SOS1 and infection: In order to study the intracellular localisation of NS4 within AHSV infected cells, BSR cells were infected with AHSV-3 (representing an NS4 protein from Clade II, or NS4-II) or AHSV-4 (representing NS4-I) and labelled with anti-NS4 for confocal microscopy at 3, 6, 12, 18, 24 and 48 hours post infection (hpi) (Fig 4A).