Potential immunomodulatory effects of latent toxoplasmosis in humans

Abstract

BackgroundAbout 30% of the population worldwide are infected with the protozoan parasite Toxoplasma gondii. Latent toxoplasmosis has many specific behavioral and physiological effects on the human organism. Modified reactivity of the immune system has been suggested to play a key role in many of these effects. For example, the immunosuppression hypothesis explains the higher probability of the birth of male offspring observed in Toxoplasma-positive humans and mice by the protection of the (more immunogenic) male embryos against abortion.MethodsHere we searched for indices of immunosuppression in Toxoplasma-positive subjects by comparing clinical records of immunology outpatients.ResultsOur cohort study showed that the male patients with latent toxoplasmosis had decreased and the Toxoplasma-positive women had increased leukocyte, NK-cell and monocyte counts in comparison with controls. The B-cell counts were reduced in both Toxoplasma-positive men and women. The difference between Toxoplasma-positive and Toxoplasma-negative subjects diminished with the decline of the specific Toxoplasma antibody titre (a proxy for the length of infection), which is consistent with the observed decreasing strength of the effect of latent toxoplasmosis on human reproduction. The prevalence of toxoplasmosis in 128 male patients was unusually low (10.9%) which contrasted with normal prevalence in 312 female patients (23.7%) and in general population Prague (20-30%).ConclusionsLatent toxoplasmosis has immunomodulatory effects in human and probably protects men against some classes of immunopathological diseases. The main limitation of the present study was the absence of the data on the immunoreactivity of immune cells subpopulations. Therefore further studies are needed to search for indices of immunosuppression in human using more specific markers.

Influence of latentToxoplasmainfection on human personality, physiology and morphology: pros and cons of theToxoplasma–human model in studying the manipulation hypothesis

“…Infected men rated the smell of cat urine as relatively more pleasant while infected women rated it as relatively less pleasant compared with noninfected controls (Flegr et al, 2011). Using urine from four other animal species (tiger, dog, horse, brown hyena), a similar but weaker effect was observed for hyena urine.…”

“…The children of Toxoplasma-infected mothers have lower rates of motor development in the first 18months of life (Kaňková et al, 2012). Most differences in the reproductionassociated traits between infected and non-infected women can be explained as being a result of immunosuppression and the resulting (expected) decrease in the stringency of embryo quality control (Neuhäuser and Krackow, 2007), which has been observed in both humans (Flegr and Stříž, 2011) and mice (Kaňková et al, 2010a) with latent toxoplasmosis. A large proportion of embryos with various developmental defects, as well as a large percentage of more immunogenic male embryos, are aborted in the early weeks of pregnancy.…”

“…It is, however, possible that chance strongly influences which of the urine samples is active in the fatal attraction test. In our study (Flegr et al, 2011), samples of five individuals of each species were used in smellrating experiments. However, the relative attractiveness of particular samples can still depend on the sample concentration and the time elapsed from sample collection.…”

Physical and Mental Health Status in Toxoplasma-Infected Women before and 3 Years after They Learn about Their Infection: Manipulation or Side-Effects of Impaired Health?

“…At the same time, psychomotor performance of infected Rh-positive homozygotes and especially of infected Rh-negative homozygotes was much poorer than that of corresponding controls (Novotná et al, 2008). It has been shown that toxoplasmosis has various effects on human physiology and some of these effects, such as increase of testosterone (Flegr et al, 2008a,b) or partial immunosuppression (Flegr and StříŽ, 2011), could have a positive impact on human performance and health in certain situations. It must be remembered that our population of Rh-positive women represents a mixture of homozygotes and heterozygotes.…”

Toxoplasmosis, but not borreliosis, is associated with psychiatric disorders: A cross-sectional survey on 46 thousand of subjects

“…It is known, however, that latent toxoplasmosis has specific immunomodulatory effects on immune system of infected humans and mice (Flegr and Stříž, 2011;Kaňková et al, 2010) which could influence the risk and the course of other infections such as borreliosis. An alternative explanation could be based on the hypothesis of the existence of a vector shared by both pathogens.…”