A Z Kapikian

Protection against severe rotavirus diarrhoea by rhesus rotavirus vaccine in Venezuelan infants

The efficacy of the rhesus rotavirus vaccine candidate MMU-18006 was evaluated in a longitudinal double-blind field trial in Caracas, Venezuela. 247 infants aged 1-10 months were studied and followed for up to 1 year (201 completed the 1-year surveillance): 123 received a dose of 10(4) plaque-forming units of the vaccine orally and 124 received placebo. 21 episodes of rotavirus diarrhoea were detected, 16 in the controls and 5 in the vaccines: vaccine efficacy against any rotavirus diarrhoea was thus 68%. In the 1-5-month-old group the vaccine efficacy was 93%; only 1 episode of rotavirus diarrhoea was detected in 68 vaccinees and 15 such illnesses were observed in 65 controls (p less than 0.0001). For the entire study group vaccine efficacy was 100% against the most severe rotavirus diarrhoeal episodes.

Enzyme-linked immunosorbent assay (ELISA) for detection of human reovirus-like agent of infantile gastroenteritis.

An enzyme-linked immunosorbent assay (ELISA) was developed for the detection of the human reovirus-like agent of infantile gastroenteritis in human stools. The results of the assay can be read either with a simple colorimeter or the naked eye. Investigations with 143 samples from children with gastroenteritis and 75 samples from children with other illnesses showed that the ELISA was as sensitive as electron microscopy or radioimmunoassay for detection of this agent. In addition, the ELISA was simple to perform and, when read visually, did not require sophisticated technical equipment. These advantages make it suitable for field work.

Epidemiology of human rotavirus Types 1 and 2 as studied by enzyme-linked immunosorbent assay.

To determine the relative importance of two known serotypes of human rotavirus, we developed an enzyme-linked immunosorbent assay to differentiate serotype-specific rotavirus antigen and antibody. Using this technic, we studied the epidemiology of the two serotypes in acute gastroenteritis. Seventy-seven per cent of 414 rotavirus isolates were Type 2, and the remainder were Type 1. The serotype distribution was similar in specimens from children in Washington, D.C., and other parts of the world. Sero-epidemiologic studies revealed that most children living in the Washington, D.C., area acquired antibody to both types by the age of two years. An analysis of children who were reinfected indicated that sequential infections usually involved different serotypes and that illness caused by one serotype did not provide resistance to illness caused by the other serotype. These results suggest that, to be completely effective, a vaccine must provide resistance to both serotypes.

Field trial of rhesus rotavirus vaccine in infants.

Orally administered rhesus rotavirus vaccine (RRV) was evaluated in a placebo-controlled study in 176 infants (ages 2 to 4 months). Eighty-eight infants received a dose of 10(4) plaque-forming units of the vaccine, and 88 received the placebo. RRV was well-tolerated but mildly reactogenic in the 10 days after vaccination. There were mild febrile reactions (greater than or equal to 38 degrees C rectally) in 40% of the vaccinees and in 16% of the placebo recipients (P = 0.001). More of the vaccinees had loose stools than did the placebo recipients (P less than 0.05). RRV was immunogenic and induced a 4-fold or greater rise in serum neutralizing antibody responses in 67% of the vaccinees; however, breast-fed infants were less likely to develop a seroresponse than infants who were not breast-fed. Despite the good immunogenicity of RRV the overall incidence of rotavirus-associated illnesses was similar between the vaccine and placebo recipients. The failure of RRV in Rochester may be related to the fact that the circulating rotaviruses were predominantly serotype 1 and RRV is a serotype 3 rotavirus. Because the serotypes of rotavirus that predominate may vary from year to year, a polyvalent preparation may be necessary to provide effective vaccination against rotaviruses.

ENTEROTOXIGENIC ESCHERICHIA COLI AND REOVIRUS-LIKE AGENT IN RURAL BANGLADESH

48 patients admitted to a rural Bangladesh hospital with dehydration secondary to diarrhea were examined for infection caused by (R.L.A.) reovirus-like agent or (E.T.E.C.) enterotoxigenic Escherichia coli. The diagnosis of R.L.A. infection was established by electron microscopy of stool filtrates and by a 4-fold or greater rise in serum complement-fixing antibodies to the Nebraska calf diarrhea virus. Evidence of infection by heat-labile-toxin producing E.T.E.C. was sought by stool culture and serological testing using the adrenal cell tissue-culture system. Infection by heat-stable-toxin producing E.T.E.C. was sought by stool culture using the infant mouse test. 12 patients, all less than 2 years old, had evidence of R.L.A. infection, accounting for illness in 5% of the 22 patients under 2. None of these 22 had evidence of E.E.T.E.C. infection. R.L.A. diarrhea lasted 5-6 days, often led to serious dehydration, and was associated with vomiting and fever. 11 cases of E.T.E.C. diarrhea were detected, accounting for 56% of the cases of diarrhea in the 18 patients who were more than 10 years old. Diarrhea caused by E.T.E.C. was sudden in onset, shorter in duration, and caused pronounced dehydration. In a community survey, E.T.E.C. was isolated with equal frequency in the stools of control and case family members. Data suggest that E.T.E.C. is a common cause of adult diarrhea in Bangladesh while R.L.A. is a common cause of diarrhea in children.

Classification of rotavirus VP4 and VP7 serotypes

Rotaviruses, members of the Reoviridae family, are major etiologic agents of acute nonbacterial gastroenteritis of the young in a wide variety of mammalian and avian species, including humans. The need for effective immunoprophylaxis against rotaviral gastroenteritis has stimulated interest in the biochemical, molecular, genetic, and clinical aspects of these agents with the aim of developing safe and effective vaccines. Because neutralizing antibodies appear to play an important role in protection against many viral diseases, rotavirus antigens that induce neutralizing antibodies have played a central role in research and development of a rotavirus vaccine. The VP7 glycoprotein and VP4 spike protein that constitute the outer capsid of a complete rotavirus particle have been shown to be independent neutralization antigens. Since type specificity of the outer capsid proteins of a rotavirus appears to play an important role in protection against disease in experimental animal models, continued efforts have been made for classification and typing of neutralization specificities on the VP7 or VP4 capsid protein. Based on a criterion of > 20-fold differences between the homologous and heterologous reciprocal neutralizing antibody titers, fourteen VP7 (G) serotypes have been established. Studies are underway to characterize and classify the VP4 (P) serotypes among the strains that exhibit the fourteen different G serotypes. Attempts to classify the VP4 serotypes based on the same criterion (i.e., > 20-fold antibody differences) that is applied to classification of VP7 serotypes are in progress. This standard of > 20-fold antibody differences can be applied with hyperimmune serum raised to a reassortant possessing the VP4 encoding gene (and an unrelated VP7 encoding gene). Genotypes can provide leads towards classification but the serotype of a strain should be based on neutralization.

FÆCAL SHEDDING OF HEPATITIS-A ANTIGEN

Serial stool specimens from two individuals with experimental hepatitis-A infection were examined and the shedding pattern of hepatitis-A antigen (HAAg) was determined by immune electron microscopy. HAAg particles were detected at least 5 days before the development of abnormal transaminase levels and jaundice, but not later than the day of peak transaminase levels. The pattern of early faecal shedding of HAAg particles correlated well with the early infectivity of faeces and accorded with the suggestion that HAAg is involved in the aetiology of hepatitis-A infection.

Comparison of reactogenicity and antigenicity of M37 rotavirus vaccine and rhesus-rotavirus-based quadrivalent vaccine

90 Venezuelan infants aged 10-20 weeks were randomly allocated to four groups which received one of the following: the M37 vaccine (1 x 10(4) pfu [plaque-forming units]); quadrivalent rotavirus vaccine (1 x 10(4) pfu each of serotype 3 rhesus rotavirus [RRV] and human rotavirus-RRV reassortants of serotypes 1, 2, and 4); balanced quadrivalent vaccine consisting of 1 x 10(4) pfu of serotype 1 and 3 components but 5 x 10(4) pfu of serotype 2 and 4 components; or placebo. The frequencies of transient febrile responses in these four groups were 20%, 27%, 30%, and 9%. 50% of 22 infants tested who received M37 vaccine showed a serum rotavirus IgA antibody response, compared with 74% of the 23 quadrivalent and 86% of the 22 balanced-quadrivalent recipients. 64% of the M37 recipients showed a neutralising antibody response to M37; 27% showed such responses to human serotype 1 Wa strain and 27% to serotype 4 neonatal strain ST3. 17-39% of the quadrivalent recipients and 27-41% of the balanced-quadrivalent recipients showed neutralising antibody responses to serotypes 1-4. 70-73% of the quadrivalent and balanced quadrivalent groups also showed neutralising antibody responses to RRV.

Safety, infectivity, transmissibility and immunogenicity of rhesus rotavirus vaccine (MMU 18006) in infants

In an attempt to evaluate the immunogenicity, infectivity, transmissibility and safety of rhesus rotavirus vaccine (RRV) MMU 18006, 27 infants ages 5 to 20 months participated in two randomized, double-blind placebo controlled trials, one in a day care setting to allow for child to child contact and close surveillance and the other on an outpatient basis. Fourteen infants (mean age, 8.3 months) received 105 plaqueforming units of RRV and 13 (mean age, 11.1 months) received placebo. In the eight infants who participated in the vaccine trial in the day care setting, there was no evidence of transmissibility of RRV, by either stool excretion or seroconversion. The data from both trials showed RRV to be 100% infective and immunogenic in the vaccinees. There were no gastrointestinal side effects although there was an association between vaccine administration and fever occurring on Days 3 and 4. Based on these encouraging preliminary results, further work is proceeding to evaluate this vaccine at lower doses in this age group of infants.

Acute Viral Enteritis and Exacerbations of Inflammatory Bowel Disease

In order to determine whether or not acute viral gastroenteritis predisposes to exacerbations of inflammatory bowel disease, patients with Crohns disease and ulcerative colitis were observed longitudinally. Assessment of disease activity was correlated with evidence for viral infection by serology and stool antigen testing. Disease exacerbations were rarely associated with rotavirus, Norwalk agent, or adenovirus infection, primarily because these infection rates were very low. However, the few patients having these viral infections often had relapse symptoms.