Final answer:
Adaptive immunity to orthomyxoviruses like the influenza virus is predominantly conferred by the hemaglutinin protein, which is critical for inducing a protective immune response. Neuraminidase also plays a role, but mainly in virus release from host cells, and is targeted by antiviral drugs.
Step-by-step explanation:
The molecules that predominantly confer adaptive immunity to orthomyxoviruses, such as the influenza virus, are the hemagglutinin (H) and neuraminidase (N) proteins. However, it is the hemagglutinin protein that is most critical for inducing a protective immune response. Hemagglutinin allows the virus to attach and enter host cells and is the primary target for neutralizing antibodies. A strong immune response is elicited, especially when haemagglutinin is recognized by the immune system from a previous infection or vaccination, offering protection against that specific strain of the virus.
Despite this, the influenza virus is notorious for its rapid antigenic changes, which can result in the emergence of new strains through mutations in hemagglutinin or neuraminidase. This antigenic drift can lead to the evasion of the host's immune response, enabling the virus to spread and potentially cause epidemics. The neuraminidase protein, while also a target for the immune response, is more involved in the release of progeny viruses from the host cell surface, as it cleaves the links between the virus and the host cell. Antiviral drugs known as neuraminidase inhibitors can block this action, aiding in the treatment of influenza infections.