Association of serum antibodies with protection against rotavirus infection and disease in South Indian children

VP4-Specific IgA level as a correlate of neutralizing antibody and fecal shedding of porcine rotavirus infection

Rotavirus (RV) causes diarrhea in children, infants, and young animals globally, with public health implications. Porcine rotavirus (PoRV) leads to economic losses in swine farming. Neutralizing antibodies (NAb) are vital for protecting piglets from intestinal infections. However, which serum and mucosal markers correlate with NAbs against PoRV and relate to post-infection fecal shedding remains unclear, crucial for pathogen-specific detection. We used indirect ELISA to measure IgG/IgA in sera, sIgA in colostrum from recovered pigs, and feces from diarrheal piglets against VP4*, VP7*, VP6, and NSP4*. Analyses showed specific IgA/sIgA levels correlated better with NAb titers than IgG. Among them, VP4*-specific IgA/sIgA had the highest positive correlation with NAb titers in sera (R = 0.848, P < 0.0001) and colostrum (R = 0.865, P < 0.0001). Also, VP4*-specific IgA/sIgA in sera (R= -0.446, P < 0.001) and feces (R= -0.497, P < 0.0001) had the strongest inverse relationship with viral RNA load. Piglet passive protection tests confirmed VP4*-specific IgA's high neutralizing capacity, highly correlated with NAb titers (R = 0.858, P < 0.0001), reducing viral shedding. In conclusion, mucosal IgA/sIgA responses to VP4 are important for PoRV diagnosis assays and vaccine efficacy evaluation.

Correlates of immune protection against human rotaviruses: natural infection and vaccination

Species A rotaviruses are the leading viral cause of acute gastroenteritis in children under 5 years of age worldwide. Despite progress in the characterization of the pathogenesis and immunology of rotavirus-induced gastroenteritis, correlates of protection (CoPs) in the course of either natural infection or vaccine-induced immunity are not fully understood. There are numerous factors such as serological responses (IgA and IgG), the presence of maternal antibodies (Abs) in breast milk, changes in the intestinal microbiome, and rotavirus structural and non-structural proteins that contribute to the outcome of the CoP. Indeed, while an intestinal IgA response and its surrogate, the serum IgA level, are suggested as the principal CoPs for oral rotavirus vaccines, the IgG level is more likely to be a CoP for parenteral non-replicating rotavirus vaccines. Integrating clinical and immunological data will be instrumental in improving rotavirus vaccine efficacy, especially in low- and middle-income countries, where vaccine efficacy is significantly lower than in high-income countries. Further knowledge on CoPs against rotavirus disease will be helpful for next-generation vaccine development. Herein, available data and literature on interacting components and proposed CoPs against human rotavirus disease are reviewed, and limitations and gaps in our knowledge in this area are discussed.

Efficacy of Microencapsulated Probiotic as Adjunct Therapy on Resolution of Diarrhea, Copper-Zinc Homeostasis, Immunoglobulins, and Inflammatory Markers in Serum of Spontaneous Rotavirus-Infected Diarrhoetic Calves

The objective of this study was to assess the efficacy of a microencapsulated probiotic as an adjunct therapy in rotavirus-positive diarrhea of neonatal calves that received supportive treatment or supportive along with microencapsulated probiotic treatment, for 5 days. We examined whether microencapsulated Lactobacillus acidophilus NCDC15 probiotic treatment in rotavirus-infected diarrhoetic calves led to faster resolution of diarrhea, amelioration of zinc-copper imbalance, improved the immunoglobulin A and immunoglobulin G, and decreased the inflammatory markers in serum. Calves with rotavirus-positive diarrhea < 4-week age and fecal scores ≥ 2 were randomly assigned into two groups. The supportive along with microencapsulated probiotic treatment significantly (p < 0.05) increased zinc and immunoglobulin A concentrations and decreased copper, tumor necrosis factor-α, and nitric oxide level in serum on days 3 and 5 from pretreatment values; the immunoglobulin G concentration was elevated (p < 0.05) on day 5. The mean resolution time of abnormal fecal score was 5.3 and 3.3 days in supportive treatment and supportive along with microencapsulated probiotic groups, respectively, in log-rank Mantel-Cox test. The calves in the supportive along with microencapsulated probiotic treatment group had faster resolution of diarrhea than supportive treatment group in Dunn's multiple comparisons test. This study demonstrates that supportive treatment along with microencapsulated probiotic administered to naturally rotavirus-infected diarrhoetic calves at onset of diarrhea led to faster resolution of diarrhea, improved zinc and immunoglobulin levels, and decreased the inflammatory parameters in serum of rotavirus-infected diarrhoetic calves.

Plasma VP8∗-Binding Antibodies in Rotavirus Infection and Oral Vaccination in Young Bangladeshi Children

BACKGROUND

Despite the availability and success of live-attenuated oral vaccines, rotavirus (RV) remains the leading cause of pediatric gastroenteritis worldwide. Next-generation vaccines targeting RV VP8∗ are under evaluation, but the role of VP8∗-specific antibodies in human immunity to RV and their potential as immune correlates of protection remains underexplored.

METHODS

We measured plasma RV VP8∗-binding antibodies in 2 cohorts of young children in Dhaka, Bangladesh. Plasma from a cohort study of 137 unvaccinated children aged 6-24 months old hospitalized with acute gastroenteritis was assessed for VP8∗ antibody seropositivity. VP8∗ antibodies were compared with the current standard for RV immunity, total RV-specific IgA (RV-IgA). Additionally, VP8∗ antibody responses were measured as part of an immunogenicity trial of a monovalent, oral, live-attenuated RV vaccine (Rotarix).

RESULTS

Fewer children with acute RV gastroenteritis were seropositive for VP8∗-binding IgA or IgG antibodies at hospital admission compared with RV-IgA, suggesting that the absence of VP8∗-binding antibodies more accurately predicts susceptibility to RV gastroenteritis than RV-IgA in unvaccinated children. However, when present, these antibodies appeared insufficient to protect fully from disease and no threshold antibody level for protection was apparent. In vaccinated children, these antibodies were very poorly induced by Rotarix vaccine, suggesting that VP8∗-specific antibodies alone are not necessary for clinical protection following oral vaccination.

CONCLUSIONS

This work suggests that VP8∗-binding antibodies may not be sufficient or necessary for protection from RV gastroenteritis following prior RV infection or oral vaccination; the role of VP8∗ antibodies induced by parenteral vaccination with non-replicating vaccines remains to be determined.

Duration and Density of Fecal Rotavirus Shedding in Vaccinated Malawian Children With Rotavirus Gastroenteritis

Quantifying rotavirus shedding among vaccinated individuals will aid understanding of vaccine indirect effects. Serial stool samples were collected from 196 children who presented with rotavirus gastroenteritis to health facilities in Blantyre, Malawi, and were tested for rotavirus using a VP6 semi-quantitative, real-time polymerase chain reaction. The median duration of fecal shedding was 28 days (95% CI, 19–28). The median copy numbers for peak shedding were 1.99 × 10⁷ (interquartile range, 3.39 × 10⁶ to 6.37 × 10⁷). The fecal viral load was positively associated with disease severity and negatively associated with serum anti-rotavirus immunoglobin A. High and persistent rotavirus shedding among vaccinated children with breakthrough disease may contribute to ongoing transmission in this setting.

Postvaccination Serum Antirotavirus Immunoglobulin A as a Correlate of Protection Against Rotavirus Gastroenteritis Across Settings

BACKGROUND

A correlate of protection for rotavirus gastroenteritis would facilitate rapid assessment of vaccination strategies and the next generation of rotavirus vaccines. We aimed to quantify a threshold of postvaccine serum antirotavirus immunoglobulin A (IgA) as an individual-level immune correlate of protection against rotavirus gastroenteritis.

METHODS

Individual-level data on 5074 infants in 9 GlaxoSmithKline Rotarix Phase 2/3 clinical trials from 16 countries were pooled. Cox proportional hazard models were fit to estimate hazard ratios (HRs) describing the relationship between IgA thresholds and occurrence of rotavirus gastroenteritis.

RESULTS

Seroconversion (IgA ≥ 20 U/mL) conferred substantial protection against any and severe rotavirus gastroenteritis to age 1 year. In low child mortality settings, seroconversion provided near perfect protection against severe rotavirus gastroenteritis (HR, 0.04; 95% confidence interval [CI], .01-.31). In high child mortality settings, seroconversion dramatically reduced the risk of severe rotavirus gastroenteritis (HR, 0.46; 95% CI, .25-.86). As IgA threshold increased, risk of rotavirus gastroenteritis generally decreased. A given IgA threshold provided better protection in low compared to high child mortality settings.

DISCUSSION

Postvaccination antirotavirus IgA is a valuable correlate of protection against rotavirus gastroenteritis to age 1 year. Seroconversion provides an informative threshold for assessing rotavirus vaccine performance.

Updates on immunologic correlates of vaccine-induced protection

Correlates of protection (CoPs) are increasingly important in the development and licensure of vaccines. Although the study of CoPs was initially directed at identifying a single immune function that could explain vaccine efficacy, it has become increasingly clear that there are often multiple functions responsible for efficacy. This review is meant to supplement prior articles on the subject, illustrating both simple and complex CoPs.

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

Background

Rotavirus (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.

Methods

Infants 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.

Results

Among 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).

Conclusions

RV-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 Registration

NCT01375647.

Naturally Acquired Immunity Against Rotavirus Infection and Gastroenteritis in Children: Paired Reanalyses of Birth Cohort Studies

Background

Observational studies in socioeconomically distinct populations have yielded conflicting conclusions about the strength of naturally acquired immunity against rotavirus gastroenteritis (RVGE), mirroring vaccine underperformance in low-income countries. We revisited birth cohort studies to understand naturally acquired protection against rotavirus infection and RVGE.

Methods

We reanalyzed data from 200 Mexican and 373 Indian children followed from birth to 2 and 3 years of age, respectively. We reassessed protection against RVGE, decomposing the incidence rate into the rate of rotavirus infection and the risk of RVGE given infection, and tested for serum antibody correlates of protection using regression models.

Results

Risk for primary, secondary, and subsequent infections to cause RVGE decreased per log-month of age by 28% (95% confidence interval [CI], 12%-41%), 69% (95% CI, 30%-86%), and 64% (95% CI, -186% to 95%), respectively, in Mexico City, and by 10% (95% CI, -1% to 19%), 51% (95% CI, 41%-59%) and 67% (95% CI, 57%-75%), respectively, in Vellore. Elevated serum immunoglobulin A and immunoglobulin G titers were associated with partial protection against rotavirus infection. Associations between older age and reduced risk for RVGE or moderate-to-severe RVGE given infection persisted after controlling for antibody levels.

Conclusions

Dissimilar estimates of protection against RVGE may be due in part to age-related, antibody-independent risk for rotavirus infections to cause RVGE.

Correlates of protection for enteric vaccines

An immunological Correlate of Protection (CoP) is an immune response that is statistically interrelated with protection. Identification of CoPs for enteric vaccines would help design studies to improve vaccine performance of licensed vaccines in low income settings, and would facilitate the testing of future vaccines in development that might be more affordable. CoPs are lacking today for most existing and investigational enteric vaccines. In order to share the latest information on CoPs for enteric vaccines and to discuss novel approaches to correlate mucosal immune responses in humans with protection, the Foundation Mérieux organized an international conference of experts where potential CoPs for vaccines were examined using case-studies for both bacterial and viral enteric pathogens. Experts on the panel concluded that to date, all established enteric vaccine CoPs, such as those for hepatitis A, Vi typhoid and poliovirus vaccines, are based on serological immune responses even though these may poorly reflect the relevant gut immune responses or predict protective efficacy. Known CoPs for cholera, norovirus and rotavirus could be considered as acceptable for comparisons of similarly composed vaccines while more work is still needed to establish CoPs for the remaining enteric pathogens and their candidate vaccines. Novel approaches to correlate human mucosal immune responses with protection include the investigation of gut-originating antibody-secreting cells (ASCs), B memory cells and follicular helper T cells from samples of peripheral blood during their recirculation.

Skin Vaccination against Rotavirus Using Microneedles: Proof of Concept in Gnotobiotic Piglets

Live-attenuated oral rotavirus (RV) vaccines have lower efficacy in low income countries, and additionally are associated with a rare but severe adverse event, intussusception. We have been pursuing the development of an inactivated rotavirus vaccine (IRV) using the human rotavirus strain CDC-9 (G1P[8]) through parenteral immunization and previously demonstrated dose sparing and enhanced immunogenicity of intradermal (ID) unadjuvanted IRV using a coated microneedle patch in comparison with intramuscular (IM) administration in mice. The aim of this study was to evaluate the immune response and protection against RV infection and diarrhea conferred by the administration of the ID unadjuvanted IRV using the microneedle device MicronJet600^® in neonatal gnotobiotic (Gn) piglets challenged with virulent Wa G1P[8] human RV. Three doses of 5 μg IRV when administered intradermally and 5 μg IRV formulated with aluminum hydroxide [Al(OH)₃] when administered intramuscularly induced comparable rotavirus-specific antibody titers of IgA, IgG, IgG avidity index and neutralizing activity in sera of neonatal piglets. Both IRV vaccination regimens protected against RV antigen shedding in stools, and reduced the cumulative diarrhea scores in the piglets. This study demonstrated that the ID and IM administrations of IRV are immunogenic and protective against RV-induced diarrhea in neonatal piglets. Our findings highlight the potential value of an adjuvant sparing effect of the IRV ID delivery route.

Changes in the Interstitial Cells of Cajal and Immunity in Chronic Psychological Stress Rats and Therapeutic Effects of Acupuncture at the Zusanli Point (ST36)

Now, chronic psychological stress (CPS) related diseases are increasing. Many CPS patients have gastrointestinal complaints, immune suppression, and immune imbalance. Increasing evidence is indicating that acupuncture (AP) at the Zusanli point (ST36) can alleviate functional gastrointestinal disorders (FGID), immune suppression, and immune imbalance. However, few studies have investigated the potential mechanisms. In this study, CPS rat models were established, and electroacupuncture (EA) at ST36 was done for CPS rats. Daily food intake, weight, intestinal sensitivity, the morphology of interstitial cell of Cajal (ICC) in the small intestine, and serum indexes were measured. The study found that, in CPS rats, EA at ST36 could improve food intake, weight, visceral hypersensitivity, and immunity; in CPS rats, in small intestine, the morphology of ICCs was abnormal and the number was decreased, which may be part causes of gastrointestinal motility dysfunction. EA at ST36 showed useful therapeutic effects. The mechanisms may be partially related to its repairing effects on ICCs damages; in CPS rats, there were immune suppression and immune imbalance, which may be part causes of visceral hypersensitivity. EA at ST36 showed useful therapeutic effects. The mechanisms may be partially related to its regulation on immunity.

Use of Pathogen-Specific Antibody Biomarkers to Estimate Waterborne Infections in Population-Based Settings

PURPOSE OF REVIEW

This review discusses the utility of pathogen-specific antibody biomarkers for improving estimates of the population burden of waterborne infections, assessing the fraction of infections that can be prevented by specific water treatments, and understanding transmission routes and the natural history and ecology of disease in different populations (including asymptomatic infection rates).

RECENT FINDINGS

We review recent literature on the application of pathogen-specific antibody response data to estimate incidence and prevalence of acute infections and their utility to assess the contributions of waterborne transmission pathways. Advantages and technical challenges associated with the use of serum versus minimally invasive salivary antibody biomarkers in cross-sectional and prospective surveys are discussed. We highlight recent advances and challenges and outline future directions for research, development, and application of antibody-based and other immunological biomarkers of waterborne infections.

Reinfection of adult cattle with rotavirus B during repeated outbreaks of epidemic diarrhea

Rotavirus B (RVB) infection in cattle is poorly understood. The objective of this study was to describe the epidemiological features of repeated outbreaks of epidemic diarrhea due to RVB infection in adult cattle on a large dairy farm complex in Japan. In October 2002, approximately 550 adult cows and approximately 450 in February 2005 had acute watery diarrhea at several farms on the complex. Four months before the first outbreak, RVB antibody-positive rates at subsequently affected farms were significantly lower than at non-affected farms (30% to 32% versus 61% to 67%). During the acute phase of both outbreaks, RVB antibody-positive rates in diarrheal cows tested were as low as 15% to 26%. Most of the farms affected in the second outbreak were also involved in the first outbreak. Some adult cows with RVB diarrhea in the first outbreak showed not only RVB seroresponse, but also RVB shedding in the second outbreak, although none of these cows developed diarrhea. Nucleotide sequences of the VP7 and VP4 genes revealed a close relationship between RVB strains in both outbreaks. Taken together, these results indicate that outbreaks of epidemic RVB diarrhea in adult cows might be influenced by herd immunity and could occur repeatedly at the same farms over several years. To our knowledge, this is the first report on repeated RVB infections in the same cattle.