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Infect. Immun., 07 1996, 2431-2439, Vol 64, No. 7
NF Cheville, SC Olsen, AE Jensen, MG Stevens, AM Florance, HS Houng, ES Drazek, RL Warren, TL Hadfield and DL Hoover
To evaluate host responses, young goats were inoculated subcutaneously with
a genetic deletion mutant (deltapurE201) of Brucella melitensis (n = 6),
its virulent parental strain 16M (n = 6), or saline (n = 6). No clinical
evidence of brucellosis was seen in any goat. Serum antibody titers peaked
at postinoculation day (PID) 14. Bacteria in lymph nodes that drained sites
of vaccination reached peak numbers of >10(6) CFU/g in both infected
groups at PID 7 and progressively declined to PID 84. At necropsy, bacteria
were present in mammary lymph nodes or spleen of 33% of goats given
virulent 16M but in none of goats given the purE mutant. Lymphadenitis,
most severe in goats given 16M, involved depletion of lymphocytes and
germinal centers, proliferation of lymphoblasts, and vasculitis. By PID 28,
lymph node architecture was restored; there was marked germinal center
formation and medullary plasmacytosis. Brucellar antigens, detected with
immunoperoxidase techniques, were prominent in capsular granulomas but not
in lymph node cortices. Ultrastructurally, bacteria were found in
macrophages (>97%) and small lymphocytes (<3%) but not in large
lymphocytes. Bacteria were intact in small lymphocytes but in macrophages
were in various stages of degradation. The deltapurE phenotype of
deltapurE201 was preserved during infection of goat lymph nodes. Unlike
Salmonella spp. purE mutants, strain deltapurE201 may be a candidate for
efficacy testing; it produced immune responses, was cleared from visceral
tissues, and produced less severe pathologic changes than its wild-type
parent.
Copyright © 1996, American Society for Microbiology
Bacterial persistence and immunity in goats vaccinated with a purE deletion mutant or the parental 16M strain of Brucella melitensis
National Animal Disease Center, U.S. Department of Agriculture, Ames, Iowa 50010, USA.
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