Measurement of immunoglobulin A, G, and M class rotavirus antibodies in serum and mucosal secretions

Antibody secreting B cells and plasma antibody response to rotavirus vaccination in infants from Kolkata India

Background

Assessing immune response after rotavirus vaccination consists in measuring serum or plasma IgA and IgG antibodies, but these assays provide very little information about the mucosal immune response. Thus the development of assays for detection of mucosal immune response following rotavirus vaccination is essential. We evaluate to assess circulating antibody-secreting cells (ASCs) as a potential means to evaluate mucosal immune responses to rotavirus vaccine.

Methods

372 subjects, aged 6 weeks, were enrolled in the study. All the subjects were assigned to receive two doses of Rotarix^® vaccine. Using a micro-modified whole blood-based ELISPOT assay, circulating rotavirus type-specific IgA- and IgG-ASCs, including gut homing β7+ ASCs, were enumerated on week 6 before the first dose of Rotarix vaccination at 7 weeks of age and week 18 after the second vaccination at 17 weeks of age. Plasma samples collected before vaccination, and after two doses of Rotarix^® vaccination were tested for plasma rotavirus IgA titers.

Results

Two doses of Rotarix^® provided to induce sero-protective titer of ≥ 20 Units in 35% of subjects. Total blood IgA- ASC responses were detected in 26.4% of subjects who were non-responder before vaccination. Among responders, 47% of the subjects also have sero-protective plasma IgA titers.

Discussion

Our results suggest that virus-specific blood gut homing ASCs were detected and provide insight into mucosal immune response after rotavirus vaccination. Further studies are needed to evaluate the duration of such immune responses and to assess the programmatic utility of this whole blood-based mucosal ASC testing for the rotavirus immunization program.

Rotavirus-neutralizing antibodies inhibit virus binding to integrins alpha 2 beta 1 and alpha 4 beta 1

Rotavirus outer capsid proteins VP5(*), VP8(*) and VP7 elicit neutralizing, protective antibodies. The alpha 2 beta 1 integrin is a cellular receptor for rotavirus that is bound by VP5(*). Some rotaviruses also recognize the alpha 4 beta 1 integrin. In this study, the effects of antibodies to rotavirus on virus binding to recombinant alpha 2 beta 1 and alpha 4 beta 1 expressed on K562 cells were determined. All neutralizing monoclonal antibodies to VP5(*) tested (YO-2C2, 2G4, 1A10) and two to VP7 (RV-3:2, RV-4:2) inhibited rotavirus binding to alpha 2 beta 1. Rotavirus binding to alpha 4 beta 1 was reduced by 2G4 and neutralizing antibody F45:2, directed to VP7. However, a neutralizing antibody to VP8(*) (RV-5:2) and one to VP7 (RV-3:1) did not affect rotavirus binding to these integrins. Virus-cell binding was unaffected by non-neutralizing antibody RVA to the rotavirus inner capsid protein VP6. The attachment of human rotavirus strain Wa to these integrins was inhibited by infection sera with neutralizing activity collected from two children hospitalised with severe rotavirus gastroenteritis. A negative reference serum did not affect rotavirus-cell attachment. As the binding of rotaviruses to alpha 2 beta 1 and alpha 4 beta 1 is inhibited by neutralizing antibodies to VP5(*) and VP7, and serum from children with rotavirus disease, rotavirus recognition of these integrins may be important for host infection.

Technical report: results of immunological tests on faecal extracts are likely to be extremely misleading

Clinical investigation of gut immunity is difficult because of the need to study intestinal tissues or secretions directly. Others have reported that immunoglobulins, antibodies and cytokines can be detected in saline extracts of faeces. We have assessed the validity of this approach by measuring immunoglobulins, albumin, alpha 1-antitrypsin and isotype-specific antibodies in matched samples of faeces and whole gut lavage fluid. Results were compared as estimated output per day, and by using haemoglobin as a common reference substance. Samples were obtained from 10 patients with active inflammatory bowel disease and 10 with other benign GI diseases. For immunoglobulins, albumin and antibodies, the amount detected in faeces varied from < 0.01% to 35.5% (based on estimated daily output) and < 0.01% to 18.5% (based on haemoglobin) of the amount known to be produced in the gut from results of assays on whole gut lavage fluid (WGLF); there were significantly higher rates of recovery in faecal specimens from patients with active gut inflammation than from other patients. Detection rates and titres of specific antibody in faeces were even lower than those for immunoreactive IgA. These data indicate that immunological tests on saline extracts of faeces do not represent the true status of the gut humoral immune system, and such studies should be strongly discouraged.

Immunodiagnosis of dracunculiasis by dot-ELISA

A dot-enzyme-linked immunosorbent assay (dot-ELISA) using soluble adult-guineaworm antigen was developed for immunodiagnosis of Dracunculus medinensis infection. The test was found to be specific and sensitive when compared with ELISA. The dot-ELISA described here was found to be time-saving and easy to perform, and its possible use as a diagnostic and epidemiological tool under field conditions is therefore discussed.

A longitudinal study of rotavirus antibody titers in swine in a closed specific pathogen-free herd

In a newly established closed specific pathogen-free (SPF) swine herd, gilt/sow suckling and weaned pig rotavirus specific antibody titers were followed for three lactations by enzyme-linked immunosorbent assay (ELISA) to gain insight into the dynamics of herd antibody titers to group A rotavirus. Among gilts/sows, serum antirotavirus IgG titers increased during each lactation with a subsequent drop in titer between farrowings. Serum antirotavirus IgM titers declined during each lactation and with subsequent parity. Serum antirotavirus IgA titers remained constant during lactations and among parities. In colostrum and milk, antirotavirus IgA antibody was abundant. Differences in titer were not noticed between gilts and second litter sows but third litter sows had significantly higher titers than the first two groups. Antirotavirus IgG was high in colostrum but nearly nonexistent in milk. This titer did not vary significantly within or among parities. There was a linear regression in the titers of baby pig serum antirotavirus IgG from the post colostral sample through to seven weeks old, after which titer began to increase. No difference in baby pig serum antirotavirus IgG was noted among the three litters. Serum antirotavirus IgA and IgM were undetectable in baby pig sera after 2-3 weeks of age. Coproantibody to rotavirus was sporadically present in pig feces for 2-3 weeks after birth with highest titers in the IgA fraction. We conclude that although it is probable that age resistance of pigs to rotavirus diarrhea occurs, humoral immunity as measured by ELISA rotavirus antibody titers may not be intimately involved in virus clearance since in our studies baby pigs passively received large amounts of antibody but still excreted pathogenic virus. The finding of increasing levels of serum antirotavirus IgG in gilt/sow serum suggest that exposure to antigen of dams occur without significant increases in antirotavirus IgG titers in either colostrum, milk, or baby pig serum.

Homotypic and heterotypic serum and milk antibody to rotavirus in normal, infected and vaccinated horses

The homotypic and heterotypic antibody response to rotavirus was determined in three pony mares and their foals. The normal concentrations of anti-rotavirus antibodies in mares' milk and mares' and foals' serum over the first 10 weeks post-partum were measured using IgA, IgG and rotavirus serotype-specific enzyme linked immunosorbent assays. Experimental infection of the foals with serotype 3 equine rotavirus produced a rapid, serotype-specific response which peaked 10 days after infection and a slower heterotypic response which peaked 32 days later. In contrast, vaccination of the mares with an inactivated, adjuvanted serotype 6 bovine rotavirus produced a heterotypic response similar to that of the homotypic response in both serum and milk, although the predominant response in serum was IgG, while in milk it was IgA. These results suggest that non serotype-restricted passive protection of foals against rotavirus may be achieved by parenteral vaccination of mares.

Comparison of rotavirus immunoglobulin A coproconversion with other indices of rotavirus infection in a longitudinal study in childhood

In order to determine the sensitivity and reliability of antirotaviral fecal immunoglobulin A (IgA) as an indicator of rotavirus reinfection, the antibody responses to rotavirus of 44 infants with severe rotavirus gastroenteritis recruited on admission to a hospital were studied. Feces were collected daily during hospitalization and weekly thereafter, and sera were obtained every 4 months, for 6 to 32 months (median, 17 months). Antirotaviral IgG, IgA, and IgM were measured by enzyme immunoassay in all samples. Rotavirus antigen, rotavirus-neutralizing antibody, and total IgA were measured in feces. The results showed that use of an IgA index (ratio of specific IgA to total IgA) was unnecessary to identify copro-IgA conversion to rotavirus. The other markers of rotavirus infection tested showed a high level of predictive accuracy of coproconversion in rotavirus-neutralizing antibody. Copro-IgM, serum IgM, and virus in feces were insensitive measures of neutralizing antibody coproconversion. Seroconversion in IgG or IgA was detected in 46% of neutralizing coproconversions. The most sensitive marker, present in 92% of neutralizing coproconversions, was antirotaviral fecal IgA conversion. This correlation of fecal IgA with fecal neutralizing antibody suggests that coproconversions in IgA represent true elevations in antirotaviral IgA with neutralizing capacity. A coproconversion in IgA appears to indicate genuine rotavirus infection. Copro-IgA conversions in feces collected weekly are likely to be more sensitive markers of rotavirus reinfection than are seroconversion and virus detection combined in epidemiological studies of acute diarrhea in children and in rotavirus vaccine trials.

Comparison of immunoglobulin A (IgA), IgG, and IgM enzyme-linked immunosorbent assays, plaque reduction neutralization assay, and complement fixation in detecting seroresponses to rotavirus vaccine candidates

In a phase 1 study to evaluate human-rhesus rotavirus reassortant vaccines, 116 infants 1 to 5 months of age received one of the following five preparations: the serotype 1 reassortant, the serotype 2 reassortant, rhesus rotavirus (serotype 3), a bivalent preparation (serotypes 1 and 3), or a placebo. Seroresponses to the different vaccines were measured by plaque reduction neutralization assay (PRNA); rotavirus-specific immunoglobulin A (IgA), IgG, and IgM enzyme-linked immunosorbent assays (ELISAs); and complement fixation (CF). The seroresponse rate, calculated by using a fourfold or greater antibody rise by any assay, was similar in the four vaccine groups (83 to 96%). When the data from all the vaccinees were pooled, IgA ELISA, IgG ELISA, and PRNA were comparable in detecting seroresponses (67, 62, and 70%, respectively) and more efficient than IgM ELISA (53%) and CF (44%). When the vaccinees were analyzed by age, the overall seroresponse rates were the same for infants 1 to 2 and 3 to 5 months old (90%). The IgA ELISA and PRNA were the most efficient for detecting antibody rises in both age groups. IgG ELISA was among the least efficient methods for detecting antibody rises in the younger age group but among the most efficient in the older age group (44 versus 78%). CF was among the least efficient methods in both age groups but was significantly better in the older age group than in the younger age group (54 versus 21%). Our findings show that ELISA, in particular rotavirus-specific IgA ELISA, is a sensitive indicator of vaccine takes in 1- to 5 month-old infants, the target population for vaccination. ELISA should also be very useful in demonstrating natural rotavirus infections in field studies in which a stool specimen from a diarrheal episode is not always available. The ELISA has the advantages of being easier and quicker and requiring less serum than PRNA, but it does not give serotype-specific information about the immune response.

Evaluation of end-point titration, single dilution and capture enzyme immunoassays for measurement of antirotaviral IgA and IgM in infantile secretions and serum

In order to facilitate measurement of antirotaviral IgA in large collections of faeces and secretions, adaptations of enzyme immunoassay methods for estimating antirotaviral IgA and IgM in duodenal fluid, saliva, faeces and serum were studied. To quantitate specific IgA, a single dilution of each sample was assayed. Results were expressed as antirotaviral IgA units derived from a standard curve. Units were calculated by log-logit analysis on computer. There was strong correlation between antirotaviral IgA units and end-point titres in 257 faecal samples (correlation coefficient r = 0.92) and in 182 duodenal fluids and salivary samples (correlation coefficient r = 0.74). The assay was validated using acute and convalescent faeces from children with or without rotavirus infection. Immune conversions in IgA were detected in 33 (75%) of the children by units and 34 (77%) by titres. None of nine children with gastroenteritis due to other infectious agents showed immune conversions to rotavirus. A monoclonal capture IgM assay showed similar end-point titres and numbers of immune conversions when compared with a direct assay for antirotaviral IgM in serum and secretions. Use of the capture method eliminated false-positive reactions with the cell control. The assay for antirotaviral IgA units in secretions is simple, rapid, reproducible and reliable, and has proven of value in longitudinal epidemiological studies of rotavirus coproIgA profiles. Both the capture IgM technique and the single dilution IgA method permit analysis of large numbers of specimens and are appropriate for examination of immune responses to natural rotavirus infection or during vaccine trials.

Human viral gastroenteritis

During the last 15 years, several different groups of fastidious viruses that are responsible for a large proportion of acute viral gastroenteritis cases have been discovered by the electron microscopic examination of stool specimens. This disease is one of the most prevalent and serious clinical syndromes seen around the world, especially in children. Rotaviruses, in the family Reoviridae, and fastidious fecal adenoviruses account for much of the viral gastroenteritis in infants and young children, whereas the small caliciviruses and unclassified astroviruses, and possibly enteric coronaviruses, are responsible for significantly fewer cases overall. In addition to electron microscopy, enzyme immunoassays and other rapid antigen detection systems have been developed to detect rotaviruses and fastidious fecal adenoviruses in the stool specimens of both nonhospitalized patients and those hospitalized for dehydration and electrolyte imbalance. Experimental rotavirus vaccines have also been developed, due to the prevalence and seriousness of rotavirus infection. The small, unclassified Norwalk virus and morphologically similar viruses are responsible for large and small outbreaks of acute gastroenteritis in older children, adolescents, and adults. Hospitalization of older patients infected with these viruses is usually not required, and their laboratory diagnoses have been limited primarily to research laboratories.

Enzyme-linked immunosorbent assays for measurement of reovirus immunoglobulin G, A, and M levels in serum

Enzyme-linked immunosorbent assays were developed for the quantitation of anti-reovirus immunoglobulin G (IgG), IgA, and IgM in serum. The assays were specific, sensitive, and reproducible and measured antibodies to the reovirus group antigen. They should permit diagnosis of recent reovirus infection and longitudinal study of the development of reovirus group antibodies.

Characterization of a monoclonal antibody against infective larvae of Brugia malayi

Monoclonal antibodies were produced following immunization of mice with live infective larvae of Brugia malayi. One of these, 46.08.76, is an antibody that promotes adherence of mouse peritoneal macrophages and human peripheral blood leucocytes to the infective larvae of B. malayi and Wuchereria bancrofti, respectively, and kills them. Fresh normal serum, as a source of complement, augments this effect. The same monoclonal antibody conferred 89% protection to jirds (Meriones unguiculatus) against challenge infection of B. malayi stage-three larvae. This monoclonal antibody recognizes antigens of 80,000, 67,000, 52,000 and 36,000 MW proteins present among the antigens of larvae, as detected by an immunoblotting technique. The antibody also reacts with antigens of infective larvae of Litomosoides carinii, Dipetalonema viteae and B. pahangi, but to a smaller extent.

Possible role for rotavirus in the development of cows' milk enteropathy in infants

In order to test the hypothesis that rotavirus infection leads to IgE hypersensitivity to cows' milk, evidence of past rotavirus infection, as reflected by the presence of antibodies, was sought in two groups of children with cows' milk allergy. The groups were defined according to the time to react to milk challenge. In group I there were fifteen children with an adverse reaction within 40 min of milk challenge. The twenty-one children in group II had gastrointestinal reactions between 1 hr and 24 hr after milk challenge. The results showed a higher incidence of antibodies to rotavirus in group II than group I (P less than 0.05). Although group I patients had significantly higher levels of total and milk-specific IgE antibodies to cows' milk than those in group II, both patient groups had lower levels of serum IgG, IgA and IgM than a control population. No association between the presence of rotavirus antibodies and IgE hypersensitivity to cows' milk was found. However, an association between non-IgE milk enteropathy and previous rotavirus antibodies was demonstrated.

Non-neutralizing monoclonal antibodies to a trypsin-sensitive site on the major glycoprotein of rotavirus which discriminate between virus serotypes

Monoclonal antibodies were derived to a human rotavirus purified from stools. Three of the antibodies immunoprecipitated the rotavirus outer capsid glycoprotein gp 34 and were non-neutralizing. These antibodies reacted by enzyme immunoassay with cultivable rotaviruses showing the "long" RNA electropherotype but were inefficient as detectors of "long" RNA pattern rotaviruses in stools. Treatment of SA 11 rotavirus with 7.5 micrograms/ml porcine trypsin for 30 minutes at 37 degrees C irreversibly reduced binding of the antibodies to SA 11 rotavirus in enzyme immunoassays by 50 per cent. Binding was abolished in the presence of rotavirus-negative faecal extracts. These results indicate that non-neutralizing sites on gp 34 of rotaviruses can vary with RNA electropherotype and serotype, and that levels of trypsin currently in use to assist growth of rotaviruses in cell culture may alter the serological profile of the viruses.

Neutralizing monoclonal antibodies to human rotavirus and indications of antigenic drift among strains from neonates

Cells producing neutralizing monoclonal antibodies to a serotype 3 human neonatal rotavirus strain RV-3 were derived by fusion of hyperimmunized mouse spleen cells with mouse myeloma cells. As ascites fluid, three rotavirus-neutralizing monoclonal antibodies were characterized by hemagglutination inhibition and reacted with 17 cultivable mammalian rotaviruses representing five virus serotypes, by fluorescent focus neutralization and enzyme immunoassay. Two antibodies, Mab RV-3:1 and Mab RV-3:2, reacted with the seven serotype 3 rotaviruses only. Mab RV-3:1 was shown to bind to the outer capsid glycoprotein gp34 of rotavirus when variants of SA 11 rotavirus were used, and it therefore appears to react with the major neutralization epitope of serotype 3 rotaviruses. The antibody Mab RV-3:3 was specific for an epitope of RV-3 rotavirus not present on any other rotavirus of any serotype tested, including another neonatal isolate of identical RNA electropherotype isolated from the same ward of the same hospital as RV-3 3 months earlier. These two viruses were also distinguishable by fluorescent focus neutralization, using antiserum to RV-3 virus. Western blot analysis showed binding of Mab RV-3:3 to the trypsin cleavage product of the outer capsid protein p86 of RV-3. This suggests that antigenic drift may have occurred among neonatal rotaviruses in Melbourne. These monoclonal antibodies will be useful in serotyping assays of rotaviruses directly in stool samples, and in further analysis of antigenic variation within the serotype.

Kinetics of viral replication and local and systemic immune responses in experimental rotavirus infection

Rotavirus-seronegative mice were orally inoculated with murine rotavirus in order to study the kinetics of rotavirus replication and the relationship of viral replication to immunity and disease and to assess the effects of local and systemic antibodies on viral clearance and disease resolution.

An improved enzyme-linked immunosorbent assay for the detection of rotavirus in faeces of neonates

A direct enzyme-linked immunosorbent assay (EIA) for the detection of rotavirus in neonatal stools was developed. Rabbit antiserum against SA 11 rotavirus was incorporated as both coating and detector antibody, and rotavirus-negative rabbit serum was applied as a coating antibody control to eliminate false positive results. Pretreatment of stools with EDTA was found to increase both the sensitivity and specificity of the assay. This effect was greatest when 0.25 M EDTA (tetrasodium salt) was included in homogenized stool suspensions before the removal of solid debris by centrifugation. By electron microscopy, this EDTA pretreatment appeared to partly uncoat human rotavirus particles in faeces. Potentially suitable solid phase supports and horseradish peroxidase substrates were evaluated in the development of the assay. Screening of stool samples revealed that repeated freezing and thawing of stools eliminated positive EIA reactions. The SA 11 coating antibody compared favourably with a reference coating antiserum prepared against human faecal rotavirus strains. This EIA showed greater sensitivity for rotavirus detection than electron microscopy of stool concentrates prepared by ultracentrifugation, on testing 143 stools from 99 neonates and children. The assay has been applied successfully to detection of rotavirus in stools of neonates containing meconium, smaller amounts of viral antigen than in older children, and lacteal antirotaviral antibody. It is likely to be particularly useful for cross-infection studies in hospital wards and neonatal nurseries.

The major surface glycoprotein of simian rotavirus (SA11) contains distinct epitopes

The polypeptide specificities on monoclonal antibodies previously derived against the SA11 simian, NIC bovine, and Wa human strains of rotavirus were determined by radioimmunoprecipitation of infected cell lysates. All the monoclonal antibodies derived using NIC and Wa were found to be directed against the major component of the inner capsid, while most of the SA11 monoclones were directed against the major outer capsid glycoprotein. When several SA11 glycoprotein-specific monoclonal antibodies were used in competitive binding studies, four distinct epitopes, which correlated with the functional activities of the antibodies, were defined. One epitope appeared most critical for virus neutralization, another was involved to a lesser extent, and the remaining two epitopes seemed to have no role. A possible topographical arrangement of these epitopes is suggested.

Estimation of rotavirus immunoglobulin G antibodies in human serum samples by enzyme-linked immunosorbent assay: expression of results as units derived from a standard curve

A method for estimating rotavirus immunoglobulin G (IgG) antibodies by assay of human serum samples at a single serum dilution was studied. Antibody was measured by enzyme-linked immunosorbent assay (ELISA). The optical density of the reaction with a 1:100 dilution of each serum was expressed as ELISA units of antirotavirus IgG by reference to a standard curve. This standard curve was obtained by incorporation in each assay of five dilutions of a serum containing an arbitrary number of units of antirotavirus IgG. Test serum samples found to contain high amounts of antirotavirus IgG were reassayed at a 1:1,000 dilution. There was good correlation between antirotavirus IgG ELISA units in 45 serum samples and endpoint titers of the same samples (Spearman rank correlation coefficient rs, 0.95). Seroconversion during rotavirus infection was defined as an increase in antirotavirus IgG ELISA units per milliliter of greater than 28% (2 X intra-run coefficient of variation of the assay) in consecutive serum samples from the same child. Paired serum samples from nine children with diarrhea not due to rotavirus infection showed no seroconversions. Paired samples from eight children with rotavirus infection showed seroconversions. Estimation of antirotavirus IgG ELISA units in serum is simple, rapid, reproducible, and economical of serum samples. Standardization of results could be achieved by worldwide distribution of a standard serum. Its use would facilitate epidemiological surveys to evaluate potential rotavirus vaccines.

Iscom, a novel structure for antigenic presentation of membrane proteins from enveloped viruses

We describe here a novel type of immunostimulating complex, called 'iscom', in which virus membrane proteins are presented in a multimeric form. The matrix of the iscom is the glycoside Quil A (Spikoside; Iscotec AB), extracted from the bark of Quillaja saponaria Molina, which forms micelles at the critical micellar concentration of 0.03%. In micelle form, Quil A probably has regions accessible for hydrophobic interaction with the membrane proteins so that it can form complexes with them. Iscoms have been prepared with membrane proteins of para-influenza-3 (PI-3), measles and rabies viruses, and their immunizing potency tested in animals. In these experiments, iscoms prove to be at least 10 times more potent than micelles formed by aggregation of the membrane proteins alone. Iscoms of PI-3 and measles viruses also stimulate the formation of antibody to the fusion (F) protein, which is considered to be poorly immunogenic. No side effects of iscoms or of protein micelles have been observed.

Efficient coating of the solid phase with rotavirus antigens for enzyme-linked immunosorbent assay of immunoglobulin A antibody in feces

Sensitivity of the enzyme-linked immunosorbent assay for detecting serum antibodies to rotavirus was greatly enhanced when rotavirus particles were fragmented by chaotropic agents (NaSCN or guanidine hydrochloride) before adsorption of the antigens to the solid phase. For detecting fecal antibodies, the addition of fetal calf serum to the diluent was further needed to protect the antigens from the proteolytic activity of feces. With this technique, we readily detected immunoglobulin A antibody in feces from infantile gastroenteritis patients. Rate-zonal centrifugation of feces revealed that immunoglobulin A antibody activity sedimented with two peaks: one at 11S with a secretory component and another sedimenting slower than 7S, presumably as Fab portions.

Clinical immunity after neonatal rotavirus infection. A prospective longitudinal study in young children

To determine whether rotavirus infection in newborn babies conferred immunity to postneonatal rotavirus infection, we studied 81 babies at birth and kept them under clinical and serologic study for three years. During the first 14 days of life, 44 of the infants excreted rotavirus, and 37 did not. Fifty-five per cent of those with neonatal infection and 54 per cent of those without it had rotavirus infection during the next three years. Symptoms associated with postneonatal rotavirus infection were significantly less frequent and less severe in the infants who had had neonatal infection (P = 0.003) than in those who had not. Thirty-eight per cent of the former group (9 of 24 infants) had symptoms of mild (3 infants) or moderate (6) severity during the first postneonatal infection. In contrast, 85 per cent of the latter group (17 of 20 infants) had mild (3), moderate (6), or severe (8) symptoms. We conclude that neonatal rotavirus infection does not confer immunity against reinfection but does protect against the development of clinically severe disease during reinfection.

Enzyme-linked immunosorbent assay for rubella immunoglobulin G: new method for attachment of antigens to microtiter plates

Many of the enzyme-linked immunosorbent assay (ELISA) techniques previously described for detection of rubella-specific antibodies employ complex technology not available in routine diagnostic laboratories. The method described allows the use of commercially available rubella hemagglutination inhibition (HI) antigen. Passive adsorption of these antigens to plastic is variable, but with the use of albumin as a bridge, it is possible to attach the antigen reliably to the plastic wells. Over 1,500 sera were tested by both HI and ELISA techniques to detect the presence of rubella antibodies. These sera were selected with a bias towards those with low levels of rubella-specific antibody, since it has been demonstrated that it is in this range that discrepancies are more likely to occur between HI and ELISA techniques. In 99% of the sera tested, the results of both techniques were in agreement. On the basis of these results, the technique offers a useful alternative to the routine rubella HI test and other ELISA techniques which need sophisticated antigen preparations.

Derivation of neutralizing monoclonal antibodies against rotavirus

Monoclonal antibodies were derived against the SA11 simian, NIC bovine, and Wa human rotavirus strains and characterized by enzyme-linked immunosorbent assay, plaque neutralization, and hemagglutination inhibition. Several strain SA11-specific antibodies were found to have neutralizing and hemagglutination-inhibiting capacity.

Effects of antibodies, trypsin, and trypsin inhibitors on susceptibility of neonates to rotavirus infection

Levels of antirotaviral secretory immunoglobulin A were measured by enzyme-linked immunosorbent assay in colostrum and milk samples collected daily for the first 5 days postpartum from 49 mothers breast-feeding their infants. The trypsin-inhibitory capacity of these lacteal secretion samples was assessed by their ability to inhibit the hydrolysis of alpha-N-benzoyl-DL-arginine-p-nitroanilide by trypsin. Stools passed by these breast-fed infants and by an additional 43 bottle-fed infants were pooled by individual and examined by electron microscopy for rotavirus. Stool trypsin levels were estimated with the gelatin hydrolysis test. Breast-fed infants were significantly less likely to become infected with rotavirus and showed significantly lower stool tryptic activity than did bottle-fed infants. Breast-fed infants who did not excrete rotavirus over the 5-day period received milk of significantly higher antirotaviral secretory immunoglobulin A or trypsin-inhibitory capacity or both than breast-fed infants who were infected with rotavirus. A case of probable maternal rotavirus infection during pregnancy, producing greatly elevated lacteal antirotaviral secretory immunoglobulin A levels lasting for 2 years, was detected. Results of this study suggest that both antibodies and trypsin inhibitors in human milk can be associated with the protection of neonates against rotavirus infection in the first 5 days of life.

Coproantibody response to rotavirus infection

During three months after a family outbreak of diarrhoeal disease, rotavirus-specific immunoglobulins of the IgA, IgG and IgM classes were measured by enzyme-linked immunosorbent assay in faecal extracts from the four people involved. Shortly afterwards, sequential extracts were obtained from another infant after a proven rotavirus infection. Rotavirus infection was diagnosed by electron microscopy in three of the patients from whom acute-phase faecal samples were obtained, and all five patients developed a transient specific-antibody response. Antirotaviral IgA, IgM and IgG all reached peak titres between two and four weeks after infection, then dropped back to undetectable levels after two months. If these findings are confirmed in larger numbers of cases, they will provide the basis for simple diagnosis of recent rotavirus infections, without the need of even a single sample of serum.

Transfer of antirotaviral antibodies from mothers to their infants

Levels of rotavirus-specific immunoglobulin G (IgG), IgA, IgM, and secretory immunoglobulin in maternal and cord serum, colostrum and milk, and infants' stools were measured by enzyme-linked immunosorbent assay in 92 mothers and their infants. Although antirotaviral IgG, IgA, and secretory immunoglobulin were present in most maternal sera, only IgG crossed the placenta. All samples of colostrum and milk tested contained antirotaviral secretory immunoglobulin and IgA except those of two women in whom IgA deficiency was subsequently described. Specific IgM and IgG were also detected in many colostral samples. Antirotaviral IgA was detected in many colostral samples. Antirotaviral IgA was detected in stools of breast-fed but not bottle-fed neonates. Apparently the human infant receives rotaviral antibodies both transplacentally and via maternal colostrum and milk.