Ivermectin modulated cerebral γ-aminobutyric acid (GABA) and reduced the number of chronic Toxoplasma gondii cysts significantly in the brains of immunocompromised mice

Disruption of GABAergic signaling could exaggerate the inflammatory reaction associated with Toxoplasma gondii infection, as well as produce neurophysiological consequences including seizures that occur within the brain tissues. The current study aimed to evaluate the efficacy of ivermectin (IVM) in treating latent cerebral toxoplasmosis and define its role in the neuromodulation of cerebral tissue GABA expression, conducted in an immunocompromised dexamethasone-treated mouse model infected with the ME49 Toxoplasma strain. The control (non-infected non-treated) group showed a mean of 22.1 ± 0.71 for local expression of GABA. Significantly lower expression (3.78 ± 1.38) was recorded in the infected non-treated group (p ≤ 0.05). On the contrary, a significantly higher expression was reported in the group infected and treated with IVM than in the infected non-treated group (19.8 ± 0.8). While the infected spiramycin (SP)-treated group reported a significantly lower level than the control. Non-infected groups that received only IVM or SP recorded 22.3 ± 0.45 and 22 ± 0.89 respectively with no significant difference. IVM is shown in this work, not only to reduce the size and the number of Toxoplasma cystic lesions within the brain significantly with a reduction rate of 68.85% but to also increase the level of GABA local expression significantly in addition to improving cerebral histopathology. Thus, IVM by its ability to modulate GABA expression may improve such clinical situations, if used as a treatment either exclusively or in combination with other medications.

Pathological changes in acute experimental toxoplasmosis with Toxoplasma gondii strains obtained from human cases of congenital disease

There is a lack of studies using Toxoplasma gondii strains isolated from human patients. Here, we present a pathological study of three strains obtained from human cases of congenital toxoplasmosis in Brazil using inbred mice after oral infection with 10 tissue cysts. Multiplex-nested PCR-RFLP of eleven loci revealed atypical genotypes commonly found in Brazil: toxodb #8 for TgCTBr5 and TgCTBr16 strains and toxodb #11 for the TgCTBr9 strain. BALB/c and C57BL/6 mice were evaluated for survival and histological changes during the acute phase of the disease. All mice inoculated with the non-virulent TgCTBR5 strain survived after 30 days, although irreversible tissue damage was found. In contrast, no mice were resistant to infection with the highly virulent TgCTBR9 strain. The TgCTBr16 strain resulted in 80% survival in mice. However, this strain presented low infectivity, especially by the oral route of infection. Despite being identified with the same genotype, TgCTBr5 and TgCTBr16 strains showed biological differences. Histopathologic analysis revealed liver and lungs to be the most affected organs, and the pattern of tissue injury was similar to that found in mice inoculated perorally with strains belonging to clonal genotypes. However, there was a variation in the intensity of ileum lesions according to T. gondii strain and mouse lineage. C57BL/6 mice showed higher susceptibility than BALB/c for histological lesions. Taken together, these results revealed that the pathogenesis of T. gondii strains belonging to atypical genotypes can induce similar tissue damage to those from clonal genotypes, although intrinsic aspects of the strains seem critical to the induction of ileitis in the infected host.

Pathobiology of human RH strain induced experimental toxoplasmosis in murine model

Of late, toxoplasmosis has gained immense importance as an opportunist parasite in immunocompromised patients. In immunocompromised subjects, the disease is supposed to occur in acute form and causes acute toxoplasmic encephalitis. However, the exact pathogenesis of other vital organs, particularly in acute form of infection, is still a matter of debate. Therefore, an attempt was made to study the pathogenesis of acute form of toxoplasmosis using cryopreserved human RH strain of the parasite in murine models. For this, 100 tachyzoites were given to individual mice and upon the setup of acute form of infection, the mice were euthanized and the organs were processed for histopathology. Histopathology revealed tachyzoites in liver only while severe necrosis due to multiplication of tachyzoites were visible in liver, spleen, lungs and brain. Kidneys and heart appeared more or less normal. Finally, the pathology of disease in these organs is described in detail. The present research has generated some vital information regarding necrotic changes in tissues due to acute toxoplasmosis and will defiantly help the researchers in the better understanding of disease particularly in humans and putting up of suitable treatment regime for human subjects infected with acute toxoplasmosis.

An Insight into the Behavior, Course and Kinetics of Acute Infection of Toxoplasma gondii Human RH Strain in Experimentally Infected Murine Model

BACKGROUND

Toxoplasma gondii, an apicomplexan parasite, is capable of infecting a broad range of intermediate warm-blooded hosts including humans. The parasite seems to be capable of altering the natural behavior of the host to favor its transmission in the environment. The aim of this study was to evaluate the course, alterations in behavior along with normal kinetics of the abnormally induced experimental acute toxoplasmosis in murine models.

METHODS

Ten Swiss albino mice were intraperitoneally inoculated with 100 virulent RH strain tachyzoites and finally, the alterations in behavior were described and compared with other known alterations in humans and animals.

RESULTS

The behavior and the other symptoms of the acute toxoplasmosis were recorded. Such mice showed typical symptoms like normal coat, severe ascites with pendulous abdomen and tachypnoea exhibited by resting fore legs either on walls of the cage, or nozzle of water bottle or other resting mice and yielded a creamy colored cloudy natured peritoneal fluid on aspiration.

CONCLUSIONS

Finally the alterations in behavior were described and compared with other known alterations in humans and animals. The study has generated some important data related to possible causes of behavioral alterations and generation of suitable strategies for control of these alterations in behavior vis-à-vis better understanding of the effect of acute infection of parasite on normal behavior of infected intermediate host.

Kinetics and time dependence of the differential agglutination of acetone [AC]- and formalin [HS]-fixed Toxoplasma tachyzoites by serum of mice with experimental toxoplasmosis

Researches to specify a serologic diagnostic test capable of determining the stage of toxoplasmosis, whether recent or latent, have been hampered by lack of knowing the real time of infection. Studying the precise kinetics of the differential agglutination of acetone [AC]-fixed versus that of formalin [HS]-fixed tachyzoites (differential agglutination test or AC/HS test) by sera of mice during the course of toxoplasmosis and assessment of its value in the differentiation between recent and latent infections in mice were the aims of the present work. Experimental toxoplasmosis was induced in mice, sera were collected sequentially and AC/HS test, FAST-ELISA to determine levels of IgM and IgG and microscopic examination of brain for Toxoplasma cysts were done. Both AC and HS specific patterns in the AC/HS test were noted to be dependent on the time from the onset of infection. Acute patterns of the AC/HS test were observed early in infection till before the appearance of brain cysts. Non-acute patterns were obtained late on 28th day post infection coinciding with the disappearance of IgM, persistence of IgG and presence of cysts in brains. The AC antibody was high in the recent phase of infection, and then it declined to be replaced by high sustained level of HS antibody late in infection. In conclusion, in the presence of both IgM and IgG, the appearance of either equivocal pattern or the non-acute pattern in the AC/HS test is significant in ruling out acute infection in mice.