Long-term RNA persistence of porcine rubulavirus (PorPV-LPMV) after an outbreak of a natural infection: the detection of viral mRNA in sentinel pigs suggests viral transmission

The persistence of porcine rubulavirus (PorPV-LPMV) in five pigs that had survived an outbreak of a natural infection was determined. After the resolution of the outbreak, each animal was housed in an isolation pen together with one sentinel pig. Approximately every 2 months thereafter one group of animals was euthanized and tissue samples taken for virological and serological analysis. Infectious virus was not isolated from any samples; antibodies to PorPV-LPMV were detected in convalescent pigs by virus neutralisation test and blocking ELISA but not in sentinel pigs. PorPV-LPMV mRNA of the nucleoprotein (NP) and phosphoprotein (P) genes was detected by a nested polymerase chain reaction (nPCR) in samples of trigeminal and optic nerves, cervical spinal cord, tonsils, salivary gland, lung and pancreas from convalescent pigs. mRNA was also detected in the midbrain, corpus callosum, or olfactory bulb in four out of five pigs by nRT-PCR, this result was confirmed by the sequencing of a 260bp PCR product of P gene region. The highest average viral copies/μg of total RNA occurred in the olfactory bulb and pancreas tissues of convalescent pigs and midbrain, tonsil and pancreas of sentinel pigs housed with the convalescent pigs. Satellitosis and gliosis of the midbrain, olfactory bulb, corpus callosum, medulla oblongata or choroid plexus were microscopically observed in four convalescent pigs. The control pig remained negative in all tests. The results indicate that PorPV-LPMV mRNA persists and induces a durable humoral immune response in pigs that have recovered from a natural infection. After a possible reactivation of the virus, it was transmitted to sentinel pigs in contact with the convalescent pigs.

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.

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.

NeuAc alpha 2,3gal-glycoconjugate expression determines cell susceptibility to the porcine rubulavirus LPMV

Relevance of membrane sialoglycoconjugates as receptors for infection by the porcine rubulavirus has been determined in vitro by sugar and lectin competition assays and by inhibition of glycosylation. Our results show that NeuAc alpha 2,3Gal but not NeuAc alpha 2,6Gal inhibits the virus infectivity of Vero cells, and the virus was effectively blocked with the lectin Maackia amurensis, specific for NeuAc alpha 2,3Gal. Inhibition of the cellular glycosylation with tunicamycin, deoxinojirimycin as well as neuraminidase treatment diminishes the viral capacity to bind and infect this cell line. Dexamethasone, which promotes the activity of sialyl alpha 2,6 glycosyltransferase, also diminishes the cell susceptibility for infection. This is the first report confirming that NeuAc alpha-2,3Gal recognition is determinant in the pathogenesis of the porcine rubulavirus.

The porcine paramyxovirus LPM specifically recognizes sialyl (alpha 2,3) lactose-containing structures

The porcine paramyxovirus LPM recognizes alpha, but not beta, anomers of sialic acid containing structures, specifically sialyl (alpha 2,3) lactose. The virus specificity is directed to the sialyl residue and to the C'4 axial OH and the C'6 CH2OH of the galactose present in this structure.

Ultrastructural changes associated with the inhibition of monocyte chemotaxis caused by products of axenically grown Entamoeba histolytica

The supernatant fluid of axenically grown Entamoeba histolytica-HM1 significantly modifies the ultrastructural features associated with monocyte chemotaxis as assayed in Boyden chambers. This morphological evidence supports the existence of a factor, monocyte locomotion inhibitory factor (MLIF), produced by E. histolytica that inhibits the in vitro locomotion of human monocytes. None of the leucocyte-locomotion modifying drugs included in this study (i.e., cytochalasin-B, colchicine, vinblastine, and hydrocortisone) caused changes totally comparable with those induced by MLIF. The most striking feature was the increase of centriole-associated microtubules induced by MLIF and by cytochalasin-B. MLIF may inhibit monocyte locomotion by directly inducing excessive microtubule assembly, although a direct, if somewhat weak effect upon microfilaments cannot be excluded. The increase in microtubules could then represent a perhaps futile attempt of the microtubule organizing center to overcome the locomotion blockade that has occurred elsewhere in the cell. If active in vivo, MLIF may contribute to the paucity of inflammation in the advanced stages of invasive amebiasis, and consequently to the lack of scar tissue formation upon recovery from such lesions, as monocytes constitute an essential link to the healing process.

An ultrastructural and immunofluorescent study of rabies virus in tissue culture for antiviral drug evaluation

With the purpose of establishing a model for antiviral drug evaluation the ERA and V319 rabies fixed virus strains were studied in tissue cultures, for studies of the rabies virus cycle. Viral incubation was made using a low viral input multiplicity and allowing substances that may alter, cell or virus morphology. Immunofluorescence and electron microscopy studies were carried out for quantitative evaluation of structures involved in rabies virus replication after a 24 hours incubation period. The number of fluorescent cells decreased with the viral dilutions. ERA rabies strain had more fluorescent cells than V319 strain. Also viral structures were commonly found on different penetration steps to the cells, with the ERA strain. Interpretation of our results was made on the basis that ERA strain showed a shorter latency period than the V319 rabies strain. Differences in the replication pattern between fixed rabies strains using similar experimental conditions were found.

Meiotic arrest at first spermatocyte level: a new inherited infertility disorder

Three 46,XY phenotypically male, azoospermic brothers out of thirteen sibs from a consanguineous marriage were studied and found to have a unique pattern of testicular histology with arrest of spermatogenesis at the pachytene stage of primary spermatocytes. Endocrinological evaluation showed elevated plasma luteinizing(LH) and normal to elevated follicle-stimulating (FSH) hormones, positive gonadotropin pituitary response to luteinizing hormone-releasing hormone, depletion of LH and FSH levels by exogenous testosterone (T) administration, normal levels of T and dihydrotestosterone hormones, and elevation of T after stimulation with human chorionic gonadotropin hormone. Electrophoretic assay of lactic dehydrogenase isozymes did not reveal band C4 in semen or testicular tissue. These traits seem to constitute a hitherto undescribed form of infertility in which spermatogenesis arrest at the first spermatocyte level is the main feature. The parental consanguinity suggests autosomal recessive inheritance.

In vitro effect of isoprinosine on rabies virus

The in vitro effect of isoprinosine, an antiviral compound, was evaluated on ERA and VA319 rabies viral strains. Isoprinosine diminished the number of immunofluorescent cells, viral titers, and structures involved in rabies virus replication. Mechanism of antiviral action was probably mediated by modification of the polyribosome conformation and function.

A simple and rapid technique to isolate enriched populations of spermatocytes and spermatids from the immature rat testis

A technique was developed to obtain enriched populations of large numbers of primary spermatacytes (70--81%) and of spermatids (75%) from immature rat testes (21--23 and 38 days old respectively) in a simple and rapid fashion. The cells were nearly all viable and membrane preservation was good. The testicular cells were dispersed by a mild mechanical treatment combined with an incubation with purified collagenase, and the cell populations were separated by centrifugation in a discontinuous dextran gradient in a cell culture medium.

Inherited congenital normofunctional testicular hyperplasia and mental deficiency. A corroborative study

Three 46,XY unrelated individuals out of 84 postpubertal male inpatients with severe mental deficiency in a psychiatric hospital were found to have megalorchidia and macrogenitosomia. One of the cases had a similarly affected brother. Endocrine studies were performed in two of the cases with similar results. Normal plasma levels of pituitary gonadotropins were found. A normal testicular function was demonstrated by the finding of normal: (a) baseline plasma testosterone levels and a significant rise following human chorionic gonadotropin administration, (b) sperm analysis, and (c) morphology and cell architecture of the testes. These results were compatible with normofunctional testicular hyperplasia confirming previous observations and allowing the definite individualization of a syndrome with mental deficiency probably due to an X-linked recessive mutation.

Fine structure of mule testes: light and electron microscopy study

Testes of 3 mules, 3 stallions, and 3 donkeys were studied by light and electron microscopic techniques. Mule testes were firm, with an average weight less than that of stallion or donkey testes. As expected, mule seminiferous tubules had few cell elements. There were 2 cell populations within the seminiferous tubules: (a) Only basal spermatogonia and Sertoli's cells in 70% of the tubules and, (b) the cells in (a) plus leptotene and pachytene primary spermatocytes in 30% of the tubules. Degenerative changes occurred at the pachytene stage and began with the appearance of nuclear vesicles and chromatin condensation. The last stages disclosed pyknotic nuclei and cytoplasmic vesicles. The interstitia were filled by connective tissue elements and few Leydig's cells. Interstitial cells had well-developed, smooth endoplasmic reticula and mitochondria, indicating a normal steroidogenic activity. Epididymides in the mule had morphologic features similar to those of the stallion or donkey, except for the presence of intertubular fibrosis. Degenerative changes in primary spermatocytes indicate metabolic alterations which could be explained by the blockage of meiosis.

The fine structure of the glycocalyx of equine spermatozoa: a high-resolution cytochemical study

Equine spermatozoa were obtained from ejaculates of young stallions. The seminal plasma was removed and the sperm pellets washed three times with 0-15 M-NaCl solution before final centrifugation at 4500 g for 15 min. The pellets were fixed in a mixture of 2-5% glutaraldehyde in 0-1 M-cacodylate buffer, pH 7-4, with 0-5% Alcian blue and post-fixed in 1% osmium tetroxide with 1% lanthanum nitrate; other samples were treated with ruthenium red. All samples were dehydrated in ascending concentrations of ethanol, embedded in araldite and thin sections examined in an electron microscope. Electron dense deposits of lanthanum were present on the surface plasmalemma of the head, mid-piece and tail of 70% of mature spermatozoa, and similar deposits were seen in ruthenium red-treated samples. No glycocalyx was observed in untreated spermatozoa.

Fine structure of the gonads of the horse and its functional implications

Light and electron microscopic studies of the gonads of the fetal horse have shown that, in their hypertrophic condition which begins during the 3rd month, the interstitial cells contain large amounts of smooth endoplasmic reticulum, suggesting a secretory activity. Hydroxylating activity which was cytochrome P-450-dependent was observed in the fetal testis and may be involved in steroid biosynthesis.