The fate and toxicity of Raman-active silica-gold nanoparticles in mice

Raman spectroscopy is an optical imaging method that is based on the Raman effect, the inelastic scattering of a photon when energy is absorbed from light by a surface. Although Raman spectroscopy is widely used for chemical and molecular analysis, its clinical application has been hindered by the inherently weak nature of the Raman effect. Raman-silica-gold-nanoparticles (R-Si-Au-NPs) overcome this limitation by producing larger Raman signals through surface-enhanced Raman scattering. Because we are developing these particles for use as targeted molecular imaging agents, we examined the acute toxicity and biodistribution of core polyethylene glycol (PEG)-ylated R-Si-Au-NPs after different routes of administration in mice. After intravenous administration, PEG-R-Si-Au-NPs were removed from the circulation by macrophages in the liver and spleen (that is, the reticuloendothelial system). At 24 hours, PEG-R-Si-Au-NPs elicited a mild inflammatory response and an increase in oxidative stress in the liver, which subsided by 2 weeks after administration. No evidence of significant toxicity was observed by measuring clinical, histological, biochemical, or cardiovascular parameters for 2 weeks. Because we are designing targeted PEG-R-Si-Au-NPs (for example, PEG-R-Si-Au-NPs labeled with an affibody that binds specifically to the epidermal growth factor receptor) to detect colorectal cancer after administration into the bowel lumen, we tested the toxicity of the core nanoparticle after administration per rectum. We observed no significant bowel or systemic toxicity, and no PEG-R-Si-Au-NPs were detected systemically. Although additional studies are required to investigate the long-term effects of PEG-R-Si-Au-NPs and their toxicity when carrying the targeting moiety, the results presented here support the idea that PEG-R-Si-Au-NPs can be safely used in living subjects, especially when administered rectally.     

Ultrastructure of mixed plant virus infection: bean yellow mosaic virus with cowpea severe mosaic virus or cowpea mosaic virus in bean

Ultrastructural responses of bean leaf cells simultaneously infected with two morphologically distinct RNA viruses, cowpea mosaic virus (CPMV) and bean yellow mosaic virus (BYMV), or cowpea severe mosaic virus (CSMV) and BYMV, were studied in situ. The major effects on cells infected with two viruses included: (1) association of virus group-specific cytoplasmic inclusions characteristic of each virus; (2) close association of virions into specifically arranged aggregates in which CPMV or CSMV icosahedra were aligned along the long axes of the BYMV rods; and (3) the induced formation of intranuclear inclusions, spheres (22-26 nm in diameter) and filaments (10-14 nm wide and of variable length) in mixed infections of CSMV and BYMV. Intracellular serological testing using ferritin conjugated with CSMV antibodies revealed no relationship between the spherical intranuclear inclusions and CSMV capsids. We conclude that the ultrastructure of mixed infections could be used as another tool for identifying related plant viruses.     

Single and repeated dose toxicity of mesoporous hollow silica nanoparticles in intravenously exposed mice

Mesoporous hollow silica nanoparticles (MHSNs) are emerging as one of the new and promising nanomaterials for biomedical applications, but the biocompatibility of MHSNs in vivo has received little attention. In the present study, the systematic single and repeated dose toxicity, biodistribution and clearance of MHSNs in vivo were demonstrated after intravenous injection in mice. For single dose toxicity, lethal dose 50 (LD(50)) of 110?nm MHSNs was higher than 1000?mg/kg. Further repeated dose toxicity studies indicated no death was observed when mice were exposed to MHSNs at 20, 40 and 80?mg/kg by continuous intravenous administration for 14 days. These results suggest low toxicity of MHSNs when intravenous injection at single dose or repeated administrations. ICP-OES and TEM results show that the MHSNs mainly accumulate in mononuclear phagocytic cells in liver and spleen. In addition, these particles could be excreted from the body and the entire clearance time of the particles should be over 4 weeks. These findings would be useful for future development of nanotechnology-based drug delivery system and other biomedical applications.     

Biodistribution of filamentous phage-Fab in nude mice.

In vivo panning of peptide libraries in mice has allowed the isolation of peptides which target the vasculature of specific organs. The application of this approach to phage displaying Fab fragments (phage-Fab) could lead to the isolation of antibodies which recognize novel tumor antigens. In this study, we have evaluated the biodistribution of phage-Fab in nude mice. Balb/c nude mice were injected intravenously with 10(9) TU of phage displaying the anti-colon cancer Fab c30.6. Blood samples were collected at nine time points over a period of 72 h and three groups of four mice were sacrificed at 4 min, 24 h and 72 h. Normal tissues (liver, colon, spleen, kidneys, lungs, skeletal muscle) and faeces were collected at these time points and the number of viable phage in each sample was determined. The distribution of phage in tissues was also examined by immunohistochemical analysis of paraffin-embedded tissues. Regression analysis of plasma kinetic data showed that the half-life and the volume of distribution of phage was 3.6 h and 1 ml, respectively. Phage uptake occurred predominantly in lungs, kidneys, spleen and liver. Relatively few phage were distributed to colon and muscle, and phage were eliminated from the circulation by 72 h. Immunohistochemical analysis showed phage to be mainly within the vasculature at 4 min, whereas notable phage extravasation was observed at 24 h and 72 h. In conclusion, this study provides information on the in vivo behavior of phage-Fab which will be useful in the design of in vivo panning strategies. By choosing appropriate time points for tissue collection, it may be possible to isolate novel Fabs against both intra- and extravascular targets.     

Alternate hosts of African cassava mosaic virus and East African cassava mosaic Cameroon virus in Nigeria

Cassava mosaic disease (CMD) caused by African cassava mosaic virus (ACMV) and East African cassava mosaic Cameroon virus (EACMCV) is the major constraint to cassava production in Nigeria. Sequences of the DNA-A component of ACMV and EACMCV isolates from leguminous plant species (Senna occidentalis, Leucana leucocephala and Glycine max), castor oil plant (Ricinus communis), a weed host (Combretum confertum) and a wild species of cassava (Manihot glaziovii) were determined. All ACMV isolates from these hosts showed 96-98% nucleotide sequence identity with cassava isolates from West Africa. EACMCV was found only in four hosts (S. occidentalis, L. leucocephala, C. confertum, M. glaziovii), and sequences of these isolates showed 96-99% identity with cassava isolates from West Africa. These results provide definitive evidence for the natural occurrence of ACMV and EACMCV in plant species besides cassava.     

Potato yellow mosaic virus: a synonym of Tomato yellow mosaic virus

Summary.  Tomato yellow mosaic was first described in 1963, as a disease caused by a geminivirus transmitted by the whitefly Bemisia tabaci in Venezuela. In 1981 and 1985, Tomato yellow mosaic virus (ToYMV) was reported to occasionally infect potato plants growing in the proximity of tomato plantings affected by this virus. Despite these previous reports, a virus isolated from yellow mosaic-affected potato plants in Venezuela, was described in 1986 as a “new geminivirus” called potato yellow mosaic virus (PYMV). In recent years, different geminiviruses related to PYMV have been described from tomato fields in Venezuela and other countries in the Caribbean Basin, including Panama. Comparative nucleotide and amino acid sequence analyses of a 1698 bp fragment amplified from the common region and part of the AV1 and AC1 ORFs of ToYMV from Venezuela, yielded 95.7% sequence identity with the corresponding regions of PYMV. Nucleotide and amino acid sequence identities between ToYMV and PYMV, were 96.3% and 95.1% for AC1, and 95.7% and 100% for AV1, respectively. The identity of the nucleotide sequence for the common region of ToYMV and PYMV was 96.5%. Comparative sequence analyses conducted with ToYMV and other tomato begomoviruses present in the Caribbean region, showed only distant relationships. It is concluded here that PYMV is a synonym of ToYMV. Received February 2, 2001 Accepted February 28, 2001     

Immunomodulatory effect of gelatin-coated silver nanoparticles in mice: Ultrastructural evaluation

Silver nanoparticles (SNP) are used in many pharmaceutical, cosmetic, and industrial products already available in the market. Although they are considered relatively safe, many toxic and pathological alterations in different organs including immune organs were reported after SNP administration. In this study, 10-week-old male mice (n = 20) were divided into two groups. Ten mice received greenly synthesized gelatin-coated silver nanoparticles in a dose of 10 mg/kg body weight for five consecutive days while the other 10 received 0.5 ml of distilled water daily for 5 days and kept as control. At the sixth day, all mice were sacrificed; blood and tissue samples were collected and prepared for pathological analysis. Liver and kidney lesions were in the form of degenerative and inflammatory changes. Interestingly, the immune organs were drastically affected by SNP treatment. Severe hyperplasia of the Peyer’s patches was noticed in the intestines of intoxicated animals both in gross and microscopic examination. Spleen was enlarged and showed large number of megakaryocytes. The particles were encountered in membrane-bound phagosomes inside macrophages in different organs like lungs and spleen. Blood picture complied to morphological findings with an increase in monocytes and eosinophils accompanied by drop in the platelets count in the intoxicated animals.     

Hybrid brome mosaic virus RNAs express and are packaged in tobacco mosaic virus coat protein in vivo

Brome mosaic virus (BMV) is an icosahedral virus with a tripartite RNA genome which infects monocotyledonous plants, while the cowpea or legume strain of tobacco mosaic virus (CcTMV) is a rod-shaped virus with a single component RNA genome which infects dicotyledonous plants. To examine the potential for exchanging entire genes between RNA viruses, biologically active cDNA clones were used to replace the natural coat gene of BMV RNA3 with the coat gene and encapsidation origin of CcTMV. In protoplasts coinoculated with BMV RNAs 1 and 2, the resulting hybrid RNA3 was replicated by BMV trans-acting factors but was packaged in TMV coat protein to give rod-shaped particles rather than the usual BMV icosahedra. When the CcTMV encapsidation origin was suitably inserted in derivatives of BMV RNAs 1 and 2, these RNAs were also packaged in a ribonuclease-resistant form in protoplasts coinoculated with the hybrid RNA3 expressing TMV rather than BMV coat protein. Thus, despite the markedly divergent nature of BMV and TMV, replicating hybrids bearing characters derived from both parent viruses were produced. Such hybrid viruses could be of considerable value for studying specific steps in infection and for assigning functions to particular virus genes.     

Development and evaluation of a complementation-dependent gene delivery system based on cucumber mosaic virus

To engineer cucumber mosaic virus (CMV-Ix) into a gene vector, genome component RNA 3 of the virus was modified and split into two sub-components, RNA 3A and RNA 3B. In RNA 3A, the open reading frame of the movement protein (MP) was replaced by a reporter gene encoding the green fluorescent protein (GFP), to monitor virus replication and movement. In RNA 3B, the coat protein (CP) gene was eliminated and a multiple cloning site (MCS) was created for foreign gene insertion. Each sub-component alone is defective and relies on its companion sub-component to restore full RNA 3 function. The vector system was evaluated for its ability to deliver and express the bacterial beta-glucuronidase (GUS) gene and a modified bean yellow mosaic virus coat protein (BYMV-CP) gene in Nicotiana benthamiana plants. Results showed that the engineered virus was able to move from cell to cell in the inoculated leaf and enter the minor veins of the inoculated leaf. Foreign gene expression was detected in the inoculated leaves. However, intermolecular recombination between RNA 3A and 3B occurred frequently, preventing efficient systemic expression of the foreign gene(s). Modifications and further evaluations are being undertaken to improve the gene delivery system.     

Systemic trafficking of plant virus nanoparticles in mice via the oral route

The plant virus, cowpea mosaic virus (CPMV), is increasingly being used as a nanoparticle platform for multivalent display of peptides. A growing variety of applications have employed the CPMV display technology including vaccines, antiviral therapeutics, nanoblock chemistry, and materials science. CPMV chimeras can be inexpensively produced from experimentally infected cowpea plants and are completely stable at 37 degrees C and low pH, suggesting that they could be used as edible or mucosally-delivered vaccines or therapeutics. However, the fate of CPMV particles in vivo, or following delivery via the oral route, is unknown. To address this question, we examined CPMV in vitro and in vivo. CPMV was shown to be stable under simulated gastric conditions in vitro. The pattern of localization of CPMV particles to mouse tissues following oral or intravenous dosing was then determined. For several days following oral or intravenous inoculation, CPMV was found in a wide variety of tissues throughout the body, including the spleen, kidney, liver, lung, stomach, small intestine, lymph nodes, brain, and bone marrow. CPMV particles were detected after cardiac perfusion, suggesting that the particles entered the tissues. This pattern was confirmed using methods to specifically detect the viral capsid proteins and the internal viral RNA. The stability of CPMV virions in the gastrointestinal tract followed by their systemic dissemination supports their use as orally bioavailable nanoparticles.     

CO2 effects on local-lesion production by tobacco mosaic virus and turnip mosaic virus

Nicotiana tabacum var. Havana 425 and N. glutinosa plants were inoculated with tobacco mosaic virus (TMV) and those of N. tabacum var. Haranova with turnip mosaic virus (TuMV). After inoculation, plants were kept in normal air or in 1% CO₂, either continuously, only during the light period, or only during the dark period. When plants were exposed to 1% CO₂ during the light period, lesion production in all three hosts was greatly inhibited. In other CO₂ treatments the number of lesions produced was similar to the control (normal air). However, in plants of N. tabacum var. Havana 425 exposed to 1% CO₂, either during the dark period or continuously, lesions were yellow instead of the usual brown. In addition, lesions developed on leaves exposed to 1% CO₂ during dark or light periods were smaller than in the other two treatments. In the yellow lesions there was frequently a new type of particle aggregation, called zipper aggregates, indicating that variation in the environment can cause changes in the structure of the TMV aggregates.     

Characterization and genetic diversity of sugarcane streak mosaic virus causing mosaic in sugarcane

Sixty-three sugarcane leaf samples were collected from fifty-eight sugarcane varieties, evolved from eleven major sugarcane growing states in India, Australia, South Africa and USA. In RT-PCR, using gene specific primers for sugarcane streak mosaic virus (SCSMV)-CP, 58 of 63 sugarcane samples were found positive to the virus infection and rest of the five samples were negative. Partial CP gene sequences of 42 SCSMV isolates including an isolate from aphid colony (Melanaphis indosacchari) infested on sugarcane variety from this study were characterized after cloning and sequencing for selective isolates represented by at least one isolate from each location. The new sequences identified in the study were named as SCSMV-CB isolates. Fifty two sequences including the 10 database sequences (complete CP cds) deposited earlier from this institute were compared with each other as well as GenBank database sequences of Potyviridae members viz., Rymovirus, Potyvirus, Ipomovirus, Tritimovirus and eight sequences of SCSMV reported from elsewhere. Among the SCSMV-CB isolates sequenced in the study, 85.7–100% (nucleotide) and 89.9–100% (amino acid) sequence identities were observed and with the other data base sequences of SCSMV, the respective identities were 82.2–97.5 and 89.7–98.6%. Grouping of the isolates by the maximum likelihood with molecular clock model, distributed 60 SCSMV sequences including the eight database sequences deposited by other SCSMV working groups from India and USA in 16 different phylogenetic groups. Although the isolates of SCSMV were relatively close to Ipomovirus and Tritimovirus, they were sandwiched between Rymovirus and Ipomovirus. The sequence comparison and phylogenetic studies revealed that the relatedness of SCSMV with the potyviral related genera was comparatively low to consider it as a member of earlier described potyviral genera, hence the genus “Susmovirus” (sugarcane streak mosaic virus) has been proposed, with SCSMV as the sole species to be included. The 52 SCSMV-CB isolates from this institute were distributed in 14 phylogenetic groups and the grouping pattern revealed that the virus isolates could not be grouped based on geographical origin of the host varieties or longevity of the host variety.     

Crystallization of cauliflower mosaic virus

Cauliflower mosaic virus has been crystallized in hanging and sitting drops. The hexagonal and octahedrally shaped crystals are up to 0.5 mm in mean diameter. The octahedrally shaped crystals diffract to about 27 A resolution. The results are discussed in relation to the lability and aggregation of the virions.     

Biodistribution and pharmacokinetics of recombinant, human 125I-interleukin-2 in mice

The pharmacokinetics and biodistribution of radioiodinated recombinant interleukin-2 (125I-IL-2) was studied after either intravenous (i.v.) or intraperitoneal (i.p.) injection into C57BL/6 mice. Beta-lactoglobulin radiolabeled with 131I served as a control protein. After i.v. injection, 125I-IL-2 preferentially accumulated in the liver and spleen. Liver accumulation was fast, peaking at 5 min, and was followed by rapid clearance. Spleen accumulation was slightly slower, peaking at 15 min. Blood values 1 min after i.v. injection were 22-34% of the injected doses (I.D.)/gram. These values declined quickly over the next hour. In contrast, after i.p. administration no organ showed specific uptake of 125I-IL-2. Blood values after i.p. injection were essentially constant over 3 h and were greater and more sustained than after i.v. administration. Kidney values for both 125I-IL-2 and 131I-beta-lactoglobulin, after either i.v. or i.p. injection, indicated that the major route of clearance for both compounds was rapid loss through the kidneys.     

Phosphorylated proteins in cauliflower mosaic virus

Autoradiography of dodecyl sulfate-impregnated polyacrylamide gels after electrophoresis of the proteins from 32P-labeled cauliflower mosaic virus (CaMV) showed that two of the structural proteins were phosphorylated. These two proteins of 44 and 58 kilodaltons (kd) occur as minor components with some strains of the virus, but with other virus strains under particular conditions the 44-kd protein appears as a major component of the virion. The site of phosphorylation was found to be phosphoserine and phosphothreonine. It is suggested from these results that the 58-kd protein may be the primary translation product of the coat protein gene of CaMV and that the 44-kd and other lower molecular weight forms of the coat protein are derived from this polypeptide by proteolysis.     

Assembly of trans-encapsidated recombinant viral vectors engineered from Tobacco mosaic virus and Semliki Forest virus and their evaluation as immunogens

RNA virus vectors are attractive vaccine delivery agents capable of directing high-level gene expression without integration into host cell DNA. However, delivery of non-encapsidated RNA viral vectors into animal cells is relatively inefficient. By introducing the tobacco mosaic virus (TMV) origin of assembly into the RNA genome of Semliki Forest virus (SFV), we generated an SFV expression vector that could be efficiently packaged (trans-encapsidated) in vitro by purified TMV coat protein (CP). Using cellular assays, pseudovirus disassembly, RNA replication and reporter gene expression were demonstrated. We also evaluated the immune response to trans-encapsidated recombinant SFV carrying a model antigen gene (beta-galactosidase) in C57/B6 mice. Relative to RNA alone, vector encapsidation significantly improved the humoral and cellular immune responses. Furthermore, reassembly with recombinant TMV CPs permitted the display of peptide epitopes on the capsid surface as either genetic fusions or through chemical conjugation, to complement the immunoreactivity of the encapsidated RNA genetic payload. The SFV vector/TMV CP system described provides an alternative nucleic acid delivery mechanism that is safe, easy to manufacture in vitro and that also facilitates the generation of unique nucleic acid/protein antigen compositions.     

Crystallization of Brome mosaic virus and T = 1 Brome mosaic virus particles following a structural transition

Brome mosaic virus (BMV), a T = 3 icosahedral plant virus, can be dissociated into coat protein subunits and subunit oligomers at pH 7.5 in the presence of concentrated salts. We have found that during the course of this treatment the coat protein subunits are cleaved, presumably by plant cell proteases still present in the preparation, between amino acids 35 and 36. The truncated protein subunits will then reorganize into T = 1 icosahedral particles and can be crystallized from sodium malonate. Quasi elastic light scattering and atomic force microscopy results suggest that the transition from T = 3 to T = 1 particles can occur by separate pathways, dissociation into coat protein subunits and oligomers and reassembly into T = 1 particles, or direct condensation of the T = 3 virions to T = 1 particles with the shedding of hexameric capsomeres. The latter process has been directly visualized using atomic force microscopy. Native T = 3 virions have been crystallized in several different crystal forms, but neither a rhombohedral form nor either of two orthorhombic forms diffract beyond about 3.4 A. Tetragonal crystals of the T = 1 particles, however, diffract to at least 2.5 A resolution. Evidence suggests that the T = 1 particles are more structurally uniform and ordered than are native T = 3 virions. A variety of anomalous virus particles having diverse sizes have been visualized in preparations of BMV used for crystallization. In some cases these aberrant particles are incorporated into growing crystals where they are frequently responsible for defect formation.