Evaluation of a poliovirus-binding inhibition assay as an alternative to the virus neutralization test

In-Vitro Inactivation of Sabin-Polioviruses for Development of Safe and Effective Polio Vaccine

After years of global collaboration; we are steps away from a polio-free world. However, the currently conventional inactivated polio vaccine (cIPV) is suboptimal for the post eradication era. cIPV production cost and biosafety hazards hinder its availability and coverage of the global demands. Production of IPV from the attenuated Sabin strains (sIPV) was an ideal solution and scientists work extensively to perfect a safe, effective and affordable sIPV. This study investigated the ability of hydrogen peroxide (H₂O₂), ascorbic acid (AA) and epigallocatechin-3-gallate (EGCG) as alternatives for Formaldehyde (HCHO) to inactivate Sabin-polioviruses strains for sIPV production. Sabin-polioviruses vaccine strains were individually treated with AA, EGCG or H₂O₂ and were compared to HCHO. This was investigated by determination of the inactivation kinetics on HEP_2C cells, testing of D-antigen preservation by ELISA and the immune response in Wistar rats of the four vaccine preparations. H₂O₂, AA and EGCG were able to inactivate polioviruses within 24 h while HCHO required 96 h. Significant high D-antigen levels were observed using AA, EGCG and H₂O₂ compared to HCHO. Rat sera tested for neutralizing antibodies showed comparable results. These findings support the idea of using these inactivating agents as safe and time- saving alternatives for HCHO to produce sIPV.

Seroprevalence of Poliomyelitis Antibodies Among Children Aged 1 to 4 Years Old and Factors Associated With Poliovirus Susceptibility; Mexican Health and Nutrition Survey, 2012

Background

An essential component of the “Polio Eradication and Endgame Strategic Plan 2013–2018” is the evaluation of population immunity. Mexico introduced the inactivated polio vaccine (IPV) into its routine immunization schedule in 2007 but continued to give trivalent oral polio vaccine OPV twice a year during National Health Weeks through 2016.

Methods

To describe the seroprevalence of poliomyelitis among children one to four years old in Mexico and analyze risk factors for susceptibility. We detected antibodies to poliovirus type 1 by microneutralization test in 966 serum samples randomly selected from the National Health and Nutrition Survey, 2012. We assessed variables associated with susceptibility using multivariable logistic regression.

Results

The overall weighted seroprevalence of the general population was 98.39% (95% confidence interval [CI] 96.76–99.21). We found significant differences of prevalence according to age (94.39%, 95% CI 87.56–97.58; 99.02%, 95% CI 95.68–99.79; 99.82%, 95% CI 98.77–99.98; and 100% among children 1, 2, 3, and 4 years old respectively) and number of IPV doses (96.91%, 95% CI 90.55–99.44; 100%; 97.85%, 95% CI 94.46–99.18; and 99.92%, 95% CI 99.45–99.98 for 1 2, 3, and 4 number of doses, respectively). Multivariate analyses showed that susceptibility was associated with younger age, fewer doses of IPV, and certain socioeconomic levels.

Conclusions

Overall seroprevalence was high. However, we found susceptible children among younger ages and children with fewer or unknown IPV doses belonging to certain socioeconomic strata. Results are relevant for countries transitioning from OPV to IPV and underline the importance of achieving high coverage with IPV.

Seroprevalence and vaccination coverage of vaccine-preventable diseases in perinatally HIV-1-infected patients

BACKGROUND

Even in the era of highly active antiretroviral therapy (HAART), HIV-infected subjects are at higher risk of complications from vaccine-preventable diseases than those uninfected. The current international guidelines strongly recommend that these patients should receive all the routine childhood vaccinations. Although these children represent an appropriate target for immunization, the available data indicate suboptimal coverage rates.

METHODS

To evaluate seroprotection/seropositivity rates and vaccination coverage against the common vaccine-preventable diseases, all patients with vertically transmitted HIV-1 infection who attended San Martino Hospital were enrolled. Blood samples were collected for testing antibodies against diphtheria, tetanus, hepatitis A and B viruses by Enzyme-Linked ImmunoSorbent Assay and polioviruses by microneutralization test. In order to assess immunization coverage, retrospectively was recorded the vaccination history collecting data from Regional Immunization Database.

RESULTS

A total of 39 perinatally HIV-1 infected patients were included in the study. At the time of serum was obtained, the mean age was 18,1 years (range: 6-28). The median CD4+ T-lymphocyte count was 702 cells/mm(3) (2-1476 cells/mm(3)). Twenty-nine (74.4%) patients were found with HIV RNA load < 50 copies/mL. The proportion of subjects with protective anti-tetanus and anti-HBs were 43.6% and 30.8%, respectively. Seroprotection rates about 20% against rubella and measles were found, less than 20% against all the other antigens investigated. In particular, all patients resulted susceptible to mumps. High immunization rates were observed for polio and HBV (100% and 92.3%, respectively) and suboptimal for diphtheria-tetanus (84.6%). For the other recommended vaccines the rates were generally low. None of the patients received varicella vaccine doses.

CONCLUSIONS

As in the HAART era the vertically acquired HIV infection has become a chronic treatable disease, the vaccine-induced long-term protection plays an increasingly significant role; despite good initial response to primary vaccination, subsequent decline and loss of detectable antibodies may be prevented by additional strategies for booster doses of vaccines in adolescents and young adults.

Robustness against serum neutralization of a poliovirus type 1 from a lethal epidemic of poliomyelitis in the Republic of Congo in 2010

In 2010, a large outbreak of poliomyelitis with unusual 47% lethality occurred in Pointe Noire, Republic of Congo. Vaccine-mediated immunity against the outbreak virus was never investigated. A wild poliovirus 1 (WPV1) isolated from a fatal case (termed PV1-RC2010) showed a previously unknown combination of amino acid exchanges in critical antigenic site 2 (AgS2, VP1 capsid protein positions 221SAAL → 221PADL). These exchanges were also detected in an additional 11 WPV1 strains from fatal cases. PV1-RC2010 escaped neutralization by three different mAbs relevant for AgS2. Virus neutralization was tested in sera from fatal cases, who died before supplementary immunization (n = 24), Gabonese recipients of recent oral polio vaccination (n = 12), routinely vaccinated German medical students (n = 34), and German outpatients tested for antipoliovirus immunity (n = 17) on Vero, human rhabdomyosarcoma, and human epidermoid carcinoma 2 cells. Fatal poliomyelitis cases gave laboratory evidence of previous trivalent vaccination. Neutralizing antibody titers against PV1-RC2010 were significantly lower than those against the vaccine strain Sabin-1, two genetically distinct WPV1s isolated in 1965 and 2010 and two genetically distinct vaccine-derived PV strains. Of German vaccinees tested according to World Health Organization protocols, 15-29% were unprotected according to their neutralization titers (<1:8 serum dilution), even though all were protected against Sabin-1. Phylogenetic analysis of the WPV1 outbreak strains suggested a recent introduction of virus progenitors from Asia with formation of separate Angolan and Congolese lineages. Only the latter carried both critical AgS2 mutations. Antigenetically variant PVs may become relevant during the final phase of poliomyelitis eradication in populations with predominantly vaccine-derived immunity. Sustained vaccination coverage and clinical and environmental surveillance will be necessary.

ELISA as a possible alternative to the neutralization test for evaluating the immune response to poliovirus vaccines

This review describes several enzyme-linked immunosorbent assay (ELISA) techniques proposed to replace the neutralization test for detecting neutralization-relevant antibodies to polioviruses in recipients of inactivated poliovirus vaccine and oral poliovirus vaccine, and for seroepidemiologic studies. Comparisons of results from ELISA and the neutralization test suggest that ELISA variants, based on the principle of blocking or binding inhibition that emulate the neutralization test, might offer an alternative to the neutralization test. However, to replace the neutralization test with ELISA would first require extensive studies with very large numbers of serum samples, including sera having low titers of neutralizing antibodies, in order to obtain reliable and statistically sound validation.

Vitamin a supplementation does not affect infants' immune responses to polio and tetanus vaccines

It has been suggested that administering vitamin A with the measles vaccine may reduce the vaccine's immunogenicity. This trial examined the effect of supplementing vitamin A during the early months of life on infants' immune responses to tetanus and polio vaccines. Young infants (n = 1085) were enrolled and individually randomized into 1 of 4 groups in a factorial, double-blind, placebo-controlled trial. Three vitamin A supplementation strategies were investigated: 1) supplementation of breast-feeding mothers with 60 mg retinol equivalent (RE) vitamin A within 4 wk of delivery; 2) Expanded Program on Immunization (EPI)-linked supplementation of infants with 7.5 mg RE vitamin A at 6, 10, and 14 wk; and 3) combined mother and child supplementations. A 4th group in which mother and child were given placebos served as controls. Blood samples were collected from each child at 6 wk and 6 mo of age to measure antipolio antibody titer, antitetanus toxoid antibodies, and avidity of antibodies to tetanus. Of the infants randomized into the 4 arms of the study, 767 (71%) completed follow-up at 6 mo of age. Follow-up rates were similar in all 4 arms (69-72%, P = 0.8). Antibody titers were relatively high in all 4 groups at both 6 wk and 6 mo of age, with no differences among the groups. We found no evidence that vitamin A supplementation affects infants' antibody responses to tetanus toxoid or oral polio vaccine delivered at EPI contacts.

Determination of poliovirus-specific IgA in saliva by ELISA tests

This study describes three ELISA methods for detection of immunoglobulin A (IgA) specific to three types of Sabin strains of poliovirus in saliva taken from 70 children aged 6-7 years vaccinated with a full course of oral poliovirus vaccine (OPV). Of the three ELISA methods (conventional IgA ELISA and two new methods described in this communication, the alpha-capture ELISA and Inhibition ELISA), alpha-capture ELISA demonstrated the highest sensitivity, with all saliva samples testing positive for Sabin poliovirus strains specific IgA antibodies of 1-3 types. Of 62 available alpha-capture ELISA positive saliva samples, all were also positive by the inhibition ELISA, and a significant correlation was found between the results. Fifty-two available saliva samples were screened by the three ELISA tests with positive results, and a significant correlation was found between the alpha-capture ELISA and the IgA ELISA; the correlation between the IgA ELISA and inhibition ELISA was not significant. The results of this study suggest that determination of Sabin poliovirus-specific IgA in human saliva by the ELISA techniques (especially by the novel alpha-capture ELISA) can be used reliably for evaluation of mucosal immunity in large groups of people immunized with poliovirus vaccines and for epidemiological studies.

Probiotic bacteria stimulate virus-specific neutralizing antibodies following a booster polio vaccination

BACKGROUND

Orally ingested probiotic bacteria may modulate the immune response and increase antibody titers against enteric infections by bacteria or viruses. Even though positive effects of probiotics on respiratory tract infections have been reported, overall only few studies have examined effects on virus infections concerning organs other than the gastrointestinal tract.

AIM OF THE STUDY

It was the aim of the study to investigate whether and how probiotics affect the immune response to a standardized enterovirus challenge (polio) and infections not limited to the gastrointestinal tract in healthy adults.

METHODS

In a randomized, controlled and double-blind study 64 volunteers consumed for 5 weeks chemically acidified clotted milk without bacteria or with 10(10)/serving (Lactobacillus rhamnosus ) GG or Lactobacillus acidophilus CRL431 added. In the second week subjects were vaccinated orally against polio 1, 2 and 3. Polio virus neutralizing serum activity, the primary parameter, was determined by the standard neutralization test (WHO) before and three times after vaccination. Polio-specific IgA, IgG and IgM were detected by ELISAs.

RESULTS

Probiotics increased poliovirus neutralizing antibody titers (NT) and affected the formation of poliovirus-specific IgA and IgG in serum. The maximum increase after immunization was about 2, 2.2, or 4-fold higher, respectively, for NT, IgG or, IgA, in volunteers consuming probiotics instead of placebo. No consistent difference was noted between bacterial strains.

CONCLUSIONS

Probiotics induce an immunologic response that may provide enhanced systemic protection of cells from virus infections by increasing production of virus neutralizing antibodies.

Efficacy of donor vaccination before hematopoietic cell transplantation and recipient vaccination both before and early after transplantation

Allogeneic hematopoietic cell transplantation is followed by humoral immunodeficiency. We evaluated whether antibody levels can be improved by recipient vaccination on day -1 and 50 and whether the levels can be further improved by donor vaccination on day -20. A total of 85 patients were randomized or assigned to one of the following strategies of immunization with Streptococcus pneumoniae polysaccharides, Haemophilus influenzae polysaccharide-protein conjugate, tetanus toxoid (protein recall antigen) and hepatitis B surface antigen (protein neo-antigen): (1) donor on day -20, recipient on days -1, +50 and +365 (D(-20)R(-1,50,365)); (2) donor nil, recipient on days -1, +50 and +365 (D(N)R(-1,50,365)); or (3) donor nil, recipient on day +365 (D(N)R(365)). For H. influenzae and tetanus, IgG levels after grafting were the highest in the D(-20)R(-1,50,365) patients, intermediate in the D(N)R(-1,50,365) patients and the lowest in the D(N)R(365) patients. For S. pneumoniae and hepatitis B, antibody levels appeared to be similar in all three patient groups. The results suggest that for polysaccharide-protein conjugate antigens or protein recall antigens, recipient immunization on days -1 and 50 improves antibody levels and that donor vaccination on day -20 further improves the levels. In contrast, neither recipient immunization on days -1 and 50 nor donor immunization on day -20 appears to be efficacious for polysaccharide antigens and poorly immunogenic protein neo-antigens.

Factors affecting antibody levels after allogeneic hematopoietic cell transplantation

To obtain insight into the mechanism(s) of posttransplantation humoral immunodeficiency, we evaluated factors affecting serum antibody levels against polio, tetanus, Haemophilus influenzae, and Streptococcus pneumoniae in 87 patients. Patients with hematologic malignancies were randomized to receive marrow versus blood stem cells, which contain approximately 10 times more lymphocytes than marrow. Blood stem cell recipients did not have higher antibody levels than marrow recipients. Recipient pretransplantation antibody levels were correlated with the posttransplantation levels, especially in the first 6 months after transplantation when the correlation coefficients typically exceeded 0.6. Donor pretransplantation antibody levels had less of a correlation with posttransplantation levels in the recipient. Patient or donor age, total body irradiation, and graft-versus-host disease or its treatment appeared to have no effect. In conclusion, antibody levels in the first year after transplantation are affected primarily by pretransplantation antibody levels in the recipient and, to a lesser degree, in the donor. These findings suggest that immunization of the recipient and the donor before transplantation may be more effective in improving antibody immunity after transplantation than manipulating graft-versus-host disease, changing conditioning, or increasing the number of lymphocytes in the graft.

Combined cell culture enzyme-linked immunosorbent assay for quantification of poliovirus neutralization- relevant antibodies

A combined cell culture enzyme-linked immunosorbent assay (CCC-ELISA) was developed for measuring the neutralizing antipoliovirus antibodies in human sera. The binding of different concentrations of each of the three poliovirus types to BGM cells in the presence and absence of a constant dilution from each test and reference serum was measured in the CCC-ELISA. The titers of the viruses neutralized by each serum were measured with the titration curves and used for interpretation of neutralizing titers to the three poliovirus types. Analysis of human sera revealed that the sensitivity and specificity of the CCC-ELISA and the microneutralization assay were comparable. The CCC-ELISA is nonsubjective, rapid, and highly reproducible. Furthermore, the CCC-ELISA could potentially be used as a seroepidemiologic tool for assessment of the humoral response to the cell culture infectious viruses.

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.

Induction of Mucosal Immunity by Inactivated Poliovirus Vaccine Is Dependent on Previous Mucosal Contact with Live Virus

The inactivated poliovirus vaccine (IPV) is used for protection against poliomyelitis in The Netherlands. It is not clear, however, whether IPV vaccination can lead to priming of the mucosal immune system and the induction of IgA. It has been demonstrated that IPV vaccination is able to induce strong memory IgA responses in the serum of persons who have been naturally exposed to wild-type poliovirus. This has led to the hypothesis that IPV vaccination is able to induce poliovirus-specific IgA at mucosal sites in persons who have been previously primed with live poliovirus at mucosal sites. To test this hypothesis, the kinetics of the IgA response in serum and saliva after IPV vaccination were examined in persons previously vaccinated with oral poliovirus vaccine (OPV) or IPV. ELISA and enzyme-linked immunospot assays were used for the detection of poliovirus-specific IgA responses. In addition, B cell populations were separated on the basis of the expression of mucosal (α4β7 integrin) and peripheral homing receptors (L-selectin). Parenteral IPV vaccination was able to boost systemic and mucosal IgA responses in previously OPV-vaccinated persons only. None of the previously vaccinated IPV recipients responded with the production of IgA in saliva. In agreement with this finding, a large percentage of the poliovirus-specific IgA-producing lymphocytes detected in previous OPV recipients expressed the α4β7 integrin. It is concluded that IPV vaccination alone is insufficient to induce a mucosal IgA response against poliovirus. In mucosally (OPV-) primed individuals, however, booster vaccination with IPV leads to a strong mucosal IgA response.

Evaluation of an enzyme-linked immunosorbent assay based on binding inhibition for type-specific quantification of poliovirus neutralization-relevant antibodies

To detect neutralization-relevant antibodies against 3 types of poliovirus (PV) without using tissue cultures and live viruses, an enzyme-linked immunosorbent assay (ELISA) based on monoclonal antibody-binding inhibition was evaluated using sera from 80 vaccinated Japanese children and 60 Pakistani poliomyelitis patients. Compared with the neutralization test, the sensitivity of the inhibition ELISA was 100% (111/111) for detection of anti-PV1 antibody, 98.3% (118/120) for anti-PV2, and 96.5% (82/85) for anti-PV3, and the specificity was 93.1% (27/29), 100% (20/20), and 92.7% (51/55), respectively. Thus, the inhibition ELISA showed excellent potential as a seroepidemiologic tool in both vaccinated and naturally-infected populations.