Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Suspension cultures of L-cells were infected with strains representing different biotypes of Chlamydia (C.) psittaci of bovine, ovine, caprine, equine, feline, porcine and guinea pig origin. Biotype-1 chlamydiae multiplied to high titers, and high yields of infectivity were obtained in subsequent passages. Chlamydial strains representative of other biotypes did not infect suspension cultures efficiently. Low rates of infection were obtained on the first passage, and the infectivity was lost while attempting subpassages. L-cells inoculated in suspension with more than one inclusion forming unit/L-cell of the chlamydial strain B577 and allowed to form monolayers, were destroyed within 15 days. However, upon continued incubation, a few surviving cells repopulated the flasks and remained persistently infected. The persistent state was characterized by cycles of repopulation with a low ratio of infected cells, and cycles of extensive cytopathology where >90% of the cells had inclusions and which could be terminated with penicillin. Immunofluorescence and superinfection during repopulation revealed that the presistently infected cells adsorb chlamydiae, but their multiplication is arrested. This non-permissive state was terminated by cycloheximide treatment. The different chlamydial biotypes were immunotyped by an indirect microimmunofluorescence (IMIF) test. Groups of chlamydia-free BALB/c mice received two weekly intravenous inoculations with chicken embryo-propagated, partially purified elementary bodies of each strain. Antisera were collected 4 days after each inoculation, and tested for antichlamydial IgM and IgG antibodies in the IMIF test using cell culture-propagated, partially purified homologous and heterologous antigens. Nine immunotypes of C. psittaci were distinguished, the correlation between immunotypes and biotypes was close, and a pattern of either disease or host specificity was associated with each immunotype. A modified complement fixation (MoCF) test, an indirect inclusion fluorescence antibody (IIFA) test, and an enzyme-linked immunosorbent assay (ELISA) were developed and evaluated as diagnostic tests for chlamydial abortions in cattle. The pattern of sequential antibody response after experimental chlamydial infection was similar with the three different serological techniques. The MoCF test increased the sensitivity of the standard CF test. However, the IIFA test and ELISA were even more sensitive.