Production and titration of African swine fever virus in porcine alveolar macrophages.

The broncho-alveolar lavage of a pig (20-40 kg) contains about 1.6 x 10(9) alveolar cells, half of which were macrophages. The number of cells in the lavage of bacille Calmette Guerin (BCG)-treated pigs increased about 4-fold. Both African swine fever virus-infected porcine alveolar macrophages and blood monocytes produced about 1000 hemadsorption units/cell, a value 10-fold larger than that obtained in virus-infected Vero cells. Porcine alveolar cells could be stored frozen and, after thawing, they could be infected with African swine fever virus, producing the same amount of virus as the unfrozen cells. With the number of alveolar macrophages obtained from a single pit it is possible to titer about 3000 virus samples with the same stock of alveolar macrophages.