Showing papers by "Karin Müller published in 1988"

Multiplication of influenza A viruses with cleavable and non-cleavable haemagglutinin in chicken embryo membranes or organs, and cell cultures derived therefrom.

Abstract: Summary Pathogenic properties of influenza A viruses introduced into embryonated chicken eggs via the allantoic cavity, the amniotic cavity or the yolk sac were studied using viruses with cleavable or non-cleavable haemagglutinin (HA), or reassortants derived from the highly pathogenic fowl plague virus (FPV) which has a cleavable HA. The various organs, membranes and fluids were analysed for virus yields, and by immunohistochemistry for production of viral nucleoprotein. Virus replication in primary tissue cultures derived from various embryonic organs was also studied. Some of the reassortants, which were previously found to be non-pathogenic for chickens and were temperature-sensitive (ts) at 40 °C, multiplied at 37 °C to the same extent as the highly pathogenic FPV. The spread of other non-pathogenic reassortants in the embryo was restricted. For example, 81/Ho was able to multiply to a reasonable extent only in the chorioallantoic and the allantoamniotic membranes. After inoculation of the A/PR/8/34 strain containing a non-cleavable HA into the amniotic cavity, virus multipled only in the inner epithelial layer of the amnion, in superficial epidermal cells and in superficial epithelia of the oropharyngeal cavities, the nasal and paranasal sinuses and the oesophagus. Kidneys were free of virus antigen, although the virus multiplied to high titres in primary tissue cultures derived from embryonic kidneys. Thus influenza A viruses can be non-pathogenic for chickens because they are ts and unable to multiply at the body temperature of chickens (41 °C), or because their spread in the animal is impaired per se.

Effect of dimethylsulfoxide (DMSO) on virus replication and maturation.

Abstract: At intermediate concentrations of DMSO the yields of infectious virus and biologically active hemagglutinin and neuraminidase of an influenza A virus (fowl plague virus) and of reassortants therefrom are enhanced severalfold, even though viral protein synthesis is not significantly affected. A corresponding enhancing effect was also found with New castle disease and Semliki Forest viruses. At elevated concentrations of DMSO virus yield decreases, and under these conditions the synthesis of the late influenza virus proteins is specifically inhibited. The results indicate that DMSO can facilitate the assembly of virus particles, and viral components, which are normally produced in surplus amounts, now contribute to the maturation of infectious particles.

Interference between influenza A viruses with a cleavable and a noncleavable hemagglutinin; pH-stability after mixed infection

Abstract: The infectivity of influenza A viruses like fowl plague virus (FPV) with a cleaved hemagglutinin (HA) is highly sensitive to treatment at pH 5, while strains like PR 8 or virus N with a noncleaved HA survive under this condition. After double infection of chick embryo cells with FPV and PR 8 or virus N, the yield of virus with the HA gene of FPV is greatly reduced. However, it can now survive treatment at pH 5, and the surviving FPV particles form plaques only in the presence of trypsin, indicating that they were coated by the HA of PR 8 or virus N, depending on the coinfecting virus. The results are discussed with respect to the build-up and maintenance of a large reservoir of nonpathogenic influenza A viruses with noncleavable HA in water fowl.