Development of an Enzyme Immunoassay for Detection of Sapovirus-Specific Antibodies and Its Application in a Study of Seroprevalence in Children

Abstract

Sapoviruses (SVs) are an important cause of acute pediatric gastroenteritis. Due to the lack of appropriate diagnostic methods, the epidemiology of SV-associated illness remains poorly understood. Baculovirus and Escherichia coli expression systems were evaluated for the development of antibody detection enzyme immunoassays (EIA). Age-related antibody prevalence in children was studied using the new EIA. Because of the low yield of the baculovirus system, the E. coli-expressed SV capsid proteins were used to develop the EIA. The antigenic specificities of the E. coli-expressed SV capsid proteins were demonstrated using hyperimmune antisera raised in animals and sera collected from patients. A high prevalence (>90%) of antibodies to both SV (strain Mex340) and norovirus (strain VA387) was observed in children involved in a birth cohort at 20 to 24 months of age; however, at 1 to 3 months of age, <25% of the children possessed anti-SV antibodies versus >90% with anti-NV antibodies. The E. coli-derived SV proteins are an excellent source of antigens for the EIA. SV infection is common in the first 2 years of life. The low prevalence of maternal antibodies detected in Mexican children against SVs in this study is unique and needs to be addressed in future studies.The family Caliciviridae consists of four genera, Norovirus (NV), Sapovirus (SV), Lagovirus, and Vesivirus, from which NV and SV cause disease mainly in humans and therefore are also referred to as human caliciviruses (HuCVs) (9). NVs are the leading cause of epidemic gastroenteritis, often causing large water-or food-borne outbreaks in all ages, while SVs are implicated mainly in pediatric gastroenteritis. In a study among Mexican children, we found that 19% of the sporadic acute gastroenteritis cases were associated with HuCVs and over a third of these were caused by SVs (8). Pang et al. reported 20% and 9% detection rates for NVs and SVs, respectively, in stool specimens of children with acute gastroenteritis in Finland (31,32). It is generally accepted that SV gastroenteritis is less severe than that of rotavirus or NV; however, SVs have been detected in 1 to 3% of stool specimens collected from children hospitalized with gastroenteritis, indicating that SVs can cause severe illness (34,38,47). Also, with the increasing awareness of SV gastroenteritis and improved diagnostic methods, SVs were recently implicated in several gastroenteritis outbreaks in adult populations (22,43).Because of the lack of a suitable animal model and tissue culture system for the propagation of HuCVs (5), the study of these pathogens has advanced slowly since the description of the prototype Norwalk and Sapporo viruses in the 1970s (3, 23). The cloning and genomic characterization of the Norwalk virus (14) and subsequently other HuCVs opened the way for the development of diagnostic techniques, such as reverse transcription-PCR (16) and enzyme immunoassays (EIA) utilizing recombinant virus-like particles (VLPs) (15, 17). These techniques proved to be superior to previously use...

Acute Gastroenteritis Caused by GI/2 Sapovirus, Taiwan, 2007

“…For our patients, the common predisposing factors were poor hygiene and low socioeconomic status, which may expose them to ectoparasites including lice and fl eas. In contrast with previous study fi ndings, B. quintana infectious endocarditis developed on preexisting valvular lesions in all patients (10). This fi nding may refl ect a different clinical evolution than in Europe, where studies have suggested that B. quintana infectious endocarditis followed chronic bacteremia in patients who did not have previous valvular defects (10).…”

“…quintana is mostly associated with human body lice but has also been found in fl eas (9). The predisposing factors for B. quintana endocarditis are homelessness, alcoholism, and exposure to body lice (10). For our patients, the common predisposing factors were poor hygiene and low socioeconomic status, which may expose them to ectoparasites including lice and fl eas.…”

“…However, in a recent molecular epidemiologic study in Japan, a large number of symptomatic and asymptomatic food handlers were found to be infected with noroviruses (9). Several seroprevalence studies also indicated high prevalence rates of antibodies to sapovirus in adults and children (10). All of these fi ndings highlight the need to collect stool specimens from asymptomatic persons and indicate possible "silent" transmission through an asymptomatic route.…”

Etiological Role and Repeated Infections of Sapovirus among Children Aged Less than 2 Years in a Cohort Study in a Peri-urban Community of Peru

“…In contrast, very little information is available about protective immunity against sapovirus infection. Sera collected from naturally infected humans or immunized animals with recombinant VP1 protein of sapovirus were shown to be moderately cross-reactive against the heterologous genotypes and weakly cross-reactive with heterologous genogroups of sapovirus (42)(43)(44). Large-scale studies are needed to investigate whether protective immunity for sapovirus is genotype specific or not, since the number of children with reinfections in this study was small due to a limited sample size.…”

The First Chinese Porcine Sapovirus Strain That Contributed to an Outbreak of Gastroenteritis in Piglets

“…Sapovirus (SaV) belongs to the family Caliciviridae and is a causative agent of gastroenteritis in children and adults (6,2). On the basis of complete capsid gene sequences, SaV can be divided into five genogroups, among which GI, GII, GIV, and GV infect humans, whereas SaV GIII infects porcine species (1).…”