Detection of IgA and IgG but not IgE antibody to respiratory syncytial virus in nasal washes and sera from infants with wheezing

BACKGROUND AND OBJECTIVE: The capacity of respiratory syncytial virus (RSV) to stimulate an IgE antibody response and enhance the development of atopy and asthma remains controversial. Nasal washes and sera from 40 infants (20 with wheezing, 9 with rhinitis, and 11 without respiratory tract symptoms) were obtained to measure IgE, IgA, and IgG antibody to the immunodominant, F and G, virion proteins from RSV. STUDY DESIGN: Children (aged 6 weeks to 2 years) were enrolled in the emergency department during the mid-winter months and seen at follow-up when they were asymptomatic. All nasal washes were tested for RSV antigen. Determinations of antibody isotypes (IgE, IgA, and IgG) to RSV antigens were done in nasal washes and sera by using an enzyme-linked immunosorbent assay. In a subset of nasal washes, IgE to RSV was also evaluated by using a monoclonal anti-F(c)E antibody-based assay. RESULTS: Fifteen patients with wheezing, two with rhinitis, and one control subject tested positive for RSV antigen at enrollment. Thirteen patients with wheezing were <6 months old, and most (77%) were experiencing their first attack. Among the children with positive test results for RSV antigen, an increase in both nasal wash and serum IgA antibody to RSV-F(a) and G(a) was observed at the follow-up visit. However, there was no evidence for an IgE antibody response to either antigen. CONCLUSION: Both IgA and IgG antibodies to the immunodominant RSV-F(a) and G(a) antigens were readily detected in the nasal washes and sera from patients in this study. We were unable to demonstrate specific IgE antibody to these antigens and conclude that the production of IgE as a manifestation of a T(H)2 lymphocyte response to RSV is unlikely.     

Undetectable IgE responses after respiratory syncytial virus infection.

Sequential nasopharyngeal secretions were collected from 81 infants from one day to three months after admission to hospital with respiratory syncytial virus (RSV) infection. Samples from 21 infants were assayed for anti-RSV IgE in an antigen capture ELISA assay. No IgE antibodies were detected although an assay of IgA antibodies carried out in parallel by a similar technique detected IgA antibodies in the secretions of all patients tested. Neither prior absorption of IgA or IgG, concentration of the secretions by freeze drying, nor enzyme amplification of the assay revealed any virus specific IgE. Using an antibody capture ELISA with a sensitivity of 0.85 IU/ml, IgE could be detected in sequential secretions of only one of the 81 RSV infected infants studied. Further testing of the secretions from 12 of these patients and those of a further 15 using an enzyme amplified assay with a sensitivity of 0.1 IU/ml revealed no further positives. Low concentrations of IgE were found in the sera of the majority of infants with RSV infection but they did not differ from those of virus negative children of a similar age collected between RSV epidemics. No rise in mean serum IgE concentrations between acute and convalescent samples was observed. No virus specific IgE was detected in the sera of any infant using the enzyme amplified antigen capture ELISA.     

Undetectable IgE responses after respiratory syncytial virus infection

Sequential nasopharyngeal secretions were collected from 81 infants from one day to three months after admission to hospital with respiratory syncytial virus (RSV) infection. Samples from 21 infants were assayed for anti-RSV IgE in an antigen capture ELISA assay. No IgE antibodies were detected although an assay of IgA antibodies carried out in parallel by a similar technique detected IgA antibodies in the secretions of all patients tested. Neither prior absorption of IgA or IgG, concentration of the secretions by freeze drying, nor enzyme amplification of the assay revealed any virus specific IgE. Using an antibody capture ELISA with a sensitivity of 0.85 IU/ml, IgE could be detected in sequential secretions of only one of the 81 RSV infected infants studied. Further testing of the secretions from 12 of these patients and those of a further 15 using an enzyme amplified assay with a sensitivity of 0.1 IU/ml revealed no further positives. Low concentrations of IgE were found in the sera of the majority of infants with RSV infection but they did not differ from those of virus negative children of a similar age collected between RSV epidemics. No rise in mean serum IgE concentrations between acute and convalescent samples was observed. No virus specific IgE was detected in the sera of any infant using the enzyme amplified antigen capture ELISA.     

Association between pronounced IgA response in RSV bronchiolitis and development of allergic sensitization

Forty-five children who had heen hospitalized with bronchiolitis caused by respiratory syncytial virus (RSV) at a mean age of 4 months, and 90 matched control children, were tested for occurrence of RSV antibodies at one year of age. Of the children who had suffered from bronchiolitis. forty had demonstrable IgG antibodies, whereas the remaining five only had IgA antibodies against RSV. In the control group. 42% were RSV seropositive. The anti-RSV IgA antibody titres tended to be higher in patients with bronchiolitis ihan in controls and a larger proportion of the seropositive children in the former than in the latter group had demonstrable IgG antibodies. These fmdings suggest that RSV infections causing bronchiolitis are more often associated with a strong antibody response than are mild cases of the infection.
Follow-up of the children at 3 years of age showed that allergic sensitization and development of asthma had occurred much more frequently in children with past RSV bronchiolitis than in controls. Children with past RSV bronchiolitis who later developed allergic sensitization had elevated RSV IgA antibody titres at one year of age more frequently than children with past RSV-bronchiolitis. who were not sensitized (p=0.015). No significant differences regarding IgG antibody titres were observed. Since IgA, similarly a. s IgE. antibody formation is strongly Th2 cell dependent, the results are compatible with other fmdings suggesting that RSV has an unusual propensity to activate the Th2 cell system. This may contribute to the pathological picture of bronchiolitis in small children and at the same lime render the infected child predisposed for later development of allergic sensitization. RSV bronchiolitis may thus be an important risk factor for later development of atopic disease although it cannot be excluded that the bronchiolitis simply serves as a marker that predicts later development of atopy.     

Serum and salivary antibody responses to non-capsular Haemophilus influenzae antigens in children with meningitis and epiglottitis

Serum IgG, IgA and IgM antibody and salivary IgA antibody concentrations to non-capsular Haemophilus influenzae antigens were measured in 13 children with H. influenzae type b meningitis and in 15 children with epiglottitis. Most had detectable serum IgG and IgM antibody at presentation but significantly fewer patients with meningitis had serum IgA antibody at presentation ( P <0.05). Serum antibody concentrations had risen significantly by 3 weeks after presentation in patients with epiglottitis only. Convalescent serum IgG antibody concentrations against these antigens were higher in younger children with epiglottitis.
Salivary IgA antibody to H. influenzae was detectable at presentation in all children with epiglottitis and in 12 of 13 with meningitis. Salivary antibody concentrations did not differ significantly between the two patient groups at presentation, although patients with meningitis had higher salivary IgA antibody concentrations than 10 children of similar age with bronchiolitis ( P <0.02). There was no association between the presence of salivary antibody and low concentrations of convalescent serum antibody.
The rise in convalescent serum antibody concentrations to non-capsular H. influenzae antigens only in children with epiglottitis is similar to findings for antibody to capsular polysaccharide. However, this rise was greater for IgG in younger patients, and the low titre of convalescent serum antibody in patients with meningitis was not associated with higher titres of IgA antibody in secretions as described by others for polysaccharide antibody. These findings suggest that the poor serum antibody response to these antigens in patients with meningitis is independent of age and is not due to mucosal induction of systemic tolerance.     

The role of neutralizing antibodies in protection of American Indian infants against respiratory syncytial virus disease

BACKGROUND: Navajo and White Mountain Apache infants have respiratory syncytial virus (RSV) hospitalization rates 2-5 times that of the general U.S. infant population. To evaluate whether these high rates can be attributable to low concentrations of maternally derived RSV neutralizing antibodies, we conducted a case-control study. METHODS: Study subjects enrolled in a prospective, hospital-based surveillance study of RSV disease and a group randomized clinical trial of a 7-valent pneumococcal conjugate vaccine. Cord blood specimens were assayed for neutralizing RSV antibody titers. Infants hospitalized with a respiratory illness had a nasal aspirate obtained to determine whether RSV was present. Infants with an RSV respiratory hospitalization were matched by date of birth and geographic location to infants who did not have an RSV hospitalization before 6 months of age. RESULTS: For every 1 log2 increase in titer of cord blood RSV neutralizing antibodies there was a 30% reduced risk of hospitalization with RSV (OR = 0.69, P = 0.003). However, among infants hospitalized with RSV, there was no association between cord blood RSV neutralizing antibody and the severity of the RSV illness. CONCLUSIONS: These findings indicate that American Indian infants with high concentrations of maternally derived RSV neutralizing antibodies are protected from RSV hospitalization before 6 months of age. However, these antibodies do not modify the severity of illness once disease has occurred. The basis for elevated rates of RSV disease among American Indian infants cannot be attributed to a failure of maternal RSV neutralizing antibodies to confer protection.     

Neutralizing activity in human milk fractions against respiratory syncytial virus

Neutralizing activity against respiratory syncytial virus (RSV) was measured in milk samples from 17 healthy women whose infants had an acute infection with respiratory syncytial virus (RSV) and from 27 women with healthy infants. All milk samples were obtained 2-8 months post partum. Neutralizing activity was detected in 36 samples. No major difference in neutralizing titers was observed between the two groups, and the titers were low. RSV-specific IgA was found in two samples, and RSV-specific IgG in one sample. RSV-specific IgM was not detected. In gel filtration studies, the neutralizing activity was eluted with an apparent molecular weight above 400,000. The neutralizing activity remained after removal of IgA by affinity chromatography. These findings suggest that both immunoglobulin and non-immunoglobulin components in human milk can neutralize RSV.     

Respiratory syncytial virus outbreak on American Samoa. Evaluation of risk factors

Acute respiratory illness is one of the leading causes of childhood mortality in developing nations. We investigated an increase in hospitalizations of children less than 2 years old for severe lower respiratory tract illness (LRI) from October 1986 through December 1986 on the island of American Samoa. Hospitalization rates were highest in children less than 6 months of age (60 of 1000 compared with 22 of 1000 for those 6 to 11 months of age, and seven of 1000 for those 12 to 24 months of age). The outbreak was more severe than in previous years, with ten (19%) of 54 patients admitted to the intensive care unit (ICU) compared with three (7%) of 42 and one (3%) of 40 during the same months of 1985 and 1984. Two patients died. Most patients had clinical bronchiolitis; of 34 patients tested, serologic or nasal aspirate evidence of recent respiratory syncytial virus (RSV) infection was found in 18 (53%). A study of patients younger than 1 year of age demonstrated that patients hospitalized with LRI were more likely to have a household member who smoked cigarettes (18/20, 90%) than outpatient controls without recent respiratory illness (8/15, 53%). Maternal sera obtained between December 1985 and October 1986 showed no protective effect of either detectable IgG or neutralizing antibody to two major groups of RSV. Our study documents the involvement of RSV in an outbreak of severe LRI among infants in a tropical area and further suggests that exposure to cigarette smoke is a risk factor for LRI infants.     

Serum and salivary antibody responses to non-capsular Haemophilus influenzae antigens in children with meningitis and epiglottitis

Serum IgG, IgA and IgM antibody and salivary IgA antibody concentrations to non-capsular Haemophilus influenzae antigens were measured in 13 children with H. influenzae type b meningitis and in 15 children with epiglottitis. Most had detectable serum IgG and IgM antibody at presentation but significantly fewer patients with meningitis had serum IgA antibody at presentation (P less than 0.05). Serum antibody concentrations had risen significantly by 3 weeks after presentation in patients with epiglottitis only. Convalescent serum IgG antibody concentrations against these antigens were higher in younger children with epiglottitis. Salivary IgA antibody to H. influenzae was detectable at presentation in all children with epiglottitis and in 12 of 13 with meningitis. Salivary antibody concentrations did not differ significantly between the two patient groups at presentation, although patients with meningitis had higher salivary IgA antibody concentrations than 10 children of similar age with bronchiolitis (P less than 0.02). There was no association between the presence of salivary antibody and low concentrations of convalescent serum antibody. The rise in convalescent serum antibody concentrations to non-capsular H. influenzae antigens only in children with epiglottitis is similar to findings for antibody to capsular polysaccharide. However, this rise was greater for IgG in younger patients, and the low titre of convalescent serum antibody in patients with meningitis was not associated with higher titres of IgA antibody in secretions as described by others for polysaccharide antibody. These findings suggest that the poor serum antibody response to these antigens in patients with meningitis is independent of age and is not due to mucosal induction of systemic tolerance.(ABSTRACT TRUNCATED AT 250 WORDS)     

Maternally transferred neutralising dengue antibodies in Thai infants: a pilot study

In a dengue-endemic area, sera from 42 mother-infant pairs and sera collected from the infants at follow-up at the ages of 3 months (n =27), 6 months (n =34), 9 months (n =23) and 12 months (n =8) were tested for antibodies to four dengue serotypes using a plaque reduction neutralisation test (PRNT(50)), IgG ELISA and haemagglutination inhibition assay (HAI). The IgG ELISA and HAI tests were less sensitive than PRNT(50) in detecting low levels of antibodies. Levels of maternally transferred dengue neutralising antibodies in the cord sera were very high and identical to those in the mothers. Neutralising antibody prevalences in the newborns were 95% to dengue serotype 1 (DEN-1), 93% to DEN-2 and DEN-3 and 91% to DEN-4. The antibodies decreased with increasing age. At least one dengue serotype neutralising antibody persisted in the infants at ages 3, 6 and 9 months in 92%, 69% and 13%, respectively. No maternally transferred antibody was observed in 12-month-old infants. In endemic areas therefore, where most infants have maternally transferred dengue antibodies, interference with dengue vaccine is likely to be less after 12 months of age than before then.     

IgG and IgG subclass specific antibody responses to diphtheria and tetanus toxoids in newborns and infants given DTP immunization

To evaluate immune responses to diphtheria and tetanus toxoids in infants we used enzyme-linked immunosorbent assays to detect total IgG and specific IgG-1, IgG-2, IgG-3, and IgG-4 antibody. One group of infants received a newborn dose and subsequently received the usual three doses of DTP. A second group of infants received only the routine dosage at 2, 4, and 6 months of age. In sera acquired at birth, 6, and 9 months of age, there were no statistically significant differences between the two vaccine groups in IgG antibody responses to diphtheria or tetanus, or in IgG subclass tetanus-specific antibody responses. In individual children, tetanus-specific subclass responses were similar in pattern to that for total IgG tetanus antibody, i.e. each IgG subclass response appeared to be regulated by similar mechanisms in that child, but the regulation differed between children. In contrast to a prior study of pertussis immunity, maternally acquired antibody did not significantly affect immune responses to diphtheria or tetanus toxoid by 9 months of age. There was no discernible tolerance due to early tetanus or diphtheria immunization or to high levels of maternally acquired antibody.     

Mucosal immune responses to meningococcal conjugate polysaccharide vaccines in infants

BACKGROUND: Serogroup C meningococcal conjugate polysaccharide vaccines have been reported to induce significant serum IgG antibodies and immunologic memory in infants. Because meningococcus is a mucosal pathogen colonizing the nasopharynx, local mucosal immune responses may play an important role in host defense against infection and carriage. We have investigated the mucosal IgA and IgG antibody responses to two meningococcal C conjugate vaccines in the saliva of healthy infants. METHODS: Specific salivary IgA and IgG antibodies to two meningococcal C polysaccharide conjugate vaccines (Menjugate from Chiron Corp., n = 46; and Meningitec from Wyeth Lederle, n = 54) were investigated by immunoassay in infants after parenteral vaccinations at the ages of 2, 3 and 4 months. Unstimulated saliva samples were collected immediately before the first immunization and 1 month after the third immunizations. Forty healthy infants receiving the same routine vaccines but no meningococcal C vaccine were recruited as controls. RESULTS: There were significant increases in meningococcal C polysaccharide-specific IgG antibody concentrations postvaccination compared with prevaccination concentrations in both vaccinated groups (both P < 0.001), but no change in the control group. There were no significant increases in specific IgA postvaccination geometric mean concentrations in either the vaccine or the control groups. The number of IgA positives postvaccination increased slightly in the Wyeth vaccine group vs. controls (P < 0.05). CONCLUSIONS: Significant salivary IgG antibodies to meningococcal C polysaccharide were observed after parenteral immunization with two meningococcal C conjugate vaccines, whereas there was no significant increase in specific IgA antibody levels for these two vaccines.     

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.     

Impact of respiratory syncytial virus immune globulin in 1996-1997: a local controlled comparison.

BACKGROUND: Immune globulin containing high titers of neutralizing antibodies specific for respiratory syncytial virus (RSV) is clinically used to prevent hospitalizations for RSV-related respiratory infections among high-risk infants. However, recommendations regarding which patient populations should receive RSV immune globulin are inconsistent. OBJECTIVE: To compare hospitalization rates for prematurely born infants with and without chronic lung disease who received RSV immune globulin with similar infants whose parents refused such treatment during the 1996-1997 winter season. DESIGN: Inception cohort study. PARTICIPANTS: Infants born at less than 35 weeks' gestation and less than 6 months old without lung disease and children who had been born prematurely, had chronic respiratory disease, and were less than 2 years old at the onset of the RSV season. MAIN OUTCOME MEASURE: Hospitalization for an RSV-related respiratory illness. RESULTS: Seventy-six infants (66 [87%] with chronic lung disease and 10 [13%] born prematurely without lung disease) received RSV immune globulin; 65 infants (18 [28%] with chronic lung disease and 47 [72%] born prematurely without lung disease) did not. Three (4%) of the treated group and 2 (3%) of the untreated group were hospitalized for RSV infections. Of those with chronic lung disease, 5% (3/66) of those treated with RSV immune globulin were hospitalized, compared with 11% (2/18) of those untreated. Of those born prematurely without lung disease, no infant in the treated (0/10) or untreated (0/47) group was hospitalized. CONCLUSIONS: The risk of hospitalization of infants born prematurely who are younger than 6 months without lung disease is low. Current recommendations for preventing RSV illness in this group by using RSV immune globulin may require inclusion of more specific clinical characteristics rather than gestational age alone.     

Mucosal IgA, mucosal cow's milk antibodies, serum cow's milk antibodies and gastrointestinal permeability in infants

We have studied development of the levels of IgA cow's milk (CM) antibodies in the saliva, faeces and serum of 20 term and 20 preterm infants from birth to 8 months. All infants already had IgA in their saliva during the first week of life. The levels peaked at the age of one month, thereafter decreasing in both groups; from the age of three months levels remained stable. Term infants had higher levels than preterm infants, but no differences were found between breastfed and CM-fed infants. Breastfed infants had higher levels of IgA in their faeces than did CM-fed infants; the IgA levels were similar in breast-fed term and preterm infants, being highest at birth, and decreasing thereafter. We also showed rising titers of serum IgA CM antibodies, with higher levels in infants regularly exposed to CM than in breast-fed infants. We sought associations between the magnitude of intestinal permeability to human a-lactalbumin (ALA) measured at the ages of 4-7 days and one month and the levels of IgG antibodies to CM, but no such relation was found.;     

IgG and IgM antibodies to viral glycoproteins in respiratory syncytial virus infections of graded severity.

Serum antibodies to the fusion (F) and large glycoprotein (G) of respiratory syncytial virus in the serum of 57 infected infants were measured by enzyme linked immunosorbent assay (ELISA). Most serum samples taken at the time of admission to hospital contained antibodies to both glycoproteins, and overall there was no significant evidence of a selective deficiency of antibody to either viral antigen. Less than a quarter of the infants showed rising IgG antibody titres to either glycoprotein after infection, whereas over threequarters produced an IgM response. There was a significant correlation between IgG response to viral glycoproteins and the age of the infant. The correlation of age with the IgM response was less pronounced, and there was no correlation between serum IgG antibody derived transplancentally in the acute phase of infection and IgM response to either glycoprotein. Neither IgG or IgM responses correlated with a clinical assessment of the severity of infection in the infants. IgM responses, however, were weakly correlated with reduced secretion of infectious virus in the upper respiratory tract.     

The progression of maternal RSV antibodies in the offspring.

The concentrations of maternal anti-RSV IgG antibodies were followed in 49 healthy newborns over the first six months of life. At birth, 41 mothers (83%) tested positive for anti-RSV IgG and all of their babies carried maternal anti-RSV IgG. Anti-RSV IgG positivity dropped to 73% at 1 month, 6% at 3 months, and 2% at 6 months. Between 3 and 6 months, 8% did acquire RSV infection, half of them as acute bronchiolitis and half as non-specific respiratory infection. All of the patients who acquired clinical RSV disease had an antibody concentration of <20 RU/ml which may be the cut off value for protection.     

The progression of maternal RSV antibodies in the offspring

The concentrations of maternal anti-RSV IgG antibodies were followed in 49 healthy newborns over the first six months of life. At birth, 41 mothers (83%) tested positive for anti-RSV IgG and all of their babies carried maternal anti-RSV IgG. Anti-RSV IgG positivity dropped to 73% at 1 month, 6% at 3 months, and 2% at 6 months. Between 3 and 6 months, 8% did acquire RSV infection, half of them as acute bronchiolitis and half as non-specific respiratory infection. All of the patients who acquired clinical RSV disease had an antibody concentration of <20 RU/ml which may be the cut off value for protection.     

Age-related difference in immune responses to respiratory syncytial virus infection in young children

There have been longitudinal studies of the developmental change of the immune system during the first year of life. The aim of this study was to investigate if there is any age-related difference in cytokine responses to respiratory syncytial virus (RSV) infection between the patients under 6 months of age and the patients over 12 months of age compared with age-matched controls. Forty-five children < or =24 months of age who were admitted with acute RSV bronchiolitis were enrolled. The patients were divided into two groups: the infants < or =6 months old and the young children > or =12 months old. Immune response to RSV infection was determined by measuring the serum concentrations of cytokines and compared with age-matched controls. Serum samples were obtained on admission and analyzed for interferon (IFN)-gamma, interleukins (IL)-10, -13, and -4 using ELISA. Comparing the cytokine levels of two control groups, both IFN-gamma and IL-13 were lower in the children > or =12 months of age than in the infants < or =6 months of age. IL-10 and IL-4 showed no significant changes with age. Comparing with age-matched controls, IFN-gamma levels were significantly higher in RSV group > or =12 months of age, but showed a tendency toward lower levels in RSV group < or =6 months of age. Both IL-10 and IL-13 levels were significantly higher in RSV group > or =12 months of age, but showed no significant difference in RSV group < or =6 months of age. Our study demonstrated a significant age-related difference in immune response to RSV infection during early life. It suggests that the developmental changes in cytokine responses to RSV infection may be considered in the control of RSV bronchiolitis in young children.     

Transplacentally acquired immunoglobulin G antibodies against measles, mumps, rubella and varicella-zoster virus in preterm and full term newborns

IgG antibody values against measles, mumps, rubella and varicella-zoster virus in 71 full term and 101 preterm infants and their 152 mothers and the decay of maternally acquired antibodies during infancy were studied. Both magnitude of transplacental antibody passage and cord blood antibody values correlated with gestational age. After 6 months preterm infants born before 32 weeks of gestation had lost maternal antibodies.