Date Published: April 17, 2007
Publisher: Public Library of Science
Author(s): Sarah E Blutt, David O Matson, Sue E Crawford, Mary Allen Staat, Parvin Azimi, Berkeley L Bennett, Pedro A Piedra, Margaret E Conner, David Candy
Abstract: BackgroundAntigenemia is commonly detected in rotavirus-infected children. Although rotavirus RNA has been detected in serum, definitive proof of rotavirus viremia has not been shown. We aimed to analyze a defined patient population to determine if infectious virus could be detected in sera from children with rotavirus antigenemia.Methods and FindingsSerum samples obtained upon hospitalization from children with gastroenteritis (57 stool rotavirus-positive and 41 rotavirus-negative), children with diagnosed bronchiolitis of known (n = 58) or unknown (n = 17) viral etiology, children with noninfectious, nonchronic conditions (n = 17), and healthy adults (n = 28) were tested for rotavirus antigen by enzyme immunoassay (EIA). Results of serum antigen testing were assessed for association with clinical and immunological attributes of the children. Rotavirus antigenemia was detected in 90% (51/57) of children with rotavirus-positive stools, in 89% (8/9) of children without diarrhea but with rotavirus-positive stools, in 12% (2/17) of children with bronchiolitis of unknown etiology without gastroenteritis, and in 12% (5/41) of children with gastroenteritis but with rotavirus-negative stools. Antigenemia was not detected in sera from children with noninfectious nonchronic conditions, children with bronchiolitis of known etiology and no gastroenteritis, or healthy adults. Neither age nor timing of serum collection within eight days after onset of gastroenteritis significantly affected levels of antigenemia, and there was no correlation between antigenemia and viral genotype. However, there was a negative correlation between serum rotavirus antigen and acute rotavirus-specific serum IgA (r = −0.44, p = 0.025) and IgG (r = −0.40, p = 0.01) titers. We examined 11 antigen-positive and nine antigen-negative sera for infectious virus after three blind serial passages in HT-29 cells using immunofluorescence staining for rotavirus structural and nonstructural proteins. Infectious virus was detected in 11/11 (100%) sera from serum antigen-positive children and in two out of nine (22%) sera samples from antigen-negative children (p = 0.002).ConclusionsMost children infected with rotavirus are viremic. The presence of viremia is directly related to the detection of antigenemia and is independent of the presence of diarrhea. Antigenemia load is inversely related to the titer of antirotavirus antibody in the serum. The finding of infectious rotavirus in the blood suggests extraintestinal involvement in rotavirus pathogenesis; however, the impact of rotavirus viremia on clinical manifestations of infection is unknown.
Partial Text: Rotavirus is a major cause of gastroenteritis in pediatric populations, resulting in 114 million episodes of gastroenteritis per year worldwide  and an annual economic burden in the United States estimated in 1998 at over one billion dollars . Rotaviral infection is generally thought to be localized to the epithelial cells lining the small intestine. However, case reports suggest that rotavirus may cause infection and illness outside the intestine, including hepatitis and nephritis , pneumonia , exanthema , disseminated intravascular coagulation , haemophagocytic lymphohistiocytosis , and neurological complications such as encephalitis , encephalopathy , cerebellitis , or convulsions or seizures [10,11]. Reports of attempts to find rotavirus RNA or proteins at extraintestinal sites include detection of RNA in cerebral spinal fluid [12,13], central nervous system , heart [14,15], blood , and endothelial cells [14,17], while rotavirus nonstructural proteins were detected in liver and kidney sections . These findings support the possibility of uncommon extraintestinal infections that were thought to be either infections with unusual rotavirus strains or rare host genetic or immunologic defects in the infected child. Early work supporting this idea described rotavirus antigenemia in immunodeficient but not immune-competent children .
Rotavirus infection in children results in antigenemia [19,20]. Although RNA has been associated with antigenemia , proof of viremia in children has not been previously demonstrated. Here, we present proof that antigenemia is associated with infectious virus in rotavirus-infected children. Major technical barriers to the isolation of infectious wild-type human rotavirus from serum are that human primary isolates require adaptation to grow in vitro  and that serum factors can inhibit viral replication [42,43]. Attempts to isolate human rotavirus from serum were unsuccessful using MA104 cells . Our detection of infectious virus in serum may have been greatly enhanced by the use of HT-29 cells , serial blind passage, and testing multiple dilutions of sera. The detection of infectious virus in the serum from rotavirus-infected children indicates that rotavirus is present systemically, in addition to its well-documented mucosal infection. In addition, antigenemia is predictive of viremia and can be used as a marker for the presence of extraintestinal rotavirus.