Abstract: Highly purified antihemophilic factor is produced by a process comprising a PEG precipitation step, a gel filtration step and a virus inactivation step. Al(OH).sub.3 adsorption and PEG precipitation carried out at room temperature allow processing to proceed directly to a gel filtration step.

Abstract: Highly purified antihemophilic factor can be produced from a cryoprecipitate by a process comprising a PEG precipitation step, a viral inactivation step and a gel filtration step, all steps being carried out at room temperature.

Abstract: Lipid-enveloped viruses present in purified biologically active protein products obtained from blood or cell culture systems can be inactivated by contacting the products with caprylic acid at a non-ionized concentration, pH, temperature and ionic environment sufficient to inactivate the viruses without adversely precipitating or affecting the biological activity of the protein products.

Abstract: There is disclosed an immunizing composition comprising a non-toxic polysaccharide isolated from gram-negative bacteria, especially from Pseudomonas aeruginosa, covalently coupled to a non-toxic protein from the gram-positive bacterium Micrococcus luteus by means of a 4-12 carbon moiety. To prepare the above immunizing agent, the lipid A portion of lipopolysaccharide from a gram-negative bacterium is separated to give a non-toxic polysaccharide. Reactive aldehyde groups are generated on the non-toxic polysaccharide by selective oxidation. The non-toxic polysaccharide is then covalently coupled to a non-toxic protein isolated from said gram-positive bacterium, Micrococcus luteus, by means of a polyfunctional compound having 4-12 carbon atoms and having at least two functional groups which are reactive to the aldehyde groups on the non-toxic polysaccharide and to the carboxylic groups on the non-toxic protein.