The Human Enteric Caliciviruses: an Expanded Role for Old Viruses

Abstract

The human enteric previously known as the Norwalk family of viruses, the classic human caliciviruses, or the small round-structured viruses, are a group of enteric pathogens that are a common cause of gastroenteritis in children and adults alike. When the gene encoding the capsid was expressed in baculovirus, the resulting protein self-assembled into virus-like particles that looked like natural virus by electron microscopy (EM) and provided replenishable reagents for serologic testing, structural studies, and antigen to develop immunoassays for antigen detection. These molecular discoveries and diagnostic advances have permitted researchers to reassess the clinical and epidemiologic features of illness caused by the caliciviruses and to reconsider public health approaches to their prevention and control. This chapter provides a review to highlight some of the advances in our understanding of calicivirus-associated gastroenteritis following the introduction of new molecular diagnostics, with illustrations drawn from several recent epidemic investigations. Tracing some epidemics back to their source has extended the use of diagnostics to the detection of viruses in contaminated food and water. Despite the major advances in the knowledge of the caliciviruses based upon the understanding of their sequence and molecular organization, the search for simple diagnostic assays has been difficult. Nonetheless, in the process of sequencing many strains, the human enteric caliciviruses fell into two distinct genera. The ability to sequence polymerase chain reaction (PCR) products made it possible to trace the molecular epidemiology of caliciviruses in outbreaks of disease.