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Survival of infectious Poliovirus-1 in river water compared to the persistence of somatic coliphages, thermotolerant coliforms and Poliovirus-1 genome.

The microbiological quality of water is currently assessed by search for fecal bacteria indicators. There is, however, a body of knowledge demonstrating that bacterial indicators are less resistant to environmental factors than human pathogenic viruses and therefore underestimate the viral risk. As river water is often used as a resource for drinking water production, it is particularly important to obtain a valid estimation of the health hazard, including specific viral risk. This work was conducted to compare the survival of infectious Poliovirus-1 used as a pathogenic virus model to the persistence of, on the one hand, thermotolerant coliforms commonly used as indicators and on the other hand, to somatic coliphages and Poliovirus-1 genome considered as potential indicators. We studied the behavior of infectious Poliovirus-1 and the three (potential) indicators of viral contamination in river water at three different temperatures (4 degrees C,18 degrees C and 25 degrees C). This experiment was performed twice with river water sampled at two different periods, once in winter and once in summer. Our results showed that the survival of thermotolerant coliforms can be 1.5-fold lower than infectious Poliovirus-1. In contrast, under all our experimental conditions, somatic coliphages and Poliovirus-1 genome persisted longer than infectious Poliovirus-1, surviving, respectively, 2-6-fold and about 2-fold longer than infectious Poliovirus-1. According to our results exclusively based on survival capacity, somatic coliphages and viral genome, unlike thermotolerant coliforms appear to be better indicators of viral contamination in river water. Moreover, the disappearance of viral genome is well-correlated to that one of infectious virus irrespective of the conditions tested.

Adaptation, Physiological↗

Comparison of neuropathogenicity of poliovirus in two transgenic mouse strains expressing human poliovirus receptor with different distribution patterns.

In order to determine the influence of poliovirus receptor (PVR) expression on poliovirus cell tropism and neuropathogenesis, two transgenic (tg) mouse models were produced in which PVR was expressed under the transcriptional control of the human PVR gene promoter (hg-PVR mice) and the CAG promoter (CAG-PVR mice). Then the pathogenicity of poliovirus after intracerebral inoculation of the type 1 Mahoney strain was compared. These showed completely different clinical and pathological changes. In the former, the expression of PVR in neurons in the central nervous system (CNS) conferred susceptibility to poliovirus, and a paralytic disease that resembled the human poliomyelitis occurred. In the latter, PVR expression was detected in glial and ependymal cells in addition to the neurons. Paralysis of the limbs and death were rarely observed and mice survived without showing substantial clinical abnormality. Histopathological examination revealed that glial and ependymal cells also became susceptible to poliovirus infection. Poliovirus antigens were mainly detected in ependymal and glial cells and hippocampal neurons near the lateral ventricles in the brain, but were not frequently detected in neurons in the brainstem unlike in the hg-PVR mice. The levels of viral antigens and virus recovered from the CNS of CAG-PVR mice began to decrease as early as 2 days after inoculation, which suggested induction of a fast immune response. These results suggest that the neuropathogenicity of poliovirus changes markedly depending on the specific expression of the PVR molecule in the CNS.

Animals↗

Three poliovirus 2B mutants exhibit noncomplementable defects in viral RNA amplification and display dosage-dependent dominance over wild-type poliovirus.

Many functions of the poliovirus genome in virally infected cells have been elucidated. However, the role of 2B (and of its precursor polypeptide, 2BC), encoded by the P2 region in the poliovirus genome, remains unknown. We have employed a genetic approach to examine the role of 2B in poliovirus-infected cells. We report here the phenotype of one previously isolated mutant in the 2B coding region, 2B201. In addition, we have constructed one additional mutation in the 2B coding region of an infectious poliovirus cDNA clone. Upon transfection into monkey Vero cells we could recover two 2B mutant polioviruses, 2B204 and 2B205. All three mutants exhibited small-plaque phenotypes on monkey Vero and human HeLa cells and displayed primary defects in viral RNA synthesis. None of the 2B mutants could be complemented by wild-type virus. Instead, the mutants exhibited a dosage-dependent dominance over wild-type poliovirus. Thus, the phenotypes of these 2B mutants implicate 2B and possibly its precursor, 2BC, in viral RNA amplification in poliovirus-infected cells, and the dominance of the 2B mutants suggests a structural role for 2B in viral replication complexes.

Animals↗

Nasopharyngeal secretory antibody response to poliovirus type 3 virion proteins exhibit different specificities after immunization with live or inactivated poliovirus vaccines.

By using immunoblotting, neutralization, and ELISA, the development of secretory antibody responses to poliovirus type 3 virion proteins (VP1, VP2, VP3) and to intact or trypsin-treated poliovirus type 3 was studied in the nasopharyngeal secretions in groups of infants after immunization with live attenuated poliovirus vaccine (OPV), enhanced potency inactivated poliovirus vaccine (IPV-EP), or after combined vaccination with IPV-EP followed by OPV. After three doses of vaccine, infants in all vaccine groups developed similar secretory IgA response to VP1 and VP2. The antibody response to VP3 was observed in 76.5% of subjects immunized with OPV alone and approximately 60% of those immunized with IPV-EP followed by OPV. However, only 13% of those immunized with IPV-EP alone exhibited VP3-specific antibody response. Significant differences in poliovirus type 3 specific antibody activity were observed between OPV and IPV-EP immunized subjects when trypsin-treated poliovirus was used as the antigen for neutralization or for ELISA in vitro. The neutralizing antibody activity against cleaved virus was significantly higher than against whole virus in the OPV vaccinated subjects. Both neutralizing and ELISA antibody activity against cleaved virus was significantly lower than against the whole virus in IPV-EP immunized subjects.

Antigens, Viral↗

Poliovirus surveillance: isolation of polioviruses in Japan, 1980-1991. A report of the National Epidemiological Surveillance of Infectious Agents in Japan.

This report presents an overall distribution of poliovirus isolations in Japan, where poliomyelitis has been under control over two decades as a result of legal administration of two doses of the trivalent live oral poliovirus vaccine of the Sabin strains (OPV) to children under 48 months of age. During the past 12 years from 1980 through 1991, a total of 1,126 poliovirus isolations from humans and 268 isolations from sewage/river water were reported by respectively 49 and nine of the participating laboratories. Type 2 was most frequently isolated from children after administration of one dose of OPV, followed by type 1 and type 3. On the contrary, after the second dose of OPV, the rate of isolation of type 3 exceeded those of type 2 and type 1. Seasonal and age distribution of poliovirus isolations from both humans and sewage/river water paralleled the OPV vaccination schedule in Japan. One percent of the isolations were, however, from infants younger than the vaccination-scheduled ages and 5% were from children older than those ages, including one each from 15 and 16 years olds. The data indicate that the poliovirus has silently been disseminated from vaccinated children to others and the community, thus suggesting repeated transmission of the viruses. The fact that some elder children had poliovirus colonization in their alimentary tracts indicates a potential risk of infection of such a population when exposed to a wild virus and of becoming a source of transmission to others.

Adolescent↗

Will containment of wild poliovirus in laboratories and inactivated poliovirus vaccine production sites be effective for global certification?

The absolute laboratory containment of any virus cannot be guaranteed, but a wealth of experience indicates that effective containment of wild poliovirus materials for global certification is technically and operationally feasible. Effective containment is based on the principles of minimal wild poliovirus infectious and potentially infectious materials in laboratories; minimal risks of operations in laboratories and inactivated poliovirus vaccine production facilities; minimal susceptibility of workers to wild poliovirus infection and shedding; and minimal susceptibility of populations to wild poliovirus spread. Each principle alone is imperfect, but collectively they greatly minimize the risks of transmitting wild poliovirus from the laboratory to the community.

Certification↗

Formation of poliovirus-like particles by recombinant baculoviruses expressing the individual VP0, VP3, and VP1 proteins by comparison to particles derived from the expressed poliovirus polyprotein.

The cDNA sequences encoding the VP0, VP3, and VP1 structural proteins of poliovirus type 3 (strain P3/Leon/37) have been individually cloned and used to prepare recombinant baculoviruses based on Autographa californica nuclear polyhedrosis viruses (AcNPV). Expression of the proteins was monitored in virus-infected Spodoptera frugiperda cells. Both the individually expressed VP0 protein and VP0 derived from the complete poliovirus coding region were shown to incorporate myristic acid. A significant improvement in VP0 protein yield was obtained when the amino terminal glycine of VP0 was changed to alanine (VP0/ala), suggesting that the presence of glycine or its myristylation is unfavorable for VP0 expression. Even so, the expression levels of the poliovirus capsid proteins were low by comparison with those obtained for other foreign genes (e.g., lacZ). The reason does not appear to be due to protein instability or, from the studies undertaken with VP0, the sequences that flank the AUG codon. Using recombinant baculoviruses that express VP0, VP1, and VP3 (or VP0/ala, VP1, and VP3), poliovirus-like particles (VLPs) were isolated from infected S. frugiperda cells. Examination by electron microscopy of the VLPs purified by CsCl gradient centrifugation revealed structures corresponding in size, appearance, and antigenicity to those expected for poliovirus procapsids; however, the yields of particles were low when compared to those derived from a construct (AcLeon) that expresses the complete coding region of poliovirus type 3, indicating that procapsid synthesis from the P1 precursor is a more favored route.

Amino Acid Sequence↗

In vitro stimulation of presensitized mouse spleen cells with poliovirus type 1, Mahoney, and enhancement of poliovirus-specific hybridomas.

In vivo immunization of BALB/c mice with poliovirus type 1, strain Mahoney, or with its purified polypeptides resulted in 0.2 to 0.5 antigen-specific hybridoma microcultures per 10(6) spleen cells. Stimulation of spleen cells from mice immunized with poliovirus or with its polypeptides in vitro with poliovirus 6 days prior to fusion with the myeloma cells led to a six- to 20-fold increase in the number of positive microcultures, i.e. after stimulation the yield of poliovirus-specific hybridomas was up to 3.8 antigen-specific microcultures per 10(6) spleen cells. The in vitro stimulation of spleen cells primed in vivo was demonstrated by the detection of poliovirus-specific antibody-producing cells 6 days after in vitro cultivation in the presence of poliovirus as antigen. Only spleen cells stimulated under these conditions in vitro gave rise to specific antibody-producing cells and yielded antigen-specific hybridomas after somatic hybridization.

Animals↗

A poliovirus replicon containing the chloramphenicol acetyltransferase gene can be used to study the replication and encapsidation of poliovirus RNA.

A poliovirus replicon, FLC/REP, which incorporates the reporter gene chloramphenicol acetyltransferase (CAT) in place of the region encoding the capsid proteins VP4, VP2, and part of VP3 in the genome of poliovirus type 3, has been constructed. Transfection of cells indicates that the FLC/REP replicon replicates efficiently and that active CAT enzyme is produced as a CAT-VP3 fusion protein. The level of CAT activity in transfected cells broadly reflects the level of FLC/REP RNA. A series of mutations in the 5' noncoding region of poliovirus type 3 were introduced into FLC/REP, and their effects were monitored by a simple CAT assay. These experiments helped to define further the stem-loop structures in the 5' noncoding region which are essential for RNA replication. The CAT-containing poliovirus replicon could also be packaged into poliovirus capsids provided by helper virus and was stable as a subpopulation of virus particles over at least four passages. The location of the CAT gene in FLC/REP excluded the presence of an encapsidation signal in the region of the poliovirus genome comprising nucleotides 756 to 1805.

Amino Acid Sequence↗

Analysis of reversions in the 5'-untranslated region of attenuated poliovirus after sequential administration of inactivated and oral poliovirus vaccines.

Replication of Sabin strains used in oral poliovirus vaccine (OPV) in the intestines of vaccine recipients leads to reversions that increase virus neurovirulence. Previously, a small study reported that prior immunization with inactivated poliovirus vaccine (IPV) resulted in faster accumulation of revertant virus, thus potentially increasing the risk of vaccine-associated paralytic poliomyelitis. We studied the impact that prior immunization with IPV and OPV has on shedding of revertant virus by healthy infants. By polymerase chain reaction (PCR), we amplified full-length poliovirus genomes directly from stool specimens from unimmunized infants and from infants previously immunized with IPV or OPV. The amplicons were used to quantify reversions in the 5'-untranslated region, using oligonucleotide microarray hybridization. Nearly all 140 samples that were PCR positive contained varying amounts of revertants of all 3 poliovirus serotypes. Polioviruses of Sabin types 2 and 3 reverted more easily than those of type 1. Prior vaccination with IPV did not increase the proportion of revertants after OPV administration.

DNA, Viral↗

Shedding of virulent poliovirus revertants during immunization with oral poliovirus vaccine after prior immunization with inactivated polio vaccine.

Fecal shedding of virulent revertant polioviruses was examined in isolates from infants previously immunized with > or = 1 dose of orally administered live attenuated polio vaccine (OPV) alone, enhanced-potency inactivated polio vaccine (EIPV) alone, or a combination of both. After administration of OPV alone, vaccine poliovirus serotypes were recovered in feces within 1 week and for as long as 31-60 days in 30%-80% of subjects after 1 or 2 doses and in 30%-50% after immunization with > or = 3 doses. No revertant poliovirus shedding was observed after OPV challenge in subjects immunized previously with > or = 3 doses of OPV. However, fecal shedding of revertant poliovirus after OPV challenge was observed in 50%-100% of subjects previously immunized with > or = 3 doses of the EIPV. These findings suggest that prior immunization with EIPV does not prevent fecal shedding of revertant polioviruses after subsequent reexposure to OPV.

Feces↗

Gut-homing (alpha(4)beta(7)(+)) Th1 memory responses after inactivated poliovirus immunization in poliovirus orally pre-immunized donors.

Mucosal infections are prevented by a specialized local immune system. Immune cells of this compartment can also be found in the blood and are characterized by the expression of mucosa-specific homing molecules. Here, the cellular immune responses after inactivated poliovirus immunization (IPV) in poliovirus orally pre-immunized donors were investigated. Subcutaneous IPV induced a transient increase in the proliferative response against poliovirus antigen and in the number of poliovirus-specific CD4(+) T cells in the blood of the vaccinees. These cells were characterized to be of the effector memory type (CD45RA(-)/CD45RO(+)/CCR7(-)/CD27(+)) and expressed the homing molecule alpha(4)beta(7), indicating their origin from the gut. Together these data show the recurrence of gut-derived poliovirus-specific cells upon IPV and evaluate the whole-blood assay as a powerful tool for monitoring the success of a vaccination.

Administration, Oral↗

Immunogenicity and fecal poliovirus excretion in sequential use of inactivated and oral poliovirus vaccines.

BACKGROUND AND PURPOSE: Though inoculation with inactivated poliovirus vaccine (IPV) is advocated, sequential use of IPV and live oral poliovirus vaccines (OPV) has many advantages. This study aimed to define the immunogenicities of IPV and OPV in Taiwanese children after the use of a sequential schedule of IPV-OPV and also to determine whether prior IPV inoculation hampers the fecal passage of OPV. METHODS: Fifty-nine infants were recruited to receive IPV-OPV sequential vaccinations consisting of IPV given at the ages of 2 and 4 months and OPV given at the ages of 6 and 18 months. Blood samples were taken at ages 2, 6, 18, and 19 months for antibody determination, and stool samples were collected to isolate vaccine strains of poliovirus after the second dose of OPV, at the age of 18 months. RESULTS: None of the children had severe systemic or local reactions. Protective antibodies were detected in all infants at the age of 6 months, 2 months after the second IPV dose. The antibody titers were augmented at the age of 19 months, 1 month after the booster dose of OPV. Stool samples collected 7 days after the second dose of OPV yielded at least one type of poliovirus in 9 of 18 children. Analysis of stool samples revealed that poliovirus was excreted by the 28th day in only two of the children. CONCLUSIONS: Our study showed that both IPV and OPV exhibit immunogenicity in Taiwanese children. Side effects of an IPV-OPV sequential schedule were mild and infrequent. Viral shedding in stools after OPV vaccination was preserved in a substantial proportion of subjects. These findings suggest that this sequential vaccination schedule can maintain herd immunity.

Antibodies, Viral↗

Poliovirus pathogenesis in a new poliovirus receptor transgenic mouse model: age-dependent paralysis and a mucosal route of infection.

We constructed a poliovirus receptor (PVR) transgenic mouse line carrying a PVR delta cDNA driven by a beta-actin promoter. We refer to this model as the cPVR mouse. The cPVR mice express Pvr in a variety of tissues (including small intestines, brain, spinal cord, muscle, blood and liver) and are susceptible to infection after intraperitoneal, intracerebral or intramuscular inoculation of poliovirus. After intraperitoneal inoculation, poliovirus replication is observed in cPVR muscle, brain, spinal cord and, notably, small intestine. The cPVR mice exhibit a striking age-dependent paralysis after intramuscular infection, with 2-week-old mice being 10,000-fold more susceptible to paralytic disease than adult mice. The cPVR mice are also susceptible to paralysis following intranasal infection with poliovirus. After intranasal infection, virus replication is observed in the olfactory bulb, cerebrum, brain stem and spinal cord, suggesting that intranasal infection of cPVR mice is a model for bulbar paralysis. Intranasally infected mice frequently display unusual neurological behaviours. The PVR transgenic mouse reported here provides the first available model for a mucosal route of infection with poliovirus.

Age Factors↗

Antibody responses to antigenic sites 1 and 3 of serotype 3 poliovirus after vaccination with oral live attenuated or inactivated poliovirus vaccine and after natural exposure.

Three important antigenic sites involved in virus neutralization on polioviruses in mouse experiments have been identified. These sites are located at the surface of the virion and have been designated antigenic sites 1, 2, and 3. In mice, the antibody response to antigenic site 1 of serotype 3 poliovirus is considered to be immunodominant, but little is known about the immunogenicity of these sites in humans. In the present study, we developed inhibition enzyme-linked immunosorbent assays specific for antigenic sites 1 and 3 to measure antibody responses to these sites in fully vaccinated inactivated poliovirus vaccine (IPV) (n = 63) and oral live attenuated poliovirus vaccine (OPV) (n = 63) recipients and in naturally infected persons (n = 25). Similar levels of antibodies to site 1 in IPV and OPV vaccinees were detected. However, significantly more OPV recipients (88.7%) had detectable antibodies to antigenic site 3 (P < 0.01) than did IPV-vaccinated persons (63. 1%). After an IPV booster vaccination, both previously IPV- and OPV-vaccinated persons responded with a significant increase in antibodies to sites 1 and 3 (P < 0.01). We conclude that the immune response to serotype 3 poliovirus in humans consists of both site 1- and site 3-specific antibodies and that these responses can be induced by either OPV or recent IPV vaccination.

Antibodies, Monoclonal↗

A recombinant virus between the Sabin 1 and Sabin 3 vaccine strains of poliovirus as a possible candidate for a new type 3 poliovirus live vaccine strain.

Biological tests including the monkey neurovirulence test performed on recombinants between the virulent Mahoney and attenuated Sabin 1 strains of type 1 poliovirus indicated that the genome region encoding mainly the viral capsid proteins had little correlation with the neurovirulence or attenuation phenotype of the virus. The results suggested that new vaccine strains of type 2 and type 3 polioviruses may be constructed in vitro by replacing the sequence encoding the antigenic determinants in viral capsid proteins of the Sabin 1 genome by the corresponding sequences of the type 2 and type 3 genome, respectively. Accordingly, we constructed recombinants between the Sabin 1 and Sabin 3 strains of poliovirus in which genome sequences of the Sabin 1 strain encoding most or all capsid proteins were replaced by the corresponding genome sequences of the Sabin 3 strain. One of the recombinant viruses thus constructed was fully viable and showed antigenicity and immunogenicity identical to those of type 3 poliovirus. The monkey neurovirulence tests and in vitro phenotypic marker tests (temperature sensitivity of growth, sodium bicarbonate concentration dependency of growth under agar overlay, and size of plaque) were performed on the recombinant virus. The stability of the virus in regard to the temperature sensitivity phenotype was also tested. The results suggested that the recombinant virus is a possible candidate for a new type 3 poliovirus vaccine strain.

Animals↗

Transgenic mice carrying the human poliovirus receptor: new animal models for study of poliovirus neurovirulence.

Recombinant viruses between the virulent Mahoney and attenuated Sabin 1 strains of poliovirus type 1 were subjected to neurovirulence tests using a transgenic (Tg) mouse line, ICR-PVRTg1, that carried the human poliovirus receptor gene. The Tg mice were inoculated intracerebrally with these recombinant viruses and observed for clinical signs, histopathological lesions, and viral antigens as parameters of neurovirulence of the viruses. These parameters observed in the Tg mice were different for different inoculated viruses. Dose-dependent incidences of paralysis and of death were observed in the Tg mice inoculated with any viruses used. This indicates that values of 50% lethal dose are useful to score a wide range of neurovirulence of poliovirus. The neurovirulence of individual viruses estimated by the Tg mouse model had a strong correlation with those estimated by monkey model. Consequently, the mouse tests identified the neurovirulence determinants on the genome of poliovirus that had been identified by monkey tests. In addition, the mouse tests revealed new neurovirulence determinants, that is, different nucleotides between the two strains at positions 189 and 21 and/or 935 in the 5'-proximal 1,122 nucleotides. The Tg mice used in this study may be suitable for replacing monkeys for investigating poliovirus neurovirulence.

Animals↗

Introduction of inactivated poliovirus vaccine into oral poliovirus vaccine-using countries.

Given the progress already made towards the goal of global eradication of poliomyelitis LE (polio), the risk of paralytic poliomyelitis is changing in many geographical areas. Vaccination against polio will need to continue because of the threat of wild poliovirus importation. However, an increasing number of polio-free countries are determining that the risk of paralytic poliomyelitis associated with continued routine immunization using oral poliovirus vaccine (OPV) is greater than the risk of importation or laboratory handling of wild poliovirus. Some of these countries have introduced inactivated poliovirus vaccine (IPV)--a safe and effective alternative for routine immunization--using one of two approaches: replacement of OPV by IPV and introduction of a sequential IPV/OPV schedule. Countries considering such changes should conduct a thorough evaluation of the epidemiological, financial and operational implications before finalizing a change in policy. Tropical developing countries pose a special challenge for policy formulation on IPV. In these countries, given the unresolved issues related to the immunogenicity of IPV when administered in the WHO/Expanded Programme on Immunization (EPI) vaccination schedule, the continued focal circulation of wild poliovirus on two continents, the relatively high cost of IPV and the operational complexities of introducing this vaccine, WHO does not--as of July 2003--recommend the adoption of IPV alone or in a sequential schedule. It is expected that this position will be reviewed late 2004 and, if appropriate, revised according to the additional information that has become available on IPV effectiveness, logistic implications, and on further progress towards polio eradication. WHO is encouraging operational studies and introduction projects to evaluate these issues.

Developing Countries↗