Rotavirus-specific Immunoglobulin Research Articles

Association Between Maternal Breastmilk Microbiota Composition and Rotavirus Vaccine Response in African, Asian, and European Infants: A Prospective Cohort Study.

Maternal breastmilk is a source of pre- and pro-biotics that impact neonatal gut microbiota colonization. Because oral rotavirus vaccines (ORVs) are administered at a time when infants are often breastfed, breastmilk microbiota composition may have a direct or indirect influence on vaccine take and immunogenicity. Using standardized methods across sites, we compared breastmilk microbiota composition in relation to geographic location and ORV response in cohorts prospectively followed from birth to 18 weeks of age in India (n = 307), Malawi (n = 119), and the United Kingdom ([UK] n = 60). Breastmilk microbiota diversity was higher in India and Malawi than the UK across 3 longitudinal samples spanning weeks of life 1 to 13. Dominant taxa such as Streptococcus and Staphylococcus were consistent across cohorts; however, significant geographic differences were observed in the prevalence and abundance of common and rare genera throughout follow up. No consistent associations were identified between breastmilk microbiota composition and ORV outcomes including seroconversion, vaccine shedding after dose 1, and postvaccination rotavirus-specific immunoglobulin A level. Our findings suggest that breastmilk microbiota composition may not be a key factor in shaping trends in ORV response within or between countries.

Rotavirus specific maternal antibodies and immune response to RV3-BB rotavirus vaccine in central java and yogyakarta, Indonesia

BackgroundPlacental or breast milk maternal antibodies can potentially reduce oral rotavirus vaccine efficacy in developing countries. We aimed to examine the relationship between the level of rotavirus specific immunoglobulin A (IgA) and neutralising antibodies (NA) in colostrum and breast milk and cord IgG, with cumulative vaccine take following one and three doses of oral RV3-BB rotavirus vaccine within a Phase IIb trial in Indonesia. Methods196 infants received three doses of RV3-BB in a randomized, double-blinded trial, using a neonatal schedule (first dose at 0–5 days of age, n = 61), an infant schedule (first dose at ~ 8 weeks of age, n = 67) or placebo (n = 68). Rotavirus specific IgA and NA in colostrum and breast milk, rotavirus specific cord IgG, Serum IgA and stool excretion were measured. ResultsThere was little evidence of an association between IgA in colostrum or breast milk and cumulative vaccine take after three doses in the neonatal or infant groups. In the neonatal group, there was a negative association between IgG titre in cord blood and cumulative vaccine take (odds ratio [OR] 0.96; 95% confidence interval [CI] 0.92–1.00; p = 0.03) and serum IgA response (OR 0.94; 95%CI 0.89–0.99; p = 0.02) after one dose of vaccine, which were not evident after three doses in the neonatal or infant groups. ConclusionsAmongst Indonesian infants we did not find an association between IgA in colostrum or breast milk and vaccine take after 3 doses of RV3-BB vaccine. Maternal rotavirus antibodies in breast milk appear to have minimal impact on RV3-BB vaccine take when administered with a short delay in breast-feeding in settings with a high rotavirus disease burden.

The effect of increased inoculum on oral rotavirus vaccine take among infants in Dhaka, Bangladesh: A double-blind, parallel group, randomized, controlled trial

BackgroundOral, live-attenuated rotavirus vaccines suffer from impaired immunogenicity and efficacy in low-income countries. Increasing the inoculum of vaccine might improve vaccine response, but this approach has been inadequately explored in low-income countries. MethodsWe performed a double-blind, parallel group, randomized controlled trial from June 2017 through June 2018 in the urban Mirpur slum of Dhaka, Bangladesh to compare vaccine take (primary outcome) among healthy infants randomized to receive either the standard dose or double the standard dose of oral Rotarix (GlaxoSmithKline) vaccine at 6 and 10 weeks of life. Infants with congenital malformations, birth or enrollment weight <2000 gm, known immunocompromising condition, enrollment in another vaccine trial, or other household member enrolled in the study were excluded. Infants were randomized using random permuted blocks. Vaccine take was defined as detection of post-vaccination fecal vaccine shedding by real-time reverse transcription polymerase chain reaction with sequence confirmation or plasma rotavirus-specific immunoglobulin A (RV-IgA) seroconversion 4 weeks following the second dose. Results220 infants were enrolled and randomized (110 per group). 97 standard-dose and 92 high-dose infants completed the study per-protocol. For the primary outcome, no significant difference was observed between groups: vaccine take occurred in 62 (67%) high-dose infants versus 69 (71%) standard-dose infants (RR 0.92, 95% CI 0.67–1.24). However, in post-hoc analysis, children with confirmed vaccine replication had significantly increased RV-IgA responses, independent of the intervention. No significant adverse events related to study participation were detected. ConclusionsAdministration of double the standard dose of an oral, live-attenuated rotavirus vaccine (Rotarix) did not improve vaccine take among infants in urban Dhaka, Bangladesh. However, improved immunogenicity in children with vaccine replication irrespective of initial inoculum provides further evidence for the need to promote in-host replication and improved gut health to improve oral vaccine response in low-income settings. ClinicalTrials.gov: NCT02992197.

NLRC5 deficiency has a moderate impact on immunodominant CD8+ T-cell responses during rotavirus infection of adult mice.

The NOD-like receptor (NLR) family plays an important role in innate immunity. Class II transactivator and NOD-like receptor caspase activation and recruitment domain CARD containing 5 (NLRC5) are unusual members of the NLR family that instead of recognizing pathogen-associated or damage-associated molecular patterns, form enhanceosomes with adaptor molecules and modulate major histocompatibility complex (MHC) class II and MHC class I expression, respectively. While NLRC5 has been shown to play a role during intracellular pathogen infection and tumor cell immune evasion, its role in regulating antigen-specific CD8+ T-cell responses at the intestinal mucosa has not been investigated. Here, we take advantage of the rotavirus model in adult mice to dissect the impact of NLRC5 on CD8+ T-cell responses to this viral infection at the gut mucosa. We show that while Nlrc5-/- mice exhibited normal proportions of T-cell subpopulations in the intraepithelial and lamina propria compartments, these mice had decreased baseline MHC class I expression on various immune cells in the lamina propria. Upon rotavirus infection, Nlrc5 deficiency resulted in impaired H2-Kb -restricted antigen-specific CD8+ T-cell responses, which were recapitulated in mice deficient for Nlrc5 within the dendritic cell compartment. The impaired CD8+ T-cell response in Nlrc5-/- mice was not significant enough to impact viral titers, suggesting compensation in Nlrc5-/- mice, perhaps as a result of higher numbers of activated B cells in the mesenteric lymph nodes and normal rotavirus-specific immunoglobulin A responses. Collectively, our results demonstrate a minor role for NLRC5 in modulating H2-Kb -restricted antigen-specific CD8+ T-cell responses in the small intestine during rotavirus infection in adult mice.

Nonsecretor Histo-blood Group Antigen Phenotype Is Associated With Reduced Risk of Clinical Rotavirus Vaccine Failure in Malawian Infants.

BackgroundHisto–blood group antigen (HBGA) Lewis/secretor phenotypes predict genotype-specific susceptibility to rotavirus gastroenteritis (RVGE). We tested the hypothesis that nonsecretor/Lewis-negative phenotype leads to reduced vaccine take and lower clinical protection following vaccination with G1P[8] rotavirus vaccine (RV1) in Malawian infantsMethodsA cohort study recruited infants receiving RV1 at age 6 and 10 weeks. HBGA phenotype was determined by salivary enzyme-linked immunosorbent assay (ELISA). RV1 vaccine virus shedding was detected by quantitative real-time polymerase chain reaction (qRT-PCR) in stool collected on alternate days for 10 days post-immunization. Plasma rotavirus–specific immunoglobulin A was determined by ELISA pre- and post-immunization. In a case-control study, HBGA phenotype distribution was compared between RV1-vaccinated infants with RVGE and 1:1 age-matched community controls. Rotavirus genotype was determined by RT-PCR.ResultsIn 202 cohort participants, neither overall vaccine virus fecal shedding nor seroconversion differed by HBGA phenotype. In 238 case-control infants, nonsecretor phenotype was less common in infants with clinical vaccine failure (odds ratio [OR], 0.39; 95% confidence interval [CI], 0.20–0.75). Nonsecretor phenotype was less common in infants with P[8] RVGE (OR, 0.12; 95% CI, 0.03–0.50) and P[4] RVGE (OR, 0.17; 95% CI, 0.04–0.75). Lewis-negative phenotype was more common in infants with P[6] RVGE (OR, 3.2; 95% CI, 1.4–7.2).ConclusionsNonsecretor phenotype was associated with reduced risk of rotavirus vaccine failure. There was no significant association between HBGA phenotype and vaccine take. These data refute the hypothesis that high prevalence of nonsecretor/Lewis-negative phenotypes contributes to lower rotavirus vaccine effectiveness in Malawi.

Rotavirus-Specific Immunoglobulin A Responses Are Impaired and Serve as a Suboptimal Correlate of Protection Among Infants in Bangladesh.

BackgroundRotavirus (RV)–specific immunoglobulin A (IgA) responses following oral RV vaccination are impaired in low-income countries, where the utility of RV-IgA as a correlate of protection (CoP) remains unclear. In a monovalent oral RV vaccine (Rotarix) efficacy trial among infants in Dhaka, Bangladesh, we identified factors associated with poor RV-IgA responses and explored the utility of RV-IgA as a CoP.MethodsInfants were randomized to receive Rotarix or no Rotarix at 10 and 17 weeks of life and followed with active diarrheal surveillance. RV-IgA concentration, seroconversion, and seropositivity were determined at 18 weeks of life and analyzed for correlation(s) with rotavirus diarrhea (RVD) and for contribution to Rotarix vaccine effect.ResultsAmong vaccinated infants, overall RV-IgA geometric mean concentration was 21 U/mL; only 27% seroconverted and 32% were seropositive after vaccination. Increased RV-specific maternal antibodies significantly impaired immunogenicity. Seroconversion was associated with reduced risk of RVD through 1 year of life, but RV-IgA seropositivity only explained 7.8% of the vaccine effect demonstrated by the clinical endpoint (RVD).ConclusionsRV-IgA responses were low among infants in Bangladesh and were significantly impaired by maternal antibodies. RV-IgA is a suboptimal CoP in this setting; an improved CoP for RV in low-income countries is needed.Clinical Trials RegistrationNCT01375647.

Rotavirus infection.

Rotavirus infections are a leading cause of severe, dehydrating gastroenteritis in children <5 years of age. Despite the global introduction of vaccinations for rotavirus over a decade ago, rotavirus infections still result in >200,000 deaths annually, mostly in low-income countries. Rotavirus primarily infects enterocytes and induces diarrhoea through the destruction of absorptive enterocytes (leading to malabsorption), intestinal secretion stimulated by rotavirus non-structural protein 4 and activation of the enteric nervous system. In addition, rotavirus infections can lead to antigenaemia (which is associated with more severe manifestations of acute gastroenteritis) and viraemia, and rotavirus can replicate in systemic sites, although this is limited. Reinfections with rotavirus are common throughout life, although the disease severity is reduced with repeat infections. The immune correlates of protection against rotavirus reinfection and recovery from infection are poorly understood, although rotavirus-specific immunoglobulin A has a role in both aspects. The management of rotavirus infection focuses on the prevention and treatment of dehydration, although the use of antiviral and anti-emetic drugs can be indicated in some cases.

Dual Functions of Lactobacillus acidophilus NCFM as Protection Against Rotavirus Diarrhea

The aim of the study was to examine the dose effects of Lactobacillus acidophilus (LA) NCFM strain on rotavirus-specific antibody and B-cell responses in gnotobiotic pigs vaccinated with an oral attenuated human rotavirus (AttHRV). Pigs were inoculated with AttHRV vaccine in conjunction with high-dose LA (14 doses, total 2.2 × 10(6) colony-forming units [CFU]), intermediate-dose LA (MidLA) (9 doses, total 3.2 × 10(9) CFU), low-dose LA (LoLA) (5 doses, total 2.1 × 10(6) CFU), or without LA feeding. Protection against rotavirus shedding and diarrhea was assessed upon challenge with a virulent HRV. Rotavirus-specific immunoglobulin A (IgA) and IgG antibodies in serum and rotavirus-specific IgA and IgG antibody-secreting cells (ASCs) and memory B cells in ileum, spleen, and blood of the pigs were measured and compared among treatment groups. The MidLA, but not high-dose LA or LoLA, significantly reduced rotavirus diarrhea (MidLA-only group) and significantly improved the protection conferred by AttHRV vaccine (MidLA + AttHRV group). Associated with the increased protection, MidLA significantly enhanced rotavirus-specific antibody, ASCs, and memory B-cell responses to AttHRV vaccine. High-dose LA or LoLA did not enhance virus-specific antibody and ASC responses, and hence did not improve the vaccine efficacy. These findings highlight the importance of dose selection and indicate that certain specific lactobacilli strains at the appropriate dose have the dual function of reducing rotavirus diarrhea and enhancing the immunogenicity and protective efficacy of rotavirus vaccines.

Detection of rotavirus specific immunoglobulins in the serum of neonatal piglets with or without colostrum feeding

Rotavirus (RV) infection remains a major source of morbidity and mortality worldwide. Although RV vaccines are available, they do not confer complete protection in malnourished populations. Our long‐term goal is to develop a piglet RV vaccination model. Piglets do not receive Ig prenatally; however, porcine colostrum contains RV‐specific immunoglobulins (Ig) that are taken up by the gut. Herein, the time course of serum RV‐specific immunoglobulins was measured in piglets that were colostrum‐deprived and orally‐gavaged with sow serum for 24h (CD, n=4) or received 48h colostrum and were randomized to be sow‐reared (SR, n=6) or formula‐fed (FC, n=6). Serum RV specific IgG, IgA and IgM concentrations were measured by ELISA on d7, 14, 21 and 28. On d7, CD piglets had lower (P&lt; 0.05) IgG than SR or FC and no detectable IgA and IgM. Overall, IgG, IgA and IgM concentrations decreased (P&lt; 0.05) between d7 to d28 in FC and SR. IgG concentrations were greater (P&lt;0.05) in FC than SR on d7 and d14. IgA and IgM concentrations did not differ between FC and SR between d7 to d28. Limiting colostrum intake to 48h did not reduce the serum RV specific antibodies of FC vs. SR piglets. Thus, providing serum may confer immune protection while limiting exposure to RV‐specific Ig.

Rotavirus immunoglobulin levels among Indian mothers of two socio‐economic groups and occurrence of rotavirus infections among their infants up to six months

Rotavirus specific immunoglobulin levels were estimated and compared between mothers undergoing delivery from two socio-economic groups (n = 56 each) by direct/capture ELISA. IgG geometric mean titers (GMTs) of cord blood/mothers serum at delivery were significantly higher in the higher socio-economic group (HSG) as compared to the lower socio-economic group (LSG) (P < 0.01). Thirty-four mother-infant pairs (17 from each group) were followed-up up to 6 months for the occurrence of rotavirus infections. All follow-up LSG infants were low birth weight as against none from the HSG. Detection of virus by ELISA/RT-PCR and considering IgM/IgA seroconversion as an index of infection, 11 and 17 infants from HSG and LSG respectively had rotavirus infections. Two infants from LSG were hospitalized for severe rotavirus diarrhea but none from the HSG. Lower IgG levels in the LSG mother-infant pairs as compared to those of HSG, suggests a possible role of under nutrition in development of antibodies and immunity. Infants from the HSG who did not have rotavirus infections had significantly higher IgG GMTs in cord blood and serum samples at 6 months, than those HSG infants who had symptomatic/asymptomatic rotavirus infections (P < 0.05). In conclusion, fewer rotavirus infections occur when cord blood contains higher level of IgG antibodies, suggesting a role of protective immunity.

Rotavirus-specific B cells induced by recent infection in adults and children predominantly express the intestinal homing receptor alpha4beta7.

In vivo replication of rotaviruses is generally limited to enterocytes. Because of this restriction, most blood circulating rotavirus-specific B cells are hypothesized to originate in Peyer's patches and should express the intestinal homing receptor alpha4beta7. To test this hypothesis in humans, we used a flow cytometry assay that identifies antigen-activated (IgD-) B cells (CD19+) that express surface rotavirus-specific immunoglobulin. With this assay we could detect rotavirus-specific B cells in both children and adults with an acute rotavirus (RV) infection. Staining with an anti-alpha4beta7 monoclonal antibody, we could determine that B cells that express rotavirus-specific surface immunoglobulin predominantly express alpha4beta7. The response of rotavirus-specific antibody-secreting cells in the peripheral blood of children and adults with acute rotavirus infection was also studied by ELISPOT. The antibody-secreting cells of children were mainly of the IgM isotype, while the antibody-secreting cells of adults were predominantly of the IgA and IgG isotype. alpha4beta7+ and alpha4beta7- subsets of peripheral blood mononuclear cells were purified using paramagnetic beads and then tested in the ELISPOT assay. Rotavirus-specific antibody-secreting cells were predominantly present in the alpha4beta7+ subpopulation. The flow cytometry assay we have described will permit future studies to characterize the phenotype of virus-specific B cells and could be useful in the study of the immunogenicity and protective efficacy of RV vaccines and the identification of markers of protective immunity.

Intranasal administration of 2/6-rotavirus-like particles with mutant Escherichia coli heat-labile toxin (LT-R192G) induces antibody-secreting cell responses but not protective immunity in gnotobiotic pigs.

We investigated the immunogenicity of recombinant double-layered rotavirus-like particle (2/6-VLPs) vaccines derived from simian SA11 or human (VP6) Wa and bovine RF (VP2) rotavirus strains. The 2/6-VLPs were administered to gnotobiotic pigs intranasally (i.n.) with a mutant Escherichia coli heat-labile toxin, LT-R192G (mLT), as mucosal adjuvant. Pigs were challenged with virulent Wa (P1A[8],G1) human rotavirus at postinoculation day (PID) 21 (two-dose VLP regimen) or 28 (three-dose VLP regimen). In vivo antigen-activated antibody-secreting cells (ASC) (effector B cells) and in vitro antigen-reactivated ASC (derived from memory B cells) from intestinal and systemic lymphoid tissues (duodenum, ileum, mesenteric lymph nodes [MLN], spleen, peripheral blood lymphocytes [PBL], and bone marrow lymphocytes) collected at selected times were quantitated by enzyme-linked immunospot assays. Rotavirus-specific immunoglobulin M (IgM), IgA, and IgG ASC and memory B-cell responses were detected by PID 21 or 28 in intestinal and systemic lymphoid tissues after i.n. inoculation with two or three doses of 2/6-VLPs with or without mLT. Greater mean numbers of virus-specific ASC and memory B cells in all tissues prechallenge were induced in pigs inoculated with two doses of SA11 2/6-VLPs plus mLT compared to SA11 2/6-VLPs without mLT. After challenge, anamnestic IgA and IgG ASC and memory B-cell responses were detected in intestinal lymphoid tissues of all VLP-inoculated groups, but serum virus-neutralizing antibody titers were not significantly enhanced compared to the challenged controls. Pigs inoculated with Wa-RF 2/6-VLPs (with or without mLT) developed higher anamnestic IgA and IgG ASC responses in ileum after challenge compared to pigs inoculated with SA11 2/6-VLPs (with or without mLT). Three doses of SA 11 2/6-VLP plus mLT induced the highest mean numbers of IgG memory B cells in MLN, spleen, and PBL among all groups postchallenge. However, no significant protection against diarrhea or virus shedding was evident in any of the 2/6-VLP (with or without mLT)-inoculated pigs after challenge with virulent Wa human rotavirus. These results indicate that 2/6-VLP vaccines are immunogenic in gnotobiotic pigs when inoculated i.n. and that the adjuvant mLT enhanced their immunogenicity. However, i.n. inoculation of gnotobiotic pigs with 2/6-VLPs did not confer protection against human rotavirus challenge.

Relative importance of rotavirus-specific effector and memory B cells in protection against challenge.

Adult BALB/c mice were orally inoculated with murine (strain EDIM), simian (strain RRV), or bovine (strain WC3) rotavirus. Six or 16 weeks after inoculation, mice were challenged with EDIM. At the time of challenge and in the days immediately following challenge, production of rotavirus-specific immunoglobulin A (IgA), IgG, and IgM by small intestinal lamina propria lymphocytes (LPL) was determined by fragment culture, and quantities of virus-specific antibodies at the intestinal mucosal surface were determined by intestinal lavage. Mice immunized with EDIM were completely protected against EDIM challenge both 6 and 16 weeks after immunization. Protection was associated with production of high levels of IgA by LPL and detection of virus-specific IgA at the intestinal mucosal surface. In addition, animals immunized and later challenged with EDIM did not develop a boost in antibody responses, suggesting that they were also not reinfected. We also found that in mice immunized with nonmurine rotaviruses, (i) quantities of virus-specific IgA generated following challenge were greater 16 weeks than 6 weeks after immunization, (ii) immunization enhanced the magnitude but did not hasten the onset of production of high quantities of virus-specific IgA by LPL after challenge, and (iii) immunization induced partial protection against challenge; however, protection was not associated with either production of virus-specific antibodies by LPL or detection of virus-specific antibodies at the intestinal mucosal surface.

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.

Antibody response in serum and intestine in children up to six months after a naturally acquired rotavirus gastroenteritis.

The aim of this study was to provide detailed information about the local and systemic antibody response and their relationship following a rotavirus gastroenteritis. Rotavirus-specific immunoglobulins were analyzed by enzyme-linked immunosorbent assay (ELISA). The study included 49 children referred to hospital with rotavirus gastroenteritis and 16 children with nonrotavirus gastroenteritis. The concentrations of rotavirus immunoglobulin A (IgA) in serum increased within the first 2 weeks and those of rotavirus IgG within the first month after the onset of diarrhea. Thereafter, they remained unchanged during the 6-month observation period. Rotavirus ScIg (i.e., antirotavirus immunoglobulin-containing secretory component) appeared in serum almost exclusively within 7-14 days after onset (i.e., 85% of the samples). After the first 2 weeks, rotavirus IgA could be detected in the majority of fecal samples, even up to 6 months after the disease. However, rotavirus ScIg was absent in the majority of fecal samples. The severity of illness correlated only with the increase of rotavirus IgG in serum. Conclusively, there is a longstanding immune response after a naturally acquired rotavirus gastroenteritis. Moreover, with the present methods, measurements of rotavirus IgA and IgG in serum can be safely used for serodiagnosis, even when samples are taken with 6-month interval. It is suggested that trials with rotavirus vaccines include measurements of rotavirus IgA and ScIg in serum and rotavirus IgA in feces.

Rotavirus antibodies in the mother and her breast-fed infant.

The transfer of rotavirus antibodies from 25 healthy mothers to their breast-fed infants was investigated during the period of lactation (mean, 3.9 months; range, 1-9 months). Furthermore, the destiny of these antibodies in the infants' gastrointestinal tract and serum was examined. Rotavirus-specific immunoglobulins were analyzed by the ELISA (enzyme-linked immunosorbent assay) technique. All the mothers had rotavirus IgA and IgG in serum. About 80% of the mothers had low concentrations of rotavirus ScIg (i.e., antirotavirus immunoglobulin containing secretory component) in serum at the beginning of the lactation period declining to about 45% at the end of the period. From a few days after delivery to about 2 weeks later, the concentrations of rotavirus IgA and ScIg in milk declined. Thereafter, they remained unchanged. There was a positive correlation among the concentrations of rotavirus IgA in serum and rotavirus IgA as well as ScIg in milk. Rotavirus IgG in the infants' serum correlated with that of the mothers. Few samples of the infants' duodenal fluid contained rotavirus IgA or ScIg. On the other hand, about 80% of the infants' fecal samples contained rotavirus ScIg and IgA. Rotavirus IgA and ScIg disappeared from the infants' feces after cessation of lactation. Hence, it may be concluded that infants receive rotavirus IgG through the placenta, and rotavirus ScIg and IgA in constant amounts via milk throughout the period of lactation. The small intestine is flushed with rotavirus ScIg and IgA at each breast-meal, and these antibodies survive proteolysis in the gut. A possible protectional effect of rotavirus ScIg or IgA requires frequent breast-meals, and the effect is limited to the period of lactation.

THE USE OF HOMOLOGOUS AND HETEROLOGOUS ROTAVIRUS ANTIBODIES FOR THE PREVENTION OF ROTAVIRUS GASTROENTERITIS

Rotavirus is an important cause of serious gastroenteritis in children. One possible strategy for the prevention of rotavirus gastroenteritis is the oral administration of rotavirus specific immunoglobulin. We utilized a mouse model of rotavirus infection to examine the efficacy of rotavirus antibody for the prevention of symptomatic rotavirus diarrhea. This model consists of the feeding of seronegative infant mice a predetermined amount of murine rotavirus and antibody and then assaying the animals for intestinal antigen excretion, liquid colonic contents, and immune response. We found that mouse serum containing homologous antibodies to murine rotavirus completely protected animals from symptomatic infection and viral shedding while non-immune serum provided no protection. Neither immune nor non-immune mouse milk offered any protection from infection. In the case of heterologous sources of sera obtained from animals experimentally infected with human or bovine rotaviruses, and antibodies derived from the yolks of eggs obtained from chickens immunized with rotaviruses full protection was provided from symptomatic disease. Non-immune sera and immune human milk did not protect the animal from infection. The majority of the animals treated with effective specific immunoglobulin preparations developed a rotavirus systemic antibody response. These studies indicate that homologous and heterologous sources of rotavirus antibodies can provide protection from rotavirus diarrhea and may allow for active immunity to occur.

Serum and intestinal immune response to rotavirus enteritis in children.

This study was designed to assess the serum and mucosal immune response to naturally acquired rotavirus enteritis in children. Serum and duodenal secretions were collected 1 week and again 4 to 5 weeks after the onset of illness from 10 children. In two of these children, the procedure was repeated 12 to 15 months later. Another 10 children with bacterial enteritis were studied as controls. The antibody response in serum included a significant elevation of rotavirus-specific immunoglobulin M (IgM) in acute-phase samples (P less than 0.05), but not in convalescent-phase samples, when compared with controls. Rotavirus-specific IgG and IgA levels were significantly elevated in convalescent-phase serum when compared with acute-phase serum (P less than 0.025), but not in control serum. Rotavirus-specific IgA levels in convalescent duodenal secretions were significantly raised when compared with both acute-phase and control samples (P less than 0.01). Rotavirus-specific IgM levels were elevated in acute-phase duodenal secretions (P less than 0.05), but not in convalescent-phase secretions. In two children, the secretory IgA response had disappeared by 12 months. These studies demonstrate the presence of rotavirus-specific antibody in duodenal secretions which may be important for protection against reinfection and may be capable of being stimulated by oral vaccination.

Traveler's diarrhea associated with rotavirus infection: analysis of virus-specific immunoglobulin classes.

An enzyme-linked immunosorbent assay for the detection of rotavirus-specific immunoglobulin G (IgG), IgM, and IgA antibodies was used in a serological study of Traveler's diarrhea. The antigenically related simian rotavirus (SA-11) was used as antigen in this study. Serum was obtained from two groups of volunteers before travel (pre-travel) and at various times after arrival at their destination (post-travel). One group consisted of 47 American Peace Corps volunteers who traveled to Honduras, and the second group consisted of 66 Panamanian travelers who visited Mexico. An association between rotavirus and Traveler's diarrhea was found in each group with 36% of American Peace Corps volunteers and 30% of Panamanians with diarrhea demonstrating a greater than or equal to 4-fold increase in rotavirus antibody titers in the post- as compared to the pre-travel specimens. While no rotavirus-specific IgM antibody was detected in any serum tested, increases in specific antibody were found in both the IgG and IgA immunoglobulin classes.

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.