Reactivities of 20 anti-human monoclonal antibodies with leucocytes from ten different animal species

Twenty commercially available monoclonal antibodies (mAbs) raised against various human leucocyte surface antigens were tested on lymphocytes, monocytes and granulocytes from horse, pig, cow, sheep, goat, dog, mink, rabbit, rhesus monkey as well as man. Eight antibodies reacted with leucocytes from some of the animals. These were the antibodies against CD2, CD4, CD5, CD8, CD14, CD18, HLA-DR, and the HLA-ABC antigen. The CD18 antibody reacted with lymphocytes, monocytes and granulocytes from all animals tested except goat. The CD14 antibody reacted with monocytes from pig, cow, sheep, goat, dog, mink, rabbit and monkey and with granulocytes from pig and rabbit. The anti-HLA-ABC reacted with leucocytes from monkey and cow. Finally, the CD2, CD4, CD5 and CD8 antibodies reacted with leucocytes from monkey only.

Identification of monoclonal antibodies that cross-react with cytokines from different animal species

Eleven monoclonal antibodies specific for ovine, bovine and human cytokines were investigated by flow cytometry for cross-reactivities with cytokines produced by peripheral blood mononuclear cells (PBMCs) from sheep, cattle, goat, swine, horse, dog, mink, rabbit and human. Four antibodies specific for IL-4, IL-8, IFN-gamma and TNF-alpha cross-reacted with cytokines from a majority of the species investigated. These antibodies can be applied to flow cytometric studies of cytokine production by PBMCs from several veterinary species. Another five antibodies specific for IL-2, IL-6, GM-CSF and IFN-gamma (two antibodies) cross-reacted weakly and with a variable number of animal species. These antibodies could in certain situations be useful in flow cytometry. In a number of cases the immunological cross-reactivities were confirmed by Western blot analyses. Overall, the results of this study will remedy some of the lack of species-specific anti-cytokine antibodies in veterinary research.

Analysis of the immunological cross reactivities of 213 well characterized monoclonal antibodies with specificities against various leucocyte surface antigens of human and 11 animal species

213 Monoclonal antibodies (mAbs) raised against leucocyte surface antigens from human and 11 animal species were analyzed for reactivities against leucocytes from human and 15 different animal species. We found 77 mAbs (36%) to cross-react. Altogether, 217 cross reactions were registered out of 3195 possible combinations (7%). Most of the cross reacting mAbs had integrin or MHC class II specificities. This study defined cross reactions on the following markers: CD1a, 1c, 2, 4, 5, 8, 9, 11a, 11b, 14, 18, 20, 21, 23, 29, 31, 41, 43, 44, 45, 45R, 46, 49, 61, 62L, TCR gamma/delta, BCR, Thy-1, MHC class I and MHC class II, Swine-WC7 and Cattle-WC1. In order to characterize the molecular weight (MW) of the corresponding cross reacting antigens, selected mAbs were used to immunoprecipitate the antigens. The MW's of the analyzed precipitated antigens were in good agreement with the MWs of the homologous antigens. The followed strategy was found to be efficient and economical in defining new leucocyte antigen reactive mAbs.

Three-dimensional structure of Aleutian mink disease parvovirus: implications for disease pathogenicity

The three-dimensional structure of expressed VP2 capsids of Aleutian mink disease parvovirus strain G (ADVG-VP2) has been determined to 22 A resolution by cryo-electron microscopy and image reconstruction techniques. A structure-based sequence alignment of the VP2 capsid protein of canine parvovirus (CPV) provided a means to construct an atomic model of the ADVG-VP2 capsid. The ADVG-VP2 reconstruction reveals a capsid structure with a mean external radius of 128 A and several surface features similar to those found in human parvovirus B19 (B19), CPV, feline panleukopenia virus (FPV), and minute virus of mice (MVM). Dimple-like depressions occur at the icosahedral twofold axes, canyon-like regions encircle the fivefold axes, and spike-like protrusions decorate the threefold axes. These spikes are not present in B19, and they are more prominent in ADV compared to the other parvoviruses owing to the presence of loop insertions which create mounds near the threefold axes. Cylindrical channels along the fivefold axes of CPV, FPV, and MVM, which are surrounded by five symmetry-related beta-ribbons, are closed in ADVG-VP2 and B19. Immunoreactive peptides made from segments of the ADVG-VP2 capsid protein map to residues in the mound structures. In vitro tissue tropism and in vivo pathogenic properties of ADV map to residues at the threefold axes and to the wall of the dimples.

Production and evaluation of glucagon antibodies for radioimmunoassay

Antiglucagon antibodies were raised in rabbits against glucagon covalently linked to bovine serum albumin. We followed three different immunization schemes in order to investigate the role of immunization frequency. The animals were bled regularly and their sera analysed for titre, avidity, and specificity of glucagon antibodies. Immunization frequency could not be correlated to any of the parameters investigated. Antigen dose, however, and persistence of immunization seem to be of importance. After 9 months 22 out of 30 animals immunized yielded antisera with an avidity suitable for radioimmunoassay. Nine of these antisera could be diluted to more than 1:96 000, 8 yielded detection limits below 25 pg/ml, 4 were relatively specific for pancreatic glucagon, and 5 reacted equally well with pancreatic and gut glucagon.

Nucleotide sequence analysis of Aleutian mink disease parvovirus shows that multiple virus types are present in infected mink

Different isolates of Aleutian mink disease parvovirus (ADV) were cloned and nucleotide sequenced. Analysis of individual clones from two in vivo-derived isolates of high virulence indicated that more than one type of ADV DNA were present in each of these isolates. Analysis of several clones from two preparations of a cell culture-adapted isolate of low virulence showed the presence of only one type of ADV DNA. We also describe the nucleotide sequence from map units 44 to 88 of a new type of ADV DNA. The new type of ADV DNA is compared with the previously published ADV sequences, to which it shows 95% homology. These findings indicate that ADV, a single-stranded DNA virus, has a considerable degree of variability and that several virus types can be present simultaneously in an infected animal.

Expression of Aleutian mink disease parvovirus proteins in a baculovirus vector system

We have previously published a detailed transcription map of Aleutian mink disease parvovirus (ADV) and proposed a model for the translation of the two virion structural proteins (VP1 and VP2) and three nonstructural proteins (NS-1, NS-2, and NS-3) (S. Alexandersen, M. E. Bloom, and S. Perryman, J. Virol. 62:3684-3994, 1988). To verify and further characterize this model, we cloned the predicted open reading frames for NS-1, NS-2, NS-3, VP1-VP2, and VP2 alone into a recombinant baculovirus and expressed them in Sf9 insect cells. Expression of VP1-VP2 or VP2 alone in cDNA and in the genomic form was achieved. The expressed proteins had molecular weights similar to those of the corresponding proteins of wild-type ADV-G, although the ratio of VP1 to VP2 was altered. The recombinant baculovirus-expressed ADV VP1 and VP2 showed nuclear localization in Sf9 cells and were able to form particles indistinguishable, by electron microscopy, from wild-type virus. The large nonstructural protein, NS-1, showed predominantly nuclear localization in Sf9 cells when analyzed by immunofluorescence and had a molecular weight similar to that of wild-type ADV NS-1. Moreover, expression of NS-1 in Sf9 cells caused a change in morphology of the cells and resulted in 10-times-lower titers of recombinant baculovirus during infection, suggesting a cytostatic or cytotoxic action of this protein. The smaller NS-2 gene product seems to be located in the cytoplasm. When analyzed by Western immunoblotting, NS-2 comigrated with an approximately 16-kDa band seen in lysates of ADV-infected feline kidney cells. The putative NS-3 gene product exhibited a diffuse distribution in Sf9 cells and had a molecular weight of approximately 10,000. All of the expressed ADV-encoded proteins were recognized by sera from ADV-infected mink. Thus, expression of ADV cDNAs allowed assignment of the different mRNAs to the viral proteins observed during ADV infection in cell culture and supported our previously proposed ADV transcriptional and translational scheme. Moreover, the production of structural proteins from a full-length NS-2 mRNA may add to the repertoire of parvovirus gene expression.

Passive transfer of antiviral antibodies restricts replication of Aleutian mink disease parvovirus in vivo

When mink kits were infected neonatally with a highly virulent strain of Aleutian disease virus (ADV), 100% of both Aleutian and non-Aleutian genotype mink died of interstitial pneumonia characterized by permissive ADV infection of alveolar type II cells. Treatment of infected kits with either mink anti-ADV gamma globulin or mouse monoclonal antibodies against ADV structural proteins reduced mortality by 50 to 75% and drastically reduced the severity of clinical signs. Interestingly, mink kits that survived the acute pulmonary disease all developed the chronic form of immune complex-mediated Aleutian disease. Thus, the antibodies directed against ADV structural proteins were capable of modulating the in vivo pathogenicity from an acute fulminant disease to a chronic immune complex-mediated disorder. The mechanism of this modulation was examined by strand-specific in situ hybridization. We found that the number of ADV-infected type II cells was the same in both untreated and antibody-treated kits. However, in the treated kits, viral replication and transcription were restricted at the cellular level. These data suggested that antibodies prevented acute viral pneumonia by restricting the intracellular level of viral replication and that the relevant antigenic determinants were contained within the viral structural proteins. The restricted levels of viral replication and transcription seen in antibody-treated mink kits resembled the levels observed in infected adult mink and suggested a role of antiviral antibodies in development of persistent infection and chronic immune complex disease.

Overview of the Second International Workshop to define swine cluster of differentiation (CD) antigens

The aim of the Second International Swine Cluster of Differentiation (CD) Workshop, supported by the Veterinary Immunology Committee (VIC) of the International Union of Immunological Societies (IUIS), was to standardize the assignment of monoclonal antibodies (mAb) reactive with porcine leukocyte differentiation antigens and to define new antibody clusters. At the summary meeting of the workshop in July, 1995, revisions in the existing nomenclature for Swine CD were approved, so that the rules are now in accord with those for human and ruminant CD. Swine CD numbers will now be given to clusters of mAb to swine orthologues of human CD molecules when homology is proven by (1) suitable tissue distribution and lymphoid cell subset expression, (2) appropriate molecular mass of the antigen recognized by the mAbs, and (3) reactivity of mAbs with the cloned swine gene products, or cross-reactivity of the mAb on the human gene products. In some cases, this reactivity would not be fully proven, mainly due to the lack of cloned gene products; for these CD antigens, the respective clusters will be assigned by the prefix 'w' which will lead to 'wCD' antigens. As a result of the Second International Swine CD Workshop the assignment of 16 mAb to existing CD groups (CD2a, CD4a, CD5a, wCD6, wCD8, CD14, CD18a, wCD21, wCD25) was confirmed, and 2 mAb to existing swine workshop clusters (SWC). More importantly, for the work on the porcine immune system, was the definition of 5 new swine CD antigens, namely CD3 (recognized by 6 new mAb and 3 epitopes), CD16 (1 new mAb), wCD29 (2 mAb), CD45RA (3 mAb) and CD45RC (1 new mAb). Finally, the demarcation of two new SWC molecules in swine, SWC8 (2 mAb) and SWC9 (2 mAb) was confirmed.

Sequence comparison of the non-structural genes of four different types of Aleutian mink disease parvovirus indicates an unusual degree of variability

The present work shows that at least four different sequence types of Aleutian mink disease parvovirus (ADV) are present in ADV isolates from mink. We here report the nucleotide sequences of these four types of ADV from nucleotide 123 to 2208 (map unit 3 to 46). This part of the genome encodes three non-structural (NS) proteins of ADV. Comparison of the deduced amino acid sequences of these NS proteins showed that the ADV proteins are much less conserved than the NS proteins from other members of the autonomous group of parvoviruses. In general, we found that the middle region of the ADV NS-1 protein was relatively well conserved among the types, while both the amino- and carboxy-terminal ends of the protein had higher amino acid variability. Interestingly, the putative NS-3 protein from type 3 ADV is truncated in the carboxy-terminal end. The molecular evolutionary relationship among the four types of ADV was examined. This analysis, taken together with the unusually high degree of variability of the ADV types, indicates that the ADV infection in mink is likely to be an old infection compared to the other parvovirus infections or, alternatively, that ADV accumulates sequence changes much faster than other parvoviruses.

Acute interstitial pneumonia in mink kits inoculated with defined isolates of Aleutian mink disease parvovirus

The present study addressed the causal role of Aleutian mink disease parvovirus (ADV) in acute interstitial pneumonia in mink kits. All the examined isolates of ADV caused interstitial pneumonia in newborn kits, although the severity of disease and the mortality varied. These findings indicate that ADV is the direct causal agent of this disease in mink kits and that cofactors, which could have been present in the original ADV-K isolate, do not play a role. Acute interstitial pneumonia characterized by hypertrophy and hyperplasia of alveolar type II cells, intranuclear viral inclusions, interstitial edema, and hyaline membrane formation was experimentally reproduced in mink kits infected as newborns with five different isolates of ADV. Four hundred forty-nine newborn mink kits were included in the study, of which 247 were necropsied. The lesions caused by the different isolates were indistinguishable by histopathologic examination, but the incidence (50-100%) and severity (mortality of 30-100%, n = 218) of disease among the mink kits varied. Also, the content of ADV antigens in the lungs of infected kits varied among the groups. According to these features, the examined isolates could be placed in groups of high and low virulence. ADV-K, ADV-Utah I, and ADV-DK were in a highly virulent group producing a mortality of 90-100% (n = 110) in mink inoculated as newborns. ADV-GL and ADV-Pullman belonged to a group of low virulence, with an incidence of clinical disease of 50-70% and a mortality of approximately 30-50% (n = 118) in kits inoculated as newborns. The mortality in the control group receiving a mock inoculum was around 12% (n = 34). The period from infection to development of fatal disease varied from approximately 12 days for the highly virulent isolates up to around 20 days for the isolates of low virulence. The 107 mink kits that survived inoculation with ADV as newborns developed lesions typical of classical Aleutian disease irrespective of the ADV isolate used. The lesions consisted of chronic immune complex-mediated glomerulonephritis and infiltrations with mononuclear cells, including plasma cells in lung, liver, spleen, kidney, mesenteric lymph node, and intestine. Surviving kits also had hypertrophy of the bronchus-associated lymphoid tissue and focal subpleural, intraalveolar accumulations of large cells with foamy cytoplasm, so-called lipid pneumonia.

Reactivity of eleven anti-human leucocyte monoclonal antibodies with lymphocytes from several domestic animals

Nine commercially available monoclonal antibodies and two monoclonal antibodies from The American Type Culture Collection, raised against various human leucocyte surface antigens, were tested on lymphocytes from cow, sheep, goat, swine, horse, cat, dog, mink, and rabbit as well as man. Four antibodies bound to lymphocytes from some of the animals. These were the antibodies against CD8 and CD4 antigen, the antibody to C3b-receptor, and the antibody to the HLA-DR antigen. The CD8 antigen-reactive antibody reacted with lymphocytes from mink, cat, dog, and sheep, while the CD4 antigen-reactive antibody reacted with lymphocytes from mink. The anti-C3b-R antibody reacted with lymphocytes from horse, swine, dog, and cat, and the anti-HLA-DR reacted with lymphocytes from cow, goat, sheep, horse, dog, cat, and mink.

Purification and characterization of the major nonstructural protein (NS-1) of Aleutian mink disease parvovirus

We have previously described the expression of the major nonstructural protein (NS-1) of Aleutian mink disease parvovirus (ADV) in insect cells by using a baculovirus vector (J. Christensen, T. Storgaard, B. Bloch, S. Alexandersen, and B. Aasted, J. Virol. 67:229-238, 1993). To study its biochemical properties, ADV NS-1 was expressed in Sf9 insect cells and purified to apparent homogeneity with a combination of nuclear extraction, Zn2+ ion chromatography, and immunoaffinity chromatography on monoclonal antibodies. The purified protein showed ATP binding and ATPase- and ATP- or dATP-dependent helicase activity requiring either Mg2+ or Mn2+ as a cofactor. The ATPase activity of NS-1 was efficiently stimulated by single-stranded DNA and, to a lesser extent, double-stranded DNA. We also describe the expression, purification, and characterization of a mutant NS-1 protein, in which a lysine in the putative nucleotide binding consensus sequence of the molecule was replaced with serine. The mutated NS-1 was expressed at 10-fold higher levels than wild-type NS-1, but it exhibited no ATP binding. ATPase, or helicase activity. The availability of large amounts of purified functional NS-1 protein will facilitate studies of the biochemistry of ADV replication and gene regulation leading to disease in mink.

Analyses of mAb reactive with porcine CD8

Among all mAb submitted to the first porcine CD workshop, based on FCM analyses six mAb could be identified to recognize the porcine CD8 analogue (workshop Nos. 004, 051, 052, 053, 108 and 109). In immunoprecipitation studies three mAb (Nos. 004, 108 and 109) recognized an antigen with an apparent molecular mass of about 35 kDa under reducing conditions and about 70 kDa under non-reducing conditions. The molecular masses of the antigens recognized by the three other mAb (Nos. 051, 052 and 053) are still unknown. Epitope analyses performed by blocking experiments led to the determination of two CD8 epitopes: CD8a and CD8b. CD8a is recognized by mAb Nos. 004, 051 and 052, and CD8b by Nos. 053, 108 and 109.

Vaccination with Aleutian mink disease parvovirus (AMDV) capsid proteins enhances disease, while vaccination with the major non-structural AMDV protein causes partial protection from disease

Vaccination studies were performed with partially purified recombinant AMDV VP1/2 capsids as well as with the major AMDV non-structural protein (NS1). All vaccine constructs induced an antibody response, but did not prevent infection upon challenge with AMDV. The severity of Aleutian disease (AD) was judged by the serum gammaglobulin level, the quantity of peripheral blood CD8 lymphocytes, antibody titers to VP1/2 and NS1 proteins and mink death rates. The VP1/2 vaccine constructs enhanced the disease process with drastic death rates for the vaccinated mink. On the contrary, the NS1 vaccine constructs resulted in milder AD than seen in the non-vaccinated mink.

Summary of workshop findings for antibodies reacting with porcine T-cells and activation antigens: results from the Second International Swine CD Workshop

After initial evaluation of the 176 new and 19 control monoclonal antibodies (mAb) submitted to the Second International Swine CD Workshop, 57 were assigned to the T-cell/activation marker subgroup. These 57 mAb were further analyzed using flow cytometry on whole blood lymphocytes, splenocytes, Peyer's patch lymphocytes, in vitro cell lines, broncho-alveolar lavage cells, Con A and PHA blasts, fetal cell populations, and by 2-color flow cytometry against mAb to porcine CD2, CD4, and CD8. Finally, the molecular weights of the target antigens were characterized when possible. As a result of these analyses, 23 mAb were distributed into 7 CD clusters. Newly confirmed mAb assignments included: two CD2; one CD4; two CD5; one wCD6; and one wCD25. Three new mAb were found that reacted with wCD8, one of which defined a new epitope, wCD8c. For the first time, mAb against porcine CD3 were identified, including 6 mAb that reacted with three different epitopes. Several new mAb reacted with antigens whose expression varied depending on the activation state of the test cell. These will require further characterization in order to assign a CD number.

Dietary gluten reduces the number of intestinal regulatory T cells in mice

It is well established that gluten-free diet reduces the incidence of type 1 diabetes mellitus (T1D) in non-obese diabetic (NOD) mice, though the mechanism is not known. However, regulatory T cells (Treg) are likely to play an important role. Also, it is known that dietary gluten induces an intestinal increase in the bacterium Lactococcus garvieae, but the importance of this phenomenon for T1D development is doubtful. Our hypothesis is that gluten is responsible for mediating its effect on T1D through the influence on Treg development independent of gluten-induced Lactococci. Four groups of female NOD and BALB/c mice of 3 week old were fed either a gluten-free diet or a standard diet. Lactococcus garvieae or saline water was administered per oral to one of each dietary group. Spleen and Peyer's patches were sampled from BALB/c mice for flow cytometric monitoring of IL-10 and Treg. NOD mice were diagnosed diabetic with blood glucose level >12 mmol/l. Dietary gluten significantly decreased the occurrence of Tregs by 10-15% (P < 0.05) in mice compared with those fed a standard diet. These results and the diabetes incidence were independent of the gluten-induced bacterial factor Lactococci. The prevalence of Treg was 5- to 10-fold more abundant in the Peyer's patches than in the spleen (P < 0.001). In conclusion, dietary gluten has a significant negative quantitative impact on the generation of Treg in mice, independent of gluten-induced Lactococcus garvieae, and Treg are far more abundant in Peyer's patches than in the spleen.

Report on the analyses of mAb reactive with porcine CD8 for the second international swine CD workshop

Based on an analysis of their reactivity with porcine peripheral blood lymphocytes (PBL), only three of the 57 mAbs assigned to the T cell/activation marker group were grouped into cluster T9 along with the two wCD8 workshop standard mAbs 76-2-11 (CD8a) and 11/295/33 (CD8b). Their placement was verified through the use of two-color cytofluorometry which established that all three mAbs (STH101, #090; UCP1H12-2, #139; and PG164A, #051) bind exclusively to CD8+ cells. Moreover, like the CD8 standard mAbs, these three mAbs reacted with two proteins with a MW of 33 and 35 kDa from lymphocyte lysates and were, thus, given the wCD8 designation. Because the mAb STH101 inhibited the binding of mAb 76-2-11 but not of 11/295/33, it was given the wCD8a designation. The reactivity of the other two new mAbs in the T9 cluster with the various subsets of CD8+ lymphocytes were distinct from that of the other members in this cluster including the standards. Although the characteristic porcine CD8 staining pattern consisting of CD8low and CD8high cells was obtained with the mAb UCP1H12-2, a wider gap between the fluorescence intensity of the CD8low and CD8high lymphocytes was observed. In contrast, the mAb PG164A, not only exclusively reacted with CD4-/CD8high lymphocytes, but it also failed to recognize CD4/CD8 double positive lymphocytes. It was concluded that this mAb is specific for a previously unrecognized CD8 epitope, and was, thus, given the wCD8c designation. A very similar reactivity pattern to that of PG164A was observed for two other mAbs (STH106, #094; and SwNL554.1, #009). Although these two mAbs were not originally positioned in the T cell subgroup because of their reactivity and their ability to inhibit the binding of PG164A, they were given the wCD8c designation. Overall, five new wCD8 mAbs were identified. Although the molecular basis for the differences in PBL recognition by these mAbs is not yet understood, they will be important in defining the role of CD8+ lymphocyte subsets in health and disease.

Comparison of promoter activity in Aleutian mink disease parvovirus, minute virus of mice, and canine parvovirus: possible role of weak promoters in the pathogenesis of Aleutian mink disease parvovirus infection

Aleutian mink disease parvovirus (ADV) infection causes both acute and chronic disease in mink, and we have previously shown that it is the level of viral gene expression that determines the disease pattern. To study the gene regulation of ADV, we have cloned the P3 ADV and P36 ADV promoters in front of a reporter gene, the chloramphenicol acetyltransferase (CAT) gene, and analyzed these constructs by transient transfection in a feline kidney cell line and mouse NIH 3T3 cells. The genes for ADV structural proteins (VP1 and VP2) and the nonstructural proteins (NS-1, NS-2, and NS-3) were cloned into a eukaryotic expression vector, and their functions in regulation of the P3 ADV and P36 ADV promoters were examined in cotransfection experiments. The ADV NS-1 protein was able to transactivate the P36 ADV promoter and, to a lesser degree, the P3 ADV promoter. Constitutive activities of the P3 ADV and P36 ADV promoters were weaker than those of the corresponding promoters from the prototypic parvovirus minute virus of mice (MVM) and canine parvovirus (CPV). Also, the level of transactivation of the P36 ADV promoter was much lower than those of the corresponding P38 MVM and P38 CPV promoters transactivated with MVM NS-1. Moreover, the ADV NS-1 gene product could transactivate the P38 MVM promoter to higher levels than it could transactivate the P36 ADV promoter, while the P36 ADV promoter could be transactivated by MVM NS-1 and ADV NS-1 to similar levels. Taken together, these data indicated that cis-acting sequences in the P36 ADV promoter play a major role in determining the low level of transactivation observed. The P3 ADV and P4 MVM promoters could be transactivated to some degree by their respective NS-1 gene products. However, in contrast to the situation for the late promoters, switching NS-1 proteins between the two viruses was not possible. This finding may indicate a different mechanism of transactivation of the early promoters (P3 ADV and P4 MVM) compared with the late (P36 ADV and P38 MVM) promoters. In summary, the constitutive levels of expression from the ADV promoters are weaker than the levels from the corresponding promoters of MVM and CPV. Moreover, the level of NS-1-mediated transactivation of the late ADV promoter is impaired compared with the level of transactivation of the late promoters of MVM and CPV.(ABSTRACT TRUNCATED AT 400 WORDS)

In utero infection with porcine reproductive and respiratory syndrome virus modulates leukocyte subpopulations in peripheral blood and bronchoalveolar fluid of surviving piglets

It is well known that piglets congenitally infected with porcine reproductive and respiratory syndrome virus (PRRSV) can be viremic at birth, and that preweaning mortality due to secondary infections often increases during acute outbreaks of PRRS. Therefore, an immunosuppressive effect of in utero infection has been suggested. The aim of the present study was to characterise the changes of leukocyte populations in piglets surviving in utero infection with PRRSV. A total of 27 liveborn uninfected control piglets and 22 piglets infected transplacentally with a Danish strain of PRRSV were included. At 2 and 4 weeks of age, 21 of 22 (96%) and 7 of 14 (50%) examined infected piglets were still viremic, whereas PRRSV could not be detected in the six infected piglets examined at 6 weeks of age. Flow cytometry analysis was used to determine the phenotypic composition of leukocytes in peripheral blood and bronchoalveolar lavage fluid (BALF) of 2-, 4- and 6-week-old infected piglets and age-matched uninfected controls. The key observation in the present study is that high levels of CD8(+) cells constitute a dominant feature in peripheral blood and BALF of piglets surviving in utero infection with PRRSV. In BALF, the average high level of CD8(+) cells in 2-week-old infected piglets (33.4 +/- 12.6%) was followed by a decline to 7.3 +/- 3.0 and 11.1 +/- 3.0% at 4 and 6 weeks of age. BALF of control piglets contained 1.6 +/- 0.9, 2.3 +/- 1.8 and 1.9 +/- 0.5% CD8(+) cells, only. In peripheral blood, however, the average number of CD8(+) cells remained at high levels in the infected piglets throughout the post-natal experimental period (2.8 +/- 1.9, 2.9 +/- 1.8 and 3.2 +/- 1.7 x 10(6) CD8(+) cells/ml at 2, 4 and 6 weeks, respectively). In the controls, the average levels of CD8(+) cells were 0.9+/-0.2, 1.9 +/- 1.7 and 1.6 +/- 0.5 x 10(6)/ml, respectively. Furthermore, the numbers of CD2(+) , CD4(+)CD8(+) and SLA-classII(+) cells, respectively, in peripheral blood, together with the levels of CD2(+) and CD3(+) cells in BALF were increased in the infected piglets infected in utero compared to the uninfected controls. The kinetic analyses carried out in the present study reflect that in utero infection with PRRSV modulates immune cell populations in peripheral blood and BALF of surviving piglets. The observed changes are characterised by high levels of CD8(+) cells supporting an important role of these cells in PRRSV infection. The present results, however, do not support the existence of post-natal immunosuppression following in utero infection with PRRSV.

Infection with human H1N1 influenza virus affects the expression of sialic acids of metaplastic mucous cells in the ferret airways

Glycans terminating in sialic acids serve as receptors for influenza viruses. In this study ferrets were infected with influenza virus A/New Caledonia/20/99, and the in situ localization of sialic acids linked alpha2-3 and alpha2-6 in the airways was investigated in infected and non-infected animals by use of sialic acid detecting lectins and a monoclonal antibody towards the Sialyl-Tn antigen. The goblet cells in the bronchi from non-infected ferrets expressed Sialyl alpha 2-6Gal glycans, while the seromucinous glands in the submucosa expressed Sialyl alpha 2-3Gal glycans. In the infected animals, the surface epithelial cells in some bronchi showed metaplasia and expressed the Sialyl-Tn antigen: Sialyl alpha 2-6GalNAc-O-Thr/Ser. The submucosal tracheal glands in these animals showed increased expression of both Sialyl alpha 2-3 and Sialyl alpha 2-6 epitopes.

Production of mink enteritis parvovirus empty capsids by expression in a baculovirus vector system: a recombinant vaccine for mink enteritis parvovirus in mink

The VP-2 gene of mink enteritis parvovirus (MEV) was amplified by the polymerase chain reaction using MEV DNA isolated from the faeces of a naturally infected mink. Subsequently the VP-2 gene was cloned into a baculovirus expression vector. Recombinant baculoviruses were isolated and the MEV VP-2 gene product was characterized after expression in Sf9 insect cells. The MEV VP-2 product had the same size as that reported for the wild-type MEV VP-2 protein and was recognized by convalescent sera from MEV-infected mink and a panel of monoclonal antibodies reactive to MEV. Furthermore, the VP-2 protein was able to form parvovirus-like particles, which had haemagglutinating properties comparable with the wild-type MEV. The cloned VP-2 gene was sequenced and only five nucleotide differences were found after alignment with the known sequences of the MEV type 1 and type 2 isolates. Surprisingly, the VP-2 gene encoded a valine and a tyrosine at amino acid positions 232 and 234, identical to the situation found in MEV type 1, but at position 300 there was a valine which is a determinant of MEV type 2. Immunization of mink with approximately 40,000 haemagglutinating units of recombinant MEV VP-2 induced a measurable antibody response as tested by haemagglutination inhibition. Furthermore, the immunized mink did not excrete virus and did not develop clinical disease upon challenge with a virulent isolate of MEV.

Aleutian disease virus, a parvovirus, is proteolytically degraded during in vivo infection in mink

The polypeptides of the highly virulent mink-passaged Utah I and the nonvirulent cell culture-adapted ADV-G strain of Aleutian disease virus (ADV) were compared. When CRFK cells infected with either Utah I or ADV-G were analyzed by immunoprecipitation, both viruses induced proteins with molecular weights characteristic of the ADV-G 85,000 ( 85k )- and 75k-dalton structural proteins (p85 and p75) as well as the 71k -dalton nonvirion protein p71 . However, when Utah I, Pullman ADV, and DK ADV (a Danish isolate of ADV) were purified from infected mink, only polypeptides with molecular weights between 27k and 30k could be identified. In addition, trypsin treatment of ADV-G degraded p85 and p75 to smaller antigenic proteins with molecular weights of 24k and 27k, similar to those found for the virulent in vivo viruses. The effect of proteolytic treatment of ADV was then studied in detail. Purification of Utah I ADV from mink organs in the presence of protease inhibitor did not prevent the appearance of the low-molecular-weight proteins and ADV-G proteins were not degraded upon purification from a homogenate of normal mink organs, suggesting that artifactual proteolysis was not occurring. When a serum pool from terminally diseased mink was analyzed by radioimmunoassay for antibody reactivity against trypsinized and nontrypsinized ADV-G, five times higher reactivity was found for the trypsinized ADV-G than for the nontrypsinized ADV-G, an effect which could not be elicited by chymotrypsin or V8 protease treatment, implying that in vivo-produced ADV was being modulated in vivo by trypsin or a trypsin-like enzyme. Trypsinization was shown not to cause a change in ADV virion density, but to decrease the in vitro infectivity of ADV-G for CRFK cells. These studies suggested that during infection of mink ADV proteins are degraded to highly antigenic smaller polypeptides.