Entamoeba histolytica is a protozoan parasite that causes amoebic dysentery and liver abscess. E. histolytica relies on motility, phagocytosis, host cell adhesion, and proteolysis of extracellular matrix for virulence. In eukaryotic cells, these processes are mediated in part by phosphatidylinositol 3-kinase (PI3K) signaling. Thus, PI3K may be critical for virulence. We utilized a functional genomics approach to identify genes whose products may operate in the PI3K pathway in E. histolytica. We treated a population of trophozoites that were overexpressing genes from a cDNA library with a near-lethal dose of the PI3K inhibitor wortmannin. This screen was based on the rationale that survivors would be overexpressing gene products that directly or indirectly function in the PI3K pathway. We sequenced the overexpressed genes in survivors and identified a cDNA encoding a Rap GTPase, a protein previously shown to participate in the PI3K pathway. This supports the validity of our approach. Genes encoding a coactosin-like protein, EhCoactosin, and a serine-rich E. histolytica protein (SREHP) were also identified. Cells overexpressing EhCoactosin or SREHP were also less sensitive to a second PI3K inhibitor, LY294002. This corroborates the link between these proteins and PI3K. Finally, a mutant cell line with an increased level of phosphatidylinositol (3,4,5)-triphosphate, the product of PI3K activity, exhibited increased expression of SREHP and EhCoactosin. This further supports the functional connection between these proteins and PI3K in E. histolytica. To our knowledge, this is the first forward-genetics screen adapted to reveal genes participating in a signal transduction pathway in this pathogen. E ntamoeba histolytica is an enteric protozoan parasite that causes amoebiasis and amoebic liver abscess in humans (1). It is prevalent in developing countries that cannot prevent its fecaloral spread. E. histolytica enters the human host upon ingestion of water or food contaminated with environmentally stable cysts. After passing through the stomach, excystation leads to the release of trophozoites, which migrate to the bowel lumen for colonization. In 10% of infected individuals, infection can progress from a noninvasive stage to an invasive stage (2), during which the parasite binds to and destroys colonic epithelium. From here, the parasites enter the circulatory system and translocate to other organs. The most common site of extraintestinal infection is the liver, characterized by the formation of amebic liver abscess (ALA).E. histolytica relies on cell motility, phagocytosis, proteolysis of host extracellular matrix, and host cell adhesion for virulence (3). In other eukaryotic cells, these processes are mediated in part by phosphatidylinositol 3-kinase (PI3K) signaling (4). PI3Ks phosphorylate phosphatidylinositol (PI) and its derivatives to generate signaling lipids such as phosphatidylinositol 3-phosphate (PI3P), phosphatidylinositol 3,4-bisphosphate [PI(3,4)P 2 ], phosphatidylinositol 3,5-bisphosphate [PI(3,5)P 2 ]...

Understanding the magnitude of responses to vaccination during the ongoing SARS-CoV-2 pandemic is essential for ultimate mitigation of the disease. Here, we describe a cohort of 102 subjects (70 COVID-19-naïve, 32 COVID-19-experienced) who received two doses of one of the mRNA vaccines (BNT162b2 (Pfizer–BioNTech) and mRNA-1273 (Moderna)). We document that a single exposure to antigen via infection or vaccination induces a variable antibody response which is affected by age, gender, race, and co-morbidities. In response to a second antigen dose, both COVID-19-naïve and experienced subjects exhibited elevated levels of anti-spike and SARS-CoV-2 neutralizing activity; however, COVID-19-experienced individuals achieved higher antibody levels and neutralization activity as a group. The COVID-19-experienced subjects exhibited no significant increase in antibody or neutralization titer in response to the second vaccine dose (i.e., third antigen exposure). Finally, we found that COVID-19-naïve individuals who received the Moderna vaccine exhibited a more robust boost response to the second vaccine dose (p = 0.004) as compared to the response to Pfizer–BioNTech. Ongoing studies with this cohort will continue to contribute to our understanding of the range and durability of responses to SARS-CoV-2 mRNA vaccines.