Bariloche protein symposium argentine society for biochemistry and molecular biology

65
BIOCELL, 27 (Suppl. I), 2003
MI-P22.
IMMUNE SYSTEM RESPONSE, REPRODUCTION, AND
COMPETITION DURING CHAGAS INFECTION
Cossy Isasi, S.
1
; Sibona, G.J.
2
; and Condat, C.A.
3
1
Facultad de Ciencias Medicas, Universidad Nacional de Cordoba,
Cordoba, Argentina, 
2
Institute for Mathematics, University of
Augsburg, Augsburg, Germany, and 
3
Department of Physics,
University of Puerto Rico, Mayaguez, USA, and CONICET and
FaMAF, Universidad Nacional de Cordoba, Cordoba, Argentina.
E-mail: [e-mail]
The biology and pathogenesis of the Chagas disease are not yet
completely understood. Biochemical and anatomopathological
observations in experimental Chagas and in the human disease
indicate a strong involvement of both humoral and cellular
immunities. Recently (J. Theor. Biol. 208, 1-13, 2001), we
presented a model for the interaction between T. cruzi and its
specific antibodies, which includes parasite reproduction, parasite-
generated decoys and immune system learning. The parasite-
antibodies interaction can lead to either the coexistence between
species (chronicity) or to the exclusion of one of them (healing or
death). We have also remarked upon the analogies between
parasite-immune system interactions and virus-immune system
interactions (Comm. Theor. Biol. 8, 1-21, 2003). We now use these
analogies to model the simultaneous action of the humoral and
cellular responses during the Chagas infection. With this extended
model we find the conditions that determine whether one of the
responses becomes dominant or whether a competitive coexistence
develops between the responses. On the other hand, modeling
intracellular amastigotes and invasive tripomastigotes as separate
populations allows us to substantially improve our fittings to the
available data.
MI-P23.
EVALUATION OF THE RECOMBINANT E2
GLYCOPROTEIN OF BOVINE VIRAL DIARRHOEA
VIRUS (BVDV) AS IMMUNOGEN IN CATTLE
Chimeno Zoth, S.A.
1
; Morrell, E.
2
; Leunda, M.R.
2
; Cantón, G.
2
;
Ferrer, M.F.
1
; Taboga, O.A.
1
; Odeón, A.C.
2
; Piccone, M.E.
1
1
Instituto de Biotecnología. INTA-Castelar. 
2
Dpto. Sanidad Animal.
INTA-Balcarce. E-mail: [e-mail]
Bovine viral diarrhoea virus  (BVDV) is a member of the pestivirus
genus, within the Flaviviridae family. This RNA virus is an
important pathogen of cattle, causing significant economic losses
world-wide. The E2 envelope glycoprotein is highly antigenic and
elicits the production of neutralizing antibodies in the host after
vaccination with live or killed vaccines. In previous reports, we
expressed E2 in Sf9 insect cells. When mice and rabbits were
immunized with the recombinant E2, it demonstrated to have
immunological properties similar to those of the native viral
protein. The aim of this work was to determine the serological
responses of cattle to the recombinant E2 glycoprotein and the
protection against challenge. Animals were immunized with
cellular extracts obtained from Sf9 infected with recombinant
baculovirus expressing E2 and they were challenged with NADL
strain of BVDV. Clinical parameters were recorded daily and
samples of serum were evaluated by neutralization test. Viral
isolation was performed from buffy coat, nasal and ocullar swabs.
Animals immunized with recombinant E2 developed higher
neutralizating antibodies titers which increased in shorter time
than control groups (one of which included an inactivated vaccine).
These results indicate that E2 expressed in Sf9 cells stimulated a
specific BVDV neutralizing response that lasted for at least 5
months post vaccination.
MI-P24.
A NOVEL SYSTEM TO SCREEN TRYPANOSOMATID
ADENYLYL CYCLASE INHIBITORS IN
SCHIZOSACCHAROMYCES POMBE
D´Angelo, M.
1
; Llorente, B.
1
; Alonso, G.
1
; Birnbaumer, L.
2
; Torres,
H.
1
 and Flawiá, M.
1
1
INGEBI, Buenos Aires, Argentina. 
2
NIEHS, NC, USA. E-mail:
[e-mail]
Adenylyl cyclases have a key role in the differentiation of T. cruzi.
Therefore, these enzymes could be exploited as therapeutic targets
for the treatment of Chagas Disease. However, the adenylyl cyclase
multiplicity of these parasites exclude the possibility of
characterizing the inhibition of a single isoform. To overcome this
problem we decided to express TczAC in a S. pombe mutant strain
that contains the endogenous adenylyl cyclase gene deleted and
the  lacZ and URA4 genes inserted under a cAMP repressible
promoter. Thus changes in cAMP levels can be monitored by a
decrease of â-gal activity and by growth in 5´-FOA (a toxic drug
for URA4 expressing cells). TczAC was first expressed in mutant
yeasts under the control of a strong promoter. Transformed cells
showed less â-gal activity and cells were longer than the control
ones. TczAC was then expressed under two weaker promoters.
Similar to the adenylyl cyclase activity, the length of the cells
diminished with the decrease of promoter strength. On the other
hand, the â-gal activity showed the opposite behavior. All together
these results suggest that the expression of trypanosomatid adenylyl
cyclases in this S. pombe strain could be useful to screen specific
inhibitors of single enzyme isoform.
MI-P25.
GROWTH-PHASE MODIFIED THE UVA RESPONSE OF
E. coli: INFLUENCE OF CONDITIONED MEDIA,
ACETATE AND HYDROGEN PEROXIDE
Dantur K., Pizarro R.
CNEA. Dep. Radiobiología. E-mail: [e-mail]
Results reported here indicate that UVA radiation induces
deleterious effects in E. coli, depending on the growth phase.
Stationary-phase cells recover faster from a sub-lethal UVA
exposure and have a higher resistance to lethal effect of the
radiation than exponential growing cells. Although pre-incubation
in spent medium supernatant increased the resistance of log-phase
cells to lethal UVA effects, this pre-treatment considerably
prolonged the duration of the radioinduced sub-lethal growth delay.
Our purpose was to investigate the effect exerted by the E. coli
conditioned media and the influence of nutritional stress, hydrogen
peroxide and acetate was determined. Preincubated in conditioned
medium, exponential growing cells were irradiated and the induced
effects were compared with those found when catalase, high culture
densities and acetate were added. Unexpectedly, the duration of
growth delay in cells submitted to these treatments was shortened
in comparison with control cells incubated in conditioned medium
with no modifications. Enlargement of the growth delay was
mimicked when exponentially growing cells were incubated in
fresh medium supplied with 5ì M H
2
O
2
. The effects of spent
medium on wild type and rpoS (oxidative stress response) were
similar, indicating that this response is independent of RpoS
controlled functions. We assumed that an oxidative component of
the spent medium, probably H
2
O
2
, could be involved in the
observed phenomenon, this effect is specific of E. coli and
independent of rpoS.

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