Prevalence of neutralizing antibodies against different rotavirus serotypes in children with severe rotavirus-induced diarrhea and their mothers

Effect of Infant and Maternal Secretor Status on Rotavirus Vaccine Take-An Overview

Histo-blood group antigens, which are present on gut epithelial surfaces, function as receptors or attachment factors and mediate susceptibility to rotavirus infection. The major determinant for susceptibility is a functional FUT2 enzyme which mediates the presence of α-1,2 fucosylated blood group antigens in mucosa and secretions, yielding the secretor-positive phenotype. Secretors are more susceptible to infection with predominant rotavirus genotypes, as well as to the commonly used live rotavirus vaccines. Difference in susceptibility to the vaccines is one proposed factor for the varying degree of efficacy observed between countries. Besides infection susceptibility, secretor status has been found to modulate rotavirus specific antibody levels in adults, as well as composition of breastmilk in mothers and microbiota of the infant, which are other proposed factors affecting rotavirus vaccine take. Here, the known and possible effects of secretor status in both infant and mother on rotavirus vaccine take are reviewed and discussed.

Overview of the Development, Impacts, and Challenges of Live-Attenuated Oral Rotavirus Vaccines

Safety, efficacy, and cost-effectiveness are paramount to vaccine development. Following the isolation of rotavirus particles in 1969 and its evidence as an aetiology of severe dehydrating diarrhoea in infants and young children worldwide, the quest to find not only an acceptable and reliable but cost-effective vaccine has continued until now. Four live-attenuated oral rotavirus vaccines (LAORoVs) (Rotarix^®, RotaTeq^®, Rotavac^®, and RotaSIIL^®) have been developed and licensed to be used against all forms of rotavirus-associated infection. The efficacy of these vaccines is more obvious in the high-income countries (HIC) compared with the low- to middle-income countries (LMICs); however, the impact is far exceeding in the low-income countries (LICs). Despite the rotavirus vaccine efficacy and effectiveness, more than 90 countries (mostly Asia, America, and Europe) are yet to implement any of these vaccines. Implementation of these vaccines has continued to suffer a setback in these countries due to the vaccine cost, policy, discharging of strategic preventive measures, and infrastructures. This review reappraises the impacts and effectiveness of the current live-attenuated oral rotavirus vaccines from many representative countries of the globe. It examines the problems associated with the low efficacy of these vaccines and the way forward. Lastly, forefront efforts put forward to develop initial procedures for oral rotavirus vaccines were examined and re-connected to today vaccines.

High-Frequency, Functional HIV-Specific T-Follicular Helper and Regulatory Cells Are Present Within Germinal Centers in Children but Not Adults

Broadly neutralizing antibodies (bnAbs) against HIV-1 are an effective means of preventing transmission. To better understand the mechanisms by which HIV-specific bnAbs naturally develop, we investigated blood and lymphoid tissue in pediatric infection, since potent bnAbs develop with greater frequency in children than adults. As in adults, the frequency of circulating effector T-follicular helper cells (TFH) in HIV infected, treatment naïve children correlates with neutralization breadth. However, major differences between children and adults were also observed both in circulation, and in a small number of tonsil samples. In children, TFH cells are significantly more abundant, both in blood and in lymphoid tissue germinal centers, than in adults. Second, HIV-specific TFH cells are more frequent in pediatric than in adult lymphoid tissue and secrete the signature cytokine IL-21, which HIV-infected adults do not. Third, the enrichment of IL-21-secreting HIV-specific TFH in pediatric lymphoid tissue is accompanied by increased TFH regulation via more abundant regulatory follicular T-cells and HIV-specific CXCR5+ CD8 T-cells compared to adults. The relationship between regulation and neutralization breadth is also observed in the pediatric PBMC samples and correlates with neutralization breadth. Matching neutralization data from lymphoid tissue samples is not available. However, the distinction between infected children and adults in the magnitude, quality and regulation of HIV-specific TFH responses is consistent with the superior ability of children to develop high-frequency, potent bnAbs. These findings suggest the possibility that the optimal timing for next generation vaccine strategies designed to induce high-frequency, potent bnAbs to prevent HIV infection in adults would be in childhood.

Rotavirus VP6 preparations as a non-replicating vaccine candidates

Rotavirus (RV) structural proteins VP4 and VP7, located on the surface of viral particles, elicit neutralizing antibodies (Abs) and are therefore considered to be important components of RV vaccines. However, despite inducing neutralizing Abs, limits of cross-neutralizing activity and lack of full correlation with protection limit the usefulness of these proteins as protective agents against RV disease. VP6 protein, which forms the middle layer of RV particles, is discussed as an alternative vaccine candidate since it can induce cross-protective immune responses against different RV strains although the Ab raised is not neutralizing. This report reviews different functions of VP6 that can lead to considering it as an alternative vaccine against RV disease.

A comparison of seasonal variations in rotavirus antibodies in the breast milk of Swedish and Bangladeshi mothers

AIM

The rotavirus has been identified as the most common cause of severe gastroenteritis in young children. This study compared the levels of rotavirus-specific antibodies in breast milk and serum samples in Swedish and Bangladeshi mothers to identify any seasonal variations.

METHODS

Breast milk and serum samples were collected from 69 Swedish and 52 Bangladeshi mothers during all months of the year. Sera were analysed for Immunoglobulin A (IgA) and Immunoglobulin G (IgG) titres and breast milk for secretory IgA (SIgA) antibody levels against rotavirus.

RESULTS

Significantly, higher SIgA antibody levels against rotavirus were found in breast milk from Bangladeshi than Swedish mothers (p < 0.0001). Seasonality of rotavirus antibody levels was only detected in breast milk from Swedish mothers, with samples collected during the spring having significantly higher rotavirus titres than samples collected during the autumn (p = 0.0203).

CONCLUSION

This study found significantly higher SIgA antibody levels against rotavirus in breast milk from Bangladeshi than Swedish mothers, together with a seasonal variation among Swedish mothers only. These results suggest that Swedish children who are being breastfed should ideally be vaccinated during seasons when the rotavirus antibody levels in breast milk are low.

Prevalence of rotavirus infection in children below two years presenting with diarrhea

BACKGROUND

Rotavirus is a common cause of diarrhea in children. There is a need for data on prevalence of rotavirus diarrhea especially in our setting. This study was carried out to determine the prevalence of rotavirus infection in children upto two years presenting with diarrhea and to ascertain factors associated with rotavirus infection in them.

METHODS

A cross sectional observational study was carried out to determine the prevalence of rotavirus infection amongst children less than 2 years presenting with diarrhea. The clinical profile of the children was analyzed along with detection of rotavirus antigen in stool.

RESULTS

A total of 250 children with diarrhea were included in the study. The Male: Female ratio was 0.97:1. We found 24% children presenting with diarrhea to be positive for rotavirus antigen. 78.3% of children with rotaviral diarrhea were in the age group of 6-15 months. There was a significant association between type of feeding and rotavirus diarrhea with reduced prevalence while on exclusive breast-feeding. Though only 10.4% of children with rotavirus diarrhea had severe dehydration, 61.5% of children with severe dehydration were positive for rotavirus.

CONCLUSION

Rotavirus diarrhea caused substantial morbidity in our study population. The rotavirus positivity in these children was 24% and there was a significant association of rotavirus infection with type of feeding and severity of dehydration.

Efficacy and immunogenicity of live-attenuated human rotavirus vaccine in breast-fed and formula-fed European infants

BACKGROUND

Rotavirus is the main cause of severe gastroenteritis and diarrhea in infants and young children less than 5 years of age. Potential impact of breast-feeding on the efficacy and immunogenicity of human rotavirus G1P[8] vaccine was examined in this exploratory analysis.

METHODS

Healthy infants (N = 3994) aged 6-14 weeks who received 2 doses of human rotavirus vaccine/placebo according to a 0-1 or 0-2 month schedule were followed for rotavirus gastroenteritis during 2 epidemic seasons. Rotavirus IgA seroconversion rate (anti-IgA antibody concentration ≥ 20 mIU/mL) and geometric mean concentrations were measured prevaccination and 1-2 months post-dose 2. Vaccine efficacy against any and severe rotavirus gastroenteritis was analyzed according to the infants being breast-fed or exclusively formula-fed at the time of vaccination.

RESULTS

Antirotavirus IgA seroconversion rate was 85.5% (95% confidence interval [CI]: 82.4-88.3) in breast-fed and 89.2% (95% CI: 84.2-93) in exclusively formula-fed infants; geometric mean concentrations in the respective groups were 185.8 U/mL (95% CI: 161.4-213.9) and 231.5 U/mL (95% CI: 185.9-288.2). Vaccine efficacy was equally high in breast-fed and exclusively formula-fed children in the first season but fell in breast-fed infants in the second rotavirus season. During the combined 2-year efficacy follow-up period, vaccine efficacy against any rotavirus gastroenteritis was 76.2% (95% CI: 68.7-82.1) and 89.8% (95% CI: 77.6-95.9) and against severe rotavirus gastroenteritis 88.4% (95% CI: 81.6-93) and 98.1% (95% CI: 88.2-100) in the breast-fed and exclusively formula-fed infants, respectively.

CONCLUSIONS

The difference in immunogenicity of human rotavirus vaccine in breast-fed and exclusively formula-fed infants was small. Vaccine efficacy was equally high in breast-fed and exclusively formula-fed children in the first season. Breast-feeding seemed to reduce slightly the efficacy in the second season.

Identification of an antibody-binding epitope on the rotavirus A non-structural protein NSP2 using phage display analysis

The non-structural protein 2 (NSP2) of rotavirus has important roles in rotavirus replication associated with RNA binding, hydrolysis of NTPs and RNA, and helix destabilizing properties. A cell-culture assay using an NSP2-specific mAb and polyclonal antiserum to block virus replication showed a 73 and 96 % reduction in the amount of virus produced during replication, respectively. Phage display technology was used to identify the antibody-binding region on the NSP2 protein with the motif (244)T-(Y/F)-Ø-Ø-Ø-X-K-Ø-G(252), where Ø is a hydrophilic residue and X is any amino acid. This region was mapped to the three-dimensional NSP2 crystal structure to visualize the epitope. Analysis revealed identity to a region on NSP2 that mapped to a site exposed on the surface of the protein, which could possibly interfere with a functionally important region of the protein. Antibody binding to this region could disrupt the essential roles of NSP2, such as the formation of viroplasms with NSP5 or the interaction with viral RNA, thereby indicating a possible mechanism for the observed inhibition of virus replication. Genetic analysis of the putative binding region of NSP2 revealed a high level of conservation, suggesting that the region is under strict control.

Breastfeeding and the risk of rotavirus diarrhea in hospitalized infants in Uganda: a matched case control study

BACKGROUND

Rotavirus is responsible for over 25 million outpatient visits, over 2 million hospitalizations and 527,000 deaths annually, worldwide. It is estimated that breastfeeding in accordance with the World Health Organization recommendations would save 1.45 million children's lives each year in the developing countries. The few studies that examined the effect of breastfeeding on rotavirus diarrhea produced conflicting results. This study aimed to determine the effect of breastfeeding on rotavirus diarrhea among admitted infants in Uganda.

METHODS

The study was conducted in the Pediatrics medical emergency unit of a National Referral hospital during a peak incidence time for rotavirus from February to April 2008. It was an age matched case-control study with a ratio of 1:1. We consecutively enrolled infants presenting at the study site during this period whose caretakers consented to participate in the study. A minimum sample size of 90 pairs was adequate with power of 80% to detect a 30% decrease in breastfeeding rate among the cases assuming a breastfeeding rate of 80% in the controls. The infants with rotavirus positive results were the "cases". We used the commercial enzyme immunoassay kit (DAKO IDEIA™ rotavirus EIA detection kit) to diagnose the cases. The "controls" were admitted children with no diarrhea. We compared the cases and controls for antecedent breastfeeding patterns.

RESULTS

Ninety-one matched case-control age-matched pairs with an age caliper of one month were included in the analysis. Breastfeeding was not protective against rotavirus diarrhea (OR 1.08: 95% CI 0.52 - 2.25; p = 0.8) in the conditional logistic model.

CONCLUSIONS

Our study findings did not reveal breastfeeding as protective against rotavirus diarrhea in infants. This suggests searching for other complementary preventive methods such as rotavirus vaccination and zinc supplementation to reduce the problem of rotavirus diarrhea in infants irrespective of their feeding practices.

Maternal antibodies to rotavirus: could they interfere with live rotavirus vaccines in developing countries?

INTRODUCTION

Past experience with live oral vaccines including licensed rotavirus vaccines demonstrates a trend towards reduced vaccine efficacy in developing countries compared with developed countries. The reasons behind this disparity are not well understood. Transplacental transfer of maternal antibodies and breast milk ingestion may attenuate vaccine responses in infants in developing countries where rotavirus infections are endemic, and maternal antibody levels are high. We examined the prevalence and level of rotavirus antibody in maternal and cord serum, colostrum and breast milk in a developing country setting.

METHODS

100 mother-infant pairs were prospectively recruited from December 2008 to February 2009 at Dr. Sardjito Hospital, Yogyakarta, Indonesia. Maternal and cord sera were collected during delivery. Colostrum and transitional breast milk were collected between day 0-3 and day 7-10 postpartum respectively. Rotavirus-specific IgA and IgG were estimated for all specimens and virus neutralization assays were conducted on a subset of milk specimens.

RESULTS

All maternal and cord serum samples were positive for rotavirus-specific IgG antibodies with a strong correlation between levels of rotavirus-specific IgG in mothers and levels transferred to infants in cord blood (r=0.86; p=0.001). 78% of colostrum and 67% of transitional breast milk specimens were positive for rotavirus-specific IgA. There was a median 4-fold decrease in rotavirus-specific IgA from colostrum to transitional breast milk. Neutralizing antibodies were present in 56% of colostrum specimens assayed (19/34) and in 41% of transitional milk specimens assayed (14/34).

CONCLUSIONS

Maternal serum and breast milk antibodies to rotavirus are highly prevalent in a developing country setting. Evaluation of the impact of maternal anti-rotavirus serum and breast milk antibody upon vaccine immunogenicity would help to inform rotavirus vaccination strategies, especially in developing settings.

Inhibitory effect of breast milk on infectivity of live oral rotavirus vaccines

BACKGROUND

Live oral rotavirus vaccines have been less immunogenic and efficacious among children in poor developing countries compared with middle income and industrialized countries for reasons that are not yet completely understood. We assessed whether the neutralizing activity of breast milk could lower the titer of vaccine virus and explain this difference in vitro.

METHODS

Breast milk samples were collected from mothers who were breast-feeding infants 4 to 29 weeks of age (ie, vaccine eligible age) in India (N = 40), Vietnam (N = 77), South Korea (N = 34), and the United States (N = 51). We examined breast milk for rotavirus-specific IgA and neutralizing activity against 3 rotavirus vaccine strains-RV1, RV5 G1, and 116E using enzyme immunoassays. The inhibitory effect of breast milk on RV1 was further examined by a plaque reduction assay.

FINDINGS

Breast milk from Indian women had the highest IgA and neutralizing titers against all 3 vaccine strains, while lower but comparable median IgA and neutralizing titers were detected in breast milk from Korean and Vietnamese women, and the lowest titers were seen in American women. Neutralizing activity was greatest against the 2 vaccine strains of human origin, RV1 and 116E. This neutralizing activity in one half of the breast milk specimens from Indian women could reduce the effective titer of RV1 by ∼2 logs, of 116E by 1.5 logs, and RV5 G1 strain by ∼1 log more than that of breast milk from American women.

INTERPRETATION

The lower immunogenicity and efficacy of rotavirus vaccines in poor developing countries could be explained, in part, by higher titers of IgA and neutralizing activity in breast milk consumed by their infants at the time of immunization that could effectively reduce the potency of the vaccine. Strategies to overcome this negative effect, such as delaying breast-feeding at the time of immunization, should be evaluated.

[Detection of a rotavirus G9P[8] outbreak causing gastroenteritis in a geriatric nursing home]

INTRODUCTION

The aim of this study was to describe an outbreak of gastroenteritis due to rotavirus in a geriatric nursing home.

METHOD

Stool samples from 8 patients were studied. Antigen detection was carried out by ELISA, and molecular typing was performed by RT-PCR.

RESULTS

Rotavirus antigen was detected in 6 patients. Typing demonstrated a common genotype (G9P[8]).

CONCLUSION

The outbreak detected in elderly persons suggests a loss of immunity with age or a lack of protection against an emergent genotype.

First detection of G12 rotaviruses in newborns with neonatal rotavirus infection at all India Institute of Medical Sciences, New Delhi, India

Rotavirus genotype G12 strains were detected for the first time among newborns with asymptomatic rotavirus infection (74% of 39 rotavirus strains isolated from the infected infants were genotype G12) in the nursery of the All India Institute of Medical Sciences during a period from 2005 to 2006. Sequence analysis of the VP7 genes from these neonatal strains indicated a high level of homology to other G12 strains reported worldwide, suggesting the recent emergence of these strains in humans. Such nosocomial infections of newborns represent a potential source of introduction of novel rotavirus serotypes into the community.

Unexpected detection of simian SA11-human reassortant strains of rotavirus G3P[8] genotype from diarrhea epidemic among tribal children of Western India

This investigation is in continuation with the earlier studies on diarrhea epidemic due to rotavirus, that occurred at Jawhar western India, among tribal children during Dec 2000-Jan 2001 published by National Institute of Virology, Pune. Three rotavirus strains were isolated in cell culture from fecal specimens of affected children. Monoclonal antibody ELISA and RT-PCR typed the isolates as G3P [8]. Two isolates agglutinated guinea pig erythrocytes thereby indicating their animal origin. Antiserum against simian G3, SA11 neutralized both the isolates largely than antiserum against human G3 (YO). Nucleotide sequencing of VP7 gene, nested PCR product of three isolates, and two original fecal specimens showed 100% identity with both simian G3, SA11 prototype and ROSVP7, SA11 strains whereas, lower identity (82%) with human G3 (YO) strain. Partial sequence analysis of the VP4 gene of fecal specimen FS-006964 & isolate I-006964 showed 99% identity with G1P[8] strain, while 80% identity with simian G3P[2], SA11 strain. Thus, the strains appeared to be reassortants between human and simian origin. Serological studies further supported the identity of the causative agent as simian G3, SA11 like strains. Neutralizing antibody titers at very low level against simian G3, SA11 as well as human G3 (YO) strains among the population at Jawhar suggested an overall lack of immunity against the virus. Seroconversion against simian G3, SA11 was shown by six out of seven child patients. Thus, simian G3, SA11 like strains are claimed for the first time as etiological agents of diarrhea in humans.

Dual infection due to simian G3—human reassortant and human G9 strains of rotavirus in a child and subsequent spread of serotype G9, leading to diarrhea among grandparents

Cultivation of rotavirus from day 1 and 3 fecal specimens of a child yielded simian SA11-human reassortant, G3P[8] and AU32 like G9P[8] rotavirus strains, respectively. Diarrhea developed in the grandfather by sheer hospital visits, and in the grandmother, after wiping the vomit of the grandfather. AU32 like G9 strains were isolated from the grandparents also. Rotavirus specific IgM developed in all the three patients. A fourfold rise in G9 neutralizing antibodies was observed in the child and grandmother. The child's mother had asymptomatic rotavirus infection. The study highlights the potential of G9 serotype to spread from children to adults.

Evidence of rotavirus AU32 like G9 strains from nontypeable fecal specimens of Indian children hospitalized during 1993-1994

Serotyping of 432 rotavirus positive fecal specimens collected from hospitalized children during 1990-1997 was carried out at National Institute of Virology (NIV), Pune, India, using monoclonal antibodies (MAbs) directed against VP7 determinant of serotypes G1-G4, G6, G8, and G10. However, significant number of specimens, that is, 47.92% remained nontypeable. The aim of the present study was to culture adapt the nontypeable specimens and to characterize them further. Since the fecal specimens were not tested by MAb to G9 serotype, which has emerged as an important serotype infecting humans recently, presence of G9 serotype was expected in nontypeable specimens. Therefore, we selected specimens from those children, who showed higher neutralizing antibody (NAb) titer in their convalescent serum samples to G9 serotype than their mothers. Out of six isolates having long electropherotype, five isolates showed subgroup II, and one showed subgroup I, II. The isolates were confirmed as G9 by MAb based ELISA, neutralization assay, and PCR. The G9 specific nested PCR products of four isolates showed 96-99% identities to AU32 G9 strain reported from Japan. P type of four isolates was determined as P8. Besides isolates, four additional nontypeable fecal specimens were confirmed as G9 by MAb based ELISA. Thus, 10 (28.57%) out of 35 nontypeable specimens were identified as rotavirus serotype G9. The results indicate that serotype G9 may represent significant proportion of specimens, which were previously nontypeable.