Preparation of biologically active single-chain variable antibody fragments that target the HIV-1 gp120 V3 loop

KD-247 is a humanized monoclonal antibody that targets the third hypervariable (V3) loop of gp120. It can efficiently neutralize a broad panel of clade B, but not non-clade B, HIV-1 isolates. To overcome this limitation, we are seeking to prepare genetically-engineered single-chain variable fragments (scFvs) of KD-247 that will have broader neutralizing activity against both clade B and non-clade B HIV-1 isolates. Initial attempts of optimizing the expression of KD-247 scFv have resulted in the formation of insoluble protein. Therefore, we have established purification protocols to recover, purify, and refold the KD-247 scFv from inclusion bodies. The protocol involved step-wise refolding of denatured scFv by dilution, dialysis, and on-column nickel-affinity purification. Monomeric scFv was further purified by size-exclusion chromatography. Using far UV circular dichroism (CD) spectroscopy we confirmed the expected beta-sheet profile of the refolded KD-247 scFv. Importantly, the refolded KD-247 scFv showed neutralizing activity against replication-competent HIV-1 BaL and JR-FL Env pseudotyped HIV-1, at potency comparable to that of the native full-size KD-247 antibody. Ongoing studies focus on the application of this system in generating KD-247 scFv variants with the ability to neutralize clade B and non-clade B HIV-1 isolates.

Ultrastructural study of the male gamete of Glossobothrium sp. (Cestoda: Bothriocephalidea: Triaenophoridae) a parasite of Schedophilus velaini (Perciformes: Centrolophidae) in Senegal

This paper describes the ultrastructure of the male gamete of Glossobothrium sp. (Bothriocephalidea: Triaenophoridae). The mature spermatozoon of Glossobothrium sp. is filiform and possesses two axonemes, a single helicoidal crested body, a parallel nucleus, parallel cortical microtubules and granules of glycogen. In Glossobothrium sp. we describe for first time a 200-250 nm thick crest-like body in the Bothriocephalidean. The anterior part of the spermatozoon exhibits a ring of 27 electron-dense cortical microtubules encircling the first axoneme. This structure persists until the appearance of the second axoneme. When the ring of electron-dense cortical microtubules disappears, the spermatozoon exhibits two bundles of thin cortical microtubules. The posterior part of the spermatozoon contains the posterior extremity of the second axoneme, the posterior extremity of the nucleus and few cortical microtubules. Soon nucleus disappears and the axoneme is disorganized. Thus the posterior extremity of the spermatozoon of Glossobothrium sp. exhibits only singlets produced by the disorganization of the doublets of the second axoneme and few cortical microtubules. This type of posterior extremity of the mature spermatozoon has never been described previously in the Triaenophoridae.

Ultrastructural study of spermiogenesis and the spermatozoon of Acanthocephaloides incrassatus (Molin, 1858) (Acanthocephala, Paleacanthocephala, Arhythmacanthidae) from Anguilla anguilla (Pisces, Teleostei) in Urbino ponds (Corsica Island)

This study deals with first ultrastructure features of Acanthocephaloides incrassatus (Paleacanthocephala, Arhythmacanthidae), a parasite of the fish Anguilla anguilla, reported for the first time in a Mediterranean pond. The spermiogenesis of A. incrassatus shows original specificities which have never been pointed out to this day in ultrastructural studies on spermiogenesis: the centriolar derivative is divided into two parts of different densities: an electron-dense, and the other, electron-lucent; a ring form has been observed on each side of the axoneme; a centriole with one central element. After the elaboration of a flagellum of 9+2 pattern, the centriole migrates in a nuclear groove. Rapidly, the centriole disappears. Then, the flagellum migration occurs by a series of processes and gives rise to a spermatozoon. The spermatozoon of A. incrassatus presents its own specificities: it exhibits an evolution of the centriolar derivative characterized by only nine peripheral elements deprived of a central element in the anterior part, then nine peripheral and one central element, and finally, nine peripheral elements with two central elements. An assumption is emitted on a probable correspondence of the evolution of the derivative centriolar during the spermiogenesis and the evolution that occurs in the spermatozoon. Protein granules also show different sizes and forms, full or emptied of their contents compared with data on other Acanthocephala.

Ultrastructure of the spermatozoon of Bothriocotyle sp. (Cestoda: Bothriocephalidea), a parasite of Schedophilus velaini (Sauvage, 1879) (Perciformes: Centrolophidae) in Senegal

The mature spermatozoon of Bothriocotyle sp. is filiform and tapered at both extremities. It possesses 2 axonemes of unequal length, showing the 9 + "1" pattern of Trepaxonemata. The anterior extremity exhibits a crest-like body. Thereafter, the crest-like body disappears, and the first axoneme is surrounded by a ring of cortical microtubules (about 27 units) that persist until the appearance of the second axoneme. This ring of cortical microtubules is characteristic only for species of Bothriocephalidea and represents a very useful phylogenetic character. The spermatozoon cytoplasm is slightly electron-dense and contains numerous electron-dense granules of glycogen in several regions. The anterior and posterior extremities of the spermatozoon lack cortical microtubules. The posterior extremity of the spermatozoon of Bothriocotyle sp. possesses a nucleus and a disorganized axoneme, which also characterizes spermatozoa of the Echinophallidae studied to date.

Topography and ultrastructure of the tegument of Lecithochirium musculus (Digenea: Hemiuridae), a parasite of the European eel Anguilla anguilla (Osteichthyes: Anguillidae)

The tegumental ultrastructure of the stomach fluke Lecithochirium musculus was studied using scanning and transmission electron microscopy. The surface of the tegument was smooth and covered by transverse cytoplasmic ridges. Cobblestone-like units of the tegument were observed on the ventral surface. Invagination and evagination of the ecsoma induced variations in the tegumental surface. The ultrastructural study revealed that the tegument of L. musculus had a typical syncytial organization with a distal cytoplasm lying over a basal matrix and cytons. Two types of intra-tegumental sensory structures were observed. Type 1 sensory receptor was a domed-like fusiform structure consisting of a smooth elevation of the tegument. Four receptors of this type were observed on the anterior dorsal surface of the fluke. Three nerve bulbs filled with electron-lucent material and mitochondria composed this receptor. Hemispherical electron-dense collars were observed at the top of the nerve bulbs. Striated rootlets laid just beneath the hemispherical electron-dense collars. Type 2 sensory receptor presented two morphological variations, i.e., a bulb-like monolobed structure, and a bulb-like bilobed structure observed at two different degrees of evagination. For both variations, the nerve bulb enclosed mitochondria, electron-lucent material, and a conical electron-dense collar from which extended a striated rootlet. Numerous sensory receptors of this type were observed around the ventral sucker.

Spermatozoon ultrastructure of Gyliauchen sp. (Digenea: Gyliauchenidae), an intestinal parasite of Siganus fuscescens (Pisces: Teleostei)

The ultrastructure of the mature spermatozoon of Gyliauchen sp., a parasite of the dusky rabbitfish Siganus fuscescens, was studied by transmission electron microscopy. The spermatozoon possesses two axonemes of the 9+"1" pattern of Trepaxonemata, four attachment zones, one mitochondrion, a nucleus, cortical microtubules, external ornamentation of the plasma membrane, and spine-like bodies. The main characteristics of this spermatozoon are the presence of one mitochondrion, spine-like bodies not associated with the external ornamentation, and a posterior extremity of type 3 that is characterized by the following sequence: posterior extremity of the nucleus then posterior extremity of the second axoneme. Numerous other ultrastructural features are also discussed and compared to the digenean spermatology literature. This is the first study of a member of the Gyliauchenidae and the fourth within the Lepocreadioidea. The results show that many ultrastructural characters are variable within this superfamily and could be useful for phylogeny.

Sperm ultrastructure of Helicometra epinepheli (Platyhelminthes, Digenea, Opecoelidae), parasite of Epinephelus fasciatus (Pisces, Teleostei)

This paper describes the ultrastructure of the mature spermatozoon of the digenean Helicometra epinepheli. The ultrastructural elements observed are: two axonemes with a 9+"1" pattern of Trepaxonemata, four attachment zones, a nucleus, two mitochondria, external ornamentation of the plasma membrane, spine-like bodies and cortical microtubules. A particularity of this spermatozoon is the presence of an apical cone. However, the spermatozoon presents the general pattern of the Opecoelidae and thus differs from Helicometra fasciata (which appears as an exception in this family) by several ultrastructural features: the presence of external ornamentation and spine-like bodies and the arrangement of cortical microtubules around the first mitochondrion in the region of the ornamentation. Each ultrastructural feature is discussed and compared with the literature to highlight characters which could be useful for phylogeny.

The sugar ring conformation of 4'-ethynyl-2-fluoro-2'-deoxyadenosine and its recognition by the polymerase active site of HIV reverse transcriptase

4' Ethynyl-2-fluoro-2'-deoxyadenosine (EFdA) is the most potent inhibitor of HIV reverse transcriptase (RT). We have recently named EFdA a Translocation Defective RT Inhibitor (TDRTI) because after its incorporation in the nucleic acid it blocks DNA polymerization, primarily by preventing translocation of RT on the template/primer that has EFdA at the 3'-primer end (T/PEFdA). The sugar ring conformation of EFdA may also influence RT inhibition by a) affecting the binding of EFdA triphosphate (EFdATP) at the RT active site and/or b) by preventing proper positioning of the 3'-OH of EFdA in T/PEFdA that is required for efficient DNA synthesis. Specifically, the North (C2'-exo/C3'-endo), but not the South (C2'-endo/C3'-exo) nucleotide sugar ring conformation is required for efficient binding at the primer-binding and polymerase active sites of RT. In this study we use nuclear magnetic resonance (NMR) spectroscopy experiments to determine the sugar ring conformation of EFdA. We find that unlike adenosine nucleosides unsubstituted at the 4'-position, the sugar ring of EFdA is primarily in the North conformation. This difference in sugar ring puckering likely contributes to the more efficient incorporation of EFdATP by RT than dATP. In addition, it suggests that the 3'-OH of EFdA in T/PEFdA is not likely to prevent incorporation of additional nucleotides and thus it does not contribute to the mechanism of RT inhibition. This study provides the first insights into how structural attributes of EFdA affect its antiviral potency through interactions with its RT target.

Topography and ultrastructure of the tegument of Bucephalus anguillae (Digenea: Bucephalidae), a parasite of the European eel Anguilla anguilla (Osteichthyen: Anguillidae)

The tegumental ultrastructure of the intestinal fluke Bucephalus anguillae was studied with the use of scanning and transmission electron microscopy. The surface of the tegument is covered by transverse ridges from which protrude numerous closely packed, digitated, and claw-shaped spines. Cobblestone-like units of the tegument were observed on the crescent-shaped formation of the rhynchus and at the posterior part of the body. Three types of sensory structures were examined, i.e., 2 uniciliated receptors and 1 without cilia. As anterior-posterior differences were observed, particular attention was given to spines and sensory receptors. Spine insertion zones and average cilia length are variable between anterior and posterior tegument areas. Ultrastructural study revealed that the tegument of B. anguillae has a typical syncytial organization with a distal cytoplasm lying over a basal matrix and cytons below. Cytoplasmic bridges allowed transit of secretory vesicles and granules. Diagrams of spines and sensory receptors were made to help in understanding the nature of these structures.

Comparison of arsenic and antimony contents in tissues and organs of brown trout caught from the river Presa polluted by ancient mining practices and from the river Bravona in Corsica (France): a survey study

The present study evaluates the concentrations of arsenic (As) and antimony (Sb) in the intestine, liver, muscle, gonads, gills, and kidney of Salmo trutta subsp. from the Presa River in Corsica (France; n = 10), which crosses an abandoned arsenic mine, and from the Bravona River (reference site; n = 10). Both metalloids were analyzed by means of ICP-MS. The relationships between fish size (length and weight) and metalloid concentrations in their tissues were investigated by linear regression analysis. In all fish samples concentrations of As and Sb (expressed as micrograms per gram fresh weight) were highest in the kidney. Lowest Sb concentrations were found in the muscle, whereas lowest As concentrations were found in the gonads of S. trutta. Two organotropisms were revealed: one for As-kidney (21.4656) > intestine (3.9535) > gills (3.0404) > liver (1.1743) > muscle (0.9976) > gonads (0.8081); and the other for Sb-kidney (0.70067) > gills (0.6181) > intestine (0.2576) > gonads (0.1673) > liver (0.9625) > muscle (0.0753). Results of linear regression analysis in most cases showed a significant negative correlation between metalloid concentration and fish size. Highly significant (p < 0.05) negative correlations were found between fish length and As concentration in the gonads, as well as between fish length and Sb concentrations in the gills. Arsenic concentrations in female fish were significantly higher than those in males in the kidney, gonads, gills, and liver. The same results were found for Sb, except in the liver, where the tendency was reversed.

Sperm ultrastructure of the digenean Siphoderina elongata (Platyhelminthes, Cryptogonimidae) intestinal parasite of Nemipterus furcosus (Pisces, Teleostei)

The ultrastructure of the spermatozoon of Siphoderina elongata was studied by transmission electron microscopy. A description and drawings of the mature spermatozoon are presented in this paper. Several ultrastructural elements of this male gamete have been observed: a nucleus, two mitochondria, two axonemes of 9 + "1" pattern, external ornamentation of the plasma membrane, spine-like bodies and cortical microtubules. The presence, the location or the number of these elements have been compared with other digenean spermatozoa. Moreover, a close attention was paid to the organization of the external ornamentation region. This zone presents a single row of cortical microtubules disposed in a semi-circle around a mitochondrion and associated with external ornamentation and spine-like bodies. The aim of this study is to highlight criteria which can be interesting in Platyhelminthes phylogeny.