Pregnancy, immunosupression and reactivation of latent toxoplasmosis

Abstract

Toxoplasmosis is a chronic, latent infection which can be reactivated in the presence of immunosuppression. The critical question in obstetrics is whether toxoplasmosis may be reactivated in the presence of the physiological "immunosuppression" of pregnancy. Standard in vitro tests, done in 24 healthy pregnant women and compared with the literature, show no significant changes in humoral and cellular immunity during pregnancy. However, the fact that some infections occur more frequently and more severely than in non-pregnant women (e.g. those due to cytomegalovirus (CMV) and human papilloma virus (HPV) points to a degree of pregnancy-associated immunosuppression. Non-rejection of the semiallogenic fetus is achieved in presence of maternal immunocompetence and is explained mainly by local changes in immune function, mediated by inhibitors of decidual, placental and fetal origin, and by the absence of class II histocompatibility antigens at the fetomaternal interface. Immune status allowing reactivation of toxoplasmosis was studied in a selected group of (predominantly male) AIDS patients from the Swiss HIV Cohort study. Shortly before (cerebral) reactivation of toxoplasmosis, 92% of these patients had very low CD4 lymphocyte counts (mean 50 cells/microliters, i.e. lower than ever recorded in a normal uncomplicated pregnancy). In a larger population of 48 women receiving immunosuppressive therapy after organ transplantation, not a single case of cerebral toxoplasmosis was observed during pregnancy, while in the 105 HIV-positive women in the Swiss HIV and Pregnancy study, there was only one case of cerebral toxoplasmosis during pregnancy and the puerperium (20 CD4/microliters), even though some 17% of those sampled (18/105) had CD4 levels below 200 cells/microliters on at least one occasion during pregnancy. These findings explain why latent toxoplasmosis is not reactivated in normal pregnancy, and why it is only likely in an immunosuppressed mother when her CD4 lymphocyte count is very low (< 200 cells/microliters). In such cases, a prophylactic treatment to prevent maternal reactivation and vertical transmission of toxoplasmosis may be useful.

Toxoplasmosis in HIV/AIDS Patients - A Living Legacy

“…A case of CT was earlier reported in an HIV-infected pregnant woman who responded well with a standard regimen of pyrimethamine and sulfadiazine, with a normal fetal outcome (Hedriana et al, 1993). Another case of CT was confirmed in an HIV-infected pregnant woman during the puerperium with her CD4 count being < 200 cells/cumm (Biedermann et al, 1995). A prophylactic treatment was recommended to prevent maternal reactivation and congenital transmission of toxoplasmosis in such a case.…”

Infection of Placental Trophoblasts byToxoplasma gondii

“…Antimicrobial treatment after maternal seroconversion is ineffective, possibly because transmission may occur before detection of seroconversion or because of antibiotic catabolism [6][7][8][9]. Reactivation of latent disease, secondary to maternal immunosuppression (such as AIDS) or corticosteroid therapy, may also result in fetal infection [10]. Severity of the disease correlates with the extent of placental damage [11].…”

Sero–Prevalence, and Associated Risk Factors of Toxoplasma gondii Infection in Pregnant Women and HIV/AIDS Patients in Selected Cities of Ethiopia

“…The high seroprevalence of toxoplasmosis in HIV infected patients might partly be due to early child hood and teenage infection. In contrast, Biedermann [BIEDERMANN et al, 1995] and Woldemichael [WOLDEMICHAEL et al, 1998] reported similar seroprevalence rates between HIV infected individuals and normal controls. As age increased, it was observed that there was a relative increase in seroprevalence due to exposure to infective stages of parasite.…”