Unveiling Cryptosporidium parvum sporozoite-derived extracellular vesicles: profiling, origin, and protein composition

Cryptosporidium parvum is a common cause of a zoonotic disease and a main cause of diarrhea in newborns. Effective drugs or vaccines are still lacking. Oocyst is the infective form of the parasite; after its ingestion, the oocyst excysts and releases four sporozoites into the host intestine that rapidly attack the enterocytes. The membrane protein CpRom1 is a large rhomboid protease that is expressed by sporozoites and recognized as antigen by the host immune system. In this study, we observed the release of CpRom1 with extracellular vesicles (EVs) that was not previously described. To investigate this phenomenon, we isolated and resolved EVs from the excystation medium by differential ultracentrifugation. Fluorescence flow cytometry and transmission electron microscopy (TEM) experiments identified two types of sporozoite-derived vesicles: large extracellular vesicles (LEVs) and small extracellular vesicles (SEVs). Nanoparticle tracking analysis (NTA) revealed mode diameter of 181 nm for LEVs and 105 nm for SEVs, respectively. Immunodetection experiments proved the presence of CpRom1 and the Golgi protein CpGRASP in LEVs, while immune-electron microscopy trials demonstrated the localization of CpRom1 on the LEVs surface. TEM and scanning electron microscopy (SEM) showed that LEVs were generated by means of the budding of the outer membrane of sporozoites; conversely, the origin of SEVs remained uncertain. Distinct protein compositions were observed between LEVs and SEVs as evidenced by their corresponding electrophoretic profiles. Indeed, a dedicated proteomic analysis identified 5 and 16 proteins unique for LEVs and SEVs, respectively. Overall, 60 proteins were identified in the proteome of both types of vesicles and most of these proteins (48 in number) were already identified in the molecular cargo of extracellular vesicles from other organisms. Noteworthy, we identified 12 proteins unique to Cryptosporidium spp. and this last group included the immunodominant parasite antigen glycoprotein GP60, which is one of the most abundant proteins in both LEVs and SEVs.

Isolation and Characterization of Mouse Monoclonal Antibodies That Neutralize SARS-CoV-2 and Its Variants of Concern Alpha, Beta, Gamma and Delta by Binding Conformational Epitopes of Glycosylated RBD With High Potency

Antibodies targeting Receptor Binding Domain (RBD) of SARS-CoV-2 have been suggested to account for the majority of neutralizing activity in COVID-19 convalescent sera and several neutralizing antibodies (nAbs) have been isolated, characterized and proposed as emergency therapeutics in the form of monoclonal antibodies (mAbs). However, SARS-CoV-2 variants are rapidly spreading worldwide from the sites of initial identification. The variants of concern (VOC) B.1.1.7 (Alpha), B.1.351 (Beta), P.1 (Gamma) and B.1.167.2 (Delta) showed mutations in the SARS-CoV-2 spike protein potentially able to cause escape from nAb responses with a consequent reduction of efficacy of vaccines and mAbs-based therapy. We produced the recombinant RBD (rRBD) of SARS-CoV-2 spike glycoprotein from the Wuhan-Hu 1 reference sequence in a mammalian system, for mice immunization to isolate new mAbs with neutralizing activity. Here we describe four mAbs that were able to bind the rRBD in Enzyme-Linked Immunosorbent Assay and the transmembrane full-length spike protein expressed in HEK293T cells by flow cytometry assay. Moreover, the mAbs recognized the RBD in supernatants of SARS-CoV-2 infected VERO E6 cells by Western Blot under non-reducing condition or in supernatants of cells infected with lentivirus pseudotyped for spike protein, by immunoprecipitation assay. Three out of four mAbs lost their binding efficiency to completely N-deglycosylated rRBD and none was able to bind the same recombinant protein expressed in Escherichia coli, suggesting that the epitopes recognized by three mAbs are generated by the conformational structure of the glycosylated native protein. Of particular relevance, three mAbs were able to inhibit Wuhan SARS-CoV-2 infection of VERO E6 cells in a plaque-reduction neutralization test and the Wuhan SARS-CoV-2 as well as the Alpha, Beta, Gamma and Delta VOC in a pseudoviruses-based neutralization test. These mAbs represent important additional tools for diagnosis and therapy of COVID-19 and may contribute to the understanding of the functional structure of SARS-CoV-2 RBD.

Prevalence and genetic characterization of Dientamoeba fragilis in asymptomatic children attending daycare centers

In order to provide additional data on the prevalence and genetic diversity of Dientamoeba fragilis in human populations, we conducted a study in children from low-income communities in Sao Paulo State, Brazil. Fecal samples from daycare center attendees up to 6 years old (n=156) and staff members (n=18) were submitted to PCR and sequencing of D. fragilis as well as to microscopic examination for the presence of other intestinal parasites. All children assessed were asymptomatic and 10.3% (16/156) were positive for D. fragilis. No worker was found to be positive. An association between Dientamoeba and coinfection with other intestinal parasites was observed. Concerning the genetic diversity, 14 and only two isolates were genotype 1 and genotype 2, respectively. Our findings outline interesting aspects: (1) asymptomatic children as carriers of Dientamoeba in communities in which environmental conditions ensure parasite transmission and, (2) association between Dientamoeba infection in young children and coinfection with other enteric parasites, reinforcing its transmission via the fecal-oral route.

Delivery of SA35 and SA40 peptides in mice enhances humoral and cellular immune responses and confers protection against Cryptosporidium parvum infection

BACKGROUND

Cryptosporidium parvum is a major cause of diarrhea in children and ruminants at the earliest stages of life. Maternal antibodies represent the main shield of neonate mammals for most of the infections. Two recombinant antigens (SA35 and SA40), portions of two C. parvum proteins, were tested for their ability to induce immune responses in adult mice and for protection on neonate BALB/c mice born from females immunised by mucosal delivery of both peptides.

METHODS

Adult BALB/c mice were intraperitoneally immunised with SA35 and SA40, separately or mixed, and their immune response was characterised. Furthermore, BALB/c pregnant mice were immunised by mucosal delivery with an SA35/40 mix, before and during pregnancy. Soon after birth, their offspring were infected with two doses (1 × 105 and 5 × 103) of C. parvum oocysts and the parasitic burden was determined at 5 and 9 days post-infection.

RESULTS

Intraperitoneal immunisation with SA35 and SA40 induced specific IgG and IgG1 in serum, specific IgA in the intestinal mucosa, increase of CD3+/CD4+ and CD30+ cells in splenocytes, which produced IFN-γ. Neonates born from immunised mice and infected with 1 × 105 oocysts showed a significant reduction of oocysts and intestinal forms (23 and 42%, respectively). A reduction of all parasitic forms (96%; P < 0.05) was observed when neonates were infected with 5 × 103 oocysts.

CONCLUSIONS

SA35 and SA40 peptides induce specific humoral and cell-mediated immune responses to C. parvum in adult mice. Moreover, mucosal administration of the SA35/40 mix in pregnant mice reduces C. parvum burden in their litters.

Myiasis of the Tracheostomy Wound Caused by Sarcophaga (Liopygia) argyrostoma (Diptera: Sarcophagidae): Molecular Identification Based on the Mitochondrial Cytochrome c Oxidase I Gene

Wound myiasis is the infestation of open wounds of mammalian hosts caused by larvae of various species of flies. This kind of myiasis can be a serious problem for immobilized patients with open wounds. Here, we identify a dipteran larva found in the tracheostomy wound of a child affected by a severe spinal muscular atrophy. The collected larva was dissected and microscopically analyzed. DNA was extracted from part of the larva and used for the molecular identification. A 487 bp fragment, including part of 5.8 S, the internal transcribed spacer 2 (ITS2), and part of 28S, was amplified using a novel PCR assay to be cloned and sequenced. The barcode region of cytochrome oxidase I (COI) was also cloned and sequenced after PCR amplification. The larva, designated as SASI1, was identified as a third instar of Sarcophaga sp. The COI sequencing confirmed a low similarity with Sarcophaga ruficornis (F.) (95%), yet COI showed a 100% similarity with Sarcophaga argyrostoma (Robineau-Desvoidy, 1830) species. Therefore, SASI1 was identified as a S. argyrostoma larva on the basis of its COI barcode. This is one of the rare cases of myiasis of tracheostomy wound and the first caused by S. argyrostoma.

A real-time assemblage-specific PCR assay for the detection of Giardia duodenalis assemblages A, B and E in fecal samples

Giardiosis is a common gastrointestinal infection caused by the flagellate Giardia duodenalis, and affects both humans and animals, worldwide. Animals are infected with both zoonotic and host-specific G. duodenalis assemblages, and their role in the transmission of the infection to humans has been a subject of intense research and debate. Conventional PCR assays are appropriate to determine G. duodenalis assemblages, but lack sensitivity for the detection of mixed infections. Previous surveys demonstrated the occurrence of mixed infections with G. duodenalis assemblage A and B in humans, and with assemblages A and E in cattle, but are likely to be underestimated. In this study, we designed a set of assemblage-specific primers by exploiting sequence variability in homologous genes from assemblages A, B and E. Primers were designed to amplify fragments of different size that generated different melting curves from each assemblage in real-time PCR (rt-PCR) experiments. The assay has been tested on a large panel of human and farm animal isolates, and shown to possess high specificity (no cross reactions observed) and sensitivity (detection limit close to 20 copies). Therefore, this assay can be useful to detect zoonotic and host-specific G. duodenalis assemblages in fecal samples from farm animals, particularly when a large number of samples is to be tested.

Molecular characterization of intestinal protozoa in two poor communities in the State of São Paulo, Brazil

Background

Several species of protozoa cause acute or chronic gastroenteritis in humans, worldwide. The burden of disease is particularly high among children living in developing areas of the world, where transmission is favored by lower hygienic standards and scarce availability of safe water. However, asymptomatic infection and polyparasitism are also commonly observed in poor settings. Here, we investigated the prevalence of intestinal protozoa in two small fishing villages, Porto Said (PS) and Santa Maria da Serra (SM), situated along the river Tietê in the State of São Paolo, Brazil. The villages lack basic public infrastructure and services, such as roads, public water supply, electricity and public health services.

Methods

Multiple fecal samples were collected from 88 individuals in PS and from 38 individuals in SM, who were asymptomatic at the time of sampling and had no recent history of diarrheal disease. To gain insights into potential transmission routes, 49 dog fecal samples (38 from PS and 11 from SM) and 28 river water samples were also collected. All samples were tested by microscopy and PCR was used to genotype Giardia duodenalis, Blastocystis sp., Dientamoeba fragilis and Cryptosporidium spp.

Results

By molecular methods, the most common human parasite was Blastocystis sp. (prevalence, 45% in PS and 71% in SM), followed by D. fragilis (13.6% in PS, and 18.4% in SM) and G. duodenalis (18.2% in PS and 7.9% in SM); Cryptosporidium spp. were not detected. Sequence analysis revealed large genetic variation among Blastocystis samples, with subtypes (STs) 1 and 3 being predominant, and with the notable absence of ST4. Among G. duodenalis samples, assemblages A and B were detected in humans, whereas assemblages A, C and D were found in dogs. Finally, all D. fragilis samples from humans were genotype 1. A single dog was found infected with Cryptosporidium canis. River water samples were negative for the investigated parasites.

Conclusions

This study showed a high carriage of intestinal parasites in asymptomatic individuals from two poor Brazilian villages, and highlighted a large genetic variability of Blastocystis spp. and G. duodenalis.

Pigs as natural hosts of Dientamoeba fragilis genotypes found in humans

Dientamoeba fragilis is a common intestinal parasite in humans. Transmission routes and natural host range are unknown. To determine whether pigs are hosts, we analyzed 152 fecal samples by microscopy and molecular methods. We confirmed that pigs are a natural host and harbor genotypes found in humans, suggesting zoonotic potential.

Detection of Giardia duodenalis assemblages A and B in human feces by simple, assemblage-specific PCR assays

The flagellated protozoan Giardia duodenalis is a common gastrointestinal parasite of mammals, including humans. Molecular characterizations have shown the existence of eight genetic groups (or assemblages) in the G. duodenalis species complex. Human infections are caused by assemblages A and B, which infect other mammals as well. Whether transmission routes, animal reservoirs and associations with specific symptoms differ for assemblage A and assemblage B is not clear. Furthermore, the occurrence and clinical significance of mixed (A+B) infections is also poorly understood. To date, the majority of PCR assays has been developed to identify all G. duodenalis assemblages based on the use of primers that bind to conserved regions, yet a reliable identification of specific assemblages is better achieved by ad hoc methods. The aim of this work was to design simple PCR assays that, based on the use of assemblage-specific primers, produce diagnostic bands of different lengths for assemblage A and B. We first generated novel sequence information from assemblage B, identified homologous sequences in the assemblage A genome, and designed primers at six independent loci. Experiments performed on DNA extracted from axenic cultures showed that two of the six assays can detect the equivalent of a single cyst and are not negatively influenced by disproportions between DNA of each assemblage, at least up to a 9∶1 ratio. Further experiments on DNAs extracted from feces showed that the two assays can detect both assemblages in single tube reactions with excellent reliability. Finally, the robustness of these assays was demonstrated by testing a large collection of human isolates previously typed by multi-locus genotyping.

Giardia duodenalis is an important cause of diarrhoea in humans worldwide, even if the burden of infection is higher in developing countries where the poor sanitary conditions favour the contamination of water and food with infective cysts. The parasite is considered as a species complex that comprises at least eight distinct genetic groups, referred to as assemblage A to H. Humans are infected only by assemblages A and B, which can only be distinguished by molecular methods. The clinical manifestations of giardiasis in humans are highly variable and range from the absence of symptoms to acute or chronic diarrhoea. Since genetic traits that influence the virulence are yet unknown, the identification of the assemblage is considered a primary element in the study of human giardiasis. Current methods are time consuming and/or require expensive instruments. Here, we describe the development and application of single step PCR methods that allow to detect and distinguish assemblages A and B from human fecal specimens simply by gel electrophoresis of the amplification products. The novelty of the assays described in our manuscript is the reliability in detecting mixed infections and the applicability of the methodology in laboratories with basic molecular equipment.

A rare Cryptosporidium parvum genotype associated with infection of lambs and zoonotic transmission in Italy

An outbreak of cryptosporidiosis occurred in a mixed sheep/cattle farm of Central Italy in October 2011. A total of 450 ovines (250 sheep and 200 lambs) and 140 bovines (130 cows and 10 calves) were housed in two separated units, at the time of the outbreak. About half of the lambs had diarrhea due to Cryptosporidium sp. with a mortality rate of 80%; calves were not infected. Genomic DNA was extracted from an archived slide and from fecal specimens, and the parasite was identified as Cryptosporidium parvum by PCR and sequence analysis at the CpA135 gene. Genotyping at the GP60 gene showed the presence of a very rare genotype, IIaA20G2R1. Shortly after the outbreak was identified, the son of the farm's owner, aged 18 months, experienced an acute gastroenteritis and was hospitalized due to recurrent episodes of diarrhea, fever, vomiting and lack of appetite. The feces tested negative for bacteria and viruses, whereas cryptosporidiosis was diagnosed by microscopy and an immunochromatographic test. Molecular typing identified the C. parvum genotype IIaA20G2R1 in the feces of the child. This is the first case of transmission of cryptosporidiosis in Italy involving lambs as source of oocysts infectious to humans.

The immunological selection of recombinant peptides from Cryptosporidium parvum reveals 14 proteins expressed at the sporozoite stage, 7 of which are conserved in other apicomplexa

Cryptosporidium parvum is an apicomplexan parasite that infects various mammals, including humans, yet no specific treatment has been developed. C. parvum sporozoites are the initial invasive forms that infect the intestinal epithelial cells of the host. To identify novel proteins expressed at the sporozoite stage, we analyzed around 100 recombinant peptides from a C. parvum expression library with an anti-sporozoite serum. We selected 14 peptides recognized by the serum and identified the corresponding genes in the C. parvum genomic database. Twelve of the 14 genes had been previously annotated in the genome database, whereas 2 of them (the CpC2C and the CpMT1 genes) were newly identified. We established that 13 of the 14 genes are expressed in the sporozoites and that the only multi-exon gene (CpC2C) produces a detectable amount of unspliced mRNA. The search for conserved domains revealed various structural features of these proteins, including signal peptides, transmembrane domains, WD repeats, C2 domain, and Myosin tails. Interestingly, among the 14 proteins, we also identified a putative rhomboid (CpRom) which, similarly to those found in other apicomplexa, could be involved in the host-cell invasion process. The search for similar proteins, conducted on 13 proteins, showed that 4 of these proteins belong to widely conserved families, whereas 7 of them are of apicomplexan origin and only 2 are restricted to the Cryptosporidium genus.

Proteomics analysis and protein expression during sporozoite excystation of Cryptosporidium parvum (Coccidia, Apicomplexa)

Cryptosporidiosis, caused by coccidian parasites of the genus Cryptosporidium, is a major cause of human gastrointestinal infections and poses a significant health risk especially to immunocompromised patients. Despite intensive efforts for more than 20 years, there is currently no effective drug treatment against these protozoa. This study examined the zoonotic species Cryptosporidium parvum at two important stages of its life cycle: the non-excysted (transmissive) and excysted (infective) forms. To increase our understanding of the molecular basis of sporozoite excystation, LC-MS/MS coupling with a stable isotope N-terminal labeling strategy using iTRAQ reagents was used on soluble fractions of both non-excysted and excysted sporozoites, i.e. sporozoites both inside and outside oocysts were examined. Sporozoites are the infective stage that penetrates small intestinal enterocytes. Also to increase our knowledge of the C. parvum proteome, shotgun sequencing was performed on insoluble fractions from both non-excysted and excysted sporozoites. In total 303 C. parvum proteins were identified, 56 of which, hitherto described as being only hypothetical proteins, are expressed in both excysted and non-excysted sporozoites. Importantly we demonstrated that the expression of 26 proteins increases significantly during excystation. These excystation-induced proteins included ribosomal proteins, metabolic enzymes, and heat shock proteins. Interestingly three Apicomplexa-specific proteins and five Cryptosporidium-specific proteins augmented in excysted invasive sporozoites. These eight proteins represent promising targets for developing vaccines or chemotherapies that could block parasite entry into host cells.

Apicomplexa genes involved in the host cell invasion: the Cpa135 protein family

The availability of a bulk of genomic data of Apicomplexa parasites is a unique opportunity to identify groups of related proteins that are characteristic of this phylum. The Cpa135 protein of Cryptosporidium parvum is expressed and secreted through the apical complex at the invasive stage of sporozoite. This protein is characterised by an LCCL domain, a common trait of various secreted proteins within Apicomplexa. Using the Cpa135 as a "virtual template", we have identified Cpa135 orthologous genes in four apicomplexan species (Plasmodium falciparum, Theileria parva, Toxoplasma gondii and Eimeria tenella). In addition, the architecture of the deduced proteins shows that the Cpa135-related proteins are a distinct family among the apicomplexan LCCL proteins.

Cryptosporidium parvum at different developmental stages modulates host cell apoptosis in vitro

We studied apoptosis in a human ileocecal adenocarcinoma tumor cell line (HCT-8) infected with Cryptosporidium parvum, from 2 to 72 h postinfection (h.p.i.). At 2 h.p.i., the percentage of annexin V-positive cells in the cell culture had increased to 10% compared to 2.5% in noninfected control culture; sorted infected cells expressed mRNA of FasL, the active form of caspase 3, and high caspase 3 activity, whereas the noninfected neighboring cells sorted from the same culture showed no signs of apoptosis. At 24 h.p.i., the percentages of early (annexin V positive) and late (DNA fragment) apoptotic cells were 13 and 2%, respectively, in the entire cell culture, and these percentages were not statistically significant in comparison with those from noninfected control cultures. At this time, sorted infected cells expressed the inactive form of caspase 3, a low caspase 3 activity, and the antiapoptotic protein Bcl-2. Noninfected cells sorted from the same culture showed expression of the active form of caspase 3, a moderate caspase 3 activity, and no Bcl-2 expression. At 48 h.p.i., the percentages of early and late apoptotic cells and caspase 3 activity had increased in the total cell culture, and both sorted infected and noninfected cells showed the active form of caspase 3. These results show that C. parvum, depending on its developmental stage, can inhibit (at the trophozoite stage) or promote (at the sporozoite and merozoite stages) host cell apoptosis, suggesting that it is able to interact with and regulate the host-cell gene expression.

A new modular protein of Cryptosporidium parvum, with ricin B and LCCL domains, expressed in the sporozoite invasive stage

The recombinant SA35 peptide has been described as an antigenic portion of a larger Cryptosporidium parvum protein. We identified and characterized the encoding Cpa135 gene and the entire protein, Cpa135. The Cpa135 gene was found to consist of a single exon of 4671 bp, and the mRNA transcribed in the sporozoites was identified. The predicted 1556 amino-acid protein showed the presence of domains which are widely conserved also in other unrelated phylogenetic groups (i.e. a ricin B and a LCCL motif). Comparison of Cpa135 sequence with genomic and protein databases revealed many related genes in other apicomplexan species and high homology with CCP2 protein from Plasmodium yoelii and Plasmodium berghei. The Cpa135 protein was identified and localized by using a monoclonal antibody (Mab) directed against the SA35 antigen (anti-SA35). In oocyst-sporozoite lysate, the anti-SA35 MAb recognized a 135 kDa protein that forms a protein complex larger than 200 kDa, which is mediated by disulfide bridges. Cpa135 synthesis was up-regulated during the excystation process. After host-cell invasion, Cpa135 gene expression was undetectable up to 48 h, whereas mRNA synthesis was newly observed at 72 h post-infection. The Cpa135 protein was localized in the apical complex, and it was found to be secreted by sporozoites during their gliding. Cpa135 persisted during the intracellular stages of the parasite, and it defined the boundaries of the parasitophorous vacuole in the infected cells. The unique array of domains and the homology with other apicomplexan proteins indicate that the Cpa135 protein is representative of a new family of proteins.

Detection and counting of Cryptosporidium parvum in HCT-8 cells by flowcytometry

The objective of the present study was to evaluate flowcytometry analysis (FCA) as a tool for rapidly and objectively estimating the percentage of cells infected with Cryptosporidium parvum in an in vitro model. We compared the results to those obtained with immunofluorescence assay (IFA) and evaluated the intra-assay variability of both assays and the inter-assay variability of IFA. Human ileocecal adenocarcinoma cells (HCT-8) were infected with different doses of excysted oocysts. After 24 hours, cells were analysed by FCA and by IFA using a monoclonal antibody that recognises a C. parvum antigenic protein and a lectin that binds with glycoproteins present in the parasitophorous vacuoles. The coefficient of variability in terms of the percentage of infected cells was lower for FCA (i.e., 13-14%) than for IFA (i.e., 27-38% when performed by a single operator and 19-22% when performed by three operators), suggesting that FCA is more accurate, in that it is not subject to operator expertise. FCA also has the advantage of allowing the entire culture to be examined, thus avoiding problems with heterogeneity among microscopic fields. In light of these results, this method could also be used to test new anti-Cryptosporidium drugs.

Cryptosporidium parvum-specific CD4 Th1 cells from sensitized donors responding to both fractionated and recombinant antigenic proteins

T-cell-mediated immunity plays a central role in the host response to Cryptosporidium parvum. Human T-cell clones (TCC) were isolated from peripheral blood mononuclear cells of five healthy donors with prior cryptosporidiosis by use of a C. parvum crude extract, two antigen fractions obtained by ion-exchange chromatography (IEC1 and IEC2), and two recombinant peptides (SA35 and SA40) from C. parvum sporozoites. The T-cell lines derived from the one recently infected donor had a higher proportion (26 to 38%) of T cells exhibiting the gamma/delta T-cell receptor (gamma/delta-TCR) than those from donors who had recovered from cryptosporidiosis several years earlier, suggesting that the gamma/delta T-cell population is involved in the early stage of the infection. The specific TCC had the alpha/beta-TCR, had the phenotype CD45RO(+) CD4(+) CD8(-), and were characterized by either hyperproduction of gamma interferon (IFN-gamma) alone, with a Th1 profile, or IFN-gamma hyperproduction together with interleukin-4 (IL-4) or IL-5 production, with a Th0 profile. SA35, SA40, IEC1, and IEC2 may be considered good targets of the cellular response against C. parvum and may play a role in maintaining the T-cell-mediated memory response to this parasite. Furthermore, the SA35 and SA40 peptides may be regarded as immunodominant antigens involved in the maintenance of the T-cell response in healthy C. parvum-sensitized persons.

Colloidal anticancer drugs bioavailabilities in oral administration models

Liposomes have been prepared with a polymerised core. Drug release and gastrointestinal (GI) degradation of liposomes with this polymerised core was slightly less important than those of classical liposomes. Vincristine, 5-fluorouracil (5-FU), and methotrexate (MTX) have been incorporated into the liposomes, and studies carried out using the differentiated cell lines Caco-2 and TC7, and with 150 histologically normal sections of human colon. Encapsulation of the drugs in liposomes had variable effects, depending on the test system and the drug used. For 5-FU and MTX calculated to be in a therapeutic range, liposomal formulation enhanced drug permeation, but not for the other drugs tested. In the excised human colon model, the treatment history of the patients can affect bioavailability: pre-operative radiation increased the drug tissue uptake. Transmucosal transport of ions was modified by prior chemotherapy. These results should be taken into account in the design of oral anticancer treatments both at the level of nutritional and pharmacological considerations.

Indinavir reduces Cryptosporidium parvum infection in both in vitro and in vivo models

The use of highly active antiretroviral therapy in persons with acquired immunodeficiency syndrome has reduced the prevalence of infection with Cryptosporidium parvum and the length and severity of its clinical course. This effect has in most cases been attributed to the recovery of the host immunity; however, some works suggest that human immunodeficiency virus protease inhibitors, indinavir in particular, which is one of the human immunodeficiency virus protease inhibitors used in highly active antiretroviral therapy, may be capable of controlling Microsporidia and Cryptosporidium infections, which are refractory to other treatments. The objective of the present study was to investigate the effect of human immunodeficiency virus protease inhibitors on C. parvum infections. Since preliminary experiments using ritonavir, saquinavir, and indinavir showed a drastic reduction of C. parvum infection both in vivo (neonatal Balb/c mice) and in vitro (human ileocecal adenocarcinoma tumour cell line) models, indinavir alone was tested in successive experiments. In vitro, the treatment of the sporulated oocysts with different concentrations of indinavir reduced the percentage of human ileocecal adenocarcinoma tumour cell line infected cells in a dose-dependent manner. For established infection, the treatment with 50 microM of indinavir decreased the percentage of infected cells in a time-dependent manner. In vivo, mice treated with indinavir at the same time they were infected with the oocysts showed a 93% reduction in the number of oocysts present in the entire intestinal contents and a 91% reduction in the number of intracellular parasites in the ileum. For established infection, indinavir treatment reduced the number of oocysts in the entire intestinal content by about 50% and the number of intracellular parasites in the ileum by about 70%. These data show that indinavir directly interferes with the cycle of C. parvum, resulting in a marked reduction in oocyst shedding and in the number of intracellular parasites. Protease inhibitors could be considered as good candidates for the treatment of cyptosporidiosis in immunosuppressed persons.

Composite integron array generated by insertion of an ORF341-type integron within a Tn21-like element

Two class 1 integrons, In-t1 and In-t2, were previously identified in IncFI plasmids of Salmonella enterica serotype Typhimurium. Molecular analysis revealed a close physical link between the two integrons. In-t1 is preceded by the transposase genes of Tn21, whereas In-t2 is located downstream the 3'-conserved segment (3'-CS) of In-t1, in a head-to-tail configuration. In-t1 shows a peculiar sequence downstream the 3'-CS, containing an extended version of the open reading frame known as ORF341 (referred to as ORF341E) and a novel trimethoprim resistance gene, designated dfrA18. Retrospective analysis provided evidence for In-t1 insertion within Tn1935, a Tn21-related transposon identified in IncFI plasmids circulating among epidemic clones of multidrug-resistant S. enterica during the 1970s. Structural comparison between Tn21 derivatives from recent and ancestor IncFI plasmids showed that In-t2 has been conserved by these replicons. In-t1 belongs to a novel family of class 1 integrons containing the ORF341E sequence, and appears to have been acquired by IncFI plasmids after the assembly of Tn1935. In-t1 insertion occurred within the 5'-conserved segment (5'-CS) proximal region of the resident In-t2.

Characterization of plasmids carrying CMY-2 from expanded-spectrum cephalosporin-resistant Salmonella strains isolated in the United States between 1996 and 1998

Sequencing of DNA from 15 expanded-spectrum cephalosporin (e.g., ceftriaxone)-resistant Salmonella isolates obtained in the United States revealed that resistance to ceftriaxone in all isolates was mediated by cmy-2. Hybridization patterns revealed three plasmid structures containing cmy-2 in these 15 isolates. These data suggest that the spread of cmy-2 among Salmonella strains is occurring through mobilization of the cmy-2 gene into different plasmid backbones and consequent horizontal transfer by conjugation.

Multiple-antibiotic resistance mediated by structurally related IncL/M plasmids carrying an extended-spectrum beta-lactamase gene and a class 1 integron

A conjugative IncL/M plasmid (pSEM) conferring resistance to gentamicin, amikacin, kanamycin, sulfonamides, and expanded-spectrum cephalosporins was found in pathogenic strains of Salmonella enterica serotype Typhimurium. Resistance to aminoglycosides was encoded by a sul1-type class 1 integron (In-t3). An extended-spectrum beta-lactamase gene, bla(SHV-5), was identified 3. 5 kb downstream of the integrase (intI1) gene of In-t3. Nucleotide sequence analysis of the 5.3-kb bla(SHV-5)-In-t3 region of pSEM highlighted striking similarities with IncL/M plasmids isolated from nosocomial gram-negative pathogens, conferring resistance to expanded-spectrum cephalosporins and aminoglycosides.

Identification and characterisation of three antigenic proteins from Cryptosporidium parvum sporozoites using a DNA library expressing poly-histidine tagged peptides

To identify antigenic peptides of the parasite Cryptosporidium parvum, an expression library that allows for the production of chimeric proteins fused with a 6-histidine tag was made. The library was screened with C. parvum sporozoite rabbit anti-serum, and three positive clones (sa20, sa35, and sa40) were identified. The corresponding recombinant proteins (SA20, SA35, and SA40) were expressed in Escherichia coli and purified by metal-affinity chromatography. The sequence of sa20 and sa35 clones did not show any homology with known genes or proteins, whereas the 5' end of the sa40 clone showed homology with two previously identified C. parvum sequences. Hybridisations to intact chromosomes fractionated by pulsed-field gel electrophoresis revealed that the sa35 and sa40 sequences are localised on chromosome VII, whereas the sa20 sequence is localised on chromosome VI. Reverse transcriptase-PCR experiments showed the presence of mRNAs for sa35 and sa40 in the oocyst, whereas the sa20 mRNA was undetectable in this stage. The serological response to the three proteins was assayed in C. parvum-immunised rabbits and in immunocompetent individuals with cryptosporidiosis. The Western blot results indicated that rabbits, challenged with a sporozoite crude antigen or with an oocyst crude antigen, were highly responsive to these three antigens. Human serum samples showed a response to the three proteins, although the response to SA20 appeared to be unrelated to a recent C. parvum infection. These results suggest that the SA35 and the SA40 proteins may be useful in detecting C. parvum infections.

Antibiotic resistance conferred by a conjugative plasmid and a class I integron in Vibrio cholerae O1 El Tor strains isolated in Albania and Italy

Multidrug-resistant Vibrio cholerae O1 El Tor strains isolated during the 1994 outbreak of cholera in Albania and Italy were characterized for the molecular basis of antibiotic resistance. All strains were found to be resistant to tetracycline, streptomycin, spectinomycin, trimethoprim, sulfathiazole, and the vibriostatic compound O/129 (2,4-diamino-6,7-diisopropylteridine). Resistance genes were self-transferable by a conjugative plasmid of about 60 MDa, with the exception of spectinomycin resistance, which was conferred by the aadA1 gene cassette located in the bacterial chromosome within a class 1 integron. The resistance to trimethoprim and O/129 was conferred by the dfrA1 gene, which was present on the plasmid. Although the dfrA1 gene is known to be borne on an integron cassette, class 1, 2, or 3 intI genes were not detected as part of the plasmid DNA from the strains studied.

Class 1 integron-borne multiple-antibiotic resistance carried by IncFI and IncL/M plasmids in Salmonella enterica serotype typhimurium

The presence and genetic content of integrons were investigated for 37 epidemiologically unrelated multiple-drug-resistant strains of Salmonella enterica serotype Typhimurium from humans. All isolates were resistant to ampicillin, chloramphenicol, kanamycin, streptomycin, sulfonamides, and trimethoprim, as well as to tetracycline and/or nalidixic acid; 20% of them were also resistant to gentamicin and amikacin. Three different class 1 integrons (In-t1, In-t2, and In-t3) were identified by Southern blot hybridization, PCR, and DNA sequencing, and these integrons were found to carry the aadB, catB3, oxa1, aadA1a, aacA4, and aacC1 gene cassettes. Integrons In-t1 (aadB and catB3) and In-t2 (oxa1 and aadA1a) were both located on a conjugative IncFI plasmid of 140 kb. In-t3 (aacA4, aacC1, and aadAIa) was located on an IncL/M plasmid of 100 kb which was present, in association with the IncFI plasmid, in gentamicin- and amikacin-resistant isolates. Despite the extensive similarity at the level of the antibiotic resistance phenotype, integrons were not found on the prototypic IncFI plasmids carried by epidemic Salmonella strains isolated during the late 1970s. The recent appearance and the coexistence of multiple integrons on two conjugative plasmids in the same Salmonella isolate are examples of how mobile gene cassettes may contribute to the acquisition and dissemination of antibiotic resistance.

The uvp1 gene on the R46 plasmid encodes a resolvase that catalyzes site-specific resolution involving the 5'-conserved segment of the adjacent integron In1

The product of the uvp1 gene of the R46 plasmid, a member of the DNA invertase-resolvase family, was studied to characterize its recombination activity on the R46 plasmid. The purified Uvp1 protein specifically binds to a 256-bp DNA fragment located immediately upstream of the uvp1 gene itself, and overlapping the 5'-conserved segment (5'-CS) of the R46 integron In1. We identified on this fragment a putative resolution (res) site. Using an in vitro assay, we demonstrated the ability of the protein to resolve a synthetic cointegrate containing a direct repeat of the res site. In vivo, we obtained cointegrate resolution in Uvp1-expressing recA- cells. Sites I and II, subsites of the putative res site, lie within the outer boundary of the integron 5'-CS which is common to all the known integrons. Furthermore, a 69-bp DNA element (containing site I) is required for cointegrate resolution. We propose that this recombination mechanism protects R46 plasmid against unequal distribution following fusion with either identical or different integron-bearing plasmids. Moreover, Uvp1 might have a role in generating gene cassette diversity between the two conserved segments of the integron.

The gene coding for proteins HC and HI-30 of inter-alpha-trypsin inhibitor maps to 9q22.3----q33

Proteins HC and HI-30 of inter-alpha-trypsin inhibitor light chain are two plasma proteins. They are encoded by the same monocistronic mRNA. Their function is probably related to the regulation of immunologic and/or inflammatory responses. Using a genomic DNA probe and a panel of somatic cell hybrids we have mapped the gene coding for the proteins to chromosome 9. In situ hybridization experiments refined the assignment to the region 9q22.3----q33.