes in N-τ-methyl histidine (NτMH) in healthy and LPS-treated pigs. NτMH— is a post-translationally modified AA that has historically been used as an indirect marker of muscle protein breakdown in rodents and humans. However, the major form (i.e., free or acetylated) of NτMH in pig plasma was unknown. Results indicate that only 15% of plasma NτMH is in the free form and the remainder is acetylated. Furthermore, LPS treated pigs had increased acetylated and total NτMH fractions while free NτMH did not change. Therefore, to accurately monitor plasma changes in NτMH as an indicator of muscle proteolysis, plasma samples must be subjected to acid hydrolysis.
- Porcine circovirus associated disease: Modulation of the host immune response to PCV2 and PRRSV by regulatory T cellsCecere, Thomas E. (Virginia Tech, 2012-05-21)Porcine circovirus associated disease (PCVAD) is currently one of the most economically important diseases facing the global swine industry. Porcine circovirus type 2 (PCV2) is the primary and essential causative agent of PCVAD, but development of clinical disease typically requires co-infection with other swine pathogens such as porcine reproductive and respiratory syndrome virus (PRRSV). The specific mechanisms of co-infection that lead to clinical disease are not fully understood, but immune modulation by the co-infecting viruses is thought to play a critical role. The ability of dendritic cells (DC) infected with PRRSV, PCV2 or both to induce regulatory T cells (Tregs) was evaluated in vitro. DCs infected with PCV2 significantly increased CD4+CD25+FoxP3+ Tregs (p<0.05) and DCs co-infected with PRRSV and PCV2 induced significantly higher numbers of Tregs than with PCV2 alone (p<0.05). This Treg induction was found to be dependent on TGF-β and not IL-10. Further investigation of the in vivo swine immune response to acute co-infection with PCV2 and PRRSV failed to detect activation of Tregs in peripheral blood mononuclear cells (PBMCs) or bronchoalveolar lavage samples. The Treg response to in vitro and in vivo PRRSV challenge in pigs persistently infected with PCV2 or vaccinated against PCV2 was evaluated. There was no significant difference in Tregs in PBMCs among chronically PCV2-infected, vaccinated PCV2 challenged or negative control pigs. However, following in vitro infection of monocyte-derived dendritic cells with PCV2, PRRSV, or both viruses, co-cultured lymphocytes from chronically infected and PCV2 vaccinated pigs had significantly (p<0.05) decreased Treg expression in the virus infected groups compared to the negative controls. In separate experiments, pigs vaccinated against PCV2 and subsequently challenged with an attenuated PRRSV strain and its pathogenic parental strain developed increased CD4+CD25+FoxP3+ Tregs (p<0.05) in PBMC samples compared to uninfected controls, and this correlated with increased suppressor activity and IL-10 expression. The findings from these studies indicate that the interaction of PCV2 and PRRSV in swine modulates the host immune response mediated in part through the activity of Tregs. However, the extent to which Tregs orchestrate a dysregulated immune response in the pathogenesis of PCVAD in vivo remains to be determined.
- Tocopherol induced angiogenesis in placental vascular network in late pregnant ewesKasimanickam, Ramanathan K.; Kasimanickam, Vanmathy R.; Rodriguez, Jacobo S.; Pelzer, Kevin D.; Sponenberg, D. Phillip; Thatcher, Craig D. (2010-07-12)Background Tocopherols have biphasic, proangiogenic and antiangiogenic therapeutic effects. The objective of this clinical trial was to clarify tocopherol's placental angiogenic potential in late pregnant ewes following oral supplementation. Methods Eighteen pregnant ewes during late gestation were selected for this study. Ewes were given oral supplementation of 500 mg of alpha-tocopherol (aT; N = 6) or 1000 mg of gamma-tocopherol (gT; N = 7) or placebo (CON; N = 5) once daily from 107 to 137 days post breeding. Serum was obtained at weekly intervals and tissue samples were obtained at the end of supplementation to: 1) evaluate tocopherol concentrations in serum, uterus and placentome; 2) evaluate relative mRNA expressions of Vascular Endothelial Growth Factor (VEGF), Placental Growth Factor (PlGF), endothelial Nitric Oxide Synthase (eNOS) and Hypoxia Inducible Factors (HIF) in uterus, caruncle and cotyledon; 3) analyze the morphometry of the placental vascular network. Results Supplementation of aT or gT resulted in increased concentrations in serum, placentome and uterus compared to control (P < 0.05). In aT group, mRNA expressions of PlGF, eNOS and HIF-1α in cotyledon were greater than the CON group. In gT group, mRNA expressions of VEGF, eNOS, HIF-1 alpha and HIF-2 alpha in caruncle and uterus, and HIF-1α in cotyledon, were greater than the CON group. Morphometry analysis revealed increased angiogenesis in the supplemented groups. Conclusion Daily oral supplementation of aT or gT increased angiogenesis in the placental vascular network in pregnant ewes during late gestation. Increase in placental angiogenesis may provide nutrients required for the development and growth of fetus during late pregnancy.
- Veterinary Therapeutic and Biologic Agents in Virginia Sheep ProductionRorrer, Rebecca Kathleen (Virginia Tech, 2002-07-16)Biological and therapeutic agents are used in food animal production to maintain animal health and well being, prevent and treat disease, and to maintain or enhance production. Concerns about the use of pharmaceutical agents in food animal production have been raised, especially in relation to food quality and safety. This study addressed the scarcity of information concerning the quantity of pharmaceuticals being used and the reasons for their use in sheep production. Additional goals included determining the sources of information used by shepherds in making treatment decisions and evaluating the economic impact that pharmaceutical usage has on sheep production. Thirty-nine Virginia sheep producers participated in this study of four months duration from March through September. After completing an initial questionnaire to determine flock and management characteristics, participants were asked to record all treatments with biological and therapeutic agents that occurred within their sheep flocks. A total of 14,310 treatments were recorded for a median of 1.5 treatments per sheep per month. Parasite control and vaccination were the most frequent reasons for treatment (64.9% and 15.2%, respectively) with vitamin/mineral supplementation being the next most common (8.8%). Price information was collected for 13,912 treatment events. An estimated total of $7,523.78 was spent on pharmaceutical treatment over the course of the study. This amounts to a cost of $0.63 per sheep per month of observation. Results of this study will enhance the ability of producers to evaluate treatment decisions, allow comparisons to be made between operations and provide a base of information for future research.
- Zoonotic Diseases of CattlePelzer, Kevin D.; Currin, Nancy (Virginia Cooperative Extension, 2005-09-01)There are numerous zoonotic diseases that can be transferred from cattle to humans, that cause mild to severe symptoms. While some of the diseases are rare, it is necessary to take precautions for these diseases seriously.