Development of a new enzyme immunoassay for improved detection of rotavirus in fecal specimens of vaccinated infants.

BACKGROUND: Group A rotavirus is the most common cause of acute diarrhea in young children worldwide. A simple and rapid enzyme immunoassay (EIA) has been commonly used to detect rotavirus infection and evaluate rotavirus vaccines. Currently licensed commercial EIA kits have low sensitivity. A more sensitive detection of rotavirus can improve rotavirus diagnostics and vaccine efficacy studies. OBJECTIVE: A biotin-avidin based sandwich EIA was developed and compared with commercial EIA kits for improved detection of viral shedding in fecal samples from infants who received human rotavirus vaccine Rotarix in Mexico. STUDY DESIGN: A monoclonal antibody (mAb: 1D4) specific to human rotavirus group antigen VP6 was prepared and used to develop a biotin-avidin based sandwich EIA. This EIA was employed to test 128 fecal samples from vaccinated infants, in comparison with two commercial EIA kits using RT-PCR as a reference. RESULTS: A new biotin-avidin based sandwich EIA showed specific reaction to group A rotaviruses, but not to other enteric viruses. This new EIA had a detection rate of 36.7% for rotavirus antigen shedding in fecal specimens, which was two times higher (16.4%, 18.0%) than those from two commercial EIA kits. CONCLUSION: The new EIA had specificity and higher sensitivity than commercial kits. This new EIA has the potential to detect rotavirus at lower concentration in clinical specimens and thus should be further evaluated as a more sensitive kit for use in diagnostics and vaccine efficacy and effectiveness studies.

Innate Immune Factors in Mothers' Breast Milk and Their Lack of Association With Rotavirus Vaccine Immunogenicity in Nicaraguan Infants.

To better understand underlying causes of lower rotavirus vaccine effectiveness in low-middle income countries (LMICs), we measured innate antiviral factors in Nicaraguan mothers' milk and immune response to the first dose of the pentavalent rotavirus vaccine in corresponding infants. No relationship was found between concentrations of innate factors and rotavirus vaccine response.

Breastfeeding linked to the reduction of both rotavirus shedding and IgA levels after Rotarix® immunization in Mexican infants.

We examined potential risk factors on vaccine virus shedding and antibody seroresponse to human rotavirus vaccine (Rotarix) in Mexican infants. Two doses of Rotarix were administered to infants during the first two visits for their routine childhood immunization (∼8 and 15weeks of age) in Mexico City. Infant's characteristics and socioeconomic indicators were obtained, including history of long-term feeding practices (exclusively/predominantly breastfed and exclusively/predominantly non-breastfed). Two serum specimens were collected, one during the second rotavirus vaccine visit and one 7weeks later. Stool specimens were collected between days 4-7 after each of the two rotavirus vaccine doses. Rotavirus IgA and IgG titers in serum were determined by enzyme immunoassays (EIA) and rotavirus shedding in stool was assessed by EIA and confirmed by RT-PCR. The overall rotavirus IgA geometric mean titers (GMT) increased significantly post dose 2 from post dose 1 [176 (95%CI: 113-273) to 335 (238-471); p=0.020). Infants who were exclusively/predominantly breastfed were less likely to shed vaccine virus in stool than those who were formula-fed (22% vs. 43%, p=0.016). Infants who were breastfed had lower rotavirus IgA titers than those who were formula-fed after dose 1 [GMT: 145 (84-250) vs. 267 (126-566) p=0.188] and dose 2 [236 (147-378) vs.578 (367-910), p=0.007]. Infants who shed vaccine virus post dose 1 had significantly higher serum IgA GMT than those who did not shed [425 (188-965) vs. 150 (84-266), p=0.038]. Breastfeeding was linked with the reduction of both stool vaccine shedding, and IgA seroresponse. The reduced rotavirus replication in the gut and shedding after dose 1 may explain in part the lower IgA response in serum.

Prevalence of groups A and C rotavirus antibodies in infants with biliary atresia and cholestatic controls.

OBJECTIVE: To analyze the prevalence of acute asymptomatic group A and C rotavirus (RV-A and RV-C) infection in neonates with cholestasis. STUDY DESIGN: Participants were infants <180 days of age with cholestasis (serum direct or conjugated bilirubin >20% of total and ≥2 mg/dL) enrolled in the Childhood Liver Disease Research and Education Network during RV season (December-May). Forty infants with biliary atresia (BA), age 62 ± 29 days (range, 4.7-13 weeks) and 38 infants with cholestasis, age 67 ± 44 days (range, 3-15.8 weeks) were enrolled. RESULTS: At enrollment, RV-A IgM positivity rates did not differ between infants with BA (10%) vs those without (18%) (P = .349). RV-C IgM was positive in 0% of infants with BA vs 3% in those without BA (P = .49). RV-A IgG was lower in infants with BA: 51 ± 39 vs 56 ± 44 enzyme-linked immunoassay unit, P = .045 but this difference may lack biological relevance as maternal RV-A IgG titers were similar between groups. Infant RV-A IgM titers at 2-6 months follow-up increased markedly vs at presentation in both infants with BA (50 ± 30 vs 9 ± 9) and those without (43 ± 18 vs 16 ± 20 enzyme-linked immunoassay unit) (P < .0001), without differences between groups. CONCLUSIONS: RV-A infection in the first 6 months of life is common in infants with cholestasis of any cause. RV-A could have different pathogenetic effects by initiating different hepatic immune responses in infants with vs without BA or could lack pathogenetic significance.

Incidence and Epidemiology of Intussusception among Infants in Ho Chi Minh City, Vietnam.

OBJECTIVE: To evaluate rates of intussusception hospitalization among infants in Vietnam before the introduction of rotavirus vaccine. STUDY DESIGN: Between 2009 and 2011, we identified intussusception hospitalizations among infants using the International Statistical Classification of Diseases and Related Health Problems, 10th Revision, Clinical Modification code K56.1 at 2 large pediatric hospitals in Ho Chi Minh City, Vietnam that treat most of the intussusception cases in the city. We reviewed all medical records to confirm a Brighton level 1 case definition for intussusception. RESULTS: We identified a total of 869 intussusception cases in Ho Chi Minh City during the 3-year study period, for an annual rate of 296 per 100,000 infants. The mean age of intussusception was ∼ 37 weeks (8.6 months), with <2% of the cases occurring before age 15 weeks. Cases of intussusception were observed year-round in these hospitals with no evident seasonal pattern. Ultrasonography was used to diagnose most cases (97%), and reduction was performed by air enema in >95% of the cases, with only 1% of cases at 1 hospital and 5% at the other hospital requiring surgical intervention. Ultrasound diagnosis was confirmed by an independent radiologist in 94% of a randomly selected group of intussusception cases at 1 of the 2 hospitals. No mortality was reported. CONCLUSION: Vietnam has a substantially higher rate of intussusception in children aged >15 weeks compared with most other regions of the world. Most of our cases were diagnosed by ultrasound, and only a small proportion required surgical intervention with no fatalities, suggesting that the higher rates may be related in part to better and earlier detection of intussusception.

The control of rotavirus gastroenteritis in the United States.

Since 2006, two new vaccines have been licensed to prevent rotavirus, the cause of 20% to 50% of severe acute gastroenteritis in young children worldwide. These vaccines have been implemented in national immunization programs in about 30 high- and middle-income countries, including the United States, and vaccine use has led to substantial decreases in diarrhea-related health care visits. In addition to reductions in diarrhea burden in vaccinated children, decreases have been observed in older, unvaccinated age groups in many settings, suggesting indirect benefits (i.e., herd immunity) from vaccination. Although the efficacy of these oral rotavirus vaccines is expectedly lower in developing countries in Asia and Africa, the public health benefits of vaccination in these settings, where more than 90% of the estimated 453,000 annual deaths from rotavirus occur, are likely to be substantial. Efforts continue to develop alternative rotavirus vaccines that could have a better efficacy and safety profile and may be less expensive.

Molecular epidemiology of group A rotavirus in Buenos Aires, Argentina 2004-2007: reemergence of G2P[4] and emergence of G9P[8] strains.

Detection and characterization of group A rotavirus in Buenos Aires, Argentina, was conducted on 710 fecal samples from children 0-15 years old collected between 2004 and 2007. Rotavirus was detected in 140 (19.7%) samples with G9P[8] (30.0%) and G2P[4] (21.4%) as the most common genotypes. Mixed (G and/or P) infections accounted for 17.9% of the samples and the emerging G12 strain was detected during 2004 (3.5%) and 2007 (2.5%). Genotype G2 was the most prevalent during 2004 (43.9%) and 2007 (57.5%) and G9 during 2005 (58.0%) and 2006 (61.5%). Analysis of genotype prevalences from studies performed since 1996 in the same area showed striking natural fluctuations in G and P genotype frequencies. In particular, G2P[4] strains disappeared after 1999 and reemerged in 2004 to become the predominant strain by 2007 with a concomitant major decrease in G1P[8] prevalence. The VP7 genes from Argentinian G9 and G2 strains were sequenced and phylogenetic analysis was conducted in order to compare with sequences from strains isolated in regional countries reported previously. Several changes in the deduced amino acid sequence in antigenic regions of the VP7 protein from Argentinian and Brazilian strains were identified compared to vaccine strains. Overall, this study revealed relationships in the circulation of rotavirus strains in South American countries and major replacements in dominant genotypes, including the virtual disappearance of G1P[8] strains in a non-vaccinated population. High numbers of mixed infections speeding up evolution, circulation of rare serotypes, and antigenic drift could, eventually, become challenges for new vaccines.

Detection and characterization of group C rotavirus in Buenos Aires, Argentina, 1997-2003.

The role of group C rotaviruses as a cause of diarrhea was examined among children <17 years of age admitted to a Hospital in a suburban area of Buenos Aires, Argentina between 1997 and 2003. A total of 1,579 fecal samples were screened for group A (RVA) and C (RVC) rotaviruses by two in-house ELISA methods at Quilmes University (UNQ-ELISA). Samples positive, doubtful and negative by RVC specific UNQ-ELISA (n = 246) were examined further for RVC by another in-house ELISA (CDC-ELISA), electron microscopy, RT-PCR, nested PCR, and Southern hybridization. Sensitivity, specificity, and predictive values for each test were determined. While the sensitivity was comparable for the nested PCR and CDC-ELISA methods (82.5%), the molecular methods were slightly more specific. Poorly preserved particles were often seen in fecal samples, suggesting that degradation of RNA could be a factor influencing the performance of molecular methods. The incidence of RVC was estimated to be 3% without apparent differences among seasons. RVC infected patients had a significantly (P < 0.001) higher median age (6 years vs. 1 year) than those with RVA infection. Sequence of the RVC VP7 gene from six Argentinean strains and sequences reported previously in different countries showed high nucleotide (94.4-99.9%) sequence identities, indicating a high degree of conservation for human RVC VP7 genes among strains collected on five continents over a period of 17 years. These findings indicate that RVC is a significant cause of diarrhea and it is necessary to develop simple and sensitive serological methods for its detection.

Characterization of genotype P[9]G12 rotavirus strains from Argentina: high similarity with Japanese and Korean G12 strains.

The circulation of the unusual P[9]G12 strains was previously reported in suburban Buenos Aires, Argentina and in Far Eastern Asian countries. To examine genetic relationships of these strains the genes coding VP7, VP4, and NSP1 from two Argentine, one Japanese and one Korean P[9]G12 isolates were sequenced and their overall genome relatedness was determined by liquid hybridization. In addition, liquid hybridization was used to compare this group of strains to the previous G12 isolates L26 and Se585, and prototype Wa, DS-1, and AU-1 strains. The genomes of the Argentinean, Japanese and Korean strains were virtually indistinguishable by hybridization assays, suggesting very high sequence relatedness for all 11 segments. Hybridization assays also demonstrated that these four strains belong to the AU-1 genogroup and that their genetic relationship with rotaviruses L26 and Se585 is limited to the VP7 gene. The VP7, VP4, and NSP1 genes of the Argentinean, Japanese and Korean strains were highly homologous to each other and to Thai strain T152 ( approximately 99% identity). These results together with the report of a similar strain detected during 2003 in Brazil are consistent with a recent importation and dissemination of the G12 strains from Far Eastern countries into South America. Increasing reports from several regions of the world demonstrating a variety of different G12 reassortant strains suggests that routine surveillance for this serotype should be conducted to determine its potential for global emergence.

Evidence for zoonotic transmission of group C rotaviruses among children in Belém, Brazil.

The prevalence and potential zoonotic transmission of group C rotavirus (RVC) were examined by testing fecal samples collected from children during a longitudinal study that was carried out in the outskirts of Belém, Brazil, from December 1982 to March 1986. The study involved a group of 30 children who were followed from birth to 3 years. Of the 77 samples tested from 29 children, 5 (6.5%) were positive for human and 3 (4%) for porcine RVC by using nested PCR assay with primers specific for VP6 gene of human or porcine RVC and by Southern hybridization using a probe specific for VP6 gene of both human and porcine RVC. In addition, a total of 59 fecal specimens from the 30th child were tested, 1 (1.7%) and 14 (23.7%) were positive for human and porcine RVC, respectively. Partial nucleotide sequences of VP6 gene demonstrated that the six human strains detected in Brazil were homologous with other human RVC, and 14 of the 17 porcine RVC strains examined showed a complete homology among themselves but differed slightly from the porcine Cowden strain, suggesting that a single porcine RVC strain was circulating in Belém. This study is the first to provide evidence for transmission of RVC from swine to human. They also indicate that both human and porcine RVC were endemic in Belém.