Differential expression of sialic acid on porcine organs during the maturation process

Assessment of the hemagglutinating activity of the Porcine orthorubulavirus

Blue eye disease (BED) in pigs is caused by Porcine orthorubulavirus (PRV) of the Paramyxoviridae family. It is an endemic disease in swine production in the central region of Mexico and causes nervous signs and high mortality in suckling pigs, pneumonia in growing pigs, orchitis in boars and mummification during gestation. PRV hemagglutinates most red blood cells (RBCs) of domestic species. For serological diagnosis, the hemagglutination inhibition test is used, and in this test, guinea pig, bovine and chicken RBCs have been commonly used. In this investigation, hemagglutination with PRV was evaluated using the RBCs of seven domestic species (chicken, bovine, horse, pig, dog, guinea pig and rabbit). In the hemagglutination test, the following parameters were evaluated: temperature (25 °C and 37 °C), bottoms of the wells (V and U), erythrocyte concentration (0.5%, 0.75%, and 1%), and reading time (15, 30, 45, 60 and 90 min). Significant differences (P < 0.001) were found in most of the evaluated treatments. The best hemagglutination results were obtained with chicken, bovine and horse RBCs. The hemagglutination titer is higher (2 dilutions) when using chicken RBCs than when using bovine or horse RBCs. If chicken RBCs are used in the inhibition of hemagglutination, the test will be more sensitive, while it is more specific when bovine or horse RBCs are used. The hemagglutination readings are imprecise when using RBCs from dogs, pigs, guinea pigs and rabbits. RBCs from these species should not be used for the diagnosis or investigation of PRV.

Continuous Reassortment of Clade 2.3.4.4 H5N6 Highly Pathogenetic Avian Influenza Viruses Demonstrating High Risk to Public Health

Since it firstly emerged in China in 2013, clade 2.3.4.4 H5N6 highly pathogenic avian influenza viruses (HPAIVs) has rapidly replaced predominant H5N1 to become the dominant H5 subtype in China, especially in ducks. Not only endemic in China, it also crossed the geographical barrier and emerged in South Korea, Japan, and Europe. Here, we analyzed the genetic properties of the clade 2.3.4.4 H5N6 HPAIVs with full genome sequences available online together with our own isolates. Phylogenetic analysis showed that clade 2.3.4.4 H5N6 HPAIVs continuously reassorted with local H5, H6, and H7N9/H9N2. Species analysis reveals that aquatic poultry and migratory birds became the dominant hosts of H5N6. Adaption to aquatic poultry might help clade 2.3.4.4 H5N6 better adapt to migratory birds, thus enabling it to become endemic in China. Besides, migratory birds might help clade 2.3.4.4 H5N6 transmit all over the world. Clade 2.3.4.4 H5N6 HPAIVs also showed a preference for α2,6-SA receptors when compared to other avian origin influenza viruses. Experiments in vitro and in vivo revealed that clade 2.3.4.4 H5N6 HPAIVs exhibited high replication efficiency in both avian and mammal cells, and it also showed high pathogenicity in both mice and chickens, demonstrating high risk to public health. Considering all the factors together, adaption to aquatic poultry and migratory birds helps clade 2.3.4.4 H5N6 overcome the geographical isolation, and it has potential to be the next influenza pandemic in the world, making it worthy of our attention.

Neuraminidase activity of blue eye disease porcine rubulavirus: Specificity, affinity and inhibition studies

Porcine rubulavirus (PorPV), also known as La Piedad Michoacan Virus (LPMV) causes encephalitis and reproductive failure in newborn and adult pigs, respectively. The hemagglutinin-neuraminidase (HN) glycoprotein is the most exposed and antigenic of the virus proteins. HN plays central roles in PorPV infection; i.e., it recognizes sialic acid-containing cell receptors that mediate virus attachment and penetration; in addition, its neuraminidase (sialic acid releasing) activity has been proposed as a virulence factor. This work describes the purification and characterization of PorPV HN protein (isolate PAC1). The specificity of neuraminidase is restricted to sialyl(α2,3)lactose (3SL). HN showed typical Michaelis-Menten kinetics with fetuin as substrate (km=0.029μM, Vmax=522.8nmolmin^-1mg^-1). When 3SL was used as substrate, typical cooperative kinetics were found (S₅₀=0.15μM, Vmax=154.3nmolmin^-1mg^-1). The influenza inhibitor zanamivir inhibited the PorPV neuraminidase with IC₅₀ of 0.24μM. PorPV neuraminidase was activated by Ca²⁺ and inhibited by nucleoside triphosphates with the level of inhibition depending on phosphorylation level. The present results open possibilities to study the role of neuraminidase in the pathogenicity of PorPV infection and its potential inhibitors.

Acute neurologic disease in Porcine rubulavirus experimentally infected piglets

The objective of this study was to evaluate the clinical disease, humoral response and viral distribution of recent Porcine rubulavirus (PorPV) isolates in experimentally infected pigs. Four, 6-piglet (5-days old) groups were employed (G1-84, G2-93, G3-147, and G4-T). Three viral strains were used for the experimental infection: the reference strain LPMV-1984 (Michoacán 1984) and two other strains isolated in 2013, one in Queretaro (Qro/93/2013) and the other in Michoacán (Mich/147/2013). Each strain was genetically characterized by amplification and sequencing of the gene encoding hemagglutinin-neuroamidase (HN). The inoculation was performed through the oronasal and ocular routes, at a dose of 1×10⁶TCID₅₀/ml. Subsequently, the signs were evaluated daily and necropsies were performed on 3 different days post infection (dpi). We recorded all micro- and macroscopic lesions. Organs from the nervous, lymphatic, and respiratory system were analyzed by quantifying the viral RNA load and the presence of the infectious virus. The presence of the viral antigen in organs was evidenced through immunohistochemistry. Seroconversion was evaluated through the use of a hemagglutination inhibition test. In the characterization of gene HN, only three substitutions were identified in strain Mich/147/2013, two in strain LPMV/1984 (fourth passage) and one in strain Qro/93/2013, with respect to reference strain LPMV-84, these changes had not been identified as virulence factors in previously reported strains. Neurological alterations associated with the infection were found in all three experimental groups starting from 3dpi. Groups G1-84 and G3-147 presented the most exacerbated nervous signs. Group G2-93 only presented milder signs including slight motor incoordination, and an increased rectal temperature starting from day 5 post infection (PI). The main histopathological findings were the presence of a mononuclear inflammatory infiltrate (lymphocytic/monocytic) surrounding the ventricles in the brain and focal interstitial pneumonitis with distention of the alveolar sacs in the lungs. PorPV and RNA distribution were identified in the organs of the nervous, lymphatic, and respiratory systems of the piglets analyzed at different times (days 5, 10, and 15 PI). The viral antigen was detected in the brain and lungs in most of the assessed groups. Seroconversion was evident in groups G1-84 and G2-93. Groups G1-84 and G3-147 were the most clinically affected by the experimental infection. Both strains were isolated in the state of Michoacán. The virulence of the new isolates maintains similar characteristics to those reported more than 30 years ago.

Molecular characterization of the level of sialic acids N-acetylneuraminic acid, N-glycolylneuraminic acid, and ketodeoxynonulosonic acid in porcine milk during lactation

Sialic acids (Sia) are key monosaccharide constituents of sialylated glycoproteins (Sia-GP), human sialylated milk oligosaccharide (Sia-MOS), and gangliosides. Human milk sialylated glycoconjugates (Sia-GC) are bioactive compounds known to act as prebiotics and promote neurodevelopment, immune function, and gut maturation in newborns. Only limited data are available on the Sia content of porcine milk. The objective of this study was to quantitatively determine the total level of Sia N-acetylneuraminic acid (Neu5Ac), N-glycolylneuraminic acid (Neu5Gc), and ketodeoxynonulosonic acid (KDN) in porcine milk and to compare these levels in gilt and sow milk during lactation. Milk from 8 gilts and 22 sows was collected at 3 stages of lactation (colostrum, transition, and mature milk). Standard and experimental samples were derivatized using 1,2-diamino-4,5-methylenedioxy-benzene and analyzed by ultra-high-performance liquid chromatography using a fluorescence detector. The following new findings are reported: (1) Gilt and sow milk contained significant levels of total Sia, with the highest concentration in colostrum (1,238.5 mg/L), followed by transition milk (778.3 mg/L) and mature milk (347.2 mg/L); (2) during lactation, the majority of Sia was conjugated to Sia-GP (41-46%), followed by Sia-MOS (31-42%) and a smaller proportion in gangliosides (12-28%); (3) Neu5Ac was the major form of Sia (93-96%), followed by Neu5Gc (3-6%) and then KDN (1-2%), irrespective of milk fraction or stage of lactation; (4) the concentration of Sia in Sia-GP and Sia-MOS showed a significant decline during lactation, but the level of ganglioside Sia remained relatively constant; (5) mature gilt milk contained a significantly higher concentration of Sia-GP than sow milk. The high concentration of total Sia in porcine milk suggests that Sia-GC are important nutrients that contribute to the optimization of neurodevelopment, immune function, and growth and development in piglets. These findings provide an important rationale for the inclusion of Sia-GC in pig milk replacers to mimic porcine milk composition for the optimal growth and development of piglets.

Molecular and epidemiological studies of Porcine rubulavirus infection - an overview

Porcine rubulavirus-La Piedad-Michoacan-Mexico virus (PorPV-LPMV) was identified as the causative agent of a viral disease that emerged spontaneously in Mexican swine in the 1980s. Since the report of the initial outbreak of the disease, only one full-length genome from a strain isolated in 1984 (PorPV-LPMV/1984) has been sequenced; sequence data are scarce from other isolates. The genetic variation of this virus that has spread throughout the main endemic region of Mexico is almost a complete mystery. The development of molecular techniques for improved diagnostics and to investigate the persistence, molecular epidemiology, and the possible reservoirs of PorPV are needed. Together, this will provide greater knowledge regarding the molecular genetic changes and useful data to establish new strategies in the control of this virus in Mexico.

Respiratory disease in growing pigs after Porcine rubulavirus experimental infection

The aim of this study was to analyze the pathogenicity and distribution of Porcine rubulavirus (PorPV) in the respiratory tract of experimentally infected pigs. Nine 6-week-old pigs were infected with PorPV and examined clinically. Blood, nasal swab, and tissue samples were collected on different days post-infection (DPI). The humoral immune responses and viral loads were evaluated. The infected pigs exhibited an increase in the respiratory clinical signs. In addition, the excretion of PorPV was extended to 23 DPI in the nasal fluid. The distribution of PorPV in the respiratory tract tissues was extended until the end of the experiment; soft palate tonsil and lymph nodes exhibited high viral loads. The major microscopic lesions observed in the lungs corresponded to interstitial pneumonia and hyperplasia of the associated lymphoid tissue. In conclusion, PorPV infection causes a pneumonic disease characterized by a prolonged virus excretion and high viral load in the lymphoid tissues.

Functions and Biosynthesis of O-Acetylated Sialic Acids

Sialic acids have a pivotal functional impact in many biological interactions such as virus attachment, cellular adhesion, regulation of proliferation, and apoptosis. A common modification of sialic acids is O-acetylation. O-Acetylated sialic acids occur in bacteria and parasites and are also receptor determinants for a number of viruses. Moreover, they have important functions in embryogenesis, development, and immunological processes. O-Acetylated sialic acids represent cancer markers, as shown for acute lymphoblastic leukemia, and they are known to play significant roles in the regulation of ganglioside-mediated apoptosis. Expression of O-acetylated sialoglycans is regulated by sialic acid-specific O-acetyltransferases and O-acetylesterases. Recent developments in the identification of the enigmatic sialic acid-specific O-acetyltransferase are discussed.

Terminal monosaccharide expression on amniotic glycoproteins as biomarkers of fetus maturity

Glycotypes, particularly those that terminate with sialic acid and fucose are known to play a fundamental role in human development, during implantation, growth and differentiation of fetal tissues. The present review describes changes in the exposition of terminal sialic acid and fucose isoforms in the amniotic fluid glycoconjugates, α1-acid glycoprotein and fibronectin during critical stages of pregnancy, i.e. second and third trimester, perinatal period, delivery and post-date pregnancy. The distinct amniotic glycoforms are suggested to be implicated in regulatory processes to ensure homoeostasis during pregnancy and to protect the fetus. These may have the potential of becoming additional laboratory makers in obstetrics to monitor pregnancy.

Increased expression of sialic acid in cervical biopsies with squamous intraepithelial lesions

Background

Altered sialylation has been observed during oncogenic transformation. Sialylated oligosaccharides of glycoproteins and glycolipids have been implicated in tumor progression and metastases. In the cervical cancer high levels of sialic acid have been reported in the patients serum, and an increased of total sialic acid concentration has been reported for the cervical neoplasia and cervical cancer. This study investigates the changes in expression and distribution of α2,3-linked sialic acid and α2,6- linked sialic acid in low and high squamous intraepithelial lesions and in normal tissue.

Methods

Lectin histochemistry was used to examine the expression and distribution of sialic acid in different grades of cervical neoplasia. We applied Maackia amurensis lectin, which interacts with α2,3-linked sialic acid and Sambucus nigra lectin specific for α2,6-linked sialic acid.

Results

The histochemical analysis showed that α2,3-linked sialic acid and α2,6- linked sialic acid increased in intensity and distribution in concordance with the grade of squamous intraepithelial lesion (SIL). These results are in concordance with a previous study that reports increased RNAm levels of three sialyltransferases.

Conclusions

These results show that the change in sialylation occurs before cancer development and may play an important role in cellular transformation. These findings provide the basis for more detailed studies of the possible role of cell surface glycoconjugates bearing sialic acid in the cellular cervix transformation.

The second bovine beta-galactoside-alpha2,6-sialyltransferase (ST6Gal II): genomic organization and stimulation of its in vitro expression by IL-6 in bovine mammary epithelial cells

We have cloned a cDNA sequence encoding the second bovine beta-galactoside-alpha2,6-sialyltransferase whose sequence shares more than 75% of identity with hST6Gal II cDNA coding sequence. The bovine gene, located on BTA 11, spans over 50 kbp with five exons (E1-E5) containing the 1488 bp open reading frame and a 5'-untranslated exon (E0). The gene expression pattern reveals a specific tissue distribution (brain, lungs, spleen, salivary, and mammary glands) compared to ST6Gal I which is ubiquitously expressed. We identified for bovine ST6Gal II three kinds of transcripts which differ by their 5'-untranslated regions. Among them, two transcripts are brain specific whereas the third one is found in all of the tissues expressing the gene. Two pFlag-bST6Gal II vector constructions were separately transfected in COS-1 cells in order to express either membrane-bound or soluble active forms of ST6Gal II. Enzymatic assays with these two forms indicated that the enzyme used the LacdiNAc structure (GalNAcbeta1,4GlcNAc) as a better acceptor substrate than the Type II (Galbeta1-4GlcNAc) disaccharide. Moreover, the enzyme's efficiency is improved when the acceptor substrate is provided as a free oligosaccharide rather than as a protein-bound oligosaccharide. In order to investigate the potential role of ST6Gal II during the acute phase of inflammation, we used primary cultures of bovine mammary epithelial cells which were stimulated with pro-inflammatory cytokines. It appears that the ST6Gal II gene was upregulated in cells stimulated by IL-6. This result suggested that alpha2,6-sialylation mediated by this gene could contribute to organism's response to infections.

Investigation of T-cell responses and viral mRNA persistence in lymph nodes of pigs infected with porcine rubulavirus

Selected lymphocyte subpopulations were studied and the distribution of viral mRNA were investigated during acute and persistent porcine rubulavirus (PoRV-LPMV) infection in Vietnamese pot-bellied pigs. Six pigs infected with PoRV-LPMV at 17 days of age exhibited clinical signs 7-10 days post-inoculation (pi). One infected piglet died 11 days pi while the other five recovered around day 13 pi and survived until euthanasia on day 277 pi. Increased numbers of CD8+, CD4+ and CD2+ T cells were detected during the acute phase of infection while CD8+ cells were elevated throughout the infection, including during the persistent stage. Specific antibodies against the haemagglutinin-neuraminidase protein of PoRV-LPMV were detected during persistent infection. Although infectious virus could not be recovered from tissues from any of the infected pigs at necropsy 277 days pi, PoRV-LPMV mRNA was detected in lymph nodes, pancreas and central nervous system using a nested polymerase chain reaction technique. Continued lymphocyte interaction with viral RNA may be an important factor in promoting cellular and humoral responses during persistent PoRV-LPMV infection.

Potential use of the Macrobrachium rosenbergii lectin for diagnosis of T-cell acute lymphoblastic leukemia

T-cell acute lymphoblastic leukemia is the most common form of cancer in children. Lectins are proteins or glycoproteins from plants or animals that recognize oligossacharides on the cell surface and have been used to characterize the structural changes of oligosaccharides in leukemias. In this study, we used the lectin from the freshwater prawn Macrobrachium (M. rosenbergii), specific for acetyl groups in sialylated glycans, because increased sialylation of glycoproteins and glycolipids has been identified in lymphoblastic leukemias. We compared the specificity of the M. rosenbergii lectin for lymphoblastic leukemias with the specificities of the lectins from Triticum vulgaris, Solanum tuberosum, Arachis hipogaea, and Phytolacca americana. By morphologic and phenotype characterization with a panel of monoclonal antibodies, we identified four types of leukemias from 106 leukemia patients: 11 cases of T-cell acute lymphoblastic leukemia, 61 cases of B-cell acute lymphoblastic leukemia, 24 cases of acute myeloblastic leukemia, and 10 cases of acute biphenotypic leukemia. As determined by cytofluorometric assays, nine of the eleven cases with T-cell acute lymphoblastic leukemia (8 +/- 3 years old) were specifically identified with the lectin from M. rosenbergii. In contrast, only six cases of B-cell leukemia, one case of myeloblastic leukemia, and 2 cases of biphenotypic leukemia were identified with this M. rosenbergii lectin. The other lectins tested showed no capacity to differentiate, in a significant manner, any of the four types of leukemias tested. Thus, the lectin from M. rosenbergii could be considered a useful tool for the diagnosis and study of T-cell acute lymphoblastic leukemia.

Molecular characterization of the hemagglutinin-neuraminidase gene of porcine rubulavirus isolates associated with neurological disorders in fattening and adult pigs

"Blue eye disease" is a viral infection of swine endemic in Mexico, which produces fatal encephalitis accompanied by respiratory signs and corneal opacity in suckling piglets. An atypical blue eye disease outbreak presented high rates of neurological signs in fattening and adult pigs from 2000 to 2003. In order to identify the basis of increased neurovirulence, the hemagglutinin-neuraminidase (HN) gene of several porcine rubulavirus isolates were sequenced and compared with that of La Piedad Michoacan virus and other isolates that did not produce neurological disorders in weaned pigs. Nine amino acid mutations distinguished the high neurovirulent PAC6-PAC9 viruses, whereas five mutations characterized the low neurovirulent PAC2 and PAC3 viruses. HN protein three-dimensional models showed that the main conformation and functional domains were preserved, although substitutions A223T and A291D occurred in PAC2 and PAC3 viruses, as well as A511K and E514K presented in PAC6-PAC9 viruses considerably modified the properties of the HN protein surface. The increased positive charge of the HN protein of PAC6-PAC9 viruses seems to be associated with their increased neurovirulence.

Relative amounts of sialic acid and fucose of amniotic fluid glycoconjugates in relation to pregnancy age

The present knowledge concerning the glycan structures and role of glycoconjugates derived from amniotic fluid is fragmentary and mainly focuses on the individual glycoproteins. The question has arisen as whether the general glycosylation pattern of amniotic fluid glycoconjugates can change with the progression of a normal pregnancy. In the present work we have described the dynamic, quantitative alterations in relative amounts of sialic acid and fucose linked by a variety of anomeric linkages to subterminal oligosaccharide structures of amniotic fluid glycoconjugates in relation to pregnancy age. The analysis was performed in the following groups of amniotic fluids derived from normal pregnancy by lectin dotting method: "2nd trimester" (14-19 weeks), "3rd trimester" (29-37 weeks), "perinatal period" (38-40 weeks) , "delivery at term" (39-41 weeks) and "post date pregnancy" (41-43 weeks). In the "3rd trimester" the amniotic fluid glycoconjugates contained higher relative amounts of glycans terminated by alpha2-6-linked sialic acid (p < 0.00002) and by alpha1-6 innermost fucose (p < 0.000001) than those in the 2nd trimester. In contrast, they showed the lower relative amount of fucose linked alpha1-3 (p < 0.02). At the perinatal period the relative amount of alpha2-6-linked sialic acid increased (p < 0.03), and it then decreased during delivery (p < 0.02) to the level found in the "3rd trimester" group. In the post date pregnancy all parameters studied increased. The sialyl- and fucosyl-glycotopes of the amniotic fluid glycoconjugates may play an critical role in growth and tissue remodeling of the foetus, as well as may might reflect maturation of a foetus. Additionally, a determination of the glycotope expressions might be helpful in prenatal diagnosis as predictor factors for well being of mother and child.

Purification of the Porcine rubulavirus attachment protein by liquid isoelectric focusing

Porcine rubulavirus (PoRV) is an emerging virus responsible for meningoencephalitis, respiratory distress, and reproductive alterations in pigs. The hemagglutinin-neuraminidase (HN) glycoprotein is the most exposed and antigenic of the virus proteins. HN plays central roles in PoRV infection; i.e., it recognizes sialic acid-containing cell receptors that mediate virus attachment and penetration; in addition, its neuraminidase (sialic acid hydrolysis) activity has been proposed to be a virulence factor. So, HN is an ideal target for therapeutic treatment and prevention of this viral infection. This work describes a simple, fast, and sensitive method to purify the active form of HN protein based on its isoelectric point. HN was purified at a pH of 4.4, at which a single protein band of 66 kDa was observed on SDS-PAGE. Pure HN showed a maximal enzymatic activity at pH 3.5 and 37 degrees C using bovine fetuin as substrate. However, it retains circa 80% of its activity at a wide temperature range from 30 to 55 degrees C. We also describe improvements of neuraminidase determination method, which permits analysis in a microplate spectrophotometer, thereby increasing the sensitivity and reducing the costs of valuable reagents and biological samples.

Identification and functional expression of a second human beta-galactoside alpha2,6-sialyltransferase, ST6Gal II

BLAST analysis of the human and mouse genome sequence databases using the sequence of the human CMP-sialic acid:beta-galactoside alpha-2,6-sialyltransferase cDNA (hST6Gal I, EC2.4.99.1) as a probe allowed us to identify a putative sialyltransferase gene on chromosome 2. The sequence of the corresponding cDNA was also found as an expressed sequence tag of human brain. This gene contained a 1590 bp open reading frame divided in five exons and the deduced amino-acid sequence didn't correspond to any sialyltransferase already known in other species. Multiple sequence alignment and subsequent phylogenic analysis showed that this new enzyme belonged to the ST6Gal subfamily and shared 48% identity with hST6Gal-I. Consequently, we named this new sialyltransferase ST6Gal II. A construction in pFlag vector transfected in COS-7 cells gave raise to a soluble active form of ST6Gal II. Enzymatic assays indicate that the best acceptor substrate of ST6Gal II was the free disaccharide Galbeta1-4GlcNAc structure whereas ST6Gal I preferred Galbeta1-4GlcNAc-R disaccharide sequence linked to a protein. The alpha2,6-linkage was confirmed by the increase of Sambucus nigra agglutinin-lectin binding to the cell surface of CHO transfected with the cDNA encoding ST6Gal II and by specific sialidases treatment. In addition, the ST6Gal II gene showed a very tissue specific pattern of expression because it was found essentially in brain whereas ST6Gal I gene is ubiquitously expressed.

Regulation of N-glycolylneuraminic acid biosynthesis in developing pig small intestine

N -Glycolylneuraminic acid (Neu5Gc), an abundant sialic acid in animal glycoconjugates, is formed by the enzyme CMP-N-acetylneuraminic acid (CMP-Neu5Ac) hydroxylase. The amount of Neu5Gc relative to other sialic acids is highly dependent on the species, tissue and developmental stage. Although the activity of the hydroxylase is a key factor in controlling Neu5Gc incorporation in adult animals, little is known about the regulation of hydroxylase expression and the role of this enzyme in determining changes in Neu5Gc during development. Using pig small intestine as a model system, the appearance of total sialic acid and the regulation of Neu5Gc biosynthesis during development were studied in various regions of this tissue. The amount of total sialic acid and Neu5Gc declined markedly in 2 weeks after birth. Although in subsequent developmental phases there were no positional differences in total sialic acid, a significant proximal-to-distal increase in Neu5Gc was detected. In all cases, a good correlation between the amount of Neu5Gc, the activity of the hydroxylase and the level of hydroxylase mRNA was observed. However, Western-blot analysis revealed considerable accumulation of less active enzyme in the post partum period, which persisted until adulthood. No evidence for cytosolic factors influencing the hydroxylase activity or for the formation of truncated enzyme was found, raising the possibility that other regulatory mechanisms are involved. The relevance of these results in the formation of Neu5Gc as a receptor for certain pig enteric pathogens is also discussed.

Apoptosis in lymph nodes and changes in lymphocyte subpopulations in peripheral blood of pigs infected with porcine rubulavirus

In a first experiment, five pigs were inoculated intranasally with porcine rubulavirus (PoRV) at 5 days of age and killed 7 days post-infection (pi). In a second experiment, four pigs were infected with the same virus at 17 days of age and killed at 9 or 15 days pi. Control piglets in each experiment received uninfected cell culture supernate. All PoRV-infected pigs developed respiratory and nervous signs, and histological lesions of non-suppurative encephalitis and interstitial pneumonia. All control pigs remained clinically normal and did not have histological lesions. Significantly increased numbers of apoptotic cells were detected by terminal deoxynucleotidyl transferase biotin-dUTP nick end labelling (TUNEL) in tonsil and lymph nodes of the pigs infected at 7 days of age and killed at 7 days pi. Significantly increased percentages of CD2(+) and CD8(+) T lymphocytes were also found in peripheral blood of these animals at this time, while the percentages of CD4(+) and MHC class II lymphocytes were significantly reduced. Significantly increased numbers of apoptotic cells were detected in lymphoid tissues of the pigs infected at 17 days of age and killed at 9 days pi. The percentages of CD2(+), CD8(+) and MHC class II lymphocytes in peripheral blood were also significantly increased at this time; the percentage of MHC class II lymphocytes remained elevated at 15 days pi. These results indicate that induction of apoptosis is an important mechanism in the pathogenesis of PoRV infection in young pigs, and that this virus induces changes in lymphocyte subpopulations in peripheral blood.

Sialylation is modulated through maturation in hemocytes from Macrobrachium rosenbergii

In this work we identified in adult and juvenile freshwater prawn, Macrobrachium rosenbergii, three major type of circulating hemocytes: fusiform; rounded; and large ovoid hemocytes. Rounded and large hemocytes represent the first defense line, since this type of cells exerts phagocytic activity as well as lectin synthesis. Considering that glycosylation plays important roles in cell communication and as a target for pathogenic microorganisms, in this report was also described the main glycosidic modifications that occur in the large and rounded hemocytes from the freshwater prawn during maturation as determined with lectins. Neu5Acalpha2,6Gal, was identified homogeneously distributed in the membrane in 90% of hemocytes from juvenile organisms. Maturation of the freshwater prawn induced a decrease or complete loss of Neu5Acalpha2,6Gal residues that were replaced with Neu5Acalpha2,3 molecules in practically all hemocytes from adult organisms. This change was paralleled by a diminution in 9-O-acetyl-neuraminic acid (Neu5,9Ac(2)) expression. T and Tn antigens (Galbetal,3 GalNAcalpha1-0-Ser/Thr or GalNAcalpha1-0-Ser/Thr, respectively), as well as N-glycosidically linked glycans, seem to be highly conserved throughout maturation. Our results show that sialylation of freshwater prawn hemocytes is modulated throughout the maturation process.

Comparative evaluation of the CD4+CD8+ and CD4+CD8- lymphocytes in the immune response to porcine rubulavirus

The porcine immune system is unique in the expression of CD4+CD8+ (double-positive, DP) lymphocytes. These cells have been associated with immunological memory due to their gradual increase with age, the expression of memory phenotype and their ability to respond to recall viral antigen. This work analyzes the biological function of CD4+CD8- and CD4+CD8+ lymphocytes in the immune response to porcine rubulavirus (PRv). CD4+CD8- cells isolated from pigs 3 weeks after infection with porcine rubulavirus proliferated in response to homologous virus and generated lymphoblasts which were predominantly of the CD4+CD8+ phenotype, whereas stimulation with mitogen induced proliferation but did not switch the phenotype. CD4+CD8- lymphocytes isolated after 10 weeks of infection proliferated in response to phytohemagglutinin (PHA) but did not proliferate in response to homologous virus and did not change their phenotype, whereas CD4+CD8+ lymphocytes proliferated in response to PHA and to viral antigen. The cytokine profile of both lymphocyte populations showed the presence of IL-2 and IL-10 transcripts, quantitation demonstrated that CD4+CD8+ cells expressed mainly IL-10, whereas CD4+CD8- lymphocytes expressed primarily IL-2. Our results show that CD4+CD8- lymphocytes in the early phase of porcine rubulavirus infection can be converted to double-positive cells expressing IL-10 in an antigen-dependent manner, and that CD4+CD8- T-cells late in infection do not acquire CD8.