Final answer:
Antibodies play a significant role in providing immunity to viruses, such as norovirus, by blocking the virus from infecting host cells. A higher number of antibodies typically means increased immunity, as evidenced by fewer plaques in a neutralization assay.
Step-by-step explanation:
Antibodies can provide immunity to viruses, including norovirus, by neutralizing extracellular pathogens. In a neutralization assay, high numbers of antiviral antibodies in a patient's serum will result in fewer plaques. This is because antibodies block key sites on the virus that would normally enhance its infectivity, such as receptors that allow the virus to dock on host cells. Through this blocking, antibodies prevent the virus from entering and infecting host cells. The norovirus, when coated by these neutralizing antibodies, can be filtered out of the body by the spleen and then eliminated in urine or feces.
Therefore, the presence of antibodies against norovirus does suggest a certain degree of immunity. However, as with many infectious diseases, immunity can wane over time or may not be completely protective against all strains of the virus. Good hygiene practices, such as hand washing and careful food preparation, remain essential in reducing the risk of infection.