Teratogenic Rubella Virus Alters the Endodermal Differentiation Capacity of Human Induced Pluripotent Stem Cells

The study of congenital virus infections in humans requires suitable ex vivo platforms for the species-specific events during embryonal development. A prominent example for these infections is rubella virus (RV) which most commonly leads to defects in ear, heart, and eye development. We applied teratogenic RV to human induced pluripotent stem cells (iPSCs) followed by differentiation into cells of the three embryonic lineages (ecto-, meso-, and endoderm) as a cell culture model for blastocyst- and gastrulation-like stages. In the presence of RV, lineage-specific differentiation markers were expressed, indicating that lineage identity was maintained. However, portrait analysis of the transcriptomic expression signatures of all samples revealed that mock- and RV-infected endodermal cells were less related to each other than their ecto- and mesodermal counterparts. Markers for definitive endoderm were increased during RV infection. Profound alterations of the epigenetic landscape including the expression level of components of the chromatin remodeling complexes and an induction of type III interferons were found, especially after endodermal differentiation of RV-infected iPSCs. Moreover, the eye field transcription factors RAX and SIX3 and components of the gene set vasculogenesis were identified as dysregulated transcripts. Although iPSC morphology was maintained, the formation of embryoid bodies as three-dimensional cell aggregates and as such cellular adhesion capacity was impaired during RV infection. The correlation of the molecular alterations induced by RV during differentiation of iPSCs with the clinical signs of congenital rubella syndrome suggests mechanisms of viral impairment of human development.

Battery Powered Portable Thermal Cycler for Continuous-Flow Polymerase Chain Reaction Diagnosis by Single Thermostatic Thermoelectric Cooler and Open-Loop Controller

Temperature control is the most important and fundamental part of a polymerase chain reaction (PCR). To date, there have been several methods to realize the periodic heating and cooling of the thermal-cycler system for continuous-flow PCR reactions, and three of them were widely used: the thermo-cycled thermoelectric cooler (TEC), the heating block, and the thermostatic heater. In the present study, a new approach called open-loop controlled single thermostatic TEC was introduced to control the thermal cycle during the amplification process. Differing from the former three methods, the size of this microdevice is much smaller, especially when compared to the microdevice used in the heating block method. Furthermore, the rising and cooling speed of this method is much rapider than that in a traditional TEC cycler, and is nearly 20-30% faster than a single thermostatic heater. Thus, a portable PCR system was made without any external heat source, and only a Teflon tube-wrapped TEC chip was used to achieve the continuous-flow PCR reactions. This provides an efficient way to reduce the size of the system and simplify it. In addition, through further experiments, the microdevice is not only found to be capable of amplification of a PCR product from Human papillomavirus type 49 (Genbank ref: X74480.1) and Rubella virus (RUBV), but also enables clinical diagnostics, such as a test for hepatitis B virus.

Seroprevalence of measles, mumps & rubella antibodies among 5-10 years old children in north India

Background & objectives

: Globally, there is an effort to eliminate the measles and control rubella as these diseases lead to considerable morbidity and mortality especially among under-five children and are important public health problems. This study was aimed to estimate the seroprevalence of measles, mumps and rubella (MMR) antibodies among children of age 5-10 yr in Chandigarh, north India, to provide evidence on prevalent immunity levels.

Methods

: This cross-sectional study was conducted in Chandigarh, among 196 randomly selected healthy children (5-10 yr), who received either one or two doses of measles or MMR combination vaccine. Socio-economic background and immunization history were recorded. Blood sample (2 ml) was collected to estimate the MMR IgG antibody titres by using ELISA kits.

Results

: Protective seroprevalence of MMR antibodies was 40.8, 75.5 and 86.2 per cent, respectively. The geometric mean titres of MMR IgG antibodies in the study children were 11.3, 50.6 and 54.3 international units (IU)/ ml, respectively. The proportion of seroprotected children for measles was significantly higher among those who had received two or more doses (46.4%) of measles vaccine compared to those who had received single dose (35.6%) (P <0.001). About 16 per cent of children had received single dose of MMR vaccine. Among these, 71.4 and 100 per cent were seroprotected against mumps and rubella, respectively.

Interpretation & conclusions

: A large proportion of children aged 5-10 yr lacked protective immunity against measles (60%); about one-fourth (15-25%) were susceptible to infection with mumps and rubella virus. Mumps vaccination may be considered to be included in National Immunization Schedule for children with periodic serosurveillance.

Rubella Virus-Associated Cutaneous Granulomatous Disease: a Unique Complication in Immune-Deficient Patients, Not Limited to DNA Repair Disorders

The association of immunodeficiency-related vaccine-derived rubella virus (iVDRV) with cutaneous and visceral granulomatous disease has been reported in patients with primary immunodeficiency disorders (PIDs). The majority of these PID patients with rubella-positive granulomas had DNA repair disorders. To support this line of inquiry, we provide additional descriptive data on seven previously reported patients with Nijmegen breakage syndrome (NBS) (n = 3) and ataxia telangiectasia (AT) (n = 4) as well as eight previously unreported patients with iVDRV-induced cutaneous granulomas and DNA repair disorders including NBS (n = 1), AT (n = 5), DNA ligase 4 deficiency (n = 1), and Artemis deficiency (n = 1). We also provide descriptive data on several previously unreported PID patients with iVDRV-induced cutaneous granulomas including cartilage hair hypoplasia (n = 1), warts, hypogammaglobulinemia, immunodeficiency, myelokathexis (WHIM) syndrome (n = 1), MHC class II deficiency (n = 1), Coronin-1A deficiency (n = 1), X-linked severe combined immunodeficiency (X-SCID) (n = 1), and combined immunodeficiency without a molecular diagnosis (n = 1). At the time of this report, the median age of the patients with skin granulomas and DNA repair disorders was 9 years (range 3-18). Cutaneous granulomas have been documented in all, while visceral granulomas were observed in six cases (40%). All patients had received rubella virus vaccine. The median duration of time elapsed from vaccination to the development of cutaneous granulomas was 48 months (range 2-152). Hematopoietic cell transplantation was reported to result in scarring resolution of cutaneous granulomas in two patients with NBS, one patient with AT, one patient with Artemis deficiency, one patient with DNA Ligase 4 deficiency, one patient with MHC class II deficiency, and one patient with combined immunodeficiency without a known molecular etiology. Of the previously reported and unreported cases, the majority share the diagnosis of a DNA repair disorder. Analysis of additional patients with this complication may clarify determinants of rubella pathogenesis, identify specific immune defects resulting in chronic infection, and may lead to defect-specific therapies.

Illuminating uveitis: metagenomic deep sequencing identifies common and rare pathogens

BACKGROUND

Ocular infections remain a major cause of blindness and morbidity worldwide. While prognosis is dependent on the timing and accuracy of diagnosis, the etiology remains elusive in ~50 % of presumed infectious uveitis cases. The objective of this study is to determine if unbiased metagenomic deep sequencing (MDS) can accurately detect pathogens in intraocular fluid samples of patients with uveitis.

METHODS

This is a proof-of-concept study, in which intraocular fluid samples were obtained from five subjects with known diagnoses, and one subject with bilateral chronic uveitis without a known etiology. Samples were subjected to MDS, and results were compared with those from conventional diagnostic tests. Pathogens were identified using a rapid computational pipeline to analyze the non-host sequences obtained from MDS.

RESULTS

Unbiased MDS of intraocular fluid produced results concordant with known diagnoses in subjects with (n = 4) and without (n = 1) uveitis. Samples positive for Cryptococcus neoformans, Toxoplasma gondii, and herpes simplex virus 1 as tested by a Clinical Laboratory Improvement Amendments-certified laboratory were correctly identified with MDS. Rubella virus was identified in one case of chronic bilateral idiopathic uveitis. The subject's strain was most closely related to a German rubella virus strain isolated in 1992, one year before he developed a fever and rash while living in Germany. The pattern and the number of viral identified mutations present in the patient's strain were consistent with long-term viral replication in the eye.

CONCLUSIONS

MDS can identify fungi, parasites, and DNA and RNA viruses in minute volumes of intraocular fluid samples. The identification of chronic intraocular rubella virus infection highlights the eye's role as a long-term pathogen reservoir, which has implications for virus eradication and emerging global epidemics.

[The very severe sensorineural deafness patients caused by rubella virus infection: two cases report]

To explore the audiological features in children who were sever sensorineural hearing loss infected with rubella virus. There were two cases of rubella virus infection in children who were deaf, they conducted the distortion product otoacoustic emission, ABR and auditory steady-state evoked response (ASSR) examination, then analyzed the results comprehensively. Two patients' mothers were prompted to have infected rubella virus during the early three months pregnant period by history and laboratory tests. The two patients were not detected deafness gene mutation. Audiology results implied the two patients were very severe binaural sensorineural deafness, so they were recommended to equipped with hearing aids and cochlear implant surgery. Early pregnancy women infected with rubella virus can cause very severe offspring sensorineural deafness. The crowd whose mother were suspected to infect with rubella virus in early pregnancy, that should be tracked and detected hearing in order to achieve early detection, early intervention and early treatment.

[Epidemiologic control for rubella in pregnant women]

AIM

Evaluate effectiveness of measures specified by epidemiologic control for rubella in pregnant women.

MATERIALS AND METHODS

585 pregnant women with suspected measles were laboratory examined in 10 Regional Centers of Control for Measles and Rubella by EIA.

RESULTS

24 rubella infected pregnant women aged 16-36 years were detected among the examined pregnant women, most of those (91.7%) were either not immunized against rubella or had unknown immunization anamnesis: 16 women terminated pregnancy, in 8 women pregnancy ended with delivery at term. Of the 8 newborns only a single child had innate rubella infection (the child was clinically healthy).

CONCLUSION

Epidemiologic investigation of each rubella case in pregnant women with obligatory laboratory examination of women and source of infection revealed a significant number of women at childbearing age susceptible to rubella virus that retains the possibility of birth of children with innate rubella syndrome.

[Studying of molecular mechanisms of rubella virus attenuation evidence from Russian strain C-77]

Live attenuated rubella vaccine is used for vaccination. Temperature-sensitive (ts) phenotype was proved for almost all rubella vaccine strains, and the acquisition of the ts phenotype during cold adaptation was strongly correlated with the attenuation of the wild-type viruses. Nevertheless, the molecular mechanisms of the attenuation have been insufficiently understood for rubella virus. Study ofthese mechanisms, identifying genotypic markers of attenuation, which together with the sequence analyses could be used for genetic stability control of vaccine strains, is still of current interest. In this work, we determined nearly complete genome sequences of attenuated (ca) and the wildtype progenitor (wt) of the rubella virus strain C-77 isolated in Russia. Possible genetic determinants of attenuation were detected. Thus, 13 nucleotide differences leading to 6 amino acid substitutions were found. Four amino acid substitutions were found to be almost unique. Special consideration should be given to Tyr1042Cys substitution in the protease domain of C-77 strain, because it most probably plays the crucial role in acquisition of ts-phenotype.

[Molecular and biologic characteristics of attenuated rubella viruses]

AIM

To study stability/variability of rubella virus vaccine strain "Orlov-B" during its adaptation to other tissue substrate.

MATERIALS AND METHODS

Vaccine strains of rubella virus Wistar 27/3 and "Orlov-B" as well as wild type strains "Orlov-D" and "Lebedev" were used. Rhesus monkeys were used as laboratory animals. Standard virological, molecular and statistical methods were applied.

RESULTS

Obtained as a result of adaptation to other tissue substrate - diploid human cell line M-22 - strain "Orlov-D" demonstrated stability on RCT40 sign in in vitro experiments. Comparative genotyping of "Orlov-B" and "Orlov-D" strains on gene E1 showed identity of nucleotide sequences of both variants. Genetic stability of virus on the gene coding the most immunogenic protein E1 was confirmed in vivo: the stable high immunogenic and protective activity of both "Orlov-B" and "Orlov- D" strains was demonstrated in experiments on rhesus macaques.

CONCLUSION

New data on stability of attenuated rubella virus vaccine strains have practical significance for the development of new vaccines.

Microarray analyses of differentially expressed human genes and biological processes in ECV304 cells infected with rubella virus

Changes in mRNA expression levels of ECV304 cells infected with the wild-type rubella strain were analyzed using a microarray system representing 18,716 human genes. Four hundred eighty-seven genes exhibited differential expression levels; 456 of these genes were up-regulated while 31 genes were down-regulated. We identified 53 biological processes that were significantly relevant to the RV-infection. Among these biological processes, 52 were one-gene processes and one was a process involving five genes: IFNA21 (interferon, alpha 21), interferon stimulated exonuclease gene 20 kDa (ISG20), zinc finger protein 175 (ZNF175), tripartite motif-containing 22 (TRIM22), and MX2 [myxovirus (influenza virus) resistance 2 (mouse)]. Except for ZNF175, gene annotation indicated four of these genes encoded interferon or interferon-induced genes. These results suggest that genes relevant to interferon-regulated pathways may be involved in the pathogenesis of rubella.

Rubella virus-induced superinfection exclusion studied in cells with persisting replicons

For the first time, homologous superinfection exclusion was documented for rubella virus (RUB) by using Vero cells harbouring persisting RUB replicons. Infection with wild-type RUB was reduced by tenfold, whereas Sindbis virus infection was unaffected. Replication following infection with packaged replicons and transfection with replicon transcripts was also restricted in these cells, indicating that restriction occurred after penetration and entry. Translation of such 'supertransfecting' replicon transcripts was not impaired, but no accumulation of supertransfecting replicon RNA could be detected. We tested the hypothesis favoured in the related alphaviruses that superinfection exclusion is mediated by cleavage of the incoming non-structural precursor by the pre-existing non-structural (NS) protease, resulting in an inhibition of minus-strand RNA synthesis. However, cleavage of a precursor translated from a supertransfecting replicon transcript with an NS protease catalytic-site mutation was not detected and the event in the replication cycle at which superinfection exclusion is executed remains to be elucidated.

Analysis of the selective advantage conferred by a C-E1 fusion protein synthesized by rubella virus DI RNAs

During serial passaging of rubella virus (RUB) in cell culture, the dominant species of defective-interfering RNA (DI) generated contains an in-frame deletion between the capsid protein (C) gene and E1 glycoprotein gene resulting in production of a C-E1 fusion protein that is necessary for the maintenance of the DI [Tzeng, W.P., Frey, T.K. (2006). C-E1 fusion protein synthesized by rubella virus DI RNAs maintained during serial passage. Virology 356 198-207.]. A BHK cell line stably expressing the RUB structural proteins was established which was used to package DIs into virus particles following transfection with in vitro transcripts from DI infectious cDNA constructs. Packaging of a DI encoding an in-frame C-GFP-E1 reporter fusion protein corresponding to the C-E1 fusion protein expressed in a native DI was only marginally more efficient than packaging of a DI encoding GFP, indicating that the C-E1 fusion protein did not function by enhancing packaging. However, infection with the DI encoding the C-GFP-E1 fusion protein (in the absence of wt RUB helper virus) resulted in formation of clusters of GFP-positive cells and the percentage of GFP-positive cells in the culture following infection remained relatively constant. In contrast, a DI encoding GFP did not form GFP-positive clusters and the percentage of GFP-positive cells declined by roughly half from 2 to 4 days post-infection. Cluster formation and sustaining the percentage of infected (GFP-positive) cells required the C part of the fusion protein, including the downstream but not the upstream of two arginine clusters (both of which are associated with RNA binding and association with mitochondrial p32 protein) and the E1 part through the transmembrane sequence, but not the C-terminal cytoplasmic tail. Among a collection of mutant DI constructs, cluster formation and sustaining infected cell percentage correlated with maintenance during serial passage with wt RUB. We hypothesize that cluster formation and sustaining infected cell percentage increase the likelihood of co-infection by a DI and wt RUB during serial passage thus enhancing maintenance of the DI. Cluster formation and sustaining infected cell percentage were found to be due to a combination of attenuated cytopathogenicity of DIs that express the C-E1 fusion protein and cell-to-cell movement of the DI. In infected cells, the C-GFP-E1 fusion protein was localized to potentially novel vesicular structures that appear to originate from ER-Golgi transport vacuoles. This species of DI expressing a C-E1 fusion protein that exhibits attenuated cytopathogenicity and the ability to increase the number of infected cells through cell-to-cell movement could be the basis for development of an attractive vaccine vector.

Rubella virus-associated uveitis in a nonvaccinated child

PURPOSE

To report presumed Fuchs heterochromic uveitis (FHU) associated with Rubella virus (RV)-specific intraocular antibody production in a child who was not vaccinated against rubella.

DESIGN

Observational case report.

METHODS

We examined a 13-year-old boy with chronic anterior uveitis complicated by mature cataract. Two aqueous humor (AH) samples taken with an interval of four weeks were analyzed for intraocular antibody production against RV by calculation of the Goldmann-Witmer coefficient.

RESULTS

The patient showed all the clinical signs for FHU: iris atrophy, stellate keratic precipitates, and cataract. Analysis of the AH demonstrated intraocular antibody production against RV in two sequential samples.

CONCLUSIONS

The data show that RV-associated uveitis can already present during childhood. Moreover, this finding suggests that nonvaccinated children may be at risk to develop uveitis after RV infection.

Potency estimation of measles, mumps and rubella trivalent vaccines with quantitative PCR infectivity assay

The quantitative PCR infectivity assay is a combination of virus propagation and quantitative PCR. Previously [Schalk JAC, van den Elzen C, Ovelgonne H, Baas C, Jongen PMJM. Estimation of the number of infectious measles viruses in live virus vaccines using quantitative real-time PCR. J Virol Methods 2004;117:179-87.], we used this assay to estimate the titer of infectious measles virus in trivalent, live, measles, mumps, rubella vaccines (MMR). Here we describe the further improvement and development of the assay for simultaneous potency estimation of measles, mumps and rubella viruses. The potency of measles and mumps virus is estimated within one assay after 1 day of cell culture. The potency of rubella virus is estimated in a separate assay after 2 days of cell culture. Compared to conventional CCID50 and plaque assays, the quantitative PCR infectivity assay has the advantage in being fast because the assay is not dependent on the formation of cytopathic effect. Furthermore assay design is simplified: serological neutralization can be omitted because PCR is virus-specific and, under the conditions used, the individual components of trivalent measles, mumps, rubella vaccines do not interfere with each other. The assay was validated and compared to the performance of a plaque assay.

Effects of endocytosis inhibitory drugs on rubella virus entry into VeroE6 cells

It has been suggested that infectious entry of rubella virus (RV) is conducted by receptor mediated endocytosis. To explore the cellular entry mechanism of RV, inhibitory effects of drugs affecting various endocytic pathways on RV entry into VeroE6 cells were analyzed. Results showed that RV infectious entry into VeroE6 cells is mediated by clathrin-dependent endocytosis and not by caveolae-mediated endocytosis. Moreover, chemical inhibition of macropinocytosis such as treatments of amiloride, actin and microtubule-disrupting drug significantly reduced RV infection. Considering that macropinocytosis is inducible endocytosis by cellular stimulations, clathrin-mediated endocytosis is likely to be a major route of RV infectious entry.

Rubella virus and birth defects: Molecular insights into the viral teratogenesis at the cellular level

BACKGROUND

In utero rubella virus (RV) infection of a fetus can result in birth defects that are often collectively referred to as congenital rubella syndrome (CRS). In extreme cases, fetal death can occur. In spite of the availability of a safe and effective vaccine against rubella, recent worldwide estimates are that more than 100,000 infants are born with CRS annually.

RECENT PROGRESS

Recently, several significant findings in the field of cell biology, as well as in the RV replication and virus-cell interactions, have originated from the authors' laboratory, and other researchers have provided insights into RV teratogenesis. It has been shown that 1) an RV protein induces cell-cycle arrest by generating a subpopulation of tetraploid nuclei (i.e., 4N DNA) cells, perhaps representative of the tetraploid state following S phase in the cell cycle, due to its interaction with citron-K kinase (CK); 2) RV infection induces apoptosis in cell culture, and 3) CK functional perturbations lead to tetraploidy, followed by apoptosis, in specific cell types.

CONCLUSIONS

Based on several similarities between known RV-associated fetal and cellular manifestations and CK deficiency-associated phenotypes, it is reasonable to postulate that P90-CK interaction in RV-infected cells interferes with CK function and induces cell-cycle arrest following S phase in a subpopulation, perhaps representative of tetraploid stage, which could lead to subsequent apoptosis in RV infection. Taking all these observations to the fetal organogenesis level, it is plausible that P90-CK interaction could perhaps be one of the initial steps in RV infection-induced apoptosis-associated fetal birth defects in utero.

Rubella virus capsid protein modulates viral genome replication and virus infectivity

The structural proteins (SP) of the Togaviridae can be deleted in defective interfering RNAs. The dispensability of viral SP has allowed construction of noninfectious viral expression vectors and replicons from viruses of the Alphavirus and Rubivirus genera. Nevertheless, in this study, we found that the SP of rubella virus (RUB) could enhance expression of reporter genes from RUB replicons in trans. SP enhancement required capsid protein (CP) expression and was not due to RNA-RNA recombination. Accumulation of minus- and plus-strand RNAs from replicons was observed in the presence of SP, suggesting that SP specifically affects RNA synthesis. By using replicons containing an antibiotic resistance gene, we found 2- to 50-fold increases in the number of cells surviving selection in the presence of SP. The increases depended significantly on the amount of transfected RNA. Small amounts of RNA or templates that replicated inefficiently showed more enhancement. The infectivity of infectious RNA was increased by at least 10-fold in cells expressing CP. Moreover, virus infectivity was greatly enhanced in such cells. In other cells that expressed higher levels of CP, RNA replication of replicons was inhibited. Thus, depending on conditions, CP can markedly enhance or inhibit RUB RNA replication.

Characteristics and mechanisms of isolated rubella virus, strain JR23: infection of the central nervous system of BALB/c mice

OBJECTIVE

To investigate the correlation between rubella virus (RuV) antigen in peripheral lymphocytes, the immune status and RuV infection in the central nervous system (CNS).

METHODS

BALB/c mice were used as a model and treated with immunoaffecting medicines. Then, the mice were infected with RuV via the abdominal cavity, and the antigen level in peripheral lymphocytes was examined 1, 3, 7 and 14 days postinfection. RuV in the CNS was detected by immunohistochemical methods. BALB/c mice were given dexamethasone and cytoxan before infection with the RuV JR23 strain. Immune functions and RuV invasion of the CNS were assayed on day 21 postinfection via the abdominal cavity, and their relationship was analyzed.

RESULTS

The mean antigen detection rates at different times were 3.1, 4.1, 9.6 and 2.4%, respectively, in the dexamethasone group, and 14.2, 12.7, 9.9 and 3.1%, respectively, in the cytoxan group. In the group without any intervention, the detection rates were 4.63, 10.25, 6.88 and 1.75%, respectively. The antigen detection rates in peripheral lymphocytes among the three groups 24 h postinfection were significantly different (F = 0.0317, p < 0.05). Comparisons between groups showed that antigen detection rates in the cytoxan group were much higher than those in other groups, but there was no difference between the dexamethasone and control groups. The animals with persistent presence of antigen were much more susceptible to cerebral infection than those with short-term presence (p < 0.001). T cell functions of the cytoxan group were significantly lower than those of other groups (p < 0.05), as detected by the MTT method. Infection rates of the dexamethasone, cytoxan and control groups were 60, 90 and 50%, respectively. Cell immune functions of the mice with CNS infection were obviously worse than those of the mice without CNS infection (p < 0.001). RuV-specific antibodies were assayed in all groups by ELISA and the results showed that there were no significant differences among groups (p < 0.05) or between the groups with and without CNS infection.

CONCLUSION

Cytoxan can affect virus detection rates in peripheral lymphocytes. At the early phase of infection, the persistent presence of RuV in peripheral lymphocytes increases the incidence of CNS infection. RuV infection in the CNS was related to the cell immune situation before specific antibody was produced in the body.

Time-course induction of apoptosis by wild-type and attenuated strains of rubella virus

The time-course of rubella virus (RV)-induced apoptosis was studied in RK13 cells. DEVD-specific caspase activity assay and Western blotting for caspase-3 were used to determine the time-course of caspase activation and demonstrated that RV-induced apoptotic changes occur as early as 12 h post-infection (p.i.). Caspase activity followed a cyclic pattern, as seen with apoptotic-inducing drugs, with maximum activity detected at 72 h p.i. Apoptosis caused by wild-type (RN) and attenuated vaccine (Cendehill) strains of RV was compared by TUNEL staining, counting dead floating cells and DNA fragmentation analysis. Although the amount of apoptosis due to the wild-type strain was marginally greater, this was probably due to its faster growth rate.

Apoptosis induction by the infection with Gilchrist strain of rubella virus

Apoptosis is an active process of cellular self-destruction, which can be initiated in response to several stimuli such as toxic substances, hormones, cytokines, trophic or osmotic modifications and viral infections. In this study, we demonstrate that in vitro rubella-virus (RV) induced cell death exhibited properties of apoptosis, characterized by condensation and segmentation of nuclei and internucleosomal cleavage of nuclear DNA. Apoptosis was not seen in the cells absorbed with UV-inactivated virus, indicating that the viral replication is required for the induction of apoptosis. Our results suggest that most of the cells undergoing apoptosis are non-infected neighboring cells.

Effect of site-directed asparagine to isoleucine substitutions at the N-linked E1 glycosylation sites on rubella virus viability

The role of three N-linked glycosylation sites in rubella virus (RV) E1 protein on virion release was analyzed by transfecting Vero 76 cells with infectious RV RNA (Robo302WT) containing isoleucine substitutions at N76, N177, and N209 (individually and in combinations). RV RNAs were detected and found to retain substitutions in the transfected cells, but RV capsid indicative of infection was undetectable, except for in Robo302WT and Robo302-N177I transfected cells. Only culture supernatants of Robo302WT and Robo302-N177I RNA transfected cells were positive for RV, suggestive of the virion release into the culture medium. Further, detection of intracellular RV E1 and newly released virion-associated E1 was possible only from cells previously incubated with Robo302-N177I and Robo302WT culture supernatants, suggesting that N177I substituted virus retained infectivity. These results suggest that while glycosylation at N177 is not critical, N76I and N209I mutations are lethal to RV viability.

Antibodies directed against rubella virus induce demyelination in aggregating rat brain cell cultures

To link the presence of intrathecal virus-specific oligoclonal immunoglobulin G (IgG) in multiple sclerosis patients to a demyelinating activity, aggregating rat brain cell cultures were treated with antibodies directed against two viruses, namely, rubella (RV) and hepatitis B (HB). Anti-RV antibodies in the presence of complement decreased myelin basic protein concentrations in a dose-dependent manner, whereas anti-HB antibodies had no effect. A similar but less pronounced effect was observed on the enzymatic activity of 2',3'-cyclic nucleotide 3'-phosphohydrolase, which is enriched in noncompact membranes of oligodendrocytes. These effects were comparable to those in cultures treated with antibodies directed against myelin oligodendrocyte glycoprotein (MOG), previously found to be myelinotoxic both in vitro and in vivo. Sequence homologies were found between structural glycoprotein E(2) of RV and MOG, suggesting that demyelination was due to molecular mimicry. To support the hypothesis that demyelination was caused by anti-RV IgG that recognized an MOG epitope, we found that anti-RV antibodies depleted MOG in a dose-dependent manner. Further evidence came from the demonstration that anti-RV and anti-MOG IgG colocalized on oligodendrocyte processes and that both revealed by Western blot a 28 kDa protein in CNS myelin, a molecular weight corresponding to MOG. These findings suggest that a virus such as RV exhibiting molecular mimicry with MOG can trigger an autoimmune demyelination.