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Chapter 84 : Rotaviruses and Noroviruses
Enzyme immunoassay (EIA), in particular, has been used extensively to establish the incidence and prevalence of rotavirus infection and to define antigenic characteristics of the virus. Antiserum prepared against virus of one serotype tends to neutralize homotypic rotaviruses more efficiently than it neutralizes heterotypic viruses. P1A and P1B are associated with the most virulent human rotaviruses that cause diarrhea. The protocol for the EIA to determine the VP4 serotype is similar to that for the VP7 serotyping EIA described, except that VP4 serotyping antibodies are used. Human infections are most commonly caused by GI and GII noroviruses, representing 15 or more genotypes. By nature of the infection, detection of norovirus nucleic acid is performed with stool samples which may contain inhibitors to RT-PCR. Significant sequence diversity among the multitude of norovirus strains has made it difficult to design primers that detect all strains of norovirus. The RT-PCR methods used most extensively to date are neither the simplest nor the fastest. In addition, verifying the specificity of the amplicon necessitates additional analysis, including probe hybridization and variations of this technique, as well as sequencing the product. Two fluorescence techniques, in single-tube formats, are increasingly studied to detect noroviruses in clinical samples, water, and shellfish: SYBR green dye incorporation into amplicons and the TaqMan fluorogenic detection system. Developing the optimal molecular detection assay for the highly diverse noroviruses continues to be a challenge that is being pursued by scientists throughout the world.
Direct EIA for antigen measurement. Reproduced from reference 24 with permission.
Indirect EIA for rotavirus antigen measurement. Reproduced from reference 24 with permission.
Cross-reactivity due to anti-immunoglobulin.
Reference viruses and a partial list of VP7 monoclonal antibodies for G serotyping
Reference viruses and a partial list of VP4 monoclonal antibodies for P serotyping