Development of a real-time fluorescent reverse transcription loop-mediated isothermal amplification assay with quenching primers for rapid detection of rubella virus.

Rubella virus infection during early pregnancy sometimes causes severe birth defects termed congenital rubella syndrome. Although there are safe and effective live-attenuated vaccines, rubella has only been certified as eliminated in the Americas within the six World Health Organization regions. Rubella remains an endemic disease in many regions, and outbreaks occur wherever population immunity is insufficient. There are two main methods for diagnosis of rubella: detection of anti-rubella IgM antibodies by enzyme immunoassay and detection of the viral genome by real-time RT-PCR. Both of these methods require substantial time and effort. In the present study, a rapid rubella detection assay using real-time fluorescent reverse transcription loop-mediated isothermal amplification with quenching primers was developed. The time required for the new assay was one-half that required for a real-time RT-PCR assay. The assay had 93.6% positive percent agreement and 100% negative percent agreement for clinical specimens compared with the real-time RT-PCR assay. The new assay is considered useful for diagnosis of rubella in areas where rubella is endemic.

Progress Toward Rubella Elimination - World Health Organization European Region, 2005-2019.

In 2005, the Regional Committee of the World Health Organization (WHO) European Region (EUR) passed a resolution calling for the regional elimination of measles, rubella, and congenital rubella syndrome (CRS) (1). In 2010, all 53 countries in EUR* reaffirmed their commitment to eliminating measles, rubella, and CRS (2); this goal was included in the European Vaccine Action Plan 2015-2020 (3,4). Rubella, which typically manifests as a mild febrile rash illness, is the leading vaccine-preventable cause of birth defects. Rubella infection during pregnancy can result in miscarriage, fetal death, or a constellation of malformations known as CRS, which usually includes one or more visual, auditory, or cardiac defects (5). The WHO-recommended measles and rubella elimination strategies in EUR include 1) achieving and maintaining ≥95% coverage with 2 doses of measles- and rubella-containing vaccine (MRCV) through routine immunization services; 2) providing measles and rubella vaccination opportunities, including supplementary immunization activities (SIAs), to populations susceptible to measles or rubella; 3) strengthening surveillance by conducting case investigations and confirming suspected cases and outbreaks with laboratory results; and 4) improving the availability and use of evidence to clearly communicate the benefits and risks of preventing these diseases through vaccination to health professionals and the public (6). This report updates a previous report and describes progress toward rubella and CRS elimination in EUR during 2005-2019 (7). In 2000, estimated coverage with the first dose of a rubella-containing vaccine (RCV1) in EUR was 60%, and 621,039 rubella cases were reported (incidence = 716.9 per 1 million population). During 2005-2019, estimated regional coverage with RCV1 was 93%-95%, and in 2019, 31 (58%) countries achieved ≥95% coverage with the RCV1. During 2005-2019, approximately 38 million persons received an RCV during SIAs in 20 (37%) countries. Rubella incidence declined by >99%, from 234.9 cases per 1 million population (206,359 cases) in 2005 to 0.67 cases per 1 million population (620 cases) by 2019. CRS cases declined by 50%, from 16 cases in 2005 to eight cases in 2019. For rubella and CRS elimination in EUR to be achieved and maintained, measures are needed to strengthen immunization programs by ensuring high coverage with an RCV in every district of each country, offering supplementary rubella vaccination to susceptible adults, maintaining high-quality surveillance for rapid case detection and confirmation, and ensuring effective outbreak preparedness and response.

The period from prodromal fever onset to rash onset in laboratory-confirmed rubella cases: a cross-sectional study.

BACKGROUND: In resource-limited settings, where rubella is endemic, it is difficult to determine which sporadic case should be tested for rubella. The study aimed to provide useful evidence to help screen rubella cases for real-time reverse transcriptase-polymerase chain reaction (RT-PCR) examination for rubella in resource-limited settings. METHOD: Suspected rubella patients identified by a physician and brought to the notice of the Ryugasaki public health center or the Tsuchiura public health center were enrolled from April 2018 through December 2019. The inclusion criterion was a confirmed rubella diagnosis based on laboratory tests. We studied the distribution of the time from the onset of fever until the onset of rash. RESULTS: The study included 86 cases with simultaneous presentation of fever and rash. Twenty-nine cases had confirmed rubella based on the laboratory diagnosis. Among these, the time from the onset of fever until the onset of rash was limited to - 1 day to 2 days. The number of rubella cases was the highest when the onset of rash was on the following day of the onset of fever. Of the 78 patients who underwent the RT-PCR test, 48% tested positive for rubella among those with a time from the onset of fever to the onset of rash between - 1 day and 2 days (22 out of 46, 95% confidence interval 34-62%); no positive results (0 out of 30, 95% confidence interval - 14%) were seen in patients with a time from fever to rash onset ≥3 days. CONCLUSION: The period from the onset of fever to the onset of rash was limited to - 1 day to 2 days among confirmed rubella patients. If the period from onset of fever to the onset of rash was ≥3 days for a patient, the likelihood of rubella was low.

Study of the teratogenicity of the vaccine strain of the Rubella virus «Orlov-V¼ (Matonaviridae: Rubivirus: Rubella virus) in experience on rhesus macaques.

INTRODUCTION: Rubella virus has pronounced teratogenic properties that can cause generalized and persistent intrauterine infection of the fetus. As a result, the control of the loss of teratogenicity inherent in «wild-type¼ virus strains is a necessary stage of a preclinical study of the vaccine strain for a live attenuated rubella vaccine.The purpose of the study is to comprehensively study the teratogenic properties of the vaccine strain of rubella virus «Orlov-V¼ in the experiment on rhesus macaques. MATERIAL AND METHODS: Seronegative to rubella virus female rhesus macaques in early pregnancy at the age of 4-7 years (n = 13) were used in the experiment. Animals of the experimental group (n = 9) received single immunization intramuscularly with a preparation from the «Orlov-V¼ strain. The control group of the monkeys (n = 3) were immunized with a commercial vaccine containing Wistar RA27/3 strain. The female of the control group (n = 1) was injected with a solvent used in the rubella vaccine. Study of possible teratogenic properties of vaccine strains of rubella virus was carried out using a complex of clinical, immunological, pathomorphological and virological methods. Clinical observations were made within 3 months after the monkeys' birth. Determination of antibody titers in the blood serum of immunized monkeys was performed in HI test on the 28th-30th day after infection. The ELISA method was applied to determine IgM antibodies in the blood serum of newborns within the first month of life. Detection of rubella virus RNA was performed by PCR with electrophoretic detection of amplicons. RESULTS: No markers of congenital rubella infection were found in infants born from monkeys vaccinated during the pregnancy. It is shown that PCR can be an informative method to confirm the absence of teratogenic properties of vaccine strains of rubella virus. DISCUSSION: The obtained data demonstrated that vaccine strains of the «Orlov-V¼ rubella virus and Wistar RA27/3 have lost their teratogenic properties. The possibility of using an alternative strategy for preclinical assessment of specific safety of antiviral vaccines including a complex of clinical, immunological, pathologic and virological methods instead of the classical pathologic method is discussed. CONCLUSION: The results obtained in this study showed the absence of teratogenic properties and high immunogenic activity of the vaccine strain of rubella virus «Orlov-V¼.

Relatives of rubella virus in diverse mammals.

Since 1814, when rubella was first described, the origins of the disease and its causative agent, rubella virus (Matonaviridae: Rubivirus), have remained unclear1. Here we describe ruhugu virus and rustrela virus in Africa and Europe, respectively, which are, to our knowledge, the first known relatives of rubella virus. Ruhugu virus, which is the closest relative of rubella virus, was found in apparently healthy cyclops leaf-nosed bats (Hipposideros cyclops) in Uganda. Rustrela virus, which is an outgroup to the clade that comprises rubella and ruhugu viruses, was found in acutely encephalitic placental and marsupial animals at a zoo in Germany and in wild yellow-necked field mice (Apodemus flavicollis) at and near the zoo. Ruhugu and rustrela viruses share an identical genomic architecture with rubella virus2,3. The amino acid sequences of four putative B cell epitopes in the fusion (E1) protein of the rubella, ruhugu and rustrela viruses and two putative T cell epitopes in the capsid protein of the rubella and ruhugu viruses are moderately to highly conserved4-6. Modelling of E1 homotrimers in the post-fusion state predicts that ruhugu and rubella viruses have a similar capacity for fusion with the host-cell membrane5. Together, these findings show that some members of the family Matonaviridae can cross substantial barriers between host species and that rubella virus probably has a zoonotic origin. Our findings raise concerns about future zoonotic transmission of rubella-like viruses, but will facilitate comparative studies and animal models of rubella and congenital rubella syndrome.

Comparison of virological and serological methods for laboratory confirmation of rubella.

BACKGROUND: Work toward rubella elimination has accelerated globally. A reliable laboratory confirmation of rubella-suspected cases is required for effective surveillance in the rubella-elimination phase. The use of adequate specimens is a key to improving the quality of this surveillance. STUDY DESIGN: We conducted rubella virus (RUBV) isolation and RUBV genome or anti-RUBV IgM detection on 1023 specimens from 372 rubella- or measles-suspected cases collected through the national surveillance program in Sakai city of Osaka prefecture, Japan between 2011 and 2013. The resulting data were analyzed by specimen type, collection date, and immunological status. RESULTS: Among the three specimen types (throat swab, serum or plasma, and urine) collected through 10 days post-rash onset, the highest success rates for RUBV genome detection and RUBV isolation were obtained using throat swabs. In agreement with previous work, RUBV-specific IgM were undetectable in 50% of the rubella-confirmed cases until 3 days after rash onset. The success rates of RUBV genome detection and RUBV isolation declined in association with the appearance of RUBV-specific antibodies in blood, especially in serum, plasma, or urine samples. CONCLUSION: Throat swabs are the most optimal specimen types for both RUBV genome detection and RUBV isolation; serum/plasma samples may be suboptimal, especially for RUBV isolation. The findings from this study will provide useful information for improving laboratory surveillance for rubella in the elimination phase.

Seroprevalence of rubella virus antibodies among pregnant women in the Center and South-West regions of Cameroon.

Rubella infection in early pregnancy can lead to miscarriages, fetal death, or birth of an infant with congenital rubella syndrome (CRS). In Cameroon, like in many developing countries, rubella surveillance is not well-established. The aim of this study was to determine the prevalence of rubella virus specific antibodies among pregnant Cameroonians. We conducted a cross-sectional study for rubella infection among pregnant women attending antenatal clinics in the Center and South-West regions of Cameroon. Demographic data and blood were collected and tested for rubella specific antibodies (IgG and IgM), and for the IgM positive cases, IgG avidity and real time PCR was done. From December 2015 to July 2017, 522 serum samples were collected and tested from pregnant women. The seroprevalence of rubella specific IgG was 94.4%, presumably due to immunity induced by wild-type rubella virus. The seroprevalence of rubella specific IgM was 5.0%, possibly indicating rubella infection. However, IgG avidity testing of the IgM positive cases detected high avidity IgGs, ranging from 52.37% to 87.70%, indicating past rubella infection. 5.6% (29/522) of the participants had negative results for IgG to rubella virus, indicating susceptibility to rubella infection. None of the participants had received a rubella containing vaccine (RCV), but 51% (266/522) of the pregnant women lived in a house with a child with records of at least one dose of RCV. Rubella virus RNA was not detected in the urine of any IgM positive case. Findings from this study show that rubella infection is significant in Cameroon. Some pregnant women are still susceptible to rubella infection. For a better management of rubella infection in pregnancy in Cameroon, consideration should be taken to investigate for IgG-avidity test in cases with positive rubella IgM result to distinguish between recent from past rubella infection.

Rubella virus, Toxoplasma gondii and Treponema pallidum congenital infections among full term delivered women in an urban area of Tanzania: a call for improved antenatal care.

BACKGROUND: A significant proportion of newborns in the developing countries are born with congenital anomalies. OBJECTIVE: This study investigated congenital infections due to Rubella virus, Toxoplasma gondii, Treponema pallidum among presumed normal neonates from full term pregnant women in Mwanza, Tanzania. METHODS: Sera from mothers were tested for Treponema pallidum and Toxoplasma gondii infection while newborns from mothers with acute infections were tested for T. pallidum and T. gondii, and all newborns were tested for Rubella IgM antibodies. RESULTS: A total of 13/300 (4.3 %) mothers had T. pallidum antibodies with 3 of them having acute infection. Two (0.7 %) of the newborns from mothers with acute infection were confirmed to have congenital syphilis. Regarding toxoplasmosis, 92/300 (30.7 %) mothers were IgG seropositive and 7 had borderline positivity, with only 1/99 (1%) being IgM seropositive who delivered IgM seronegative neonate. Only 1/300 (0.3 %) newborn had rubella IgM antibodies indicating congenital rubella infection. CONCLUSION: Based on these results, it is estimated that in Mwanza city in every 100,000 live births about 300 and 600 newborns have congenital rubella and syphilis infections, respectively. Rubella virus and T. pallidum are likely to be among common causes of congenital infections in developing countries.

Infectious vaccine-derived rubella viruses emerge, persist, and evolve in cutaneous granulomas of children with primary immunodeficiencies.

Rubella viruses (RV) have been found in an association with granulomas in children with primary immune deficiencies (PID). Here, we report the recovery and characterization of infectious immunodeficiency-related vaccine-derived rubella viruses (iVDRV) from diagnostic skin biopsies of four patients. Sequence evolution within PID hosts was studied by comparison of the complete genomic sequences of the iVDRVs with the genome of the vaccine virus RA27/3. The degree of divergence of each iVDRV correlated with the duration of persistence indicating continuous intrahost evolution. The evolution rates for synonymous and nonsynonymous substitutions were estimated to be 5.7 x 10-3 subs/site/year and 8.9 x 10-4 subs/site/year, respectively. Mutational spectra and signatures indicated a major role for APOBEC cytidine deaminases and a secondary role for ADAR adenosine deaminases in generating diversity of iVDRVs. The distributions of mutations across the genes and 3D hotspots for amino acid substitutions in the E1 glycoprotein identified regions that may be under positive selective pressure. Quasispecies diversity was higher in granulomas than in recovered infectious iVDRVs. Growth properties of iVDRVs were assessed in WI-38 fibroblast cultures. None of the iVDRV isolates showed complete reversion to wild type phenotype but the replicative and persistence characteristics of iVDRVs were different from those of the RA27/3 vaccine strain, making predictions of iVDRV transmissibility and teratogenicity difficult. However, detection of iVDRV RNA in nasopharyngeal specimen and poor neutralization of some iVDRV strains by sera from vaccinated persons suggests possible public health risks associated with iVDRV carriers. Detection of IgM antibody to RV in sera of two out of three patients may be a marker of virus persistence, potentially useful for identifying patients with iVDRV before development of lesions. Studies of the evolutionary dynamics of iVDRV during persistence will contribute to development of infection control strategies and antiviral therapies.

Genetic Characterization of Measles and Rubella Viruses Detected Through Global Measles and Rubella Elimination Surveillance, 2016-2018.

All six World Health Organization (WHO) regions have established measles elimination goals, and three regions have a rubella elimination goal. Each region has established a regional verification commission to monitor progress toward measles elimination, rubella elimination, or both, and to provide verification of elimination* (1,2). To verify elimination, high-quality case-based surveillance is essential, including laboratory confirmation of suspected cases and genotyping of viruses from confirmed cases to track transmission pathways. In 2000, WHO established the Global Measles and Rubella Laboratory Network (GMRLN) to provide high-quality laboratory support for surveillance for measles, rubella, and congenital rubella syndrome (3). GMRLN is the largest globally coordinated laboratory network, with 704 laboratories supporting surveillance in 191 countries (4). This report updates a previous report and describes the genetic characterization of measles and rubella viruses during 2016-2018 (5). The genetic diversity of measles viruses (MeVs) and rubella viruses (RuVs) has decreased globally following implementation of measles and rubella elimination strategies. Among 10,857 MeV sequences reported to the global Measles Nucleotide Surveillance (MeaNS) database during 2016-2018, the number of MeV genotypes detected in ongoing transmission decreased from six in 2016 to four in 2018. Among the 1,296 RuV sequences submitted to the global Rubella Nucleotide Surveillance (RubeNS) database during the same period, the number of RuV genotypes detected decreased from five in 2016 to two in 2018. To strengthen laboratory surveillance for measles and rubella elimination, specimens should be collected from all confirmed cases for genotyping, and sequences from all wild-type measles and rubella viruses should be submitted to MeaNS and RubeNS in a timely manner.

Simultaneous and rapid detection method for measles and rubella using single-tube multiplex real-time quantitative RT-PCR.

Patients with measles or rubella infections manifest acute onset fever accompanying systemic exanthema, which are clinically difficult to be distinguish. Rapid diagnosis and differentiation of such epidemic viral diseases is essential to prevent outbreaks. We developed a single-tube multiplex real-time PCR assay for these indistinguishable viruses. We used previously-reported primer settings, with a slight modification of reporter dye, and applied to multiplex Taqman real-time PCR by cobas z480 (Roche Molecular Systems, Inc.). Consequently, the assay could detect 10 copies/10 µl of measles and rubella with coefficient of variations of 11.2% and 21.8%, respectively. Strengths of our methodology include simplicity of operation, short measurement time (2 h), uses of internal control (confirming a run of PCR), and quantitative measurement with high sensitivity. Both measles and rubella currently cause social outbreaks in Japan. We hope that our single-tube multiplex assay contributes to an early diagnosis, leading to an appropriate infection control measure and prevention of epidemics.

The risk factors of exposure to rubella among pregnant women in Zaria 2013.

INTRODUCTION: rubella virus usually causes a mild disease, but maternal infection early in pregnancy often leads to birth defects known as congenital rubella syndrome (CRS). Rubella remains poorly controlled in Africa despite being a vaccine preventable disease. The objective of this study was to determine the risk factor of expose of rubella and prevalence of rubella IgG antibodies among pregnant women in Zaria. The results of this study will provide data which may be used to advise the government of Kaduna State on the need to include rubella vaccine in the free routine immunization particularly for women of childbearing age. METHODS: a cross-sectional study was carried out. Pregnant women attending antenatal clinics from three different health facilities in Zaria. A questionnaire was administered, to determine the proportion of pregnant women vaccinated and the sera of these women were tested for rubella IgG antibody using commercially produced enzyme-linked immunosorbent assay (ELISA) Kit. Statistical variables were compared with univariate (frequencies) bivariate (chi- square), multivariate analyses (logistic regression). A p-value of < 0.05 was considered significantly associated at 95% confidence intervals. RESULTS: of the 246 pregnant women screened, 222 (90.2%) were positive for rubella IgG. Prevalence was highest 82/222 (36.9%) among age group 20-24 years. Those positive of those who had completed secondary school education were 104/222 (46.8%) A large number among those who tested positive with 197/222 (88.7%) were married. The Hausa tribe 155/222 (69.9%) had the highest positivity for rubella IgG. Only 2 (0.9%) women claimed to have received rubella vaccine and 159/222 (71.6%) women were seropositive for IgG among the unemployed group. CONCLUSION: the serological evidence of rubella virus is an indication that rubella is endemic in Nigeria. Nigeria should include rubella vaccination in the routine immunization exercise for women before they get pregnant to reduce the risk of CRS.

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.

Use of FTA Cards To Transport Throat Swabs and Oral Fluid Samples for Molecular Detection and Genotyping of Measles and Rubella Viruses.

The genetic characterization of measles viruses is an important tool for measles surveillance. Reverse cold chain requirements for the transportation of samples to reference laboratories are challenging in resource-limited settings. FTA cards facilitate the transport of virologic samples at ambient temperature as noninfectious material; however, the utility of FTA cards for the detection and genotyping of measles virus from clinical samples has not been evaluated. Throat swabs (TS) and oral fluid (OF) samples were collected from suspected measles cases in the Democratic Republic of the Congo. Virus detection (reverse transcription-quantitative real-time PCR [RT-qPCR]) and genotyping (endpoint RT-PCR) were compared for samples from 238 suspected cases; these samples were either transported using the reverse cold chain or at ambient temperature on FTA cards. Virus detection showed excellent positive agreement for OF samples compared to TS (95.3%; confidence interval [CI], 91.6 to 97.4), in contrast to 79.4% (CI, 73.5 to 84.3) for TS on FTA, and 85.5% (CI, 80.2 to 89.6) for OF on FTA compared to OF samples. Genotyping results obtained for a subset of samples indicated that 77.3% of all TS and 71.0% of OF samples would produce genotype information compared to 41.6% of TS and 41.3% of OF on FTA cards. Similar results were found for 16 measles-negative samples that were confirmed as rubella cases. Measles genotype B3 and rubella genotype 2B were detected. FTA cards have limited utility for virologic surveillance of sporadic cases of measles; however, they can be a useful tool for the expansion of virologic surveillance in countries where the reverse cold chain is not available.

Plasmonic gold chips for the diagnosis of Toxoplasma gondii, CMV, and rubella infections using saliva with serum detection precision.

Sampling the blood compartment by an invasive procedure such as phlebotomy is the most common approach used for diagnostic purposes. However, phlebotomy has several drawbacks including pain, vasovagal reactions, and anxiety. Therefore, alternative approaches should be tested to minimize patient's discomfort. Saliva is a reasonable compartment; when obtained, it generates little or no anxiety. We setup a multiplexed serology assay for detection of Toxoplasma gondii IgG and IgM, rubella IgG, and CMV IgG, in serum, whole blood, and saliva using novel plasmonic gold (pGOLD) chips. pGOLD test results in serum, whole blood, and saliva were compared with commercial kits test results in serum. One hundred twenty serum/saliva sets (Lyon) and 28 serum/whole blood/saliva sets (Nice) from France were tested. In serum and whole blood, sensitivity and specificity of multiplex T. gondii, CMV, and rubella IgG were 100% in pGOLD when compared to commercial test results in serum. In saliva, sensitivity and specificity for T. gondii and rubella IgG were 100%, and for CMV IgG, sensitivity and specificity were 92.9% and 100%, respectively, when compared to commercial test results in serum. We were also able to detect T. gondii IgM in saliva with sensitivity and specificity of 100% and 95.4%, respectively, when compared to serum test results. Serological testing by multiplex pGOLD assay for T. gondii, rubella, and CMV in saliva is reliable and likely to be more acceptable for systematic screening of pregnant women, newborn, and immunocompromised patients.

Antiviral immunity in chronic lymphocytic leukemia measured by anti-rubella antibody.

BACKGROUND: Chronic lymphocytic leukemia (CLL), the most common form of adult leukemia in Caucasian populations, is characterized by a decrease in anti-infective immunity. Clinical evidence of antiviral immunity decrease is the reactivation of herpes virus in the form of skin lesions. In Europe, rubella infection is common and creates lifelong persistence of IgG antibodies. OBJECTIVES: The aim of our study was to determine whether hemagglutination inhibition (HAI) rubella test can be used to determine antiviral immunity in CLL patients. MATERIAL AND METHODS: The titers of the HAI test against rubella were examined in a group of 26 healthy subjects, 7 subjects with herpes labialis infection and 56 patients with CLL, among which 9 patients were co-infected with herpes virus. RESULTS: Statistical tests have shown differences between groups and a significant decrease of the titers of the test in patients with CLL, compared with healthy persons and the herpes group compared with other persons. CONCLUSIONS: Our results indicate a significant decrease of antiviral immunity in patients with CLL and persons with herpes-type skin lesions. Simultaneously, relying on our previous studies, we also suggest that the result of this test may be an important indicator of antiviral immunity in patients with CLL.

Rubella Virus Strain-Associated Differences in the Induction of Oxidative Stress Are Independent of Their Interferon Activation.

Rubella virus (RV) infection impacts cellular metabolic activity in a complex manner with strain-specific nutritional requirements. Here we addressed whether this differential metabolic influence was associated with differences in oxidative stress induction and subsequently with innate immune response activation. The low passaged clinical isolates of RV examined in this study induced oxidative stress as validated through generation of the reactive oxygen species (ROS) cytoplasmic hydrogen peroxide and mitochondrial superoxide. The addition of the cytoplasmic and mitochondrial ROS scavengers N-acetyl-l-cysteine and MitoTEMPO, respectively, reduced RV-associated cytopathogenicity and caspase activation. While the degree of oxidative stress induction varied among RV clinical isolates, the level of innate immune response and interferon-stimulated gene activation was comparable. The type III IFNs were highly upregulated in all cell culture systems tested. However, only pre-stimulation with IFN ß slightly reduced RV replication indicating that RV appears to have evolved the ability to counteract innate immune response mechanisms. Through the data presented, we showed that the ability of RV to induce oxidative stress was independent of its capacity to stimulate and counteract the intrinsic innate immune response.