Development of antibodies to PspA families 1 and 2 in children after exposure to Streptococcus pneumoniae

Streptococcus pneumoniae serotype 3 population structure in the era of conjugate vaccines, 2001-2018

Background. Despite use of highly effective conjugate vaccines, invasive pneumococcal disease (IPD) remains a leading cause of morbidity and mortality and disproportionately affects Indigenous populations. Although included in the 13-valent pneumococcal conjugate vaccine (PCV13), which was introduced in 2010, serotype 3 continues to cause disease among Indigenous communities in the Southwest USA. In the Navajo Nation, serotype 3 IPD incidence increased among adults (3.8/100 000 in 2001-2009 and 6.2/100 000 in 2011-2019); in children the disease persisted although the rates dropped from 5.8/100 000 to 2.3/100 000.Methods. We analysed the genomic epidemiology of serotype 3 isolates collected from 129 adults and 63 children with pneumococcal carriage (n=61) or IPD (n=131) from 2001 to 2018 of the Navajo Nation. Using whole-genome sequencing data, we determined clade membership and assessed changes in serotype 3 population structure over time.Results. The serotype 3 population structure was characterized by three dominant subpopulations: clade II (n=90, 46.9 %) and clade Iα (n=59, 30.7 %), which fall into Clonal Complex (CC) 180, and a non-CC180 clade (n=43, 22.4 %). The proportion of clade II-associated IPD cases increased significantly from 2001 to 2010 to 2011-2018 among adults (23.1-71.8 %; P<0.001) but not in children (27.3-33.3 %; P=0.84). Over the same period, the proportion of clade II-associated carriage increased; this was statistically significant among children (23.3-52.6 %; P=0.04) but not adults (0-50.0 %, P=0.08).Conclusions. In this setting with persistent serotype 3 IPD and carriage, clade II has increased since 2010. Genomic changes may be contributing to the observed trends in serotype 3 carriage and disease over time.

Synthesis and delivery of Streptococcus pneumoniae capsular polysaccharides by recombinant attenuated Salmonella vaccines

Pneumococcal infection-caused diseases are responsible for substantial morbidity and mortality worldwide. Traditional pneumococcal vaccines are developed based on purified capsular polysaccharides (CPS) or CPS conjugated to a protein carrier. Production processes of the traditional vaccines are laborious, and thereby increase the vaccine cost and limit their use in developing nations. A cost-effective pneumococcal vaccine using the recombinant attenuated Salmonella vaccine (RASV) was developed in this study. We cloned and expressed genes for seven serotypes of CPSs in the RASV strain. The RASV-delivered CPSs induced robust humoral and cell-mediated responses and mediated efficient protection of mice against pneumococcal infection. Our work provides an innovative strategy for mass producing low-cost bioconjugated polysaccharide vaccines for needle-free mucosal delivery against pneumococcal infections.

Streptococcus pneumoniae capsular polysaccharides (CPSs) are major determinants of bacterial pathogenicity. CPSs of different serotypes form the main components of the pneumococcal vaccines Pneumovax, Prevnar7, and Prevnar13, which substantially reduced the S. pneumoniae disease burden in developed countries. However, the laborious production processes of traditional polysaccharide-based vaccines have raised the cost of the vaccines and limited their impact in developing countries. The aim of this study is to develop a kind of low-cost live vaccine based on using the recombinant attenuated Salmonella vaccine (RASV) system to protect against pneumococcal infections. We cloned genes for seven different serotypes of CPSs to be expressed by the RASV strain. Oral immunization of mice with the RASV-CPS strains elicited robust Th1 biased adaptive immune responses. All the CPS-specific antisera mediated opsonophagocytic killing of the corresponding serotype of S. pneumoniae in vitro. The RASV-CPS2 and RASV-CPS3 strains provided efficient protection of mice against challenge infections with either S. pneumoniae strain D39 or WU2. Synthesis and delivery of S. pneumoniae CPSs using the RASV strains provide an innovative strategy for low-cost pneumococcal vaccine development, production, and use.

Serum levels of anti-PspA and anti-PspC IgG decrease with age and do not correlate with susceptibility to experimental human pneumococcal colonization

Older adults are at increased risk of pneumococcal disease. This work aims to evaluate whether there is any decrease in serum IgG against variants of the antigens Pneumococcal surface protein A (PspA) and Pneumococcal surface protein C (PspC) in healthy adults with increasing age. Levels of IgG against PspA and PspC variants were determined by ELISA in serum samples comparing volunteers 18–30 years of age with volunteers who were 50–70+ before and after an experimental pneumococcal colonization challenge. The serotype 6B strain used in the challenge belongs to a minor group of pneumococcal isolates expressing two PspC variants. There was a decrease in levels of IgG with increasing age for the most common PspA variants and for all PspC variants analyzed. No correlation was found between basal levels of IgG against these antigens and protection against colonization. There was an increase in levels of IgG against PspA variants that are more cross-reactive with the variant expressed by the challenge strain post challenge in younger individuals who became colonized. Since the challenge strain used in our study expresses two different PspC variants, an increase in serum IgG against all PspC variants tested was observed in younger individuals who became colonized. For some of the antigen variants tested, a decrease in serum IgG was observed in young volunteers who were challenged but did not become colonized. Serum IgG antibodies against PspA and PspC variants thus decrease with age in healthy adults, but there is no correlation between levels of IgG against these antigens and protection against human experimental colonization. Though no correlation between naturally induced serum IgG antibodies against PspA and PspC and protection against colonization was observed, these results do not rule out the protective potential of these antigens as vaccines against pneumococcal infections.

Virulence-Associated Characteristics of Serotype 14 and Serogroup 9 Streptococcus pneumoniae Clones Circulating in Brazil: Association of Penicillin Non-susceptibility With Transparent Colony Phenotype Variants

Streptococcus pneumoniae remains a major agent of invasive diseases, especially in children and the elderly. The presence of pneumococcal capsule, pneumococcal surface protein A (PspA), and pilus type 1 (PI-1) and the ability of colony phase variation are assumed to play important roles in the virulence potential of this microorganism. Differences in the capsular polysaccharide allow the characterization of more than 90 pneumococcal serotypes; among them, serotype 14 and serogroup 9 stand out due to their prevalence in the pre- pneumococcal conjugate vaccine era and frequent association with penicillin non-susceptibility. Here we investigated the distribution of PI-1 and pspA genes and colony phase variants among 315 S. pneumoniae isolates belonging to serotype 14 and serogroup 9, recovered over 20 years in Brazil, and correlated these characteristics with penicillin susceptibility and genotype as determined by multilocus sequence typing. All strains were shown to carry pspA genes, with those of family 2 (pspA2) being the most common, and nearly half of the strains harbored P1-1 genes. The pspA gene family and the presence of PI-1 genes were conserved features among strains belonging to a given clone. A trend for increasing the occurrence of pspA2 and PI-1 genes over the period of investigation was observed, and it coincided with the dissemination of CC156 (Spain^9V-3) clone in Brazil, suggesting a role for these virulence attributes in the establishment and the persistence of this successful clone. Opaque variant was the colony phenotype most frequently observed, regardless of clonal type. On the other hand, the transparent variant was more commonly associated with penicillin-non-susceptible pneumococci and with strains presenting evidence of recombination events involving the genes coding for polysaccharide capsule and PspA, suggesting that pneumococcal transparent variants may present a higher ability to acquire exogenous DNA. The results bring to light new information about the virulence potentials of serotype 14 and serogroup 9 S. pneumoniae isolates representing the major clones that have been associated with the emergence and the dissemination of antimicrobial resistance in our setting since the late 1980s.

A preliminary study on the application of PspA as a carrier for group A meningococcal polysaccharide

This study aimed to explore the feasibility of pneumococcal surface protein A (PspA) as a carrier protein. Three recombinant pneumococcal surface proteins from three different clades were expressed by the prokaryotic expression system and conjugated to group A meningococcal polysaccharide (GAMP) to generate three polysaccharide-protein conjugates. The conjugates, unconjugated proteins, GAMP, and GAMP-TT vaccine bulk (used as positive control) were immunized into mice, and their immune effects were assessed by the methods of enzyme-linked immunosorbent assay (ELISA), flow cytometry (FCM), and serum bactericidal assay (SBA). The results showed that the polysaccharide-protein conjugates could produce higher levels of anti-GAMP IgG titers (P < 0.05), higher ratios of Th1/Th2 (P < 0.05), and higher levels of serum bactericidal activity (P < 0.05), compared with the unconjugated GAMP. The conjugation of PspAs to GAMP also enhanced the anti-PspA responses compared with unconjugated PspAs except for PspA3. In conclusion, the results indicated that the three PspAs were appropriate carrier proteins, as demonstrated by the characteristics of T-cell dependent responses to the GAMP, and might protect against group A of epidemic cerebrospinal meningitis.

Room Temperature Stable PspA-Based Nanovaccine Induces Protective Immunity

Streptococcus pneumoniae is a major causative agent of pneumonia, a debilitating disease particularly in young and elderly populations, and is the leading worldwide cause of death in children under the age of five. While there are existing vaccines against S. pneumoniae, none are protective across all serotypes. Pneumococcal surface protein A (PspA), a key virulence factor of S. pneumoniae, is an antigen that may be incorporated into future vaccines to address the immunological challenges presented by the diversity of capsular antigens. PspA has been shown to be immunogenic and capable of initiating a humoral immune response that is reactive across approximately 94% of pneumococcal strains. Biodegradable polyanhydrides have been studied as a nanoparticle-based vaccine (i.e., nanovaccine) platform to stabilize labile proteins, to provide adjuvanticity, and enhance patient compliance by providing protective immunity in a single dose. In this study, we designed a room temperature stable PspA-based polyanhydride nanovaccine that eliminated the need for a free protein component (i.e., 100% encapsulated within the nanoparticles). Mice were immunized once with the lead nanovaccine and upon challenge, presented significantly higher survival rates than animals immunized with soluble protein alone, even with a 25-fold reduction in protein dose. This lead nanovaccine formulation performed similarly to protein adjuvanted with Alum, however, with much less tissue reactogenicity at the site of immunization. By eliminating the free PspA from the nanovaccine formulation, the lead nanovaccine was efficacious after being stored dry for 60 days at room temperature, breaking the need for maintaining the cold chain. Altogether, this study demonstrated that a single dose PspA-based nanovaccine against S. pneumoniae induced protective immunity and provided thermal stability when stored at room temperature for at least 60 days.

Association of Pneumococcal Protein Antigen Serology With Age and Antigenic Profile of Colonizing Isolates

Background

Several Streptococcus pneumoniae proteins play a role in pathogenesis and are being investigated as vaccine targets. It is largely unknown whether naturally acquired antibodies reduce the risk of colonization with strains expressing a particular antigenic variant.

Methods

Serum immunoglobulin G (IgG) titers to 28 pneumococcal protein antigens were measured among 242 individuals aged <6 months-78 years in Native American communities between 2007 and 2009. Nasopharyngeal swabs were collected >- 30 days after serum collection, and the antigen variant in each pneumococcal isolate was determined using genomic data. We assessed the association between preexisting variant-specific antibody titers and subsequent carriage of pneumococcus expressing a particular antigen variant.

Results

Antibody titers often increased across pediatric groups before decreasing among adults. Individuals with low titers against group 3 pneumococcal surface protein C (PspC) variants were more likely to be colonized with pneumococci expressing those variants. For other antigens, variant-specific IgG titers do not predict colonization.

Conclusion

We observed an inverse association between variant-specific antibody concentration and homologous pneumococcal colonization for only 1 protein. Further assessment of antibody repertoires may elucidate the nature of antipneumococcal antibody-mediated mucosal immunity while informing vaccine development.

Towards Identifying Protective B-Cell Epitopes: The PspA Story

Pneumococcal surface protein A (PspA) is one of the most abundant cell surface protein of Streptococcus pneumoniae (S. pneumoniae). PspA variants are structurally and serologically diverse and help evade complement-mediated phagocytosis of S. pneumoniae, which is essential for its survival in the host. PspA is currently been screened for employment in the generation of more effective (serotype independent) vaccine to overcome the limitations of polysaccharide based vaccines, providing serotype specific immune responses. The cross-protection eliciting regions of PspA localize to the α-helical and proline rich regions. Recent data indicate significant variation in the ability of antibodies induced against the recombinant PspA variants to recognize distinct S. pneumoniae strains. Hence, screening for the identification of the topographical repertoire of B-cell epitopes that elicit cross-protective immune response seems essential in the engineering of a superior PspA-based vaccine. Herein, we revisit epitope identification in PspA and the utility of hybridoma technology in directing the identification of protective epitope regions of PspA that can be used in vaccine research.

A longitudinal study of natural antibody development to pneumococcal surface protein A families 1 and 2 in Papua New Guinean Highland children: a cohort study

BACKGROUND

Pneumococcal surface protein A (PspA), a conserved virulence factor essential for Streptococcus pneumoniae attachment to upper respiratory tract (URT) epithelia, is a potential vaccine candidate for preventing colonisation.

METHODS

This cohort study was conducted in the Asaro Valley in the Eastern Highlands Province of Papua New Guinea, of which Goroka town is the provincial capital. The children included in the analysis were participants in a neonatal pneumococcal conjugate vaccine trial (ClinicalTrials.gov NCT00219401) that was conducted between 2005 and 2009. We investigated the development of anti-PspA antibodies in the first 18 months of life relative to URT pneumococcal carriage in Papua New Guinean infants who experience one of the earliest and highest colonisation rates in the world. Blood samples and nasopharyngeal swabs were collected from a cohort of 88 children at ages 3, 9, and 18 months to quantify immunoglobulin G (IgG) levels to PspA families 1 and 2 using an enzyme-linked immunosorbent assay and to determine URT carriage.

RESULTS

Seventy-three per cent (64/88) of infants carried S. pneumoniae at age 3 months; 85 % (75/88) at 9 months, and 83 % (73/88) at 18 months. PspA-IgG levels declined between ages 3 and 9 months (p < 0.001), then increased between 9 and 18 months (p < 0.001). At age 3 months, pneumococcal carriers showed lower PspA1-IgG levels (geometric mean concentration [GMC] 602 arbitrary units [AU]/ml, 95 % confidence interval [CI] 497-728) than non-carriers (GMC 1058 AU/ml [95 % CI 732-1530]; p = 0.008), while at 9 months, PspA1- and PspA2-IgG levels were significantly higher in carriers (PspA1: 186 AU/ml, 95 % CI 136-256; PspA2: 284 AU/ml, 95 % CI 192-421) than in non-carriers (PspA1 87 AU/ml, 95 % CI 45-169; PspA2 74 AU/ml, 95 % CI 34-159) (PspA1: p = 0.037, PspA2: p = 0.003).

CONCLUSION

Our findings confirm that PspA is immunogenic and indicate that natural anti-PspA immune responses are acquired through exposure and develop with age. PspA may be a useful candidate in an infant pneumococcal vaccine to prevent early URT colonisation.

Preparation and testing of a Vi conjugate vaccine using pneumococcal surface protein A (PspA) from Streptococcus pneumoniae as the carrier protein

In the current study pneumococcal surface protein A (PspA) was conjugated to Vi capsular polysaccharide from Salmonella Typhi to make available a vaccine against typhoid fever that has the potential to also provide broad protection from Streptococcus pneumoniae. High yielding production processes were developed for the purification of PspAs from families 1 and 2. The purified PspAs were conjugated to Vi with high recovery of both Vi and PspA. The processes developed especially for PspA family 2 could readily be adapted for large scale production under cGMP conditions. Previously we have shown that conjugation of diphtheria toxoid (DT) to Vi polysaccharide improves the immune response to Vi but can also enhance the response to DT. In this study it was shown that conjugation of PspA to Vi enhanced the anti-PspA response and that PspA was a suitable carrier protein as demonstrated by the characteristics of a T-cell dependent response to the Vi. We propose that a bivalent vaccine consisting of PspA from families 1 and 2 bound to Vi polysaccharide would protect against typhoid fever and has the potential to also protect against pneumococcal disease and should be considered for use in developing countries.

A live-attenuated pneumococcal vaccine elicits CD4+ T-cell dependent class switching and provides serotype independent protection against acute otitis media

Acute otitis media (AOM) caused by Streptococcus pneumoniae remains one of the most common infectious diseases worldwide despite widespread vaccination. A major limitation of the currently licensed pneumococcal vaccines is the lack of efficacy against mucosal disease manifestations such as AOM, acute bacterial sinusitis and pneumonia. We sought to generate a novel class of live vaccines that (1) retain all major antigenic virulence proteins yet are fully attenuated and (2) protect against otitis media. A live vaccine candidate based on deletion of the signal recognition pathway component ftsY induced potent, serotype-independent protection against otitis media, sinusitis, pneumonia and invasive pneumococcal disease. Protection was maintained in animals coinfected with influenza virus, but was lost if mice were depleted of CD4(+) T cells at the time of vaccination. The live vaccine induced a strong serum IgG2a and IgG2b response that correlated with CD4(+) T-cell mediated class switching. Deletion of genes required for microbial adaptation to the host environment is a novel live attenuated vaccine strategy yielding the first experimental vaccine effective against pneumococcal otitis media.

IgG responses to Pneumococcal and Haemophilus influenzae protein antigens are not impaired in children with a history of recurrent acute otitis media

Background

Vaccines including conserved antigens from Streptococcus pneumoniae and nontypeable Haemophilus influenzae (NTHi) have the potential to reduce the burden of acute otitis media. Little is known about the antibody response to such antigens in young children with recurrent acute otitis media, however, it has been suggested antibody production may be impaired in these children.

Methods

We measured serum IgG levels against 4 pneumococcal (PspA1, PspA 2, CbpA and Ply) and 3 NTHi (P4, P6 and PD) proteins in a cross-sectional study of 172 children under 3 years of age with a history of recurrent acute otitis media (median 7 episodes, requiring ventilation tube insertion) and 63 healthy age-matched controls, using a newly developed multiplex bead assay.

Results

Children with a history of recurrent acute otitis media had significantly higher geometric mean serum IgG levels against NTHi proteins P4, P6 and PD compared with healthy controls, whereas there was no difference in antibody levels against pneumococcal protein antigens. In both children with and without a history of acute otitis media, antibody levels increased with age and were significantly higher in children colonised with S. pneumoniae or NTHi compared with children that were not colonised.

Conclusions

Proteins from S. pneumoniae and NTHi induce serum IgG in children with a history of acute otitis media. The mechanisms in which proteins induce immunity and potential protection requires further investigation but the dogma of impaired antibody responses in children with recurrent acute otitis media should be reconsidered.

Adenoidectomy in young children and serum IgG antibodies to pneumococcal surface protein A and choline binding protein A

OBJECTIVE

We have previously reported that surgical removal of the nasopharyngeal adenoid in young children resulted in increased risk of nasopharyngeal colonization by pneumococci. We now investigated whether adenoidectomy influences the development of serum IgG antibodies to pneumococcal choline-binding protein A (CbpA) and pneumococcal surface protein A (PspA).

METHODS

Altogether 217 children aged 12-48 months who had recurrent or persistent otitis media were randomized to undergo or not to undergo adenoidectomy. All the children underwent insertion of tympanostomy tubes. 166 children were followed-up for 3 years. The main outcome measures were concentrations of serum IgG antibodies to CbpA and PspA three years after randomization. Nasopharyngeal colonization by pneumococci was assessed 1, 2, and 3 years after randomization.

RESULTS

Adenoidectomy decreased concentrations of CbpA antibodies by ca. 25% independently of the observed increase in pneumococcal carriage (OR of log(10) transformed concentrations 0.74, 95% CI 0.58-0.94, P=0.016). Concentrations of PspA antibodies were lower and they seemed not to be influenced by adenoidectomy.

CONCLUSIONS

Adenoidectomy in young children causes a small but detectable impairment in the development of serum IgG antibodies to pneumococcal CbpA. The adenoid seems to have a role in augmenting systemic immunity against pneumococci.

Development of cross-reactive antibodies to the proline-rich region of pneumococcal surface protein A in children

Pneumococcal surface protein A (PspA) is an important virulence factor of Streptococcus pneumoniae and a candidate for inclusion in future protein-based vaccines. The surface-exposed α-helical region of PspA is immunogenic and frequently cross-reactive, but also variable in structure. Sequence and serological differences in this region divide PspAs into two major families. We showed previously that children preferentially develop antibodies limited to the PspA family of the colonizing strain. In this study, sera of children with history of pneumococcal colonization were analyzed for presence of IgG antibodies to the conserved proline-rich region (PRR) of PspA. The results indicate that children produce antibodies to the PRR upon exposure to pneumococci. The PRR-specific antibodies were elicited regardless of the PspA family of the infecting strain. The results indicate that the PRR antigen elicits broadly cross-reactive antibodies that may have the potential to provide cross-protection against a broad spectrum of pneumococcal strains.

Natural antibodies against several pneumococcal virulence proteins in children during the pre-pneumococcal-vaccine era: the generation R study

The currently available pneumococcal vaccines do not protect against all serotypes of Streptococcus pneumoniae. A shift toward nonvaccine serotypes causing colonization and invasive disease has occurred, and studies on protein-based vaccines have been undertaken. We assessed the association between specific antibodies against pneumococcal virulence proteins and colonization and respiratory tract infections (RTIs). Additionally, we assessed the extent to which colonization induces a humoral immune response. Nasopharyngeal swabs collected from children at 1.5, 6, 14, and 24 months of age were cultured for pneumococcus. Serum samples were obtained at birth and at 6, 14, and 24 months (n = 57 children providing 177 serum samples). Data were collected prior to the pneumococcal vaccine era. IgG, IgA, and IgM levels against 17 pneumococcal protein vaccine candidates were measured using a bead-based flow cytometry technique (xMAP; Luminex Corporation). Information regarding RTIs was questionnaire derived. Levels of IgG against all proteins were high in cord blood, decreased in the first 6 months and increased again thereafter, in contrast to the course of IgA and IgM levels. Specific antibodies were induced upon colonization. Increased levels of IgG against BVH-3, NanA, and SP1003 at 6 months, NanA, PpmA, PsaA, SlrA, SP0189, and SP1003 at 14 months, and SlrA at 24 months were associated with a decreased number of RTIs in the third year of life but not with colonization. Maternal antipneumococcal antibodies did not protect against pneumococcal colonization and infection. Certain antibodies against pneumococcal virulence proteins, some of which are induced by colonization, are associated with a decreased number of RTIs in children. This should be taken into account in future pneumococcal vaccine studies.

Maternal antibodies to pneumolysin but not to pneumococcal surface protein A delay early pneumococcal carriage in high-risk Papua New Guinean infants

Immunization of pregnant women can be an efficient strategy to induce early protection in infants in developing countries. Pneumococcal protein-based vaccines may have the capacity to induce pneumococcal serotype-independent protection. To understand the potential of maternal pneumococcal protein-specific antibodies in infants in high-risk areas, we studied the placental transfer of naturally acquired antibodies to pneumolysin (Ply) and pneumococcal surface protein A family 1 and 2 (PspA1 and PspA2) in relation to onset of pneumococcal nasopharyngeal carriage in infants in Papua New Guinea (PNG). In this study, 76% of the infants carried Streptococcus pneumoniae in the upper respiratory tract within the first month of life, at a median age of 19 days. Maternal and cord blood antibody titers to Ply (rho = 0.824, P < 0.001), PspA1 (rho = 0.746, P < 0.001), and PspA2 (rho = 0.631, P < 0.001) were strongly correlated. Maternal pneumococcal carriage (hazard ratio [HR], 2.60; 95% confidence interval [CI], 1.25 to 5.39) and younger maternal age (HR, 0.74; 95% CI, 0.54 to 1.00) were independent risk factors for early carriage, while higher cord Ply-specific antibody titers predicted a significantly delayed onset (HR, 0.71; 95% CI, 0.52 to 1.00) and cord PspA1-specific antibodies a significantly younger onset of carriage in PNG infants (HR, 1.57; 95% CI, 1.03 to 2.40). Maternal vaccination with a pneumococcal protein-based vaccine should be considered as a strategy to protect high-risk infants against pneumococcal disease by reducing carriage risks in both mothers and infants.

PspA family fusion proteins delivered by attenuated Salmonella enterica serovar Typhimurium extend and enhance protection against Streptococcus pneumoniae

Pneumococcal surface protein A (PspA) is highly immunogenic and can induce a protective immune response against pneumococcal infection. PspA is divided into two major families based on serological variability: family 1 and family 2. To provide broad protection, PspA proteins from pneumococcal strains Rx1 (family 1) and EF5668 (family 2) were combined to form two PspA fusion proteins, PspA/Rx1-EF5668 and PspA/EF5668-Rx1. Each protein was fused to a type II secretion signal and delivered by a recombinant attenuated Salmonella vaccine (RASV). Both PspA/Rx1-EF5668 and PspA/EF5668-Rx1 were synthesized in the RASV and secreted into the periplasm and supernatant. The fusion proteins reacted strongly with both anti-PspA/Rx1 and anti-PspA/EF5668 antisera. Oral immunization of BALB/c mice with RASV synthesizing either PspA fusion protein elicited serum immunoglobulin G (IgG) and mucosal IgA responses against both families of PspA. Analysis of IgG isotypes (IgG2a and IgG1) indicated a strong Th1 bias to the immune responses to both proteins. Sera from mice immunized with RASV synthesizing PspA/Rx1-EF5668 bound to the surface and directed C3 complement deposition on representative strains from all five PspA clades. Immunization with RASV synthesizing either protein protected mice against intraperitoneal challenge with Streptococcus pneumoniae WU2 strain (family 1), intravenous challenge with S. pneumoniae 3JYP2670 strain (family 2), and intranasal challenge with S. pneumoniae A66.1 (family 1). The PspA/Rx1-EF5668 protein elicited significantly greater protection than PspA/EF5668-Rx1, PspA/Rx1, or PspA/EF5668. These results indicate an RASV synthesizing a PspA fusion protein representing both PspA families constitutes an effective antipneumococcal vaccine, extending and enhancing protection against multiple strains of S. pneumoniae.

Distribution of pneumococcal surface protein A families 1 and 2 among Streptococcus pneumoniae isolates from children in finland who had acute otitis media or were nasopharyngeal carriers

PspA is a structurally variable surface protein important to the virulence of pneumococci. PspAs are serologically cross-reactive and exist as two major families. In this study, we determined the distribution of PspA families 1 and 2 among pneumococcal strains isolated from the middle ear fluid (MEF) of children with acute otitis media and from nasopharyngeal specimens of children with pneumococcal carriage. We characterized the association between the two PspA families, capsular serotypes, and multilocus sequence types (STs) of the pneumococcal isolates. MEF isolates (n = 201) of 109 patients and nasopharyngeal isolates (n = 173) of 49 children were PspA family typed by whole-cell enzyme immunoassay (EIA). Genetic typing (PCR) of PspA family was done for 60 isolates to confirm EIA typing results. The prevalences of PspA families 1 and 2 were similar among pneumococci isolated from MEF (51% and 45%, respectively) and nasopharyngeal specimens (48% each). Isolates of certain capsule types as well as isolates of certain STs showed statistical associations with either family 1 or family 2 PspA. Pneumococci from seven children with multiple pneumococcal isolates appeared to express serologically different PspA families in different isolates of the same serotype; in three of the children the STs of the isolates were the same, suggesting that antigenic changes in the PspA expressed may have taken place. The majority of the isolates (97%) belonged to either PspA family 1 or family 2, suggesting that a combination including the two main PspA families would make a good vaccine candidate.