Infectivity Titration of Guinea-pig Inclusion Conjunctivitis Agent in Irradiated McCoy Cells

Abstract

Estimation of the infectivity of the agent of guinea-pig inclusion conjunctivitis for irradiated McCoy cells, assayed as inclusion-forming units, was influenced by the age of cells after irradiation, the maturation time of the inclusions, the centrifugal force and the centrifugation temperature. Agent passaged through irradiated McCoy cells or guinea-pig conjunctivae showed a greater capacity to infect irradiated McCoy cells without centrifuging than agent grown in a chick embryo. The nature of the change and the mechanism of infectivity enhancement by centrifuging are discussed.

Host Modification of the Adherence Properties of Chlamydia trachomatis

“…Furthermore, it has been noted that successive passage in cell cultures resulted in an 'adaptation', i.e. rapid development of the intracellular bacterium, and also acquisition of greater infectivity to the cell cultures than when grown in chick yolk sac (Griffiths et al, 1976). However, during passage of the trachomaderived C. trachomatis strains in McCoy cell cultures, there was no detectable alteration in the major antigens (Gordon et al, 1971).…”

Differential Neutralization of Spontaneous and Centrifuge-assisted Chlamydial Infectivity

“…Centrifugation facilitates chlamydia1 infection, at least in part, by greatly increasing attachment; this may range from 5-to 7-fold, as with MRC4f, to more than 100-fold with other chlamydiae (Stirling & Richmond, 1977;Griffiths et al, 1976). The facilitation occurs, not through sedimentation of organisms, but from induced cell surface changes (Allan & Pearce, 1979), which may explain the failure of antibody to inhibit attachment in centrifugeassisted infection.…”

“…bovine serum (growth medium), harvested, irradiated and monolayers were prepared as previously described (Griffiths et al, 1976); monolayers were used 24 to 96 h after irradiation of cells.…”

“…To measure spontaneous infection, replicate cell monolayers, from which growth medium had been removed, were inoculated with 0.2 ml of diluted chlamydial suspensions and incubated for 90 min at 35 "C. For centrifuge-assisted infection, inoculated monolayers were centrifuged at 1580 g for 90 min at 35 "C (Griffiths et al, 1976). Inoculum supernatants were then removed and replaced by fresh growth medium (1 ml).…”

Host Modification of Chlamydiae: Differential Infectivity for Cell Monolayers of Chlamydiae Grown in Eggs and Monolayers

“…We have previously developed a quantitative assay for infectivity of the guinea-pig inclusion conjunctivitis strain (GP-IC) of C. psittaci using centrifugation to enhance infection of irradiated McCoy cell monolayers (Griffiths et al, 1976). We found that organisms passaged through monolayers or the guinea-pig conjunctiva showed a greater capacity to infect static monolayers (spontaneous infection) than organisms grown in the chick embryo.…”