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Biomedical subjects

M Pensaert

Publications and source records attributed to M Pensaert.

At least 19 recordsLinked to original sources
PubMed2004

Impact of genetic diversity of European-type porcine reproductive and respiratory syndrome virus strains on vaccine efficacy.

The aim of this study was to find out how efficiently pigs that are vaccinated with an attenuated porcine reproductive and respiratory syndrome virus (PRRSV) vaccine based on a virus from the Lelystad cluster are protected against a European wild-type strain from the same or another genetic cluster. Two experiments were performed. In each experiment, 5-week-old PRRSV-seronegative pigs were vaccinated intramuscularly with 10(4.5) TCID50 of a commercial vaccine based on a European virus strain from the Lelystad cluster. Non-vaccinated pigs were included as controls. At 5, 9, 15, 20, 28, 35 and 42 days post vaccination (PV), broncho-alveolar lavage (BAL) fluids and blood were collected to determine vaccine virus quantities. Forty-nine days PV, pigs were challenged intranasally with 10(6.0) TCID50 of a European wild-type strain, belonging either to the Lelystad cluster (98% nucleotide identity in ORF5 with vaccine strain) (experiment A) or to an Italian cluster (84% nucleotide identity in ORF5 with vaccine strain) (experiment B). At 5, 9, 15, 20 and 27 days post challenge (PC), BAL fluids and blood were collected to determine virus quantities. Vaccine virus was first detected in BAL fluids and blood at 5 days PV and reached highest quantities between 9 and 15 days PV. One pig was positive in its BAL fluid until 42 days PV. After challenge, virus was isolated from BAL fluids and blood of all non-vaccinated control pigs. All vaccinated pigs challenged with the Lelystad strain remained negative for virus, while virus was present in BAL fluids and blood of all vaccinated pigs after challenge with the Italian strain. Mean virus titres of the vaccinated pigs challenged with the Italian strain were significantly lower than those of the non-vaccinated control pigs (P <0.05) at 9, 15 and 20 days PC. Thus, the genetic diversity within European-type PRRSV may affect the efficacy of the current European-type vaccines.

Animals↗
PubMed2004

Aujeszky's disease vaccination and differentiation of vaccinated from infected pigs.

In this paper, the use of a glycoprotein E (gE)-deleted vaccine to eradicate Aujeszky's disease virus (ADV) or pseudorabies virus in swine is described. In regions where there is a dense population of swine, ADV is highly prevalent and intensive vaccination with such a marker vaccine has resulted, in several countries, in a decrease of the field virus prevalence to a sufficiently low level so that culling becomes economically feasible. The evolution in the reduction of circulating field virus can be followed at herd and/or population level by serological monitoring for antibodies against gE, using commercially available enzyme-linked immunosorbent assays. To be successful, other measures besides the vaccination in itself are important, such as the proper use and administration of the vaccine, repeated boosters, prevention of introduction of gE-positive animals and restriction in the movement of animals from gE-positive herds. When pockets of infection remain, intensifying the vaccination may be needed. Culling of remaining gE-positive animals, particularly breeders, is usually necessary. Some European Union (EU) member states have become ADV-free using this approach. Others are still working at it. The success is often dependent on whether or not a good discipline exists. The disease situation in the different EU member states is described. In ADV-free regions with dense swine populations at risk, it is advisable not to stop the vaccination too soon, particularly when the infection status in neighbouring countries or trade partners is not equally good.

Animals↗
PubMed2003

Respiratory tract protection upon challenge of pigs vaccinated with attenuated porcine reproductive and respiratory syndrome virus vaccines.

In this study, the efficacy of two attenuated porcine reproductive and respiratory syndrome virus (PRRSV) vaccines was assessed. The virological protection in the lungs of vaccinated pigs upon challenge was studied. Also, challenged pigs were exposed to lipopolysaccharide (LPS) to evaluate clinical protection. Six-week-old pigs were immunized intramuscularly with commercial vaccines based on either an attenuated American or an attenuated European virus strain. Non-immunized pigs and pigs intramuscularly inoculated with the virulent Lelystad strain were included as controls. Six weeks after immunization, pigs were challenged either intratracheally or intranasally with the Lelystad strain, and 3 and 6 days later intratracheally exposed to Escherichia coli LPS. After LPS administration, pigs were monitored for clinical signs. At 4 and 7 days after challenge, pigs were euthanized to determine virus quantities in broncho-alveolar lavage (BAL) fluids and in lungs. Challenge virus was recovered from three out of eight pigs that had been primo-inoculated with the Lelystad strain with titers ranging between 0.3 and 3.1 log(10). Fifteen out of sixteen pigs vaccinated with the attenuated American strain were positive for challenge virus and their mean virus titers were similar to those of non-immunized challenge controls. Eleven out of 16 pigs vaccinated with the attenuated European strain were positive for challenge virus and their mean virus titers were 2.0-2.5 log(10) lower than those of non-immunized challenge controls. Thus, the virological protection in the lungs of vaccinated pigs upon challenge was incomplete, but was more pronounced in the homologous situation. Clinical signs upon LPS exposure in both vaccinated groups were not reproducible in two experiments.

Animals↗
PubMed2003

Investigations of the efficacy of European H1N1- and H3N2-based swine influenza vaccines against the novel H1N2 subtype.

The efficacy of a commercial swine influenza vaccine based on A/New Jersey/8/76 (H1N1) and A/Port Chalmers/1/73 (H3N2) strains was tested against challenge with an H1N2 swine influenza virus. Influenza virus-seronegative pigs were vaccinated twice with the vaccine when they were four and eight weeks old, or with the same vaccine supplemented with an H1N2 component. Control pigs were left unvaccinated. Three weeks after the second vaccination, all the pigs were challenged intratracheally with the swine influenza strain Sw/Gent/7625/99 (H1N2). The commercial vaccine induced cross-reactive antibodies to H1N2, as detected by the virus neutralisation (VN) assay, but VN antibody titres were 18 times lower than in the pigs vaccinated with the H1N2-supplemented vaccine. The challenge produced severe respiratory signs in nine of 10 unvaccinated control pigs, which developed high H1N2 virus titres in the lungs 24 and 72 hours after the challenge. Vaccination with the commercial vaccine resulted in milder respiratory signs, but H1N2 virus replication was not prevented. Mean virus titres in the pigs vaccinated with the commercial vaccine were 1-5 log10 lower than in the controls at 24 hours but no different at 72 hours. In contrast, the H1N2-supplemented vaccine prevented respiratory disease in most pigs. There was a 4-5 log10 reduction in the mean virus titre at 24 hours in the pigs vaccinated with this vaccine, and no detectable virus replication at 72 hours. These data indicate that the commercial swine influenza vaccine did not confer adequate protection against the H1N2 subtype.

Animals↗
PubMed2002

Porcine reproductive-respiratory syndrome virus infection predisposes pigs for respiratory signs upon exposure to bacterial lipopolysaccharide.

This study examined whether an infection with porcine reproductive and respiratory syndrome virus (PRRSV) potentiates respiratory signs upon exposure to bacterial lipopolysaccharides (LPS). Five-week-old conventional pigs were inoculated intratracheally with the Lelystad strain of PRRSV and received 5 days later one or two intratracheal LPS administrations. The necessary controls were included. After LPS administration, pigs were intensively monitored for clinical signs. Additionally, some pigs were euthanatized after a second LPS administration for broncho-alveolar cell analysis and virological examinations of the lungs. Broncho-alveolar lavage (BAL) cells were counted and differentiated. Lung suspensions and BAL fluids were titrated for PRRSV. Exposure of pigs to PRRSV only resulted in a fever for time periods ranging from 1 to 5 days and slight respiratory signs. Exposure of pigs to LPS only resulted in general signs, characterized by fever and depression, but respiratory signs were slight or absent. PRRSV-LPS exposed pigs, on the other hand, developed severe respiratory signs upon LPS exposure, characterized by tachypnoea, abdominal breathing and dyspnoea. Besides respiratory signs, these pigs also showed enhanced general signs, such as fever and depression. Lung neutrophil infiltration was similar in non-infected and PRRSV-infected pigs upon LPS exposure. PRRSV quantities were similar in lungs and BAL fluids of pigs infected with PRRSV only and PRRSV-LPS exposed pigs. These data show a clear synergism between PRRSV and LPS in the induction of respiratory signs in conventional pigs. The synergism was observed in 87% of the pigs. So, it can be considered as reproducible and may be used to test the efficacy of preventive and therapeutic measures.

Animals↗
PubMed2002

Efficacy of avian pneumovirus vaccines against an avian pneumovirus/Escherichia coli O2:K1 dual infection in turkeys.

The clinical, pathological and microbiological outcome of a challenge with avian pneumovirus (APV) and Escherichia coli O2:K1 was evaluated in turkeys vaccinated with an attenuated APV vaccine and with or without maternally derived antibodies. Two groups of two-week-old poults, one with and one without maternally derived antibodies against APV, were vaccinated oculonasally with attenuated APV subtype A or B. A third group remained unvaccinated. Eleven weeks later, the turkeys were inoculated intranasally with either virulent APV subtype A, or E. coli O2:K1, or with both agents three days apart. After the dual infection, birds vaccinated with attenuated subtype A or B, and with or without maternally derived antibodies, had lower mean clinical scores than the unvaccinated birds. In the vaccinated birds, virus replication was significantly reduced and no bacteria were isolated, except from the birds vaccinated with attenuated subtype B. In the unvaccinated turkeys, large numbers of E. coli O2:K1 were isolated from the turbinates of the dually infected birds between one-and-a-half and seven days after they were inoculated.

Animals↗
PubMed2002

Correlations between lung proinflammatory cytokine levels, virus replication, and disease after swine influenza virus challenge of vaccination-immune pigs.

During experimental infection of pigs with swine influenza virus (SIV), there is a strong temporal correlation between peak virus titers in the lungs, levels of different proinflammatory cytokines in bronchoalveolar lavage (BAL) fluids, and disease. Vaccination against SIV can greatly reduce or prevent virus replication after challenge and the resulting disease. Here, we took advantage of pigs from vaccination-challenge experiments, with different degrees of virological and clinical protection, to further correlate SIV replication with cytokines and disease. Forty-nine pigs were vaccinated twice with a commercial inactivated SIV vaccine or with experimental vaccines, and 35 control pigs were not vaccinated. Between 2 and 4 weeks after the last vaccination, all pigs were challenged intratracheally with SIV. Twenty-four hours after the challenge, we determined body temperatures, respiratory scores, lung virus titers, and neutrophils and cytokines in BAL fluids. Interferon-alpha (IFN-alpha), tumor necrosis factor (TNF-alpha), interleukin-1 (IL-1), and -6 (IL-6) were determined by bioassay, and IL-8 by a commercial ELISA. The results were analyzed for three comparison groups. The unvaccinated control pigs (group 1, n = 35) were positive for all or most parameters examined. Vaccinated pigs with challenge virus replication in the lungs (group 2, n = 28) had slightly lower virus titers than the challenge control pigs, and clear reductions in disease severity and mean titers of all five cytokines, but neutrophil numbers were not affected. Vaccinated pigs without detectable virus replication (group 3, n = 21) were largely protected against clinical signs and neutrophil infiltration. Mean levels of IFN-alpha, TNF-alpha, and IL-6, but not IL-1 or IL-8, were lower than in both other groups. Virus titers in the lungs of individual pigs showed highly significant correlations with IFN-alpha and IL-6, and lower correlations with TNF-alpha and IL-8. Clinical signs were most closely associated with IFN-alpha, IL-6, and TNF-alpha. The relationship between disease and IL-8 or IL-1 was much weaker. Our data provide further evidence for a role of IFN-alpha, TNF-alpha, and IL-6 in the pathogenesis of SIV. The similarities with cytokine profiles during human influenza virus infection are discussed.

Animals↗
PubMed2001

The clinical, pathological and microbiological outcome of an Escherichia coli O2:K1 infection in avian pneumovirus infected turkeys.

The purpose of this study was to evaluate the effect of an Escherichia coli infection in avian pneumovirus (APV)-infected turkeys. One group of 2-week-old specific pathogen-free (SPF) and two groups of 3-week-old conventional (CON) turkeys were inoculated oculonasally with virulent APV subtype A alone, with E. coli O2:K1 alone or with both agents at varying intervals (1, 3, 5 or 7 days) between the two inoculations. The birds were followed clinically and examined for macroscopic lesions at necropsy. Titres of APV were determined in the turbinates, trachea, lungs and air sacs. The number of E. coli O2:K1were assessed in the turbinates, trachea, lungs, air sacs, liver and heart. In both SPF and CON turkeys, dual infection resulted in an increased morbidity and a higher incidence of gross lesions compared to the groups given single infections, especially with a time interval between APV and E. coli inoculations of 3 and 5 days. APV was isolated from the respiratory tract of all APV-infected groups between 3 and 7 days post inoculation. E. coli O2:K1 was isolated only from turkeys that received a dual infection. It was recovered from the turbinates, trachea, lungs, heart and liver. These results show that APV may act as a primary agent predisposing to E. coli colonization and invasion.

Animals↗
PubMed2001

Efficacy of vaccination of pigs with different H1N1 swine influenza viruses using a recent challenge strain and different parameters of protection.

This study investigates whether antigenic evolution within H1N1 swine influenza viruses can compromise vaccine efficacy and, specifically, whether the A/New Jersey/8/76 strain in the commercial swine influenza vaccines needs to be updated. Pigs were vaccinated twice intramuscularly with experimental monovalent vaccines derived from different H1N1 strains (A/New Jersey/8/76, Sw/Belgium/1/83 or Sw/Belgium/1/98) or with a commercial bivalent vaccine based on A/New Jersey/8/76 (H1N1) and A/Port Chalmers/1/73 (H3N2). Experimental and commercial vaccines contained a different adjuvant. Two weeks after the second vaccination, all pigs were challenged intratracheally with Sw/Belgium/1/98. Mean pre-challenge haemagglutination inhibition (HI) antibody titres against the challenge virus were lower for the experimental A/New Jersey/8/76 vaccine than for the other vaccines. The reduction in mean virus titres in the lungs was highly significant for the latter vaccines, including the commercial New Jersey-derived vaccine, but not for the experimental A/New Jersey/8/76 vaccine. Clinical signs after challenge were negligible in all vaccinates. Post-challenge levels of interferon-alpha and tumor necrosis factor-alpha in bronchoalveolar lavage fluids were reduced in the vaccinates, while levels of interleukin-1 and neutrophils were less consistent. Though the A/New Jersey/8/76 strain is less effective in preventing infection by Sw/Belgium/1/98 than the homologous virus or than Sw/Belgium/1/83, all strains can protect completely if antibody titres against the challenge virus are sufficiently high. Apart from the vaccine strain, adjuvant and antigenic dose may play a crucial role in vaccine efficacy.

Animals↗
PubMed2001

Clinical effects of experimental dual infections with porcine reproductive and respiratory syndrome virus followed by swine influenza virus in conventional and colostrum-deprived pigs.

Previous studies demonstrated that experimental dual infections of pigs with porcine reproductive and respiratory syndrome virus (PRRSV) followed by H1N1 influenza virus cause more severe disease and growth retardation than the respective single virus infections. Here three experiments were undertaken to better define the clinical impact of combined PRRSV-H1N1 infections in conventional and caesarean-derived colostrum-deprived (CDCD) pigs. Groups of pigs were inoculated by aerosol with PRRSV followed by H1N1 at 3-, 7- or 14-day intervals. During the post-H1N1 period, mean body temperatures, respiratory signs and mean weight gains in the PRRSV-H1N1 inoculated groups were recorded and compared with those in uninoculated controls (experiments 1 and 2) or in singly virus-inoculated pigs (experiment 3). In a first experiment with conventional pigs, the PRRSV-3d-H1N1 and PRRSV-7d-H1N1 infections induced mean body temperatures > 40.5 degrees C during 8 days (peaks 41.1 and 41.6 degrees C, respectively) and mean growth reductions of 3.4 and 4.8 kg, respectively, during the 2 weeks after H1N1, along with marked depression and respiratory disease. The PRRSV-14d-H1N1 infection, on the contrary, was largely subclinical. In a second experiment with conventional pigs, PRRSV-3d-H1N1 and PRRSV-7d-H1N1 infections were clinically milder, with smaller increases in mean body temperatures (peak 40.5 degrees C in both groups) and growth reductions (1.4 and 1.6 kg, respectively). In both groups, only one pig showed prominent general and respiratory signs. In a final experiment with CDCD pigs, PRRSV-7d-H1N1 infection had minimal effects on mean clinical performances and growth and, except for one pig that was severely affected, differences with the single virus inoculations were negligible. Thus, both the time interval between infections and the sanitary status of pigs can affect the clinical outcome of dual PRRSV-H1N1 infections. However, factors so far unknown seem to cause large variations in the clinical response between individual pigs.

Animals↗
PubMed2000

Duration of cross-protection between subtypes A and B avian pneumovirus in turkeys.

The degree and duration of clinical and virological cross-protection between avian pneumovirus subtypes A and B were examined in two-week-old pneumovirus antibody-free turkeys. The turkeys were inoculated with either a virulent subtype A (Belgian isolate A/T6/96), a virulent subtype B (Belgian isolate B/T9/96), an attenuated subtype A or an attenuated subtype B, and challenged homologously and heterologously with virulent avian pneumovirus two, five and 11 weeks after inoculation. Birds inoculated with virulent A or B virus showed typical respiratory signs from three to seven days after inoculation. After challenge, no clinical signs were observed in any of the groups, and no virus was isolated from the turkeys that had been initially inoculated with a virulent strain. Virulent virus was recovered from the birds that had been initially inoculated with attenuated subtypes and challenged five and/or 11 weeks later with a heterologous virulent strain. Birds challenged after five weeks showed a serological booster reaction only when they had been inoculated initially with a virulent or attenuated subtype B and challenged with subtype A. Seroconversion was observed in all the groups challenged after 11 weeks except when they had been inoculated initially with attenuated subtype B and challenged with subtype B.

Animals↗
PubMed1999

Prevalence of herds with young sows seropositive to pseudorabies (Aujeszky's disease) in northern Belgium.

In Belgium, pseudorabies in swine has been the subject of a mandatory eradication programme since 1993. From December 1995 to February 1996, a survey was conducted in the five provinces of northern Belgium to estimate the provincial pseudorabies virus (PRV) herd seroprevalence. Seven hundred and twenty randomly selected herds were included in this survey. To detect recently infected animals, only young sows were sampled. The results show that 44% of these herds had an important number of PRV-seropositive young sows. The highest herd seroprevalence was observed in West Flanders (68%), followed by Antwerp (60%), East Flanders (43%), Limburg (18%), and Flemish Brabant (8%). Assuming a diagnostic test sensitivity and specificity of 95% and 99%, respectively, and a true PRV within-herd prevalence of 43%, the overall true PRV herd prevalence was estimated to be 35%. A logistic multiple-regression revealed that the presence of finishing pigs was associated with a two-fold increase in odds of a herd being seropositive (odds ratio (OR)=2.07, 95% confidence interval (CI) = 1.31-3.26); a breeding herd size > or =70 sows was associated with a four-fold increase in odds of a herd being seropositive (OR = 4.09, 95% CI = 2.18-7.67); a pig density in the municipality of >455 pigs/km2 was associated with a 10-fold increase in odds of a herd being seropositive (OR = 9.68, 95% CI = 5.17-18.12). No association was detected between the PRV herd seroprevalence and purchase policy of breeding pigs (purchased gilts, or use of homebred gilts only).

Animal Husbandry↗
PubMed1999

Differential production of proinflammatory cytokines in the pig lung during different respiratory virus infections: correlations with pathogenicity.

The acute stages of infection with swine influenza virus (SIV), porcine respiratory coronavirus (PRCV) and porcine reproductive-respiratory syndrome virus (PRRSV) were shown to differ in terms of clinical and lung inflammatory effects and proinflammatory cytokine profiles in bronchoalveolar lavage (BAL) fluids. Caesarian-derived colostrum-deprived pigs were inoculated intratracheally with one of the three viruses. SIV infection was followed within 1 day post inoculation (d PI) by characteristic respiratory and general signs, and excessive lung epithelial desquamation and neutrophil infiltration (38 to 56 per cent of BAL cells at 1 d PI vs 0 to 1 per cent in controls). High concentrations of bioactive interferon-alpha (IFN -alpha), tumour necrosis factor-alpha (TNF -alpha) and interleukin-1 (IL -1) coincided with peak symptoms and neutrophil infiltration. PRCV infection was asymptomatic and produced a mild bronchointerstitial pneumonitis and neutrophil infiltration (13 to 22 per cent of BAL cells at 4 d PI). IFN -alpha titres parallelled those found during SIV infection, TNF -alpha was negligible and IL -1 undetectable. PRRSV infection induced anorexia and lethargy between 3 and 5 d PI. There was marked infiltration with mononuclear cells in alveolar septa and BAL fluids between 7 and 10 d PI, while neutrophils remained at less than 11 per cent of BAL cells at any time. IL -1 was produced from three throughout 10 d PI, while IFN -alpha production was minimal and TNF -alpha undetectable. These data strongly suggest that proinflammatory cytokines can be important mediators of viral respiratory disease.

Animals↗
PubMed1998

In vivo and in vitro interferon (IFN) studies with the porcine reproductive and respiratory syndrome virus (PRRSV).

Some of the interactions between the porcine reproductive and respiratory syndrome virus (PRRSV) and the porcine interferon-alpha (IFN-alpha) system were studied. In a first experiment, it was shown that pretreatment of primary porcine alveolar macrophages (AMs) with recombinant porcine (rPo) IFN-alpha 1 resulted in significant reductions of PRRSV yield and numbers of antigen expressing cells. In a second experiment, sensitivity of PRRSV to IFN-alpha was confirmed in vivo. In pigs inoculated with porcine respiratory coronavirus (PRCV)--a potent inducer of endogenous IFN-alpha in the lungs of pigs--followed 2 days later by PRRSV--lung PRRSV titers were 1.7 to 2.9 log10 TCID50 reduced compared to those in singly PRRSV inoculated pigs. It was concluded therefore that PRRSV has a fairly good sensitivity to the antiviral effects of IFN-alpha. A third experiment documented that in vivo PRRSV infection generally does not affect PRCV-induced IFN-alpha production in the lungs of pigs. In addition, it was shown that the IFN-inducing capacity of PRRSV is at least 159 times lower than that of PRCV. This finding suggests that cells other than AMs may be responsible for IFN production in the lungs of pigs.

Animals↗
PubMed1998

Bronchoalveolar interferon-alpha, tumor necrosis factor-alpha, interleukin-1, and inflammation during acute influenza in pigs: a possible model for humans?

Biologically active interferon-alpha, tumor necrosis factor-alpha (TNF-alpha), and interleukin-1 (IL-1) were detected in bronchoalveolar lavage (BAL) fluids of 3-week-old cesarian-derived colostrum-deprived pigs inoculated with H1N1 influenza virus. Cytokine titers and lung virus titers were significantly higher 18-24 h after inoculation than at 48-72 h after inoculation in all 4 litters of pigs examined. All three cytokines were positively correlated with a 3- to 4-fold increase in BAL cell numbers (P < .036) and with a drastic neutrophil infiltration (24%-77% of BAL cells vs. 0-1.5% in controls) (P < .001). In addition, cytokine production coincided with the onset of general and respiratory symptoms of influenza and with the development of a necrotizing bronchopneumonia. This study is the first demonstration of TNF-alpha and IL-1 in BAL fluids of a natural influenza virus host. It documents that pigs may be a highly valuable experimental model in human influenza virus pneumonia.

Animals↗
PubMed1998

Infections and reinfections with avian pneumovirus subtype A and B on Belgian turkey farms and relation to respiratory problems.

A longitudinal study was performed on six turkey farms in order to determine whether infections with avian pneumovirus (APV) occur and if they are related to outbreaks of respiratory problems in Belgium. Blood was taken at 1-3 week intervals of 20 identified animals during the fattening period. On five farms, the turkeys seroconverted against APV shortly after the appearance of respiratory problems. On two farms, where the animals had not been vaccinated against APV, attempts were made to isolate APV during the outbreaks. Two isolates were obtained: one of subtype A, the other of subtype B. These results indicate that the respiratory problems on five farms were related to an infection with APV. A second increase in APV antibody titres detected on four farms at the end of the fattening period, indicates that reinfections frequently occur. This is, to our knowledge, the first report on the isolation of an APV subtype A on the continent.

Animals↗