Circulating antibody secreting cell response to parenteral pneumococcal vaccines as an indicator of a salivary IgA antibody response

Persistence of antibody to 23-valent pneumococcal polysaccharide vaccine: a 5-year prospective follow-up cohort study

BACKGROUND

Pneumococcal vaccines are effective in preventing pneumococcal diseases in adults. The evaluation of the antibodies persistence to the 23-valent pneumococcal polysaccharide vaccine (PPV23) could provide evidence on PPV23 revaccination.

RESEARCH DESIGN AND METHODS

Adults aged ≥ 60 years were selected and vaccinated with PPV23 in Shanghai, and followed up for 5 years with blood samples collection of a 1-year interval. The geometric mean concentrations (GMC) of the IgG against 23 pneumococcal serotypes covered by PPV23 were detected using enzyme-linked immunosorbent assay. The antibodies to 23 pneumococcal serotypes among different groups was analyzed using statistical analysis.

RESULTS

Overall, 517 participants completed all six visits over a 5-year period (2013-2018). The GMC of 23 serotypes in adults aged ≥ 60 years decreased slowly after PPV23 vaccination compared to baseline pre-vaccination (P < 0.05), except serotype 3. Additionally, the multiplicative increase in the antibody concentration after PPV23 vaccination was greater, and the antibody levels of serotypes 1 and 6B were significantly higher at visit 5 than at visit 4 (P < 0.05).

CONCLUSIONS

The pneumococcal antibodies in elderly after PPV23 vaccination could sustain high levels over long-term follow-up, which suggested that the interval of revaccination with PPV23 in elderly should be at least 5 years after the first vaccination.

Antibodies prevalence against Haemophilus influenzae type b in Jeddah population, Saudi Arabia. II. Antibodies subclasses

Our previous reported that Jeddah, Saudi Arabia population have a comparable and protective herd immunity represented by IgG, IgA and IgM against Haemophilus influenzae type b (Hib), by using indirect ELISA test was used to evaluate Haemophilus influenzae type b (Hib) anti-polyribosyl-ribitol phosphate (PRP) total antibodies (IgM, IgG, IgA) in 1,003 sera samples. Current report was evaluated the IgG and IgA subclasses responsible about this protection using same methodology. IgG, IgA, and their subclasses are responsible about this circulating protection. Our study will consider the first report evaluate the levels of IgA subclasses and its relation to ages, as well as the relations between anti-Hib antibody subclass and age. The current results demonstrated that the highest levels concentrated in IgG1 and IgG2, while IgG3 and IgG4 showed the lowest levels. So, their concentrations were arranged in IgG1 > IgG2 > IgG3 > IgG4. The results indicated that the age and gender have no effect on both IgG or IgA subclasses in healthy immunized individuals enrolled. While, IgA1 concentrations were significantly higher than IgA2 in all age categories regardless of gender. It seem that the IgG1, IgG2 and IgA1 subclasses were the main constituent of Jeddah herd immunity against Hib. Finally, to the best of our knowledge, there were no previous reports that focusing on the levels of IgA subclasses and its relation to ages, so our study considers the first worldwide.

Hib Vaccines: Past, Present, and Future Perspectives

Haemophilus influenzae type b (Hib) causes many severe diseases, including epiglottitis, pneumonia, sepsis, and meningitis. In developed countries, the annual incidence of meningitis caused by bacteria is approximately 5–10 cases per population of 100,000. The Hib conjugate vaccine is considered protective and safe. Adjuvants, molecules that can enhance and/or regulate the fundamental immunogenicity of an antigen, comprise a wide range of diverse compounds. While earlier developments of adjuvants created effective products, there is still a need to create new generations, rationally designed based on recent discoveries in immunology, mainly in innate immunity. Many factors may play a role in the immunogenicity of Hib conjugate vaccines, such as the polysaccharides and proteins carrier used in vaccine construction, as well as the method of conjugation. A Hib conjugate vaccine has been constructed via chemical synthesis of a Hib saccharide antigen. Two models of carbohydrate-protein conjugate have been established, the single ended model (terminal amination-single method) and cross-linked lattice matrix (dual amination method). Increased knowledge in the fields of immunology, molecular biology, glycobiology, glycoimmunology, and the biology of infectious microorganisms has led to a dramatic increase in vaccine efficacy.

Sublingual immunization with the phosphate-binding-protein (PstS) reduces oral colonization by Streptococcus mutans

Bacterial ATP-binding cassette (ABC) transporters play a crucial role in the physiology and pathogenicity of different bacterial species. Components of ABC transporters have also been tested as target antigens for the development of vaccines against different bacterial species, such as those belonging to the Streptococcus genus. Streptococcus mutans is the etiological agent of dental caries, and previous studies have demonstrated that deletion of the gene encoding PstS, the substrate-binding component of the phosphate uptake system (Pst), reduced the adherence of the bacteria to abiotic surfaces. In the current study, we generated a recombinant form of the S. mutans PstS protein (rPstS) with preserved structural features, and we evaluated the induction of antibody responses in mice after sublingual mucosal immunization with a formulation containing the recombinant protein and an adjuvant derived from the heat-labile toxin from enterotoxigenic Escherichia coli strains. Mice immunized with rPstS exhibited systemic and secreted antibody responses, measured by the number of immunoglobulin A-secreting cells in draining lymph nodes. Serum antibodies raised in mice immunized with rPstS interfered with the adhesion of bacteria to the oral cavity of naive mice challenged with S. mutans. Similarly, mice actively immunized with rPstS were partially protected from oral colonization after challenge with the S. mutans NG8 strain. Therefore, our results indicate that S. mutans PstS is a potential target antigen capable of inducing specific and protective antibody responses after sublingual administration. Overall, these observations raise interesting perspectives for the development of vaccines to prevent dental caries.

Different Dynamics for IgG and IgA Memory B Cells in Adolescents following a Meningococcal Serogroup C Tetanus Toxoid Conjugate Booster Vaccination Nine Years after Priming: A Role for Priming Age?

Background

Antibody levels wane rapidly after Meningococcal serogroup C conjugate (MenCC) vaccination in young children, rendering the need for an adolescent booster dose. It is not clear whether circulating memory B cells are associated with persistence of MenC-specific antibody levels.

Methods

Measurement of MenC-specific IgG and IgA memory B cells and levels of serum and salivary MenC-specific IgG and IgA in healthy 10-, 12- and 15-year-olds prior to and one month and one year after a MenCC booster vaccination. All participants had received a primary MenCC vaccination nine years earlier.

Results

The number of circulating MenC-specific IgG memory B cells prior to booster was low and not predictive for MenC-specific IgG responses in serum or saliva post-booster, whereas the number of MenC-specific IgA memory B cells pre-booster positively correlated with MenC-specific IgA levels in saliva post-booster (R = 0.5, P<0.05). The booster induced a clear increase in the number of MenC-specific IgG and IgA memory B cells. The number of MenC-PS-specific IgG memory B cells at 1 month post-booster was highest in the 12-year-olds. The number of MenC-specific memory B cells at one month post-booster showed no correlation with the rate of MenC-specific antibody decay throughout the first year post-booster.

Conclusions

Circulating MenC-specific IgA memory B cells correlate with IgA responses in saliva, whereas circulating MenC-specific IgG memory B cells are not predictive for MenC-specific IgG responses in serum or saliva. Our results are suggestive for age-dependent differences in pre-existing memory against MenC.

Immune profile of asplenic patients following single or double vaccine administration: A longitudinal cross-sectional study

OBJECTIVE

Splenectomy poses a lifelong threat for the development of uncontrolled sepsis despite vaccination. As it is impractical to measure the levels of each antibody against 23 most frequent bacterial serotypes, different surrogate markers of immune response should be identified.

MATERIAL AND METHODS

Forty-eight patients with benign disorders were vaccinated with Pneumo-23 and Act-HIB before or at the day of surgery. The immunological response and opsonization capacity of the patients after splenectomy was analyzed through the quantitative measurement of IgG, IgM, C3, and C4 titers; flow-cytometric analysis of (CD3+) T-lymphocytes and (CD19+) B-lymphocytes; and isolation of CD27+ B cells by immunomagnetic positive selection. Blood samples were drawn at the sixth month and 5 and 7 years after surgery.

RESULTS

The mean follow-up period was 98.4 months. All the patients in this series had normal IgG, C3, C4 levels and a normal distribution of CD19+ B-cells and CD8+ T-cells in three follow-up periods. Moreover, C3 levels markedly improved to 133.5±37.3 mg/dL at 5 years and remained stable thereafter. CD19+ B-lymphocyte values have progressively improved to the normal range in 98% patients at 7 years. Further, low levels of CD27+ B-cell population (memory cells) was observed in only 12.5% patients at the last follow-up. Adequate seroconversion of IgG, IgM with normal C3, C4, and CD19+ B-cell levels were accomplished in almost all patients. Early postoperative death and late overwhelming infections did not occur.

CONCLUSION

Our results are indicative of the resumption of the immune function following Pneumo-23 and Act-HIB administrations, instigated by the probable activation of B cells and adequate production of C3, C4, IgG, and IgM antibodies in remote lymphoid tissues.

Protein carriers of conjugate vaccines: characteristics, development, and clinical trials

The immunogenicity of polysaccharides as human vaccines was enhanced by coupling to protein carriers. Conjugation transformed the T cell-independent polysaccharide vaccines of the past to T cell-dependent antigenic vaccines that were much more immunogenic and launched a renaissance in vaccinology. This review discusses the conjugate vaccines for prevention of infections caused by Hemophilus influenzae type b, Streptococcus pneumoniae, and Neisseria meningitidis. Specifically, the characteristics of the proteins used in the construction of the vaccines including CRM, tetanus toxoid, diphtheria toxoid, Neisseria meningitidis outer membrane complex, and Hemophilus influenzae protein D are discussed. The studies that established differences among and key features of conjugate vaccines including immunologic memory induction, reduction of nasopharyngeal colonization and herd immunity, and antibody avidity and avidity maturation are presented. Studies of dose, schedule, response to boosters, of single protein carriers with single and multiple polysaccharides, of multiple protein carriers with multiple polysaccharides and conjugate vaccines administered concurrently with other vaccines are discussed along with undesirable consequences of conjugate vaccines. The clear benefits of conjugate vaccines in improving the protective responses of the immature immune systems of young infants and the senescent immune systems of the elderly have been made clear and opened the way to development of additional vaccines using this technology for future vaccine products.

Fully human monoclonal antibodies from antibody secreting cells after vaccination with Pneumovax®23 are serotype specific and facilitate opsonophagocytosis

B lymphocyte memory generates antibody-secreting cells (ASCs) that represent a source of protective antibodies that may be exploited for therapeutics. Here we vaccinated four donors with Pneumovax®23 and produced human monoclonal antibodies (hmAbs) from ASCs. We have cloned 137 hmAbs and the specificities of these antibodies encompass 19 of the 23 serotypes in the vaccine, as well as cell wall polysaccharide (CWPS). Although the majority of the antibodies are serotype specific, 12% cross-react with two serotypes. The Pneumovax®23 ASC antibody sequences are highly mutated and clonal, indicating an anamnestic response, even though this was a primary vaccination. Hmabs from 64% of the clonal families facilitate opsonophagocytosis. Although 9% of the total antibodies bind to CWPS impurity in the vaccine, none of these clonal families showed opsonophagocytic activity. Overall, these studies have allowed us to address unanswered questions in the field of human immune responses to polysaccharide vaccines, including the cross-reactivity of individual antibodies between serotypes and the percentage of antibodies that are protective after vaccination with Pneumovax®23.

Exploiting mucosal surfaces for the development of mucosal vaccines

Mucosal immunity covers a variety of mucosal surfaces susceptible to different pathogens. This review highlights the diversity of mucosal tissues and the unique microenvironments in which an immune response is generated. It argues that tissue-specific factors present throughout mucosal tissues and lymph nodes determine the differentiation into IgA-producing B cells, which in turn determines their migration patterns. Mucosal immunity can therefore be induced when antigen is delivered at any mucosal tissue without the need for specific 'mucosal adjuvants' or targeting to specialised lymphoid structures. Non-oral vaccination strategies directed at alternative and more accessible mucosal tissue sites, may provide new avenues for both mucosal and systemic immunization, and will be greatly facilitated by the use of large animal models.

Appearance of peripheral blood plasma cells and memory B cells in a primary and secondary immune response in humans

In humans, the kinetics of the appearance of memory B cells and plasma cells during primary immunization are not well defined. In this study, we assessed the primary B-cell response of rabies-antigen naive volunteers during a 3-dose course of rabies vaccine compared with the B-cell response to a booster dose of rabies vaccine given to previously immunized volunteers. After a single dose of vaccine, in the naive group plasma and memory B cells appeared later (peak at day 10) than in the primed group (peak at day 7) and were at lower frequency. The most rapid responses (day 4) were detected after a third immunization in the naive group. This is the first study to document the detailed kinetics of the plasma cell and memory B-cell responses to immunization in adult humans and to demonstrate differences in the responses that relate to the preexisting immune status of the persons.

Immunogenicity of varying dosages of 7-valent pneumococcal polysaccharide-protein conjugate vaccine in seniors previously vaccinated with 23-valent pneumococcal polysaccharide vaccine

In this dose-ranging study 220 seniors who had received the 23-valent pneumococcal polysaccharide (PnPS) vaccine at least 5 years prior to enrollment were assigned to receive one of four volumes (0.1, 0.5, 1 or 2 ml) of 7-valent pneumococcal conjugate (PnC) vaccine or a 0.5 ml dose of 23-valent PnPS vaccine. All participants received a reduced challenge dose of 0.1 ml of PnPS vaccine 1 year after enrollment. There was evidence of a dose response to PnC vaccine and antibody levels in the 1 ml PnC group tended to be significantly higher than in the PnPS group. A booster response to the challenge vaccination was not observed. Administration of a 1 ml dose of PnC vaccine is more immunogenic than 0.5 ml of PnPS vaccine in elderly adults previously vaccinated with PnPS vaccine.

The kinetics and phenotype of the human B-cell response following immunization with a heptavalent pneumococcal-CRM conjugate vaccine

Primary immunization of infants with protein-polysaccharide conjugate vaccines induces antipolysaccharide antibody and is highly effective in preventing invasive disease caused by encapsulated bacteria. However, recent experience from the UK indicates that this immunity is not sustained in the absence of booster doses of vaccine. This study aimed to establish the kinetics and phenotype of B-cell subpopulations responding to booster immunization with a heptavalent pneumococcal conjugate vaccine (Pnc7), which is to be introduced into the primary immunization schedule in the UK during 2006. Six adult volunteers received a booster dose of Pnc7 12-18 months after primary immunization. CD27hi CD38hi CD20(+/-) IgG antibody-forming cells were detected in peripheral blood with maximum frequency at days 6-7 after immunization. This was accompanied by a more prolonged rise in memory B cells that required in vitro stimulation with Staphylococcus aureus Cowan strain and interleukin-2 to induce antibody secretion. These data provide evidence for at least two subsets of antibody-forming cells involved in the secondary humoral response to a glycoconjugate vaccine in primed individuals. A briefly circulating subset of B cells that spontaneously secrete immunoglobulin G may be responsible for early defence against re-encountered encapsulated bacteria. However, the kinetics of the appearance of these cells may indicate that the humoral immune response is too slow in defence against an organism that invades within days of acquisition. The more sustained presence of a memory population may provide persistence of antipolysaccharide antibody after a booster dose of vaccine and may also include re-circulatory populations responsible for further anamnestic responses.

Salivary antibodies induced by the seven-valent PncOMPC conjugate vaccine in the Finnish Otitis Media Vaccine Trial

Background

Mucosal antibodies have been suggested to have a role in defence against pneumococcal infections. We investigated here the ability of a seven-valent pneumococcal conjugate vaccine, PncOMPC, to induce mucosal immune response.

Methods

Healthy Finnish children (n = 111), a subcohort of the Finnish Otitis Media Vaccine Trial, were recruited and 56 of them were immunised with the PncOMPC at the age of 2, 4, and 6 months. At 12 months of age, 49 of them received the PncOMPC and 7 were vaccinated with the pneumococcal polysaccharide vaccine (PncPS) as a booster. The control group of 55 children received a hepatitis B vaccine at the same ages. Salivary anti-Pnc IgG, IgA, IgA1, and IgA2 antibodies to serotypes 6B, 14, 19F, and 23F were measured in both groups at the age of 7 and 13 months.

Results

Salivary anti-Pnc IgG and IgA were detected more often in the PncOMPC than in the control group. However, the difference between groups was significant only for 19F and 23F IgA concentrations at the age of 7 months. At the age of 13 months, antibody concentrations did not differ between PncOMPC and control groups. The rises in IgA concentrations between 7 and 13 months of age were mainly of subclass IgA1. Further, there is a clear trend that PncPS booster induces higher salivary anti-Pnc PS antibody concentrations than the PncOMPC.

Conclusion

We found that PncOMPC can induce a mucosal IgA response. However, the actual impact of mucosal antibodies in protection against pneumococcal infections is not clear.

Salivary antibodies induced by the seven-valent PncCRM conjugate vaccine in the Finnish Otitis Media Vaccine Trial

We studied salivary antibodies induced by a seven-valent pneumococcal conjugate vaccine (PncCRM). Healthy Finnish children (n=115), a subcohort of the Finnish Otitis Media (FinOM) Vaccine Trial, were immunised either with the PncCRM or a control vaccine (hepatitis B) at the age of 2, 4, 6, and 12 months. Salivary IgG, IgA, IgA1, IgA2 and sIg for serotypes 6B, 14, 19F, and 23F were measured at 7 and 13 months of age, and IgG and IgA also at 4-5 years of age. The PncCRM could induce both salivary anti-Pnc polysaccharide IgG and IgA. However, by the age of 4-5 years IgA concentrations had increased in both groups and were similar. The increases in IgA concentrations were mostly of IgA1 subclass. The difference between the PncCRM and the control group was more notable for serotypes 6B, 14 and 23F than for serotype 19F. We could not find evidence for the development of mucosal immunologic memory after vaccination with the PncCRM.

Bacterial polysaccharide-protein conjugate vaccines

Following demonstration that chemical conjugation of polysaccharide antigens to proteins could enhance their immunogenicity in the 1920s, interest in this approach to primary prevention of bacterial infections waned with the development and widespread use of antibiotics. Emergence of resistant bacteria rekindled interest in the late 20th century, which saw extremely rapid development and implementation of several vaccines which are already rapidly changing the epidemiology of childhood infections with Haemophilus influenzae type b, Streptococcus pneumoniae and Neisseria meningitidis. Others such as Group B streptococcus and Salmonella typhi infections may soon follow. However, several important questions about the immunology of these antigens remain unanswered and the long-term implications of reducing or eliminating the circulation of organisms which are more commonly nasopharyngeal commensals than pathogenic invaders are uncertain.

Optimization of an ovine antibody-secreting cell assay for detection of antigen-specific immunoglobulin production in peripheral blood leukocytes

Enumeration of antibody-secreting cells in peripheral blood by enzyme-linked immunospot (ELISPOT) has been used in human studies to detect antigen-specific antibody production at mucosal tissue sites. An alternative assay for detecting and quantitating antigen-specific antibody responses involves culturing circulating peripheral blood antibody-secreting cells and quantitating specific antibody production in culture supernatant by ELISA. In the present study, antigen-specific peripheral blood lymphocytes were isolated from subcutaneously immunized sheep and the parameters for maximizing in vitro antibody production by in vivo-induced antibody-secreting cells optimized for this species. Maximum antibody-secreting cell responses were observed in peripheral blood collected four days after antigen challenge. The addition of lipopolysaccharide and antisheep immunoglobulin had no effect on in vitro antibody secretion by blood antibody-secreting cells, while the effects of pokeweed mitogen were highly variable. However, the combination of anti-Ig and recombinant ovine interleukin-6 to peripheral blood lymphocyte cultures was found to markedly and consistently enhance specific antibody production. In unstimulated cultures, the optimal peripheral blood lymphocyte concentration for generating the greatest antibody responses was 5.0 x 107 cells per mL, but in cultures stimulated with recombinant ovine interleukin-6/antisheep immunoglobulin, the optimal cell concentration was lowered to approximately 1.0 x 107 cells per mL. In vitro, peak immunoglobulin production was usually achieved by day one in unstimulated cultures. In recombinant ovine interleukin-6/antisheep immunoglobulin-stimulated cultures, antibody levels were similar to unstimulated cultures by day one, however, the levels continued to rise during incubation to reach a maximum between days four and five of incubation. This optimized antibody-secreting cell culture assay is amenable for increasing the sensitivity and reducing the cell numbers required for quantitating antigen-specific antibody induction in large-scale immunization trials in sheep and other large animal species.

The new pneumococcal vaccine

Pneumococcal disease is now the leading cause of vaccine-preventable bacterial disease in children worldwide. Although a pneumococcal polysaccharide vaccine has been available for over three decades, its use has been limited due to poor immunogenicity in the most vulnerable children, aged less than 2 years. The prevalence of pneumococcal disease worldwide and the alarming global escalation of multiresistant strains of Streptococcus pneumoniae (pneumococcus) during the past decade have provided the impetus for the development and application of a new pneumococcal vaccine. The outstanding success of Haemophilus influenzae type b (Hib) conjugate vaccine in the control of invasive Hib disease is a reason to be optimistic that the pneumococcal conjugate vaccines will achieve similar results for the control of invasive pneumococcal disease. Remarkable efficacy against invasive pneumococcal disease with a seven-valent pneumococcal conjugate vaccine was demonstrated in infants and toddlers in the USA, and in February 2000 the first pneumococcal conjugate vaccine was licensed. Licensure and widespread use is likely to follow in other countries in which there is a need and the means to afford this live-saving vaccine. Active disease surveillance must be sustained globally, while active research, development of other multivalent conjugate formulations and the search for new candidate protein-based vaccines are in progress.

Current state of pneumococcal vaccines

Streptococcus pneumoniae is a leading cause of bacterial pneumonia, meningitis, and acute otitis media in children and adults worldwide. According to World Health Organization estimates, at least 1 million children under 5 years of age die each year from pneumococcal pneumonia. The emergence of resistant strains necessitates the development of an effective vaccine with a large serotype coverage. The 11 most common serotypes cause 72-83% of all serious pneumococcal diseases worldwide. Currently marketed 23-valent pneumococcal polysaccharide vaccine provides large serotype coverage and offers a less expensive option. However, it is efficacious only in adults but not in infants. Conjugate vaccines offer a solution by generating immunological memory already at early age. A recently licensed 7-valent conjugate vaccine is immunogenic and efficacious in infants. Its serotype coverage might be sufficient in Europe and North America, but not in Africa, Asia and Oceania. A need exists to develop pneumococcal vaccines with lower cost and larger serotype coverage. Several 11-valent pneumococcal conjugate vaccines are being evaluated in phase I-III trials. This study reviews the current state of pneumococcal problem and pneumococcal vaccines in clinical use.

Future vaccines: recent advances and future prospects

The 20th century has witnessed the introduction of over 20 vaccines that prevent or even conquer diseases such as smallpox, polio, and measles. The continued threat of infectious diseases demands the creation of many more vaccines, especially against common respiratory and gastrointestinal pathogens. Thanks to recent advances in molecular biology, immunology, and adjuvant technology, the next decade likely will bring a vaccine for HIV/AIDS also. We enter the 21st century with a tempered optimism, proud of past achievements, but mindful of the challenges that lie ahead.

Serum and salivary anti-capsular antibodies in infants and children vaccinated with octavalent pneumococcal conjugate vaccines, PncD and PncT

We studied the immunogenicity of two octavalent pneumococcal (Pnc) conjugate vaccines; Pnc polysaccharides (PS) of serotypes 3, 4, 6B, 9V, 14, 18C, 19F, and 23F were conjugated to diphtheria or tetanus toxoid (PncD and PncT, respectively). Fifty healthy Finnish infants were vaccinated at the ages of 2, 4, 6, and 15 months with either PncD or PncT. Serum IgG antibodies to the vaccine serotypes were analysed by enzyme-linked immunosorbent assay (EIA). All eight PSs induced a significant antibody response both after the primary series and after the booster. Response to PncD was higher for PSs 3, 9V, 14 and 18C and to PncT for serotype 4. Salivary IgA and IgG anti-Pnc antibodies were measured for serotypes 4, 6B, 9V, 14, 18C, and 19F. Mucosal antibodies were found rarely after the primary series but in a greater proportion after the booster. In conclusion, both vaccines were immunogenic.

Tolerability and immunogenicity of an 11-valent pneumococcal conjugate vaccine in adults

We studied the safety and immunogenicity in healthy adults of an 11-valent pneumococcal conjugate vaccine. Capsular polysaccharides (PS) of serotypes 1, 4, 5, 7F, 9V, 19F and 23F were conjugated to tetanus toxoid, and of serotypes 3, 6B, 14 and 18C to diphtheria toxoid. Ten subjects received the conjugate vaccine with and the other ten subjects without aluminium hydroxide adjuvant. The reference vaccine was a marketed 23-valent PS vaccine. Safety data were recorded over 5 days after the immunisation. IgG antibody concentrations, avidity and subclass distribution were measured by EIA. The conjugate without aluminium induced more local adverse effects than the conjugate with aluminium or PS vaccine. All vaccines evoked significant antibody increases to all vaccine specific antigens. Both conjugate vaccines induced antibodies mainly of IgG(2) subclass, and adjuvanted conjugate vaccine induced IgG antibodies with increased avidity. This first administration, to man, of a mixed protein carrier 11-valent pneumococcal conjugate vaccine demonstrated its ability to induce an immune response without significant adverse effects, enabling further study on its use in paediatric populations.

Serum and salivary anti-capsular antibodies in infants and children immunized with the heptavalent pneumococcal conjugate vaccine

AIM

To study the ability of seven-valent experimental pneumococcal polysaccharide CRM197 protein conjugate vaccine (PncCRM) to induce antibodies in serum and saliva of infants.

METHODS

Sixty Finnish infants received Pnc-CRM vaccine at 2, 4 and 6 months of age and were boosted with PncCRM (n = 30) or pneumococcal polysaccharide (PncPS) (n = 29) vaccine at the age of 15 months. Serum IgG antibody concentrations to vaccine serotypes 4, 6B, 9V, 14, 18C, 19F and 23F were measured by enzyme immunoassay at 2, 4, 6, 7, 15, 16 and 24 months of age. Salivary IgA, IgG and secretory Ig antibody titers at 7 and 16 months of ages were analyzed by enzyme immunoassay against the same serotypes, except 23F.

RESULTS

PncCRM induced systemic immune responses and immunologic memory. At 7 months of age 69 to 100% of children, depending on the serotype, had serum IgG antibody concentrations exceeding the value of 1.0 microg/ml. At 15 months the titers were still higher than before the vaccinations. Booster doses of either PncPS or PncCRM induced an increase in antibody concentrations. The titers were still elevated at 24 months of age. Salivary IgA and IgG antibodies were found rarely at 7 months of age, but in up to 80% of samples taken at 16 months of age, depending on the serotype and nature of the booster vaccine. Salivary IgG correlated with IgG in serum, supporting the theory that salivary IgG is derived from serum. Salivary IgA and secretory Ig correlated positively, which indicates that IgA was locally produced.

CONCLUSIONS

PncCRM induces both systemic and mucosal immune responses in infants.

Pneumococcal conjugate vaccination in toddlers: mucosal antibody response measured as circulating antibody-secreting cells and as salivary antibodies

BACKGROUND

Our previous studies have shown an antibody-secreting cell (ASC) response to pneumococcal vaccines in adults and suggested that a high IgA ASC response is an indicator of a secretory IgA response in saliva. We believe that the mucosal immune response is potentially an important characteristic of the pneumococcal vaccines and should thus be measured when the new pneumococcal conjugate vaccines are evaluated.

OBJECTIVES

To study mucosal and serum antibody responses to pneumococcal conjugate vaccines in toddlers.

METHODS

Each investigational vaccine, containing either 3 or 10 microg of pneumococcal PS serotypes 6B, 14, 19F and 23F conjugated to either diphtheria toxoid (PncD) or tetanus protein (PncT), was administered to 10 children (a total of 40 children). The ASC response was measured on Day 7 after immunization by enzyme-linked immunospot assay, and the salivary and serum antibodies were measured before and 7 and 28 days after the immunization by enzyme immunoassay.

RESULTS

The vaccines studied induced ASC responses to the pneumococcal polysaccharides (PS) in all children vaccinated. The ASC responses to the PS components of the vaccine (the geometric mean number of ASCs varying from 120 to 160 ASC/10(6) cells) were lower than those seen earlier in adults after conjugate vaccine (240 to 2015 ASC/10(6) cells), but comparable with those seen earlier in adults after pneumococcal PS vaccine (113 to 136 ASC/10(6) cells). The ASC response was clearly dominated by IgA-secreting cells. Salivary IgA responses were detected in 35% of the children, but IgG was rarely detected in saliva. A positive correlation was demonstrated between the number of IgA ASCs and salivary IgA concentration (r = 0.70, P = 0.01), suggesting that a high number of IgA ASCs after parenteral immunization is an indicator of a secretory IgA response in saliva. On Day 28 after immunization increased serum concentrations of IgG were detected in most vaccinees (75 to 95%, depending on the serotype).

CONCLUSIONS

Both mucosal and systemic antibody responses were induced by PncD and PncT vaccines in toddlers.

B and T cell immunity in patients with lysinuric protein intolerance

Lysinuric protein intolerance (LPI) is characterized by defective cellular transport of the dibasic amino acids, secondary dysfunction of the urea cycle, aversion to dietary protein, failure to thrive, hepatosplenomegaly and osteoporosis. Because several patients have suffered from recurrent respiratory infections and/or severe generalized varicella, and a few have developed systemic lupus, vasculitis or other autoimmune diseases, we have now evaluated the function of patients' immune systems. Serum concentrations of one to three IgG subclasses were decreased in 10 of the 12 patients studied. Antibody titres against diphtheria, tetanus and Haemophilus influenzae (Hib) were below the detection limit of the assay in four, three and eight of the 11 patients examined, respectively. (Re)vaccination of these 11 patients led to satisfactory responses against tetanus, but two patients still failed to develop measurable antibodies against diphtheria, two against Hib and six against one or more of the three serotypes of 23-valent pneumococcus vaccine. The proportions of T cells of all lymphocytes and the proliferative responses of the peripheral blood mononuclear cells were normal. In conclusion, humoral immune responses in some patients with LPI are defective and these patients may benefit from intravenous immunoglobulin therapy.

Pneumococcal conjugate vaccination in adults: circulating antibody secreting cell response and humoral antibody responses in saliva and in serum

The results from our previous study showed IgA dominated ASC responses to pneumococcal polysaccharide vaccine and to pneumococcal polysaccharide meningococcal outer membrane protein conjugate vaccine (PncOMPC) in adult volunteers. The results indicated that a high IgA ASC response is a useful indicator of a secretory IgA response in saliva. We believe that the mucosal immune responses is potentially an important characteristic of the pneumococcal vaccines and should thus be measured when the new pneumococcal conjugate vaccines are evaluated. In the present study, we studied two new tetravalent pneumococcal conjugate vaccines: the diphtheria toxoid and tetanus toxoid conjugates. In contrast to PncOMPC, these conjugates induced higher responses than the polysaccharide vaccine. Furthermore, the different structure of the two conjugate vaccines might affect the nature of the response. Thus a different vaccine may be optimal for induction of a mucosal response than is of systemic responses.