Excretion of attenuated polioviruses in children vaccinated with live oral poliovirus vaccine

The excretion of attenuated polioviruses was studied in a group of nursery children vaccinated with 105TCD50 of each type of virus. The primovaccinated children were found to excrete type 1 poliovirus for 8 weeks, type 2 for 11 weeks after the vaccination with the type 1 + 2 bivaccine. Poliovirus type 1 as eliminated by 78% and type 2 by 98% of the vaccinees. The separately administered type 3 was detectable for 6 weeks and was isolated from 100% of the vaccinees. The highest per cent of children with type 1 excretion positivity was recorded at week 5, with type 2 positivity at week 1 and with type 3 positivity at week 2. The poliovirus excretion peaked early after the vaccination, the titres of the poliovirus type 2 were the highest. The children revaccinated next year with the type 1 + 2 bivaccine eliminated the respective types of virus 1 - 2 weeks; type 3 poliovirus was detectable for 6 weeks after revaccination and was excreted by the highest per cent of vaccines. The contact infections caused by the attenuated polioviruses developed in 9 from 22 children vaccinated previously. The excretion of polioviruses did not last longer than 1 week. The contact infections were most frequently caused by the poliovirus type 2. The examined children, particularly those vaccinated previously, turned out to excrete also other enteroviruses identified as Coxsakieviruses B 4 and B 5 and Echovirus 21. In the primovaccinated these viruses were isolated only from those with the negative excretion of polioviruses.     

Genomic features of intertypic recombinant sabin poliovirus strains excreted by primary vaccinees

The trivalent oral poliomyelitis vaccine (OPV) contains three different poliovirus serotypes. It use therefore creates particularly favorable conditions for mixed infection of gut cells, and indeed intertypic vaccine-derived recombinants (VdRec) have been frequently found in patients with vaccine-associated paralytic poliomyelitis. Nevertheless, there have not been extensive searches for VdRec in healthy vaccinees following immunization with OPV. To determine the incidence of VdRec and their excretion kinetics in primary vaccinees, and to establish the general genomic features of the corresponding recombinant genomes, we characterized poliovirus isolates excreted by vaccinees following primary immunization with OPV. Isolates were collected from 67 children 2 to 60 days following vaccination. Recombinant strains were identified by multiple restriction fragment length polymorphism assays. The localization of junction sites in recombinant genomes was also determined. VdRec excreted by vaccinees were first detected 2 to 4 days after vaccination. The highest rate of recombinants was on day 14. The frequency of VdRec depends strongly on the serotype of the analyzed isolates (2, 53, and 79% of recombinant strains in the last-excreted type 1, 2, and 3 isolates, respectively). Particular associations of genomic segments were preferred in the recombinant genomes, and recombination junctions were found in the genomic region encoding the nonstructural proteins. Recombination junctions generally clustered in particular subgenomic regions that were dependent on the serotype of the isolate and/or on the associations of genomic segments in recombinants. Thus, VdRec are frequently excreted by vaccinees, and the poliovirus replication machinery requirements or selection factors appear to act in vivo to shape the features of the recombinant genomes.     

The trend of acquired immunity with live poliovirus vaccine and the effect of revaccination: follow-up of vaccinees for ten years

The persistence of neutralizing antibody (NA) against three types of poliovirus acquired after two doses of trivalent live attenuated poliovirus vaccine (LPV) has been followed up for ten years in individual vaccinees. Sixty-seven children were bled once a year over a five year period following the primary vaccination. More than 80% of them retained NA against all three types of poliovirus. Thirty-two individuals whose NA titres were 1:16 or over for types 1 and 2 and 1:4 or over for type 3 at the fifth year were further followed up for a further five years and it was shown that during this period some of them had a naturally-acquired antibody rise, mostly against type 3 virus. At the sixth to eighth year after the primary vaccination, one further dose of the trivalent vaccine was administered to the children whose NA titres were down to 1:8 or less and the effect of booster vaccination on NA was followed. Other subjects were revaccinated with LPV and their fecal excretion of the vaccine virus was investigated. The results showed that a decrease in serum antibody level could be a good indicator of the local resistance of the alimentary tract and that reinfection could occur if serum NA had decreased to 1:8 or less, which allowed a virus excretion in the stools.     

Human Circulating Antibody-Producing B Cell as a Predictive Measure of Mucosal Immunity to Poliovirus

Background

The “gold standard” for assessing mucosal immunity after vaccination with poliovirus vaccines consists in measuring virus excretion in stool after challenge with oral poliovirus vaccine (OPV). This testing is time and resource intensive, and development of alternative methods is a priority for accelerating polio eradication. We therefore evaluated circulating antibody-secreting cells (ASCs) as a potential means to evaluate mucosal immunity to poliovirus vaccine.

Methods

199 subjects, aged 10 years, and previously immunized repeatedly with OPV, were selected. Subjects were assigned to receive either a booster dose of inactivated poliovirus vaccine (IPV), bivalent OPV (bOPV), or no vaccine. Using a micro-modified whole blood-based ELISPOT assay designed for field setting, circulating poliovirus type-specific IgA- and IgG-ASCs, including gut homing α4β7+ ASCs, were enumerated on days 0 and 7 after booster immunization. In addition, serum samples collected on days 0, 28 and 56 were tested for neutralizing antibody titers against poliovirus types 1, 2, and 3. Stool specimens were collected on day 28 (day of bOPV challenge), and on days 31, 35 and 42 and processed for poliovirus isolation.

Results

An IPV dose elicited blood IgA- and IgG-ASC responses in 84.8 to 94.9% of subjects, respectively. In comparison, a bOPV dose evoked corresponding blood ASC responses in 20.0 to 48.6% of subjects. A significant association was found between IgA- and IgG-ASC responses and serum neutralizing antibody titers for poliovirus type 1, 2, 3 (p<0.001). In the IPV group, α4β7⁺ ASCs accounted for a substantial proportion of IgA-ASCs and the proportion of subjects with a positive α4β7⁺ IgA-ASC response to poliovirus types 1, 2 and 3 was 62.7%, 89.8% and 45.8%, respectively. A significant association was observed between virus excretion and α4β7⁺ IgA^- and/or IgG-ASC responses to poliovirus type 3 among immunized children; however, only a weak association was found for type 1 poliovirus.

Discussion

Our results suggest that virus-specific blood ASCs, especially for type 3 poliovirus, can serve as surrogate of mucosal immunity after vaccination. Further studies are needed to evaluate the duration of such memory responses and to assess the programmatic utility of this whole blood-based mucosal ASC testing for the polio eradication program.     

The antibody response of seronegative infants to inactivated poliovirus vaccine of enhanced potency

The immunogenic efficacy of inactivated poliovirus vaccine of enhanced potency (IPV-E), containing 40, 8 and 32 D-antigen units of types 1, 2 and 3, respectively, was evaluated in tritypic seronegative infants. Eighty infants aged six to 45 weeks, with no antibody detectable at a 1 : 4 dilution, were given two doses of a quadruple vaccine containing diphtheria-pertussis-tetanus (DPT) vaccine and IPV-E at intervals of four weeks (37 infants, group 1) or eight weeks (43 infants, group 2) between doses. All infants of group 2 responded with antibody to the three types of polioviruses. In group 1, all responded to types 1 and 3 antigens but only 36 responded to type 2. Antibody titres were higher in infants immunized at eight week than at four week intervals. Thus, two doses of IPV-E, especially when given eight weeks apart, are sufficient for primary immunization against poliomyelitis. If DPT vaccine of enhanced potency is combined with IPV-E, two doses of such a quadruple vaccine may be sufficient for primary immunization against four diseases; this possibility deserves evaluation.     

Feasibility of quantitative environmental surveillance in poliovirus eradication strategies

The progress of the Global Polio Eradication Initiative is monitored by acute flaccid paralysis (AFP) surveillance supplemented with environmental surveillance in selected areas. To assess the sensitivity of environmental surveillance, stools from (re)vaccinated elderly persons with a low seroprevalence and from wastewater were concurrently collected and analyzed in the Netherlands over a prolonged period of time. A total number of 228 healthy individuals with different levels of immunity were challenged with monovalent oral polio vaccine serotype 1 or 3. Poliovirus concentrations were determined by the titration of fecal suspensions on poliovirus-sensitive L20B cells and of sewage concentrates by L20B monolayer plaque assay. Almost half of the individuals (45%) shed poliovirus on day 3 after challenge, which peaked (57%) on day 8 with an average poliovirus excretion of 1.3 × 10(5) TCID(50) per g of feces and gradually decreased to less than 5% on day 42. The virus concentrations in sewage peaked on days 6 to 8 at approximately 100 PFU per liter, remained high until day 14, and subsequently decreased to less than 10 PFU per liter on day 29. The estimated poliovirus concentration in sewage approximated the measured initial virus excretion in feces, within 1 log(10) variation, resulting in a sensitivity of detection of 100 infected but mostly asymptomatic individuals in tens of thousands of individuals. An additional second peak observed in sewage may indicate secondary transmission missed by enterovirus or AFP surveillance in patients. This enables the detection of circulating poliovirus by environmental surveillance, supporting its feasibility as an early warning system.     

Immunological effectiveness of a dried group-A meningococcal polysaccharide vaccine

The immunological effectiveness of dried group A meningococcal polysaccharide vaccine, developed at the Gabrichevsky Research Institute of Epidemiology and Microbiology, Moscow, for children aged 5-14 years was studied. The intensiveness of the immune response of children to 0.5 ml of the vaccine introduced in a single injection was evaluated by a rise in the level of agglutinating antibodies to group A meningococcal polysaccharide in the sera of the vaccinees 3-4 weeks after immunization with the following optimum doses: 25 micrograms for children aged 5-8 years, 50 micrograms for children aged 9-13 years and 75 micrograms for children aged 14 years and over. The vaccine was shown to be highly immunogenic. Antibodies to group A meningococcal polysaccharide were identified as IgM. These antibodies in a titer of 1:40 and higher could be detected in 90% of the vaccinated children in the younger age group, 7 months after immunization.     

Prevention of mumps in preschool institutions using a live mumps vaccine made from strain L-3

The effectiveness of the emergency vaccinal prophylaxis of epidemic parotitis was studied in 19 children's day-care centers. As revealed in this study, the immunological effectiveness of vaccination did not depend on the age of vaccinees, but sharply decreased if live parotitis vaccine contained less than 10,000 HADU50 per immunization dose. After a single administration of the vaccine 91.1 +/- 0.98% of children were found to produce mumps antibodies. The immunization of children with live parotitis vaccine prepared from strain l-3 immediately after the first case of parotitis had been registered proved to be a highly effective measure. The coefficient of epidemiological effectiveness was 96.4%.     

Studies on live attenuated mumps vaccine. II. Follow-up study on the efficacy of Biken Vaccine.

Clinical and serological follow-ups were made on 18 children for 3 years and on another 18 children for 4 years, after immunization against mumps by attenuated mumps vaccine; Biken vaccine. To evaluate the protective efficacy of the vaccine, matched controls were studied during the same period. Serological examinations revealed that 77% of the vaccinees and 93% of the controls were infected with mumps after close contacts with mumps patients. Regular mumps was contracted by 88% of the controls, but none of the vaccinees. There was no substantial decrease in the antibody titers in unexposed vaccinees after vaccination.     

Structural and antigenic variation of the structural protein VP3 in serotype 1 poliovirus isolated from vaccinees

High resolution two-dimensional PAGE was used to analyse protein variation among serotype 1 poliovirus isolates. Viruses isolated from patients with recent histories of vaccination with live attenuated poliovirus were compared with prototype serotype 1 poliovaccine. The nonvaccine Mahoney and Brunenders strains of serotype 1 poliovirus were also analysed. The overall protein profile was conserved but the structural protein VP3 varied in its net charge among the viruses. Eight out of 14 clinical virus isolates had VP3 with a net basic charge identical to serotype 1 polio vaccine, whereas the remaining clinical isolates had an acidic VP3 similar to the nonvaccine type 1 strains. The altered VP3 mobility correlated with a change in antigenicity as determined by monoclonal antibodies directed to the neutralization site located on VP3. The data clearly illustrated the suitability of two-dimensional PAGE in analysing protein mutations in attenuated vaccine virus excreted by vaccinees.     

Environmental Surveillance of Poliovirus in Sewage Water around the Introduction Period for Inactivated Polio Vaccine in Japan

Environmental virus surveillance was conducted at two independent sewage plants from urban and rural areas in the northern prefecture of the Kyushu district, Japan, to trace polioviruses (PVs) within communities. Consequently, 83 PVs were isolated over a 34-month period from April 2010 to January 2013. The frequency of PV isolation at the urban plant was 1.5 times higher than that at the rural plant. Molecular sequence analysis of the viral VP1 gene identified all three serotypes among the PV isolates, with the most prevalent serotype being type 2 (46%). Nearly all poliovirus isolates exhibited more than one nucleotide mutation from the Sabin vaccine strains. During this study, inactivated poliovirus vaccine (IPV) was introduced for routine immunization on 1 September 2012, replacing the live oral poliovirus vaccine (OPV). Interestingly, the frequency of PV isolation from sewage waters declined before OPV cessation at both sites. Our study highlights the importance of environmental surveillance for the detection of the excretion of PVs from an OPV-immunized population in a highly sensitive manner, during the OPV-to-IPV transition period.     

Immunoprophylaxis of poliomyelitis in Ukraine with the use of inactivated vaccine

In connection with the cessation of the circulation of "wild" poliovirus on the territory of the European region, including Ukraine, the strategy of the vaccinal prophylaxis of poliomyelitis is reviewed. Its main aims are the creation of a high level of the specific protection of the population, the prophylaxis of vaccine-associated paralytic poliomyelitis and a decrease in the intensity of the circulation vaccine polioviruses. These aims may be achieved only by the inclusion of vaccinations with inactivated poliomyelitis vaccine (IPV) into the immunization schedule. IPV "Imovax Polio" produced by the firm "Aventis Pasteur" (France) has been shown to have low reactogenicity and high effectiveness, especially with respect to type 3 poliovirus, under the conditions of Ukraine. On the basis of our studies all children, starting from the age of 3 months, are recommended to be vaccinated first with two injections of IPV, followed by further immunization with oral vaccine.     

Safety and immunogenicity of a monovalent MF59®-adjuvanted A/H1N1 vaccine in HIV-infected children and young adults

BackgroundThis Phase IV study evaluated the safety and immunogenicity of a two-dose, MF59^®-adjuvanted (Novartis Vaccines, Marburg, Germany), monovalent, A/H1N1 pandemic influenza vaccination schedule in Human Immunodeficiency Virus (HIV) positive children and young adults.MethodsA total of 83 children infected with HIV-1, and 37 non-immunocompromised, age-matched controls were enrolled. All participants received two vaccine doses administered three weeks apart. Antibody responses were assessed by haemagglutination assay at baseline, three weeks after each vaccine dose, and six months after immunization. Vaccines were evaluated according to European influenza vaccine licensure criteria.ResultsThe investigational vaccine was well tolerated. After the first vaccine dose, seroconversion rates were significantly lower in HIV-positive patients (60%) than controls (82%), with GMTs of 419 and 600, respectively. No significant differences in seroconversion rates were observed between the two study groups in response to the second vaccine dose. Persisting antibody titers were similar for both HIV-positive and non-infected controls, six months after immunization.ConclusionOne dose of MF59-adjuvanted vaccine was sufficient to provide adequate levels of seroprotection against A/H1N1 influenza disease in HIV-positive children. However, a two-dose vaccination schedule may be optimal for this population.     

Intestinal trypsin can significantly modify antigenic properties of polioviruses: implications for the use of inactivated poliovirus vaccine.

It was recently reported that the intestinal protease trypsin cleaves in vitro the VP1 protein of type 3 poliovirus at antigenic site 1 (J. P. Icenogle, P. D. Minor, M. Ferguson, and J. M. Hogle, J. Virol. 60:297-301, 1986). We found that incubation of purified or crude type 3 poliovirus preparations with specimens of human intestinal fluid brings about a similar change in the virion structure. Sera from children immunized solely with the regular inactivated poliovirus vaccine (IPV) neutralized trypsin-cleaved Sabin 3 virus poorly, if at all, despite moderate levels of antibodies to the corresponding intact virus. Sera containing very high titers of the intact virus also neutralized the trypsin-cleaved virus but at a relatively weaker capacity. Most sera from older persons who may have been exposed to a natural poliovirus infection before the introduction of the poliovirus vaccines as well as sera from children infected with type 3 poliovirus during the recent outbreak in Finland were able to neutralize the trypsin-cleaved type 3 polioviruses. Serum specimens collected 1 month after a single dose of live poliovirus vaccine from children previously immunized with IPV were able to neutralize the trypsin-cleaved virus as well. During natural infection and after live poliovirus vaccine administration polioviruses are exposed to proteolytic enzymes in the gut. Our results may offer an alternative explanation for the relatively weak mucosal immunity obtained with IPV. Improvement of IPV preparations by incorporation of trypsin-treated type 3 polioviruses in the vaccine should be studied.     

A long-term follow-up study on the efficacy of further attenuated live measles vaccine, Biken CAM vaccine

Antibody persistence was measured in 39 children in an open community 12-13 years after immunization against measles with further attenuated live vaccine, Biken CAM. Serum samples of the children taken every two or three years after vaccination had higher, lower, or the same HI antibody titers as those in samples taken 6 weeks after vaccination. These differences reflected a decrease in the titer in some children and subclinical natural reinfection in others. However, all the children still retained detectable antibody in 12 or 13 years after vaccination, indicating long-term persistence of immunity after immunization with Biken CAM vaccine. For evaluation of the protective efficacy of the vaccine, matched controls were studied during the same period. Serological examination revealed that 97.5% of the controls were infected with measles and contracted the disease. In contrast, none of the vaccinees developed clinical infection after close contact with measles patients.     

Excretion of wild-type and vaccine-derived poliovirus in the feces of poliovirus receptor-transgenic mice

The emergence of circulating vaccine-derived poliovirus (cVDPV) strains in suboptimally vaccinated populations is a serious threat to the global poliovirus eradication. The genetic determinants for the transmissibility phenotype of polioviruses, and in particularly of cVDPV strains, are currently unknown. Here we describe the fecal excretion of wild-type poliovirus, oral polio vaccine, and cVDPV (Hispaniola) strains after intraperitoneal injection in poliovirus receptor-transgenic mice. Both the pattern and the level of fecal excretion of the cVDPV strains resemble those of wild-type poliovirus type 1. In contrast, very little poliovirus was present in the feces after oral polio vaccine administration. This mouse model will be helpful in elucidating the genetic determinants for the high fecal-oral transmission phenotype of cVDPV strains.     

Changes in population dynamics during long-term evolution of sabin type 1 poliovirus in an immunodeficient patient

The evolution of the Sabin strain of type 1 poliovirus in a hypogammaglobulinemia patient for a period of 649 days is described. Twelve poliovirus isolates from sequential stool samples encompassing days 21 to 649 after vaccination with Sabin 1 were characterized in terms of their antigenic properties, virulence in transgenic mice, sensitivity for growth at high temperatures, and differences in nucleotide sequence from the Sabin 1 strain. Poliovirus isolates from the immunodeficient patient evolved gradually toward non-temperature-sensitive and neurovirulent phenotypes, accumulating mutations at key nucleotide positions that correlated with the observed reversion to biological properties typical of wild polioviruses. Analysis of plaque-purified viruses from stool samples revealed complex genetic and evolutionary relationships between the poliovirus strains. The generation of various coevolving genetic lineages incorporating different mutations was observed at early stages of virus excretion. The main driving force for genetic diversity appeared to be the selection of mutations at attenuation sites, particularly in the 5' noncoding region and the VP1 BC loop. Recombination between virus strains from the two main lineages was observed between days 63 and 88. Genetic heterogeneity among plaque-purified viruses at each time point seemed to decrease with time, and only viruses belonging to a unique genotypic lineage were seen from day 105 after vaccination. The relevance of vaccine-derived poliovirus strains for disease surveillance and future polio immunization policies is discussed in the context of the Global Polio Eradication Initiative.     

Assessment of the prophylactic effectiveness of an inactivated influenza vaccine by immunizing schoolchildren in the springtime

To evaluate the prophylactic effectiveness of influenza inactivated chromatographic vaccine, limited epidemiological observations were made on school children aged 11-14 years in Leningrad, in the autumn of 1981 and the spring of 1982. For immunization, made in a single administration, the vaccine composed of A (H3N2) + +A (H1N1) and containing 3.0-3.4 micrograms of hemagglutinin of each component per 0.2 ml of the preparation was used. Altogether 6928 schoolchildren were under observation; of these, 3686 children were immunized and 3242 children received placebo. The results of questioning and the analysis of morbidity rate among the schoolchildren, both immunized and receiving placebo, showed the safety and low reactogenicity of the vaccine irrespective of the time of the immunization campaign. The immunogenic potency of the preparation, as indicated by all observation results, proved to be higher in spring, than in autumn. The data thus obtained indicate that children immunized in spring were better protected and retained a higher level of protection within 12 months after immunization. The shift of the time of the immunization campaign from autumn to spring increased the immune layer in the groups of children by 16.5%. In 10 months after spring immunization the morbidity rate in influenza and acute respiratory diseases among the vaccinees was found to decrease 1.7 times.