Effect of passively transferred anti-poliovirus antibodies on seroconversion

Neutralizing anti-polio antibody titre in newborn babies in post-polio eradication period in Nigeria

BACKGROUND

According to Polio Eradication and Endgame Strategic Plan 2019-2023 (PEESP), countries that achieved wild polio elimination is expected to replace oral polio vaccine (OPV) which has a risk of vaccine-derived poliovirus, Inactivated Polio Vaccine (IPV). It is important to determine the earliest time in the age of a child at which IPV could be introduced into the country's routine immunization schedule for effectiveness especially as it concerns neutralizing effect of trans-placental transmitted antibodies which usually does not affect OPV. In this study, the level of poliovirus neutralizing antibody titre among neonates at birth was evaluated.

METHODS

A cross-sectional study of mother-baby pair. The serum level of the neutralizing Poliovirus antibody IgG titre was done by the Enzyme Linked Immunosorbent Assay (ELISA) technique.

RESULTS

There was 100% transfer of maternal passive antibodies to their babies. The mean poliovirus antibody titre among neonates was 21.8 IU/L which was above the neutralizing titre level. Most (85.7%) babies antibody level correlate positively with that of their mothers.

CONCLUSION

The transferred maternal antibodies to the babies are still very high at birth, and capable of dampening the immunity of IPV if introduced early. Programme managers should evaluate the impact and benefit of given booster dose of IPV to pregnant mothers to increase the titre level in their babies. This will be very necessary when the OPV is withdrawn from the immunization schedule.

Enhanced humoral response in pregnant mice immunized with liposome encapsulated recombinant neutralizing epitope protein of Hepatitis- E virus

BACKGROUND

Pregnant women from developing countries are at high-risk of hepatitis E-associated high mortality and constitute priority population for vaccination. So far, candidate vaccines have not been evaluated during pregnancy. We evaluated our vaccine candidate, recombinant Neutralizing Epitope protein (rNEp) encapsulated in liposomes, in pregnant mice.

METHODS

A single dose (10 μg) of the formulation was administered intramuscularly on day 7 of pregnancy. Titres of serum IgG antibodies to hepatitis E virus (IgG-anti-HEV), levels of cytokines and biochemical parameters were determined. Spleens were harvested from pregnant and non-pregnant mice for immunophenotyping (flow cytometry), cytokines (cytometric bead array, CBA) and gene expression of immune response genes (Taqman low density array, TLDA). Histopathology studies of spleen, liver, kidneys, brain and muscle was carried out.

RESULTS

The vaccine was well-tolerated during pregnancy as evidenced by histopathology and serum biochemical parameters. Anti-HEV titres were significantly higher in the pregnant balb/c and C57BL/6 mice (3592 ± 802 and 1016 ± 138 respectively, than in non-pregnant groups (634 ± 191 and 320 ± 55 respectively, p < 0.001 for both) suggesting that the higher antibody response in pregnant mice was independent of the genetic makeup of the host but immunogen-driven. Pups receiving vertically transferred antibodies developed lower anti-HEV antibodies (p < 0.05) when immunized with the formulation after seronegativity than in the age-matched mice without such antibodies. In non-pregnant mice, a Th1 response and discordance between splenic and serum cytokines was evident while in pregnancy, a Th2 bias was observed irrespective of immunization. Increased CD19 levels correlated with higher anti-HEV titres in pregnant mice.

CONCLUSION

The single dose of the vaccine was safe and highly immunogenic in pregnant mice. Degree and type of immune response to vaccination during pregnancy is immunogen-driven. In-depth studies are needed to understand the underlying immunologic mechanism(s). These encouraging results for a vaccine intended for use in pregnant women should be confirmed in higher animals.

Preeradication vaccine policy options for poliovirus infection and disease control

With the circulation of wild poliovirus (WPV) types 1 and 3 continuing more than a decade after the original goal of eradicating all three types of WPVs by 2000, policymakers consider many immunization options as they strive to stop transmission in the remaining endemic and outbreak areas and prevent reintroductions of live polioviruses into nonendemic areas. While polio vaccination choices may appear simple, our analysis of current options shows remarkable complexity. We offer important context for current and future polio vaccine decisions and policy analyses by developing decision trees that clearly identify potential options currently used by countries as they evaluate national polio vaccine choices. Based on a comprehensive review of the literature we (1) identify the current vaccination options that national health leaders consider for polio vaccination, (2) characterize current practices and factors that appear to influence national and international choices, and (3) assess the evidence of vaccine effectiveness considering sources of variability between countries and uncertainties associated with limitations of the data. With low numbers of cases occurring globally, the management of polio risks might seem like a relatively low priority, but stopping live poliovirus circulation requires making proactive and intentional choices to manage population immunity in the remaining endemic areas and to prevent reestablishment in nonendemic areas. Our analysis shows remarkable variability in the current national polio vaccine product choices and schedules, with combination vaccine options containing inactivated poliovirus vaccine and different formulations of oral poliovirus vaccine making choices increasingly difficult for national health leaders.