This project was funded by Case Western Reserve University startup funds provided to E. Jolly. Infected snails were provided by the Schistosome Resource Center, NIH-NIAID (NIAID Contract No. HHSN272201000009I). We also thank Chris King and Ronald Blanton for support in securing infected schistosome snails and for helpful discussions.

Safety measures:
Schistosome cercariae can directly penetrate the skin without the needs of a cut or pores, and cause the chronic disease schistosomiasis. S. mansoni is a biosafety level 2 organism, therefore proper personal protective equipment and proper safety measures must be followed when working with infective cercaria. Most of the equipment necessary to grow and transform schistosomes is standard, with a few key exceptions noted in the table at the end of the protocol. All cercarial work should be done in an isolated room. Schistosomules should be cultured in a sterile, approved biosafety hood. Two layers of nitrile or latex gloves should be worn, as should a lab coat, a waterproof pair of shoes, pants with no holes or tears, and waterproof sleeve protectors for your wrists and arms. In case of an accidental spill, immediately spray contaminated area with 70% ethanol or 10% bleach, rubbing vigorously if on your person. This will be sufficient to disable the parasite, but all possible infections should be reported and taken seriously. Although schistosomules are not innately infective, institutional guidelines vary, and should be consulted to determine whether BSL2 precautions are required during noninfectious life stages. Disinfect all surfaces that come into contact with any potentially infectious substance after the experiment is performed and discard waste in an approved biohazard container.
NOTE: Cover snail host bins 1 to 2 days prior to shedding and protect from light
1.	Harvesting cercariae from the snail host
<ol>
<li>Fill a clean, 500mL beaker free of detergents halfway full with distilled water equilibrated to room temperature. If working with host snails infected with miracidia on different dates, use a separate beaker for each infection date (This is particularly important if the snails will be reused for future experiments). The size of the beaker can also be smaller depending on the experience of the user.</li>
<li>Collect infected snail hosts you wish to shed and carefully deposit them in the beaker using a standard aquarium fish net and general purpose forceps as needed.</li>
<li>Place beaker on an emergency spill tray approximately 8 to 12 inches beneath an incandescent light source. Let stand for 1-2 hours under the light. Cercariae exit the snail host when exposed to bright light.</li>
<li>Carefully filter out snails from the cercariae mixture. Take extra safety precautions, as mixture is highly infectious. Remember, cercariae can directly penetrate human skin!</li>
<li>Replace mixture under light source for about 15 minutes, allowing any particulate waste matter to settle.</li>
<li>Transfer cercariae into a clean Erlenmeyer flask using a pipet, avoiding the debris at the bottom of the beaker. Place the flask at approximately a 45&deg; angle on ice in the dark for 45 - 60 minutes, allowing cercariae to settle into one corner.</li>
<li>Use a 50 mL pipet to remove 75 to 90% of the supernatant and deposit it in beaker containing 10% bleach or 70% ethanol, taking care not to let water drops containing cercariae drip from the pipet.</li>
<li>Swirl the Erlenmeyer flask containing cercariae gently to resuspend the cercariae in solution. Use a pipet to transfer the sample to sterile 50 ml conical tubes. Place tubes again on ice for 20 minutes in the dark. Cercariae will settle towards the bottom of the tube in the dark. </li>
</ol>
2.	Manual transformation of cercariae to schistosomules
Before you begin: Make RPMI 1640 complete (RPMI, 5% Fetal Bovine Serum, 1X Pen/Strep) and warm to 37&deg;C. (It is crucial that the fetal bovine serum used has been inactivated by incubation a 56&deg;C for 1 hour as schistosomes can be sensitive to complement). 
<ol>
<li>In a biohazard hood, remove supernatant down to 5 to 10 ml of solution in each 50 ml conical using a pipettor or vacuum device. </li>
<li>Attach a 22 gauge double-ended, luer lok emulsifying needle to an appropriately sized syringe. </li>
<li>Slowly draw mixture into the syringe. Collect cercariae from all 50 ml tubes in a syringe. Be attentive of dripping.</li>
<li>Carefully turn syringe over such that the unattached needle end is up. Attach another syringe to this side of the emulsifying needle.</li>
<li>Pass the mixture through the needle a total of 40 times (20 times back and forth) to transform the cercariae. </li>
<li>Position the syringes vertically such that the mixture is contained in the bottom syringe and the top syringe is empty. Remove top syringe and disinfect in 70% Ethanol. </li>
<li>Deposit mixture drop by drop into a clean high walled 100mm x 50mm pyrex dish or crystallizing dish. Disinfect needle and syringe in 70% Ethanol. </li>
<li>Add 37&deg;C RPMI 1640 complete media such that the bottom of the Petri dish is completely covered, as if pouring a Luria broth plate.</li>
<li>Swirl gently to collect schistosomules in the center of the Petri dish. Avoid splashing. 
Note: It may be useful to turn off the hood light for this step to more adequately visualize the schistosomules in the center.</li>
<li>Immediately deposit concentrated schistosomules into a fresh 12-well cell culture plate well using a sterile dropper. </li>
<li>Repeat 2.9 and 2.10 until schistosomules are no longer present in the center of the dish (approximately 10 times). Deposit each subsequent collection in a fresh well.</li>
<li>Fill each well up halfway (&tilde;1.5 mL ) with prewarmed RPMI complete media. </li>
<li>Visualize on an inverted microscope to verify presence of schistosomules and absence of cercariae. </li>
<li>Grow the schistosomules in a CO2 incubator set to 37&deg;C and 5% CO2.</li>
</ol>
3.	Representative Results: 
Pending transfer of transformed schistosomules into culture media, visualization under an inverted bright-field microscope (See equipment table for an example) should yield an image similar to Figure 1, in which only transformed schistosomules are present in the well. Potential contaminants could include intact cercariae, severed cercarial tails, or other debris. If no inverted microscope is available, a standard microscope or even a dissection scope will be sufficient to visualize the schistosomules. Note that this procedure does not always transform 100% of cercariae. 
<img src="/files/ftp_upload/3191/3191fig1.jpg" alt="Figure 1"/> Figure 1: Transformed Schistosomulum
<img src="/files/ftp_upload/3191/3191fig2.jpg" alt="Figure 2"/> Figure 2: Cercariae and Severed Tails

<ol>
	<li>Ross, A. G., Bartley, P. B., Sleigh, A. C., Olds, G. R., Li, Y., Williams, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Schistosomiasis.">Schistosomiasis.</a> N Engl J Med. 346, 1212-1220 (2002).</li><li>Steinmann, P., Keiser, J., Bos, R., Tanner, M., Utzinger, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Schistosomiasis+and+water+resources+development:+systematic+review,+meta-analysis,+and+estimates+of+people+at+risk.">Schistosomiasis and water resources development: systematic review, meta-analysis, and estimates of people at risk.</a> Lancet Infect Dis. 6, 411-425 (2006).</li><li>Savioli, L., Albonico, M., Engels, D., Montresor, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Progress+in+the+prevention+and+control+of+schistosomiasis+and+soil-transmitted+helminthiasis.">Progress in the prevention and control of schistosomiasis and soil-transmitted helminthiasis.</a> Parasitol Int. 53, 103-113 (2004).</li><li>King, C. H., Dickman, K., Tisch, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reassessment+of+the+cost+of+chronic+helmintic+infection:+a+meta-analysis+of+disability-related+outcomes+in+endemic+schistosomiasis.">Reassessment of the cost of chronic helmintic infection: a meta-analysis of disability-related outcomes in endemic schistosomiasis.</a> Lancet. 365, 1561-159 (2005).</li><li>Haas, W., Grabe, K., Geis, C., Pach, T., Stoll, K., Fuchs, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recognition+and+invasion+of+human+skin+by+Schistosoma+mansoni+cercariae:+the+key-role+of+L-arginine.+Parasitology.">Recognition and invasion of human skin by Schistosoma mansoni cercariae: the key-role of L-arginine. Parasitology.</a> 124, 153-167 (2002).</li><li>Grabe, K., Haas, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Navigation+within+host+tissues:+cercariae+orientate+towards+dark+after+penetration.">Navigation within host tissues: cercariae orientate towards dark after penetration.</a> Parasitol Res. 93, 111-113 (2004).</li><li>Shiff, C. J., Cmelik, S. H., Ley, H. E., Kriel, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+influence+of+human+skin+lipids+on+the+cercarial+penetration+responses+of+Schistosoma+haematobium+and+Schistosoma+mansoni.">The influence of human skin lipids on the cercarial penetration responses of Schistosoma haematobium and Schistosoma mansoni.</a> J Parasitol. 58, 476-480 (1972).</li><li>Saladin, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Schistosoma+mansoni:+cercarial+responses+to+irradiance+changes.">Schistosoma mansoni: cercarial responses to irradiance changes.</a> J Parasitol. 68, 120-124 (1982).</li><li>Chai, M., McManus, D. P., McInnes, R., Moertel, L., Tran, M., Loukas, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcriptome+profiling+of+lung+schistosomula,+in+vitro+cultured+schistosomula+and+adult+Schistosoma+japonicum.">Transcriptome profiling of lung schistosomula, in vitro cultured schistosomula and adult Schistosoma japonicum.</a> Cell Mol Life Sci. 63, 919-929 (2006).</li><li>Gobert, G. N., Tran, M. H., Moertel, L., Mulvenna, J., Jones, M. K., McManus, D. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcriptional+changes+in+Schistosoma+mansoni+during+early+schistosomula+development+and+in+the+presence+of+erythrocytes.">Transcriptional changes in Schistosoma mansoni during early schistosomula development and in the presence of erythrocytes.</a> PLoS Negl Trop Dis. 4, (2011).</li><li>Basch, P. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cultivation+of+Schistosoma+mansoni+in+vitro.+I.+Establishment+of+cultures+from+cercariae+and+development+until+pairing.">Cultivation of Schistosoma mansoni in vitro. I. Establishment of cultures from cercariae and development until pairing.</a> J Parasitol. 67, 179-185 (1981).</li><li>Yoshino, T. P. &. a. m. p. ;. a. m. p., Laursen, J. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Production+of+Schistosoma+mansoni+daughter+sporocysts+from+mother+sporocysts+maintained+in+synxenic+culture+with+Biomphalaria+glabrata+embryonic+(Bge)+cells.">Production of Schistosoma mansoni daughter sporocysts from mother sporocysts maintained in synxenic culture with Biomphalaria glabrata embryonic (Bge) cells.</a> J Parasitol. 81, 714-722 (1995).</li><li>Colley, D. G., Wikel, S. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Schistosoma+mansoni:+simplified+method+for+the+production+of+schistosomules.">Schistosoma mansoni: simplified method for the production of schistosomules.</a> Exp Parasitol. 35, 44-51 (1974).</li><li>Lazdins, J. K., Stein, M. J., David, J. R., Sher, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Schistosoma+mansoni:+rapid+isolation+and+purification+of+schistosomula+of+different+developmental+stages+by+centrifugation+on+discontinuous+density+gradients+of+Percoll.">Schistosoma mansoni: rapid isolation and purification of schistosomula of different developmental stages by centrifugation on discontinuous density gradients of Percoll.</a> Exp Parasitol. 53, 39-44 (1982).</li><li>Cousin, C. E., Stirewalt, M. A., Dorsey, C. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Schistosoma+mansoni:+ultrastructure+of+early+transformation+of+skin-+and+shear-pressure-derived+schistosomules.">Schistosoma mansoni: ultrastructure of early transformation of skin- and shear-pressure-derived schistosomules.</a> Exp Parasitol. 51, 341-365 (1981).</li><li>Lewis, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Schistosomiasis.">Schistosomiasis.</a> Curr Protoc Immunol. Chapter 19, 1-1 (2001).</li></ol>

No conflicts of interest declared.

Several potential problems could arise during the transformation procedure; however, this protocol is designed to avoid most of these problems. One potential hazard is the clogging of the emulsifying needle, which usually arises due to debris left over from the harvesting in step 1.3. Be sure to allow all particulate matter to settle in step 1.5 and to transfer the cercariae carefully in step 1.6 to avoid this problem. Also, as described before, working inside a biological safety cabinet, use of personal protective equipment (even face shields) and avoidance of excessive pressure on the syringes is advisable. 
Detached cercarial tails can be visualized in the media, which is indicative of poor separation during step 2.9. The tails exhibit a spasm-like motion and have a distinct shape (see Figure 2), and thusly are easily distinguishable from the schistosomules. The tails can be removed by washing the schistosomules in excess of RPMI complete allowing the schistosomules to settle. The tails will remain floating and can be vacuumed off.
If intact cercariae are present in the media, the transformation in step 2.5 was not executed properly. An image of an intact cercaria is depicted in Figure 3b for reference. If this problem occurs, insure that the emulsifying needle being used is of the proper size. Also, the number of times the cercarial mixture is passed through the needle can be increased, although 40 times is typically much more than enough to approach 100% shearing of the cercarial tails. 
Transformation of cercaria into schistosomules was first described in 1974 by Colley and Wikel (13). Since then, preparation of schistosomules has been done using either the shearing strategy with a needle and syringe as described in this protocol, or using a vortexing approach and separated with gradients of percoll (14, 15) or swirling as demonstrated in this paper. These two techniques for preparing schistosomules are beautifully described by Fred Lewis (16) and more information for further culturing of schistosomules for long-term growth can be found at the NIAID Schistosome Resource Center (<a href="http://www.schisto-resource.org/">www.schisto-resource.org</a>).

<table border="1">
	<tbody>
		<tr>
			<th>Name of reagent	</th>
			<th>Company	</th>
			<th>Catalogue number</th>
		</tr>
		<tr>
			<td>22g x 2-7/8" Emulsifying needle		</td>
			<td>Fisher Scientific</td>
			<td>14-825-17G</td>
		</tr>
		<tr>
			<td>RPMI 1640 Medium 1X (500ml)		</td>
			<td>Invitrogen</td>
			<td>11835030</td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum (FBS) heat inactivated</td>
			<td>Invitrogen</td>
			<td>10082139</td>
		</tr>
		<tr>
			<td>Penicillin/Streptomycin (100X)</td>
			<td>Invitrogen</td>
			<td>15070063</td>
		</tr>
		<tr>
			<td>Crystallizing Dish (100mm)</td>
			<td>Fisher Scientific</td>
			<td>08-741D</td>
		</tr>
		<tr>
			<td>General Purpose Tweezers</td>
			<td>Fisher Scientific</td>
			<td>10-316C</td>
		</tr>
		<tr>
			<td>Petco Aquarium net for brine shrimp	</td>
			<td>Petco</td>
			<td>SKU:1190954</td>
		</tr>
	</tbody>
</table>

cercarial transformation and in vitro cultivation of schistosoma mansoni schistosomules

Schistosome parasites are the causative agents of schistosomiasis, a chronically debilitating disease that affects over 200 million people globally and ranks second to malaria among parasitic diseases in terms of public health and socio-economic impact (1-4). Schistosome parasites are trematode worms with a complex life cycle interchanging between a parasitic life in molluscan and mammalian hosts with intervening free-swimming stages. Briefly, free-swimming cercariae infect a mammalian host by penetrating the skin with the aid of secreted proteases, during which time the cercariae lose their tails, transforming into schistosomules. The schistosomules must now evade the host immune system, develop a gut for digestion of red blood cells, and migrate though the lungs and portal circulation en route to their final destination in the hepatic portal system and eventually the mesenteric veins (for S. mansoni) where male and female worms pair and mate, producing hundreds of eggs daily. Some of the eggs are excreted from the body into fresh water, where the eggs hatch into free-swimming miracidia (5-10). The miracidia infect specific snail species and transform into mother and daughter sporocysts, which in turn, produce infective cercariae, completing the life cycle. Unfortunately, the entire schistosome life cycle cannot be cultured in vitro, but infective cercariae can be transformed into schistosomules, and the schistosomules can be cultured for weeks for the analysis of schistosome development in vitro or microarray analysis. In this protocol, we provide a visual description of cercarial transformation and in vitro culturing of schistosomules. We shed infectious cercariae from the snail host Biomphalaria glabrata and manually transform them into schistosomules by detaching their tails using an emulsifying double-ended needle. The in vitro cercarial transformation and schistosomules culture techniques described avoid the use of a mammalian host, which simplifies visualization of schistosomes and facilitates the collection of the parasite for experimental analysis. in vitro transformation and culturing techniques of schistosomes have been done for years (11, 12), but no visual protocols have been developed that are available to the entire community.

Watch this Scientific Journal Video about Cercarial Transformation and in vitro Cultivation of Schistosoma mansoni Schistosomules at JoVE.com

Cercarial Transformation and in vitro Cultivation of Schistosoma mansoni Schistosomules

We describe an in vitro method for culturing schistosomula of the flatworm parasite Schistosoma mansoni, via the harvesting and transformation of infective cercariae from the fresh water snail intermediate host Biomphalaria glabrata.

Cercarial Transformation and in vitro Cultivation of Schistosoma mansoni Schistosomules

Schistosome parasites are the causative agents of schistosomiasis, a chronically debilitating disease that affects over 200 million people globally and ...

cercarial-transformation-vitro-cultivation-schistosoma-mansoni

Research

JoVE Journal

Immunology and Infection

18.0K Views.  Case Western Reserve University. We describe an in vitro method for culturing schistosomula of the flatworm parasite Schistosoma mansoni, via the harvesting and transformation of infective cercariae from the fresh water snail intermediate host Biomphalaria glabrata.

Video: Cercarial Transformation and in vitro Cultivation of Schistosoma mansoni Schistosomules

In Vitro Assay of Bacterial Adhesion onto Mammalian Epithelial Cells

To cause infections, bacteria must colonize their host. Bacterial pathogens express various molecules or structures able to promote attachment to host cells1. These adhesins rely on interactions with host cell surface receptors or soluble proteins acting as a bridge between bacteria and host. Adhesion is a critical first step prior to invasion and/or secretion of toxins, thus it is a key event to be studied in bacterial pathogenesis. Furthermore, adhered bacteria often induce exquisitely fine-tuned cellular responses, the studies of which have given birth to the field of 'cellular microbiology'2. Robust assays for bacterial adhesion on host cells and their invasion therefore play key roles in bacterial pathogenesis studies and have long been used in many pioneer laboratories3,4. These assays are now practiced by most laboratories working on bacterial pathogenesis.
Here, we describe a standard adherence assay illustrating the contribution of a specific adhesin. We use the Escherichia coli strain 27875, a human pathogenic strain expressing the autotransporter Adhesin Involved in Diffuse Adherence (AIDA). As a control, we use a mutant strain lacking the aidA gene, 2787&Delta;aidA (F. Berthiaume and M. Mourez, unpublished), and a commercial laboratory strain of E. coli, C600 (New England Biolabs). The bacteria are left to adhere to the cells from the commonly used HEp-2 human epithelial cell line. This assay has been less extensively described before6.

In Vitro Assay of Bacterial Adhesion onto Mammalian Epithelial Cells

This protocol is a simple bacterial adhesion assay consisting in counting the numbers of bacterial colony forming units that are adhered onto cultured cells. The assay is robust, independent of the adhesin studied, and numerous variations are used in most laboratories working on bacterial pathogenesis.

To cause infections, bacteria must colonize their host. Bacterial pathogens express various molecules or structures able to promote attachment to host ...

In vitro Uncoating of HIV-1 Cores

The genome of the retroviruses is encased in a capsid surrounded by a lipid envelope. For lentiviruses, such as HIV-1, the conical capsid shell is composed of CA protein arranged as a lattice of hexagon. The capsid is closed by 7 pentamers at the broad end and 5 at the narrow end of the cone1, 2. Encased in this capsid shell is the viral ribonucleoprotein complex, and together they comprise the core.
Following fusion of the viral membrane with the target cell membrane, the HIV-1 is released into the cytoplasm. The capsid then disassembles releasing free CA in the soluble form3 in a process referred to as uncoating. The intracellular location and timing of HIV-1 uncoating are poorly understood. Single amino-acid substitutions in CA that alter the stability of the capsid also impair the ability of HIV-1 to infect cells4. This indicates that the stability of the capsid is critical for HIV-1 infection.
HIV-1 uncoating has been difficult to study due to lack of availability of sensitive and reliable assays for this process. Here we describe a quantitative method for studying uncoating in vitro using cores isolated from infectious HIV-1 particles. The approach involves isolation of cores by sedimentation of concentrated virions through a layer of detergent and into a linear sucrose gradient, in the cold. To quantify uncoating, the isolated cores are incubated at 37&deg;C for various timed intervals and subsequently pelleted by ultracentrifugation. The extent of uncoating is analyzed by quantifying the fraction of CA in the supernatant. This approach has been employed to analyze effects of viral mutations on HIV-1 capsid stability4, 5, 6. It should also be useful for studying the role of cellular factors in HIV-1 uncoating.

In vitro Uncoating of HIV-1 Cores

Uncoating is an essential step in the early phase of the HIV-1 life cycle and is defined as the disassembly of the capsid shell and the release of the viral ribonucleoprotein complex (vRNP). Here, we demonstrate techniques for isolating intact cores from HIV-1 virions and for quantifying their uncoating in vitro.

The genome of the retroviruses is encased in a capsid surrounded by a lipid envelope. For lentiviruses, such as HIV-1, the conical capsid shell is ...

TransFLP &#x2014; A Method to Genetically Modify Vibrio cholerae Based on Natural Transformation and FLP-recombination

Several methods are available to manipulate bacterial chromosomes1-3. Most of these protocols rely on the insertion of conditionally replicative plasmids (e.g. harboring pir-dependent or temperature-sensitive replicons1,2). These plasmids are integrated into bacterial chromosomes based on homology-mediated recombination. Such insertional mutants are often directly used in experimental settings. Alternatively, selection for plasmid excision followed by its loss can be performed, which for Gram-negative bacteria often relies on the counter-selectable levan sucrase enzyme encoded by the sacB gene4. The excision can either restore the pre-insertion genotype or result in an exchange between the chromosome and the plasmid-encoded copy of the modified gene. A disadvantage of this technique is that it is time-consuming. The plasmid has to be cloned first; it requires horizontal transfer into V. cholerae (most notably by mating with an E. coli donor strain) or artificial transformation of the latter; and the excision of the plasmid is random and can either restore the initial genotype or create the desired modification if no positive selection is exerted. Here, we present a method for rapid manipulation of the V. cholerae chromosome(s)5 (Figure 1). This TransFLP method is based on the recently discovered chitin-mediated induction of natural competence in this organism6 and other representative of the genus Vibrio such as V. fischeri7. Natural competence allows the uptake of free DNA including PCR-generated DNA fragments. Once taken up, the DNA recombines with the chromosome given the presence of a minimum of 250-500 bp of flanking homologous region8. Including a selection marker in-between these flanking regions allows easy detection of frequently occurring transformants.
This method can be used for different genetic manipulations of V. cholerae and potentially also other naturally competent bacteria. We provide three novel examples on what can be accomplished by this method in addition to our previously published study on single gene deletions and the addition of affinity-tag sequences5. Several optimization steps concerning the initial protocol of chitin-induced natural transformation6 are incorporated in this TransFLP protocol. These include among others the replacement of crab shell fragments by commercially available chitin flakes8, the donation of PCR-derived DNA as transforming material9, and the addition of FLP-recombination target sites (FRT)5. FRT sites allow site-directed excision of the selection marker mediated by the Flp recombinase10.

TransFLP &amp;#x2014; A Method to Genetically Modify &lt;em&gt;Vibrio cholerae&lt;/em&gt; Based on Natural Transformation and FLP-recombination

A quick method to modify the genome of V. cholerae is described. These modifications include the deletion of single genes, gene clusters and genomic islands as well as the integration of short sequences (e.g. promoter elements or affinity-tag sequences). The method is based on the natural transformation and FLP-recombination.

Several methods are available to manipulate bacterial chromosomes1-3. Most of these protocols rely on the insertion of conditionally replicative plasmids ...

Using Eggs from Schistosoma mansoni as an In vivo Model of Helminth-induced Lung Inflammation

Schistosoma parasites are blood flukes that infect an estimated 200 million people worldwide 1. In chronic infection with Schistosoma, the severe pathology, including liver fibrosis and splenomegaly, is caused by the immune response to the parasite eggs rather than the parasite itself 2. Parasite eggs induce a Th2 response characterized by the production of IL-4, IL-5 and IL-13, the alternative activation of macrophages and the recruitment of eosinophils. Here, we describe injection of Schistosoma mansoni eggs as a model to examine parasite-specific Th2 cytokine responses in the lung and draining lymph nodes, the formation of pulmonary granulomas surrounding the egg, and airway inflammation. 
Following intraperitoneal sensitization and intravenous challenge, S. mansoni eggs are transported to the lung via the pulmonary arteries where they are trapped within the lung parenchyma by granulomas composed of lymphocytes, eosinophils and alternatively activated macrophages 3-6. Associated with granuloma formation, inflammation in the broncho-alveolar spaces, expansion of the draining lymph nodes and CD4 T cell activation can be observed. Here we detail the protocol for isolating Schistosoma mansoni eggs from infected livers (modified from 7), sensitizing and challenging mice, and recovering the organs (broncho-alveolar lavage (BAL), lung and draining lymph nodes) for analysis. We also include representative histologic and immunologic data and suggestions for additional immunologic analysis. 
Overall, this method provides an in vivo model to investigate helminth-induced immunologic responses in the lung, which is broadly applicable to the study of Th2 inflammatory diseases including helminth infection, fibrotic diseases, allergic inflammation and asthma. Advantages of this model for the study of type 2 inflammation in the lung include the reproducibility of a potent Th2 inflammatory response in the lung and draining lymph nodes, the ease of assessment of inflammation by histologic examination of the granulomas surrounding the egg, and the potential for long-term storage of the parasite eggs.

Using Eggs from Schistosoma mansoni as an In vivo Model of Helminth-induced Lung Inflammation

Schistosoma mansoni eggs are potent stimulators of the T helper type 2 (Th2) immune response, characteristic of parasite infection, asthma and allergic inflammation. This protocol utilizes S. mansoni egg injection to generate a CD4 Th2 cytokine-induced inflammatory response in the lung, characterized by lung granuloma formation around the egg, eosinophilia and macrophage alternative activation.

Schistosoma parasites are blood flukes that infect an estimated 200 million people worldwide 1. In chronic infection with Schistosoma, the severe ...

Quantitative In vitro Assay to Measure Neutrophil Adhesion to Activated Primary Human Microvascular Endothelial Cells under Static Conditions

The vascular endothelium plays an integral part in the inflammatory response. During the acute phase of inflammation, endothelial cells (ECs) are activated by host mediators or directly by conserved microbial components or host-derived danger molecules. Activated ECs express cytokines, chemokines and adhesion molecules that mobilize, activate and retain leukocytes at the site of infection or injury. Neutrophils are the first leukocytes to arrive, and adhere to the endothelium through a variety of adhesion molecules present on the surfaces of both cells. The main functions of neutrophils are to directly eliminate microbial threats, promote the recruitment of other leukocytes through the release of additional factors, and initiate wound repair. Therefore, their recruitment and attachment to the endothelium is a critical step in the initiation of the inflammatory response. In this report, we describe an in vitro neutrophil adhesion assay using calcein AM-labeled primary human neutrophils to quantitate the extent of microvascular endothelial cell activation under static conditions. This method has the additional advantage that the same samples quantitated by fluorescence spectrophotometry can also be visualized directly using fluorescence microscopy for a more qualitative assessment of neutrophil binding.

Quantitative In vitro Assay to Measure Neutrophil Adhesion to Activated Primary Human Microvascular Endothelial Cells under Static Conditions

Neutrophil adherence to the activated endothelium at sites of infection is an integral component of the host's inflammatory response. Described in this report is a neutrophil binding assay that allows for the in vitro quantitation of primary human neutrophil binding to endothelial cells activated by inflammatory mediators under static conditions.

The vascular  endothelium plays an integral part in the inflammatory response. During the  acute phase of inflammation, endothelial cells (ECs) are ...

Cultivation of Heligmosomoides Polygyrus: An Immunomodulatory Nematode Parasite and its Secreted Products

Heligmosomoides polygyrus (formerly known as Nematospiroides dubius, and also referred to by some as H. bakeri) is a gastrointestinal helminth that employs multiple immunomodulatory mechanisms to establish chronic infection in mice and closely resembles prevalent human helminth infections. H. polygyrus has been studied extensively in the field of helminth-derived immune regulation and has been found to potently suppress experimental models of allergy and autoimmunity (both with active infection and isolated secreted products). The protocol described in this paper outlines management of the H. polygyrus life cycle for consistent production of L3 larvae, recovery of adult parasites, and collection of their excretory-secretory products (HES).

Cultivation of Heligmosomoides Polygyrus: An Immunomodulatory Nematode Parasite and its Secreted Products

Heligmosomoides polygyrus is a murine nematode with powerful immunomodulatory capabilities that closely resemble those of highly-prevalent human helminth infection. Here we describe a protocol for the long-term maintenance of the H. polygyrus lifecycle.

Heligmosomoides polygyrus (formerly known as Nematospiroides dubius, and also referred to by some as H. bakeri) is a gastrointestinal helminth that ...

Biolistic Transformation of a Fluorescent Tagged Gene into the Opportunistic Fungal Pathogen Cryptococcus neoformans

The basidiomycete Cryptococcus neoformans, an invasive opportunistic pathogen of the central nervous system, is the most frequent cause of fungal meningitis worldwide resulting in more than 625,000 deaths per year worldwide.&#160;Although electroporation has been developed for the transformation of plasmids in Cryptococcus, only&#160;biolistic&#160;delivery provides&#160;an effective means to transform&#160;linear&#160;DNA&#160;that can be integrated into the genome by homologous recombination.&#160;
Acetate has been shown to be a major fermentation product during cryptococcal infection, but the significance of this is not yet known.&#160;A bacterial pathway composed of the enzymes xylulose-5-phosphate/fructose-6-phosphate phosphoketolase (Xfp) and acetate kinase (Ack) is one of three potential pathways for acetate production in C. neoformans. Here, we demonstrate the biolistic transformation of a construct, which has the gene encoding Ack fused to the fluorescent tag mCherry, into&#160;C. neoformans. We then confirm integration of the ACK-mCherry fusion into the&#160;ACK&#160;locus.

Biolistic Transformation of a Fluorescent Tagged Gene into the Opportunistic Fungal Pathogen Cryptococcus neoformans

Biolistic transformation is a method used to generate stable integration of DNA into the genome of the opportunistic pathogen Cryptococcus neoformans through homologous recombination. We will demonstrate biolistic transformation of a construct, which has the gene encoding acetate kinase fused to the fluorescent tag mCherry into&#160;C. neoformans.

The basidiomycete Cryptococcus neoformans, an invasive opportunistic pathogen of the central nervous system, is the most frequent cause of fungal ...

Transformation of Probiotic Yeast and Their Recovery from Gastrointestinal Immune Tissues Following Oral Gavage in Mice

Development of recombinant oral therapy would allow for more direct targeting of the mucosal immune system and improve the ability to combat gastrointestinal disorders. Adapting probiotic yeast in particular for this approach carries several advantages. These strains have not only the potential to synthesize a wide variety of complex heterologous proteins but are also capable of surviving and protecting those proteins during transit through the intestine. Critically, however, this approach requires expertise in many diverse laboratory techniques not typically used in tandem. Furthermore, although individual protocols for yeast transformation are well characterized for commonly used laboratory strains, emphasis is placed here on alternative approaches and the importance of optimizing transformation for less well characterized probiotic strains. Detailing these methods will help facilitate discussion as to the best approaches for testing probiotic yeast as oral drug delivery vehicles and indeed serve to advance the development of this novel strategy for gastrointestinal therapy.

Presented here is a unified description of techniques that can be used to develop, transform, administer, and test heterologous protein expression of the probiotic yeast Saccharomyces boulardii.

Development of recombinant oral therapy would allow for more direct targeting of the mucosal immune system and improve the ability to combat ...

Measurement of In Vitro Integration Activity of HIV-1 Preintegration Complexes

HIV-1 envelope proteins engage cognate receptors on the target cell surface, which leads to viral-cell membrane fusion followed by the release of the viral capsid (CA) core into the cytoplasm. Subsequently, the viral Reverse Transcriptase (RT), as part of a namesake nucleoprotein complex termed the Reverse Transcription Complex (RTC), converts the viral single-stranded RNA genome into a double-stranded DNA copy (vDNA). This leads to the biogenesis of another nucleoprotein complex, termed the pre-integration complex (PIC), composed of the vDNA and associated virus proteins and host factors. The PIC-associated viral integrase (IN) orchestrates the integration of the vDNA into the host chromosomal DNA in a temporally and spatially regulated two-step process. First, the IN processes the 3&#39; ends of the vDNA in the cytoplasm and, second, after the PIC traffics to the nucleus, it mediates integration of the processed vDNA into the chromosomal DNA. The PICs isolated from target cells acutely infected with HIV-1 are functional in vitro, as they are competent to integrate the associated vDNA into an exogenously added heterologous target DNA. Such PIC-based in vitro integration assays have significantly contributed to delineating the mechanistic details of retroviral integration and to discovering IN inhibitors. In this report, we elaborate upon an updated HIV-1 PIC assay that employs a nested real-time quantitative Polymerase Chain Reaction (qPCR)-based strategy for measuring the in vitro integration activity of isolated native PICs.

Measurement of In Vitro Integration Activity of HIV-1 Preintegration Complexes

This report describes an in vitro assay for measuring the human immunodeficiency virus type 1 (HIV-1) preintegration complex (PIC)-associated integration activity in the cytoplasmic extracts of acutely infected cells. The integration of PIC-associated HIV-1 DNA into heterologous target DNA is quantified by using a nested real-time polymerase chain reaction strategy.

HIV-1 envelope proteins engage cognate receptors on the target cell surface, which leads to viral-cell membrane fusion followed by the release of the ...

In Vitro Methods for Comparing Target Binding and CDC Induction Between Therapeutic Antibodies: Applications in Biosimilarity Analysis

Therapeutic monoclonal antibodies (mAbs) are relevant to the treatment of different pathologies, including cancers. The development of biosimilar mAbs by pharmaceutical companies is a market opportunity, but it is also a strategy to increase drug accessibility and reduce therapy-associated costs. The protocols detailed here describe the evaluation of target binding and CDC induction by rituximab in Daudi cells. These two functions require different structural regions of the antibody and are relevant to the clinical effect induced by rituximab. The protocols allow the side-to-side comparison of a reference rituximab and a marketed rituximab biosimilar. The evaluated products showed differences both in target binding and CDC induction, suggesting that there are underlying physicochemical differences and highlighting the need to analyze the impact of those differences in the clinical setting. The methods reported here constitute simple and inexpensive in vitro models for the evaluation of the activity of rituximab biosimilars. Thus, they can be useful during biosimilar development, as well as for quality control in biosimilar production. Furthermore, the presented methods can be extrapolated to other therapeutic mAbs.

In Vitro Methods for Comparing Target Binding and CDC Induction Between Therapeutic Antibodies: Applications in Biosimilarity Analysis

This protocol describes the in vitro comparison of two key functional characteristics of rituximab: target binding and complement-dependent cytotoxicity (CDC) induction. The methods were employed for a side-to-side comparison between reference rituximab and a rituximab biosimilar. These assays can be employed during biosimilar development or as a quality control in their production.

Therapeutic monoclonal antibodies (mAbs) are relevant to the treatment of different pathologies, including cancers. The development of biosimilar mAbs by ...