Infectious entry pathway of influenza virus in a canine kidney cell line.

Abstract

The entry of fowl plague virus, an avian influenza A virus, into Madin-Darby canine kidney (MDCK) cells was examined both biochemically and morphologically . At low multiplicity and 0°C, viruses bound to the cell surface but were not internalized . Binding was not greatly dependent on the pH of the medium and reached an equilibrium level in 60-90 min. Over 90% of the bound viruses were removed by neuraminidase but not by proteases. When cells with prebound virus were warmed to 37°C, part of the virus became resistant to removal by neuraminidase, with a half-time of 10-15 min. After a brief lag period, degraded viral material was released into the medium . The neuraminidase-resistant virus was capable of infecting the cells and probably did so by an intracellular route, since ammonium chloride, a lysosomotropic agent, blocked both the infection and the degradation of viral protein.When the entry process was observed by electron microscopy, viruses were seen bound primarily to microvilli on the cell surface at 0°C and, after warming at 37°C, were endocytosed in coated pits, coated vesicles, and large smooth-surfaced vacuoles . Viruses were also present in smooth-surfaced invaginations and small smooth-surfaced vesicles at both temperatures .

Susceptibility of bone marrow-derived macrophages to influenza virus infection is dependent on macrophage phenotype

“…The higher levels of M1 mRNA in IL-4-treated cells argue that the presence of virus antigen in cells is not simply due to increased phagocytosis of viral antigens, but rather is due to increased infection of these macrophages. Influenza viruses usually enter cells by endocytosis following initial binding of the haemagglutinin to sialic acids on the cell surface (Matlin et al, 1981;Skehel & Wiley, 2000). However, there is evidence that influenza A virus …”

Virus trafficking – learning from single-virus tracking

“…Influenza virus uses a distinct entry mechanism 13,25,26 . As directly visualized in a virus tracking experiment, Influenza viruses can simultaneously use two pathways to enter cells 13 (FIG.…”

Insights into neutralization of animal viruses gained from study of influenza virus

“…A multi-stage process of 'uncoating' follows whereby the viral genome becomes functional and able to direct virus multiplication. This commences when a proton pump in the membrane acidifies the internal environment of the vesicle, causing the HA to undergo a conformational change which leads to primary uncoatingfusion of the viral and vesicle membranes and entry into the cytoplasm proper of the nucleocapsid [10][11][12]. Details of secondary uncoating can only be surmised but there have to be changes in nucleocapsid such as loss of proteins and/or relaxation of structure so that the viral genome can be exposed sufficiently to be expressed.…”