Susceptibility to re-infection in C57BL/6 mice with recombinant strains of Toxoplasma gondii

AbstractThis work reports results of re-infection of BALB/c and C57BL/6 mice with different recombinant strains of Toxoplasma gondii. Mice were prime-infected with the non-virulent D8 strain and challenged with virulent strains. PCR–RFLP of cS10-A6 genetic marker of T. gondii demonstrated that BALB/c mice were re-infected with the EGS strain, while C57BL/6 mice were re-infected with the EGS and CH3 strains. Levels of IFN-γ and IL-10 after D8 prime-infection were lower in C57BL/6 than in BALB/c mice. Brain inflammation after D8 prime-infection was more intense in C57BL/6 than in BALB/c mice. It was shown that re-infection depends on mice lineage and genotype of the strain used in the challenge

Self-Mating in the Definitive Host Potentiates Clonal Outbreaks of the Apicomplexan Parasites Sarcocystis neurona and Toxoplasma gondii

Tissue-encysting coccidia, including Toxoplasma gondii and Sarcocystis neurona, are heterogamous parasites with sexual and asexual life stages in definitive and intermediate hosts, respectively. During its sexual life stage, T. gondii reproduces either by genetic out-crossing or via clonal amplification of a single strain through self-mating. Out-crossing has been experimentally verified as a potent mechanism capable of producing offspring possessing a range of adaptive and virulence potentials. In contrast, selfing and other life history traits, such as asexual expansion of tissue-cysts by oral transmission among intermediate hosts, have been proposed to explain the genetic basis for the clonal population structure of T. gondii. In this study, we investigated the contributing roles self-mating and sexual recombination play in nature to maintain clonal population structures and produce or expand parasite clones capable of causing disease epidemics for two tissue encysting parasites. We applied high-resolution genotyping against strains isolated from a T. gondii waterborne outbreak that caused symptomatic disease in 155 immune-competent people in Brazil and a S. neurona outbreak that resulted in a mass mortality event in Southern sea otters. In both cases, a single, genetically distinct clone was found infecting outbreak-exposed individuals. Furthermore, the T. gondii outbreak clone was one of several apparently recombinant progeny recovered from the local environment. Since oocysts or sporocysts were the infectious form implicated in each outbreak, the expansion of the epidemic clone can be explained by self-mating. The results also show that out-crossing preceded selfing to produce the virulent T. gondii clone. For the tissue encysting coccidia, self-mating exists as a key adaptation potentiating the epidemic expansion and transmission of newly emerged parasite clones that can profoundly shape parasite population genetic structures or cause devastating disease outbreaks

Toxoplasma gondii antibodies on domiciled cats from Lages municipality, Santa Catarina State, Brazil Anticorpos contra Toxoplasma gondii em gatos domiciliados no município de Lages, Santa Catarina, Brasil

Sera were collected from 300 domiciled cats from the municipality of Lages, Southern Brazil, to determine the prevalence of Toxoplasma gondii antibodies and risk factors associated. Tests for T. gondii antibodies were performed using indirect immuno&#64258;uorescent antibody test (IFAT). Positive reactions with titers >1:64 were found in 43 (14.33%) cats. A significant number of seropositive cats were >6 month old (p = 0.03758) and had access to the streets or/and rural areas (p = 0.04185). The results indicate that T. gondii is widespread in cats in Lages with a prevalence of 14.33%.<br>Amostras de sangue foram obtidas de 300 gatos domiciliados para determinar a prevalência de anticorpos contra Toxoplasma gondii e possíveis fatores de risco. A detecção de anticorpos da classe IgG foi realizada por meio da Reação de Imunofluorescência Indireta (RIFI). Reações positivas com títulos >1:64 foram encontradas em 43 (14,33%) gatos. Os títulos encontrados variaram de 1:64 a 1:4096, sendo que 19 animais (44,19%) tiveram titulação de 1:64, 18 animais (41,86%) com 1:256, cinco animais (11,63%) com 1:1024 e um animal (2,32%) teve titulação de 1:4096. Foi verificada correlação entre soropositividade dos felinos ao T. gondii e idade (p = 0,03758) e com o acesso à rua e/ou zona rural (p = 0,04185). Os resultados indicam que T. gondii está disseminado entre os gatos domiciliados de Lages, Estado de Santa Catarina, Brasil, com uma prevalência de 14,33%