Priming of immune responses to hepatitis B surface antigen in young mice immunized in the presence of maternally derived antibodies

Haemagglutinin antigen selectively targeted to chicken CD83 overcomes interference from maternally derived antibodies in chickens

Maternally derived antibodies (MDAs) are important for protecting chickens against pathogens in the neonatal stage however, they often interfere with vaccine performance. Here, we investigated the effects of MDAs on a targeted antigen delivery vaccine (TADV), which is developed by conjugating H9 subtype avian influenza virus haemagglutinin (HA) antigen to single chain fragment variable (scFv) antibodies specific for the chicken antigen presenting cell receptor CD83. Groups of 1-day-old chickens carrying high levels of MDAs (MDA++) and 14-day old chickens carrying medium levels of MDAs (MDA+) were immunised with TADV (rH9HA-CD83 scFv), untargeted rH9HA or inactivated H9N2 vaccines. Immunogenicity in these vaccinated chickens was compared using haemagglutination inhibition (HI) and enzyme-linked immunosorbent assays (ELISA). The results showed that the TADV (rH9HA-CD83 scFv) induced significantly higher levels of H9HA-specific antibody titres compared to the untargeted rH9HA and inactivated H9N2 vaccines in MDA++ and MDA+ chickens. Overall, the data demonstrates immune responses induced by TADV are not affected by the MDA in chickens.

The effect of maternal antibodies on the cellular immune response after infant vaccination: A review

During the last few decades, maternal immunization as a strategy to protect young infants from infectious diseases has been increasingly recommended, yet some issues have emerged. Studies have shown that for several vaccines, such as live attenuated, toxoid and conjugated vaccines, high maternal antibody titers inhibit the infant's humoral immune response after infant vaccination. However, it is not clear whether this decreased antibody titer has any clinical impact on the infant's protection, as the cellular immune responses are often equally important in providing disease protection and may therefore compensate for diminished antibody levels. Reports describing the effect of maternal antibodies on the cellular immune response after infant vaccination are scarce, probably because such studies are expensive, labor intensive and utilize poorly standardized laboratory techniques. Therefore, this review aims to shed light on what is currently known about the cellular immune responses after infant vaccination in the presence of high (maternal) antibody titers both in animal and human studies. Overall, the findings suggest that maternally derived antibodies do not interfere with the cellular immune responses after infant vaccination. However, more research in humans is clearly needed, as most data originate from animal studies.

Adjuvant Effect of Bacille Calmette-Guérin on Hepatitis B Vaccine Immunogenicity in the Preterm and Term Newborn

Immunization is key to protecting term and preterm infants from a heightened risk of infection. However, preterm immunity is distinct from that of the term, limiting its ability to effectively respond to vaccines routinely given at birth, such as hepatitis B vaccine (HBV). As part of the Expanded Program on Immunization, HBV is often given together with the live-attenuated vaccine Bacille Calmette-Guérin (BCG), known to activate multiple pattern-recognition receptors. Of note, some clinical studies suggest BCG can enhance efficacy of other vaccines in term newborns. However, little is known about whether BCG can shape Th-polarizing cytokine responses to HBV nor the age-dependency of such effects, including whether they may extend to the preterm. To characterize the effects of BCG on HBV immunogenicity, we studied individual and combined administration of these vaccines to cord newborn and adult human whole blood and mononuclear cells in vitro and to neonatal and adult mice in vivo. Compared to either BCG or HBV alone, (BCG + HBV) synergistically enhanced in vitro whole blood production of IL-1β, while (BCG + HBV) also promoted production of several cytokines/chemokines in all age groups, age-specific enhancement included IL-12p70 in the preterm and GM-CSF in the preterm and term. In human mononuclear cells, (BCG + HBV) enhanced mRNA expression of several genes including CSF2, which contributed to clustering of genes by vaccine treatment via principle component analysis. To assess the impact of BCG on HBV immunization, mice of three different age groups were immunized subcutaneously with, BCG, HBV, (BCG + HBV) into the same site; or BCG and HBV injected into separate sites. Whether injected into a separate site or at the same site, co-administration of BCG with HBV significantly enhanced anti-HBV IgG titers in mice immunized on day of life-0 or -7, respectively, but not in adult mice. In summary, our data demonstrate that innate and adaptive vaccine responses of preterm and term newborns are immunologically distinct. Furthermore, BCG or "BCG-like" adjuvants should be further studied as a promising adjuvantation approach to enhance immunogenicity of vaccines to protect these vulnerable populations.

Immunogenicity of porcine circovirus type 2 nucleic acid vaccine containing CpG motif for mice

BACKGROUND

This study aimed at reseaching the immune effect of porcine circovirus type 2 (PCV2) DNA vaccine containing CpG motif on mice.

METHODS

A total of 40 6-week-old female BALB/c mice were randomly divided into four groups which were immunized by 18CpG-pVAX1-ORF2, pVAX1-ORF2, pVAX1 and PBS, respectively, and immunized again 2 weeks later. All mice were challenged with 0.2 mL PCV2 cells virulent strain SD (106.0 TCID50/mL) after 4 weeks. Average daily gain, blood antibody levels, microscopic changes and viremia were detected to estimate the effect of DNA vaccine.

RESULTS AND DISCUSSION

The results showed that compared to those of the control mice, groups immunized with pVAX1-ORF2 and 18CpG-pVAX1-ORF2 could induce PCV2-specific antibodies. The PCV2-specific antibodies level of 18 CpG-pVAX1-ORF2 groups was higher significantly than other groups and decreased slowly along with time. There was no distinct pathological damage and viremia occurring in mice that inoculated with CpG motif DNA vaccines. The results demonstrated that the DNA vaccine containing 18 CpG could build up resistibility immunity and reduce immune organ damage on mice.

Distinct TLR-mediated cytokine production and immunoglobulin secretion in human newborn naïve B cells

Neonatal innate immunity is distinct from that of adults, which may contribute to increased susceptibility to infection and limit vaccine responses. B cells play critical roles in protection from infection and detect PAMPs via TLRs, that, when co-activated with CD40, can drive B-cell proliferation and Ab production. We characterized the expression of TLRs in circulating B cells from newborns and adults, and evaluated TLR- and CD40-mediated naïve B-cell class-switch recombination (CSR) and cytokine production. Gene expression levels of most TLRs was similar between newborn and adult B cells, except that newborn naïve B cells expressed more TLR9 than adult naïve B cells. Neonatal naïve B cells demonstrated impaired TLR2- and TLR7- but enhanced TLR9-mediated cytokine production. Significantly fewer newborn naïve B cells underwent CSR to produce IgG, an impairment also noted with IL-21 stimulation. Additionally, co-stimulation via CD40 and TLRs induced greater cytokine production in adult B cells. Thus, while newborn naïve B cells demonstrate adult-level expression of TLRs and CD40, the responses to stimulation of these receptors are distinct. Relatively high expression of TLR9 and impaired CD40-mediated Ig secretion contributes to distinct innate and adaptive immunity of human newborns and may inform novel approaches to early-life immunization.

Inducing dose sparing with inactivated polio virus formulated in adjuvant CAF01

The development of new low cost inactivated polio virus based vaccines (IPV) is a high priority, and will be required to eradicate polio. In addition, such a vaccine constitutes the only realistic polio vaccine in the post-eradication era. One way to reduce the cost of a vaccine is to increase immunogenicity by use of adjuvants. The CAF01 adjuvant has previously been shown to be a safe and potent adjuvant with several antigens, and here we show that in mice IPV formulated with CAF01 induced increased systemic protective immunity measured by binding and neutralization antibody titers in serum. CAF01 also influenced the kinetics of both the cellular and humoral response against IPV to produce a faster, as well as a stronger, response, dominated by IgG2a, IgG2b, and IgG2c isotypes as well as IPV specific T cells secreting IFN-γ/IL-2. Finally, as intestinal immunity is also a priority of polio vaccines, we present a vaccine strategy based on simultaneous priming at an intradermal and an intramuscular site that generate intestinal immune responses against polio virus. Taken together, the IPV-CAF01 formulation constitutes a new promising vaccine against polio with the ability to generate strong humoral and cellular immunity against the polio virus.

Synergistic induction of interferon α through TLR-3 and TLR-9 agonists stimulates immune responses against measles virus in neonatal cotton rats

Immunization of neonates is problematic because of the immaturity of their immune system and the presence of maternal antibodies, both of which affect B cell responses. We tested the effects of co-administration of measles vaccine with a combination of TLR-3 (pI:C) and TLR-9 (ODN2216, optimized for human TLR-9) agonists on the ability to induce an effective immune response in neonatal cotton rats. TLR-9 expression in cotton rat lymphocytes was at the same low level as in human lymphocytes, which is in contrast to mice that express higher levels. TLR-3 expression levels were comparable between cotton rats, mice, and humans. A combination of TLR-3 and TLR-9 agonists synergistically induced high levels of type I interferon in neonatal spleen cells and higher levels of IL-10 as compared to adult spleen cells. Previously, it was shown that type I interferon stimulates B cell generation and antibody secretion in vitro and in vivo, and that IL-10 has immunomodulatory effects. The simultaneous induction of both type I interferon and IL-10 indicated that this immunization regimen could be both effective and safe. Neonatal cotton rats did not generate neutralizing antibodies after measles vaccination in the first week of life (although a T cell response was detectable). However, co-administration of the TLR-3 and TLR-9 agonist combination with measles vaccine in neonatal cotton rats induced neutralizing antibody responses comparable to those after adult immunization. This immunization regimen was also effective in neonatal cotton rats in the presence of natural maternal antibodies, although antibody titers were lower than those after immunization in the absence of maternal antibodies.

Offspring IgE responses are influenced by levels of maternal IgG transferred in early life

PROBLEM

Maternal immune responses may interfere with offspring allergy development as maternal immunization may suppress IgE development, while maternal allergy may promote allergy. Therefore, we investigated the effect of two different maternal treatments on airway allergy in female and male offspring.

METHOD OF STUDY

Pregnant mice were immunized (IMM) with ovalbumin (OVA) or immunized and airway-challenged (IMM+AI). At different ages, airway allergy to OVA was induced in offspring by intranasal sensitization.

RESULTS

Maternal IgG1 was found at higher levels in IMM+AI than in IMM offspring. After sensitization, the suppression of OVA-specific IgE and IgG1 was complete in juvenile offspring but waned with age concurrently with maternal IgG1 levels. Cytokine secretion, lung inflammation, and B cell priming were not suppressed although IgE responses were.

CONCLUSIONS

High compared with low levels of maternal IgG1 were associated with lower TH 2 antibody production after adult offspring were re-exposed to OVA. Thus, offspring allergy-related responses appeared to be shaped by maternal antibody levels.

Measles humoral and cell-mediated immunity in children aged 5-10 years after primary measles immunization administered at 6 or 9 months of age

BACKGROUND

Given the high infant measles mortality rate, there is interest in whether a measles immunization regimen beginning at <12 months of age provides lasting immunity.

METHODS

Measles-specific immune responses were evaluated in 70 children aged 5-10 years after primary measles vaccine administered at 6, 9, or 12 months.

RESULTS

At 5-10 years of age, the stimulation index for measles T-cell proliferation was 11.4 (SE, 1.3), 10.9 (SE, 1.5), and 14.4 (SE 2.1) when the first measles dose was given at 6, 9, or 12 months, respectively. Neutralizing antibody concentration (geometric mean titer [GMT]) in those immunized at 6 months of age was 125 mIU/mL (95% confidence interval [CI], 42-377) in the presence of passive antibodies (PAs) and 335 mIU/mL (95% CI, 211-531) in those without PAs; in those immunized at 9 months, GMTs were 186 mIU/mL (95% CI, 103-335) and 1080 mIU/mL (95% CI, 642-1827) in the presence and absence of PAs, respectively. The GMT was 707 mIU/mL (95% CI, 456-1095) when vaccine was administered at 12 months (P ≤ .04).

CONCLUSIONS

Measles-specific T-cell responses were sustained at 5-10 years of age regardless of age at time of primary measles immunization. Neutralizing antibody concentrations were lower in cohorts given the first vaccine dose at 6 months of age and in the presence of PAs; however, responses could be boosted by subsequent doses. Starting measles vaccination at <12 months of age may be beneficial during measles outbreaks or in endemic areas.

The status of live viral vaccination in early life

The need for neonatal vaccines is supported by the high disease burden during the first year of life particularly in the first month. Two-thirds of childhood deaths are attributable to infectious diseases of which viruses represent key pathogens. Many infectious diseases have the highest incidence, severity and mortality in the first months of life, and therefore early life vaccination would provide significant protection and life savings. For some childhood viral diseases successful vaccines exist, such as against measles, mumps, rubella, varicella, influenza poliovirus, and rotavirus, but their use in the first year particularly at birth is not yet practiced. Vaccines against other key pathogens continue to elude scientists such as against respiratory syncytial virus. The obstacles for early and neonatal vaccination are complex and include host factors, such as a developing immune system and the interference of passively acquired antibodies, as well vaccine-specific issues, such as optimal route of administration, titer and dosing requirements. Importantly, additional host and infrastructure barriers also present obstacles to neonatal vaccination in the developing world where morbidity and mortality rates are highest. This review will highlight the current live viral vaccines and their use in the first year of life, focusing on efficacy and entertaining the barriers that exist. It is important to understand the successes of current vaccines and use this knowledge to determine strategies that are successful in young infants and for the development of new vaccines for use in early life.

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.

Co-expression of ubiquitin gene and capsid protein gene enhances the potency of DNA immunization of PCV2 in mice

A recombinant plasmid that co-expressed ubiquitin and porcine circovirus type 2 (PCV2) virus capsid protein (Cap), denoted as pc-Ub-Cap, and a plasmid encoding PCV2 virus Cap alone, denoted as pc-Cap, were transfected into 293T cells. Indirect immunofluorescence (IIF) and confocal microscopy were performed to measure the cellular expression of Cap. Three groups of mice were then vaccinated once every three weeks for a total of three doses with pc-Ub-Cap, pc-Cap or the empty vector pCAGGS, followed by challenging all mice intraperitoneally with 0.5 mL 10^6.5 TCID₅₀/mL PCV2. To characterize the protective immune response against PCV2 infection in mice, assays of antibody titer (including different IgG isotypes), flow cytometric analysis (FCM), lymphocyte proliferation, cytokine production and viremia were evaluated. The results showed that pc-Ub-Cap and pc-Cap were efficiently expressed in 293T cells. However, pc-Ub-Cap-vaccinated animals had a significantly higher level of Cap-specific antibody and induced a stronger Th1 type cellular immune response than did pc-Cap-vaccinated animals, suggesting that ubiquitin conjugation improved both the cellular and humoral immune responses. Additionally, viral replication in blood was lower in the pc-Ub-Cap-vaccinated group than in the pc-Cap and empty vector groups, suggesting that the protective immunity induced by pc-Ub-Cap is superior to that induced by pc-Cap.

Immunogenicity of recombinant hepatitis B vaccine: comparison of two different vaccination schedules

BACKGROUND

Neonatal immunization with hepatitis B (HB) vaccine induces protective levels of antibody (anti-HBs > or =10 IU/L) in a majority of vaccines. However, the duration of protection after HB vaccination in infants is unknown. A smaller proportion of children vaccinated beginning at birth with three doses of HB vaccine were found to have protective titers 5-10 years after initial vaccination. Long-term efficacy of HB vaccine depends mainly on peak antibody levels after vaccination, and subjects were observed to have lower levels of antibodies if they received the first dose of vaccine immediately after birth. The aim of our study was to compare the immunogenicity of two different HB vaccine schedules in infants born to HB surface antigen-negative mothers.

METHODS

Anti-HBs titers in infants vaccinated with two different schedules were compared. Infants were vaccinated at 0, 2, and 9 months (group 1) or at 2, 4, and 9 months (group 2). In total, 267 blood samples were analyzed at a mean of 14.20 +/- 2.39 months after the third vaccine dose. Sera were tested for hepatitis B surface antigen (HBsAg), hepatitis B surface antibody (anti-HBs), and hepatitis B core antibody (anti-HBc) using commercial enzyme immunoassay kits.

RESULTS

The geometric mean titers for anti-HBs were 95.00 and 379.51 IU/L and the rates of anti-HBs more than > or =100 IU/L were 57.7 and 94.9% in group 1 and 2 infants, respectively.

CONCLUSION

Delaying the first dose of the HB vaccine until 2 months after birth produces a higher immune response and can provide longer term protection.

Immunotherapeutic applications of CpG oligodeoxynucleotide TLR9 agonists

Toll-like receptor 9 (TLR9) agonists have demonstrated substantial potential as vaccine adjuvants, and as mono- or combination therapies for the treatment of cancer and infectious and allergic diseases. Commonly referred to as CpG oligodeoxynucleotides (ODN), TLR9 agonists directly induce the activation and maturation of plasmacytoid dendritic cells and enhance differentiation of B cells into antibody-secreting plasma cells. Preclinical and early clinical data support the use of TLR9 agonists as vaccine adjuvants, where they can enhance both the humoral and cellular responses to diverse antigens. In mouse tumor models TLR9 agonists have shown activity not only as monotherapy, but also in combination with multiple other therapies including vaccines, antibodies, cellular therapies, other immunotherapies, antiangiogenic agents, radiotherapy, cryotherapy, and some chemotherapies. Phase I and II clinical trials have indicated that these agents have antitumor activity as single agents and enhance the development of antitumor T-cell responses when used as therapeutic vaccine adjuvants. CpG ODN have shown benefit in multiple rodent and primate models of asthma and other allergic diseases, with encouraging results in some early human clinical trials. Although their potential clinical contributions are enormous, the safety and efficacy of these TLR9 agonists in humans remain to be determined.

Adjuvants LT-K63 and CpG enhance the activation of dendritic cells in neonatal mice

Dendritic cells (DC) play a major role in the priming of T cells and initiating specific immune responses. We assessed the effects of the adjuvants LT-K63 and CpG on neonatal DC in vivo and in vitro. Cytokine levels (IL-10, IL-12p70 and IL-12p40/IL-23p40) were measured and the expression of the activation markers CD86, CD40 and MHCII on CD11c+ DC was analysed by using FACS. The proportion of MHCII high CD11c+ DC was higher in neonatal mice immunized with a pneumococcal conjugate (PncTT) and LT-K63 or CpG compared with that when PncTT was alone. In vitro stimulation with LT-K63 enhanced the expression of CD86 more on CD11c+ DC from spleens of mice immunized as neonates than those immunized as adults, whereas in vitro stimulation with CpG enhanced the expression of CD86 and CD40 on CD11c+ DC similarly in both age groups. CpG stimulation in vitro enhanced IL-10 and IL-12(p70) production in mice immunized as neonates with PncTT and either adjuvant, but not PncTT alone. The adjuvants LT-K63 and CpG enhance the activation of CD11c+ DC in mice immunized as neonates and can thereby overcome one of the limiting factors in the initiation of the immune response to conjugate vaccines in early life. The fact that neonatal DC are more susceptible to stimulation with either adjuvant, LT-K63 or CpG, could imply that neonatal CD11c+ DC are more easily activated than adult CD11c+ DC, and /or be a consequence of the predominance of different DC subsets in neonatal and adult mice.

Strategies to link innate and adaptive immunity when designing vaccine adjuvants

Adjuvants are important components of vaccine formulations. Their functions include the delivery of antigen, recruitment of specific immune cells to the site of immunization, activation of these cells to create an inflammatory microenvironment, and maturation of antigen-presenting cells for enhancement of antigen-uptake and -presentation in secondary lymphoid tissues. Adjuvants include a large family of molecules and substances, many of which were developed empirically and without knowledge of their specific mechanisms of action. The discovery of pattern recognition receptors including Toll-like-, nucleotide-binding oligomerization domain (NOD)- and mannose-receptors, has significantly advanced the field of adjuvant research. It is now clear that effective adjuvants link innate and adaptive immunity by signaling through a combination of pathogen recognition receptors (PRRs). Research in our lab is focused towards the development of novel adjuvants and immunomodulators that can be used to improve neonatal vaccines for humans and animals. Using a neonatal pig model for pertussis, we are currently analyzing the effectiveness of host defence peptides (HDPs), bacterial DNA and polyphosphazenes as vaccine adjuvants.

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.

Enhancement of infectious disease vaccines through TLR9-dependent recognition of CpG DNA

The adaptive immune system-with its remarkable ability to generate antigen-specific antibodies and T lymphocytes against pathogens never before "seen" by an organism-is one of the marvels of evolution. However, to generate these responses, the adaptive immune system requires activation by the innate immune system. Toll-like receptors (TLRs) are perhaps the best-understood family of innate immune receptors for detecting infections and stimulating adaptive immune responses. TLR9 appears to have evolved to recognize infections by a subtle structural difference between eukaryotic and prokaryotic/viral DNA; only the former frequently methylates CpG dinucleotides. Used as vaccine adjuvants, synthetic oligodeoxynucleotide (ODN) ligands for TLR9--CpG ODN--greatly enhance the speed and strength of the immune responses to vaccination.

Surgical excision combined with autologous whole tumor cell vaccination is an effective therapy for murine neuroblastoma

BACKGROUND

Although a whole tumor cell vaccine strategy based on the synergistic action of granulocyte macrophage-colony-stimulating factor (GM-CSF) transduced tumor cells and CpG oligodeoxynucleotides induces potent tumor-specific immunity, such therapy is not curative in the face of large established tumors.

PURPOSE

The primary goal of this study was to determine if combining surgical resection of the tumor with whole tumor cell vaccination is an effective therapeutic strategy for established neuroblastoma. We also wished to determine if the phenotype of the immune response generated by this vaccine strategy was altered by the presence of bulky established tumor.

METHODS

The murine neuroblastoma model was used in which syngeneic Neuro-2a was grown subcutaneously in A/J mouse. The whole tumor cell vaccine consisted of irradiated Neuro-2a as the vehicle for tumor antigens admixed with GM-CSF and CpG oligonucleotides (100 microg).

RESULTS

In the presence of large tumors, dendritic cells were effectively activated by the vaccine, but secretion of intereferon-gamma from vaccinated splenocytes in response to antigen stimulation was suppressed. The tumor's inhibitory effect on interferon-gamma production from vaccinated splenocytes was reversed after resection of the primary tumor. The use of prepared GM-CSF-secreting bystander cells simplified production of an autologous whole tumor cell vaccine that was remarkably effective in curing large tumors when combined with tumor excision.

CONCLUSIONS

These findings suggest that at least part of the immunosuppressive effects of the cancer can be reversed after surgical excision of the primary tumor. Thus, in the context of minimal residual disease, this dendritic cell-targeted immunotherapeutic approach may prove effective for the treatment of neuroblastoma.

Therapeutic potential of Toll-like receptor 9 activation

In the decade since the discovery that mouse B cells respond to certain unmethylated CpG dinucleotides in bacterial DNA, a specific receptor for these 'CpG motifs' has been identified, Toll-like receptor 9 (TLR9), and a new approach to immunotherapy has moved into the clinic based on the use of synthetic oligodeoxynucleotides (ODN) as TLR9 agonists. This review highlights the current understanding of the mechanism of action of these CpG ODN, and provides an overview of the preclinical data and early human clinical trial results using these drugs to improve vaccines and treat cancer, infectious disease and allergy/asthma.

High titers of circulating maternal antibodies suppress effector and memory B-cell responses induced by an attenuated rotavirus priming and rotavirus-like particle-immunostimulating complex boosting vaccine regimen

We investigated maternal antibody (MatAb) effects on protection and immune responses to rotavirus vaccines. Gnotobiotic pigs were injected intraperitoneally at birth with pooled serum from sows hyperimmunized with human rotavirus (HRV); control pigs received no sow serum. Pigs with or without MatAbs received either sequential attenuated HRV (AttHRV) oral priming and intranasal boosting with VP2/VP6 virus-like particle (VLP)-immunostimulating complex (ISCOM) (AttHRV/VLP) or intranasal VLP-ISCOM prime/boost (VLP) vaccines at 3 to 5 days of age. Subsets of pigs were challenged at 28 or 42 days postinoculation with virulent Wa HRV to assess protection. Isotype-specific antibody-secreting cell (ASC) responses to HRV were quantitated by enzyme-linked immunospot assay to measure effector and memory B-cell responses in intestinal and systemic lymphoid tissues pre- and/or postchallenge. Protection rates against HRV challenge (contributed by active immunity and passive circulating MatAbs) were consistently (but not significantly) lower in the MatAb-AttHRV/VLP groups than in the corresponding groups without MatAbs. Intestinal B-cell responses in the MatAb-AttHRV/VLP group were most suppressed with significantly reduced or no intestinal immunoglobulin A (IgA) and IgG effector and memory B-cell responses or antibody titers pre- and postchallenge. This suppression was not alleviated but was enhanced after extending vaccination/challenge from 28 to 42 days. In pigs vaccinated with nonreplicating VLP alone that failed to induce protection, MatAb effects differed, with intestinal and systemic IgG ASCs and prechallenge memory B cells suppressed but the low intestinal IgA and IgM ASC responses unaffected. Thus, we demonstrate that MatAbs differentially affect both replicating and nonreplicating HRV vaccines and suggest mechanisms of MatAb interference. This information should facilitate vaccine design to overcome MatAb suppression.

CPG 7909 adjuvant improves hepatitis B virus vaccine seroprotection in antiretroviral-treated HIV-infected adults

BACKGROUND

HIV patients are vaccine hyporesponsive.

METHODS

We evaluated CPG 7909, a synthetic oligodeoxynucleotide containing immunostimulatory CpG motifs, as an adjuvant to Engerix-B. A randomized, double-blind controlled trial was conducted to determine safety and hepatitis B virus (HBV) immunogenicity in adult HIV subjects on effective antiretroviral therapy. HBV-susceptible subjects, half of whom had failed previous vaccination, were vaccinated at 0, 1 and 2 months with a double dose of Engerix-B with/without (+/-) 1 mg CPG 7909. HBV immune subjects (anti-HBsAg titres > or = 10 mIU/l) received either CPG 7909 alone or saline. Safety, anti-HBs titres and lymphocyte proliferation response (LPR) to HBsAg were assessed over 12 months.

RESULTS

Vaccinations with Engerix B +/- CPG 7909 were well tolerated locally and systemically. HIV suppression and CD4 cell counts were maintained. Anti-HBs titers were significantly higher in vaccinees receiving CPG 7909, for all time points after the second dose. Seroprotective titres (> or = 10 mIU/ml) by 6 and 8 weeks, and 12 months were found in 89, 89, and 100% of subjects receiving CPG 7909 compared to 53, 42, and 63% of controls respectively (P = 0.029, 0.005, and 0.008). HBsAg LPR was increased at all time-points up to 12 months after vaccination with addition of CPG 7909 (P < 0.05).

CONCLUSIONS

Addition of CPG 7909 achieves rapid, higher, and sustained HBV seroprotection and increases HBV-specific T helper cell response to HBV vaccine in HIV subjects. These results confirm a potential adjuvant role for CPG 7909 in vaccine hyporesponsive populations including those living with HIV.

CPG 7909, an immunostimulatory TLR9 agonist oligodeoxynucleotide, as adjuvant to Engerix-B HBV vaccine in healthy adults: a double-blind phase I/II study

Oligodeoxynucleotides containing immunostimulatory CpG motifs (CpG ODN) act as potent Th1-like immune enhancers with many antigens in animal models. We have extended these observations to the first clinical evaluation of the safety, tolerability and immunogenicity of CPG 7909 when added to a commercial HBV vaccine. In a randomized, double-blind phase I dose escalation study, healthy volunteers aged 18-35 years were vaccinated at 0, 4 and 24 weeks by intramuscular injection with Engerix-B (GlaxoSmithKline). The regular adult dose of 20 microg recombinant hepatitis B surface antigen (HBsAg) adsorbed to alum was administered mixed with saline (control) or with CPG 7909 at one of three doses (0.125, 0.5 or 1.0 mg). HBsAg-specific antibody responses (anti-HBs) appeared significantly sooner and were significantly higher at all timepoints up to and including 24 weeks in CPG 7909 recipients compared to control subjects (p< or = 0.001). Strikingly, most CpG 7909-vaccinated subjects developed protective levels of anti-HBs IgG within just two weeks of the priming vaccine dose. A trend towards higher rates of positive cytotoxic T cell lymphocyte responses was noted in the two higher dose groups of CPG 7909 compared to controls. The most frequently reported adverse events were injection site reactions, flu-like symptoms and headache. While these were more frequent in CPG 7909 groups than in the control group (p<0.0001), most were reported to be of mild to moderate intensity regardless of group. In summary, CPG 7909 as an adjuvant to Engerix-B was well-tolerated and enhanced vaccine immunogenicity. CPG 7909 may allow the development of a two-dose prophylactic HBV vaccine.

Inhibition of 19-kDa C-terminal region of merozoite surface protein-1-specific antibody responses in neonatal pups by maternally derived 19-kDa C-terminal region of merozoite surface protein-1-specific antibodies but not whole parasite-specific antibodies

Immunizing pregnant women with a malaria vaccine is one approach to protecting the mother and her offspring from malaria infection. However, specific maternal Abs generated in response to vaccination and transferred to the fetus may interfere with the infant's ability to respond to the same vaccine. Using a murine model of malaria, we examined the effect of maternal 19-kDa C-terminal region of merozoite surface protein-1 (MSP1(19)) and Plasmodium yoelii Abs on the pups' ability to respond to immunization with MSP1(19). Maternal MSP1(19)-specific Abs but not P. yoelii-specific Abs inhibited Ab production following MSP1(19) immunization in 2-wk-old pups. This inhibition was correlated with the amount of maternal MSP1(19) Ab present in the pup at the time of immunization and was due to fewer specific B cells. Passively acquired Ab most likely inhibited the development of an Ab response by blocking access to critical B cell epitopes. If a neonate's ability to respond to MSP1(19) vaccination depends on the level of maternal Abs present at the time of vaccination, it may be necessary to delay immunization until Abs specific for the vaccinating Ag have decreased.

Immunisation against PCV2 structural protein by DNA vaccination of mice

Porcine circovirus type 2 (PCV2) is the causative agent of an emerging swine disease, postweaning multisystemic wasting syndrome (PMWS). The disease affects primarily 5-12-weeks-old pigs which might suggest that infection with PCV2 occurs when the level of maternal antibodies have declined to sub-protective levels around weaning at 3-5-weeks of age. If immunoprophylaxis is to be effective, an immunisation method capable of breaking through maternal immunity must be employed. In this study, we have developed and investigated the potential of a DNA vaccination approach to be one such method. The gene encoding the capsid protein of PCV2 was cloned in a DNA vaccination plasmid and expression of capsid protein was demonstrated in vitro. Mice were gene gun vaccinated three timesand all mice responded serologically by raising antibodies against PCV2. The results suggest, that DNA based vaccination might offer opportunities for vaccination of piglets against PCV2.

DNA vaccination of infants in the presence of maternal antibody: a measles model in the primate

To eradicate measles in developing nations a vaccine capable of being administered at birth may be necessary. We immunized newborn rhesus macaques with naked DNA encoding the measles virus hemagglutinin, fusion and nucleoprotein genes. Prior to vaccination we passively transferred measles immunoglobulin to mimic maternal antibody. In the presence or absence of measles immunoglobulin, 23 of 25 infant macaques had detectable cell mediated immunity and 16 had protective levels of neutralizing antibody. The co-administration of an IL-2/IgG plasmid augmented the vaccine, increasing cell mediated immunity in all infants and increasing the antibody response in infants vaccinated without immunoglobulin. We show for the first time that DNA vaccination can protect a newborn primate from the high-level viremia that correlates with severe measles, even in the presence of maternal antibody. Further, the addition of a molecular IL-2 adjuvant augments this DNA vaccine.

CPG ODN allows lower dose of antigen against hepatitis B surface antigen in BALB/c mice

We have evaluated alum, immunostimulatory cytosine guanine dinucleotide-containing oligodeoxy-nucleotides (CPG ODN), and an alum/CPG ODN combination as adjuvants with hepatitis B surface antigen, to compare their potential to allow lower doses of antigen to be used for induction of humoral responses. BALB/c mice were immunized by intramuscular injection with 0.01, 0.1 or 1.0 micro g recombinant hepatitis B surface antigen without adjuvant or with alum and/or CPG ODN added. When given without adjuvant or with alum, each 10-fold decrease in amount of antigen resulted in a similarly reduced titre of antibody against hepatitis B surface antigen. In contrast, CPG ODN, on its own or combined with alum, allowed high anti-hepatitis B surface antigen titres even with a 1000-fold reduction in amount of antigen. These findings may have important immunological and economical consequences for vaccine development.

Genetic immunization of neonates

The vaccination of neonates is generally difficult due to immaturity of the immune system, higher susceptibility to tolerance and potential negative interference of maternal antibodies. Studies carried out in rodents and non-human primates showed that plasmid vaccines expressing microbial antigens, rather than inducing tolerance, triggered significant humoral and cellular immunity with a Th1 component. The ability of bacterial CpG motifs to activate immature antigen-presenting cells is critical for the neonatal immunogenicity of DNA vaccines. In addition, the endogenous production of antigen subsequent to transfection of antigen-presenting cells may explain the lack of inhibition by maternal antibodies of cellular responses. Together, these features make the plasmid vaccines an appealing strategy to prime immune responses against foreign pathogens, during early life. In combination with subsequent boosting using conventional vaccines, DNA vaccine-based regimens may provide a qualitatively superior immunity against microbes. Thorough understanding of immunomodulatory properties of plasmid-vectors may extend their use for early prophylaxis of inflammatory disorders.