Histomonas meleagridis (Parabasala, Trichomonadea, Monocercomonadidae): presence of natural agglutinins in horse serum.

This research article details a scientific investigation into the interaction between the cells of a single-celled parasite (Histomonas meleagridis) and horse serum, demonstrating a noteworthy ability of the latter to cause agglutination or clumping of the former, a phenomenon that was dependent on the time and concentration of the serum used.

Methodology

• The research team working on this study started by culturing Histomonas meleagridis cells. These are parasitic cells that affect poultry.
• The cultured cells were then subjected to agglutination tests in vitro (under laboratory conditions) using horse serum. The horse serum was applied at different concentrations, starting as low as 5%, with the researchers noting that even at this low concentration, the serum still caused the cells to clump together or agglutinate.
• The cells underwent a washing process using Hanks balanced solution (HBSS) and were then filtered through glass wool. This was done to ensure the cells were clean before the horse sera were added.
• The clump formation was observed and recorded, with the researchers indicating that the process was time- and concentration-dependent – meaning that the duration and degree of clumping increased with time and with the increasing concentration of the horse serum.

Observations and Findings

• The research team found that agitation—a form of mild disturbance—had different effects depending on the concentration of the serum. At lower serum concentrations, agitation was found to hinder the agglutination process; on the contrary, at higher concentrations, it accelerated the process.
• The researchers tested sera from various sources and found that the agglutination factor (AF) was present in several batches regardless of whether or not these sera had been heat-treated to inactivate any potential complement (a part of the immune system).
• Neither fetal horse serum nor bovine serum (from cows) were found to cause clumping of the histomonads. Similarly, chicken or turkey serum did not show the same level of agglutination as the horse serum.

Conclusions and Applications

• A notable finding from the study was that immune turkey serum caused the histomonads to lyse or break down, which made the observation of clumping challenging. The breakdown of the cells was only slightly reduced when the serum’s complement was inactivated.
• The researchers found they could precipitate the AF in horse serum by utilizing ammonium sulfate, after which the AF remained active even after being cleaned by dialysis and reconstituted in HBSS.
• The agglutination or clumping effect demonstrated by the horse serum was beneficial for the researchers’ additional studies, as it aided in clean separation of the Histomonas meleagridis cells where pure suspensions were required.