👤 Merlyn Emmanuel

Concerns remain regarding the heterogeneity in overlapping human immunodeficiency virus (HIV) risk behaviors among sex workers (SWs) in Pakistan; specifically, the degree to which SWs interact with people who inject drugs (PWID) through sex and/or needle sharing.Following an in-depth mapping performed in 2011 to determine the size and distribution of key populations at highest risk of HIV acquisition in Pakistan, a cross-sectional biological and behavioral survey was conducted among PWID, female (FSWs), male (MSWs), and hijra/transgender (HSWs) sex workers, and data from 8 major cities were used for analyses. Logistic regression was used to identify factors, including city of residence and mode of SW-client solicitation, contributing to the overlapping risks of drug injection and sexual interaction with PWID.The study comprised 8483 SWs (34.5% FSWs, 32.4% HSWs, and 33.1% MSWs). Among SWs who had sex with PWID, HSWs were 2.61 (95% confidence interval [CI], 1.19-5.74) and 1.99 (95% CI, 0.94-4.22) times more likely to inject drugs than MSWs and FSWs, respectively. There was up to a 3-fold difference in drug injecting probability, dependent on where and/or how the SW solicited clients. Compared with SWs in Larkana, the highest likelihood of drug injection use was among SWs in Multan (OR = 4.52; 95% CI: 3.27-6.26), followed by those in Lahore, Quetta, and Faisalabad.Heterogeneity exists in the overlapping patterns of HIV risk behaviors of SWs. The risk of drug injection among SWs also varies by city. Some means of sexual client solicitation may be along the pathway to overlapping HIV risk vulnerability due to increased likelihood of drug injection among SWs. There is a need to closely to monitor the mixing patterns between SWs and PWID and underlying structural factors, such as means of sexual client solicitation, that mediate HIV risk, and implement prevention programs customized to local subepidemics. Show less

The protozoan parasite Entamoeba histolytica causes a wide spectrum of intestinal infections. In severe cases, the trophozoites can breach the mucosal barrier, invade the intestinal epithelium and travel via the portal circulation to the liver, where they cause hepatic abscesses, which can prove fatal if left untreated. The host Extra Cellular Matrix (ECM) plays a crucial role in amoebic invasion by triggering an array of cellular responses in the parasite, including induction of actin rich adhesion structures. Similar actin rich protrusive structures, known as 'invadosomes', promote chemotactic migration of the metastatic cancer cells and non-transformed cells by remodeling the ECM. Recent studies showed a central role for Rab GTPases, the master regulators of vesicular trafficking, in biogenesis of invadosomes. Here, we showed that fibronectin, a major host ECM component induced actin remodeling in the parasite in a Rab21 dependent manner. The focalized actin structures formed were reminiscent of the mammalian invadosomes. By using various approaches, such as immunofluorescence confocal microscopy and scanning electron microscopy, along with in vitro invasion assay and matrix degradation assay, we show that the fibronectin induced formation of amoebic actin dots depend on the nucleotide status of the GTPase. The ECM components, fibronectin and collagen type I, displayed differential control over the formation of actin dots, with fibronectin positively and collagen type I negatively modulating it. The cell surface adhesion molecule Gal/GalNAc complex was also found to impose additional regulation on this process, which might have implication in collagen type I mediated suppression of actin dots. Show less

We used a panel of recombinant human apolipoprotein (apo) A-IV truncation mutants, in which pairs of 22-mer alpha-helices were sequentially deleted along the primary sequence, to examine the impact of protein structure and interfacial activity on the ability of apoA-IV to activate cholesterol ester transfer protein. Circular dichroism and fluorescence spectroscopy revealed that the secondary structure, conformation, and molecular stability of recombinant human apoA-IV were identical to the native protein. However, deletion of any of the alpha-helical domains in apoA-IV disrupted its tertiary structure and impaired its molecular stability. Surprisingly, determination of the water/phospholipid interfacial exclusion pressure of the apoA-IV truncation mutants revealed that, for most, deletion of amphipathic alpha-helical domains increased their affinity for phospholipid monolayers. All of the truncation mutants activated the transfer of fluorescent-labeled cholesterol esters between high and low density lipoproteins at a rate higher than native apoA-IV. There was a strong positive correlation (r = 0.790, p = 0.002) between the rate constant for cholesterol ester transfer and interfacial exclusion pressure. We conclude that molecular interfacial exclusion pressure, rather than specific helical domains, determines the degree to which apoA-IV, and likely other apolipoproteins, facilitate cholesterol ester transfer protein-mediated lipid exchange. Show less

To gain insight into the evolution and function of apolipoprotein A-IV (apoA-IV) we compared structural and interfacial properties of chicken apoA-IV, human apoA-IV, and a recombinant human apoA-IV truncation mutant lacking the carboxyl terminus. Circular dichroism thermal denaturation studies revealed that the thermodynamic stability of the alpha-helical structure in chicken apoA-IV (DeltaH = 71.0 kcal/mol) was greater than that of human apoA-IV (63.6 kcal/mol), but similar to that of human apoA-I (73.1 kcal/mol). Fluorescence chemical denaturation studies revealed a multiphasic red shift with a 65% increase in relative quantum yield that preceded loss of alpha-helical structure, a phenomenon previously noted for human apoA-IV. The elastic modulus of chicken apoA-IV at the air/water interface was 13.7 mN/m, versus 21.7 mN/m for human apoA-IV and 7.6 mN/m for apoA-I. The interfacial exclusion pressure of chicken apoA-IV for phospholipid monolayers was 31.1 mN/m, versus 33.0 mN/m for human A-I and 28.5 mN/m for apoA-IV. We conclude that the secondary structural features of chicken apoA-IV more closely resemble those of human apoA-I, which may reflect the evolution of apoA-IV by intraexonic duplication of the apoA-I gene. However, the interfacial properties of chicken apoA-IV are intermediate between those of human apoA-I and apoA-IV, which suggests that chicken apoA-IV may represent an ancestral prototype of mammalian apoA-IV, which subsequently underwent further structural change as an evolutionary response to the requisites of mammalian lipoprotein metabolism. Show less