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Biomedical subjects

M Pensaert

Publications and source records attributed to M Pensaert.

At least 37 records · Page 2Linked to original sources
PubMed1996

Dual infections of feeder pigs with porcine reproductive and respiratory syndrome virus followed by porcine respiratory coronavirus or swine influenza virus: a clinical and virological study.

Dual infections of pigs with porcine reproductive and respiratory syndrome virus (PRRSV) followed by a second common respiratory virus, either porcine respiratory coronavirus (PRCV) or swine influenza virus (SIV), were studied. The aim was to determine if dual infections, as compared to single virus infections, result in enhanced clinical manifestations. It was also examined if PRRSV replication affects replication of PRCV or SIV in the respiratory tract. Groups of conventional 10 week old pigs were inoculated with PRRSV-only (3 pigs), PRCV-only (4 pigs) or SIV-only (4 pigs). Dual inoculations with PRRSV-PRCV (4 pigs) and PRRSV-SIV (3 groups of 4, 4 and 5 pigs) were performed at a 3 day interval. A group of uninoculated control pigs (8 pigs) was included. The infection with PRRSV-only induced a transient fever (40.2 degrees C) at 2 DPI, but no respiratory signs. The PRCV-only infection remained subclinical. The SIV-only infection resulted in a one day fever (40.1 degrees C) with moderate tachypnoea and dyspnoea. Mean weight gain in the virus-inoculated groups was retarded compared with the control group. The PRRSV-PRCV infection induced a 9 day lasting fever (peak 40.9 degrees C) with tachypnoea, dyspnoea and productive coughing. The PRRSV-SIV infection resulted in fever and respiratory signs in all 3 groups. Clinical signs, however, were more pronounced in group 1 than in groups 2 and 3. Pigs of group 1 showed fever during 10 days (peak 41.4 degrees C), tachypnoea, marked dyspnoea with abdominal breathing, and a productive cough. Pigs of groups 2 and 3 had fever for 5 and 3 days (peaks 40.6 and 40.3 degrees C) respectively and mild respiratory disorders. Mean weight gain during 14 DPI of the 2nd virus was 5.9 kg in the PRRSV-PRCV group and 4.0, 6.8 and 6.7 kg in PRRSV-SIV groups 1, 2 and 3 respectively. Mean weight gain during the corresponding period in the PRRSV-only group was 8.6 kg. It was concluded that dual infections with viruses causes more severe disease and growth retardation than single PRRSV infection. PRCV excretion curves were similar in single and dual virus inoculated groups. Excretion of SIV was delayed by 2 days in the dual inoculated pigs. Thus, replication of the second virus is not (PRCV) or only slightly (SIV) affected by a prior infection with PRRSV.

Animals↗
PubMed1996

An adenovirus recombinant expressing the spike glycoprotein of porcine respiratory coronavirus is immunogenic in swine.

The full-length spike (S) gene of porcine respiratory coronavirus (PRCV) was inserted into the genome of human adenovirus type 5 downstream of the early transcription region 3 promoter. The recombinant virus replicated in cultures of the swine testicle ST cell line and directed the synthesis of S antigen with a maximum yield of approximately 26 micrograms per 10(6) cells. The antigen was cell-associated except in the late phase of the infection, when a small amount (3.5 micrograms per 10(6) cells) was released. The cell-associated antigen consisted of polypeptides of molecular mass 160 kDa and 175 kDa, comigrating with the authentic precursor S' and the mature S protein of PRCV, respectively. The extracellular recombinant antigen corresponded to the 175 kDa mature protein. Some recombinant S protein was exposed on the cell surface and was recognized by neutralization-mediating anti-S monoclonal antibodies. Piglets, inoculated oronasally with the recombinant adenovirus vector developed PRCV-neutralizing serum antibodies and were partially protected against PRCV challenge, demonstrating the potential of live adenovirus as vaccine vector.

Adenoviruses, Human↗
PubMed1995

Expression and immunogenicity of the spike glycoprotein of porcine respiratory coronavirus encoded in the E3 region of adenovirus.

The full length spike (S) gene of porcine respiratory coronavirus (PRCV) was inserted into the genome of human adenovirus type 5 downstream of the early transcription region 3 promoter. The recombinant virus replicated in cultures of the swine testicle ST cell line and directed the synthesis of S antigen to an amount of approximately 33 micrograms per 10(6) cells, as determined by ELISA. The antigen was cell-associated except in the late phase of the infection, when a low amount (4 micrograms per 10(6) cells) was released in the culture supernatant. The cell-associated antigen consisted of 2 polypeptides of 160 K and 175 K, respectively. The 160 K polypeptide comigrated with the authentic S' precursor from PRCV-infected cells. The 175 K polypeptide had the same mobility as the authentic mature S protein from PRCV-infected cells and from PRCV released in the supernatant. The extracellular recombinant antigen corresponded with the 175 K mature protein. Immunofluorescent staining gave evidence that some recombinant S protein was exposed on the cell surface; it also showed that the protein was recognized by conformation-specific anti-S monoclonal antibodies. Piglets, immunized oronasally with the recombinant adenovirus vector developed PRCV-neutralizing serum antibodies and were partially protected against PRCV-challenge.

Adenoviruses, Human↗
PubMed1995

A serological study on infection patterns, control and persistence of classical swine fever in infected farms in the Philippines.

In 3 farrow-to-finish farms with enzootic classical swine fever (CSF) all sick pigs were culled and an intensive vaccination program was introduced. Boars and cows were vaccinated every 6 months and piglets at the age of 6 and 8 weeks. The infection was monitored on clinical grounds and by means of serological examination of the farms. Serological results reflected well the clinical situation in the farms. High titers and high percentage of animals with positive titers were observed in infected farms, compared to lower titers in a clinically "free" farm, which were interpreted as titers due to vaccination. Although clinical improvement was noticed, the rigid vaccination regime was not able to control CSF in none of the farms. In all cases, a small percentage of pigs in the finishing stage was still affected. Since these pigs seemed not to have responded to vaccination at 6 and 8 weeks of age, the programme was questioned. Additionally, very high titers were recorded in sows from infected farms, which would automatically extend the period of passive protection in offspring and postpone the age at which piglets could be vaccinated. More intensive programmes, which include also vaccination beyond the age of 8 weeks, were suggested to bring enzootic infections under control.

Aging↗
PubMed1994

Prevalence of infections with enzootic respiratory and enteric viruses in feeder pigs entering fattening herds.

The prevalence of infections with H1N1- and H3N2-influenza viruses, porcine respiratory coronavirus (PRCV), transmissible gastroenteritis virus (TGEV) and porcine epidemic diarrhoea virus (PEDV) in feeder pigs shortly after their entry into fattening units was examined. Ten groups of pigs with acute respiratory disease during the months September to October 1991 and seven groups of pigs with acute diarrhoea during the months February to March 1992 were investigated. On arrival in the fattening herds, more of the pigs were negative for antibodies against H1N1-influenza virus and against PRCV during September to October (61 and 50 per cent, respectively) than in February to March (51 and 34 per cent, respectively). There was serological evidence of a triple infection with PRCV and both influenza viruses in seven of the 17 groups; dual infections with PRCV and H1N1-influenza virus occurred in nine groups and with H1N1- and H3N2-influenza viruses in one group. Seroconversion against TGEV was not detected in any of the 17 groups, but seven of them had seroconverted to PEDV. Multiple infections with PRCV and either one or both of the influenza viruses were thus very common shortly after the introduction of feeder pigs into the fattening herds. There was no association between the type and/or multiplicity of these infections and respiratory disease, but infections with PEDV were clearly associated with outbreaks of diarrhoea.

Animals↗
PubMed1994

Influence of vaccine medium and vaccination schedules on the induction of active immunity against Aujeszky's disease in maternally immune pigs.

Active immunity against Aujeszky's disease virus (ADV) was compared at the end of the fattening period in pigs which had been vaccinated with the attenuated Bartha strain according to different schedules in the presence of different levels of maternal immunity. The percentage of seropositive pigs at the end of the fattening period varied from 21 to 94 per cent. The percentage was significantly higher when the vaccination schedules were applied to pigs from mothers vaccinated with an attenuated strain compared to pigs from mothers vaccinated with a subunit vaccine or from infected-immune mothers. Additionally, this percentage was two to three times lower when pigs were vaccinated once at 10 weeks old compared to pigs either revaccinated at 14 weeks or vaccinated once at 14 weeks old. When the virus strain used for vaccination had been suspended either in saline or in an oil-in-water emulsion, significant differences were not found in the serological response after vaccination and in the reduction of virus excretion upon subsequent challenge. In challenge experiments, a significantly longer duration of virus excretion was observed in vaccinated pigs which had not seroconverted than in vaccinated but seropositive pigs. The vaccination schedules for sows and fattening pigs in view of the eradication of ADV are discussed.

Animals↗
PubMed1993

A sero-epizootiological study of porcine respiratory coronavirus in Belgian swine.

A porcine respiratory coronavirus (PRCV), antigenically closely related to transmissible gastroenteritis virus (TGEV), appeared in the European swine population in 1984. The present serological study was performed to obtain insight into the epizootiology of PRCV and of TGEV. PRCV-induced neutralizing antibodies were found in 90.6 per cent of the 160 sera collected from sows at slaughter, demonstrating the enzootic appearance of PRCV in the Belgian swine population. A serological study of fattening swine on 33 farms revealed that 11 farms situated in an area with a high farm density (all farms within 4 km2) and 11 on 22 closed breeding-fattening farms situated in areas with a low farm density (only one to four farms per 12 km2) were infected with PRCV throughout the year, whereas the other 11 closed breeding-fattening farms were temporarily free of PRCV. PRCV disappeared from the farms mainly in spring and summer. All the 11 farms became reinfected in autumn or winter, indicating that PRCV is regularly reintroduced in farms in the colder seasons. There was no correlation between the herd size and the temporary disappearance of PRCV from farms. It was observed on some farms that PRCV could infect pigs shortly after weaning in the presence of declining maternal antibodies, indicating that PRCV can persist on a farm by regularly infecting newly weaned pigs. TGEV-specific antibodies were found in 7.6 per cent of the 160 sera from the slaughterhouse sows. TGEV-specific antibodies were also detected in sera from fattening swine of 5 of the above mentioned 33 farms. TGEV-outbreaks were not observed on these farms.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Porcine respiratory coronavirus: molecular features and virus-host interactions.

Since 1984, a previously unrecognized respiratory coronavirus, causing a mostly unapparent infection, has rapidly and massively spread within the swine population in Europe, and few years later, a virus with similar characteristics has been identified in the USA. The agent, designated PRCV, appears to be derived from the porcine enteric coronavirus TGEV. The aim of the present article is to review comprehensively the state of the knowledge about this new virus and its infection. The review includes the following topics: epizootiology, molecular characterization and antigenic features of PRCV, pathogenesis and clinical aspects, immunity and laboratory diagnosis. The authors' views concerning the impact of the emergence of PRCV on both coronavirus research and swine production are presented in the conclusion.

Amino Acid Sequence↗
PubMed1992

Round table on control of Aujeszky's disease and vaccine development based on molecular biology.

A summary is given on the 4 topics which were discussed during the round table and which represent current knowledge on the molecular biology of Aujeszky's disease (pseudorabies) virus. They include a review on 1. the genome and gene products of the virus; 2. the viral genes associated with virulence; 3. the immunological role of the viral gene products and 4. studies intended to compare the efficacy of several commercially available vaccines and to establish a possible correlation between antibodies against individual structural viral proteins and degree of protection. It was concluded that gI deleted vaccines appear to be the best choice for use in intensive vaccination programmes towards eradication of Aujeszky's disease virus. However, there remains a need for development of more potent vaccines which induce strong humoral and cell mediated immune responses and afford complete protection, virological protection included. It is often observed that live vaccine strains which are completely avirulent lose much capacity to replicate and spread within the vaccinated animal. It is, however, not excluded that a certain degree of dissemination may be needed to be fully efficacious. Loss of virulence may thus be accompanied by too much loss of immunogenicity. An improved genetic stability of live vaccine strains when they are obtained by genetic manipulation, possibly justifies a more widespread dissemination of the vaccine strain in the body compared to that with conventionally developed strains or compared to what is presently allowed.

Animals↗
PubMed1992

Field experiments to evaluate the feasibility of eradication of Aujeszky's disease virus by different vaccination schedules.

In the present report, the extent of the reduction in Aujeszky's disease virus (ADV) dissemination achieved when pigs were intensively vaccinated with gI-deleted vaccines under field circumstances, was examined. On widely dispersed breeding-fattening farms, a gI-negative status was most rapidly obtained and the rate of new waves of infections was lowest when the attenuated Bartha strain was administered to both the sows and the fatteners. It was more difficult not only to reach but also to keep a gI-negative status on farms on which the sows were vaccinated with an inactivated vaccine and the fatteners with the attenuated Bartha strain or when the fattening pigs were not vaccinated at all. In a densely populated area, 9 of the 17 farms had gI-positive fatteners at the start of the intensive vaccination programme in which the attenuated Bartha strain was given to both the sows and the fatteners. Antibodies were not detected in the sera of the fatteners of each farm at some time during the experiments, but the fatteners on 7 of the 18 farms still showed antibodies against gI after 20 months of vaccination. At the end of the experiment, the percentage of fatteners with antibodies on these farms was markedly reduced compared with the percentage at the start of the experiment. Therefore, elimination of field virus may be feasible if intensive vaccination is carried out over a sufficiently long period of time. However, the high rate of reinfections experienced either due to reintroduction of the virus or to recrudescence should be a warning against too much optimism, particularly in regions with a dense swine population.

Animals↗
PubMed1992

Control of product batches (before and after registration). The Belgian approach.

A review is given on the registration procedure and controls of veterinary vaccines in Belgium. An obligatory registration procedure was installed in 1969, and has since been modified several times. The Belgian approach for control of veterinary vaccines before and after registration is explained. Controls before registration are often carried out exclusively by the manufacturer and are described in the registration file. Controls may, however, also be carried out by an independent laboratory if the manufacturer so desires. In general, the procedures described in a national or European Pharmacopoeia must be applied if a monograph is available. Batch control after registration is carried out by the manufacturer. When manufactured in Belgium, controls on the finished product must also be carried out by the Institute of Hygiene for viral vaccines and some selected bacterial vaccines (e.g. anthrax). In addition, all batches of imported vaccines are subject to controls both by an officially accepted laboratory and by the Institute of Hygiene, the first to be paid by the importer, the second free of charge. Batch controls include homogeneity of the batch, labelling, storage conditions and also identity of active component(s), safety, sterility, absence of extraneous agents and potency. The potency test described in the original registration file must be used for batch control.

Animals↗
PubMed1990

Induction of milk IgA antibodies by porcine respiratory coronavirus infection.

An ELISA was developed to examine the prevalence of TGEV-specific immunoglobulin (Ig)A in the milk of sows, infected in the field with PRCV or with TGEV. It was shown that previous PRCV-infections can induce the secretion of IgA antibodies in the milk. However, only 9 out of 28 PRCV-infected sows had IgA in their milk whereas 11 TGEV-infected sows all secreted IgA. On farms where a reinfection with PRCV occurred, the number of IgA-secreting sows increased from 2 to 11 on a total of 13 sows. This showed that the presence of IgA antibodies in the milk may depend upon the occurrence of reinfection with PRCV. As demonstrated by density gradient analysis, the milk IgA induced by PRCV was 11S secretory IgA and had the capacity to neutralize TGEV.

Animals↗
PubMed1990

Sites of replication of a porcine respiratory coronavirus in 5-week-old pigs with or without maternal antibodies.

On farms, where the porcine respiratory coronavirus (PRCV) is enzootic, pigs usually become infected between 5 and 10 weeks of age while losing their maternal antibodies. It was examined whether PRCV replicates in the small intestine in such pigs. This point is important since intestinal replication with PRCV might induce immunity against TGEV not only by stimulating mucosal intestinal immunity, but also by the induction of a lactogenic IgA response at later age via the gut-mammary link. Five week old pigs with and without maternal antibodies were inoculated by aerosol or directly into the intestinal lumen. In aerosol inoculated pigs, virus replication was observed to high titres in the respiratory tract. Replication occurred in epithelial cells of nasal mucosa, trachea, bronchi bronchioli and alveoli and in alveolar macrophages. Small amounts of virus produced in the respiratory tract were ingested, but no intestinal replication of PRCV was demonstrated. Differences were not observed in virus titre and sites of replication in seronegative pigs compared to those in pigs with maternal antibodies. Upon inoculation of 10(5) or 10(7) TCID50 directly into the lumen of the cranial jejunum, no intestinal replication could be demonstrated.

Animals↗
PubMed1988

Porcine epidemic diarrhea virus (CV 777) and feline infectious peritonitis virus (FIPV) are antigenically related.

Using gut sections from pigs infected with porcine epidemic diarrhea virus (strain CV 777) and ascitic fluid from cats which had succumbed to feline infectious peritonitis (FIP), a weak cross reaction was found by immunofluorescence. Its specificity was confirmed when detergent-treated purified CV 777 showed a prominent reaction with FIPV antibodies in ELISA; no reaction was obtained with intact virions, which indicated common determinants on an internal component of the particle. Antigenic cross-reactions at the nucleocapsid level were found in Western blot ELISA performed both ways (CV 777/FIPV antibodies; FIPV/CV 777 antibodies). In immunoprecipitation using [35S]methionine labelled FIPV, anti-CV 777 sera recognized exclusively the nucleocapsid protein. The significance of these findings for the classification of coronaviruses is discussed.

Animals↗
PubMed1988

Influenza in swine in Belgium (1969-1986): epizootiologic aspects.

From 1984 until 1986, influenza isolates were obtained from 59 outbreaks of respiratory tract disease in Belgium. In 21 of the outbreaks, H3N2-influenza virus isolates, related to the human A/Port Chalmers/1/73 strain were obtained. All other isolates were H1N1-influenza virus strains. The prevalence of variants of the human H3N2-influenza virus in the Belgium swine population was determined by examining sow sera which had been collected between 1969 and 1984. The results of this serological study showed that, although a Port Chalmers-like strain was associated with outbreaks of respiratory tract disease in swine only since 1984, such strain was already present in the swine population in 1974, when a low percentage of sow sera (7%) reacted with A/Port Chalmers/1/73. Between 1975 and 1984, antibody against this strain were present in 28-61% of the sera. Furthermore, 3-6% of the sera collected between 1971 and 1980 reacted with the A/Hong Kong/1/68 strain. There were no indications that more recent human H3N2-strains (A/Texas/1/77, A/Bangkok/1/79 and A/Belgium/2/81) circulated in the Belgian swine population.

Animals↗
PubMed1988

Antigenic differentiation between transmissible gastroenteritis virus of swine and a related porcine respiratory coronavirus.

The antigenic relationship between a recently isolated porcine respiratory coronavirus (TLM 83) and transmissible gastroenteritis (TGE) virus of swine was studied by neutralization, immunoblotting and radioimmunoassay (RIA) using TGE virus-specific monoclonal antibodies (MAbs) and polyclonal antibodies specific for both viruses. A complete two-way neutralization activity between the two viruses was found. Immunoblotting revealed cross-reactions between TLM 83 and TGE virus antigens at the level of the envelope protein (E1), the nucleoprotein (N) and the peplomer protein (E2). By virus neutralization assays and RIA with TGE virus-specific MAbs, the presence of similar epitopes in the E1 and N proteins and in the neutralization-mediating antigenic site of the E2 protein were demonstrated. E2 protein-specific MAbs, without neutralizing activity and reacting with antigenic sites B, C and D (previously defined), failed to recognize TLM 83. These results indicated a close antigenic relationship and structural similarity between TLM 83 and TGE viruses and also suggested potential ways of differentiating between the two viruses.

Antibodies, Monoclonal↗