| 摘要 |
Cultures of S. pneumoniae can be caused to express substantially cell-free surface proteins, in particular PspA, into a medium from intact cells by exposing the culture to a medium comprising from about 0.5 % to not more than about 3 % choline either during growth of a culture or thereafter, or by growing a culture containing about 0.005 to about 0.1 % ethanolamine in the absence of choline. The supernatant medium may be used directly for preparation of immunogens, undesired materials may be removed before use, or the protein in the supernatant may be separated and purified as needed. |
