Kyung Hyo Kim

Nontypeable Pneumococci Can Be Divided into Multiple cps Types, Including One Type Expressing the Novel Gene pspK

ABSTRACT Although virulence of Streptococcus pneumoniae is associated with its capsule, some pathogenic S. pneumoniae isolates lack capsules and are serologically nontypeable (NT). We obtained 64 isolates that were identified as NT “pneumococci” (i.e., bacteria satisfying the conventional definition but without the multilocus sequence typing [MLST]-based definition of S. pneumoniae) by the traditional criteria. All 64 were optochin sensitive and had lytA, and 63 had ply. Twelve isolates had cpsA, suggesting the presence of a conventional but defective capsular polysaccharide synthesis (cps) locus. The 52 cpsA-negative isolates could be divided into three null capsule clades (NCC) based on aliC (aliB-like ORF1), aliD (aliB-like ORF2), and our newly discovered gene, pspK, in their cps loci. pspK encodes a protein with a long alpha-helical region containing an LPxTG motif and a YPT motif known to bind human pIgR. There were nine isolates in NCC1 (pspK+ but negative for aliC and aliD), 32 isolates in NCC2 (aliC+ aliD+ but negative for pspK), and 11 in NCC3 (aliD+ but negative for aliC and pspK). Among 52 cpsA-negative isolates, 41 were identified as S. pneumoniae by MLST analysis. All NCC1 and most NCC2 isolates were S. pneumoniae, whereas all nine NCC3 and two NCC2 isolates were not S. pneumoniae. Several NCC1 and NCC2 isolates from multiple individuals had identical MLST and cps regions, showing that unencapsulated S. pneumoniae can be infectious among humans. Furthermore, NCC1 and NCC2 S. pneumoniae isolates could colonize mice as well as encapsulated S. pneumoniae, although S. pneumoniae with an artificially disrupted cps locus did not. Moreover, an NCC1 isolate with pspK deletion did not colonize mice, suggesting that pspK is critical for colonization. Thus, PspK may provide pneumococci a means of surviving in the nasopharynx without capsule. IMPORTANCE The presence of a capsule is critical for many pathogenic bacteria, including pneumococci. Reflecting the pathogenic importance of the pneumococcal capsule, pneumococcal vaccines are designed to elicit anticapsule antibodies. Additional evidence for the pathogenic importance of the pneumococcal capsule is the fact that in pneumococci all the genes necessary for capsule production are together in one genetic locus, which is called the cps locus. However, there are occasional pathogenic pneumococci without capsules, and how they survive in the host without the capsule is unknown. Here, we show that in these acapsular pneumococci, the cps loci have been replaced with various novel genes and they can colonize mouse nasopharynges as well as capsulated pneumococci. Since the genes that replace the cps loci are likely to be important in host survival, they may show new and/or alternative capsule-independent survival mechanisms used by pneumococci. The presence of a capsule is critical for many pathogenic bacteria, including pneumococci. Reflecting the pathogenic importance of the pneumococcal capsule, pneumococcal vaccines are designed to elicit anticapsule antibodies. Additional evidence for the pathogenic importance of the pneumococcal capsule is the fact that in pneumococci all the genes necessary for capsule production are together in one genetic locus, which is called the cps locus. However, there are occasional pathogenic pneumococci without capsules, and how they survive in the host without the capsule is unknown. Here, we show that in these acapsular pneumococci, the cps loci have been replaced with various novel genes and they can colonize mouse nasopharynges as well as capsulated pneumococci. Since the genes that replace the cps loci are likely to be important in host survival, they may show new and/or alternative capsule-independent survival mechanisms used by pneumococci.

Immune Response in Infants to the Heptavalent Pneumococcal Conjugate Vaccine against Vaccine-Related Serotypes 6A and 19A

ABSTRACT The currently available 7-valent pneumococcal conjugate vaccine (PCV7) elicits good immune response to and is effective against vaccine serotypes. However, its effectiveness against vaccine-related serotypes is variable. Serum samples were obtained 1 month after the last vaccination from 31 infants immunized with PCV7 at 2, 4, and 6 months of age. The sera were used to determine immunoglobulin G antibody levels to eight serotypes (seven vaccine serotypes and serotype 19A) with enzyme-linked immunosorbent assay (ELISA) and opsonic capacity against 11 serotypes (seven vaccine serotypes, serotypes 19A and 6A, and nonvaccine serotypes 5 and 7F) using a multiplexed opsonization assay. ELISA results showed antibody concentrations varied between 1.84 and 10.49 μg/ml, and all subjects had antibody concentrations of ≥0.35 μg/ml for all serotypes, including serotype 19A. In contrast, the opsonic index was detectable (i.e., opsonic index ≥ 8) in all children for the seven vaccine serotypes, 81% for serotype 6A, and merely 19% for serotype 19A. PCV7 shows good immunogenicity for vaccine serotypes in infants after a primary series. PCV7 does not elicit opsonic antibodies to serotype 19A. ELISA may thus be an inadequate surrogate assay for evaluating the response for cross-reactive serotypes in infants.

The Causative Organisms of Bacterial Meningitis in Korean Children in 1996-2005

Bacterial meningitis remains a serious cause of morbidity and mortality in childhood, despite the availability of effective vaccines against Haemophilus influenzae type b (Hib) or Streptococcus pneumoniae. The purpose of this study was to analyze data on bacterial meningitis cases in Korea from 1996 through 2005. The information of all hospitalized bacteria-proven meningitis cases was obtained from 17 university hospitals nationwide. A total of 402 cases were identified. Of these, 125 (29.9%) cases were neonates. Streptococcus agalactiae was the most common bacteria responsible for 99 (24.6%) of all cases regardless of age, followed by S. pneumoniae for 91 (22.6%) and H. influenzae for 67 (16.7%) patients. The common etiology beyond the neonatal period was S. pneumoniae for 91 (33.0%) followed by H. influenzae for 63 (22.8%) patients. The overall case fatality rate was 9.4%, which was similar with that in 1986-1995. In conclusion, S. agalactiae, S. pneumoniae and H. influenzae were important etiologic agents of bacterial meningitis in children in the last 10 yrs. It is required to establish the preventive strategy of the three bacteria. The nationwide epidemiologic study should be continued to evaluate immunization strategy and efficacy.

Immunogenicity of the 9-Valent HPV Vaccine Using 2-Dose Regimens in Girls and Boys vs a 3-Dose Regimen in Women

Importance Human papillomavirus (HPV) infections cause anogenital cancers and warts. The 9-valent HPV vaccine provides protection against 7 high-risk types of HPV responsible for 90% of cervical cancers and 2 other HPV types accounting for 90% of genital warts. Objective To determine whether HPV type-specific antibody responses would be noninferior among girls and boys aged 9 to 14 years after receiving 2 doses of the 9-valent HPV vaccine compared with adolescent girls and young women aged 16 to 26 years receiving 3 doses. Design, Setting, and Participants Open-label, noninferiority, immunogenicity trial conducted at 52 ambulatory care sites in 15 countries. The study was initiated on December 16, 2013, with the last participant visit for this report on June 19, 2015. Five cohorts were enrolled: (1) girls aged 9 to 14 years to receive 2 doses 6 months apart (n = 301); (2) boys aged 9 to 14 years to receive 2 doses 6 months apart (n = 301); (3) girls and boys aged 9 to 14 years to receive 2 doses 12 months apart (n = 301); (4) girls aged 9 to 14 years to receive 3 doses over 6 months (n = 301); and (5) a control group of adolescent girls and young women aged 16 to 26 years to receive 3 doses over 6 months (n = 314). Interventions Two doses of the 9-valent HPV vaccine administered 6 or 12 months apart or 3 doses administered over 6 months. Main Outcomes and Measures The primary end point was prespecified as the antibody response against each HPV type assessed 1 month after the last dose using a competitive immunoassay. Each of the three 2-dose regimens was compared with the standard 3-dose schedule in adolescent girls and young women using a noninferiority margin of 0.67 for the ratio of the antibody geometric mean titers. Results Of the 1518 participants (753 girls [mean age, 11.4 years]; 451 boys [mean age, 11.5 years]; and 314 adolescent girls and young women [mean age, 21.0 years]), 1474 completed the study and data from 1377 were analyzed. At 4 weeks after the last dose, HPV antibody responses in girls and boys given 2 doses were noninferior to HPV antibody responses in adolescent girls and young women given 3 doses (P < .001 for each HPV type). Compared with adolescent girls and young women who received 3 doses over 6 months, the 1-sided 97.5% CIs for the ratio of HPV antibody geometric mean titers at 1 month after the last dose across the 9 HPV subtypes ranged from 1.36 to ∞ to 2.50 to ∞ for girls who received 2 doses 6 months apart; from 1.37 to ∞ to 2.55 to ∞ for boys who received 2 doses 6 months apart; and from 1.61 to ∞ to 5.36 to ∞ for girls and boys who received 2 doses 12 months apart. Conclusions and Relevance Among girls and boys aged 9 to 14 years receiving 2-dose regimens of a 9-valent HPV vaccine separated by 6 or 12 months, immunogenicity 4 weeks after the last dose was noninferior to a 3-dose regimen in a cohort of adolescent girls and young women. Further research is needed to assess persistence of antibody responses and effects on clinical outcomes. Trial Registration clinicaltrials.gov Identifier: NCT01984697.

The effect of age on the response to the pneumococcal polysaccharide vaccine

BackgroundStreptococcus pneumoniae is a leading cause of morbidity and mortality in the elderly. To prevent invasive pneumococcal diseases, the 23-valent pneumococcal polysaccharide vaccine (PPV) is recommended in subjects over 65 years of age. Although it has been reported to provide approximately 50-80% protection against invasive disease in the general elderly population, there is still controversy as to the effectiveness of the PPV in the elderly.MethodsTo evaluate the immune response to the pneumococcal polysaccharide vaccine in the elderly, samples from young adults and elderly were obtained before and one month after vaccination. The quantitative and qualitative response to the vaccine were measured by the ELISA and opsonophagocytic killing assay for eight vaccine type serotypes (4, 6B, 9V, 14, 18C, 19A, 19F, 23F) and one vaccine-related serotype (6A).ResultsThe response to the pneumococcal polysaccharide vaccine showed a similar response between adults and elderly when evaluated by the ELISA, however the functional activity of the antibodies elicited after vaccination were lower in the elderly group for more than half of the serotypes evaluated. In comparison of the antibody needed for 1:8 opsonic titer, more antibodies were needed in the elderly for serotypes Pn 4, 19F, 23F and 6A, suggesting the functional activity of antibody detected by the ELISA was lower in the elderly compared with the adult group for these serotypes. As for subjects with an opsonic titer <8 after vaccination, only one subject each for serotypes Pn 4, 9V and 6A were found in the adult group. However, up to 10 (30.3%) of the subjects did not show opsonic activity after vaccination in the elderly group for serotypes Pn 4, 9V, 14, 19A and 6A.ConclusionsAlthough the amount of antibodies elicited were similar between the two age groups, distinct differences in function were noted. This report highlights the importance of a quantitative and qualitative evaluation of the immunogenic response to the PPV in the elderly age group.Trial registrationThis trial is registered with Clinical trials.gov. Registration number NCT00964769

Development of an Automated and Multiplexed Serotyping Assay for Streptococcus pneumoniae

ABSTRACT Streptococcus pneumoniae expresses more than 90 capsule types, and currently available pneumococcal vaccines are designed to provide serotype-specific protection. Consequently, serotyping of pneumococcal isolates is important for determining the serotypes to be included in pneumococcal vaccines and to monitor their efficacy. Yet serotyping of pneumococcal isolates has remained a significant technical challenge. By multiplexing many assays, we have now developed a simple yet comprehensive serotyping assay system that can not only identify all known pneumococcal serotypes but also subdivide nontypeable (NT) isolates into those with or without the conventional capsule locus. We have developed this assay system to require only six key reagents: two are used in one multiplex inhibition-type immunoassay, and four are required in two multiplex PCR-based assays. The assay system is largely automated by a seamless combination of monoclonal antibody-based and PCR-based multiplex assays using the flow cytometric bead array technology from Luminex. The assay system has been validated with a panel of pneumococci expressing all known pneumococcal serotypes and was found to be easily transferable to another laboratory.

Genetic, biochemical, and serological characterization of a new pneumococcal serotype, 6H, and generation of a pneumococcal strain producing three different capsular repeat units.

ABSTRACT Streptococcus pneumoniae clinical isolates were recently described that produced capsular polysaccharide with properties of both serotypes 6A and 6B. Their hybrid serological property correlated with mutations affecting the glycosyltransferase WciP, which links rhamnose to ribitol by an α(1-3) linkage for serotypes 6A and 6C and an α(1-4) linkage for serotypes 6B and 6D. The isolates had mutations in the triad residues of WciP that have been correlated with enzyme specificity. The canonical triad residues of WciP are Ala192-Ser195-Arg254 for serotypes 6A and 6C and Ser192-Asn195-Gly254 for serotypes 6B and 6D. To prove that the mutations in the triad residues are responsible for the hybrid serotype, we introduced the previously described Ala192-Cys195-Arg254 triad into a 6A strain and found that the change made WciP bispecific, resulting in 6A and 6B repeat unit expression, although 6B repeat unit production was favored over production of 6A repeat units. Likewise, this triad permitted a 6C strain to express 6C and 6D repeat units. With reported bispecificity in WciN, which adds either glucose or galactose as the second sugar in the serogroup 6 repeat unit, the possibility exists for a strain to simultaneously produce all four serogroup 6 repeat units; however, when genes encoding both bispecific enzymes were introduced into a 6A strain, only 6A, 6B, and 6D repeat units were detected serologically. Nonetheless, this may be the first example of a bacterial polysaccharide with three different repeat units. This strategy of expressing multiple repeat units in a single polymer is a novel approach to broadening vaccine coverage by eliminating the need for multiple polysaccharide sources to cover multiple serogroup members.

Seroepidemiology of hepatitis A in Korea: changes over the past 30 years.

This study aimed to assess the immune status of the Korean population against hepatitis A virus (HAV). Residual serum samples from 2008 to 2010 were collected from diagnostic laboratories and a total of 1,872 samples were analyzed. Anti-HAV seroprevalence was 57.3% in subjects aged 1-4 yr, 69.8% at 5-9 yr and decreased to 38.8% at 10-14 yr, 13.0% at 15-19 yr, and 11.7% at 20-29 yr. Seroprevalence increased with increasing age: 52.2% at 30-39 yr, 83.2% at 40-49 yr, 81.4% at 50-59 yr, 93.2% at 60-69 yr, and 95.1% at 70-79 yr. The most susceptible age group consisted of subjects aged 10-29 yr, especially those aged 20-29 yr. This pattern is markedly different from that in the past 3 decades, where the most susceptible group had consisted of children aged less than 10 yr and almost all subjects aged more than 20 yr had developed anti-HAV antibodies. Because of improvements in hygiene and introduction of hepatitis A vaccine, the age demographic of the susceptible population has shifted. These data are important for creating new prevention measures, including vaccination policies, to prevent and control outbreaks of hepatitis A in Korea.

Enterovirus 71 infection: An experience in Korea, 2009

Enterovirus 71 (EV71) has been recognized as a frequent cause of epidemics of hand-foot-and-mouth disease (HFMD) associated with severe neurological symptoms. In the spring of 2009, HFMD was epidemic in Korea. Severe cases with complication, including death, have been reported and it has become a public health issue. Most symptomatic EV71 infections commonly result in HFMD or herpangina. These clinical manifestations can be associated with neurologic syndromes frequently. Neurologic syndromes observed in EV71 include meningitis, meningoencephalomyelitis, poliomyelitis-like paralytic disease, Guillain-Barré syndrome, transverse myelitis, cerebellar ataxia, opsoclonus-myoclonus syndrome, benign intracranial hypertension, and brainstem encephalitis. Examinations for EV 71 were performed from the stools, respiratory secretion or CSF of the children by realtime PCR. Gene analysis showed that most of them were caused by EV71 subgenotype C4a which was prevalent in China, 2008. Public health measures including personal and environmental hygiene, must to target daycare centers, kindergartens, and schools where highly susceptible children congregate. To prevent the spread of infection, preschools where transmission persists for more than 2 incubation periods, have been recommended for closure, and trigger criteria for voluntary closure was instituted. During closure, operators are to thoroughly clean the centers before they are allowed to reopen. In addition, parents are advised to ensure that their children adopt a high standard of personal hygiene and to keep the infected child at home until full recovery. Because the outbreaks occur in a cyclical pattern, surveillance system to predict next outbreaks and adequate public health measures to control need to be planned for future. Control of EV71 epidemics through surveillance and public health intervention needs to be maintained in Korea. Future research should focus on understanding of EV71 virulence, identification of the receptor(s) for EV71, development of antiviral agents and development of vaccine.

Prevalence of primary immunodeficiency in Korea

This study represents the first epidemiological study based on the national registry of primary immunodeficiencies (PID) in Korea. Patient data were collected from 23 major hospitals. A total of 152 patients with PID (under 19 yr of age), who were observed from 2001 to 2005, have been entered in this registry. The period prevalence of PID in Korea in 2005 is 11.25 per million children. The following frequencies were found: antibody deficiencies, 53.3% (n = 81), phagocytic disorders, 28.9% (n = 44); combined immunodeficiencies, 13.2% (n = 20); and T cell deficiencies, 4.6% (n = 7). Congenital agammaglobulinemia (n = 21) and selective IgA deficiency (n = 21) were the most frequently reported antibody deficiency. Other reported deficiencies were common variable immunodeficiencies (n = 16), X-linked agammaglobulinemia (n = 15), IgG subclass deficiency (n = 4). Phagocytic disorder was mostly chronic granulomatous disease. A small number of patients with Wiskott-Aldrich syndrome, hyper-IgE syndrome, and severe combined immunodeficiency were also registered. Overall, the most common first manifestation was pneumonia. This study provides data that permit a more accurate estimation PID patients in Korea.