The immune response toNaegleria fowleriamebae and pathogenesis of infection

Abstract

The deletion of CD4- and CD8-double-positive (DP) cells in the thymus after treatment with anti-CD3 antibodies has long been considered as a useful model for clonal deletion during T cell development, although it was reported that DP cell death was not observed in neonates where self-tolerance should be developing. We dealt with the cellular basis of this enigmatic phenomenon in this report. Due to the similar susceptibility to the antibody-treatment in vitro between neonatal and adult thymocytes, critical factors may be outside rather than within the thymus. Indeed, newborn thymus lobes transplanted into recipients of different ages showed an increased susceptibility to the thymo-toxicity as the age of the recipient increased. The thymo-toxicity seems to be based on the adrenal function of glucocorticoid (GC) synthesis, because administration of an inhibitor of GC synthesis significantly reduced the DP cell death by the antibody-treatment. Finally, adrenalectomy completely prevented DP cell death by anti-CD3 antibodies in adult mice. Therefore, the thymocyte death by anti-CD3 antibodies in vivo may not be due to the T cellreceptor mediated selection in the thymus.

Neoparamoeba perurans loses virulence during clonal culture

“…Furthermore, virulence of an Acanthamoeba strain could be restored when the amoeba was passaged through mice (Mazur and Hadaś, 1994). Naegleria fowleri, another well studied free-living amphizoic amoeba that causes primary amoebic meningoencephalitis in humans, was also attenuated when maintained in prolonged axenic culture but virulence was restored following serial passage in mice (Marciano-Cabral and Cabral, 2007).…”

Isolation of Thermotolerant Pathogenic Naegleria australiensis from Diverse Water Resources Including Household Drinking Water in Pakistan

“…However, the widespread presence of thermotolerant Naegleria in water supplies, especially Naegleria lovanensis, which is an indicator species for Naegleria fowleri, suggests this pathogenic amoeba may pose a risk to public health in the area (Marciano-Cabral and Cabral 2007). In support at least 13 PAM cases have already been reported in Karachi, Pakistan, who had no history of aquatic activities and it was believed the infections likely occurred through ablution with tap water (Shakoor et al 2011).…”

“…Free-living amoebae (FLA) are highly diverse and show a worldwide distribution in various environments (Jamerson et al 2009;Behets et al 2007;Marciano-Cabral and Cabral 2007;Gianinazzi et al 2009). Among FLA, Naegleria fowleri is well known to be the cause of primary amoebic meningoencephalitis in humans.…”

Assessment of Knowledge of Medical Students on an Important Health Issue Neagleria Flowri Infection at a Medical College of Karachi, Pakistan

“…It is a thermophilic organism mostly inhabitant of fresh water lakes, hot springs, rivers, ponds and non-chlorinated waters [6]. First discovered in 1989 this organism infects the central nervous system primary and hence commonly known as the brain eating amoeba [7]. Despite the scarcity of this pathogen the case fatality is more than 95% of the cases affected despite advances in antimicrobial therapies [8].…”