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Biomedical subjects

M Hewish

Publications and source records attributed to M Hewish.

4 recordsLinked to original sources

Agglutinating antibodies to Toxoplasma gondii in sera from captive eastern barred bandicoots in Australia.

Toxoplasmosis is considered a severe health risk for many marsupial species. The mainland Australian population of bandicoot is endangered. Therefore, a preliminary serosurvey was conducted to evaluate exposure to Toxoplasma gondii in 57 captive eastern barred bandicoot and to estimate the possible impact of Toxoplasma on recovering populations. Five (9%) bandicoot were classified as seropositive using a modified agglutination test. Nineteen additional bandicoot (33%) were classified as serosuspect using a direct agglutination test. No bandicoot showed signs of clinical disease. Seropositive titers were IgG associated, suggesting that infections were chronic and latent. Serostatus was not associated with either sex or being wild-caught, although each seropositive bandicoot was wild-caught. Seropositive animals ranged from 1.25- to 2.5-yr-old. Computer simulations using Vortex 5.1, based on the proportion of seropositive and seronegative bandicoot in this study, indicate that mortalities from T. gondii should have little impact upon captive populations. However, the potential impact of toxoplasmosis on recovery efforts for wild, mainland bandicoot populations is not clear.

Agglutination Tests↗

HIV-1 infection of human macrophages impairs phagocytosis and killing of Toxoplasma gondii.

The susceptibility of patients with AIDS to certain opportunistic infections is due to defective cell-mediated immunity. The contribution of direct infection of macrophages with HIV-1 to this defect is unknown. To address this issue, we infected normal human monocyte-derived macrophages with a monocytotropic strain of HIV-1 and examined their ability to phagocytose and kill the opportunistic pathogen, Toxoplasma gondii. Phagocytosis of heat-killed T. gondii was reduced in HIV-infected macrophages compared with mock-infected controls. Opsonization of heat-killed T. gondii increased phagocytosis by both mock- and HIV-infected macrophages, but phagocytosis in HIV-infected cultures remained lower than in controls. Internalization of live T. gondii by macrophages was unaffected by HIV infection. Intracellular replication of live T. gondii was enhanced by HIV infection, as shown in four experiments, each using monocyte-derived macrophages from a different donor. Treatment of HIV-infected macrophages with IFN-gamma decreased parasite replication but not to control levels. These findings suggest that infection of macrophages by HIV may be a contributing factor to the reactivation of T. gondii infection in patients with AIDS.

Animals↗