Biosafety Concerns Involving Genetically Modified Mosquitoes to Combat Malaria and Dengue in Developing Countries

Malaria and dengue are the most prevalent mosquito-borne infections worldwide. Because traditional vector control methods have proven to be insufficient to control mosquito populations in endemic areas, scientists are actively working in the design of new strategies, such as genetically modified (GM) mosquitoes, to reduce disease transmission. The replacement of natural populations with GM mosquitoes is becoming a tangible possibility, however, many fear that the release of these organisms into the environment could constitute a significant risk to biodiversity and may cause the unintended spread of GM organisms across national borders. The Cartagena Protocol on Biosafety, an international agreement originally intended to oversee the trade of GM crops, did not include specific provisions for the safe use of GM insects. Recently, the Ad Hoc Technical Expert Group (AHTEG) on Risk Assessment and Risk Management to the Conference of the Parties, provided guidelines on the use of GM arthropods for the control of human disease. However, these guidelines did not address some significant technical and safety issues associated with the use of genetically or biologically modified vectors. A new global treaty, specifically intended to address issues related to genetic or biological modifications of arthropod vectors seem to be necessary before we endorse the decision of releasing modified arthropod vectors into the natural environment

Altered membrane structure and surface potential in homozygous hemoglobin C erythrocytes.

BACKGROUND:Hemoglobin C differs from normal hemoglobin A by a glutamate-to-lysine substitution at position 6 of beta globin and is oxidatively unstable. Compared to homozygous AA erythrocytes, homozygous CC erythrocytes contain higher levels of membrane-associated hemichromes and more extensively clustered band 3 proteins. These findings suggest that CC erythrocytes have a different membrane matrix than AA erythrocytes. METHODOLOGY AND FINDINGS:We found that AA and CC erythrocytes differ in their membrane lipid composition, and that a subset of CC erythrocytes expresses increased levels of externalized phosphatidylserine. Detergent membrane analyses for raft marker proteins indicated that CC erythrocyte membranes are more resistant to detergent solubilization. These data suggest that membrane raft organization is modified in CC erythrocytes. In addition, the average zeta potential (a measure of surface electrochemical potential) of CC erythrocytes was approximately 2 mV lower than that of AA erythrocytes, indicating that substantial rearrangements occur in the membrane matrix of CC erythrocytes. We were able to recapitulate this low zeta potential phenotype in AA erythrocytes by treating them with NaNO(2) to oxidize hemoglobin A molecules and increase levels of membrane-associated hemichromes. CONCLUSION:Our data support the possibility that increased hemichrome deposition and altered lipid composition induce molecular rearrangements in CC erythrocyte membranes, resulting in a unique membrane structure

Plasmodium falciparum: nitric oxide modulates heme speciation in isolated food vacuoles.

Nitric oxide (NO) and NO-derived reactive nitrogen species (RNS) are present in the food vacuole (FV) of Plasmodium falciparum trophozoites. The product of PFL1555w, a putative cytochrome b(5), localizes in the FV membrane, similar to what was previously observed for the product of PF13_0353, a putative cytochrome b(5) reductase. These two gene products may contribute to NO generation by denitrification chemistry from nitrate and/or nitrite present in the erythrocyte cytosol. The possible coordination of NO to heme species present in the food vacuole was probed by resonance Raman spectroscopy. The spectroscopic data revealed that in situ generated NO interacts with heme inside the intact FVs to form ferrous heme nitrosyl complexes that influence intra-vacuolar heme solubility. The formation of heme nitrosyl complexes within the FV is a previously unrecognized factor that could affect the equilibrium between soluble and crystallized heme within the FV in vivo

Zeta potential (ZP) analyses.

<p>(A) Diagram of ZP principle. ZP is defined as the electrochemical potential at the shear plane. Outside the shear plane, ions are not closely associated with the internal ion cloud. (B) ZP measurements from AA and CC erythrocyte populations. Peak values were estimated by Gaussian fitting the histogram. (C) Levels of membrane-associated hemichromes (mean±SD) in control and NaNO₂-treated AA erythrocytes. For reference, native CC erythrocytes show 1.8-fold greater hemichrome levels than native AA erythrocytes <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0005828#pone.0005828-Fairhurst1" target="_blank">[31]</a>. (D) ZP measurements from control and NaNO₂-treated AA erythrocyte populations.</p

Detergent-resistant membrane analyses of AA and CC erythrocytes.

<p>Proteins from 18 fractions (out of a total of 36 fractions) were separated by SDS-PAGE under denaturing conditions, transferred to PVDF membrane, and probed with protein-specific monoclonal antibodies.</p

Analysis of membrane-associated IgG in AA and CC erythrocytes.

<p>Proteins from 9 fractions (out of a total of 36 fractions) were separated by SDS-PAGE under denaturing conditions, transferred to PVDF membrane, and probed with a monoclonal antibody specific for human IgG.</p