Virological and immunological characteristics of fatal virus-associated haemophagocytic syndrome (VAHS)

We report three infants and one teenager with fatal virus-associated haemophagocytic syndrome (VAHS). Two infants were admitted to our hospital because of cardio-pulmonary arrest (CPA). The third infant was admitted to our department because of fever and liver dysfunction, and he was diagnosed as combined immunodeficiency with predominant T cell defect. The teenager was diagnosed as systemic lupus erythema (SLE) when she was 10 years old and admitted to our department because of fever and thrombocytopenia . The histological findings for the four patients' organs revealed many haemophagocytic cells . The patients were infected by Parainfluenza virus type 2 (PIV2), Enterovirus (EV), Cytomegalovirus (CMV), and Epstein-Barr virus (EBV), respectively. Their laboratory data revealed elevated levels of ferritin and IL-6, which also suggested virus-associated haemophagocytic syndrome (VAHS). Although aggressive therapies were performed in all cases, the outcome was fatal. Further investigation would be needed to clarify the mechanism of VAHS and an effective therapeutic regimen is needed.

Altered function in CD8+ T cells following paramyxovirus infection of the respiratory tract

For many respiratory pathogens, CD8+ T cells have been shown to play a critical role in clearance. However, there are still many unanswered questions with regard to the factors that promote the most efficacious immune response and the potential for immunoregulation of effector cells at the local site of infection. We have used infection of the respiratory tract with the model paramyxovirus simian virus 5 (SV5) to study CD8+ T-cell responses in the lung. For the present study, we report that over time a population of nonresponsive, virus-specific CD8+ T cells emerged in the lung, culminating in a lack of function in approximately 85% of cells specific for the immunodominant epitope from the viral matrix (M) protein by day 40 postinfection. Concurrent with the induction of nonresponsiveness, virus-specific cells that retained function at later times postinfection exhibited an increased requirement for CD8 engagement. This change was coupled with a nearly complete loss of functional phosphoprotein-specific cells, a response previously shown to be almost exclusively CD8 independent. These studies add to the growing evidence for immune dysregulation following viral infection of the respiratory tract.

Experimental porcine rubulavirus (La Piedad-Michoacan virus) infection in pregnant gilts

Porcine rubulavirus (La Piedad-Michoacan virus) (PoRV-LPMV) is a member of the Paramyxoviridae family that causes encephalitis in young piglets and infertility in adult sows and boars. Infertility in sows naturally infected by PoRV-LPMV is characterized by an increased number of returns to oestrus, stillbirths and mummified fetuses. In this study, nine seronegative gilts were inoculated intranasally with the PAC-3 strain of PoRV-LPMV at week 6 or 10 of gestation. These animals were then killed at weeks 8 or 15 of gestation (seven gilts) or after natural parturition (two gilts). Four control gilts were mock-infected at gestation week 6 or 10 and killed between 2 and 4 weeks later. Gross lesions of focal congestion and haemorrhage were seen in the placenta and endometrium of one gilt infected at gestation week 6 and one infected at gestation week 10. PoRV-LPMV was isolated, at 2-6 weeks post-inoculation (pi), from lung, tonsils, ovary, placenta, uterus and lymph nodes of three of the gilts infected at gestation week 6 and at 2-3 weeks pi from lung, tonsil and ovary of two gilts infected at gestation week 10. Many of the fetuses of eight infected gilts were smaller than normal and had dermal ecchymoses. Dehydrated or mummified fetuses were present in six of the infected gilts but not in any control animal. PoRV-LPMV was isolated from brain, lung and liver of fetuses from two gilts infected at gestation week 6, and from two infected at gestation week 10. These results indicate that, after experimental infection, PoRV can replicate in tissues of seronegative pregnant gilts, cross the placenta, and cause fetal death and mummification.

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.

High resistance of human parainfluenza type 2 virus protein-expressing cells to the antiviral and anti-cell proliferative activities of alpha/beta interferons: cysteine-rich V-specific domain is required for high resistance to the interferons

Human parainfluenza type 2 virus (hPIV-2)-infected HeLa (HeLa-CA) cells and hPIV-2 V-expressing HeLa (HeLa-V) cells show high resistance to alpha/beta interferons (IFN-alpha/beta) irrespective of whether vesicular stomatitis virus or Sindbis virus is used as a challenge virus. When Sindbis virus is used, these cells show high susceptibility to human IFN-gamma. Furthermore, the multiplication of HeLa-V cells is not inhibited by IFN-alpha/beta. HeLa cells expressing the N-terminally truncated V protein show resistance to IFN-alpha/beta, showing that the IFN resistance determinant maps to the cysteine-rich V-specific domain. A complete defect of Stat2 is found in HeLa-CA and HeLa-V cells, whereas the levels of Stat1 expression are not significantly different among HeLa, HeLa-CA, HeLa-P, and HeLa-V cells, indicating that IFN-alpha/beta resistance of HeLa-CA and HeLa-V cells is due to a defect of Stat2. HeLa-SV41V cells show high resistance to all IFNs, and no expression of Stat1 can be detected. Stat2 mRNA is fully detected in HeLa-V cells. Stat2 was scarcely pulse-labeled in the HeLa-V cells, indicating that synthesis of Stat2 is suppressed or Stat2 is very rapidly degraded in HeLa-V cells. The V protein suppresses the in vitro translation of Stat2 mRNA more extensively than that of Stat1 mRNA. An extremely small amount of Stat2 can be detected in HeLa-V cells treated with proteasome inhibitors. The half-life of Stat2 is approximately 3.5 and 2 h in uninfected and hPIV-2-infected HeLa cells, respectively. This study shows that synthesis of Stat2 may be suppressed and Stat2 degradation is also enhanced in hPIV-2-infected HeLa and HeLa-V cells.

Porcine rubulavirus LPMV RNA persists in the central nervous system of pigs after recovery from acute infection

In order to study persistence of the porcine rubulavirus LPMV, we examined tissue samples collected from pigs 53 days after experimental infection. These pigs survived the initial infection and could clinically be considered to have recovered from the infection. Two of the pigs used in this study were chemically immunosuppressed during the last 4 days before necropsy. No infectious virus or viral antigen could be detected in any tissue using standard methods for virus isolation and detection. However, the presence of viral genomic RNA and mRNA could be demonstrated in the mid brain of the convalescent pig using an optimised RT-nested PCR. Mid brain, forebrain and lung were all shown to contain LPMV RNA in the immunosuppressed convalescent pigs. In addition we examined the P-gene editing in the recovered pigs and conclude that the viral genome is transcriptionally active in these pigs. The relevance of the persistence of LPMV for maintenance and spread within and/or between pig populations is discussed.

Avian paramyxoviruses serotype 3 isolated from captive birds in Israel: clinical signs, pathology, and antigenic characterization

Thirteen HA agents were isolated in Israel from captive flamingoes (Phoenicopterus ruber), Egyptian geese (Alopochen aegyptiacus) belonging to order Anseriformes, and ibis (Guara rubra) belonging to order Ciconiiformes. The isolation was done from postmortem materials in three cases of severe respiratory disease with high mortality. The isolates were examined serologically and identified as belonging to the serotype 3 of avian paramyxoviruses (APMV-3). The isolates were more close antigenically to the APMV-3b variety (prototype strain--APMV-3/Parakeet/Netherlands/449/75) than to the APMV-3a variety (prototype strain--APMV-3/Turkey/Wisconsin/68). This is the first isolation of APMV-3 from birds belonging to the orders Anseriformes and Ciconiiformes.

Lesions in the reproductive tract of boars experimentally infected with porcine rubulavirus

"Blue eye" disease of pigs in Mexico is caused by porcine rubulavirus and characterized by infertility in sows and boars, nervous signs in young pigs, and corneal opacity in pigs of all ages. The pathogenesis of reproductive tract lesions in rubulavirus-infected boars has not previously been investigated. In a first experiment, four 9-month-old boars were inoculated with porcine rubulavirus and killed 5, 15, 30 or 45 days post-inoculation (pi). In a second experiment, four similar boars were inoculated with the same virus and two animals were killed on each of days 70 and 80 pi. Swelling of the head of the epididymis developed in all inoculated boars at approximately day 15 pi. Reduced spermatozoan motility and concentration were detected in semen samples collected from one boar from day 21 pi. At post-mortem examination, nodules were seen in the head of the epididymis of the boars killed 15, 30 or 45 days pi and the right testis of the pig killed 30 days pi was atrophic. Corresponding histopathological epididymal alterations included formation of spermatic granulomas and vacuolar degeneration of ductular epithelium. These lesions were associated with mononuclear cell infiltration and interstitial fibroplasia. Degeneration of seminiferous tubules and interstitial mononuclear cell infiltration were seen in the atrophic testis of the pig killed 30 days pi. There was fibrosis of the head of the epididymis in all boars killed 70 or 80 days pi and one of these animals also had right testicular atrophy associated with degeneration of seminiferous tubules, lymphocytic infiltration and giant cell formation. Porcine rubulavirus antigen was detected by immunofluorescence labelling in the head of the epididymis of the pigs killed 15, 30 or 45 days pi and in one animal killed on day 70 pi. These results indicate that porcine rubulavirus can cause severe epididymo-orchitis and reduced semen quality in sexually mature boars.

Failure to induce formation of proteinase K resistant fibrils in pigeons through experimental infection with paramyxovirus type 1

Ten racing pigeons were infected experimentally with the paramyxovirus (PMV) type 1 of the pigeon. Within twelve weeks of observation, they were euthanized at different times. Their brains were examined for proteinase K resistant fibrils and histopathologically for spongiform lesions. No proteinase K resistant fibrils and no spongiform lesions could be detected in any case. Therefore, it is estimated that PMV type 1 of the pigeon is not likely to induce pathogenic mechanisms assumed for transmissible spongiform encephalopathies.