Cerebral toxoplasmosis in Danish AIDS patients

Incidence, immunological and clinical characteristics of reactivation of latent Toxoplasma gondii infection in HIV-infected patients

To determine changes in incidence of reactivation of Toxoplasma gondii infection, manifesting as toxoplasmic encephalitis, and to assess the immunological mechanisms controlling reactivation in HIV-infected patients, a Czech cohort of 502 HIV/T. gondii co-infected patients was followed for 2909·3 person-years. The incidence of toxoplasmic encephalitis between the periods before and after the introduction of combination antiretroviral therapy (cART) was compared. Toxoplasmic encephalitis was diagnosed in 21 patients. In those patients the geometric mean value of CD4+ T lymphocytes was 12·6 times lower than in patients with non-reactivated T. gondii infection but an additionally significant decline in CD8+ T lymphocytes (3·3-fold) and natural killer cells (4·3-fold) was observed. This confirms the significance of these parameters. A twelvefold decrease in Toxoplasma reactivation incidence (40·2 vs. 3·4/1000 person-years) between monitored periods was seen. In the cART era, Toxoplasma reactivation was observed only in patients with unrecognized HIV infection or refusing therapy.

Effects of 2',3'-dideoxyinosine on Toxoplasma gondii cysts in mice

The activity against Toxoplasma gondii of 2',3' dideoxyinosine (ddI), an anti-human immunodeficiency virus drug, was examined in an in vitro and in vivo study. Cell cultures infected with a strain known to cause chronic infections were used to show the dose-dependent effect of this drug compared with spiramycin and sulfadiazine. When a dose of 4 microg/ml was used, no infected THP-1 cells or parasites were found after 60 h of incubation. An electron-microscopic study confirmed that after 12 h at 1 microg/ml, the few parasites observed were severely altered. The treatment of chronically infected mice 3 months postinfection showed that a 30-day treatment with 2 mg of ddI/ml induced a significant reduction in the number of T. gondii cysts in the cerebral tissue. These cysts were not viable, as confirmed by immunofluorescence and reinfection experiments. These experiments suggest a possible role for ddI in the treatment of toxoplasmosis, and this possibility deserves further investigation.

Risk of toxoplasmic encephalitis in AIDS patients: indications for prophylaxis

To establish the indications for primary prophylaxis against toxoplasmic encephalitis in the Norwegian HIV-positive population, we estimated the incidence of toxoplasmic encephalitis, and related the degree of immunodeficiency and the presence of IgG antibodies against Toxoplasma gondii (T. gondii) to the development of toxoplasmic encephalitis. This retrospective study includes all HIV-positive patients at our hospital from April 1983 to October 1994 (n = 705). A total of 238 patients had AIDS, which represents almost 90% of all AIDS patients in Oslo. Autopsy was done in over 70% of the patients who died during this period; 19 patients developed toxoplasmic encephalitis (8.0%). The median CD4 cell count was 75 x 10(6) cell/I (range 0-280) at the time of diagnosis of toxoplasmic encephalitis. T. gondii serology was studied in 698 (99.0%) of the patients, and was found positive for 17.8%. Of the patients with toxoplasmic encephalitis 18/19 had IgG antibodies against T. gondii and of the 40 AIDS patients who had anti-T. gondii IgG, 18 (45%) developed toxoplasmic encephalitis. We conclude that there is indication for prophylactic treatment of HIV positive patients who have IgG antibodies against T. gondii and who have fewer than 200 x 10(6) CD4 cells/I.

Comparative analysis of intrathecal antibody synthesis and DNA amplification for the diagnosis of cytomegalovirus infection of the central nervous system in AIDS patients

We evaluated 49 paired cerebrospinal fluid (CSF) and serum samples of 35 patients infected with the human immunodeficiency virus type 1 (HIV-1) for laboratory evidence of cytomegalovirus (CMV) infection. The patients were grouped according to clinical criteria as probable CMV encephalitis/polyradiculomyelitis, CMV retinitis, cerebral toxoplasmosis, progressive multifocal leukoencephalopathy, HIV-1-related cognitive/motor complex, HIV-1-associated myelopathy, and other neurological diseases. Paired CSF and serum samples were analysed for CMV deoxyribonucleic acid (DNA) by polymerase chain reaction (PCR), quantitative intrathecal synthesis of immunoglobulin G (IgG) antibodies specific for recombinant phosphoprotein 150 (pp150) of CMV and CMV-specific serum IgM. Intrathecal synthesis of pp150-specific IgG was detected in 26% of patients (9/35), serum IgM was found in 23% of patients (8/35), and PCR of CSF was positive in 11% of patients (4/35). Detection of CMV-specific DNA in CSF preceded the intrathecal antibody synthesis in three patients for whom serial samples were available. PCR results of the CSF became negative in one patient with CMV polyradiculomyelitis after successful therapy with 9-[2-hydroxy-1-(hydroxymethyl) ethoxymethyl] guanine (DHPG). PCR has a higher diagnostic specificity in the acute phase of CMV infection than intrathecal antibody synthesis. The serum IgM response to CMV cannot be used to monitor a compartmentalized immune response in the central nervous system while an intrathecal immune response seems to be associated with recovery either spontaneously or as a result of treatment.