Amount of maternal rotavirus-specific antibodies influence the outcome of rotavirus vaccination of newborn mice with virus-like particles

Polyphosphazene immunoadjuvants: Historical perspective and recent advances

The development of successful vaccines has been increasingly reliant on the use of immunoadjuvants - additives, which can enhance and modulate immune responses to vaccine antigens. Immunoadjuvants of the polyphosphazene family encompass synthetic biodegradable macromolecules, which attain in vivo activity via antigen delivery and immunostimulation mechanisms. Over the last decades, the technology has witnessed evolvement of next generation members, expansion to include various antigens and routes of administration, and progression to clinical phase. This was accompanied by gaining important insights into the mechanism of action and the development of a novel class of virus-mimicking nano-assemblies for antigen delivery. The present review evaluates in vitro and in vivo data generated to date in the context of latest advances in understanding the primary function and biophysical behavior of these macromolecules. It also provides an overview of relevant synthetic and characterization methods, macromolecular biodegradation pathways, and polyphosphazene-based multi-component, nanoparticulate, and microfabricated formulations.

Ginseng Stem-Leaf Saponins in Combination with Selenium Promote the Immune Response in Neonatal Mice with Maternal Antibody

Neonates acquire from their mothers maternal antibody (MatAb) which results in poor immune response to vaccination. We previously demonstrated that ginseng stem-leaf saponins in combination with selenium (GSe) had adjuvant effect on the immune response to an attenuated pseudorabies virus (aPrV) vaccine. The present study was to evaluate GSe for its effect on the immune response to aPrV vaccine in neonatal mice with MatAb. Results showed that GSe had adjuvant effect on the immune response to aPrV vaccine in neonates. When GSe was co-administered with aPrV vaccine (aP-GSe), specific gB antibody, Th1 cytokines (IL-2, IL-12 and IFN-γ) and Th2 cytokines (IL-4, IL-6 and IL-10) responses were significantly increased in association with enhanced protection of vaccinated neonates against the lethal PrV challenge even though MatAb existed when compared to the neonates immunized with aPrV vaccine alone. GSe-enhanced immune response depended on its use in the primary immunization. The mechanisms underlying the adjuvant effect of GSe may be due to more innate immune related pathways activated by GSe. Transcriptome analysis of splenocytes from neonates immunized with aP-GSe, aPrV or saline solution showed that there were 3976 differentially expressed genes (DEGs) in aP-GSe group while 5959 DEGs in aPrV group when compared to the control. Gene ontology (GO) terms and Kyoto encyclopedia of genes and genomes (KEGG) pathways analysis showed that innate immune responses and cytokine productions related terms or pathways were predominantly enriched in aP-GSe group, such as “NOD-like receptor signaling pathway”, “Natural killer cell mediated cytotoxicity”, “NF-κB signaling pathway”, “cytokine-cytokine receptor interaction”, and “Th1 and Th2 cell differentiation”. Considering the potent adjuvant effect of GSe on aPrV vaccine in neonatal mice with MatAb, it deserves further investigation in piglets.

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.

Polyionic vaccine adjuvants: another look at aluminum salts and polyelectrolytes

Adjuvants improve the adaptive immune response to a vaccine antigen by modulating innate immunity or facilitating transport and presentation. The selection of an appropriate adjuvant has become vital as new vaccines trend toward narrower composition, expanded application, and improved safety. Functionally, adjuvants act directly or indirectly on antigen presenting cells (APCs) including dendritic cells (DCs) and are perceived as having molecular patterns associated either with pathogen invasion or endogenous cell damage (known as pathogen associated molecular patterns [PAMPs] and damage associated molecular patterns [DAMPs]), thereby initiating sensing and response pathways. PAMP-type adjuvants are ligands for toll-like receptors (TLRs) and can directly affect DCs to alter the strength, potency, speed, duration, bias, breadth, and scope of adaptive immunity. DAMP-type adjuvants signal via proinflammatory pathways and promote immune cell infiltration, antigen presentation, and effector cell maturation. This class of adjuvants includes mineral salts, oil emulsions, nanoparticles, and polyelectrolytes and comprises colloids and molecular assemblies exhibiting complex, heterogeneous structures. Today innovation in adjuvant technology is driven by rapidly expanding knowledge in immunology, cross-fertilization from other areas including systems biology and materials sciences, and regulatory requirements for quality, safety, efficacy and understanding as part of the vaccine product. Standardizations will aid efforts to better define and compare the structure, function and safety of adjuvants. This article briefly surveys the genesis of adjuvant technology and then re-examines polyionic macromolecules and polyelectrolyte materials, adjuvants currently not known to employ TLR. Specific updates are provided for aluminum-based formulations and polyelectrolytes as examples of improvements to the oldest and emerging classes of vaccine adjuvants in use.

Early exposure of infants to natural rotavirus infection: a review of studies with human rotavirus vaccine RIX4414

BACKGROUND

Rotaviruses are the leading cause of severe acute gastroenteritis in children aged <5 years worldwide. A live attenuated human rotavirus vaccine, RIX4414 has been developed to reduce the global disease burden associated with rotavirus gastroenteritis. Serum anti-rotavirus immunoglobulin A (IgA) antibody measured in unvaccinated infants during clinical trials of RIX4414 reflects natural rotavirus exposure, and may inform the optimal timing for rotavirus vaccination.

METHODS

We reviewed phase II and III randomized, placebo-controlled clinical trials conducted by GlaxoSmithKline Vaccines, Wavre, Belgium between 2000 and 2008 which used the commercial formulation of RIX4414 lyophilized vaccine. We included trials for which demographic data and pre-dose-1 and post-last-dose anti-rotavirus IgA antibody status were available from placebo recipients.

RESULTS

Sixteen clinical trials met the inclusion criteria. The studies were conducted across Africa (N = 3), Asia (N = 4), Latin America (N = 4), Europe (N = 4) and North America (N = 1). Overall, 46,398 infants were enrolled and among these, 20,099 received placebo. The mean age at pre-dose-1 time point ranged from 6.4 - 12.2 weeks while the mean age at post-last-dose time point ranged from 13.5 - 19.6 weeks. The anti-RV IgA seropositivity rates at both time points were higher in less developed countries of Africa, Asia and Latin America (pre-dose-1: 2.1%-26.3%; post-last-dose: 6.3%-34.8%) when compared to more developed countries of Asia, Europe and North America (pre-dose-1: 0%-9.4%; post-last-dose: 0%-21.3%), indicating that rotavirus infections occurred at a younger age in these regions.

CONCLUSION

Exposure to rotavirus infection occurred early in life among infants in most geographical settings, especially in developing countries. These data emphasize the importance of timely rotavirus vaccination within the Expanded Program on Immunization schedule to maximize protection.

Maternal immunization promotes the immune response of neonates towards hepatitis B vaccine

Infants infected with hepatitis B virus (HBV) face the risk of developing severe complications. Unfortunately, in spite of universal vaccination programmes, 5% or more of vaccinated newborns still do not achieve protective levels of anti-hepatitis B virus surface antigen titres (anti-HBs). The aim of this study was to use animal experiments and population-based research to determine whether maternal vaccination against HBV affects the outcome of neonatal vaccination. Six sows and 53 newborn piglets were used for this study and randomly assigned to the vaccination group (three 20 μg doses of recombinant HBV vaccine). All the piglets were followed up to 10 weeks of age, and peripheral blood was withdrawn for measurement of anti-HBs. A cross-sectional study was also conducted on 449 mothers with infants. A structured questionnaire was used to collect demographic, medical and maternal data, and their peripheral blood was collected for measurement of anti-HBs. The results of animal experiments demonstrated that nonvaccinated piglets born to vaccinated sows and nonvaccinated piglets born to nonvaccinated sows were negative for anti-HBs. Repeated measures analysis of variance showed that the titres of anti-HBs in vaccinated piglets born to vaccinated sows were significantly higher than in vaccinated piglets born to nonvaccinated sows (P < 0.05). In a population-based study, a cumulative logistic regression analysis showed that the strongest influences on neonatal anti-HBs titres were delay of the first vaccination dose [OR = 3.02(95% CI: 1.72-5.30)] and maternal anti-HBs titres [OR = 2.48(95% CI: 2.03-3.04)]. In conclusion, high maternal anti-HBs titres can enhance the response to HBV vaccination in infants.

Neutralizing activity and secretory IgA antibodies reactive with rotavirus SA-11 (serotype G3) in colostrum and milk from Brazilian women

BACKGROUND

Rotavirus is an important aetiological agent for severe diarrhoea in infants and young children worldwide. Anti-rotavirus antibodies in human colostrum and milk may interfere with rotavirus vaccination seroconversion.

AIMS

To verify the presence of anti-rotavirus secretory IgA antibodies (SIgA) and the neutralizing capacity of 30 colostrum and 30 milk samples from Brazilian women in two different centres and analyze their persistence throughout lactation.

METHODS

Colostrum and milk samples from healthy nursing mothers were tested for the presence of anti-rotavirus SIgA using conventional ELISA and their capacity to neutralize rotavirus using MA-104 cell cultures. Total IgA concentrations and anti-rotavirus SIgA levels were measured in samples collected from three mothers during 90 or 240 days of the lactation period.

RESULTS

Colostrum samples showed higher levels of anti-rotavirus SIgA and higher neutralizing ability than in milk. However, these antibodies levels were not statistically different. In addition, there was no correlation between antibody levels and the neutralizing activity observed in colostrum and milk samples. Follow-up of three mothers demonstrated the persistence of anti-rotavirus and total IgA levels throughout lactation.

CONCLUSIONS

These results support the encouragement of breastfeeding as a mechanism of protection against rotavirus infection in lactating infants. Components other than SIgA antibodies might play an important role in virus neutralization.

Vaccine-derived NSP2 segment in rotaviruses from vaccinated children with gastroenteritis in Nicaragua

Rotavirus (RV) vaccination programs have been established in several countries using the human-attenuated G1P[8] monovalent vaccine Rotarix (GlaxoSmithKline) and/or the human-bovine reassortant G1, G2, G3, G4, P[8] pentavalent vaccine RotaTeq (Merck). The efficacy of both vaccines is high (∼90%) in developed countries, but can be remarkably lower in developing countries. For example, a vaccine efficacy against severe diarrhea of only 58% was observed in a 2007-2009 Nicaraguan study using RotaTeq. To gain insight into the significant level of vaccine failure in this country, we sequenced the genomes of RVs recovered from vaccinated Nicaraguan children with gastroenteritis. The results revealed that all had genotype specificities typical for human RVs (11 G1P[8], 1 G3P[8]) and that the sequences and antigenic epitopes of the outer capsid proteins (VP4 and VP7) of these viruses were similar to those reported for RVs isolated elsewhere in the world. As expected, nine of the G1P[8] viruses and the single G3P[8] virus had genome constellations typical of human G1P[8] and G3P[8] RVs: G1/3-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1. However, two of the G1P[8] viruses had atypical constellations, G1-P[8]-I1-R1-C1-M1-A1-N2-T1-E1-H1, due to the presence of a genotype-2 NSP2 (N2) gene. The sequence of the N2 NSP2 gene was identical to the bovine N2 NSP2 gene of RotaTeq, indicating that the two atypical viruses originated via reassortment of human G1P[8] RVs with RotaTeq viruses. Together, our data suggest that the high level of vaccine failure in Nicaraguan is probably not due to antigenic drift of commonly circulating virus strains nor the emergence of new antigenetically distinct virus strains. Furthermore, our data suggest that the widespread use of the RotaTeq vaccine has led to the introduction of vaccine genes into circulating human RVs.

Transplacentally acquired maternal antibody against hepatitis B surface antigen in infants and its influence on the response to hepatitis B vaccine

BACKGROUND

Passively acquired maternal antibodies in infants may inhibit active immune responses to vaccines. Whether maternal antibody against hepatitis B surface antigen (anti-HBs) in infants may influence the long-term immunogenicity of hepatitis B vaccine remains unknown.

METHODOLOGY/PRINCIPAL FINDINGS

Totally 338 pairs of mothers and children were enrolled. All infants were routinely vaccinated against hepatitis B based on 0-, 1- and 6-month schedule. We characterized the transplacental transfer of maternal anti-HBs, and compared anti-HBs response in children of mothers with or without anti-HBs. In a prospective observation, all 63 anti-HBs positive mothers transferred anti-HBs to their infants; 84.1% of the infants had higher anti-HBs concentrations than their mothers. One and half years after vaccination with three doses of hepatitis B vaccine, the positive rate and geometric mean concentration (GMC) of anti-HBs in 32 infants with maternal anti-HBs were comparable with those in 32 infants without maternal antibody (90.6% vs 87.5%, P = 0.688, and 74.5 vs 73.5 mIU/ml, P = 0.742, respectively). In a retrospective analysis, five and half years after vaccination with three doses vaccine, the positive rates of anti-HBs in 88 children of mothers with anti-HBs ≥1000 mIU/ml, 94 children of mothers with anti-HBs 10-999 mIU/ml, and 61 children of mothers with anti-HBs <10 mIU/ml were 72.7%, 69.2%, and 63.9% (P = 0.521), respectively; anti-HBs GMC in these three groups were 38.9, 43.9, and 31.7 mIU/ml (P = 0.726), respectively.

CONCLUSIONS/SIGNIFICANCE

The data demonstrate that maternal anti-HBs in infants, even at high concentrations, does not inhibit the long-term immunogenicity of hepatitis B vaccine. Thus, current hepatitis B vaccination schedule for infants will be still effective in the future when most infants are positive for maternal anti-HBs due to the massive vaccination against hepatitis B.

Improved Immunogenicity of Biodegradable Polymer Particles Entrapped Rotavirus Vaccine

Rotavirus (RV) entrapped in polylactide (PLA) and polylactide-coglycolide (PLGA) polymer particles were formulated and evaluated in mice for improved immunogenicity using oral, intranasal (IN), and intramuscular (IM) routes of administration. Microparticles of size ranges between 1 and 8 µm were prepared using double emulsion solvent evaporation technique. Stabilizers like mouse serum albumin, sucrose, and sodium bicarbonate that were used during particle formulation helped in minimizing the denaturation of the entrapped antigen. Immunization with 20 µg of antigen entrapped in polymeric particles through various routes of administration elicited measurable amount of antibody titer in mice. The immunoglobulin A (IgA) and immunoglobulin G (IgG) titer (≥4-fold rise between pre and post immunized sera) was analyzed by the use of enzyme-linked immunosorbent assay. PLGA encapsulated RV microparticles elicited better antibody response through IN route (90%) where as PLA encapsulated RV microparticles showed improved response when administrated through oral route (83.3%). Overall, the performance of IN route based immunization was significantly higher than oral and IM route ( p<0.001) with both the polymers. The results are of indication that, PLGA encapsulated RV microparticles have greater potential for vaccine formulation to combat rotavirus infection.

An oral versus intranasal prime/boost regimen using attenuated human rotavirus or VP2 and VP6 virus-like particles with immunostimulating complexes influences protection and antibody-secreting cell responses to rotavirus in a neonatal gnotobiotic pig model

We determined the impact of mucosal prime/boost regimens and vaccine type (attenuated Wa human rotavirus [AttHRV] or nonreplicating Wa 2/6 rotavirus-like particles [VLP]) on protection and antibody-secreting cell (ASC) responses to HRV in a neonatal gnotobiotic pig disease model. Comparisons of delivery routes for AttHRV and evaluation of nonreplicating VLP vaccines are important as alternative vaccine approaches to overcome risks associated with live oral vaccines. Groups of neonatal gnotobiotic pigs were vaccinated using combinations of oral (PO) and intranasal (IN) inoculation routes as follows: (i) 3 oral doses of AttHRV (AttHRV3xPO); (ii) AttHRV3xIN; (iii) AttHRVPO, then 2/6VLP2xIN; (iv) AttHRVIN, then 2/6VLP2xIN; and (v) mock-inoculated controls. Subsets of pigs from each group were challenged with virulent Wa HRV [P1A(8) G1] (4 weeks post-primary inoculation) to assess protection. The AttHRVPO+2/6VLP2xIN pigs had the highest protection rates against virus shedding and diarrhea (71% each); however, these rates did not differ statistically among the vaccine groups, except for the AttHRVIN+2/6VLPIN group, which had a significantly lower protection rate (17%) against diarrhea. The isotype, magnitude, and tissue distribution of ASCs were analyzed by enzyme-linked immunospot assay. The highest mean numbers of virus-specific IgG and IgA ASCs were observed pre- and postchallenge in both intestinal and systemic lymphoid tissues of the AttHRVPO+2/6VLPIN group. Thus, the AttHRVPO+2/6VLPIN vaccine regimen using immunostimulating complexes (ISCOM) and multiple mucosal inductive sites, followed by AttHRV3xPO or IN regimens, were the most effective vaccine regimens, suggesting that either AttHRVPO+2/6VLPIN or AttHRV3xIN may be an alternative approach to AttHRV3xPO for inducing protective immunity against rotavirus diarrhea.

Comparison of the efficacy of rotavirus VLP vaccines to a live homologous rotavirus vaccine in a pig model of rotavirus disease

Rotavirus-like particles (VLPs) have shown promise as rotavirus vaccine candidates in mice, rabbits and pigs. In pigs, VLP vaccines reduced rotavirus shedding and disease but only when used in conjunction with live attenuated human rotavirus. Using a porcine rotavirus pig model, rotavirus antigen shedding was reduced by up to 40% after vaccination with VLPs including the neutralizing antigens VP7 and VP8* when used in combination with the adjuvant polyphosphazene poly[di(carbozylatophenoxy)phoshazene] (PCPP). In contrast, complete protection from rotavirus antigen shedding and disease was induced by vaccination with the virulent porcine rotavirus PRV 4F. This is the first study to demonstrate some post-challenge reductions in rotavirus antigen shedding in a pig model of rotavirus disease after vaccination with VLPs without combining with infectious rotavirus.

Influence of maternal antibody against hepatitis B surface antigen on active immune response to hepatitis B vaccine in infants

Transplacentally acquired maternal antibodies in infants may inhibit active immune responses to vaccines. In this study, we compared the immunogenicity of the recombinant hepatitis B vaccine, which was intramuscularly injected at 0, 1, and 6 months of age, in 71 infants born to mothers with positive or negative antibody against hepatitis B surface antigen (anti-HBs). Forty-one infants born to anti-HBs positive mothers were all positive at birth. At 2 months after the second injection, anti-HBs in 30 infants with negative maternal antibody was significantly higher than that in 41 infants with positive maternal anti-HBs (191.1mIU/ml vs. 96.2mIU/ml, P=0.018). At one month after the full immunization, the anti-HBs levels had no statistical difference between maternal anti-HBs negative and positive groups, but the antibody response in infants with high maternal anti-HBs (>1000mIU/ml) was significantly inhibited. Nevertheless, all infants had anti-HBs higher than the protective level. In conclusion, passively acquired maternal anti-HBs in infants may to some extent impair the antibody response to hepatitis B vaccine. The long-term efficacy of hepatitis B vaccine in infants with high titers of maternal anti-HBs remains to be further evaluated.