Serum antibody responses in children with rotavirus diarrhea can serve as proxy for protection.

We examined sera from 42 patients 1 to 30 months of age for rotavirus immunoglobulin M (IgM), IgA, IgG, and IgG subclasses and sought to determine if serum antibody could serve as a reliable marker for prediction of disease severity. Infants in the first few months of life usually had high maternal IgG titers and, when they were infected with rotavirus, had low IgM titers or no IgM in acute-phase sera and poor seroconversions 3 weeks later, suggesting that maternal antibodies had inhibited viral replication and antibody responses. All patients > or =6 months of age had IgM in acute-phase sera, indicating that IgM is a good marker for acute rotavirus infection. IgG was the best overall predictor of an infection, as the convalescent-phase sera of 81% of the patients had a fourfold rise in the IgG titer. IgA titers in convalescent-phase sera and conversion rates were higher among patients > or =12 months of age than among children younger than 12 months. IgG1 was the predominant subclass detected in the acute-phase sera of some children and in all 28 convalescent-phase serum samples examined. Patients with preexisting acute-phase IgG titers of > or =100 or > or =200 had diarrhea that was less severe or of a shorter duration. These results indicate that serum IgG is the most reliable marker for seroconversion and is a consistent proxy for protection against severe disease.

Cytokines as mediators for or effectors against rotavirus disease in children.

Rotavirus is the most common cause of severe gastroenteritis in young children, but the pathogenesis and immunity of this disease are not completely understood. To examine the host response to acute infection, we collected paired serum specimens from 30 children with rotavirus diarrhea and measured the levels of nine cytokines (interleukin-1beta [IL-1beta], IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, gamma interferon [IFN-gamma], and tumor necrosis factor alpha [TNF-alpha]) using a microsphere-based Luminex Flowmetrix system. Patients with acute rotavirus infection had elevated median levels of seven cytokines in serum, and of these, the levels of three (IL-6, IL-10, and IFN-gamma) were significantly (P < 0.05) higher than those in serum from control children without diarrhea. Patients with fever had significantly (P < 0.05) higher levels of IL-6 in serum than control children, and those with fever and more episodes of diarrhea had significantly (P < 0.05) higher levels of TNF-alpha than those without fever and with fewer episodes of diarrhea. We further demonstrated a negative association (P < 0.05) between the levels of IL-2 and the number of stools on the day on which the first blood sample was collected. Finally, patients with vomiting had significantly (P < 0.05) lower levels of IFN-gamma than those without vomiting. Our pilot study provides evidence that the types and magnitudes of cytokine responses to rotavirus infection in children influence or reflect the clinical outcome of disease. These findings suggest that certain cytokines may play an important role in the pathogenesis of and the protection against rotavirus disease in children and, consequently, may provide directions and insights that could prove critical to the prevention or treatment of this important disease.

Comparative detection of measles and rubella IgM and IgG derived from filter paper blood and serum samples.

We compared the use of serum and filter paper blood spots as specimen sources for the detection of measles- and rubella-specific IgM and IgG. We collected capillary blood into microtainer tubes and onto filter paper spots from 60 children and 60 healthy adults. The blood was collected from 12-15-month-old children approximately 3 weeks after primary vaccination with measles, mumps, rubella vaccine, and the sample-pairs were tested for measles-specific IgM and IgG antibodies by using a capture antibody EIA and an indirect EIA, respectively. We tested sample-pairs from a subset of participants for rubella- specific IgM and IgG antibodies by using commercially available capture IgM (Captia) and indirect IgG (Wampole) assays. The concordance of results from serum and filter paper blood spots was high for all assays: 98% for measles IgM, 93% for measles IgG, 94% for rubella IgM, and 93% for rubella IgG, and increased to between 96-100% for all four assays when indeterminate samples were excluded. The correlation coefficients for EIA signals were 0.99 and 0.77 for measles IgM and IgG, respectively, and 0.92 and 0.94 for rubella IgM and IgG, respectively. The cut-off values used for filter paper samples were the same as those used for serum samples for all tests except for the rubella IgM assay. The use of filter paper blood spots is a promising future option for the detection of measles- and rubella-specific antibodies.

Induction of cytokine mRNA in peripheral blood mononuclear cells of infants after the first dose of measles vaccine.

To better characterize the cytokine response to measles virus vaccine, we examined the levels of IL-2, IL-4, IL-5, IL-10, IL-12 and gamma-interferon (gamma-IFN) in measles virus-stimulated peripheral blood mononuclear cells from 18 donors before and 2 weeks after vaccination. Donors were grouped as seropositive or seronegative on the basis of measles-specific IgM antibody present at 2 weeks postvaccination. After vaccination, similar levels of upregulation of IL-2 and gamma-IFN mRNA were observed in the two groups. The majority of donors in both groups did not exhibit an increase in measles specific IL-4 or IL-10 mRNA after vaccination. IL-12 mRNA was not induced by measles virus in any of the donors. A statistically significant upregulation of IL-5 mRNA was observed among seropositive (9/13) compared with seronegative (1/5) donors after vaccination (P=0.09, one tailed Fisher's test). The observed measles specific induction of IL-5 mRNA is suggestive of a possible association between IL-5 production and an antibody response to measles virus.

Antibody responses of healthy infants to concurrent administration of a bivalent haemophilus influenzae type b-hepatitis B vaccine with diphtheria-tetanus-pertussis, polio and measles-mumps-rubella vaccines.

OBJECTIVE: To confirm that children given a bivalent Haemophilus influenzae type b-hepatitis B vaccine (bivalent Hib-HB vaccine; COMVAX) concurrently with priming doses of diphtheria-tetanus-pertussis vaccine (DTP), a booster dose of diphtheria-tetanus-acellular pertussis vaccine (DTaP), inactivated or oral polio vaccine (IPV or OPV) and measles-mumps-rubella vaccine (M-M-R(II)) have satisfactory antibody responses to all antigens. DESIGN: 126 healthy 2-month-old infants were scheduled to receive bivalent Hib-HB vaccine concurrently with DTP (2 and 4 months of age), OPV or IPV (random allocation to OPV or IPV at 2 months of age; OPV at 4 and 14 to 15 months of age), DTaP and M-M-R(II) (14 to 15 months of age). A response was judged "adequate" if the lower bound of the 95% confidence interval on the proportion of vaccinees having a critical antibody level was <10 percentage points below prediction. RESULTS: Antibodies to hepatitis B virus surface antigen, H. influenzae polysaccharide, diphtheria toxin, tetanus toxin, pertussis agglutinogens, pertussis toxin (as measured by enzyme immunoassay but not by Chinese hamster ovary cell assay), pertussis filamentous haemagglutinin after a booster dose of DTaP, poliovirus type 2, measles virus, and mumps virus all equalled or exceeded expected levels. Antibodies to rubella virus and pertussis filamentous haemagglutinin (after priming doses of DTP) fell slightly, and in the case of rubella significantly, below predicted levels. Antibodies to poliovirus types 1 and 3 were also below expectation after 2 doses of polio vaccine but were adequate following a third dose of vaccine. CONCLUSION: Concurrent administration of bivalent Hib-HB vaccine with priming doses of DTP, a booster dose of DTaP, OPV, IPV, or M-M-R(II) was well tolerated and, with the possible exception of rubella, did not substantially impair the antibody response to any antigen.

Infection control programs at children's hospitals: a description of structures and processes.

BACKGROUND: Infection control (IC) structures and processes determine the effectiveness of surveillance efforts to prevent infections in health care settings. METHODS: A survey was sent to 56 children's hospitals collaborating in the Pediatric Prevention Network (PPN). RESULTS: Completed surveys were returned from 48 hospitals. Responsibility for the IC program resided with the medical director (21%); vice president for patient care (18%); quality improvement director (17%); other senior hospital administrator (15%); or other hospital personnel (18%). Forty-two hospitals had an IC committee; 32 had antimicrobial restriction/control policies; and 21 had an antimicrobial restriction/control task force or committee. Components of antimicrobial restriction programs included infectious disease specialist approval, restricted formularies, selective susceptibility test reporting, and staff education programs. Many methods were used to detect infections, including microbiology laboratory reports (100%); record reviews (98%); informal reports from providers (90%); and readmission reviews (77%). CONCLUSIONS: Children's hospitals vary widely in how they design and implement their IC functions. These variations influence adverse event detection and nosocomial infection rate calculations. If medical errors, including nosocomial infections, are to be detected and hospital rates compared, standardized methods to collect, analyze, and report data are needed. The PPN has initiated activities to standardize surveillance and IC practices in participating hospitals.

Pediatric Prevention Network: a multicenter collaboration to improve health care outcomes.

Nosocomial infections and antimicrobial resistance are major causes of mortality and morbidity and have become a major public health focus. To date, most national and international nosocomial infection surveillance and prevention activities have been focused on adults, despite the fact that pediatric patients are at high risk for nosocomial infections because of their immature immune systems and prevalent device usage. In 1997 the Hospital Infections Program at the Centers for Disease Control and Prevention and the National Association of Children's Hospitals and Related Institutions partnered to establish a Pediatric Prevention Network. Infection control professionals and their hospital administrators at all children's hospitals were invited to participate. The objectives of the network are to establish baseline infection rates; design, implement, and evaluate prevention interventions; establish benchmark rates and best practices; and serve as a site for multicenter studies to improve outcomes for hospitalized children. This network serves as a model for quality improvement systems in health care.

Safety and immunogenicity of four doses of Neisseria meningitidis group C vaccine conjugated to CRM197 in United States infants.

BACKGROUND: Following widespread use of conjugate pneumococcal vaccine, Neisseria meningitidis likely will become the leading cause of bacterial sepsis and meningitis in US children. This report describes the safety and immunogenicity in US children of four consecutive doses of a meningococcal group C vaccine conjugated to CRM197 via reductive amination (MnCC). METHODS: One hundred six healthy 2-month-old infants received MnCC at 2, 4 and 6 months of age in a randomized, controlled double blind study; children in the other treatment arm were given a 7-valent conjugate pneumococcal vaccine. Parents reenrolled 64 of these children at 12 to 15 months to receive a fourth dose of MnCC. Routine childhood vaccines, including DTP, were coadministered. Temperatures and symptoms were recorded for 3 days after each immunization. Serum enzyme-linked immunosorbent assay IgG and bactericidal antibodies were measured prevaccination and before and 1 month after Doses 3 and 4. RESULTS: Moderate to severe local reactions, defined as erythema or induration > or =2.4 cm or pain that interfered with limb movement was reported after 0 to 3.2% of MnCC injections, depending on the reaction and dose. Fever occurred in 23 to 37% of children, but the contribution of MnCC to the febrile reactions is unknown. Geometric mean concentrations of IgG antibody to group C meningococcal polysaccharide were 3.72 microg/ml after Dose 3 and 8.03 microg/ml after the booster. Geometric mean functional serum bactericidal antibody titers after Doses 3 and 4 were 1:463 and 1:2341, respectively. One hundred percent of children had a serum bactericidal antibody titer of > or =1:64 after three doses and > or = 1:128 after the booster. CONCLUSIONS: The MnCC vaccine had an acceptable safety profile and generated high titers of bactericidal antibody in immunized US infants and toddlers. It appears to be an attractive candidate vaccine for the prevention of serogroup C meningococcal disease in young children.

The Internet: a practical example of the use of new technology in the assessment of vancomycin use in pediatrics. The Pediatric Prevention Network.

BACKGROUND: The rapid emergence of both new infections and new technologies has revolutionized health care during the past 50 years. Increased use of the Internet has enabled health care professionals to educate, interact, and collaborate throughout the world in ways never before possible. Increased use of vancomycin has been associated with the emergence of organisms with decreased susceptibility to vancomycin, such as Enterococcus and staphylococcal species. The purpose of this article is to describe our experience using Internet technology to assess vancomycin use at children's hospitals in the United States. METHODS: A Web-based evaluation was developed and distributed on the Internet to 57 Pediatric Prevention Network hospitals. The evaluation was structured to collect summary statistics on vancomycin use and admissions data by service for 1997 and 1998. RESULTS: Twenty-four hospitals were able to provide archived vancomycin use and patient admissions data; completed evaluations were returned from 15 hospitals (62.5% response rate). Personnel at 6 (40%) hospitals completed the evaluation directly on the Internet. CONCLUSIONS: In our study, Internet technology facilitated a more efficient evaluation of vancomycin use, but fewer than half of the personnel at Pediatric Prevention Network hospitals completed the evaluation directly on the Internet. It is unclear whether personnel at these hospitals were limited in Internet access, support, or understanding. Efforts should be directed to educate health care personnel on the advantages of the Internet. Furthermore, many of the pharmacy databases used in our assessment were not standardized across hospitals nor systematically validated. Understanding that limitations still remain-within the source of the data studied, the health care system sampled, and the Internet tools available-is essential because the Internet offers health care professionals today a tool both to protect patients and to improve quality throughout the world.

Vancomycin use in pediatric hematology-oncology patients.

Across-sectional study was performed of pediatric hematology-oncology patients who received vancomycin; use was compared to the Centers for Disease Control and Prevention (CDC) recommendations for vancomycin use. Thirty-seven patients received 308 doses of vancomycin. AR patients initially received vancomycin as empirical therapy; 100% of this use was not consistent with the CDC recommendations.

Antimicrobial use for pediatric upper respiratory infections: reported practice, actual practice, and parent beliefs.

BACKGROUND: In response to the dramatic emergence of resistant pneumococci, more judicious use of antibiotics has been advocated. Physician beliefs, their prescribing practices, and the attitudes of patients have been evaluated previously in separate studies. METHODS: This 3-part study included a statewide mailed survey, office chart reviews, and parent telephone interviews. We compared survey responses of 366 licensed pediatricians and family physicians in Georgia to recently published recommendations on diagnosis and treatment of upper respiratory infections (URIs). We further evaluated 25 randomly selected pediatricians from 119 surveyed in the Atlanta metropolitan area. For each, charts from the first 30 patients between the ages of 12 and 72 months seen on a randomly selected date were reviewed for encounters during the preceding year. A sample of parents from each practice were interviewed by telephone. RESULTS: In the survey, physicians agreed that overuse of antibiotics is a major factor contributing to the development of antibiotic resistance (97%), and that they should consider selective pressure for resistance in their decisions on providing antibiotic treatment for URIs in children in their practices (83%). However, many reported practices do not conform to the recently published principles for judicious antibiotic use. For example, 69% of physicians considered purulent rhinitis a diagnostic finding for sinusitis; 86% prescribed antibiotics for bronchitis regardless of the duration of cough; and 42% prescribed antibiotics for the common cold. Reported practices by family physicians were more often at odds with the published principles: they were significantly more likely than pediatricians to omit pneumatic otoscopy (46% vs 25%); to omit the requirement for prolonged symptoms to diagnose sinusitis (median 4 vs 10 days); and to omit laboratory testing for pharyngitis (27% vs 14%). Of the 7531 encounters analyzed in the chart review, 43% resulted in an antibiotic prescription, including 11% of checkups, 18% of telephone calls, and 72% of visits for URIs. There was wide variability in the overall antibiotic use rates among the 25 physicians (1-10 courses per child per year). There was an even wider variability in some diagnosis-specific rates; bronchitis and sinusitis in particular. Those with the highest antibiotic prescribing rates had up to 30% more return office visits. Physicians who prescribed antibiotics for purulent rhinitis were more likely to see parents who believed that their children should be evaluated for cold symptoms. CONCLUSIONS: Physicians recognize the problem of antibiotic resistance but their reported practices are not in line with recently published recommendations for most pediatric URIs. The actual prescribing practices of pediatricians are often considerably different from their close colleagues. Patient beliefs are correlated with their own physician's practices.

Vancomycin use in pediatric neurosurgery patients.

OBJECTIVE: The objective of this article is to describe a pediatric neurosurgery patient population receiving vancomycin and examine the indications for and appropriateness of vancomycin use. METHODS: A cross-sectional study was performed on the pediatric neurosurgery patients at Egleston Children's Hospital who received vancomycin from January 1 through December 31, 1996. Vancomycin use was compared with the Centers for Disease Control and Prevention Hospital Infection Control Practices Advisory Committee recommendations for vancomycin use. RESULTS: Thirty patients received 115 doses of vancomycin. The median patient age was 8.0 years, and 17 (56.7%) were male. Vancomycin was used for prophylaxis in 28 (93.3%) patients and empiric therapy in 3 (10.0%) patients; one patient received vancomycin for surgical prophylaxis followed by empiric therapy for suspected meningitis. Vancomycin prophylaxis was initiated after the incision in 6 (21.4%) patients and was continued as prophylaxis for more than one dose in 26 (92.9%) patients. CONCLUSIONS: Vancomycin was used primarily as surgical prophylaxis in pediatric neurosurgery patients, and use was not consistent with the Hospital Infection Control Practices Advisory Committee recommendations. These data suggest that for certain subpopulations, such as pediatric neurosurgery patients, there is a need for more specialized recommendations. Furthermore, prudent vancomycin use is warranted to successfully decrease the risk of further emergence of vancomycin resistance. Because vancomycin use may be prevalent in this population, assessment of vancomycin use in pediatric neurosurgery patients followed by establishment of vancomycin clinical guidelines may help improve the appropriateness of vancomycin use in this population.

Nonperinatal nosocomial transmission of Candida albicans in a neonatal intensive care unit: prospective study.

Nosocomial Candida albicans infections have become a major cause of morbidity and mortality in neonates in neonatal intensive care units (NICUs). To determine the possible modes of acquisition of C. albicans in hospitalized neonates, we conducted a prospective study at Grady Memorial Hospital, Atlanta, Ga. Clinical samples for fungal surveillance cultures were obtained at birth from infants (mouth, umbilicus, and groin) and their mothers (mouth and vagina) and were obtained from infants weekly until they were discharged. All infants were culture negative for C. albicans at birth. Six infants acquired C. albicans during their NICU stay. Thirty-four (53%) of 64 mothers were C. albicans positive (positive at the mouth, n = 26; positive at the vagina, n = 18; positive at both sites, n = 10) at the time of the infant's delivery. A total of 49 C. albicans isolates were analyzed by restriction endonuclease analysis and restriction fragment length polymorphism analysis by using genomic blots hybridized with the CARE-2 probe. Of the mothers positive for C. albicans, 3 of 10 were colonized with identical strains at two different body sites, whereas 7 of 10 harbored nonidentical strains at the two different body sites. Four of six infants who acquired C. albicans colonization in the NICU had C. albicans-positive mothers; specimens from all mother-infant pairs had different restriction endonuclease and CARE-2 hybridization profiles. One C. albicans-colonized infant developed candidemia; the colonizing and infecting strains had identical banding patterns. Our study indicates that nonperinatal nosocomial transmission of C. albicans is the predominant mode of acquisition by neonates in NICUs at this hospital; mothers may be colonized with multiple strains of C. albicans simultaneously; colonizing C. albicans strains can cause invasive disease in neonates; and molecular biology-based techniques are necessary to determine the epidemiologic relatedness of maternal and infant C. albicans isolates and to facilitate determination of the mode of transmission.

Decline of measles-specific immunoglobulin M antibodies after primary measles, mumps, and rubella vaccination.

Detection of measles-specific immunoglobulin M (IgM) has become the standard diagnostic method for laboratory confirmation of measles. In outbreaks, the interpretation of an IgM-positive result can be complicated when persons with suspected measles receive a dose of measles vaccine as part of outbreak control measures. This investigation evaluated the decay of measles-specific IgM antibodies 1 to 4 months after primary vaccination with measles, mumps, and rubella vaccine (MMRII). Serum samples were obtained from 536 infants vaccinated when they were 15 months old as part of a study to assess primary and secondary measles vaccine failure. Sixty serum specimens per week were selected from specimens collected between 4 and 9 weeks after MMRII vaccination; all 176 available serum specimens collected between 10 and > or = 16 weeks were included. Specimens were tested for the presence of measles-specific IgM by an antibody-capture enzyme immunoassay. The proportion of IgM-positive specimens dropped from 73% at 4 weeks after vaccination to 52% at 5 weeks after vaccination and then declined to 7% by 8 weeks after vaccination. Less than 10% of children remained IgM positive between 9 and 11 weeks. An IgM-negative result helps rule out the diagnosis of measles in a person with suspected infection and a history of recent vaccination. The interpretation of a positive IgM result from a person with a clinically suspected case of measles and a recent history of measles vaccination (especially within 8 weeks) is problematic, and the diagnosis of measles should be based on epidemiologic linkage to a confirmed case or on detection of wild-type measles virus.

Safety and immunogenicity of heptavalent pneumococcal vaccine conjugated to CRM197 in United States infants.

OBJECTIVE: To determine the safety and immunogenicity of heptavalent pneumococcal saccharide vaccine (serotypes 4, 6B, 9V, 14, 18C, 19F, 23F) individually conjugated to CRM197 (PNCRM7), administered at 2, 4, 6, and 12 to 15 months of age. DESIGN: Two hundred twelve healthy 2-month-old infants were equally randomized to receive four consecutive doses of PNCRM7 or an investigational meningococcal group C conjugate vaccine, which served as a control. Concomitantly administered routine vaccines were oral polio vaccine and combined diphtheria toxoid, tetanus toxoid, and whole cell pertussis vaccine/Haemophilus influenzae type b vaccine consisting of capsular oligosaccharides conjugated to CRM197 (DTP/HbOC) at 2, 4, and 6 months, and either measles-mumps-rubella vaccine or HbOC at 12 to 15 months. Active safety surveillance was conducted for 3 days after each dose. Antibody concentrations to each of the 7 pneumococcal serotypes were measured by enzyme-linked immunosorbent assay prevaccination, after doses two and three, prebooster, and postbooster. RESULTS: Significantly fewer children experienced local reactions at the PNCRM7 injection site than at the DTP/HbOC site. There was no increase in the incidence or severity of local reactions at the PNCRM7 site with increasing doses of vaccine. Mild to moderate postvaccination fever was common in both the PNCRM7 and control vaccine groups, however DTP/HbOC was administered concurrently. All 7 vaccine serotypes were immunogenic. The kinetics of the immune responses were serotype-specific. After three doses of PNCRM7, between 92% to 100% of children had >/=0.15 microg/mL of antibody, and 51% to 90% achieved a level of >/=1 microg/mL against specific serotypes. A booster dose of PNCRM7 resulted in a brisk anamnestic response to all 7 vaccine serotypes, demonstrating effective stimulation of T-cell memory by the primary series of vaccinations. CONCLUSION: Primary immunization followed by a booster dose of PNCRM7 seemed to be acceptably safe and resulted in significant rises in antibody to all 7 serotypes. Implications. Studies to assess vaccine efficacy of PNCRM7 for prevention of systemic disease, nasopharyngeal colonization, and acute otitis media are in progress. If PNCRM7 proves to be protective, there is the potential to prevent up to 85% of invasive pneumococcal disease occurring in US children.

Population biology, evolution, and immunology of vaccination and vaccination programs.

The purpose of prophylactic vaccination is to reduce morbidity and mortality in a population. Many questions related to the design of vaccines and vaccination programs require a population standpoint for their sharp formulation and laboratory and field studies to understand their immunologic background. Practical suggestions of the workshop included increased studies of age-specific immunity, better immunoepidemiologic surveillance, better design of efficacy studies, and more systematic sampling of parasite strains to study the evolutionary pressure exerted by vaccines. Theoretical immunology has much to contribute. One of the realizations of the workshop was the value of a strong interdisciplinary approach in vaccine development, utilizing relevant contributions from immunology, population biology, mathematical modeling, epidemiology, molecular biology, and virology.

Infant immunization with pneumococcal CRM197 vaccines: effect of saccharide size on immunogenicity and interactions with simultaneously administered vaccines.

Six pentavalent pneumococcal conjugate vaccines (Pn-CRM197) were evaluated among 400 infants. The vaccines differed in saccharide chain length (oligosaccharide [OS] or polysaccharide [PS]) and saccharide quantity (0.5, 2, or 5 microg). Subjects were randomized into groups 1-6 (Pn-CRM197 recipients) or 7 (controls) for immunization at 2, 4, and 6 months of age. Pn-CRM197 were well tolerated and elicited mean antibody concentrations that exceeded those in controls for all 5 capsular serotypes. PS formulations were generally more immunogenic than their OS counterparts. For PS vaccines, a dose-response was documented (5 microg > 2 microg > 0.5 microg), but the differences between the 5- and 2-microg formulations were insignificant. The mean anti-PRP antibody concentration was significantly higher among Pn-CRM197 recipients. It is concluded that PS vaccines are more immunogenic than OS vaccines. The improved immunogenicity from Haemophilus type b oligosaccharide conjugate (HbOC) vaccine when given with Pn-CRM197 suggests that a decreased dose of HbOC vaccine may be sufficient to elicit protection.

Standardization of an opsonophagocytic assay for the measurement of functional antibody activity against Streptococcus pneumoniae using differentiated HL-60 cells.

Host protection against pneumococcal disease i primarily mediated by phagocytosis. We developed and standardized an opsonophagocytic assay using HL-60 cells (human promyelocytic leukemia cells). Fifty-five serum samples were analyzed for the presence of functional antibody against seven pneumococcal serogroups or serotypes (4, 6B, 9V, 14, 18C, 19F, and 23F) by using differentiated HL-60 cells (granulocytes) and peripheral blood leukocytes (PBLs). Six of the 55 serum samples were from unvaccinated adult volunteers, 31 serum samples were from adults who received one dose of the 14-valent or the 23-valent polysaccharide vaccine, and 18 serum samples were from 16-month-old infants who received four doses of an investigational 7-valent polysaccharide-protein conjugate vaccine. The results of an opsonophagocytic assay with HL-60 cells correlated highly with those of an assay with PBLs as effector cells (median r for seven serotypes = 0.87: P < 0.01). Opsonophagocytic titers were compared with the immunoglobulin G antibody concentrations determined by enzyme-linked immunosorbent assay (ELISA). The r values for serogroups or serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F were 0.61, 0.60, 0.67 0.90, 0.61, 0.39, and 0.57, respectively, when HL-60 cells were used as effector cells and 0.56, 0.47, 0.61, 0.90, 0.71, 0.31, and 0.62, respectively, when PBLs were used. The assay requires small amounts of serum (40 microliters per serotype), making this test suitable for assaying infant sera. Culturable cells aid in assay standardization and likely reduce donor-to-donor variability. This standardized assay, in combination with the standardized ELISA, can be used to evaluate current and developing pneumococcal vaccines, in which functional opsonophagocytic antibody activity may correlate with protection against pneumococcal disease.