Biophysical Properties of Bifunctional Phage-Biosensor

Biosensor research is a swiftly growing field for developing rapid and precise analytical devices for biomedical, pharmaceutical, and industrial use and beyond. Herein, we propose a phage-based biosensor method to develop a sensitive and specific system for biomedical detection. Our method is based on in vitro selected phages and their interaction with the targeted analytes as well as on optical properties that change according to the concentration of the model analyte. The green fluorescent protein (GFP) was chosen as our model analyte as it has its own well-known optical properties. Brilliant green was used as a reporter component for the sensor. Its presence enables a color intensity (absorbance) change when the analyte is present in the solution. Furthermore, the reporter dye functioned as a quencher for an additional lanthanide label in our assay. It mediated the specific phage-derived interference in the signal measured with the time-resolved luminescence. Most importantly, our results confirmed that the presented bifunctional phage with its liquid crystal properties enabled the measurement of GFP in a concentration-dependent, quantitative manner with a limit of detection of 0.24 µg/mL. In the future, our novel method to develop phage-based biosensors may provide highly sensitive and specific biosensors for biomedical or otherwise-relevant targets.

The transcriptome of circulating sexually committed Plasmodium falciparum ring stage parasites forecasts malaria transmission potential

Malaria is spread by the transmission of sexual stage parasites, called gametocytes. However, with Plasmodium falciparum, gametocytes can only be detected in peripheral blood when they are mature and transmissible to a mosquito, which complicates control efforts. Here, we identify the set of genes overexpressed in patient blood samples with high levels of gametocyte-committed ring stage parasites. Expression of all 18 genes is regulated by transcription factor AP2-G, which is required for gametocytogenesis. We select three genes, not expressed in mature gametocytes, to develop as biomarkers. All three biomarkers we validate in vitro using 6 different parasite lines and develop an algorithm that predicts gametocyte production in ex vivo samples and volunteer infection studies. The biomarkers are also sensitive enough to monitor gametocyte production in asymptomatic P. falciparum carriers allowing early detection and treatment of infectious reservoirs, as well as the in vivo analysis of factors that modulate sexual conversion.

Malaria gametocytes are sexual-stage parasites transmitted from mammalian host’s blood back to their insect vector. Here, Prajapati et al. identify gametocyte-committed ring-stage biomarkers allowing to forecast malaria transmission potential.

Comparative analysis of asexual and sexual stage Plasmodium falciparum development in different red blood cell types

BACKGROUND

Red blood cell (RBC) polymorphisms are suggested to influence the course of Plasmodium falciparum malaria. Whereas some variants have been found to be protective, others have been found to enhance parasite development. This study evaluated the effect of variant haemoglobin (Hb) and ABO blood groups on P. falciparum merozoite invasion, multiplication rates as well as gametocyte development.

METHODS

Approximately 2.5 mL of venous blood was collected from each participant. Flow cytometry was used to determine the in vitro merozoite invasion rates of NF54 parasites into the blood of 66 non-parasitaemic individuals with variant Hb genotypes (HbSS, HbSC) and blood groups (A, B, O), which were then compared with invasion into HbAA blood. The ex vivo asexual parasite multiplication and gametocyte production rates of parasites from 79 uncomplicated malaria patients with varying Hb genotypes (HbAS, HbAC and HbAA) were also estimated using microscopy.

RESULTS

Merozoite invasion rates were significantly reduced by about 50% in RBCs containing HbSS and HbSC relative to HbAA cells. The presence of blood group O and B reduced the invasion rates of HbSS by about 50% and 60%, respectively, relative to HbSC but the presence of blood group A removed the inhibitory effect of HbSS. The initial parasite densities in uncomplicated malaria patients with Hb genotypes HbAS and HbAC cells were similar but significantly lower than those with genotype HbAA. The ex vivo parasite multiplication rate, gametocytaemia and gametocyte conversion rates followed a similar trend but did not reach statistical significance (p > 0.05).

CONCLUSIONS

Parasite invasion rate into erythrocytes is dependent on both erythrocyte blood group antigen and haemoglobin genotype as blood group O and B provided protection via reduced merozoite invasion in RBCs containing HbSS relative to HbSC. Regardless of haemoglobin type, greater than 70% malaria patients had circulating ring stage parasites that differentiated into stage II gametocytes in 4 days.

Colorectal cancer in a multi-ethnic urban group: its anatomical and age profile

PURPOSE

To determine the age of presentation and anatomical distribution of colorectal cancer in an urban multi-ethnic group.

PATIENTS AND METHODS

Patients with colorectal adenocarcinoma from 1976-1995 in the tumor registry file of a major hospital in New York City's borough of Manhattan were identified. The charts of 688 patients were reviewed and the location of the cancer, ethnicity, and age at diagnosis were recorded. The tumors were classified as: right cancers (RC); from the cecum, to and including the hepatic flexure, transverse (Trans); left cancers (LC): from the splenic flexure down to and including the sigmoid colon, rectum (Rec); rectosigmoid and rectal lesions; and colorectal lesions without known locations (CA). Patients were classified from self identification, place of birth, or race as: Asians (AS); blacks (BL); Hispanics (HI); and white (WH). An ANOVA test, and a Schefee post hoc test were used to compare the mean ages. While a chi2 and a fully saturated log-linear model compared the proportions.

RESULTS

We could not identify the ethnicity of three patients, and they were not included in the analysis. There were 295 women and 390 men, with a mean age of 66.6 years and 65.0 years, respectively. The overall mean age was 65.7 years. The ethnicity of the patients were: AS = 102, BL = 98, HI = 189, and WH = 296. The mean ages for the different groups were: AS = 59.9 years, BL = 63.5 years, HI = 60.4 years, and WH = 71.7 years. The age difference was significant (P < 0.05), when comparing WH versus each other group. The regional distribution of the individual groups was: AS, RC = 28, Trans = 3, LC = 31, Rec = 37, CA = 3; BL, RC = 40, Trans = 2, LC = 33, Rec = 22, CA = 1; HI, RC = 45, Trans = 3, LC = 71, Rec = 61, CA = 9; and WH, RC = 76, Trans = 19, LC = 95, Rec = 89, CA = 17. The interethnical regional distribution of the cancers was significantly different (P < 0.05). Blacks had a greater presentation of right-sided lesions than expected, and whites had less Rec and RC lesions than expected.

CONCLUSIONS

Minority Americans presented with colorectal cancer at a significantly earlier age than WH Americans. Blacks had a high frequency of proximal lesions, and Caucasian Americans had low presentation of RC and Rec lesions. These findings may prove helpful in deciding when to begin screening for colorectal cancer among the different ethnic groups, and what modalities to apply given the differences in anatomical distribution of this cancer.