Replicating viral vectors as HIV vaccines: summary report from the IAVI-sponsored satellite symposium at the AIDS vaccine 2009 conference.

In October 2009, The International AIDS Vaccine Initiative (IAVI) convened a satellite symposium entitled 'Replicating Viral Vectors for use in AIDS Vaccines' at the AIDS Vaccine 2009 Conference in Paris. The purpose of the symposium was to gather together researchers, representatives from regulatory agencies, and vaccine developers to discuss issues related to advancement of replication-competent viral vector- based HIV vaccines into clinical trials. The meeting introduced the rationale for accelerating the development of replicating viral vectors for use as AIDS vaccines. It noted that the EMEA recently published draft guidelines that are an important first step in providing guidance for advancing live viral vectors into clinical development. Presentations included case studies and development challenges for viral vector-based vaccine candidates. These product development challenges included cell substrates used for vaccine manufacturing, the testing needed to assess vaccine safety, conducting clinical trials with live vectors, and assessment of vaccination risk versus benefit. More in depth discussion of risk and benefit highlighted the fact that AIDS vaccine efficacy trials must be conducted in the developing world where HIV incidence is greatest and how inequities in global health dramatically influence the political and social environment in developing countries.

Induction of immune responses to HIV-1 by canarypox virus (ALVAC) HIV-1 and gp120 SF-2 recombinant vaccines in uninfected volunteers. NIAID AIDS Vaccine Evaluation Group.

OBJECTIVE: To determine the ability of live attenuated canarypox virus expressing HIV antigens to induce CD8+ cytotoxic T-cell responses and to prime for neutralizing antibody responses to boosting with purified recombinant gp120 subunit vaccine. DESIGN: A prospective, double-blind, randomized, immunogenicity and safety study was conducted in healthy adults at low risk for acquiring HIV infection and who were seronegative for HIV. METHODS: CD8+ cytotoxic T-cells directed against Env or Gag expressing target cells were measured after live recombinant canarypox-HIV-1 vaccine priming (vaccine given at days 0, 7, 14 and 21). Neutralizing antibodies were measured after subunit boosting (vaccine given at days 28 and 84). RESULTS: CD8+ CTL were induced in 64% of volunteers by the live recombinant canarypox-HIV-1 vaccine. All volunteers who received two doses of subunit vaccine after live recombinant canarypox priming developed neutralizing antibodies directed against laboratory strains of HIV-1 and seven out of eight volunteers tested developed neutralizing antibodies to the primary isolate, BZ167, but to none of eight other primary isolates. Unprimed controls had low or absent neutralizing antibodies after two doses of subunit vaccine. CONCLUSIONS: The live canarypox vector was safe, stimulated cytotoxic T-cells and primed for a vigorous neutralizing antibody response upon boosting with subunit gp120 vaccine. This vaccine combination should be evaluated further for inducing protection against HIV infection.

Development and standardization of methods to evaluate the antibody response to an HIV-1 candidate vaccine in secretions and sera of seronegative vaccine recipients.

Enzyme-linked immunosorbent assays (ELISA) were developed to test, in serum and mucosal samples, total IgG, total IgA, serum albumin, and anti-gp120 MN and anti-p24 LAI IgG and IgA levels. These ELISAs were optimized according to reagents and experimental conditions. Inter- and intra-assay coefficients of variation ranged from 3.3% to 18.6%. The ELISA results were linear and precise, and for anti-HIV-1 IgG and IgA, the analytical recovery was close to 100%. For IgG and IgA titration against gp120 MN and p24 LAI, standards were made using pooled sera or gammaglobulins with assigned titres in ELISA units per ml (EU/ml). These standards were used to obtain a linear regression curve that could then be used to obtain the titres of experimental samples. The cut-offs for positivity were determined for sera and mucosal fluid using healthy controls. Validation conditions were defined for ELISAs, and samples that did not satisfy these conditions were retested. Measurement of total IgG and IgA allowed normalization and comparison of the results of specific immunoglobulin levels between different samples. Serum albumin was tested as a marker of transudation from serum to mucosal fluid, allowing calculation of the relative coefficient of excretion, which is one element required to determine the origin of the immunoglobulin detected in mucosal samples. These ELISAs were developed with samples from HIV-1-infected and healthy subjects. We now have the tools to study and understand mucosal immunity in seronegative subjects vaccinated with an HIV-1 candidate vaccine.

Safety and immunogenicity of a recombinant HIV type 1 glycoprotein 160 boosted by a V3 synthetic peptide in HIV-negative volunteers.

The safety and the immunogenicity of a recombinant hybrid envelope glycoprotein MN/LAI (rgp160) followed by booster injections of a V3 (MN) linear peptide were evaluated in HIV-negative adults at low risk for HIV infection. Volunteers received either rgp160 in alum at 0, 1, and 6 months (group A), rgp160 at 0 and 1 months followed by V3 at 3 and 6 months formulated in alum (group B), or in Freund's incomplete adjuvant (FIA) (group C). Local and systemic reactions were mild to moderate and resolved within the first 72 hr after immunization. No significant biological changes (routine tests and autoantibodies) were observed. One month after the last injection in either group, neutralizing antibodies (NAs) against the HIV-1 MN isolate were detected in 4 of 5 (A), 7 of 10 (B), and 10 of 10 (C) subjects with significantly higher geometric mean titers in the latter group. Four of nine sera with the highest NA titers against MN weakly cross-neutralized the HIV-1 SF2 isolate; none had NA against the HIV-1 LAI strain or against a North American primary isolate. Specific lymphocyte T cell proliferation to rgp160 was detected in 92% of the subjects after the second injection of rgp160 and in 80% of them 12 months after the first injection. A weak and short-lived envelope-specific CD(4+)-mediated cytotoxic lymphocyte activity was detected at certain time points in few subjects. This prime-boost vaccine approach using rgp160 followed by a V3 peptide was safe in humans, and was able to elicit high levels of neutralizing antibodies and a strong and persistent T cell lymphoproliferative response to rgp160 and to V3. However, the neutralization response was restricted to the homologous HIV-1 strain and little env-specific cytotoxic activity was induced.

A prime-boost approach to HIV preventive vaccine using a recombinant canarypox virus expressing glycoprotein 160 (MN) followed by a recombinant glycoprotein 160 (MN/LAI). The AGIS Group, and l'Agence Nationale de Recherche sur le SIDA.

The safety and the immunogenicity of a recombinant canarypox live vector expressing the human immunodeficiency virus type 1 (HIV-1) gp160 gene from the MN isolate, ALVAC-HIV (vCP125), followed by booster injections of a soluble recombinant hybrid envelope glycoprotein MN/LAI (rgp160), were evaluated in vaccinia-immune, healthy adults at low risk for acquiring HIV-1 infection. Volunteers (n = 20) received vCP125 (10(6) TCID50) at 0 and 1 month, followed randomly by rgp160 formulated in alum or in Freund's incomplete adjuvant (FIA) at 3 and 6 months. Local and systemic reactions were mild or moderate and resolved within the first 72 hr after immunization. No significant biological changes in routine tests were observed in any volunteer. Two injections of vCP125 did not elicit antibodies. Neutralizing antibodies (NA) against the HIV-1 MN isolate were detected in 65 and 90% of the subjects after the first and the second rgp 160 booster injections, respectively. Six months after the last boost, only 55% were still positive. Seven of 14 sera with the highest NA titers against MN weakly cross-neutralized the HIV-1 SF2 isolate; none had NA against the HIV-1 LAI or against a North American primary isolate. Specific lymphocyte T cell proliferation to rgp 160 was detected in 25% of the subjects after vCP125 and in all subjects after the first booster injection and 12 months after the first injection. An envelope-specific cytotoxic lymphocyte activity was found in 39% of the volunteers and characterized for some of them as CD3+, CD8+, MHC class I restricted. The adjuvant formulation did not influence significantly the immune responses.(ABSTRACT TRUNCATED AT 250 WORDS)

IgG subclass distribution in serum and various mucosal fluids of HIV type 1-infected subjects.

We measured total IgG1, IgG2, IgG3, and IgG4 concentrations by ELISA in serum (S), total saliva (TS), cervicovaginal secretions (CVS), seminal secretions (SPE), and rectal secretions (RS) from either CDC II/III HIV-1-infected subjects or healthy volunteers. Human serum albumin was measured in parallel to calculate the relative coefficient of excretion (RCE). Levels of IgG1 and IgG3 directed against gp120 MN also were measured by ELISA in all samples, and the specific activity (SA) calculated. HIV-1-specific IgG2 and IgG4 were not compared, as total IgG2 and total IgG4 levels in HIV-1-infected subjects were found to be lower than in the healthy controls. Despite substantial interindividual variability, total IgG1 and IgG3 concentrations in all fluids were greater in the HIV-1-infected subjects than in the healthy controls. Calculations of RCE indicated predominantly a transudative origin for IgG subclasses in the different mucosal fluids, except for CVS, in which IgG1, IgG2, and IgG4 was produced locally. The transduction behavior of IgG3 in secretions appears to be different from that of other IgG subclasses. HIV-1-infected subjects were considered positive for IgG1 and IgG3 antibodies against gp120 MN if their antibody levels exceeded the maximum titer measured in the control group. Positive levels of anti-gp120 MN IgG1 were detected for 100% of HIV-1-infected individuals in S, CVS, and SPE, 97% in TS, and 75% in RS. Fewer subjects had positive levels of IgG3 to gp120 MN in their secretions (maximum 67% in CVS). Despite the low concentrations of total IgG3, mean SA values for IgG3 to gp120 MN were greater in secretions than in serum. No significant difference in the SA values for IgG1 to gp120 MN was observed between the different fluids. Only CVS had a local production of HIV-specific IgG1 Our results highlight the importance of an HIV-specific IgG1 and IgG3 immune response in mucosal fluids from HIV-1-infected subjects.

Restricted specificity of anti-V3 antibodies induced in humans by HIV candidate vaccines.

We analyzed the fine specificity of anti-V3 antibodies elicited in three different species (human, guinea pig, and macaque) by various HIV candidate vaccines. Following immunization with recombinant canarypox virus expressing gp160MN or with recombinant gp160MN/LAI, this antibody response was shown to be directed against the NH2-terminal region of the V3 loop. Although this response was increased by a prime-boost regimen using immunization with canarypox expressing gp160 followed by an rgp160 boost, its specificity remained restricted mainly to the recognition of this region of the V3 loop. Pepscan analysis of sera confirmed the results obtained by ELISA and allowed the definition of an immunodominant common binding site for these sera located within the sequence NKRKRIHIGPGR. In contrast to these results, a boost with the V3 peptide was shown to broaden the antibody response and pepscan analysis showed that sera from individuals boosted with the V3 synthetic peptide recognize determinants all along the V3 loop. Similar fine specificity of anti-V3 antibodies was obtained in human, guinea pig, and macaque following immunization by a prime-boost regimen using canarypox recombinants expressing gp160 or gp120 and purified rgp160. In contrast, a V3 synthetic peptide boost stimulated the production of antibodies that recognize multiple epitopes within the V3 loop. Because the induction of antibodies that recognize multiple sites in the V3 loop could be of major importance to neutralize different HIV isolates, these results may have implications for the design and selection of HIV candidate vaccines.

Comparison of the distribution of IgG and IgA antibodies in serum and various mucosal fluids of HIV type 1-infected subjects.

We compared IgG and IgA distribution in serum, three different salivary samples, two different rectal secretion samples, cervicovaginal secretions, and seminal secretions from asymptomatic CDC stage II/III HIV-1-infected subjects (n = 44) and from HIV-1-seronegative volunteers (n = 52). In-house ELISAs were used to measure total IgG and total IgA levels, as well as HIV-specific anti-gp120 MN and anti-p24 LAI IgG and IgA. Human serum albumin was titrated in parallel to calculate the relative coefficient of excretion (RCE). In spite of substantial interindividual variability, total IgG concentrations in all fluids were found to be significantly greater in the HIV-1-infected group than in the seronegative subjects. Calculation of RCE values revealed three different types of mucosal secretion: secretions with no local Ig production, such as sperm; secretions with local production of IgA and transudative origin of IgG, such as salivary and rectal samples; and secretions with local production of both IgG and IgA, such as in cervicovaginal secretions. For all mucosal specimens from HIV-1-infected subjects, the response to HIV-1 was predominantly IgG, with highest titers observed in cervicovaginal secretions (although these were lower than serum levels). In contrast, the specific IgA response appeared weaker in the mucosa than in serum.

Safety and immunogenicity of a live recombinant canarypox virus expressing HIV type 1 gp120 MN MN tm/gag/protease LAI (ALVAC-HIV, vCP205) followed by a p24E-V3 MN synthetic peptide (CLTB-36) administered in healthy volunteers at low risk for HIV infection. AGIS Group and L'Agence Nationale de Recherches sur Le Sida.

A live recombinant canarypox vector expressing HIV-1 gpl20 MN tm/gag/protease LAI (ALVAC-HIV, vCP205) alone or boosted by a p24E-V3 MN synthetic peptide (CLTB-36) was tested in healthy volunteers at low risk for HIV infection for their safety and immunogenicity. Both antigens were well tolerated. ALVAC-HIV (vCP205) induced low levels of neutralizing antibodies against HIV-1 MN in 33% of the volunteers. None of them had detectable neutralizing antibodies against a nonsyncytium-inducing HIV-1 clade B primary isolate (Bx08). After the fourth injection of vCP205, CTL activity was detected in 33% of the volunteers and was directed against Env, Gag, and Pol. This activity was mediated by both CD4+ and CD8+ lymphocytes. On the other hand, the CLTB-36 peptide was poorly immunogenic and induced no neutralizing antibodies or CTLs. Although the ALVAC-HIV (vCP205) and CLTB-36 prime-boost regimen was not optimal, further studies with ALVAC-HIV (vCP205) are warranted because of its clear induction of a cellular immune response and utility as a priming agent for other subunit antigens such as envelope glycoproteins, pseudoparticles, or new peptides.

Assessment of proportional growth of very low birth weight infants fed banked human milk.

Twenty appropriate (mean +/- S.D., gestational age (AGA): 29.9 +/- 1.5 weeks) and 15 small (GA: 34.6 +/- 2.4 weeks) for gestational age (SGA) very low birth weight infants fed banked mature human milk were studied until term for anthropometric parameters: midarm (MAC), chest (CC), head (HC) circumferences, triceps (TSKF) and subscapular (SSKF) skinfold thickness recorded at 15 and 60 s, dynamic skinfold (delta % SKF), muscle (AMA) and fat (AFA) areas, weight and length. In AGA infants, all the parameters at term were significantly lower in extrauterine (EUL) that in intrauterine life (IUL). At term the relative proportion of AFA to total arm area was increased in EUL compared to IUL both in AGA (25.87 +/- 3.8 vs. 23.26 +/- 1.27% respectively, P less than 0.01) and in SGA infants (21.89 +/- 4.63 vs. 18.81 +/- 3.9 respectively, P less than 0.05). SGA infants showed a similar growth in EUL compared to IUL, and a significantly lower AMA and AFA than in AGA infants in EUL. Although HC was in both infants below the 10th centile at term, the ratio weight/HC2 suggests a relative preservation of head growth in EUL compared to IUL (AGA: 20.72 less than 0.87 vs. 22.65 +/- 1.46 respectively, P less than 0.001; SGA; 20.82 +/- 1.16 vs. 21.62 +/- 1.86 respectively, NS). Delta %SKF were negatively correlated with post-conceptional age suggesting a loss of extracellular water in AGA (delta %TSKF: r = -0.287, P less than 0.02) and in SGA infants (delta %TSKF: r = -0.301, P less than 0.02; delta %SSKF: r = -0.316, P less than 0.02). An intrauterine model of discrimination between AGA and SGA infants does not apply to EUL. An equation was established in SGA infants with the best discriminant parameters giving a predictive post-conceptional age: post-conceptual age (PCA) (weeks) = 0.276 HC (cm) + 0.723 CC (cm) - 0.122 MAC (cm) + 0.5 TSKF (mm) + 10.173, (r = 0.867, P less than 0.001) allowing a clear discrimination between AGA and SGA infants. These results suggest that infants show quite different growth patterns between IUL and EUL both for AGA and SGA infants.

Anthropometric assessment of nutritional status in newborn infants. Discriminative value of mid arm circumference and of skinfold thickness.

74 appropriate-for-gestational age (AGA) and 22 small-for-gestational age (SGA) caucasian infants were studied for anthropometric parameters: mid arm circumference (MAC), triceps and subscapular skinfold thickness (TSKF and SSKF) recorded at 15 and 60 s, chest circumference (cc), head circumference, birth weight and length. MAC is highly correlated with birth weight either in AGA (r = 0.936; P less than 0.001) or in SGA infants (r = 0.860; P less than 0.001). MAC is also correlated with gestational age in AGA (r = 0.850; P less than 0.001) and SGA infants (r = 0.76; P less than 0.001). Similar correlations were found between TSKF, SSKF and birth weight or gestational age. Arm muscle and fat areas are also positively correlated with birth weight and gestational age, in AGA and SGA infants. A multiple regression analysis of our data allowed a classification of the best discriminant anthropometric parameters between AGA and SGA infants. MAC, SSKF15, SSKF60 and chest circumference were selected. An equation was established in AGA infants with these four parameters giving a predictive gestational age: gestational age (weeks) = 1.216 MAC (cm)-3.588 SSKF15 (mm) + 0.263 CC (cm) + 17.9. The ratio of predicted gestational age to the real gestational age was 1.0 +/- 0.044 in AGA versus 0.896 +/- 0.034 in SGA infants. Our data suggest that MAC and SSKF provide a simple measure of body composition of neonates and a useful tool for determining the degree of maturity of a newborn independent of birth weight.

[Recombinant vaccine and extracting vaccine against hepatitis B in patients with kidney insufficiency: comparative immunogenicity]. / Vaccin recombinant et vaccin d'extraction contre l'hépatite B chez l'insuffisant rénal: immunogénicité comparée.

OBJECTIVES: Patients with chronic renal failure respond rather poorly to hepatitis B vaccines. A better response could be expected from recombinant vaccines including both the S and the pre-S2 antigens. We therefore prospectively compared the immunogenicity of plasma-derived Hevac B vaccine (H) with that of recombinant GenHevac B vaccine (G). METHODS: Vaccinations were performed in 120 non-dialyzed patients with chronic renal failure. The patients were randomly divided into two groups. Group G included 60 patients (24 males, mean age 58 +/- 16 years, mean creatinine clearance 25.3 +/- 12.6 ml/min) who were given the Hevac B vaccine at the dose of 5 micrograms. Group H included 60 patients (31 males, mean age 60 +/- 15 years, mean creatinine clearance 24.4 +/- 11.1 ml/min) who were given GenHevac B vaccine at the dose of 20 micrograms. All vaccinations were repeated at 0, 1, 2, 4 and 12 months. RESULTS: Following the fourth injection, seroconversion (anti-Hbs > or = 2 mlU/ml) was observed in 50/59 (85%) of the patients in group G versus 38/58 (67%) in group H (p < 0.02). Seroprotection (> or = 10 mlU/ml) was obtained in 42/59 (71%) vs 34/58 (59%), (NS) in the two groups respectively with a geometric mean titer of 112 versus 229 mlU/ml (NS) in responders. Following the booster injection at the 12th month, seroconversion was achieved in 48/51 (94%) vs 40/53 (76%) (p < 0.01) and seroprotection in 84% vs 70% (p = 0.053) respectively. The mean geometric titers were 879 and 1001 mlU/ml. CONCLUSIONS: Recombinant GenHevac B vaccine elicits seroconversion and seroprotection in a higher proportion of patients with chronic renal failure than the plasma-derived Hevac B vaccine, with comparably high antibody titers in responders. Therefore, GenHevac B vaccine should be recommended for vaccinating patients with chronic renal failure against hepatitis B.

[Breast feeding and birth spacing in Burundi: an approach]. / Allaitement au sein et espacement des naissances au Burundi: une approche.

Breast-feeding (BFD), post-partum amenorrhea (PPA), and birth interval (BI) were studied in 247 mothers from Burundi (159 rural and 88 urban). BFD was higher in rural than in urban areas (23.8 +/- 6.8 vs 16.5 +/- 7.2 mths, p less than 0.001), as for PPA (16.9 +/- 8.5 vs 8.9 +/- 8 mths, p less than 0.001) and Bl (29 +/- 11 vs 25.7 +/- 10.7 mths, p less than 0.01). PPA of non exclusively breast-feeding (NEB) mothers was lower than that of the other mothers (5.7 +/- 6.5 vs 13.9 +/- 9 mths, p less than 0.001). The proportion of mothers with PPA less than or equal to 12 months was higher in NEB mothers (88.9% vs 49%, p less than 0.001). The relative risk of pregnancy 9 to 12 mths after a birth was 4 times higher for these mothers (28% vs 9%, RR = 3.9, p less than 0.001). PPA and BI were correlated with BFD (respectively r = 0.644 and r = 0.21, p less than 0.001). A multivariate analysis showed that PPA is lowered when BFD and frequency of sucking are reduced in urban high socio-economic levels (R = 56%, p less than 0.01). BI was not so lowered in urban area than expected with a lower BFD and PPA. These data suggest that post-partum infertility period lowered in urban area would be partially counterbalanced by cultural taboo inhibiting sexual intercourse during breast-feeding. Deep modification in sexual behavior accelerated by use of contraceptives should lead to be careful in their spread in family planning programmes where breast-feeding promotion is more than ever a priority.

[Protein-energy malnutrition in an urban African milieu (Togo). Etiologic factors in kwashiorkor and marasmus-kwashiorkor]. / La malnutrition proteino-energetique en milieu urbain africain (Togo). Facteurs etiologiques du kwashiorkor et du marasme-kwashiorkor.

The etiologic factors of protein-energy malnutrition (P.E.M.) have been studied in 59 children with kwashiorkor (KWK) or marasmus-kwashiorkor (MKWK) and living in an african urban area. The decline of breast feeding leads to an earlier P.E.M., mainly MKWK. This decline is linked to urbanization, mother's activities, dislocation of traditional structures and use of artificial formulas. Essentially based on cereals, the diet is responsible of the post-weaning P.E.M. Poverty, ignorance and food taboos are related to a lack in weaning food varieties. A small number of infants with KWK had a rich protein diet putting back the cause of an hypoproteic diet on the KWK onset. Infections play a determinant role in the onset of KWK and of some MKWK, after 2 years of age. Diarrhoea, measles, bronchopulmonary and parasitic diseases are the most prevalent infections. Among socio-cultural factors, conjugal disorders are predominating with child-mother break-up and father's bonding failure. At the opposite of rural areas, the family size is reduced. The three first birth ranges are specially concerned with young inexperienced mothers.

[Inclusion of hepatitis B vaccination in the Expanded Program of Immunization: feasibility study in the medical region of Kolda (Senegal)]. / Inclusion de la vaccination contre l'hépatite B dans le programme élargi de vaccination: étude de faisabilité dans la région médicale de Kolda (Sénégal).

Hepatitis B is highly endemic in Senegal. The prevalence of hepatitis B antigens in the population was estimated to be 10 to 12% in 1982. According to the WHO recommendations, a hepatitis B vaccination program (HBV) was launched in 10 medical centers in the Kolda medical region to assess the feasibility of including HBV in the EPI. The epidemiological impact of HBV was also investigated by comparison of the vaccinated zone (VZ) to a control non vaccinated zone (NVZ). HBV coverage had a pattern similar to that of DPT-IPV, but at a lower level: the overall coverage with HBV was only 37.5%, and the drop out rate for HBV1-3 was only 34.4%. In addition, the coverage of the under one year age group was insufficient: 45% for HBV3 as compared to 78% for DPT3 (p < 0.0001). Routine vaccination records in the medical centers in the VZ were consistent with the findings of cluster surveys. Hepatitis B markers were less prevalent among vaccinated that non vaccinated children (8 versus 18.5%, p < 0.001). HB antigenemia was significantly less frequent in the VZ than the NVZ (3.9 versus 10.9, p < 0.0001), and the difference was even larger for all hepatitis markers (7.4 versus 23.7%, p < 0.0001). This study therefore suggests that the inclusion of HBV in the EPI should be continued and strengthened in less accessible regions by an adapted social mobilization program. HBV could then be extended to the whole medical district of Kolda in association with regular epidemiological and serological surveillance.

[Control of hepatitis B in French Polynesia with a program of systematic vaccination of newborns with the Genhevac B vaccine]. / Lutte contre l'hépatite B en Polynésie française par un programme de vaccination systématique des nouveau-nés avec le vaccin Genhevac B.

In 1988, a 5-year vaccination program against hepatitis B was launched for all newborns in a pilot area, the Austral archipelago in French Polynesia. Genhevac B, a recombinant vaccine produced from mammalian cells was administered. Three different immunization schedules were used, none of them including additional specific immunoglobulin: i) four doses, one at each months (M) 0, 1, 2, and 12; ii) three doses one at each MO, M1 and M6; and iii) three doses one at each MO, M1 and M12. Each year during the 5 year period a serological survey was conducted. Of the 837 children who received at least one vaccine dose, 5 were HBsAg carriers. Seroprotection rates for anti-HBs and anti-PreS2 antibodies were 88% after one dose and 97% after two doses. After the third dose, seroprotection rates and geometric mean titers of anti-HBs antibodies were 95% and 217 mIU/ml for schedule (i) (three dose only); 92% and 389 mIU/ml for schedule (ii) and 93% and 344 mIU/ml for schedule (iii) respectively. After four doses (schedule i) the values were 100% and 1228 mIU/ml. Of the 18 newborns whose mothers were positive for both HBsAg and HBeAg, one was a HBsAg carrier. The estimated protective rate for prevention of perinatal transmission was 94%. This study suggests that in field conditions, systematic vaccination of newborns without using specific immunoglobulins can confer early protection. The schedule recommended for use in French Polynesia was three doses, at MO, M1 and M6-12 (between 6 and 12 months) with an additional booster dose at age 6 years, the last year of nursery school. Since April 1992, all children born in French Polynesia have been vaccinated according to this schedule. A catch-up program has been implemented for children aged 4 to 10 years old using a similar immunization schedule.

Potentials and limitations of protein vaccines in infants.

Immunization of infants represents a difficult challenge since immune responses in infants differ qualitatively from those of adults (immature immune and bias towards Th2 rather than a Th1 immune responses). While protein vaccines are immunogenic in infants earlier than polysaccharides in the very first months of life, requiring repeated administration. Protein vaccines such as diphtheria and tetanus toxoids and hepatitis B antigens are safe and immunogenic in infants, able to induce long-lasting memory, and effective. HB vaccines are the first vaccines administered at birth against a sexually transmitted disease and that prevent cancer. These success stories must however be tempered by the existence of immunologic interferences that may occur when combining vaccines in a single injection. Moreover, very little is known whether inappropriate protein conformation and glycosylation play roles in the impairment of the functional immunogenicity of protein vaccines in infants. Although much is known about how to produce and purify proteins, we know much less about how protein characteristics are related to functional immunogenicity.