Impacto de infec??es mistas por clones de Trypanosoma cruzi pertencentes aos grupos gen?ticos principais sobre propriedades biol?gicas do parasito em camundongos BALB/C.

Oito estoques clonais de Trypanosoma cruzi, dois de cada umdos gen?tipos principais 19 e 20 (T. cruzi I), 39 (h?brido) e 32 (T. cruziII) foramcombinados em24 infec??es mistas diferentes e estudadas emcamundongos BALB/c. Emcada uma das infec??es mistas, os animais foraminoculados com5.000 tripomastigotas sangu?neos de cada clone por animal e comparados coma corresponde infec??o monoclonal cujo in?culo foi de 10.000 tripomastigotas do clonepor animal. Foramanalisados oito par?metros: percentual de infectividade, percentual de mortalidade e percentual de positividade da hemocultura, per?odo pr?-patente, per?odo patente, pico m?ximode parasitemia, dia do pico m?ximode parasitemia e parasitemia. Tr?s compara??es foram realizadas: (a) infec??o monoclonal x infec??omista baseada nos valores esperados (b) infec??o monoclonal x infec??o mista baseada nos valores observados (c) valores esperados x valores observados para as infec??es mistas. Ocorreramdiferen?as significativas na maioira dos par?metros estudados, tendo sido observadas diferentes percentagens de altera??es, variando de 4,2 a 79,2%. A parasitemia foi o par?metro que apresentou maior pencentagemde altera??o ocorrendo empraticamente todas as combina??es genot?picas de T. cruzi. Foi observado aumento significativo e moito misturas e diminui??o em11, representando altera??es em19 das 24 combina??es. Em umdos casos, foi observado efeito inibit?rio rec?proco completo de umclone sobre o outro. A an?lise dos outros quatros par?metros assosiados a parasitemia tamb?m demonstraramdiferen?as significativas entre os valores observados e esperados nas infec??es duplas emdiferentes propor??es: 45.83% para PPP, 62.5% para PP, 66.6% para PMP e 33.3% para DPMP. Quando esses par?metros foramconsiderados em conjunto, 11, 14, 11, 11, 15 e seis diferen?as entre os valores observados e esperados foramdetectadas nas combina??es genot?picas 19+20, 19+39 19+32, 20+39, 39+32 e 20+32, respectivamente. O menor n?mero de diferen?as significativas ocorreu exatamente na mistura 20+32, comclones filogeneticamente mais distantes e biologicamente mais distintos. Esses resultados enfatizama import?ncia de se considerar a possibilidade de ocorr?ncia de infec??es mistas e suas conseq??ncias para o hospedeiro, na patog?nese e na evolu??o da doen?a de Chagas.Eight Trypanosoma cruziclonal stocks, two of each principal T. cruzigenotypes 19 and 20 (T. cruzi I) and 39 (hybrid) and 32 (T. cruziII) were combined in 24 different double infections and studied in BALB/c mice.For the mixed infections, animals were inoculated with 5.000 blood trypomastigotes of each clone and compared with the correspondent monoclonal infection whose animals were inoculated with 10.000 blood trypomastigotes of the clone. Eight parameters were analyzed: percentage of infectivity, percentage of mortality, percentage of positive hemoculture, pre-patent period, patent period, maximumof parasitemia, day of maximumof parasitemia and parasitemia. Three comparisons were considered: (a) monoclonal infection x mixed infection based on expected values; (b) monoclonal infection x mixed infection based on observed values and (c) expected x observed values for mixed infections. Significant differences occurred in the majority of the studied parameters. It was observed different percentages of alterations with rates that varied from4,2% to 79,2%, except for infectividade and mortality. Differences of parasitemia occurred in almost all T. cruzigenotypes combinations. Significant increase (eight mixtures) and decrease (11 mixtures) of parasitemia occurred in 19 out of 24 combinations. In one case, it was observed a complete and reciprocal inhibitory effect of one clone to another. The analysis of others four parameters associated with parasitemia also showed significant differences between the expected and observed values indouble-infections in different proportions: 45.83% for PPP, 62.5% for PP, 66.6% for MP and 33.3% for DMP. When all parameters were considered together, 12, 14, 11, 11, 15 and six significant differences between the expected and observed values were detected in the genotypes combinations 19+20, 19+39 19+32, 20+39, 39+32 and 20+32 respectively. The lowest number of significant differences occurred exactly in the mixture 20+32, with clones more phylogenetically distant and biologically different. These results emphasize the importance ofto consider the possibility ofoccurrence ofmixed infections and their consequences to the host, on the pathology and on Chagas disease evolution