[Risks of infection in xenotransplantation: what are they and how are they to be controlled?].

Porcine grafts are a potential source of pathogenic agents capable of contaminating the recipient. The spread of porcine retroviruses in the patient's tissues is a major risk that must be rigorously evaluated. The control of the microbiological state of the pig donor, concerning retroviruses and other pathogens, is the necessary condition for controlling this risk.

Specific cytotoxic lymphocyte response in swine against structural proteins of transmissible gastro-enteritis virus: a study using lymphoblastoid cell line and recombinant vaccinia virus.

To determine the specificity, if any, of cellular cytotoxicity against transmissible gastro-enteritis virus (TGEV) infected cells, we developed a test using B lymphoblasts from a MHC histocompatible (d/d haplotype) cell line (L14), as stimulating and target cells. These cells were previously infected with recombinant vaccinia virus including different TGEV structural genes, either the spike (vS), membrane (vM) or nucleoprotein gene (vN). Lymphocytes from a TGEV immunized (d/d) swine developed a cytotoxic activity after secondary in vitro stimulation in the presence of vS, vM or vN infected L14 cells.

Transmissible gastroenteritis coronavirus: the development and applications of the fixed-cell immunoperoxidase technique.

Since the first demonstration in 1971 that solid-phase enzyme-linked immunosorbent assays (ELISAs) could be used for the quantitative determination of antigens and antibodies, this method has been widely applied in serodiagnosis of parasitic and infectious diseases. In addition to the classic ELISA variants using antigen or antibody to coat the plastic plates, there has recently been growing interest in the application of fixed-cell ELISA to research and diagnostic work on viral diseases. The authors discuss the development and applications of this technique to basic research and diagnosis of transmissible gastroenteritis, a highly contagious disease of swine.

The use of PCR genome mapping for the characterisation of TGEV strains.

Previous studies on different transmissible gastroenteritis virus (TGEV) strains, including porcine respiratory coronavirus (PRCV), have identified regions within the genome that are polymorphic as regards insertions and deletions. For example the 672 base deletion within the S gene and multiple deletions 5', within and 3' of the ORF-3a gene were detected in strains of PRCV. The presence of deletions may be associated with a change in the virulence, attenuation or tissue tropism of the isolate.

Induction of lactogenic immunity to transmissible gastroenteritis virus of swine using an attenuated coronavirus mutant able to survive in the physicochemical environment of the digestive tract.

A transmissible gastroenteritis (TGE) coronavirus mutant (188-SG), selected as attenuated and resistant to acidity and proteases of the digestive tract of adult pigs, was used as vaccine ("Nouzilly strain") in sows to protect suckling piglets against a challenge exposure carried out with a highly virulent TGEV strain. The pregnant sows were immunized once (42-49 days before farrowing) or twice (42-49 and 7-15 days before farrowing) by the oral, intramuscular or conjunctival route with the 188-SG strain. Sows exposed to virulent TGEV in the field and experimentally infected sows (two oral inoculations during pregnancy) were used as positive controls leading to high protection.

Lactogenic immunity to transmissible gastroenteritis (TGE) of swine induced by the attenuated Nouzilly strain of TGE virus: passive protection of piglets and detection of serum and milk antibody classes by ELISA.

Piglets of eight sows vaccinated by different routes with the attenuated TGE mutant coronavirus, Nouzilly (N) strain, and piglets from two field seropositive sows were challenged with a virulent TGE strain. On the day of challenge and 10 days after challenge, milk and serum samples from sows were analysed for their level of neutralizing antibodies, total immunoglobulin classes and TGE antibody classes by an ELISA. No direct relationship was seen between the level of protection of the litters and the titres of the different antibody classes on the day of challenge.

Natural infection with the porcine respiratory coronavirus induces protective lactogenic immunity against transmissible gastroenteritis.

Our objective was to evaluate the level of passive protection against transmissible gastroenteritis (TGE) among 57 newborn piglets nursing from seven seropositive sows previously naturally infected with porcine respiratory coronavirus (PRCV). After challenge exposure we observed mortality rates of 44% for litters of seven PRCV-infected sows, 40% for litters of four sows orally immunized with the attenuated TGEV strain Nouzilly, and 91% for litters of seven seronegative susceptible sows. A blocking ELISA with two appropriate monoclonal antibodies distinguished serological responses of PRCV-infected sows from those of TGEV-immunized sows.

Lactogenic immunity to transmissible gastroenteritis (TGE) of swine induced by the attenuated Nouzilly strain of TGE virus: neutralizing antibody classes and protection.

An attenuated TGE coronavirus mutant (Nouzilly strain) relatively resistant to acidity and digestive enzymes was used for immunization of 11 seronegative pregnant sows, mainly by the oral route. Nouzilly strain is able to induce a protective lactogenic immunity in suckling piglets against severe virulent TGE challenge. However the level of neutralizing activity in serum and milk of vaccinated sows at the time of challenge exposure is not correlated with passive protection rate.

A cytotoxic murine monoclonal antibody that recognizes a porcine T cell subset involved in lectin-induced proliferation.

A panel of cytotoxic monoclonal antibodies (Moab) derived from mice immunized with porcine thymocytes has been developed which reacts with monomorphic determinants on porcine peripheral blood lymphocytes (PBL). These Moab recognized from 25% to 100% of PBL as tested by flow microfluorimetry One of the Moab (PT 81) that bound 39% of PBL, 30% of splenocytes and 65% of thymocytes as determined by flow microfluorimetry was selected for initial characterization. PT 81 specifically lysed 37% of Ficoll/Hypaque-prepared PBL depleted of monocytes by carbonyl iron ingestion.

Transmissible gastroenteritis (TGE) of swine: in vitro virus attachment and effects of polyanions and polycations.

Four transmissible gastroenteritis virus (TGEV) strains (Purdue-115, D-52, 188-SG and Gep-II) and two cell lines (swine testis-ST and pig kidney-RPD) were used to study virus attachment and cell susceptibility. Virus attachment was partially thermodependent and the rate varied, depending on the strain. Identical TGEV inocula produced a higher plaque number by plaque assay in the swine testis cell line (ST) than in the pig kidney cell line (RPD) but [3H]uridine-labelled virus was found associated equally well with both cell lines.

Effect of deoxycholate, amphotericin B and fongizone on transmissible gastroenteritis coronavirus.

At a concentration of 2 μg/ml, neither amphotericin B nor deoxycholate had an inactivating effect upon transmissible gastroenteritis Coronavirus in-fectivity. However, amphothericin B stimulated plaque formatin in agarose and facilitated the entry of viral RNA into swine testis cells. The combination of amphotericin B + deoxycholate inactivated virus infectivity and induced a decrease in plaque diameter.

Étude comparée de trois souches du coronavirus de la gastroentérite transmissible: Conditions de la réplicationvirale et de la synthèse des antigènes structuraux.

Purdue-115 and D-52 strains of TGEV were compared with the 188-SG strain, which was obtained by means of a survivor selection process in gastric juice of adult pig. The 188-SG strain was characterized by (a) low infectivity, (b) delayed and restricted growth associated with low and delayed RNA synthesis, and (c) a high content of structural antigens. In contrast, Purdue-115 and D-52 strains were characterized by (a) high infectivity, and (b) a normal pattern of virus replication and RNA and structural antigen synthesis.

[Influence of concanavalin A on the attachment of the coronavirus of transmissible gastroenteritis in cell cultures].

Effect of Concanavalin (ConA) on attachment of three strains of Transmissible Gastroenteritis coronavirus (TGE) of swine was investigated in cell culture. Whatever the virus strain, reduction of virus plaques number is observed when viral suspension is incubated with cells together or after addition of ConA. Intensity of inhibition is related with ConA concentration.

Detection of transmissible gastroenteritis coronavirus antigens by a sandwich enzyme-linked immunosorbent assay technique.

A new sandwich enzyme-linked immunosorbent assay, using monoclonal and polyclonal antibodies, was developed to detect transmissible gastroenteritis virus antigens from cell culture and from intestinal wash or feces obtained from experimentally infected pigs. This technique was shown to be suitable for the detection of virulent field strain unadapted to cell culture. Cross reactions had not been observed with other enteric pathogens, rotavirus, porcine epizootic diarrhea virus, and Escherichia coli.

Neutralizing secretory IgA and IgG do not inhibit attachment of transmissible gastroenteritis virus.

Secretory IgA (sIgA) and IgG from porcine milk and serum, respectively, [3H]uridine-labelled virus, swine testis and pig kidney cell lines were used to examine the neutralized virus-cell interaction. Transmissible gastroenteritis virus (TGEV), 99.99% neutralized by immunoglobulin, was able to attach to the cells.

Transmissible gastroenteritis (TGE) of swine: survivor selection of TGE virus mutants in stomach juice of adult pigs.

Two transmissible gastroenteritis (TGE) virus mutants (188-SG and 152-SG) were obtained from a low-passage virus strain (D-52) by 188 and 152 cycles of stomach juice treatment and multiplication in cell culture. Compared to the high-passage Purdue-115 and the original D-52 strains, these mutants were more stable at pH 2.0, more resistant to pepsin and trypsin, and characterized by a small plaque phenotype.

Conditioned taste aversion suppresses induction of delayed-type hypersensitivity immune reactions.

Conditioned taste aversion was induced in mice by pairing saccharin drinking with an intraperitoneal injection of lithium chloride, a toxic but nonimmunosuppressive drug. Conditioned mice showed not only suppressed saccharin drinking but also a 75% reduction in the induction of delayed-type hypersensitivity immune responses to low doses of sheep erythrocytes. This effect was observed with doses of lithium chloride which had no effect of their own on immune functions.

[Transmissible gastroenteritis of swine: stability of coronavirus in gastric and intestinal contents].

Low and high passaged cell culture strains of TGE coronavirus were examined for stability in gastric and small intestine juices collected in 3-6 month-old pigs killed at different times after last feeding. Results revealed high fragility of the TGE virus in these digestive liquids. Differences in stability were observed between strains of TGE virus.

[Transmissible gastroenteritis: vaccination of sows in contaminated environment using inactivated virus in oil emulsion].

An oil emulsion vaccine against TGE was prepared using a virus suspension produced in tissue culture and inactivated by formaline. Intramuscular vaccination trials were performed on sows in the field from two herds (167 sows) which had been infected by TGE virus more than one year previously. Considering qualities of immunity after natural infection, the objective of the work was to try to give a new impetus to immunity in such herds using vaccination as a booster.

[Induction of immunosuppression by dietary aversion acquired in the absence of immunosuppressive treatment].

Conditioned taste aversion induced by either an immunosuppressive (cyclophosphamide) or non immunosuppressive (lithium chloride) drug reduced expression of a T cell mediated immune response that is highly susceptible to stress hormones. These results demonstrate that the proposed concept of conditioned immunosuppression really represents another example of how stress can alter normal regulation of cell mediated immune events.

[Hog cholera: immunization of young pigs with the Thiverval strain vaccine in the presence of colostral immunity].

The vaccination of young piglets, with or without passive antibodies of colostral origin, was studied using the Thiverval strain. The various experiments, carried out under practical conditions, allowed us to observe the following phenomena:--in piglets without immunity of maternal origin we observed a classic primary reaction, with vigourous, lasting production of antibodies and resistance to the challenge;--in piglets with immunity of maternal origin, depending on when the vaccination was administered, the production of primary antibodies was non-existent or deficient; however, we noted that piglets vaccinated 35 days after birth resist the challenge.

[Hog cholera virus: influence of colostral passive antibody on immune response of pig following vaccination with the rabbit adapted Chinese strain (author's transl)].

Using the rabbit adapted chinese strain of Hog cholera, active immunization of piglets having passive colostral antibodies was studied. 65 piglets born from 11 sows were used. Concerning sows, vaccination was performed 5-6 months and 1 month before service (3 sows), 30 days (2 sows) and 60 days (3 sows) after service.

Comparison of the immune response in serum and bucco-pharyngeal secretions following immunization by different routes with a live hog cholera virus vaccine (Thiverval strain).

The influence of vaccination route on local and systemic immune response was studied with hog cholera virus vaccine. Kinetics of antibody synthesis in serum and bucco-pharyngeal secretion was observed. Results show that, whatever the vaccination route (intranasal or intramuscular) a good systemic and local immune response were induced and pigs resisted to a virulent challenge.

Sub-clinical swine fever: a survey of neutralizing antibodies in ther sera of pigs from herds having reproductive failures.

Sera harvested from breeding farms where reproductive failures were observed but where swine fever vaccination was not carried out, where tested for the presence of neutralizing antibodies specific for swine fever virus. Neutralization tests were performed in tissue culture using two viruses strains: the american serological variant "331" strain isolated by MENGELING (1969) and the virulent "normal strain" Alfort. For comparison, sera harvested from healthy, vaccinated and unvaccinated breeding farms were also tested.