Rotavirus neutralisation by human milk

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.

The secretory IgA system in the neonatal period

It is still not known when the secretory IgA response, important for defence of the mucous membranes, becomes fully competent in the human infant. The infant is, however, provided with 0.25--0.5 g of secretory IgA/day via the maternal milk. The milk contains secretory IgA antibodies against a wide variety of antigens from microorganisms, including bacteria, viruses and parasites. Many of the antibodies are directed against important virulence factors such as bacterial pili, enterotoxins, capsular polysaccharides and endotoxic lipopolysaccharides. The passive transfer of antibodies through the milk may explain why breast-fed infants are resistant to enteric infections in particular. The antibodies in the milk are often directed against antigens in the mother's milieu and intestine. An entero-mammary gland link, possibly consisting of lymphoid cells homing from the Peyer's patches in the intestine to the mammary gland, has been suggested. A limited selective uptake of oligomeric IgA from serum in exocrine glands, including the mammary glands, has also been indicated. Whichever the mechanism, the antibodies transferred via breast milk are composed to meet the needs of the infant.

A study on delayed hypersensitivity to rotavirus in infancy and childhood

The T-cell responsiveness to rotavirus antigen and phytohaemagglutinin (PHA) together with T-cell total and subsets quantitation was carried out in 50 non-diarrhoeal and six rotavirus diarrhoeal subjects. All individuals in the non-diarrhoeal group responded well to PHA and had normal values for T-cell subsets. The number of positive responders to the rotavirus antigen increased gradually from 0% in the newborns to 92% in older children. The increasing risk of exposure to rotavirus infection is thought to be a chief cause of this age-related variation. All the rotavirus diarrhoeal patients responded well to the rotavirus antigen, indicating a potent test system. The T-cell responses to PHA and the T-cell subsets were significantly low. This could be due to temporary T-cell suppression that may accompany viral infection. Our results are discussed in the context of previous studies.

Antibodies to seven rotavirus serotypes in cord sera, maternal sera, and colostrum of German women

Forty percent of colostrum samples from German women showed neutralizing antibody titers of greater than or equal to 50 to rotavirus (RV) serotypes 1, 3, 4, and 6. Antibody to serotypes 2, 8, and 9 was less prevalent. Titers are, however, too low to indicate an important effect of colostrum on the RV vaccine take rate. On the other hand, about 50% of the cord serum samples showed high neutralizing-antibody titers to serotypes 1, 3, and 4, which could interfere with the take rate of RV vaccines based on these serotypes in very young infants.

Observations questioning a protective role for breast-feeding in severe rotavirus diarrhea

To investigate whether breast-feeding protects children against rotavirus diarrhea (RVD), we compared rates of breast-feeding by age and enteric pathogens among 2,276 children with diarrhea 0-4 years of age who attended a diarrhea hospital in Bangladesh. Infants 0-5 months were less likely to be breast-fed than children 6-11 months of age suggesting that some protection against diarrhea with all agents was associated with early breast-feeding. In every age group studied, breast-feeding was more common among children with RVD than among children with non-RVD whereas it was less common among children with cholera and shigellosis. Twenty percent of breast milks consumed by infants less than 1 year of age had high levels of neutralizing activity (greater than or equal to 320) to the Wa strain of rotavirus but this activity did not appear to be protective since the 30 infants with RVD consumed milk which had titers that did not differ significantly from those consumed by 44 infants with diarrhea of other cause. Despite the prolonged breast-feeding which is common in Bangladesh, the mean age of hospitalization with RVD is approximately the same as in countries where the duration of breast-feeding is quite short. None of these 3 independent observations support a protective role for breast-feeding against rotavirus diarrhea after the first months of life.

Involvement of infants, children, and adults in a rotavirus gastroenteritis outbreak in a kibbutz in southern Israel

An outbreak of acute gastroenteritis in a kibbutz in southern Israel, characterized by diarrhea, fever, vomiting, and abdominal pain, involved 32 kibbutz members of all ages. Nineteen percent of the children and 3.5% of the adults were ill. Transmission of the illness occurred in direct proportion to the degree of close contact, involving first infants, then mothers and nursery staff, and only later youngsters, adolescents, and fathers. Stool samples obtained from 32 kibbutz members with clinical illness and from 44 asymptomatic close contacts were examined for the presence of rotavirus antigen. Fifty-six percent of symptomatic members were positive for rotavirus antigen as compared with 4.5% of asymptomatic close contacts. Positivity of stool samples correlated inversely with the number of days elapsed after onset of illness until the sample was obtained. Serologic studies carried out on acute and convalescent sera of symptomatic and asymptomatic subjects further supported a rotavirus etiology for the outbreak. RNA profiles of stool sample extracts obtained by polyacrylamide gel electrophoresis and silver staining indicate that one electropherotype may have been responsible for the outbreak.

Fluctuation of specific IgA antibodies in human milk

The concentration of secretory IgA and the levels of IgA specific antibodies against Escherichia coli labile-toxin, Shigella flexneri 6, and rotaviruses were determined in milk samples obtained serially from women during the first 16 weeks postpartum. The mean concentration of secretory IgA followed the expected pattern; the levels of specific antibodies fluctuated in an unpredictable manner and independently of milk secretory IgA content, becoming undetectable in many instances. Under some circumstances, continued breast-feeding may not guarantee continued intake of antibodies against intestinal pathogens by the breast-fed infant.

Epidemiological studies of parvovirus infections in calves on endemically infected properties

Bovine parvovirus serology and virus excretion were monitored in calves located on three endemically infected North Queensland properties. Maternally derived serum antibody to bovine parvovirus was found to have a half-life of 19 days. On all three properties, calves developed intestinal bovine parvovirus infection with seroconversion soon after weaning. This occurred more promptly where the environment was subject to heavier bovine parvovirus contamination due to management practices. The concurrent presence of moderate levels of residual serum antibody had only minor influence on the onset of the infection. On one beef cattle property, onset of intestinal bovine parvovirus infection was associated with an outbreak of post-weaning diarrhoea. Anthelmintic treatment trials indicated that this syndrome was unrelated to helminth burdens, though coccidiosis appeared responsible for occasional subsequent cases of dysentery. It was considered that bovine parvovirus may have significantly contributed to the development of the diarrhoea syndrome, in conjunction with substantial weaning stresses.

Protection against rotavirus-induced gastroenteritis in a murine model by passively acquired gastrointestinal but not circulating antibodies

Newborn mice suckled on dams immunized either orally or parenterally with primate rotavirus SA-11 were protected against diarrhea induced by SA-11 virus challenge. Experimental oral administration of milk from orally immunized dams protected suckling mice against challenge; protective activity was detected both in the anti-rotavirus immunoglobulin A (IgA) and IgG fractions, but IgA was more potent in vivo than IgG. Oral administration of milk from parentally immunized dams also protected suckling mice against challenge; in this case, protective activity was detected in the anti-rotavirus IgG fraction. In newborn mice foster-nursed by seronegative dams, circulating rotavirus-specific antibodies in high titer did not protect mice against oral SA-11 virus challenge. It appears that the most effective rotavirus vaccine will be that which induces an efficient production of antibodies active at the intestinal cell surface.

Epidemiological studies of parvovirus infections in calves on endemically infected properties

Bovine parvovirus serology and virus excretion were monitored in calves located on three endemically infected North Queensland properties. Maternally derived serum antibody to bovine parvovirus was found to have a half-life of 19 days. On all three properties, calves developed intestinal bovine parvovirus infection with seroconversion soon after weaning. This occurred more promptly where the environment was subject to heavier bovine parvovirus contamination due to management practices. The concurrent presence of moderate levels of residual serum antibody had only minor influence on the onset of the infection. On one beef cattle property, onset of intestinal bovine parvovirus infection was associated with an outbreak of post-weaning diarrhoea. Anthelmintic treatment trials indicated that this syndrome was unrelated to helminth burdens, though coccidiosis appeared responsible for occasional subsequent cases of dysentery. It was considered that bovine parvovirus may have significantly contributed to the development of the diarrhoea syndrome, in conjunction with substantial weaning stresses.

Serotypic characterization of rotaviruses derived from asymptomatic human neonatal infections

Nineteen rotavirus strains derived from asymptomatic neonates (seven from England, five from Australia, two from Venezuela, and five from Sweden) were successfully cultivated in primary African green monkey kidney cell cultures, serotyped by plaque reduction neutralization tests, subgrouped by indirect enzyme-linked immunosorbent assay, and electropherotyped by polyacrylamide gel electrophoresis. All 19 strains were shown to fall into one of the four known human serotypes; serotype 1 (all Venezuelan strains), serotype 2 (all Swedish strains), serotype 3 (all Australian strains), or serotype 4 (all English strains). Hyperimmune guinea pig serum raised against the Venezuelan strain (M37) neutralized not only serotype 1 (strain Wa) but also serotype 4 (strain St. Thomas no. 3) viruses to a similar degree. The English, Australian, and Venezuelan isolates were found to belong to subgroup 2, and the Swedish strains were subgroup 1 viruses. The potential importance of these rotaviruses obtained from neonates as possible vaccine candidates is discussed.

Influence of breast milk on nosocomial rotavirus infections in infants

To prevent nosocomial rotavirus infections in hospitalized children with various non-gastrointestinal diseases, 30 children (mean age five months) received 200 ml of fresh human milk per day in addition to the normal diet for their age. A matched group of children on formula diet served as a control. Fecal samples were routinely screened for rotavirus by a commercial ELISA test. In stools containing rotavirus, the virus RNA segments were analysed by gel electrophoresis to identify the different rotavirus strains. Clinical symptoms were recorded daily and quantified by a score system. Human milk had no effect on the frequency of nosocomial rotavirus infections: ten infected children were fed with human milk and seven were not. However, the severity of the clinical symptoms was clearly reduced: the mean score of clinical symptoms was only half as great and the number of mild or asymptomatic infections was doubled in the group receiving fresh human milk.

Etiologie des gastroentérites du nouveau-né au centre hospitalier d'Amiens

An epidemiological study has been carried on at the Amiens' Gynecology-Obstetrical center with the aim to determinate the aetiology of acute gastrointestinal disorders who affected part of the newborns over a two months period. Rotavirus was found in 16 babies (33 %) by electronmicroscopy and Enzyme-linked-Immuno-sorbent-Assay (ELISA). In one case, a « small round viruswas associated with the Rotavirus. Enteropathogenic bacteria were isolated only two times in this syndrom. The infection seem to releave of nosocomial contamination.

Neonatal rotavirus infection: role of lacteal neutralising alpha1-anti-trypsin and nonimmunoglobulin antiviral activity in protection

Expressed breast milks (EBMs) were collected from mothers of rotavirus (RV)-excreting babies and from mothers whose babies were RV free during an outbreak of asymptomatic RV infection in a newborn nursery to determine the role of lacteal anti-RV neutralising activity, alpha1-anti-trypsin activity, and nonimmunoglobulin antiviral factor in protection of neonates from RV infection, and although all of the above factors were present in the majority of the EBMs, no correlation could be found between their presence in EBM and protection from RV infection. A significant rise in both neutralising activity and subgroup 2 antibodies, was demonstrated in the EBM of one mother who experienced a subgroup 2 RV-associated diarrhoea during lactation. However, the alpha1-anti-trypsin activity and the nonimmunoglobulin antiviral levels remained the same. The importance of these factors in passive immunity with reference to virus dose is discussed.

Etude épidémiologique de gastroentérites infantiles d'origine virale dans la région amienoise

A systematic survey was carried on stools from 130 children suffering of acute gastroenteritis. Electron microscopy, enzymo-linked immunosorbent assay (ELISA) and counter electrophoresis were employed. This survey allowed to the detection by electron microscopy of Rotavirus (40 cases), Coronaviruses (3 cases), Astroviruses (2 cases), Adenoviruses (2 cases) and Small Round Viruses (1 case). Serological tests (complement fixation, ELISA and counter electrophoresis) done with 86 sera showed a good correlation with results obtained with electron microscopy.

Effect of fractions of Ethiopian And Norwegian colostrum on rotavirus and Escherichia coli heat-labile enterotoxin

Samples of colostrum from both Ethiopian and Norwegian women contained antirotavirus activities of immunoglobulin and non-immunoglobulin nature. No significant differences in rotavirus immunoglobulin A or in rotavirus-inhibiting activity were found between samples from the two countries. The non-immunoglobulin inhibitory activity was trypsin sensitive and heat stable (100 degrees C for 10 min). Escherichia coli heat-labile enterotoxin antibodies were measured in the colostrum samples by enzyme-linked immunosorbent assay. No E. coli enterotoxin-specific immunoglobulin A was detected, possibly due to the high background caused by the nonspecific adsorption of immunoglobulin A to the enzyme-linked immunosorbent assay plates in the absence of toxin. A total of 5 of 15 Ethiopian colostrum samples and 0 of 11 Norwegian colostrum samples neutralized the effect of E. coli heat-labile enterotoxin on YI adrenal cells. Both the Ethiopian and the Norwegian colostrum samples contained a non-immunoglobulin enterotoxin-inhibitory activity when the toxin was measured by enzyme-linked immunosorbent assay. This inhibitory activity was not trypsin sensitive, and extraction by chloroform-methanol indicated that the inhibitor was of a lipid nature.

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

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

Cord blood and breast-milk antibodies in neonatal rotavirus infection

Studies were carried out during an outbreak of rotavirus type 2 infection in a neonatal nursery to determine the protective role of antibodies in cord blood and breast milk. The range, distribution, and geometric mean titres of rotavirus-specific antibody in the cord blood were similar among rotavirus-positive and rotavirus-negative neonates, and the amount of virus excreted did not correlate with antibody levels. Despite the protective effect of breast feeding, the pattern of rotavirus-specific IgA and IgG antibodies in the expressed breast milk of mothers of babies who were rotavirus excreters and non-excreters was similar. Nevertheless, a higher proportion of expressed breast milk samples contained rotavirus-specific IgA group 2 (92%) and type 2 (97%) specific antibodies than type I (67%) antibodies, and the geometric mean titres of group 2 and type 2 specific antibodies were tenfold higher than type I antibodies. Among breast-fed babies who excreted rotavirus there was no correlation between type 2 rotavirus-specific IgA antibodies in expressed breast milk and the amount of neonatal virus excretion. These studies suggest that factors other than the rotavirus antibodies in expressed breast milk are of importance in preventing rotavirus infection in newborn infants.

The effect of human milk fractions on rotavirus in relation to the secretory IgA content

Human milk from healthy Norwegian women was fractionated by ammonium sulphate precipitation and gel filtration. The protein content, lactoferrin and secretory IgA were measured. Specific antirotavirus IgA, detected by indirect immunofluorescence was found in one out of five milk samples before fractionation, while a more concentrated immunoglobulin fraction from the other four milk samples contained such IgA. Before fractionation, 3 of 5 milk samples neutralized human rota-virus infection of LLC-MK2 cells, whereas concentrated, IgA-rich fractions of all 5 milk samples neutralized human rotavirus. Some fractions without detectable IgA also neutralized human rotavirus. This suggests that human milk contains rotavirus specific IgA as well as rotavirus neutralizing activity of non-immunoglobulin nature.

Antiviral activity of colostrum and serum immunoglobulins A and G

Enteric virus-specific IgA and IgG present in paired human sera and colostrums were measured by the enzyme-linked immunosorbent assay (ELISA). Virus-specific IgA was present in all colostrums, but virus-specific IgG could not be detected. The reverse was true when sera were assayed. Most of these colostrums also neutralized either polio virus or reovirus, as did IgA, which was separated from a pool of colostrums by exclusion chromatography. No correlation could be made between levels of neutralizing and ELISA antibody titers in colostrums.

A year's experience of the rotavirus syndrome and its association with respiratory illness

In a hospital study rotavirus was identified in 51% of 152 children with diarrhoea. These patients showed a clinical pattern that was distinct from patients in whom the diarrhoea was associated with bacteria, other viruses, or no pathogens. A respiratory illness was described in 66% of rotavirus patients and usually preceded the gastrointestinal symptoms. Vomiting lasted between one and 3 days and was curtailed by substituting the normal diet with clear fluids. Watery diarrhoes continued for 4 or 5 days, even when rehydration was by the intravenous rather than the oral route. Prolonged diarrhoea was rare. Most children infected with rotavirus were under 2 years of age, but dehydration was most severe in infants aged between 12 and 18 months. A clinician can thus recognise the rotavirus syndrome and expect spontaneous recovery if adequate rehydration is maintained for a critical few days.

Viruses in the stools

It has long been possible to isolate viruses from the stools by culture, though the viruses found are rarely implicated in disease of the gut. In contrast, only recently has it been possible to identify viruses in the stools of patients with diarrhoea. Initially, such identifications were made by electron microscopy but the unsuitability of the microscope for large-scale screening has led to the development of other methods. The new methods have concentrated on rotaviruses but other viruses are also implicated and an overall view of the significance of finding a virus in any stool specimen has to take into account the evidence about all viruses, old and new.

Asymptomatic endemic rotavirus infections in the newborn

Between May 1, 1976, and May 14, 1977, 343 (32.5%) of 1056 5-day-old babies in newborn nurseries excreted rotaviruses. The infection-rate was highest during winter (49%). 76% of infected babies at this time were bottle-fed. 41% of neonates excreted low amounts of virus (less than or equal to 10(8) particles/g faeces); older children tended to excrete greater than 10(10) particles/g faeces. Infected breast-fed babies excreted less virus than those who were bottle-fed. Stools of breast-fed babies often contained clumps of complete "smooth" rotavirus particles. When the newborn nurseries were transferred to a newly built hospital wing, infection appeared in the new wards, including those admitting only new patients, within a short period. Infection was either mild (8%) or symptomless (92%), and even babies with symptoms required no treatment.