The isolation of enteroviruses from blood: a comparison of four processing methods

Detection of enterovirus RNA in peripheral blood mononuclear cells correlates with the presence of the predisposing allele of the type 1 diabetes risk gene IFIH1 and with disease stage

AIMS/HYPOTHESIS

Enteroviral infection has been implicated consistently as a key environmental factor correlating with the appearance of autoimmunity and/or the presence of overt type 1 diabetes, in which pancreatic insulin-producing beta cells are destroyed by an autoimmune response. Genetic predisposition through variation in the type 1 diabetes risk gene IFIH1 (interferon induced with helicase C domain 1), which encodes the viral pattern-recognition receptor melanoma differentiation-associated protein 5 (MDA5), supports a potential link between enterovirus infection and type 1 diabetes.

METHODS

We used molecular techniques to detect enterovirus RNA in peripheral blood samples (in separated cellular compartments or plasma) from two cohorts comprising 79 children or 72 adults that include individuals with and without type 1 diabetes who had multiple autoantibodies. We also used immunohistochemistry to detect the enteroviral protein VP1 in the pancreatic islets of post-mortem donors (n=43) with type 1 diabetes.

RESULTS

We observed enhanced detection sensitivity when sampling the cellular compartment compared with the non-cellular compartment of peripheral blood (OR 21.69; 95% CI 3.64, 229.20; p<0.0001). In addition, we show that children with autoimmunity are more likely to test positive for enterovirus RNA than those without autoimmunity (OR 11.60; 95% CI 1.89, 126.90; p=0.0065). Furthermore, we found that individuals carrying the predisposing allele (946Thr) of the common variant in IFIH1 (rs1990760, Thr946Ala) are more likely to test positive for enterovirus in peripheral blood (OR 3.07; 95% CI 1.02, 8.58; p=0.045). In contrast, using immunohistochemistry, there was no correlation between the common variant in IFIH1 and detection of enteroviral VP1 protein in the pancreatic islets of donors with type 1 diabetes.

CONCLUSIONS/INTERPRETATION

Our data indicate that, in peripheral blood, antigen-presenting cells are the predominant source of enterovirus infection, and that infection is correlated with disease stage and genetic predisposition, thereby supporting a role for enterovirus infection prior to disease onset.

Immunology in the clinic review series; focus on type 1 diabetes and viruses: the enterovirus link to type 1 diabetes: critical review of human studies

The hypothesis that under some circumstances enteroviral infections can lead to type 1 diabetes (T1D) was proposed several decades ago, based initially on evidence from animal studies and sero-epidemiology. Subsequently, enterovirus RNA has been detected more frequently in serum of patients than in control subjects, but such studies are susceptible to selection bias and reverse causality. Here, we review critically recent evidence from human studies, focusing on longitudinal studies with potential to demonstrate temporal association. Among seven longitudinal birth cohort studies, the evidence that enterovirus infections predict islet autoimmunity is quite inconsistent in our interpretation, due partially, perhaps, to heterogeneity in study design and a limited number of subjects studied. An association between enterovirus and rapid progression from autoimmunity to T1D was reported by one longitudinal study, but although consistent with evidence from animal models, this novel observation awaits replication. It is possible that a potential association with initiation and/or progression of islet autoimmunity can be ascribed to a subgroup of the many enterovirus serotypes, but this has still not been investigated properly. There is a need for larger studies with frequent sample intervals and collection of specimens of sufficient quality and quantity for detailed characterization of enterovirus. More research into the molecular epidemiology of enteroviruses and enterovirus immunity in human populations is also warranted. Ultimately, this knowledge may be used to devise strategies to reduce the risk of T1D in humans.

Human febrile illness caused by encephalomyocarditis virus infection, Peru

Encephalomyocarditis virus was identified in the serum of 2 febrile patients in Peru.

Etiologic studies of acute febrile disease were conducted in sites across South America, including Cusco and Iquitos, Peru. Patients’ clinical signs and symptoms were recorded, and acute- and convalescent-phase serum samples were obtained for serologic examination and virus isolation in Vero E6 and C6/36 cells. Virus isolated in Vero E6 cells was identified as encephalomyocarditis virus (EMCV) by electron microscopy and by subsequent molecular diagnostic testing of samples from 2 febrile patients with nausea, headache, and dyspnea. The virus was recovered from acute-phase serum samples from both case-patients and identified with cardiovirus-specific reverse transcription–PCR and sequencing. Serum samples from case-patient 1 showed cardiovirus antibody by immunoglobulin M ELISA (acute phase <8, convalescent phase >1,024) and by neutralization assay (acute phase <10, convalescent phase >1,280). Serum samples from case-patient 2 did not contain antibodies detectable by either assay. Detection of virus in serum strongly supports a role for EMCV in human infection and febrile illness.

Diagnosis of Enteroviral Meningitis by Use of Polymerase Chain Reaction of Cerebrospinal Fluid, Stool, and Serum Specimens

BACKGROUND

Because enteroviruses can be detected in various clinical samples during enteroviral meningitis, we analyzed the combined diagnostic utility of polymerase chain reaction (PCR) of cerebrospinal fluid (CSF), feces, and serum for detection of enterovirus in specimens obtained from adults with aseptic meningitis or encephalitis.

METHODS

PCR results were analyzed for 34 adults for whom enteroviral meningitis was diagnosed on the basis of virus isolation and antibody detection in our hospital during 1999-2003. PCR results were also analyzed for 77 adults with meningitis or encephalitis of another defined cause for whom this assay was used for diagnostic evaluation during that period.

RESULTS

Twenty-six (76%) of 34 CSF samples and 24 (96%) of 25 fecal samples collected from patients with enteroviral meningitis had positive PCR results. The diagnostic yield of the test was lower for CSF specimens obtained >2 days after clinical onset, compared with CSF collected < or =2 days after onset. Instead, PCR of feces was highly useful also later, because 12 of the 13 fecal specimens obtained 5-16 days after clinical onset had positive test results. None of 75 CSF samples and 2 of 48 fecal samples obtained from patients with nonenteroviral infection had positive PCR results. All serum samples were PCR negative.

CONCLUSIONS

PCR of fecal specimens obtained throughout the course of enteroviral meningitis had the highest clinical sensitivity for detecting enterovirus. It is recommended that, in addition to performance of CSF PCR, fecal samples collected from patients with suspected enteroviral meningitis should be tested by PCR, especially when the duration of symptoms is >2 days.

Early and rapid detection of enterovirus 71 infection by an IgM-capture ELISA

Enterovirus 71 infection is more likely to induce severe complications and mortality than other enteroviruses. Laboratory diagnosis of enterovirus 71 in Taiwan still relies mainly on conventional virus isolation techniques that often require 5-10 days to obtain a result, thus hindering seriously the subsequent treatment and disease control measures. This study was to find a better alternative by developing a rapid enterovirus 71 detecting procedure, which can afford an earlier diagnosis and a more rapid outcome. In this study, an enterovirus 71-IgM-capture enzyme-linked immunosorbent assay (ELISA) was designed and tested with a total of 336 serum specimens collected from 236 cases of reported enterovirus infection with complications. Using virus isolation and neutralization test as standards, the sensitivity and specificity of the new protocol were 97.7 and 93.3%, respectively. Most of the IgM positive serum specimens were collected within 7 days after the onset of symptoms, while it appeared detectable up to 94 days after the onset of symptoms. Apart from being highly sensitive, rapid and low in cost, the new IgM-capture ELISA is sufficiently accurate to provide also reliable results for early detection of the virus. With this protocol, enterovirus 71 infections can be detected within 4h.

Human antibodies isolated from plasma by affinity chromatography increase the coxsackievirus B4-induced synthesis of interferon-alpha by human peripheral blood mononuclear cells in vitro

Coxsackievirus B4 (CVB4) can be found in circulating blood of patients; however, the interaction of CVB4 with peripheral blood mononuclear cells (PBMCs) is poorly understood. CVB4 induced low levels of IFN-alpha synthesis in PBMCs from healthy donors. In contrast, preincubation of infectious CVB4 with plasma from these donors containing anti-CVB4 antibodies strongly enhanced the synthesis of IFN-alpha. IgG obtained from plasma by chromatography formed immune complexes with CVB4 and increased significantly the CVB4-induced production of IFN-alpha by PBMCs. These antibodies did not have a neutralizing effect on CVB4 infection of Hep-2 cells. The role of CVB and adenovirus receptor (CAR), FcgammaRII and FcgammaRIII in the increased synthesis of IFN-alpha induced by CVB4 preincubated with IgG was shown by inhibition with specific antibodies. The major interferon-alpha-producing cells in response to CVB4-IgG complexes were CD14(+) cells and monocyte-enriched PBMCs. With the latter, detection of IFN-alpha by immunostaining was positive whereas in monocyte-depleted PBMCs it was not. This study shows that CVB4-induced synthesis of IFN-alpha by PBMCs can be enhanced by an antibody-dependent mechanism through interactions between the virus, non-neutralizing antivirus antibodies, FcgammaRII and III and CAR.

Postpericardiotomy syndrome: no evidence for a viral etiology

BACKGROUND

Postpericardiotomy syndrome has been considered a disorder induced by viral infection. This conclusion is based on serologic criterions, but these may be unreliable following either cardiopulmonary bypass or transfusion therapy. Previous studies have not verified the proposed etiology either by isolation of viruses, or by detection of their genome. We sought, therefore, to clarify the role, if any, of viruses in this syndrome.

METHODS AND RESULTS

We studied prospectively 149 children aged from 6 months to 16 years who were undergoing open heart surgery. Blood samples were collected from all prior to operation, and again 7 to 10 days post-operatively, and 47 were sampled at the time of development of symptoms of pericardial involvement. Serums were analyzed for the presence of IgM and IgG antibodies to cytomegalovirus, herpes simplex virus, and Epstein-Barr virus. The polymerase chain reaction was used for amplification when assessing the genome of the enteroviruses. Cultures for viruses were established on samples of stool, urine, and throat swabs collected 7 days post-operatively, and at the time of postpericardial symptoms. Pericardial fluid obtained from 5 patients with the syndrome was cultured for viruses, and tested for enterovirus genome. On the basis of clinical and echocardiographic findings, 34 children were determined to have definite evidence of the syndrome, 13 were considered to have possible evidence, and the results from these patients were compared to those from patients with no pericardial symptoms, the latter being matched for age and transfusion status. We isolated viruses from one or more sites in five patients with definite evidence (16%), from one (9%) of those with possible evidence, and from seven (19%) of the controls. All serums and pericardial samples were negative for enterovirus genome. IgM antibodies were found in only 5 patients, three with symptoms of pericardial involvement and two without. Rates of seroconversion to IgG for the viruses were lower in the patients with symptoms of pericardial involvement compared to controls, but were strongly influenced by transfusion status.

CONCLUSION

Our study has provided no evidence to support a viral etiology for the postpericardiotomy syndrome.

Comparison of use of cerebrospinal fluid, serum, and throat swab specimens in diagnosis of enteroviral acute neurological infection by a rapid RNA detection PCR assay

A PCR assay for detection of enterovirus RNA in multiple specimen types from patients with neurological infections was evaluated. Combined PCR assay of cerebrospinal fluid and serum (systemic specimens) was more sensitive than assaying either specimen alone in children but not in adults. Compared with PCR in systemic specimens, detection of enterovirus RNA in throat swabs showed a sensitivity of 62.5% and a specificity of 75.6%.

Molecular typing of enteroviruses: current status and future requirements. The European Union Concerted Action on Virus Meningitis and Encephalitis

Human enteroviruses have traditionally been typed according to neutralization serotype. This procedure is limited by the difficulty in culturing some enteroviruses, the availability of antisera for serotyping, and the cost and technical complexity of serotyping procedures. Furthermore, the impact of information derived from enterovirus serotyping is generally perceived to be low. Enteroviruses are now increasingly being detected by PCR rather than by culture. Classical typing methods will therefore no longer be possible in most instances. An alternative means of enterovirus typing, employing PCR in conjunction with molecular genetic techniques such as nucleotide sequencing or nucleic acid hybridization, would complement molecular diagnosis, may overcome some of the problems associated with serotyping, and would provide additional information regarding the epidemiology and biological properties of enteroviruses. We argue the case for developing a molecular typing system, discuss the genetic basis of such a system, review the literature describing attempts to identify or classify enteroviruses by molecular methods, and suggest ways in which the goal of molecular typing may be realized.

Clinical utility of the polymerase chain reaction for diagnosis of enteroviral meningitis in infancy

OBJECTIVE

To determine the utility of polymerase chain reaction (PCR) assay of cerebrospinal fluid (CSF), serum, and urine for rapid diagnosis of enteroviral meningitis in infants 3 months of age and younger.

STUDY DESIGN

We identified prospectively infants 3 months of age and younger coming to the emergency department with fever whose examination included a lumbar puncture, blood culture, or both. Samples of CSF, serum, urine, throat, and stool specimens were collected for viral culture and, with the exception of stool, for PCR assay. Those infants who had not received prior antibiotic therapy and had sterile bacterial cultures of CSF, blood, and urine were selected for the present analysis.

RESULTS

A total of 259 specimens for viral culture and 203 specimens for PCR assay were collected from 64 infants. Comparison of results of PCR assay of CSF with viral culture, the gold standard for diagnosis of enteroviral meningitis, demonstrated a sensitivity of 100% and a specificity of 90%. Because enteroviruses are not always detectable by culture, the following modified standard was established to define enteroviral meningitis: either CSF pleocytosis, sterile bacterial cultures and detection of an enterovirus in stool culture or positive viral culture of CSF, or both. With this modified definition, the sensitivity and specificity of the PCR assay of CSF were 92% and 94%, respectively. PCR assay of serum and urine offered no benefit over PCR assay of CSF alone for diagnosis of meningitis.

CONCLUSION

PCR assay of CSF is useful for the rapid and reliable diagnosis of enteroviral meningitis. Application of this technique in the clinical setting can potentially diminish unnecessary hospitalization and use of antibiotics.

Detection of enteroviral RNA by a new single-step PCR

In this study we present a modified diagnostic routine PCR (polymerase chain reaction) technique for the detection of specific enteroviral nucleic acid sequences in human body fluids, the use of which would reduce the number of false-positive results, the costs and the concentration of reagents required in PCR. Cerebrospinal samples, pharyngeal swabs and faeces were tested. To this end, general primers, selected in the highly conserved 5' non-coding region were used, with a closed-tube RT semi-nested PCR protocol, and the PCR product was analysed using a hybridization in solid phase. A total of 32 patients with suspected enteroviral infection, 17 with suspected viral meningitis and 15 with a possible acute enteroviral infection different from meningitis were analysed, and 80% of the patients with possible acute enteroviral infection were PCR-positive. A broad range of enteroviruses can be detected and false-positive results can be reduced. The availability of results in less than 12 h and the lack of need for radiolabelled probes also increase the convenience of this protocol.

Susceptibility of human bone marrow cells and hematopoietic cell lines to coxsackievirus B3 infection

Viremia is commonly observed in association with enterovirus infections, and during this phase viruses can be transmitted to secondary target organs in the body. It is not known, however, whether blood cells play a role in the pathogenesis of enterovirus infection supporting virus replication. Our earlier work (T. Vuorinen, R. Vainionpää, H. Kettinen, and T. Hyypiä, Blood 84:823-829, 1994) demonstrated that coxsackievirus B3 is able to replicate in representatives of B- and T-cell lines but not in a monocytic cell line or peripheral blood mononuclear cells, indicating that virus replication may depend on the differentiation and maturation stages of the cells. Therefore, we have broaden our studies and analyzed the susceptibility of granulocyte-macrophage CFU and hematopoietic cell lines with various differentiation and maturation stages to coxsackievirus B3 infection. Virus replication was detected in B- and T-cell lines with no direct correlation to the maturation stage. Granulocyte-macrophage CFU were also able to support virus multiplication.

PCR for the diagnosis of enteroviral meningitis

A 2-step 'semi-nested' enterovirus PCR was developed and applied to CSF and serum specimens from 27 consecutive patients with aseptic meningitis. CSF and sera from 8 patients with non-enteroviral diagnoses were included as negative clinical controls. Enterovirus RNA was detected in CSF by PCR in 15 of the patients with aseptic meningitis, compared with 6 by virus culture. Acute-phase sera proved positive for enterovirus RNA in 11 patients, thus increasing the number of PCR-positive patients to 18. Convalescent-phase sera were all negative by PCR. The correlation of a positive or negative PCR result in CSF and/or serum versus combined conventional virology (serology and isolation from 1-3 sites, i.e. CSF, stool and throat) was 78%. All negative controls were negative by PCR. PCR is a reliable and sensitive diagnostic tool for the detection of enteroviral infections. Both CSF and acute-phase serum should be considered for testing.

Search for Coxsackievirus B3 RNA in idiopathic dilated cardiomyopathy using gene amplification by polymerase chain reaction

A polymerase chain reaction (PCR) amplification assay was developed to detect Coxsackievirus B3 ribonucleic acid (RNA) in blood and myocardial tissue of explanted hearts from 40 patients who underwent cardiac transplantation and in 1 normal heart. Twenty-one patients were affected by idiopathic dilated cardiomyopathy of different duration and 19 by coronary artery disease. Coxsackievirus B3 in vitro infected Vero cells and cells infected by related human enteroviruses (Coxsackievirus B2, B4, and poliovirus 1) were used as reaction controls. PCR was performed using 4 pairs of primers homologous to Coxsackie-virus B3 sequences. Three sets were located in regions of the genome conserved at nucleotide level between several enterovirus species (replicase gene, 5' noncoding region), while one was located in a Coxsackievirus B3-specific region (VP1 gene). Total RNA was prepared by acid guanidinium isothiocyanate extraction from tissue stored frozen at -80 degrees C. One microgram of total RNA was retrotranscribed with either antisense primer or with random hexanucleotide primers and then subjected to 40 cycles of amplification. PCR products were separated by electrophoresis on a 10% polyacrylamide gel, electrotransferred to a nylon membrane and then hybridized to oligonucleotide probes specific for the coxsackievirus B3 genome radiolabeled with radioactive isotope of phosphorous. All pairs of primers yielded specific amplification products when tested on Coxsackievirus B3-infected Vero cells, with a sensitivity of 1 infected cell out of 10(5) to 10(6) cells starting from 1 microgram total RNA. Primer sets for regions of Coxsackievirus B3 genome highly conserved between related enteroviral species gave positive amplification also when challenged with RNA from cells infected by Coxsackievirus B2, B4 and poliovirus 1.

Two-step PCR in the retrospective diagnosis of enteroviral viraemia

Enteroviral infections are potentially serious in man causing a variety of syndromes and a viraemic phase is probable in most patients. However, virological diagnosis is usually indirect by isolation of the agent from throat or stools when possible, and/or slow due to the need to titrate antibodies in paired sera. Because of its high sensitivity the polymerase chain reaction (PCR) offers the possibility of rapid detection of even low-grade viraemia. We have developed a 2-step PCR procedure adapted for enteroviruses and applied it to stored sera from patients with enteroviral meningitis. The acute sera from 7/12 patients were positive but the 4 convalescence sera tested, 2 of which had been positive at the acute phase, were negative. The assay should now be tested prospectively on serum and cerebrospinal fluid and could be developed for routine diagnosis.

Epidemiology and laboratory diagnosis of infection with viral and bacterial pathogens in infants hospitalized for suspected sepsis

A prospective study was conducted to determine the frequency and distribution of bacterial and viral pathogens in infants hospitalized with suspected sepsis and to evaluate the potential of virus detection for improving patient management. A causative organism was detected in 157 (67%) of 233 previously healthy infants less than 3 months of age, who had been hospitalized for suspected sepsis: 19 (8%) had bacterial infections, 135 (58%) had viral infections, and 3 (1%) had mixed viral-bacterial infections. Viral infections occurred in a seasonal pattern: enteroviruses were responsible for most of the hospitalizations during summer and fall (65/110; 63%) and respiratory syncytial and influenza A viruses were responsible for most of the infections during winter (44/81; 55%). In contrast, bacterial infections were not seasonally distributed. Virus was detected in 33% of the 138 infected infants within 24 hours, and in 64% within 3 days. We conclude that viral infections are prevalent among infants hospitalized for suspected sepsis, and most can be detected early enough to influence patient management.

Role of the virology laboratory in diagnosis and management of patients with central nervous system disease

A number of viruses cause acute central nervous system disease. The two major clinical presentations are aseptic meningitis and the less common meningoencephalitis. Clinical virology laboratories are now more widely available than a decade ago; they can be operated on a modest scale and can be tailored to the needs of the patients they serve. Most laboratories can provide diagnostic information on diseases caused by enteroviruses, herpesviruses, and human immunodeficiency virus. Antiviral therapy for herpes simplex virus is now available. By providing a rapid diagnostic test or isolation of the virus or both, the virology laboratory plays a direct role in guiding antiviral therapy for patients with herpes simplex encephalitis. Although there is no specific drug available for enteroviruses, attention needs to be paid to these viruses since they are the most common cause of nonbacterial meningitis and the most common pathogens causing hospitalization for suspected sepsis in young infants in the United States during the warm months of the year. When the virology laboratory maximizes the speed of viral detection or isolation, it can make a significant impact on management of these patients. Early viral diagnosis benefits patients with enteroviral meningitis, most of whom are hospitalized and treated for bacterial sepsis or meningitis or both; these patients have the advantage of early withdrawal of antibiotics and intravenous therapy, early hospital discharge, and avoidance of the risks and costs of unnecessary tests and treatment. Enteroviral infection in young infants also is a risk factor for possible long-term sequelae. For compromised patients, the diagnostic information helps in selecting specific immunoglobulin therapy. Good communication between the physician and the laboratory will result in the most benefit to patients with central nervous system viral infection.

Rapid and accurate viral diagnosis

In recent years, there has been increased recognition of the importance of viral infections. In addition, new antiviral agents have become available. These factors have led to a marked increase in utilization of viral diagnostic services. In this review, both conventional and rapid methods for viral diagnosis are presented, with emphasis on recent advances. The antiviral agents currently available and the major drugs under investigation are also briefly discussed. It is hoped that this review will serve as a useful adjunct for the management of patients with virus infections.

A combination of four cell types for rapid detection of enteroviruses in clinical specimens

Isolation in cell culture is currently the most sensitive and reliable way to demonstrate enterovirus (EV) in clinical specimens. During July-October 1982 and 1983, we studied the impact of adding two new cell lines, Buffalo green monkey kidney (BGM) and human rhabdomyosarcoma (RD), to the more traditional cell combination used for EV isolation, human embryonic lung (HEL) and primary cynomolgus monkey kidney (CMK) cells; 2,558 specimens were studied: 632 fecal, 677 respiratory, 537 CSF, and 712 blood. An EV was isolated from 417 (16%); of these, 77 (18%) were positive only in BGM or RD; 35% (146/417) of the specimens were positive in BGM, RD, or both, at least one day earlier than in the traditional cells. BGM cells were helpful in isolation of group B coxsackieviruses (CB): 99% of 121 positive specimens were detected in BGM vs 73% in CMK and 23% in HEL; 72% of the CB isolates were detected by day 2 in BGM vs 48% in CMK and 0% in HEL. RD cells were helpful in the isolation of echoviruses: 59% of the 189 positive specimens were detected in RD vs 67% in HEL and 58% in CMK. RD was the only positive cell type in 28/189 (15%) positive specimens; 31% of the echovirus isolates were detected by day 2 in RD, vs 20% in HEL and 19% in CMK. Using the cell types described, we provided the clinician with results in 42% of the EV-positive specimens by day 2 after inoculation and in 61% by day 4.