Tetherin antagonism by V proteins is a common trait among the genus Rubulavirus.

Tetherin (BST-2/CD317/HM1.24) is an anti-viral factor that restricts the budding of several enveloped viruses. Most of these viruses have evolved to encode tetherin antagonists. Our previous study demonstrated that the growth of human parainfluenza virus type 2 (hPIV-2), a member of the genus Rubulavirus in the family Paramyxoviridae, was inhibited by tetherin, and its V protein decreases the amount of cell surface tetherin by the interaction. In the present study, we investigated whether tetherin inhibits the growth of other rubulaviruses including PIV-5, mumps virus (MuV), simian virus 41, and hPIV-4, and whether their V proteins act as tetherin antagonists. Plaque assay demonstrated that the growth of PIV-5 and MuV was inhibited by tetherin. Flow cytometry and immunoblot analyses revealed that the infection of PIV-5 and MuV caused reduction of cell surface tetherin without affecting total amount of tetherin. Immunoprecipitation analysis showed that all V proteins of rubulaviruses tested bound to tetherin. These results suggest that tetherin antagonism by V proteins is common among the genus Rubulavirus.

Cloning, expression and characterization of potential immunogenic recombinant hemagglutinin-neuraminidase protein of Porcine rubulavirus.

Blue eye disease caused by Porcine rubulavirus (PorPV) is an endemic viral infection of swine causing neurological and respiratory disease in piglets, and reproductive failure in sows and boars. The hemagglutinin-neuraminidase (HN) glycoprotein of PorPV is the most abundant component in the viral envelope and the main target of the immune response in infected animals. In this study, we expressed the HN-PorPV-recombinant (rHN-PorPV) protein in an Escherichia coli system and analyzed the immune responses in mice. The HN gene was cloned from the reference strain PorPV-La Piedad Michoacan Virus (GenBank accession number BK005918), into the pDual expression vector. The expressed protein was identified at a molecular weight of 61.7 kDa. Three-dimensional modeling showed that the main conformational and functional domains of the rHN-PorPV protein were preserved. The antigenicity of the expressed protein was confirmed by Western blot with a monoclonal antibody recognizing the HN, and by testing against serum samples from pigs experimentally infected with PorPV. The immunogenicity of the rHN-PorPV protein was tested by inoculation of BALB/c mice with AbISCO-100(®) as adjuvant. Analysis of the humoral immune responses in mice showed an increased level of specific antibodies 14 days after the first immunization, compared to the control group (P < 0.0005). The results show the ability of the rHN-PorPV protein to induce an antibody response in mice. Due to its immunogenic potential, the rHN-PorPV protein will be further evaluated in pig trials for its suitability for prevention and control of blue eye disease.

Efficacy of parainfluenza virus 5 mutants expressing hemagglutinin from H5N1 influenza A virus in mice.

Parainfluenza virus 5 (PIV5) is a promising viral vector for vaccine development. PIV5 is safe, stable, efficacious, cost-effective to produce and, most interestingly, it overcomes preexisting antivector immunity. We have recently reported that PIV5 expressing the hemagglutinin (HA) from highly pathogenic avian influenza (HPAI) virus H5N1 (PIV5-H5) provides sterilizing immunity against lethal doses of HPAI H5N1 infection in mice. It is thought that induction of apoptosis can lead to enhanced antigen presentation. Previously, we have shown that deleting the SH gene and the conserved C terminus of the V gene in PIV5 results in mutant viruses (PIV5ΔSH and PIV5VΔC) that enhance induction of apoptosis. In this study, we inserted the HA gene of H5N1 into PIV5ΔSH (PIV5ΔSH-H5) or PIV5VΔC (PIV5VΔC-H5) and compared their efficacies as vaccine candidates to PIV5-H5. We have found that PIV5ΔSH-H5 induced the highest levels of anti-HA antibodies, the strongest T cell responses, and the best protection against an H5N1 lethal challenge in mice. These results suggest that PIV5ΔSH is a better vaccine vector than wild-type PIV5.

Comparison of hemagglutination inhibition tests, immunoperoxidase monolayer assays, and serum neutralizing tests in detecting antibodies against blue eye disease in pigs.

Blue eye disease (BED) of pigs was identified in the early 1980s in La Piedad, Michoacan, Mexico. The causal agent is Porcine orthorubulavirus (PRV), which affects pigs of all ages, producing nervous, respiratory, and reproductive disorders. BED is geographically endemic to the center of Mexico, where 75% of the country's swine industry is concentrated. Due to its adverse effects on the swine industry and the risk of dissemination to other countries, it is essential to have reliable diagnostic methods for BED. The objective of this study was to establish the optimal conditions for three serological tests, hemagglutination inhibition (HI), immunoperoxidase monolayer assay (IPMA), and serum neutralization (SN), and to compare their sensitivity, specificity, kappa coefficient, and predictive values. Twelve different HI protocols (9408 tests), one SN protocol and one IPMA protocol (784 tests, each) were evaluated. Forty-nine sera were analyzed, and thirty-seven sera showed true positive results, while twelve showed true negative results. The kappa coefficient was used to assess the variation in each test. The best HI protocol registered a sensitivity and specificity of 89 and 100%, respectively, the IPMA test showed values of 85 and 100%, and the SN test registered a sensitivity of 91% and a specificity of 96%. One of the disadvantages of the HI test is that when chicken red blood cells (RBCs) are used, elution occurs in a short incubation time, which would decrease the specificity. The use of bovine RBCs increases the specificity of the testy and makes it more stable, but it decreases the sensitivity. The results of HI and SN revealed the importance of eliminating the complement system of the serum and removing other inhibitors to avoid test nonspecificity. The IPMA test does not use an active virus; hence, it is considered safe and does not present any risk of disseminating PRV.

Immunoinformatics approach for predicting epitopes in HN and F proteins of Porcine rubulavirus.

Porcine rubulavirus (PRV), which belongs to the family Paramyxoviridae, causes blue eye disease in pigs, characterized by encephalitis and reproductive failure in newborn and adult pigs, respectively. There is no effective treatment against PRV and no information on the effectiveness of the available vaccines. Continuous outbreaks have occurred in Mexico since the early 1980s, which have caused serious economic losses to pig producers. Vaccination can be used to control this disease. Searching for effective antigen candidates against PRV, we first sequenced the PAC1 F protein, then we used various immunoinformatics tools to predict antigenic determinants of B-cells and T-cells against the two glycoproteins of the virus (HN and F proteins). Finally, we used AutoDock Vina to determine the binding energies. We obtained the F gene sequence of a PRV strain collected in the early 1990s in Mexico and compared its amino acid profile with previous and more recent strains, obtaining an identity similarity of 97.78 to 99.26%. For the F proteins, seven linear B-cell epitopes, six conformational B-cell epitopes and twenty-nine T-cell MHC class I epitopes were predicted. For the HN proteins, sixteen linear B-cell epitopes, seven conformational B-cell epitopes and thirty-four T-cell MHC class I epitopes were predicted. The ATRSETDYY and AAYTTTTCF epitopes of the HN protein might be important for neutralizing the viral infection. We determined the in silico binding energy between the predicted epitopes on the F and HN proteins and swine MHC-I molecules. The binding energy of these epitopes ranged from -5.8 to -7.8 kcal/mol. The present study aimed to assess the use of HN and F proteins as antigens, either as recombinant proteins or as a series of peptides that could activate different responses of the immune system. This may help identify relevant immunogens, saving time and costs in the development of new vaccines or diagnostic tools.

Mumps outbreaks in vaccinated populations: are available mumps vaccines effective enough to prevent outbreaks?

Increased reports of mumps in vaccinated populations prompted a review of the performance of mumps vaccines. The effectiveness of prior vaccination with 1 dose of vaccine ranged from 72.8% to 91% for the Jeryl Lynn strain, from 54.4% to 93% for the Urabe strain, and from 0% to 33% for the Rubini strain. Vaccine effectiveness after 2 doses of mumps vaccine was reported in 3 outbreaks and ranged from 91% to 94.6%. There was evidence of waning immunity, which is a likely factor in mumps outbreaks, aggravated by possible antigenic differences between the vaccine strain and outbreak strains. Inadequate vaccine coverage or use of the Rubini vaccine strain accounted for the majority of outbreaks reviewed; however, some outbreaks could not be prevented, despite high vaccination coverage with 2 doses of the Jeryl Lynn vaccine strain. Our findings indicate the need for more-effective mumps vaccines and/or for review of current vaccination policies to prevent future outbreaks.

Alston Virus, a Novel Paramyxovirus Isolated from Bats Causes Upper Respiratory Tract Infection in Experimentally Challenged Ferrets.

Multiple viruses with zoonotic potential have been isolated from bats globally. Here we describe the isolation and characterization of a novel paramyxovirus, Alston virus (AlsPV), isolated from urine collected from an Australian pteropid bat colony in Alstonville, New South Wales. Characterization of AlsPV by whole-genome sequencing and analyzing antigenic relatedness revealed it is a rubulavirus that is closely related to parainfluenza virus 5 (PIV5). Intranasal exposure of mice to AlsPV resulted in no clinical signs of disease, although viral RNA was detected in the olfactory bulbs of two mice at 21 days post exposure. Oronasal challenge of ferrets resulted in subclinical upper respiratory tract infection, viral shedding in respiratory secretions, and detection of viral antigen in the olfactory bulb of the brain. These results imply that AlsPV may be similar to PIV5 in its ability to infect multiple mammalian host species. This isolation of a novel paramyxovirus with the potential to transmit from bats to other mammalian species reinforces the importance of continued surveillance of bats as a source of emerging viruses.

Seroprevalence of Human Parainfluenza Virus Types 1-4 Among Healthy Children Under 5 Years of Age in Korea.

Human parainfluenza viruses (HPIVs) are among the major causes of respiratory infections in children, worldwide, including in Korea. There are four types of HPIVs, each with different epidemiological characteristics. HPIV3 is the most frequently circulating HPIV type, while the epidemiology of HPIV4 remains unclear. The aim of this study was to investigate the age-stratified seropositivity rates of HPIV types 1-4 among children in Korea. These data will be useful to determine vaccine requirements. This study included 245 participants categorized into four age groups: 6-11 months, 1 year, 2 years, and 3-5 years. Hemagglutination inhibition (HAI) assay was used to measure the antibody titers in the serum samples of the subjects. Overall, a significantly higher seropositivity rate (68%) was observed for HPIV3 (p < 0.001), indicating the predominant circulation of this type. In the 3- to 5-year-old group, 97% of the participants displayed seropositivity for HPIV3, suggesting that most Korean children acquire HPIV3 infection by the age of 5 years. The seropositivity rate for HPIV3 increased with age (p < 0.001); a prompt rise was observed between the 6-11 months age group and the 1-year age group. The seropositivity rates of HPIV1, HPIV2, and HPIV4 were found to increase with age (p < 0.001), with a marked increase recorded after the age of 2 years. HPIV1, HPIV2, and HPIV4 tended to infect children later than HPIV3. Older children showed high antibody titer ranges for HPIV3 (p < 0.001), suggesting that children experience multiple HPIV3 infections. An increasing trend of HPIV4 seropositivity rates with age was observed and this was comparable to theHPIV1 and HPIV2 seropositivity rates, indicating that its incidence may have been underestimated. To reduce HPIV infection, the administration of a HPIV3 vaccine to children 1 year of age is likely to be the most effective option.

Identification of potential B cell epitope determinants by computer techniques, in hemagglutinin-neuraminidase from the porcine rubulavirus La Piedad Michoacan.

Hemagglutinin-neuraminidase (HN) from porcine rubulavirus La Piedad Michoacan (RvpLPM) is one of the most antigenic proteins known, and is responsible for virus-host cell interaction. We analyzed the amino acid sequence of HN, using computer-assisted techniques to identify B cell epitopes. From a pool of 18 possible antigenic peptides, we evaluated the antigenicity of the 2 peptides with the highest scores and the 1 with lowest score. Antibodies from RvpLPM-infected pigs recognized the synthesized HN-A, HN-B, and HN-R peptides (optical density [OD]: 0.33 +/- 0.02 for HN-A, 0.20 +/- 0.02 for HN-B, and 0.07 +/- 0.01 for HN-R); bovine serum albumin-coupled HN-A and HN-B induced rabbit anti-RvpLPM antibodies (OD: 0.39 +/- 0.01 for HN-A and 0.35 +/- 0.02 for HN-B). Loop 5 from the outer membrane protein, OmpC, from Salmonella typhi was replaced with HN-B; this protein was then expressed in Escherichia coli UH302. BALB/c mice were challenged intraperitoneally or orogastrically with the fusion protein expressed in E. coli and murine antibodies obtained from both types of administration inhibited virus-hemagglutinating activity, as did the antibodies from RvpLPM-infected swine. These results suggest that HN-A and HN-B are peptides involved in RvpLPM cell carbohydrate recognition, and could therefore be considered potential targets for vaccine and diagnostic procedures development.

La Piedad Michoacán Mexico Virus V protein antagonizes type I interferon response by binding STAT2 protein and preventing STATs nuclear translocation.

La Piedad Michoacán Mexico Virus (LPMV) is a member of the Rubulavirus genus within the Paramyxoviridae family. LPMV is the etiologic agent of "blue eye disease", causing a significant disease burden in swine in Mexico with long-term implications for the agricultural industry. This virus mainly affects piglets and is characterized by meningoencephalitis and respiratory distress. It also affects adult pigs, causing reduced fertility and abortions in females, and orchitis and epididymitis in males. Viruses of the Paramyxoviridae family evade the innate immune response by targeting components of the interferon (IFN) signaling pathway. The V protein, expressed by most paramyxoviruses, is a well-characterized IFN signaling antagonist. Until now, there were no reports on the role of the LPMV-V protein in inhibiting the IFN response. In this study we demonstrate that LPMV-V protein antagonizes type I but not type II IFN signaling by binding STAT2, a component of the type I IFN cascade. Our results indicate that the last 18 amino acids of LPMV-V protein are required for binding to STAT2 in human and swine cells. While LPMV-V protein does not affect the protein levels of STAT1 or STAT2, it does prevent the IFN-induced phosphorylation and nuclear translocation of STAT1 and STAT2 thereby inhibiting cellular responses to IFN α/ß.

Prevalence of rabies and LPM paramyxovirus antibody in non-hematophagous bats captured in the Central Pacific coast of Mexico.

To investigate if non-hematophagous bats play a role in outbreaks of rabies and blue eye disease (LPMV), we studied the seroprevalence against both agents in several species of non-hematophagous bats on the sub-tropical Pacific coast of the state of Colima, Mexico. The survey covered a predominantly agricultural area (disturbed), and an area dominated by semideciduous dry forest (undisturbed). A total of 151 non-hematophagous bats of 16 species were captured from the two areas. Fifty-six (37%) had antirabic antibodies (Ab) while 87 (58%) did not and 8 samples (5%) had to be discarded because of hemolysis. A much lower (P<0.05) prevalence of antirabic Ab was found in bats caught in disturbed areas (22.7%) compared with those from undisturbed areas (51.9%). The presence of antirabic Ab was not related to sex, genera or feeding habits. The higher prevalence found in bats in the undisturbed area may be the result of more frequent interspecies encounters. Of the 108 sera analyzed for antibodies against LPMV, only one was positive (a male Rhogeessa parvula major, captured in the undisturbed area). This suggests that bats in the surveyed localities do not play a role in the epidemiology of LPMV.

Uptake of porcine rubulavirus (LPMV) by PK-15 cells.

BACKGROUND: The porcine virus denominated La Piedad Michoacan Virus (LPMV) is a member of the family Paramyxoviridae and is the cause of a disease in pigs present only in Mexico. The disease is characterized by meningoencephalitis and respiratory distress in young pigs, epididymitis and orchitis in boars, and reproductive failure and abortion in sows. METHODS: The cytopathology, morphology, and distribution of the hemagglutination neuraminidase (HN) and nucleoprotein (NP) proteins of LPMV were investigated following inoculation into PK-15 cells. The cytopathic effect was characterized by cytoplasmic vacuolation and the formation of syncytia and cytoplasmic inclusion bodies. RESULTS: In immunofluorescence assays using a monoclonal antibody (MAb) against the HN protein at 5-60 min post-infection (early infection), a diffuse immunofluorescence was observed near the cell membrane and adjacent to the nuclear membrane. At 24 h post-infection (late infection), a dust-like immunofluorescence was observed throughout the cytoplasm. LPMV-infected cells incubated with the MAb against the NP protein showed punctate cytoplasmic fluorescence during the early stages of infection. At the late infection stage, these fluorescent particles became larger and were seen predominantly in the cytoplasm of syncytia. This pattern was also apparent by immunohistochemical labeling and immunogold electron microscopy. The latter technique revealed that HN protein was diffusely distributed throughout the cytoplasm. When using the MAb against the NP protein, nucleocapsid organization was the most prominent feature and resulted in the formation of cytoplasmic inclusion bodies visible by light and electron microscopy. Immunogold labeling of purified nucleocapsids was shown by electron microscopy. Virus particles and nucleocapsids were morphologically similar to members of the Paramyxoviridae family. CONCLUSIONS: The morphologic characteristics of the virions and the distribution patterns of the HN and NP proteins in PK-15 infected cells indicate that the mechanisms of LPMV replication are generally similar to those of the members of the Paramyxoviridae family.

Immunity to porcine rubulavirus infection in adult swine.

The immune response against the porcine rubulavirus was analyzed in experimentally infected adult pigs. High titers of virus neutralizing and hemagglutinating inhibitory antibodies were identified in infected animals. The antibody specificity was directed towards HN, M, and NP rubula virion proteins; immunodominance of HN proteins was demonstrated. Peripheral blood mononuclear cells from infected, but not from non-infected pigs proliferated in vitro in response to virus antigenic stimuli, showing a bell-shaped plot with the highest peak at 5 weeks post-infection. Virus-induced lymphoblasts expressed CD4+ CD8+ phenotype, whereas lectin-induced lymphoblasts were mainly identified as CD4+ CD8- cells. Phenotype analysis of freshly prepared PBMC revealed increased number of both monocytes (PoM1+) and total T lymphocytes (CD2+) early during infection, with reduced values of B lymphocytes at 4 weeks post-infection. Decrease in CD4+ CD8- blood cells was observed at 3 weeks post-infection, whereas both CD4- CD8+ and CD4+ CD8+ cells increased 1 and 4 weeks post-infection, respectively. This work discusses the relevance of CD4+ CD8+ T cells in the control of porcine rubulavirus infection.

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.

Development of a blocking ELISA for screening antibodies to porcine rubulavirus, La Piedad Michoacan Virus.

A blocking enzyme-linked immunosorbent assay (ELISA) was developed to detect antibodies to porcine rubulavirus (La Piedad Michoacan Virus [LPMV]) in serum samples from pigs. The test, based on a monoclonal antibody against the LPMV hemagglutinin-neuraminidase glycoprotein, had a sensitivity of 99% and a specificity of 97%. The results of this test were in agreement with those obtained by an indirect ELISA and hemagglutination inhibition, indirect immunofluorescence, and virus neutralization tests. The blocking ELISA is considered the most suitable test for routine screening for antibodies against LPMV.

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.

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.

Detection of Newcastle disease virus-specific antibodies in ostrich sera by three serological methods.

Sera from 211 ostriches were tested for the presence of Newcastle disease virus (NDV)-specific antibodies by the virus neutralisation test, the haemagglutination inhibition (HI) test and a recently developed avian paramyxovirus serotype 1 (PMV-1) specific monoclonal antibody blocking ELISA (b-ELISA). The virus neutralisation test was used as the reference for the estimation of the sensitivity and specificity of the b-ELISA and HI tests. Of the 211 sera, 140 contained NDV-specific neutralising antibodies, 130 were positive by the HI test and 122 by the b-ELISA. The sensitivity, specificity and predictive accuracy of the HI and b-ELISA tests relative to the virus neutralisation test were similar. The good agreement between the HI and b-ELISA test (kappa = 0.85) suggested that the two methods are interchangeable.

Establishment and characterisation of a porcine rubulavirus (LPMV) persistent infection in porcine kidney cells.

Porcine rubulavirus (LPMV) can establish persistent infections in porcine kidney cells. Cell cultures characterised at passages 25 and 65 demonstrated haemadsorption, formation of syncytia, and a slower growth rate. The nucleoprotein (NP) and haemagglutinin-neuraminidase (HN) protein were present in all cells, although not to the same extent as in wild type infected cells. Incubation of the cell cultures with virus neutralising antibodies could not cure them from the infection. The cells were resistant to LPMV high multiplicity superinfection, but lysed rapidly upon infection with VSV. These cells thus fulfilled the criteria of a true persistent infection. Viral particles were released into the medium from the persistently infected cells as measured by HA and infection of PK-15 cells with medium from the persistently infected cells. The infectious titer of the virus released from the persistently infected cells was 3 logs lower compared to wild type virus, the HN titer still being comparable. Virus released from the persistently infected cells was unable to cause a lytic infection in PK-15 cells, and showed a reduced ability to spread when compared to a LPMV lytic infection.

[New data on the development of complications during epidemiological parotitis in children]. / Novoe v patogeneze razvitiia oslozhnenii pri épidemicheskom parotite u detei.

The main factors in the pathogenesis of complicated parotitis virus infection are increased virus reproduction in the salivary gland, inhibited by the production of alpha-interferon at early stages of the infectious process. Entry of the virus into the CNS is caused by slight penetration of antiparotitis antibodies through the blood-brain barrier and by poor formation of specific immune complexes at the site of primary virus reproduction and in the liquor. Interferon therapy of patients with parotitis virus infection corrects the chain of processes in the pathogenesis. In parotitic meningitis neovir stimulates gamma-interferon, which blocks the synthesis of parotitis antigen in the cell and stimulates (through antibody stimulation) the formation of specific immune complexes released with the saliva in the gland. Viferon is more active in parotitic orchitis due to prolongation of alpha-interferon activity.