The present invention provides a recombinant soluble trimeric hemagglutinin(rHA) protein comprising a hemag-glutininectodomain and an oligomerization domain. The rHA is produced as a solublehomotrimer, and may further comprises asignal peptide and/or an endoplasmic reticulum (ER) retention signal. Theinvention is also directed to nucleic acids encoding therHA of the invention, as well as vectors and chimeric constructs comprisingthe nucleic acid. Methods of producing the rHA arealso provided. The rHA described herein may be used to formulate influenzavaccines, or may be used to enrich existing vaccines.
