Quantitative and rapid interference of bovine viral diarrhea virus BVDV/END - and BVDV/END + strains

Abstract

Homologous interference in vitro is defined as the ability of primary viral infection to prevent secondary homologous superinfection. Non-cytopathic bovine viral diarrhea virus (ncp BVDV) has been classified according to the exaltation of Newcastle disease phenomenon (END) as END positive (E + ) and END negative (E - ) strains. Simultaneous inoculation of MDBK-SY cell monolayers with BVDV/E - virus and a three log higher amount of BVDV RK13/E + virus, leads to acquisition of the BVDV/E - feature of blocking Newcastle disease virus (NDV) infection in cells. BVDV/E - strains, particularly at a high titre and MOI ≥ 1.25, can exert and impose their effects in BVDV/E + infected cells; however, if BVDV/E - MOI is reduced to MOI below 0.625, the BVDV/E + effect can be restored leading to cytopathic effects (CPE) induction by NDV reciprocal to the titre of the BVDV RK13/E + strain. Moreover, blocking and prevention of induced CPE by NDV or vesicular stomatitis virus (VSV) occurs even when BVDV/E - superinfects primary BVDV/E + infected cells, indicating a defective homologous interference between BVDV/E + and BVDV/E - strains. Taken together, BVDV/E - E - strains have a strong competitive potency and mediate a fast acting (i.e. within 60 min) influence against BVDV/E + activity. This may be relevant in vivo where BVDV/E - and BVDV/E + combinations are frequently isolated from infected individuals.