A new enzyme immunoassay for the detection of enteroviruses in faecal specimens

Enteroviruses and Parechoviruses

Infections with enteroviruses and human parechoviruses are highly prevalent, particularly in neonates, where they may cause substantial morbidity and mortality. Individuals with B-cell-related immunodeficiencies are at risk for severe enteroviral infections, usually a chronic and fatal meningoencephalitis. In transplant recipients and patients with malignancy, enterovirus infections typically involve the respiratory tract, but cases of severe, disseminated infection have been described. The mainstay of diagnosis for enterovirus and human parechovirus infections involves the use of molecular diagnostic techniques. However, routine nucleic acid-detection methods for enteroviruses will not detect human parechoviruses. Laboratory diagnosis of these viral infections is important in determining a patient's prognosis and guiding clinical management.

Presentation, diagnosis, and management of enterovirus infections in neonates

The nonpoliovirus enteroviruses commonly infect newborns, with consequences ranging from asymptomatic infection and benign illness, to severe, life-threatening disease. Frequently occurring symptoms include fever, irritability, lethargy, anorexia, and rash. Although most illnesses are mild, severe disease develops in a subset of newborns infected in the first 2 weeks of life. Severe disease may consist of sepsis, meningoencephalitis, myocarditis, pneumonia, hepatitis, and/or coagulopathy. Substantial mortality rates have been reported, and long-term sequelae may occur among survivors. Risk factors and clinical features associated with severe disease include absence of neutralizing antibody to the infecting serotype, maternal illness prior to or at delivery, prematurity, illness onset within the first few days of life, multiorgan disease, severe hepatitis, positive serum viral culture, and specific infecting serotype (e.g. group B coxsackieviruses and echovirus 11). Whereas the mainstay of diagnosis has traditionally been viral isolation in tissue culture, the polymerase chain reaction has been demonstrated to be more sensitive than culture, highly specific, and rapid. Immunoglobulin has been used as a therapeutic agent for neonates with enterovirus disease; however, clinical efficacy has not been proven. Specific antiviral therapy for enteroviruses is in development. Pleconaril is an investigational agent that inhibits viral attachment to host cell receptors and uncoating of viral nucleic acid. It has broad and potent anti-enterovirus activity, excellent oral bioavailability, and is well tolerated. Some clinical trials have demonstrated benefit in children and adults with enterovirus meningitis, and in adults with upper respiratory tract infections caused by picornaviruses (rhinoviruses or enteroviruses). Data summarizing compassionate use for severe enterovirus diseases (including neonatal sepsis) also suggest possible benefit. Limited pharmacokinetic data are available in infants and neonates. A multicenter, placebo-controlled, randomized trial of pleconaril in neonates with severe hepatitis, coagulopathy, and/or myocarditis is currently being conducted.

Human rhabdomyosarcoma cells for rapid detection of enteroviruses by shell-vial assay

The ability of the RD (rhabdomyosarcoma) and MRC-5 cell-lines to detect enteroviruses in 33 clinical samples (cerebrospinal fluid, stools and throat swabs) was evaluated. The samples had previously tested enterovirus-positive by traditional tube-culture and had been frozen after their initial processing. By traditional tube-culture, 100 and 85 % of samples were positive for enterovirus in RD and MRC-5 cells, respectively. By rapid shell-vial assay, 94 and 45.5 % were positive after 48 h incubation in RD and MRC-5 cells, respectively. RD cells supported growth of all enterovirus serotypes, whereas MRC-5 cells were not able to detect any of the three coxsackieviruses that were found (one coxsackievirus A9 and two coxsackievirus B5). The shell-vial assay with RD cell-lines may be a useful tool for rapid diagnosis of enteroviral infection.

Rapid methods for identification of poliovirus isolates and determination of polio neutralizing antibody titers in human sera

A new rapid method for identification and determination of the titer of polioviruses and other enteroviruses in cell monolayers grown in microtiter plates is described. The method is based on immunoperoxidase staining of infected cells with commercial monoclonal antibodies (MAb) and biotin-labeled secondary antibody. The presence of poliovirus or other enteroviruses was established as the appearance of at least one focus of cells with stained cytoplasm 6 h post-infection. Viral titers determined by this method were expressed as focus forming unit (FFU) per ml which was found to correspond approximately to 10 TCID(50)/ml. The suitability of this technique to determine poliovirus antibody titers in human sera was also tested comparing the immunocytochemical neutralization assay with a conventional neutralization in microtiter plates. The test was standardized using reference human sera in order to produce antibody titers expressed in international units (IU). In addition to high reproducibility, the new neutralization test appears to be sensitive, specific and rapid, and might thus represent a useful tool for the diagnosis of polio and other enterovirus infections.

Evaluation of enterovirus serological tests IgM-EIA and complement fixation in patients with meningitis, confirmed by detection of enteroviral RNA by RT-PCR in cerebrospinal fluid

An enzyme immunoassay (EIA) for detection of anti-enterovirus IgM antibodies was compared with complement fixation test in 43 patients with confirmed enterovirus meningitis by RT-PCR of cerebrospinal fluids (CSF). In 34% of patients with enterovirus meningitis, IgM antibodies could be found, whereas complement fixation tests were positive in only 20%. The specificity was determined with sera of 105 patients with non-enterovirus meningitis. Specificity of IgM EIA and of complement fixation was 94% and 85%, respectively. In four patients with meningitis but without enterovirus detection in CSF, RT-PCR and virus isolation from stools were positive. In three of these patients, IgM antibodies were detected, giving a strong indication of an enterovirus-associated disease. Because of the high specificity of IgM EIA, diagnosis of enterovirus-associated diseases can be carried out in a single serum sample, whereas by complement fixation tests, only fourfold increases in antibody titres in paired sera indicate an acute infection. The application of IgM EIA is especially important in cases of meningitis when CSF samples are not available and for diagnosis of enterovirus diseases with other clinical symptoms such as fever, enteritis, and hand-foot-and-mouth disease.