Human viral gastroenteritis

Infection immunity of piglets to either VP3 or VP7 outer capsid protein confers resistance to challenge with a virulent rotavirus bearing the corresponding antigen

A single-gene substitution reassortant 11-1 was generated from two porcine rotaviruses, OSU (serotype 5) and Gottfried (serotype 4). This reassortant derived 10 genes, including gene 4 encoding VP3, from the OSU strain and only gene 9, encoding a major neutralization glycoprotein (VP7), from the Gottfried strain and was thus designated VP3:5; VP7:4. Oral administration of this reassortant to colostrum-deprived gnotobiotic newborn pigs induced a high level of neutralizing antibodies not only to Gottfried VP7 but also to OSU VP3, thus demonstrating that VP3 is as potent an immunogen as VP7 in inducing neutralizing antibodies during experimental oral infection. Gnotobiotic piglets infected previously with the reassortant were completely resistant to oral challenge with the virulent Gottfried strain (VP3:4; VP7:4), as indicated by failure of symptoms to develop and lack of virus shedding. Similarly, prior infection with the reassortant induced almost complete protection against diarrhea and significant restriction of virus replication after oral challenge with the virulent OSU strain (VP3:5; VP7:5). Thus, it appears that (i) the immune system of the piglet responds equally well to two rotavirus outer capsid proteins, VP3 and VP7, during primary enteric rotavirus infection; (ii) antibody to VP3 and antibody to VP7 are each associated with resistance to diarrhea; and (iii) infection with a reassortant rotavirus bearing VP3 and VP7 neutralization antigens derived from two viruses of different serotype induces immunity to both parental viruses. The relevance of these findings to the development of effective reassortant rotavirus vaccines is discussed.

Polyacrylamide gel electrophoresis of RNA compared with polyclonal- and monoclonal-antibody-based enzyme immunoassays for rotavirus

Polyacrylamide gel electrophoresis (PAGE) of rotaviral RNA, a sensitive and highly specific test for detecting rotavirus in stool, was compared with two commercially available enzyme immunoassays (EIAs), monoclonal (Pathfinder) and polyclonal (Rotazyme II). Stool samples from 204 children with nosocomial diarrhea were tested for rotavirus by both EIAs and by PAGE of RNA extracted from raw stools or 10% stool suspensions. Samples which tested positive by either EIA but were negative by PAGE were subjected to blocking EIA with rabbit or goat anti-SA11. Rotavirus was detected by PAGE and Pathfinder in 62 stools, but only 47 of these were positive by Rotazyme II. Blocking assays of EIA-positive, PAGE-negative samples suggested the presence of rotavirus in four additional stools. Sensitivity and specificity measured against PAGE and blocking assays were: Pathfinder, 0.985 and 0.934; and Rotazyme II, 0.731 and 0.927, respectively. False-positive rates were 0.134 for Pathfinder and 0.149 for Rotazyme II. The specificity and rate of false-positive results of Pathfinder were improved by using an adjusted optical density cutoff 4.36 times greater than that recommended by the manufacturer (specificity, 0.993; sensitivity, 0.985; false-positive rate, 0.015).

Acute diarrhoea in adults: aetiology, clinical appearance and therapeutic aspects

A prospective study of acute diarrhoea was performed during 15 months 1981/1982 and included 731 patients and 240 controls. 43% had been infected abroad. A cluster of travellers with bacterial pathogens was diagnosed in July-August. The following pathogens were found: Campylobacter (18%), enterotoxigenic E. coli (6%), Salmonella spp. (5%), rotavirus (4%), Yersinia enterocolitica (3%), Giardia lamblia (3%), Shigella spp. (2%), Clostridium difficile (2%), enteroviruses (2%) and Entamoeba histolytica (less than 1%). More than 90% of the bacterial or parasitic enteropathogens were detected in the first stool sample. Only 10% of the patients needed hospital treatment and for 97% oral fluids were sufficient. The median duration of diarrhoea was 9 days. No fatal cases occurred and only 2 cases of chronic bowel disease were detected.

Bovine milk immunoglobulins for passive immunity to infantile rotavirus gastroenteritis

Pregnant cows were successfully hyperimmunized with all four human rotavirus serotypes, resulting in a 100-fold increase in neutralizing milk antibody titers over those of controls. Milk antibodies were isolated batchwise from 1,000 kg of pooled milk for the first 10 lactation days, yielding 10 kg of freeze-dried milk immunoglobulin concentrate consisting of 50% bovine milk immunoglobulins. Milk immunoglobulin concentrate showed neutralizing activities against all four human rotavirus serotypes that were 100 times higher than those in pooled human milk samples and 10 times higher than those in a commercial pooled immunoglobulin preparation from pooled human blood serum. In vitro neutralization tests showed that milk immunoglobulin concentrate had powerful antiviral activity, even against very high doses of infectious rotaviruses. Because the technology of the milk immunoglobulin concentrate ensures that it is innocuous and can be used for oral application, it is proposed that milk immunoglobulin concentrate be used to induce passive immunity to infantile rotavirus gastroenteritis.

Perinatal viral infections

In comparison to older children and adults, neonates are immunologically incompetent. They are susceptible to infections caused by a variety of microorganisms, including bacteria, fungi and viruses. These infectious agents may be acquired by neonates either prenatally, during the intrapartum period or postnatally. The purpose of this review is to emphasize the potential impact of viral infections contracted by neonates at the time of delivery or within the neonatal period. The viruses reviewed include the herpes group of viruses (cytomegalovirus, herpes simplex viruses and varicella-zoster virus), type B hepatitis virus, human immunodeficiency virus, respiratory viruses, enteroviruses, rotavirus and human papilloma virus. For each virus the potential sources and incidence of the infection, the common manifestations of the illness, and possible means of prevention and therapy are discussed. Although infections caused by bacteria tend to be more clinically dramatic and more immediately life-threatening, it is emphasized that infections caused by viruses are common and associated with substantial long-term morbidity. Perinatal viral infections need to be recognized as early in life as possible so that their natural history can be more completely defined and any possible intervention made.

Comparison of methods for rotavirus detection in water and results of a survey of Jerusalem wastewater

Methods for the detection of viable rotaviruses and rotavirus antigen in water were developed and compared. The methods included laboratory-developed enzyme-linked immunosorbent assays (ELISAs) with chromogenic and luminescent substrates, commercial Rotazyme and Enzygnost ELISAs, and an indirect immunofluorescent assay. Of the methods tested, the immunofluorescent assay and the Enzygnost ELISA were the most sensitive for the simian rotavirus SA-11. All of the methods were positive for human rotavirus from clinical specimens. Seeded SA-11 rotavirus was concentrated from water by absorption to and elution from Zeta Plus filters followed by organic flocculation. Interference with the assays by components of the wastewater concentrates was minimal for the ELISAs, although the undiluted organic flocs were cytotoxic for the immunofluorescent assay. A survey of Jerusalem wastewater was carried out over the course of 1 year, and samples were assayed for rotaviruses and enteroviruses. Although enteroviruses were found in almost all of the samples, all samples were negative for rotaviruses. The concentration of rotaviruses in the wastewater was thus below the detection limit of the method used.

Sialic acid glycoproteins inhibit in vitro and in vivo replication of rotaviruses

We investigated the interactions of rotaviruses with glycoproteins and cells that support rotaviral replication. We found that a wide range of naturally occurring glycoproteins, including ovalbumins and ovomucoids from chicken and turkey eggs, and mucin derived from bovine submaxillary glands, inhibit the replication of rotaviruses in MA-104 cells. Our studies further indicated that the glycoproteins bind directly to rotaviruses and that virus-glycoprotein binding is dependent largely upon interactions with sialic acid oligosaccharides. We found that accessible sialic acid oligosaccharides are required for efficient rotavirus infection of MA-104 cells, thus demonstrating that sialic acid oligosaccharides play an important role in the interactions of rotaviruses with both glycoproteins and cells that support rotaviral replication. Bovine submaxillary mucin and chicken ovoinhibitor can also prevent the shedding of rotavirus antigen and the development of rotavirus gastroenteritis in a mouse model of rotavirus infection. Our findings document that a range of glycoproteins inhibit the in vivo and in vitro replication of rotaviruses and suggest that the alteration in the quantity or chemical composition of intestinal glycoproteins is a potential means for the modulation of enteric infections.

Enzyme-linked immunosorbent assays for Snow Mountain and Norwalk agents of viral gastroenteritis

Enzyme-linked immunosorbent assays (ELISAs) for antigen detection and blocking ELISAs for serum antibody rises were developed for the Snow Mountain and Norwalk agents of viral gastroenteritis. The ELISAs were as sensitive as the existing radioimmunoassays and were specific for the Snow Mountain or Norwalk agent. The blocking ELISAs detected the same number of significant rises in antibodies to these agents as did the existing blocking radioimmunoassays.

Electropherotyping of human rotaviruses: an epidemiological survey of rotavirus infections in Sicily

An electrophoretic analysis of rotavirus RNA segments was carried out on 522 faecal specimens, obtained from children hospitalized in Sicily in the period 1981/85. One hundred and one viral isolates could be characterized with respect to the electrophoretic pattern of their genomic RNAs. This analysis revealed that in 1981/82 different electropherotypes cocirculated in the infant population. In 1983 one of the patterns became prevalent; in 1984/85 only one electropherotype was detected, both in Palermo and Catania specimens. The serotyping showed that all viral strains with the prevalent electropherotype were subgroup II and serotype 1. These results contrast with the extensive genome variability of rotavirus strains observed in urban areas.

An eight-year study of the viral agents of acute gastroenteritis in humans: ultrastructural observations and seasonal distribution with a major emphasis on coronavirus-like particles

During an 8-yr period, 862 stool specimens from patients with gastroenteritis were examined by electron microscopy after negative staining with 2% phosphotungstic acid (pH 6.5). Forty-one percent of the specimens submitted over an 8-yr period were determined to be positive for virus or viruslike particles belonging to one or more of seven morphologically distinct viral groups. Coronavirus-like particles (CVLPs) were present in 69.8% of the positive stool specimens. Membranous profiles containing "complement-type" holes (10 nm in diameter) were identified in some preparations containing CVLPs. The second most prevalent viral agent found in stool specimens was the rotavirus (17% of all positive stools). The incidence of other viruses identified in the survey were as follows: adenovirus 4.5%, picorna/parvovirus agents 2.9%, Norwalk-like agent 2.9%, astrovirus 1.9%, and calicivirus 0.5%. Unclassified small round viruses (approximately 25-30 nm in diameter) represented 0.5%. It was also determined that there was a seasonal distribution in excretion of all viruses except for CVLPs. A greater number of viruses were identified in the cooler, drier months of the year.

Detection of rotavirus in stool specimens with monoclonal and polyclonal antibody-based assay systems

Accurate diagnosis of rotavirus is important in both clinical and research situations. A total of 100 stool specimens from children with diarrhea were tested for rotavirus by electron microscopy. These specimens were then coded and tested for rotavirus by four procedures: a monoclonal antibody-based enzyme immunoassay (EIA) (Pathfinder; Kallestad Laboratories, Inc., Austin, Tex.), two polyclonal antibody-based EIAs (Rotazyme II; Abbott Laboratories, North Chicago, Ill.; and an EIA performed with reagents from the National Institutes of Health, Bethesda, Md. [NIH reagent EIA]), and a latex agglutination (LA) assay (Rotalex; Medical Technology Corp., Somerset, N.J.). The sensitivity of the monoclonal antibody EIA (95%) was superior to those of the polyclonal antibody EIAs (73% for Rotazyme II and 57% for the NIH reagent EIA) and the LA assay (61%). The specificity of the LA assay (98%) was slightly better than those of the other systems (88 to 96%). The positive and negative predictive values of the monoclonal antibody EIA (93 and 96%, respectively) were better than those of Rotazyme II (82 and 80%, respectively), the LA assay (96 and 76%, respectively), and the NIH reagent EIA (93 and 74%, respectively). The visual readings of the monoclonal antibody EIA correlated better with the spectrophotometric optical density readings than did the visual readings of the polyclonal antibody EIAs; however, the agreement of both with electron microscopy results was poor when 1+ or plus-minus readings were observed. The monoclonal antibody EIA is more sensitive and predictive than other rotavirus detection systems and second only to the LA assay in specificity in detecting rotavirus in stool specimens.

Norwalk like viruses: study of an outbreak

An outbreak of acute non-bacterial gastroenteritis is reported, during which a ward had to be closed, and stool samples from 15 patients showed a virus structurally similar to the Norwalk agent.

A new screening test for rotavirus infection

A simple and rapid staphylococcal coagglutination test, using rabbit antisera prepared against Nebraska calf diarrhea virus (NCDV), is described for the detection of rotavirus in neonatal fecal specimens. When the samples were examined directly using the coagglutination test, more than 60% of the specimens agglutinated the control reagent. These non-specific reactions were markedly reduced by preincubation of the specimens with non-immune rabbit serum and further heating at 80 degrees C for 45 min. Such treatment did not reduce the specific activity in the coagglutination test when rotavirus-containing stools were tested. The coagglutination test was compared with ELISA in 290 stools positive or negative for rotavirus. The sensitivity of the coagglutination test was 92%, the specificity 91% and the predictive value 31%. These results indicate that coagglutination is a suitable test for rapid screening of rotavirus infection in clinical practice.

Rotavirus neutralizing protein VP7: antigenic determinants investigated by sequence analysis and peptide synthesis

The rotavirus neutralizing antigen, VP7, is a 37,000-molecular-weight glycoprotein which is a major component of the outer shell of the virion. The amino acid sequence of VP7 for strain S2 (human serotype 2) and Nebraska calf diarrhea virus (bovine serotype) has been inferred from the nucleic acid sequence of cloned copies of genomic segment nine. Comparison of the amino acid sequences of these two VP7 proteins with those already determined for other rotavirus strains reveals extensive sequence conservation between serotypes with clusters of amino acid differences sited predominantly in hydrophilic domains of the protein. Six peptides have been synthesized that span the hydrophilic regions of the molecule. Antisera to these peptides both recognize the respective homologous peptides in a solid-phase radioimmunoassay and bind to denatured VP7 in a Western blot. However, none of the antisera either recognize virus or exhibit significant neutralizing activity, indicating that these peptide sequences are not available on the surface of the virus.

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.

Epidemiological survey on bacterial, viral and parasitic agents in patients affected by acute enteritis

During the period June 1983-May 1984, faecal specimens from 797 patients with acute enteritis were examined for the presence of bacterial, viral and parasitic agents; 209 (26.2%) enteritic pathogens were identified, of whom 118 (35.4%) in 333 samples from the pediatrics wards. Bacterial agents were detected in 122 (15.3%), viruses in 63 (7.9%) and parasites in 25 (3.1%) of the 797 specimens. LT-producing E. coli, Salmonella and Rotavirus were the most frequent pathogens. Bacterial agents occurred most frequently in the summer and autumnal months, whereas viruses showed two peaks, the first one in summer due to cultivable agents, the second in winter to Rotavirus mainly.

Immunological aspects of virology. WHO Working Group

This article summarizes the conclusions of a WHO Working Group concerning progress towards an improved understanding of the mechanisms of natural and vaccine-induced immunity to viral infection in man. Particular attention is given to the role of humoral immunity, non-specific cellular and virus-specific T-cell responses, interferons and lymphokines in the immune response to virus infection. Detailed knowledge of the immune responses relevant to protection by vaccines is important for a rational approach to vaccine design. Recommendations are made for future collaborative research in immunovirology with due consideration given to the needs of the recently established WHO Vaccine Development Programme.