A Toxoplasma gondii patatin-like phospholipase contributes to host cell invasion.

Toxoplasma gondii is an obligate intracellular parasite that can invade any nucleated cell of any warm-blooded animal. In a previous screen to identify virulence determinants, disruption of gene TgME49_305140 generated a T. gondii mutant that could not establish a chronic infection in mice. The protein product of TgME49_305140, here named TgPL3, is a 277 kDa protein with a patatin-like phospholipase (PLP) domain and a microtubule binding domain. Antibodies generated against TgPL3 show that it is localized to the apical cap. Using a rapid selection FACS-based CRISPR/Cas-9 method, a TgPL3 deletion strain (ΔTgPL3) was generated. ΔTgPL3 parasites have defects in host cell invasion, which may be caused by reduced rhoptry secretion. We generated complementation clones with either wild type TgPL3 or an active site mutation in the PLP domain by converting the catalytic serine to an alanine, ΔTgPL3::TgPL3S1409A (S1409A). Complementation of ΔTgPL3 with wild type TgPL3 restored all phenotypes, while S1409A did not, suggesting that phospholipase activity is necessary for these phenotypes. ΔTgPL3 and S1409A parasites are also virtually avirulent in vivo but induce a robust antibody response. Vaccination with ΔTgPL3 and S1409A parasites protected mice against subsequent challenge with a lethal dose of Type I T. gondii parasites, making ΔTgPL3 a compelling vaccine candidate. These results demonstrate that TgPL3 has a role in rhoptry secretion, host cell invasion and survival of T. gondii during acute mouse infection.

Survey of college students on iPod use and hearing health.

BACKGROUND: The popularity of personal listening devices (PLDs) including iPods has increased dramatically over the past decade. PLDs allow users to listen to music uninterrupted for prolonged periods and at levels that may pose a risk for hearing loss in some listeners, particularly those using earbud earphones that fail to attenuate high ambient noise levels and necessitate increasing volume for acoustic enjoyment. Earlier studies have documented PLD use by teenagers and adults, but omitted college students, which represent a large segment of individuals who use these devices. PURPOSE: This study surveyed college students' knowledge about, experiences with, attitudes toward, and practices and preferences for hearing health and use of iPods and/or other PLDs. The study was designed to help determine the need, content, and preferred format for educational outreach campaigns regarding safe iPod use to college students. RESEARCH DESIGN: An 83-item questionnaire was designed and used to survey college students' knowledge about, experiences with, attitudes toward, and practices/preferences for hearing health and PLD use. The questionnaire assessed Demographics and Knowledge of Hearing Health, iPod Users' Practices and Preferences, Attitudes toward iPod Use, and Reasons for iPod Use. RESULTS: Generally, most college students were knowledgeable about hearing health but could use information about signs of and how to prevent hearing loss. Two-thirds of these students used iPods, but not at levels or for durations that should pose excessive risks for hearing loss when listening in quiet environments. However, most iPod users could be at risk for hearing loss given a combination of common practices. CONCLUSIONS: Most of these college students should not be at great risk of hearing loss from their iPods when used conscientiously. Some concern is warranted for a small segment of these students who seemed to be most at risk because they listened to their iPods at high volume levels for long durations using earbuds, and reported that they may already have hearing loss due to their iPods.