Infection and Immunity, July 2001, p. 4528-4535, Vol. 69, No. 7
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.7.4528-4535.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
-1,2-Glucan Mutants
Have Reduced Virulence in Mice and Are Defective in Intracellular
Replication in HeLa Cells
Instituto de Investigaciones Biotecnológicas, Instituto Tecnológico de Chascomus (IIB-INTECH), Consejo de Investigaciones Científicas y Técnicas, Universidad Nacional de General San Martín (CONICET-UNSAM),1 and Comisión Nacional de Energía Atómica, División Agropecuaria, Centro Atómico Ezeiza,2 Buenos Aires, Argentina
Received 27 September 2000/Returned for modification 9 January 2001/Accepted 22 March 2001
Null cyclic
-1,2-glucan synthetase mutants (cgs
mutants) were obtained from Brucella abortus virulent
strain 2308 and from B. abortus attenuated vaccinal strain
S19. Both mutants show greater sensitivity to surfactants like
deoxycholic acid, sodium dodecyl sulfate, and Zwittergent than the
parental strains, suggesting cell surface alterations. Although not to
the same extent, both mutants display reduced virulence in mice and
defective intracellular multiplication in HeLa cells. The B. abortus S19 cgs mutant was completely cleared from
the spleens of mice after 4 weeks, while the 2308 mutant showed a
1.5-log reduction of the number of brucellae isolated from the spleens
after 12 weeks. These results suggest that cyclic
-1,2-glucan plays
an important role in the residual virulence of the attenuated
B. abortus S19 strain. Although the cgs
mutant was cleared from the spleens earlier than the wild-type parental
strain (B. abortus S19) and produced less
inflammatory response, its ability to confer protection against
the virulent strain B. abortus 2308 was fully
retained. Equivalent levels of induction of spleen gamma interferon
mRNA and anti-lipopolysaccharide (LPS) of immunoglobulin G2a
(IgG2a) subtype antibodies were observed in mice injected with
B. abortus S19 or the cgs mutant. However, the titer of anti-LPS antibodies of the IgG1 subtype induced by the
cgs mutant was lower than that observed with the parental S19 strain, thus suggesting that the cgs mutant
induces a relatively exclusive Th1 response.
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