Effect Of Maternal Antibodies Research Articles

Effects of maternal antibodies in infants on the immunogenicity and safety of inactivated polio vaccine in infants

ABSTRACT The presence of maternal poliovirus antibodies may interfere with the immune response to inactivated polio vaccine (IPV), and its influence on the safety of vaccination is not yet understood. A total of 1146 eligible infants were randomly assigned (1:1) to the IPV and Sabin IPV (SIPV) groups to compare and analyze the efficacy of the two vaccines in preventing poliovirus infection. We pooled the SIPV and IPV groups and reclassified them into the maternal poliovirus antibody-positive group (MAPG; ≥1: 8) and the maternal poliovirus antibody-negative group (MANG; <1: 8). We evaluated the impact of maternal poliovirus antibodies by comparing the geometric mean titer (GMT), seroconversion rate, and geometric mean increase (GMI) of types I–III poliovirus neutralizing antibodies post-vaccination, and incidence rates of adverse reactions following vaccination between the MAPG and MANG. Respective seroconversion rates in the MAPG and MANG were 94% and 100%, 79.27% and 100%, and 93.26% and 100% (all serotypes, P < .01) for types I—III poliovirus, respectively. The GMT of all types of poliovirus antibodies in the MAPG (1319.13, 219.91, 764.11, respectively) were significantly lower than those in the MANG (1584.92, 286.73, 899.59, respectively) (P < .05). The GMI in the MAPG was significantly lower than that in the MANG (P < .05). No statistically significant difference in the incidence of local and systemic adverse reactions was observed between the MAPG and MANG. Thus, the presence of maternal poliovirus antibodies does not affect the safety of IPV but can negatively impact the immune responses in infants after IPV vaccination.

Genetic variation in the immune system and malaria susceptibility in infants: a nested case\u2013control study in Nanoro, Burkina Faso

BackgroundGenetic polymorphisms in the human immune system modulate susceptibility to malaria. However, there is a paucity of data on the contribution of immunogenetic variants to malaria susceptibility in infants, who present differential biological features related to the immaturity of their adaptive immune system, the protective effect of maternal antibodies and fetal haemoglobin. This study investigated the association between genetic variation in innate immune response genes and malaria susceptibility during the first year of life in 656 infants from a birth cohort survey performed in Nanoro, Burkina Faso.MethodsSeventeen single nucleotide polymorphisms (SNPs) in 11 genes of the immune system previously associated with different malaria phenotypes were genotyped using TaqMan allelic hybridization assays in a Fluidigm platform. Plasmodium falciparum infection and clinical disease were documented by active and passive case detection. Case–control association analyses for both alleles and genotypes were carried out using univariate and multivariate logistic regression. For cytokines showing significant SNP associations in multivariate analyses, cord blood supernatant concentrations were measured by quantitative suspension array technology (Luminex).ResultsGenetic variants in IL-1β (rs1143634) and FcγRIIA/CD32 (rs1801274)—both in allelic, dominant and co-dominant models—were significantly associated with protection from both P. falciparum infection and clinical malaria. Furthermore, heterozygote individuals with rs1801274 SNP in FcγRIIA/CD32 showed higher IL-1RA levels compared to wild-type homozygotes (P = 0.024), a cytokine whose production is promoted by the binding of IgG immune complexes to Fcγ receptors on effector immune cells.ConclusionsThese findings indicate that genetic polymorphisms in genes driving innate immune responses are associated to malaria susceptibility during the first year of life, possibly by modulating production of inflammatory mediators.

The Effect of Maternal Antibodies on Clinical Response to Infection with Epizootic Hemorrhagic Disease Virus in White-Tailed Deer (Odocoileus virginianus) Fawns.

We investigated whether naturally acquired maternal antibodies to epizootic hemorrhagic disease virus serotype 2 (EHDV-2) would protect white-tailed deer (Odocoileus virginianus) fawns against infection and clinical disease following an EHDV-2 challenge. We compared viremia and clinical response in 27-47-d-old, experimentally infected fawns with and without maternally derived antibodies to EHDV-2. Mild to moderate clinical signs were observed in four seronegative (maternal antibody-negative) fawns, which were viremic from 3 to 14 d postinoculation. Individual peak blood virus titers for seronegative fawns ranged from 104.3 to 106.3 median tissue culture infective doses (TCID50)/mL. In contrast, clinical signs were not observed in seropositive (maternal antibody-positive) fawns and a transient low-level viremia (≤102.4 TCID50/mL) occurred in two of six fawns. Our results indicated that the presence of maternally derived EHDV-2 antibodies in fawns prevents or greatly reduces clinical disease and the level and duration of EHDV-2 viremia.

Effect of maternal antibodies on the immune response to different canine parvovirus vaccines and antibody response to selected vaccines

Canine parvovirus (CPV) is the main cause of gastroenteritis and mortalities in young dogs worldwide. Despite vaccination, the outbreaks of canine parvovirus infection occur in many countries including Sri Lanka. Interference caused by maternally derived antibodies (MDA) is a main reason for vaccination failure. Present study assessed the level of CPV specific MDA in puppies prior to vaccination, the effect of MDA on the efficacy of different preparations of CPV vaccines and, evaluated the immunogenicity of selected CPV vaccines available commercially. Analysis of MDA in puppies born to vaccinated or unvaccinated mothers using commercially available point of care ELISA based test revealed the presence of protective levels of MDA titres at 8 weeks of age which can affect the immunogenicity of the vaccines containing inactivated virus or low viral titre (1000 HAU). The vaccines containing CCID 50 of ≥103-5 were able to induce antibody titres higher than protective level. Analysis of CPV-2 specific antibody titres, two weeks after completing the primary CPV vaccination (16-18 weeks of age) revealed that the dogs who received the vaccines containing CPV-2 or CPV-2b strain with >105 CCID 50 induced significantly high levels of mean antibody titre (vaccine “B”- p value = 0.004; vaccine “D” - p value = 0.022; vaccine “F”- p value = 0.032) when compared to the vaccine containing 1000 HAU. In conclusion, it was evident that the interference of MDA on CPV vaccines could be circumvented by using a live attenuated CPV vaccine having a high viral dose of CPV. Low viral dose vaccines and inactivated vaccines are not suitable for primary vaccination as those could be interfered by maternal immunity.

Clinical evaluation, serological response and lesions generated by the A/Mexico/La Gloria-3/2009/H1N1 and A/swine/New Jersey/11/1976/H1N1 influenza viruses in colostrated and non-colostrated pigs.

Influenza A viruses cause respiratory disease in piglets, and maternal immunity plays an important role in protecting against Influenza virus infection. Nevertheless, in the presence of high levels of maternal antibodies against influenza, an adequate immune response is not developed. In this study, the effect of maternal antibodies against the swine influenza A/swine/New Jersey/11/1976/H1N1 virus (swH1N1) on clinical presentation, serological response, and lesions produced in colostrated and non-colostrated pigs was evaluated in pigs infected with the human influenza A/Mexico/La Gloria-3/2009/ H1N1 (pH1N1) and swH1N1 viruses. Our results indicated that between 2 and 4days post-challenge, sneezing and mild nasal discharge were observed in all pigs. Body temperature in pigs from all treatment groups ranged between 39.2 and 39.3°C. Pigs inoculated with the pH1N1 virus (421g) exhibited a significantly lower daily weight gain than those inoculated with the swH1N1 virus (524g). HI antibody titers against the pH1N1 virus were significantly different between colostrated (1.62) and non-colostrated (0.43) pigs. Significant differences in antibody titers were detected between pigs inoculated with the pH1N1 (1.28) or the swH1N1 virus (0.77) (P < 0.05). The highest percentage of pulmonary lesions was observed in non-colostrated/pH1N1 pigs (11.88%) at 6days post-challenge. Cross reactivity was observed between the pH1N1 and swH1N1 viruses, as the maternal antibodies against the swH1N1 virus successfully neutralized the pH1N1 virus infection.

Effect of maternal antibody on the infant immune response to inactivated poliovirus vaccines made from Sabin strains

ABSTRACTThis study aimed to evaluate the effect of maternally derived antibody on the immunogenicity of Sabin IPV. A total of 600 infants were randomized to receive one of the five different vaccines: the high- (group A), medium- (group B) or low-dose (group C) of investigational Sabin IPV, the control Salk IPV (group D) or the control Sabin IPV (group E), at 2, 3 and 4 months of age. The post-vaccination GMTs, GMIs and seroconversion rates of poliovirus type–specific neutralizing antibody were analyzed for different maternal antibody levels. The correlations between maternal antibody levels and post-vaccination antibody responses were also modeled by linear regressions. The post-vaccination GMTs were significantly lower among infants with high maternal antibody titers for poliovirus type 1 or 2 mainly in the groups B, C, D and E. The GMIs and seroconversion rates decreased significantly with the increase of maternal antibody levels in all the five groups. In the groups A, B and C, maternal antibody levels were negatively associated with the post-vaccination antibody titers (for poliovirus type 1 and 2) and the fold increases of post-vaccination antibody (for all the 3 poliovirus types). With the reduce of potency of the investigational Sabin IPVs, the linear regression coefficients increased accordingly in the groups A, B and C. In conclusion, high levels of maternal poliovirus antibody could attenuate the immune responses to the Sabin IPVs. Altering the potency of the investigational Sabin IPVs could alter the associations between maternal antibody levels and the serologic responses of infants.

The effect of pre-laying maternal immunization on offspring growth and immunity differs across experimentally altered postnatal rearing conditions in a wild songbird

BackgroundPrenatal antibody transfer is an immune-mediated maternal effect by which females can shape postnatal offspring resistance to pathogens and parasites. Maternal antibodies passed on to offspring provide primary protection to neonates against diverse pathogenic antigens, but they may also affect offspring growth and influence the development of an offspring’s own immune response. The effects of maternal antibodies on offspring performance commonly require that the disease environment experienced by a mother prior to breeding matches the environment encountered by her offspring after hatching/birth. However, other circumstances, like postnatal rearing conditions that affect offspring food availability, may also determine the effects of maternal antibodies on offspring growth and immunity. To date, knowledge about how prenatal immune-mediated maternal effects interact with various postnatal rearing conditions to affect offspring development and phenotype in wild bird population remains elusive. Here we experimentally studied the interactive effects of pre-laying maternal immunization with a bacterial antigen (lipopolysaccharide) and post-hatching rearing conditions, altered by brood size manipulation, on offspring growth and humoral immunity of wild great tits (Parus major).ResultsWe found that maternal immunization and brood size manipulation interactively affected the growth and specific humoral immune response of avian offspring. Among nestlings reared in enlarged broods, only those that originated from immunized mothers grew better and were heavier at fledging stage compared to those that originated from non-immunized mothers. In contrast, no such effects were observed among nestlings reared in non-manipulated (control) broods. Moreover, offspring of immunized females had a stronger humoral immune response to lipopolysaccharide during postnatal development than offspring of non-immunized females, but only when the nestling was reared in control broods.ConclusionsThis study demonstrates that offspring development and their ability to cope with pathogens after hatching are driven by mutual influences of pathogen-induced prenatal maternal effects and post-hatching rearing conditions. Our findings suggest that immune-mediated maternal effects may have context-dependent influences on offspring growth and immune function, related to the postnatal environmental conditions experienced by the progeny.

Effect of maternal antibodies and pig age on the antibody response after vaccination against Glässers disease

The influence of age and maternal antibodies on the development and duration of postvaccinal antibody response against Glässer's disease were investigated. Pigs born to immune (MDA-positive) and non-immune (MDA-negative) sows were vaccinated with inactivated vaccine. Vaccination was done according to three different protocols: at 1 and 4, at 2 and 5 or at 4 and 7 weeks of age. There were also two control groups for MDA-negative and MDA-positive pigs. The level of Haemophilus parasuis (Hps) specific antibodies were determined using commercial ELISA test. No serological responses were seen in any of the groups after the first vaccination. Maternally derived antibodies (MDA) against Hps were above the positive level until approximately 3 weeks of life in MDA-positive pigs. In those pigs the strongest postvaccinal humoral response was observed in piglets vaccinated at 4 and 7 weeks of age. In the remaining MDA-positive piglets only slight seroconversion was noted but levels of antibodies never exceeded values considered as positive. All MDA-negative pigs produced Hps-specific antibodies after the second vaccination. The results of the present study indicated that MDA may alter the development and duration of active postvaccinal antibody response. Age of pigs at the moment of vaccination was not associated with the significant differences in the magnitude of antibody response, however influenced the kinetics of decline of Hps-specific antibodies.

Prolongation of the Atrioventricular Conduction in Fetuses Exposed to Maternal Anti-Ro/SSA and Anti-La/SSB Antibodies Did Not Predict Progressive Heart Block: A Prospective Observational Study on the Effects of Maternal Antibodies on 165 Fetuses

We prospectively examined the prevalence and outcome of untreated fetal atrioventricular (AV) prolongation in the presence of maternal anti-Ro antibodies. It has been suggested that antibody-mediated congenital complete atrioventricular block (CAVB) may be preventable if detected and treated early when low-grade block is present. With this rationale in mind, dexamethasone has been advocated by others to treat prolonged fetal AV conduction >2 z-scores, consistent with first-degree heart block. Between July 2003 and June 2009, 165 fetuses of 142 anti-Ro/La antibody-positive women were referred to our center for serial echocardiography. Our protocol included weekly evaluation of the fetal AV conduction between 19 (range 17 to 23) and 24 (range 23 to 35) gestational weeks. AV times were compared with institutional reference data and with post-natal electrocardiograms. Of 150 fetuses with persistently normal AV conduction throughout the observation period, a diagnosis of CAVB was subsequently made in 1 at 28 weeks, after the serial evaluation had ended. Of 15 untreated fetuses either with AV prolongation between 2 and 6 z-scores or with type 1 second-degree block, progressive heart block developed in none of them. Three of these 15 fetuses (20%) had a neonatal diagnosis of first-degree block that spontaneously resolved (n = 2) or has not progressed (n = 1) on follow-up examinations. No other cardiac complications were detected. Fetal AV prolongation did not predict progressive heart block to birth. Our findings question the rationale of a management strategy that relies on the early identification and treatment of fetal AV prolongation to prevent CAVB.

Investigation of the Presence and Protective Effects of Maternal Antibodies Against Campylobacter jejuni in Chickens

Investigation of the Presence and Protective Effects of Maternal Antibodies Against Campylobacter jejuni in Chickens

Maternal antibodies postpone hantavirus infection and enhance individual breeding success

The transfer of maternal antibodies from mother to progeny is a well-known phenomenon in avian and mammalian species. Optimally, they protect the newborn against the pathogens in the environment. The effect of maternal antibodies on microparasite transmission dynamics may have important consequences for both the fitness of the host and the epizootic processes of the pathogens. However, there is a scarcity of studies examining these effects in free-living wild species. We studied the influence of maternal antibodies against the zoonotic Puumala hantavirus (PUUV) on the fitness of bank voles (Clethrionomys glareolus) and on PUUV transmission by exposing young maternal antibody-positive (MatAb+) and negative (MatAb-) bank voles (n=160) to PUUV in experimental populations. PUUV-specific maternal antibodies delayed the timing of infection. Females were more susceptible to PUUV infection than males. Interestingly, both the females and the males with maternal antibodies matured earlier than the other individuals in the population. Our results highlight the significance of maternal antibodies in the transmission of a pathogen and in the breeding success of the carriers.

The effect of maternal antibodies on the detection of bovine virus diarrhoea virus in peripheral blood samples

Persistently infected animals (PI animals), that is those animals born after an intrauterine infection of the dam during the first 120 days of gestation, are the main source of bovine virus diarrhoea virus (BVD virus) in a cattle population. The success of any BVD virus eradication programme depends on the ability to detect all PI animals at a young age. The purpose of this study was to evaluate the use of the antigen ELISA test and the reverse transcriptase-polymerase chain reaction (RT-PCR) test for the diagnosis of PI animals in the presence of maternal antibodies, and to compare them with the classical virus isolation test. In this experiment, 25 calves born after an experimental infection with a mixture of BVD virus field strains were used. All calves were found to be positive for BVD virus using the virus isolation test, both before the ingestion of colostrum and again at 10 weeks of age. Both the virus isolation test and the antigen ELISA test were shown to be unreliable indicators for the diagnosis of persistent infections with BVD virus, when used in the presence of high levels of maternal antibodies. However, the RT-PCR test gave positive results even in the presence of high maternal antibody titres, indicating the suitability of the RT-PCR test for use in eradication programmes.

Understanding Risk Factors for Neonatal Herpes Can Help Prevent It

The risk for transmitting herpes simplex virus (HSV) from mother to infant is poorly quantified, as is the effect of maternal antibodies to HSV type 1

Immunisation against Theileria parva in eastern Zambia: influence of maternal antibodies and demonstration of the carrier status.

Immunisation of calves by the infection and treatment method (I & T) has been extensively used in the eastern province of Zambia to control East Coast fever (ECF), a protozoan tick-borne disease. This paper presents the results of a field longitudinal study, which included a total of 148 Angoni calves. After immunisation against ECF, they were monitored for a full rainy season, coinciding with the main peak of activity of the vector of Theileria parva, the tick Rhipicephalus appendiculatus. Dysimmunisation (acute reaction generated by I & T immunisation), seroconversion and mortality are among the parameters recorded. The effect of maternal antibodies on these parameters was analysed and also studied in experimental conditions on two calves. Before immunisation, young calves had a higher seroprevalence than older animals (maternal antibodies) but their post-immunisation seroprevalence was lower. There was no evidence that their immunoprotection was weaker but this indicates that the post-immunisation seroconversion is probably not a reliable tool to monitor the efficacy of calf immunisation. The carrier state of cattle after immunisation was investigated in experimental conditions on three bovines whereas in the field, the infection prevalence in the ticks was estimated using the relation between the tick burden and the T. parva contacts with the calves. The ability of larval and nymphal R. appendiculatus ticks to pick-up T. parva from carriers and to transmit it to naïve animals after moulting was assessed. It was found that both instars are able to transmit clinical and lethal ECF but that the prevalence of T. parva infection in nymphs is much lower than in adults, confirming the primary role of adults in the transmission of ECF in endemic conditions. Similar results were obtained from the field whereby the ECF peak corresponds with the peak of adult R. appendiculatus activity. The infection prevalence in the ticks was however much lower in the field than in experimental conditions indicating that an important proportion of them feed on alternative hosts. Old ticks seemed to have lost part of their infectivity.

Evaluation of the immune response and detection of infectious bursal disease viruses by reverse transcriptase-polymerase chain reaction and enzyme-linked immunosorbent assay after in ovo vaccination of commercial broilers.

Maternal immunity can interfere with infectious bursal disease virus (IBDV) vaccine efficacy. The effect of maternal antibody (MacAb) on the immune response and detection of two vaccine viruses, an IBDV immune complex (cx) and IBDV-2512, was investigated. Vaccines were administered in ovo at 100 mean embryo infectious dose to commerical broiler embryos derived from young (29 wk) or old (63 wk) flocks. Chickens with low MatAb were challenged with an antigenic standard IBDV strain at 21 and 35 days post in ovo vaccination (PIOV). At 28 and 42 days PIOV, birds were euthanatized and bursa weight: body weight ratios were determined. MatAb of progeny from the 29-wk-old flock was higher (P < 0.05) than that from progeny of the 63-wk-old flock. Progeny titers declined by day 21 PIOV. Birds with MatAb vaccinated with either the IBDV-2512 or IBDV-Icx vaccine did not mount an antibody response by 21 days PIOV. The IBDV-Icx vaccination protected chickens against bursal atrophy when they were challenged at 21 and 35 days PIOV (83% and 77%, respectively). Resistance to challenge in the absence of antibody implies that cellular immunity plays a role in IBDV protection. The IBDV-2512 vaccine caused atrophy of the bursae, and, therefore, we could not examine its protection by these criteria. Neither vaccine could be detected by antigen-capture chemiluminescent enzyme-linked immunosorbent assay. Therefore, total RNA was extracted and reverse transcription (RT)-polymerase chain reaction (PCR) and nested PCR were conducted to amplify the VP2 (hypervariable) region on viral RNA collected at 3, 6, 9, 15, and 21 days PIOV. Nested PCR detected the VP2 region of both IBDV vaccine viruses at day 3 PIOV. Only IBDV-2512 RNA was detected on day 6 PIOV. However, the IBDV-Icx RNA was detected on days 9 and 15 PIOV but not on day 21 PIOV. The IBDV-Icx RNA was evident in tissues and could induce protection against challenge. This work gives further insight into the mechanism of the IBDV-Icx vaccine.

Effect of maternal antibodies on induction and persistence of vaccine-induced immune responses against bovine viral diarrhea virus type II in young calves.

To determine the effect of maternally derived antibodies on induction of protective immune responses against bovine viral diarrhea virus (BVDV) type II in young calves vaccinated with a modified-live bovine viral diarrhea virus (BVDV) type I vaccine. Blinded controlled challenge study. 24 neonatal Holstein and Holstein-cross calves that were deprived of maternal colostrum and fed pooled colostrum that contained a high concentration of (n = 6) or no (18) antibodies to BVDV. At 10 to 14 days of age, 6 seropositive and 6 seronegative calves were given a combination vaccine containing modified-live BVDV type I. All calves were kept in isolation for 4.5 months. Six calves of the remaining 12 untreated calves were vaccinated with the same combination vaccine at approximately 4 months of age. Three weeks later, all calves were challenged intranasally with a virulent BVDV type II. Seronegative unvaccinated calves and seropositive calves that were vaccinated at 2 weeks of age developed severe disease, and 4 calves in each of these groups required euthanasia. Seronegative calves that were vaccinated at 2 weeks or 4 months of age developed only mild or no clinical signs of disease. Results indicate that a single dose of a modified-live BVDV type-I vaccine given at 10 to 14 days of age can protect susceptible young calves from virulent BVDV type II infection for at least 4 months, but high concentrations of BVDV-specific maternally derived antibodies can block the induction of the response.

Effect of maternal antibodies on influenza virus-specific immune response elicited by inactivated virus and naked DNA.

While vaccines are effective in adults, they are less successful in newborns and infants. Neonatal unresponsiveness to vaccines could be owing to immaturity of lymphocytes and/or to inhibition by maternal antibodies. Unresponsiveness of newborn to vaccines can be overcame by genetic immunization. In the present study we investigated the effect of maternal antibodies on the anti-influenza virus protective response in progeny born to dams immunized with plasmid containing the hemagglutinin gene or UV-inactivated virus. The effect of maternal antibodies was studied in plasmid immunized F1 mice born to BALB/c dams, previously immunized with virus or plasmid and crossed with C57BL/6 males, as well as in offspring born to BALB/c dams immunized with plasmid and then immunized with UV-inactivated WSN virus. We have found that the inhibition period of the anti-HA antibody response in offspring born to dams immunized with DNA is shorter than that of offspring born to dams immunized with virus. Furthermore, there is a persistent inhibitory effect on B cells from offspring born to dams immunized with virus or injected with antiviral monoclonal antibodies (MoAb), after the decline of maternal antibody titers. The analysis of the haemagglutinin-specific clonotype reactivity pattern of offspring born to dams immunized with inactivated influenza virus or with a plasmid showed that clonotypes producing antibodies specific for the immunizing virus strain were predominant in offspring born to dams immunized with DNA compared to those born to dams immunized with virus. Maternal antibodies do not affect cell-mediated immunity. These findings might be used to design efficient vaccination schedules for newborns and infants.

Effects of maternal antibodies on protection and development of antibody responses to human rotavirus in gnotobiotic pigs.

Although maternal antibodies can protect against infectious disease in infancy, they can also suppress active immune responses. The effects of circulating maternal antibodies, with and without colostrum and milk antibodies, on passive protection and active immunity to human rotavirus (HRV) were examined in gnotobiotic pigs. Pigs received intraperitoneal injections of high-titer serum (immune pigs [groups 1 and 2]) from immunized sows, low-titer serum from naturally infected sows (control pigs [groups 3 and 4]), or no serum (group 5). Immune or control colostrum and milk were added to the diet of groups 2 and 4, respectively. After inoculation (3 to 5 days of age) and challenge (postinoculation day [PID] 21) with virulent HRV, the effects of maternal antibodies on protection (from diarrhea and virus shedding), and on active antibody responses (measured by quantitation of antibody-secreting cells [ASC] in intestinal and systemic lymphoid tissues by ELISPOT) were evaluated. Groups 1 and 2 had significantly less diarrhea and virus shedding after inoculation but higher rates of diarrhea and virus shedding after challenge than did groups 3 and 5. Group 1 and 2 pigs had significantly fewer immunoglobulin A (IgA) ASC in intestinal tissues at PID 21 and at postchallenge day (PCD) 7 compared to group 5. Significantly fewer IgG ASC were present in the intestines of group 2 pigs at PID 21 and PCD 7 compared to group 5. There was a trend towards fewer ASC in intestinal tissues of group 2 than group 1, from PID 21 on, with significantly fewer IgA ASC at PCD 7. IgG ASC in the duodenum and mesenteric lymph nodes of group 3 and 4 pigs were significantly fewer than in group 5 at PCD 7. These decreases in ASC emphasize the role of passive antibodies in impairing induction of ASC rather than in merely suppressing the function of differentiated B cells. To be successful, vaccines intended for populations with high titers of maternal antibodies (infants in developing countries) may require higher titers of virus, multiple doses, or improved delivery systems, such as the use of microencapsulation or immune stimulating complexes, to overcome the suppressive effects of maternal antibodies.

Effect of passively transferred anti-poliovirus antibodies on seroconversion.

A prospective study enrolling 50 mother-infant pairs was undertaken to determine the effect of maternal antibodies on poliovirus antibody titres and seroconversion rates in infants and to determine the difference in titres and seroconversion rates following three and five doses of oral poliovaccine (OPV). Cord blood samples and samples collected 4 weeks after 3rd and 5th doses of trivalent oral poliovaccine were processed for estimation of anti-poliovirus antibody titres. These were expressed as geometric mean titres (GMT). Significance was analyzed using unpaired 't' test. The relationship between maternal antibody titres and seroconversion was determined by correlation coefficient test. Post OPV5 titres were significantly higher than post OPV3 titres for type 1 and type 2 polioviruses. Seroconversion rates against type 1, 2 and 3 polioviruses were 92.9%, 100.0% and 92.9% following OPV3 and 100.0%, 100.0% and 93.2% following OPV5. The cord blood titres did not have any relation to post-OPV3 or post-OPV5 titres. Although there is significant passive transfer of poliovirus antibodies across the placenta, this does not affect titres achieved after immunization. Post-OPV5 titres against type 1 and type 2 viruses are significantly higher than post-OPV3 titres. The seroconversion rates following OPV5 are higher than those obtained post-OPV3 but this difference is not statistically significant.

Prospects for the Development of New Vaccine Adjuvants

This review focuses on the impact of various new adjuvant formulations on the efficacy of existing and new human vaccines. Despite major advances in our understanding of immunology and vaccine adjuvants, existing and even new prophylactic vaccines seem likely to maintain their dependence upon aluminium salts for the foreseeable future. Additional immunomodulators may be included in these formulations to improve efficacy. A number of immunotherapeutic cancer vaccines appear likely to be registered soon and these will be dependent for efficacy upon new adjuvant formulations. The most useful to date have been the saponins e.g. QS-21, detox-B and Mycobacterial cells (either live as BCG, or killed). Vaccines to treat chronic infections will doubtless benefit from these developments. Adjuvant formulations and technologies exist to permit development of mucosal delivery, needle-free parenteral delivery and single dose vaccines. However, each of these will require intensive development, which will doubtless arrive when demanded by a specific application. Possibilities exist to improve responses in the elderly and to overcome the inhibitory effects of maternal antibodies in neonates. However, considerable work is required to establish the practicality and general utility of new approaches.