Profiling Anti-Neu5Gc IgG in Human Sera with a Sialoglycan Microarray Assay

The overall goal of the sialoglycan microarray assay is to evaluate Anti-Neu5Gc IgG in human sera in a high-throughput manner against a diverse collection of sialoglycans. This method can help answer key questions in the glycoimmunology field, such as how Anti-Neu5Gc antibodies are involved with various human diseases including cancer, heart diseases, and xenotransplantation. The main advantage of this technique is that it allows high-throughput profiling of Anti-Neu5Gc antibodies against a myriad of sialoglycan antigens.

Demonstrating the procedure will be Sharon Yehuda, a master student from my laboratory. Careful and detailed planning of array fabrication and layout is important to ensure success. This process is detailed in the text protocol and the supplementary information.

Dilute each glycan to 100 micromolar in a total volume of 100 microliters of glycan printing buffer in microcentrifuge tubes. Next, prepare primary amine containing fluorescent dye to one milligram per millimeter with marker buffer. Then, dilute to one microgram per milliliter in a one milliliter total volume.

Prepare human IgG standard curve dilutions as described in the text protocol. Place the 384 well plate on ice. Using an electronic multi-pipette, aliquot seven microliters of each glycan, marker, and stardard curve IgG according to the plate layout found in the text protocol.

Cover the plate with parafilm and spin down for two minutes at 250 times g and 12 degrees Celsius. Printing must be carried out in dust-free area with a humidity of 60 to 70%Here, all steps are carried out in a clean room with appropriate gloves and clothing for protection. Turn on the nano printer machine and humidifier.

After programming the printing machine as described in the text protocol, position the 384 well plate with aliquoted samples into its location on the arrayer deck and remove the parafilm cover. At this point, start printing. Number the slides with an alcohol solvent-resistant marking pen, and store them in a vacuum-sealed box in the dark.

To process the arrays, first remove a slide from the vacuum-sealed box and place it in a chemical hood for five minutes, array facing up, to evaporate the excess liquid. Next, hydrate the slide by placing it it in a staining tube filled with deionized water. Cover the tube with foil and incubate for five minutes with slow and gentle shaking at room temperature.

To block the reactive epoxy groups on the slide, dip the slide into the 50 milliliter staining tube filled with pre-warmed ethanolamine blocking solution. Cover the tube with foil and incubate for 30 minutes with slow and gentle shaking at room temperature. Discard the ethanolamine blocking solution into the appropriate biohazard trash receptacle.

Then, place the slide in a new, clean staining tube filled with 50 degree celsius deionized water. Cover the tube with foil and incubate for 10 minutes with slow and gentle shaking at room temperature. Discard the water and transfer the slides to a glass staining holder.

Place the apparatus into a swinging plate holder and centrifuge the slide dry. Next, place the slide onto a 16-well divider. After pre-wetting the wells, use a multi-pipette to aliquot 200 microliters of PBST into the slide wells.

Then, place them in a covered, humid chamber and shake for five minutes. Remove the PBST by flicking and tapping gently on a clean paper towel. Then, aliquot 200 microliters of PBS-Ovalbumine blocking buffer into each well.

Place the slides in a humid chamber and incubate for one hour at room temperature with gentle shaking. Next, prepare the primary detection, diluted in PBS-OVA blocking buffer as described in the text protocol. Flick PBS-OVA blocking buffer off the slide and add 200 microliters of primary antibody per well.

Incubate the slides in a humid chamber for two hours. Then, flick the primary detection off the slide and wash three times with PBST. Incubate the slide in PBST for five minutes in a humid chamber before washing a final time with PBST.

Then, wash once with PBS. Next, prepare the secondary antibody in PBS as described in the text protocol. Flick the PBS off the slide and add 200 microliters of secondary antibody.

Flick the secondary antibody off the slide and wash four times with PBST as before. Carefully remove the frame, then place the slides into a 50 milliliter slide staining tube filled with PBS and shake for five minutes. Next, fill two slide staining baths with deionized water.

Place the slide into the slide holder and dip the slide into the first bath. Quickly dip the slide ten times. Then, transfer the slide to the second bath and dip ten more times.

After dipping, incubate the slide for ten minutes at room temperature with shaking. Following incubation, discard the water and transfer the slide to a glass staining holder. Place the glass staining holder in a swinging plate holder and centrifuge the slide dry.

Open the scanner door and place the slide inside, array facing down. At this point, start the scanning. Save the scanned slides as a TIFF file.

To prepare a slide for analysis, select Load Array List"and upload the appropriate GAL file that maps the arrays in each block on the slide. Slides were developed with 16 different primary detection moieties, one in each block. The plant Lectin SNA binds a2-6 linked sialic acid.

Whereas the plant Lectin MALII binds a2-3 linked sialic acid. Polyclonal Anti-Neu5Gc IgY binds Neu5Gc-containing sialoglycans but does not bind Neu5Ac-containing sialoglycans. To profile Anti-Neu5Gc IgG, 12 sera from healthy human donors were analyzed on the printed sialoglycan microarray and developed using fluorescently labeled anti-human IgG in normalized to nanograms per microliter.

All tested human sera contained various levels of Anti-Neu5Gc IgG with almost no recognition of the matched pairs of Neu5Ac-containing sialoglycans. Furthermore, Anti-Neu5Gc IgG recognition patterns are highly diverse between these 12 different sera, both in the level of intensity and diversity. After watching this video, you should have a good understanding of how to profile Anti-Neu5Gc antibodies in various human samples in a high-throughput manner, using a glycan microarray system.