Quantitative detection of neutralizing antibodies against polioviruses and non-polio enteroviruses (NPEV) using an automated microneutralization assay: a seroepidemiologic survey

Polio type 2 and 3 eradication: Relevance to the immunity status of individuals living in Germany, 2005-2020

Since October 2019, poliovirus type 3 (PV3) has been certified as globally eradicated, and further laboratory use of PV3 will be restricted according to the WHO Polio Eradication Initiative and containment measures. To examine a possible gap in PV3 immunity and a lack of immunity against poliovirus type 2 (PV2), which was already declared as eradicated in 2015, neutralising antibodies against polioviruses (PV) of individuals living in Germany (n = 91,530 samples; mainly outpatients (≈90%) who received immune status testing) were investigated from 2005 to 2020 (age distribution: <18 years 15.8%, 18-64 years 71.2% and ≥65 years 9.5% for 2005-2015; <18 years 19.6%, 18-64 years 67% and ≥65 years 11.5% for 2016-2020). The results showed that the proportion of sera exclusively lacking antibodies against PV3 was 10.6% in 2005-2015 and 9.6% in 2016-2020 and against PV2 2.8% in 2005-2015. As there is decreased protection against PV3 and to detect potential antigenically (immune escape) variant PVs not covered by used vaccines, we recommend continued testing of PV1 and PV3.

Seroepidemiology of echovirus 30 in Korean children

BACKGROUND

Although aseptic meningitis associated with echovirus type 30 has emerged as a global public health concern, no data have been reported on Children's immune status against echovirus type 30. The current study aimed to investigate the seropositivity among Korean children for antibodies against echovirus 30.

METHODS

Two hundred and fifty residual serum samples were collected at St. Paul's Hospital. Individuals were categorized by age into four groups: group 1 (3 months-2 years), group 2 (3-6 years), group 3 (7-10 years) and group 4 (11-15 years). Neutralizing antibodies against echovirus 30 were measured.

RESULTS

Seroprotective neutralizing antibodies against echovirus 30 were detected in 129 (49%) individuals. Seropositivity rates were 23%, 48%, 55% and 73% in groups 1-4, respectively. For antibody titers, 1:256-1:512 was the highest neutralizing antibody titer range in group 2, while 1:1024-1:2048 in group 3 and 4. Among the seropositive individuals in group 3 and 4, 6% and 12% had neutralizing antibody titers of 1:2048, respectively.

CONCLUSIONS

The seropositivity rate increased significantly with age. The distribution of neutralizing antibody titers varied by age group, and higher ranges of neutralizing antibody titers were observed in higher age groups. These findings suggest high susceptibility to echovirus 30 infection in children younger than 2 years old. Echovirus 30 infection in childhood may have contributed to increased neutralizing antibody titers with age.

Seroepidemiology of enterovirus D68 infection in China

Human enterovirus 68 (EV-D68) is a rarely reported virus that has been linked to respiratory disease. In recent years, reports about EV-D68 infection have markedly increased worldwide. However, the epidemiological features of this emerging infection are not well understood. To evaluate the emerging EV-D68 epidemic, we isolated the circulating viral strain and investigated the seroprevalence of neutralizing antibodies (NAbs) in Beijing between 2004 and 2011. We found that the titers of EV-D68 NAbs were generally low in all age groups in sampled populations in 2004 but significantly higher in 2009. From 2007 to 2011, the NAbs against EV-D68 significantly increased over time. These findings indicate that EV-D68 has spread widely in the Chinese population in recent years, although only a limited number of cases were reported.

Is EU/EEA population protected from polio?

The WHO European Region has been declared polio-free since 2002. By 2010, inactivated polio vaccine (IPV) was the only polio vaccine in use in the EU/EEA for the primary vaccination of children. A systematic review of the literature on polio seroprevalence studies, complemented by the analysis of available vaccine coverage data, has been carried out with the aim of assessing the level of protection against polio in the European population. A total of 52 studies, with data from 14 out of the 31 EU/EEA countries, were included in the analysis. This systematic review shows that, overall, seroprevalence for PV1 and PV3 is high in most countries, although seroimmunity gaps have been detected in several birth cohorts. In particular, relatively low immunity status was found in some countries for individuals born in the 60's and 70's. Discrepancies between reported vaccination coverage and immunity levels have been also highlighted. Countries should make sure that their population is being vaccinated for polio to reduce the risk of local poliovirus transmission in case of importation. Moreover, assessing immunity status should be priority for those traveling to areas where wild polioviruses are still circulating.

A national cross-sectional study for poliovirus seroprevalence in the Republic of Korea in 2012: implication for deficiency in immunity to polio among middle-aged people

Background

A worldwide poliomyelitis eradication program was initiated in 1988; however, strains of wild poliovirus (WPV) are still endemic in some countries. Until WPV transmission is eradicated globally, importation and outbreaks of WPV are alarming possibilities. This study is the first report to document the polio immunity after 2004, when an inactivated polio vaccine (IPV) was introduced in the Republic of Korea.

Methods

A total of 745 serum samples from randomly selected patients ranging from 6 to 84 years of age were used for neutralization tests, performed in the World Health Organization polio national reference laboratory.

Results

Among the 745 tested sera, 439 (58.9%) were seropositive and 19 (2.6%) were seronegative to all PV serotypes. In all age groups, PV3 showed the lowest level of seroprevalence, at 509 cases (68.3%), compared to 616 (82.7%) for PV1 and 685 (91.9%) for PV2. In the 6–10-year age group, which included IPV-immunized children, the highest seropositive rate was observed and the difference in seroprevalence between PV3 and other serotypes was the lowest compared to the other age groups immunized with oral PV vaccines (OPV). In addition, the seronegative rates of all three PV types in children aged 6–10 in this study were found to be lower than those in OPV-immunized children reported in a previous study from the Republic of Korea. Meanwhile, middle-aged subjects (41–60 years) had the lowest seroprevalence and geometric mean titer.

Conclusions

This study indicates a deficiency in immunity to PV in middle-aged individuals, and low seroprevalence to PV3 in all age groups. In addition, due to the ongoing risk of importing PV, middle-aged people should consider PV vaccination before visiting a PV-endemic country. Our findings provide data to assist those involved in deciding future national polio vaccination strategies for the maintenance of a polio-free status in Korea.

Poor immunity status against poliomyelitis in medical students: a semi-anonymous study

In spite of almost complete eradication, poliomyelitis continues to be a global threat even in non-endemic countries due to the ever-increasing international travel activities. Health care workers are at a special risk in acquiring pathogens from travelers returning from endemic countries. Polio vaccines are fairly well accepted throughout the German population. Yet, laboratory controls for successful immunization are carried out only sporadically in the general population, and not even the medical staff are routinely tested for polio immunity. The present study was initiated in order to assess the immunity status of young people at the very beginning of their career in clinical medicine. Within their first clinical semester, all students are supposed to undergo an obligatory health check in our Occupational Medicine Unit. A blood sample is taken and sent under a personal code to our diagnostic laboratories for virus serology, and for cryoconservation of residual serum, if available. Within the periods 2004–2006 and 2008–2010, we analyzed sera from 424 and 427 individuals, respectively, for anti-polio types 1, 2, 3 antibodies by a microneutralization assay. In the latest study period, there was a slight increase in the rate of fully protected persons: 63.9 % triple-seropositivity versus 57.1 % in the period 2004–2006. By the end of the second clinical semester, students with low or negative antibody levels (1:<10) were informed, and a (booster) vaccination was recommended.

Deficiency of immunity to poliovirus type 3: a lurking danger?

Background

Europe was certified to be polio-free in 2002 by the WHO. However, wild polioviruses remain endemic in India, Pakistan, Afghanistan, and Nigeria, occasionally causing polio outbreaks, as in Tajikistan in 2010. Therefore, effective surveillance measures and vaccination campaigns remain important. To determine the poliovirus immune status of a German study population, we retrospectively evaluated the seroprevalence of neutralizing antibodies (NA) to the poliovirus types 1, 2 and 3 (PV1, 2, 3) in serum samples collected from 1,632 patients admitted the University Hospital of Frankfurt am Main, Germany, in 2001, 2005 and 2010.

Methods

Testing was done by using a standardized microneutralization assay.

Results

Level of immunity to PV1 ranged between 84.2% (95%CI: 80.3-87.5), 90.4% (88.3-92.3) and 87.5% (85.4-88.8) in 2001, 2005 and 2010. For PV2, we found 90.8% (87.5-90.6), 91.3% (89.3-93.1) and 89.8% (88.7-90.9), in the same period. Seroprevalence to PV3 was 76.6% (72.2-80.6), 69.8% (66.6-72.8) and 72.9% (67.8-77.5) in 2001 and 2005 and 2010, respectively. In 2005 and 2010 significant lower levels of immunity to PV3 in comparison to PV1 and 2 were observed. Since 2001, immunity to PV3 is gradually, but not significantly decreasing.

Conclusion

Immunity to PV3 is insufficient in our cohort. Due to increasing globalization and worldwide tourism, the danger of polio-outbreaks is not averted - even not in developed countries, such as Germany. Therefore, vaccination remains necessary.

Hand, foot and mouth disease: seroprevalence of Coxsackie A16 and Enterovirus 71 in Germany

Coxsackie A16 (CA16) and Enterovirus 71 (EV71) are members of the picornaviridae family and are associated with hand, foot and mouth disease (HFMD), in rare cases also to acute neurological diseases. HFMD outbreaks have been reported from many parts of the world, especially Southeast Asia. The objective of the study was to analyze CA16 and EV71 seroepidemiologically in the population of Frankfurt/M., Germany. A total of 696 individuals (349 males and 347 females, divided into seven different age groups, 1-4, 5-9, 10-14, 15-19, 20-39, 40-59 and >60 years) were tested for serum antibodies against CA16 and EV71 by the use of a microneutralization test. Sera were collected at the Frankfurt university hospital from patients suffering from other diseases between March and September 2006. CA16 and EV71 infections were observed to be widely present in the population. The age-adjusted seroprevalence for individuals >or=1 year was found to be 62.9% for CA16 and 42.8% for EV71 without a gender-specific significant difference. Only 12.0 and 27.0% of the children aged 1-4 had antibodies to EV71 and CA16, respectively - indicating that 88 and 73% of the children in this age group were susceptible to the infection. A total of 213 individuals (30.6%) was seropositive for both viruses, 303 (43.5%) showed neutralizing antibodies (NtAb) to at least one of the two viruses. A total of 180 individuals (25.9%) revealed no antibodies. High CA16 and EV71 antibody titers were found especially in the age group of the 10- to 14-year-olds, without gender-specific difference. The seroprevalence study demonstrates a common spread of CA16 and EV71 in Germany, but a relatively high susceptibility of the younger population to CA16 and EV71. Obviously, the manifestation rate, i.e., distinct disease of these infections is low.

Seroprevalence of vaccine preventable and blood transmissible viral infections (measles, mumps, rubella, polio, HBV, HCV and HIV) in medical students

In the course of clinical training medical students are in particular exposed to infectious diseases. Therefore, the present study was performed to investigate the immunity status of 223 medical students in their first clinical semester to job-related diseases. Specific serological antibody testing of hepatitis B-virus (HBV), hepatitis C-virus (HCV), human immunodeficiency virus (HIV), varicella zoster- (VZV), measles-, mumps-, rubella and polioviruses' type 1, 2 and 3 were performed. The results yielded, that 69.5% of the students had an anti-HBs-level > or =10 IU/l and 54.7% > or =100 IU/l. Neither HCV infection nor HIV infection were found, but one student showed an active HBV infection. Virus specific immunity rates were found in 91.5% for measles, 80.3% for mumps, 90.1% for rubella and 96.9% for varicella. Furthermore the medical students demonstrated neutralizing antibodies to polioviruses: 95.1% (type 1), 96.9% (type 2) and 70% (type 3). 68.2% had antibodies (titer 1:> or =10) against all three virus types. The partly significant gaps of immunity in the students need to be closed prior to the first contact with patients.

Antigenic sites of coxsackie A9 virus inducing neutralizing monoclonal antibodies protective in mice

A panel of murine IgG monoclonal antibodies (MAbs) was produced against coxsackievirus A9 (CAV9). Fifty-nine MAbs reactive in ELISA with purified CAV9 were identified. Eighteen of them could efficiently inhibit infection by CAV9 but not coxsackieviruses B. Neutralization-resistant CAV9 variants to four different MAbs were isolated and tested for resistance to neutralization by other MAbs of the panel. Three groups of reactivity including 10, 7, and 1 MAbs were thus identified. Sequencing of neutralization-escape virus mutants showed that neutralization by one MAb group was affected by change of VP3 amino acids 62 or 69. For the second group of reactivity, mutations included amino acids 154 or 165 of VP2. The only MAb of the third group selected for a change at residue 70 of VP2. Protection studies in a newborn mouse model of myositis suggested that either epitopes in VP2 or in VP3 mediate protection from CAV9 infection in vivo.

Epidemiological analysis of immunity to poliovirus after termination of an era of vaccination with OPV in Germany. An analysis of the German Association Against Viral Diseases (DVV)

The global eradication of poliomyelitis by the year 2000 is an objective of the World Health Organization (WHO). Since 1998, after a period of 37 years of vaccination using live oral poliovirus vaccine (OPV), single use of inactivated poliovirus vaccine (IPV) has been recommended in Germany. The present epidemiological analysis shows the immunity of 3474 patients to poliovirus types 1, 2 and 3 by using a microneutralization assay. A non-age-specific evaluation of antibodies seroprevalence to poliovirus type 1 remained 81% and similarly, for poliovirus type 2 86% while the poliovirus type 3 decreased from 78% in 1990-1992 to 68% in 1997. In the important group of children aged 5-14 years, the prevalence of antibodies to type 3 decreased clearly from 74% in 1990 to 47% in 1997. The relatively favorable level of seroprevalence of antibody to type 2 in children aged 1-4 years (89%) indicates a good acceptance of vaccination programs. However, a good immunity to all 3 serotypes was not achieved by primary vaccination. The objective of a global eradication of poliomyelitis has not yet been be achieved. Great problems still exist, especially in Africa and Asia.

Immunity status against poliomyelitis in persons 13-14 years old living in Rome

The immunity against poliomyelitis in 1000 subjects 13-14 years old was evaluated. Neutralizing antibodies against poliovirus type 1, 2 and 3 were detected in 97.6%, 95.8% and 70% of samples, respectively. 3/1000 (0.3%) subjects were simultaneously seronegative to the three types. WHO does not suggest a protective level of International Units (IU), but our data indicate that such level is 0.45 IU for polio type 1, 0.65 IU for the type 2 and 0.138 for the type 3. A booster dose of vaccine in adolescence to ensure personal and herd immunity is recommended.

Evaluation of a new automated microneutralization assay for the quantitative detection of neutralizing antibodies against enteroviruses

An automated microneutralization assay for the quantitative detection of neutralizing antibodies (NA) against polioviruses and non-polio enteroviruses (NPEV) using a pipetting roboter (Tecan RSP 5072) was established and compared to the conventional manually performed test procedure. The qualitative neutralizing antibody detection was not significantly influenced by the assay system (manual or automated assay). Concerning the quantitative antibody detection, two-fold titre differences between the two test systems were observed in only 2.3% of the 260 serum samples investigated. The intra-assay and inter-assay variability of the quantitative detection of neutralizing antibodies using the automated assay proved to be very low. The quantitative detection of neutralizing antibodies using an automated pipetting robot permitted the testing of large numbers of samples within a shorter period and with less labour intensity as compared to the manually performed assay. Therefore it represents a valuable alternative to the conventional microneutralization test, especially for the serodiagnosis of non-polio enterovirus infections in large sample collectives, assessment of immunity to polioviruses and for seroepidemiological surveys.