Rapid diagnosis of poliovirus infection by PCR amplification

Polio Eradication Initiative (PEI) contribution in strengthening public health laboratories systems in the African region

BACKGROUND

The laboratory has always played a very critical role in diagnosis of the diseases. The success of any disease programme is based on a functional laboratory network. Health laboratory services are an integral component of the health system. Efficiency and effectiveness of both clinical and public health functions including surveillance, diagnosis, prevention, treatment, research and health promotion are influenced by reliable laboratory services. The establishment of the African Regional polio laboratory for the Polio Eradication Initiative (PEI) has contributed in supporting countries in their efforts to strengthen laboratory capacity. On the eve of the closing of the program, we have shown through this article, examples of this contribution in two countries of the African region: Côte d'Ivoire and the Democratic Republic of Congo.

METHODS

Descriptive studies were carried out in Côte d'Ivoire (RCI) and Democratic Republic of Congo (DRC) from October to December 2014. Questionnaires and self-administered and in-depth interviews and group discussions as well as records and observation were used to collect information during laboratory visits and assessments.

RESULTS

The PEI financial support allows to maintain the majority of the 14 (DRC) and 12 (RCI) staff involved in the polio laboratory as full or in part time members. Through laboratory technical staff training supported by the PEI, skills and knowledge were gained to reinforce laboratories capacity and performance in quality laboratory functioning, processes and techniques such as cell culture. In the same way, infrastructure was improved and equipment provided. General laboratory quality standards, including the entire laboratory key elements was improved through the PEI accreditation process.

CONCLUSION

The Polio Eradication Initiative (PEI) is a good example of contribution in strengthening public health laboratories systems in the African region. It has established strong Polio Laboratory network that contributed to the strengthening of capacities and its expansion to surveillance of other viral priority diseases such as measles, yellow fever, Influenza, MERS-CoV and Ebola. This could serve as lesson and good example of laboratory based surveillance to improving diseases prevention, detection and control in our middle and low income countries as WHO and partners are heading to polio eradication in the world.

Poliomyelitis: historical facts, epidemiology, and current challenges in eradication

Poliomyelitis is a highly infectious disease caused by a virus belonging to the Picornaviridae family. It finds a mention even in ancient Egyptian paintings and carvings. The clinical features are varied ranging from mild cases of respiratory illness, gastroenteritis, and malaise to severe forms of paralysis. These have been categorized into inapparent infection without symptoms, mild illness (abortive poliomyelitis), aseptic meningitis (nonparalytic poliomyelitis), and paralytic poliomyelitis. This disease has been associated with crippling deformities affecting thousands of lives throughout the world. Only due to the perseverance and determination of great scientists in 1900s, the genomic structure of the virus and its pathogenesis could be elucidated. Contribution of Salk and Sabin in the form of vaccines-oral polio vaccine (OPV) and the inactivated polio vaccine-heralded a scientific revolution. In 1994, the World Health Organization (WHO) Region of The Americas was certified polio free followed by the WHO Western Pacific Region in 2000 and the WHO European Region in June 2002 of the 3 types of wild poliovirus (types 1, 2, and 3). In 2013, only 3 countries remained polio endemic-Nigeria, Pakistan, and Afghanistan. Global eradication of polio is imperative else the threat of an outbreak will hover forever. Today, all the governments of the world in collaboration with WHO stand unified in their fight against poliomyelitis and the task when achieved will pave the way for eliminating other infections in future.

Emergence of vaccine-derived polioviruses, Democratic Republic of Congo, 2004-2011

Polioviruses isolated from 70 acute flaccid paralysis patients from the Democratic Republic of Congo (DRC) during 2004-2011 were characterized and found to be vaccine-derived type 2 polioviruses (VDPV2s). Partial genomic sequencing of the isolates revealed nucleotide sequence divergence of up to 3.5% in the viral protein 1 capsid region of the viral genome relative to the Sabin vaccine strain. Genetic analysis identified at least 7 circulating lineages localized to specific geographic regions. Multiple independent events of VDPV2 emergence occurred throughout DRC during this 7-year period. During 2010-2011, VDPV2 circulation in eastern DRC occurred in an area distinct from that of wild poliovirus circulation, whereas VDPV2 circulation in the southwestern part of DRC (in Kasai Occidental) occurred within the larger region of wild poliovirus circulation.

Interrupting wild poliovirus transmission using oral poliovirus vaccine: environmental surveillance in high-risks area of India

Global eradication of poliomyelitis has reached critical stage. Sabin Oral Poliovirus Vaccine (OPV) has been successful in three major regions of the world. In India eradication of poliomyelitis from states of Uttar Pradesh (UP) and Bihar has been difficult due to high population and low-socioeconomic standards of living. Acute flaccid paralysis (AFP) surveillance and intensive OPV rounds continues with the World Health Organization (WHO) operational strategies. Yet apparent lack of progress in reducing the number of wild cases has resulted in occasional impatience and frustration, even leading to questions about ultimate feasibility of global eradication using OPV. Lucknow in UP is in geographical area endemic for poliomyelitis and is surrounded by high-risk areas yet maintains a polio-free status since 2002. Environmental surveillance study was conducted (2004-2006) to authenticate the decline in the wild poliovirus (PV) cases in Lucknow. Sewage sample analyses were compared with stools of AFP patients and healthy children from same geographical area. Study reveals useful information on OPV circulation and proves important epidemiological tool to trust WHO's OPV immunization program. Genetic sequencing had detected silent wild PV-1 circulation of RCP1PGI (EU049849), RCP2PGI (EU049850), RCP3PGI (EU049851), and RCP4PGI (EU049852) in sewage waters. Properties of isolates from sewage reflected those of viruses excreted from human. This study provides valuable information and encouragement to AFP surveillance to maintain high levels of OPV immunization campaigns in the most difficult endemic region of India to interrupt the wild PV transmission.

Basic rationale, current methods and future directions for molecular typing of human enterovirus

Enterovirus is a genus of the Picornaviridae family including more than 80 serotypes belonging to four species designed Human enterovirus A to D. The antigens of the structural proteins support the subdivision of enteroviruses into multiple serotypes. Comparative phylogeny based on molecular typing methods has been of great help to classify former and new types of enterovirus, and to investigate the diversity of enteroviruses and the evolutionary mechanisms involved in their diversity. By now, molecular typing methods of enterovirus rely mainly on the sequencing of an amplicon targeting a variable part of the region coding for the capsid proteins (VP1 and, alternatively, VP2 or VP4), either from a strain recovered by cell culture or, more recently, by direct amplification of a clinical or environmental specimen. In the future, microarrays are thought to play a major role in enterovirus typing and in the analysis of the determinants of virulence that support the puzzling diversity of the pathological conditions associated with human infection by these viruses.

Prevalence of vaccine-derived polioviruses in stools of immunodeficient children in South Africa

AIMS

The aim of the study was to determine the prevalence of vaccine-derived polioviruses (VDPVs) in stool specimens of immunodeficient patients such as HIV-positive children (including those with an AIDS indicator condition, according to the Centres for Disease Control and Prevention classification) by applying various molecular techniques.

METHODS AND RESULTS

A total of 164 stool samples from HIV-positive children and 23 stool samples from healthy immunocompetent children (the control group) were analysed during 2003 and 2004. By applying a reverse transcription polymerase chain reaction (RT-PCR) in combination with a nested PCR, a total of 54 enteroviruses were detected in the stool specimens of the immunodeficient children. The use of restriction enzymes and a Sabin specific RT-triplex PCR confirmed the presence of 13 polioviruses (PVs), such as seven Sabin PV type 1, four Sabin PV type 3 and two Sabin PV type 2 isolates. The 5'untranslated region and the VP1 capsid-encoding protein of the 13 PVs and the three PVs from the stools of the immunocompetent children were partially sequenced and their genetic relatedness was deduced from the constructed phylogenetic trees. The majority of the PVs isolated from the stools of the immunodeficient children (10 of 13 isolates) were classified as 'oral poliovirus vaccine (OPV)-like viruses', as these isolates had close sequence relationships (>99% in VP1 nucleotide sequences) to the original Sabin PV vaccine strains. Three PVs showed < or =99% VP1 sequence identity to the Sabin PV vaccine strains and were classified as 'suspected' immunodeficient VDPVs (iVDPVs). All of the OPV-like isolates and the 'suspected' iVDPVs carried mutations at specific positions in their partially sequenced regions, which have been associated with reversion of the attenuated Sabin PV vaccine strains to increased neurovirulence.

CONCLUSIONS

Thus, this study adds further evidence to the observation that immunodeficient individuals may excrete OPV strains with potential neurovirulent phenotypes.

SIGNIFICANCE AND IMPACT OF THE STUDY

Prolonged excretion of PVs by immunodeficient individuals is of major concern, because continued replication of PVs in the human gut could result in the reversion of these viruses to greater neurovirulence. When exposed to OPV, immunodeficient patients may become chronically infected, spreading potentially neurovirulent VDPVs for many months or years to close contacts and children who are no longer being vaccinated after termination of OPV vaccination in the near future.

Detection of enteroviruses by reverse-transcriptase polymerase chain reaction in cell culture negative stool specimens of patients with acute flaccid paralysis

The aim of this study was the detection of a 114 base pairs amplicon in 5' non-translated region of enterovirus genome in stool specimens of patients with acute flaccid paralysis (AFP) which were negative on cell culture. One hundred and twenty stool specimens were collected from AFP cases and tested with cell culture (RD, L20B and Hep2 cell lines). RT-PCR was carried out for the specimens with negative cell culture result. A 10% raise in enterovirus detection was observed with RT-PCR. This increased sensitivity can improve the detection of enterovirus serotypes which grow poorly in cell culture, and can thus alter significantly the medical care of patients with acute flaccid paralysis.

Poliovirus vaccine strains in sewage and river water in South Africa

Since the initiation of the global poliomyelitis eradication program in 1988, the number of wild-type polio cases decreased from 350,000 to fewer than 500, and the number of polio endemic countries declined from more than 125 to 10. The last case of polio in South Africa caused by a wild-type poliovirus (PV) occurred in 1989. The live attenuated oral poliovirus vaccine (OPV) has been effectively used in the reduction and control of poliomyelitis. However, as OPV strains are excreted in stools after vaccination, this vaccine could become a source of dissemination of PVs in the environment and the potential cause of poliomyelitis. Therefore, the aim of the study was to determine the occurrence of OPV strains in selected sewage and river water samples. During the period between 2001 and 2003, 138 samples of river water and 213 samples of settled sewage were collected from selected areas of South Africa. A total of 860 plaques were analysed, which consisted of 703 plaques from the sewage and 157 plaques from the river water samples. Using a reverse transcriptase (RT)-multiplex PCR, 49 PVs were successfully distinguished from 176 non-polio enteroviruses (NPEVs). The 176 NPEVs consisted of 50 coxsackie B2 viruses (CBV2), followed by 39 echoviruses 11 (ECV11), 25 CBV5, 21 CBV3, 15 CBV4, 14 coxsackie A6 viruses (CAV6), 7 CBV6, 2 CAV5, 2 CBV1, and 1 ECV19, which was in agreement with the prevalence of these EVs in other parts of the world. The Sabin-specific RT-triplex PCR revealed the presence of 29 Sabin PV type 1, 8 Sabin PV type 2, and 12 Sabin PV type 3 isolates. Buffalo green monkey kidney and primary liver carcinoma cell cultures allowed the amplification of a broad spectrum of EVs, whereas human epidermoid carcinoma cells were more selective for PVs. This study addressed some of the issues regarding the prevalence of OPV strains in the environment. The identification of 49 viable OPV isolates confirmed the presence and circulation of PV vaccine strains in sewage and river water. The extent of the potential health risk constituted by these OPV isolates remains to be investigated.

Identification of enteroviral infection among infants and children admitted to hospital with acute gastroentritis in Ho Chi Minh City, Vietnam

A total of 276 fecal specimens collected from infants and children admitted to hospital with acute gastroenteritis in Ho Chi Minh City, Vietnam from October 2002 to September 2003, were tested for the presence of enteroviruses by RT-PCR and virus isolation. Enteroviruses were detected in 27 patients by RT-PCR corresponding to 9.8%. However, only four enterovirus strains could be isolated by cell culture with two different cell lines CaCo2 and Vero, showing specific cytopathic effect (CPE). The results clearly indicate that RT-PCR is a sensitive, specific assay to investigate the true burden of acute gastroenteritis due to enteroviruses in clinical fecal specimens. In the present study, enteroviruses were identified throughout the year except in May and the highest number was in December. Enteroviruses were subjected to molecular analysis by sequencing. It was found that enterovirus strains detected were classified further into two distinct genetic clusters (I, II) and demonstrated the great genetic diversity among them. Based on genetic analysis, 5' noncoding region (5' NCR) sequences suggested the predominant presence of Vietnamese enteroviruses with the greatest similarities to coxsakieviruses (51.9%) and echoviruses (29.6%). Interestingly, two of the sequenced specimens of enteroviruses were similar to a new strain called enterovirus 74. This report is the first detection of enteroviral infection in feces from infants and children admitted to hospital with acute gastroenteritis in Vietnam.

An increase in selenium intake improves immune function and poliovirus handling in adults with marginal selenium status

BACKGROUND

Dietary selenium intakes in many countries, including the United Kingdom, are lower than international recommendations. No functional consequences of these lower intakes have been recognized, although experimental studies suggest that they might contribute to reduced immune function, increased cancer incidence, and increased susceptibility to viral disease.

OBJECTIVE

The objective was to assess whether administration of small selenium supplements to otherwise healthy UK subjects leads to functional changes in immune status and the rates of clearance and mutation of a picornavirus: live attenuated polio vaccine.

DESIGN

Twenty-two adult UK subjects with relatively low plasma selenium concentrations (<1.2 micromol/L, approximately 60% of those screened) received 50 or 100 microg Se (as sodium selenite) or placebo daily for 15 wk in a double-blind study. All subjects received an oral live attenuated poliomyelitis vaccine after 6 wk and enriched stable (74)Se intravenously 3 wk later.

RESULTS

Selenium supplementation increased plasma selenium concentrations, the body exchangeable selenium pool (measured by using (74)Se), and lymphocyte phospholipid and cytosolic glutathione peroxidase activities. Selenium supplements augmented the cellular immune response through an increased production of interferon gamma and other cytokines, an earlier peak T cell proliferation, and an increase in T helper cells. Humoral immune responses were unaffected. Selenium-supplemented subjects also showed more rapid clearance of the poliovirus, and the poliovirus reverse transcriptase-polymerase chain reaction products recovered from the feces of the supplemented subjects contained a lower number of mutations.

CONCLUSIONS

The data indicate that these subjects had a functional selenium deficit with suboptimal immune status and a deficit in viral handling. They also suggest that the additional 100 microg Se/d may be insufficient to support optimal function.

Detection of viral sequences in archival spinal cords from fatal cases of poliomyelitis in 1951-1952

Poliovirus (PV) subjected to genetic characterization is often isolated from faecal carriage. Such virus is not necessarily identical to the virus causing paralytic disease since genetic modifications may occur during replication outside the nervous system. We have searched for poliovirus genomes in the 14 fatal cases occurring during the last epidemics in Norway in 1951-1952. A method was developed for isolation and analysis of poliovirus RNA from formalin-fixed and paraffin-embedded archival tissue. RNA was purified by incubation with Chelex-100 and heating followed by treatment with the proteinase K and chloroform extraction. Viral sequences were amplified by a reverse transcriptase-polymerase chain reaction (RT-PCR), the products subjected to TA cloning and sequenced. RNA from the beta-actin gene, as a control, was identified in 13 cases, while sequences specific for poliovirus were achieved in 11 cases. The sequences from the 2C region of poliovirus were rather conserved while those in the 5'-untranslated region were variable. The developed method should be suitable also for other genetic studies of old archival material.

RT-PCR based analysis of cell culture negative stools samples from poliomyelitis suspected cases

BACKGROUND

Routine diagnosis of acute flaccid paralysis (AFP) is still based on classical virological procedures. Several serotypes of enterovirus which possess the potential to cause neurological disorders are not easily isolated in the cell culture systems used for the AFP diagnosis.

OBJECTIVES

Our goal was to look into the presence of enterovirus genomes in fecal suspensions previously considered negative by cell culture procedures, using RT-PCR.

STUDY DESIGN

One hundred and seventy-three fecal samples collected from AFP cases and contacts occurring in Brazil, Peru and Bolivia and tested negative regarding viral isolation, after inoculation in the cell lines RD and Hep2C, were analyzed by RT-PCR using a pair of primers which specifically detects enterovirus genome RNA's.

RESULTS

Twenty-six samples (15%) showed amplicons compatible with those observed for enterovirus RNA amplification. The identity of these amplicons were confirmed by nucleotide sequencing. By using RT-PCR directly in the fecal suspensions we were able to detect enterovirus RNA's in twenty-six additional samples. These samples would be considered as negative if only the standard cell-culture-based methodology had been utilized. No polioviruses were detected among the positive samples.

[Contribution to knowledge about the permanence and circulation of poliovirus vaccine in the environment]

The erradication of poliomyelitis in the world is a goal that requires the adoption of effective and safe strategies for its attainment. Knowing how long the strains of poliovirus derived from the oral attenuated virus vaccine may circulate and remain in the environment was essential to define the measures to be taken and was also the objective of our paper. Specimens of stools and sewage water, which were weekly obtained at the end of the National Polio Vaccination Campaign, in 1998, were analyzed. Viruses were isolated and identified by culture and neutralization tests for the identification of poliovirus. In the particular case of the sewage water, it was also used the polymerase chain reaction. The curves of elimination in both media were drawn and it was concluded that the permanence of viruses in the environment did not exceed the 12 weeks after the immunization with the oral attenuated virus vaccine.

Multicenter quality assessment of PCR methods for detection of enteroviruses

We conducted a multicenter evaluation of commercial and in-house PCR methods for the detection of enteroviruses. Three coded panels of test and control RNA samples, artificial clinical specimens, and representative enterovirus serotypes were used to assess amplification methods, RNA extraction methods, and reactivities with different enterovirus serotypes. Despite several differences between PCR methods, there was good agreement, although some variation in sensitivity was observed. Most PCR methods were able to detect enterovirus RNA derived from 0.01 50% tissue culture infective dose (TCID50) and were able to detect at least 1 TCID50 of enterovirus in cerebrospinal fluid, stool, or throat swab specimens. Most were also able to detect a wide range of enterovirus serotypes, although serotypic identification was not possible. Some laboratories experienced false-positive results due to PCR contamination, which appeared to result mainly from cross-contamination of specimens during RNA extraction. Provided that this problem is overcome, these PCR methods will prove to be a sensitive and rapid alternative to cell culture for the diagnosis of enterovirus infection.

A polymerase chain reaction-based epidemiologic investigation of the incidence of nonpolio enteroviral infections in febrile and afebrile infants 90 days and younger

OBJECTIVE

Enteroviruses are important pathogens in infants, but their true contribution to febrile illness in infants </=90 days old is unknown. The purpose of this study was to use the polymerase chain reaction (PCR) for diagnosis of enteroviral (EV) infection in febrile and afebrile infants </=90 days of age to improve the understanding of the epidemiology of EV infection in this population.

METHODS

Patients included all unimmunized, febrile infants </=90 days of age admitted to Primary Children's Medical Center (Salt Lake City, UT) for sepsis evaluation from December 1996 to December 1997. Blood, urine, cerebrospinal fluid, and throat swabs were tested for enteroviruses using a PCR assay (Roche Molecular Systems, Branchburg, NJ). Alternate PCR assays separated polio and nonpolio enteroviruses. Results of bacterial cultures, outcome, and hospital charges were obtained. Blood from afebrile, control infants </=90 days old was tested for enteroviruses.

RESULTS

A total of 345 febrile infants were enrolled; 89 (25.8%) were positive for enterovirus. The incidence of EV infection ranged from 3.2% in January to 50% in August and October. Five EV-positive, febrile infants (5.6%) had concomitant urinary tract infections, and 1 (1. 1%) had concomitant bacteremia. Infants with confirmed EV infection were significantly less likely to have bacterial infection than those who were EV-negative. All infants infected with an enterovirus recovered. Average length of stay was 3 days, average charges were nearly $4500. Eighty-six afebrile, control infants were enrolled; 6 (6.9%) were positive for enterovirus; 3 had received oral polio vaccine.

CONCLUSIONS

Nonpolio EV infections commonly cause fever in infants </=90 days of age. Rates of EV positivity are low in afebrile, unimmunized infants. The use of PCR to identify febrile infants with nonpolio EV infections may decrease length of hospital stay, unnecessary antibiotic administration, and charges.

Wild poliovirus circulation among healthy children immunized with oral polio vaccine in Antananarivo, Madagascar

From July 1995 to December 1996, 3185 stool specimens from healthy children aged 6-59 months attending 6 dispensaries in the Antananarivo area were examined for poliovirus. The children had been routinely immunized according to the Expanded Programme on Immunization (EPI) schedule and received the last dose of oral polio vaccine (OPV) more than 1 month before stool collection. 99.4% of the children were immunized with at least 3 doses of OPV. HEp-2 cell culture revealed virus infections in 192 stools (6.0%), including 9 poliovirus (0.3%) and 183 nonpolio enterovirus isolates (5.7%). Infections occurred throughout the year, but incidence was higher during the hot and rainy season (P=0.01). Using a neutralization test with monoclonal antibodies and PCR-RFLP in two genomic regions coding for the VP1 capsid and RNA polymerase, 4 wild polioviruses (3 type 1 and 1 type 3) and 5 vaccine-related polioviruses (2 Sabin 1-like variants, 1 Sabin 2-like and 2 Sabin 3-like) strains were identified. The wild polioviruses were isolated at the beginning and the end of the dry season. Similar RFLP patterns were observed for the 3 wild type 1 polioviruses. Comparison of partial genomic sequences in the VP1/2 A region of 1 of the wild type 1 isolates with 2 wild type strains isolated in Antananarivo in 1992 and 1993 showed a divergence of at least 10% between the strains, suggesting at least two different pathways of transmission during this period. Our findings demonstrate that immunization with 3 doses of OPV did not prevent intestinal carriage of wild poliovirus strains, and that there is a risk of wild poliovirus transmission to susceptible children in the area. Multiple strategies are required to improve immunization coverage in Madagascar.

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.