Monoclonal antibodies against loggerhead sea turtle, Caretta caretta, IgY isoforms reveal differential contributions to antibody titers and relatedness among other sea turtles

Quantifying Circulating IgY Antibody Responses against Select Opportunistic Bacterial Pathogens and Correlations with Body Condition Factors in Wild American Alligators, Alligator mississippiensis

Simple Summary

Immunoglobulin Y (IgY) was purified from American alligator, Alligator mississippiensis, serum and used to develop a monoclonal antibody (mAb AMY-9) specific for the heavy chains of IgY. This antibody tool was then used to develop an ELISA for quantifying serum antibody responses against whole bacterial pathogens in alligators sampled in Florida, USA and South Carolina, USA. Antibody responses against some of the bacteria were very robust and varied by location and year, and in general these antibody responses correlated well with body condition factors, such as body-mass-indices (BMI). A novel mAb is now available to the scientific community interested in disease ecology of alligators.

Abstract

Little is known about the disease ecology of American alligators (Alligator mississippiensis), and especially how they respond immunologically to emerging infectious diseases and zoonotic pathogens. In this study, we examined serum samples collected from wild alligators in Florida (2010–2011) and South Carolina (2011–2012, 2014–2017) for antibody responses to multiple bacteria. Immunoglobulin Y (IgY) was purified from serum to generate a mouse monoclonal antibody (mAb AMY-9) specific to the IgY heavy chain. An indirect ELISA was then developed for quantifying antibody responses against whole cell Escherichia coli,Vibrio parahaemolyticus, Vibrio vulnificus, Mycobacterium fortuitum, Erysipelothrix rhusiopthiae, and Streptococcus agalactiae. In Florida samples the primary differences in antibody levels were between January–March and late spring through summer and early fall (May-October), most likely reflecting seasonal influences in immune responses. Of note, differences over the months in antibody responses were confined to M. fortuitum, E. rhusiopthiae, V. vulnificus, and E. coli. Robust antibody responses in SC samples were observed in 2011, 2014, and 2015 against each bacterium except E. coli. All antibody responses were low in 2016 and 2017. Some of the highest antibody responses were against V. parahaemolyticus, M. fortuitum, and E. rhusiopthiae. One SC alligator estimated to be 70+ years old exhibited the highest measured antibody response against V. parahaemolyticus and M. fortuitum. By combining data from both sites, we show a clear correlation between body-mass-indices (BMI) and antibody titers in all six of the bacteria examined. Our study provides a critical antibody reagent and a proof-of-concept approach for studying the disease ecology of alligators in both the wild and in captivity.

The Use of Bacteriophages and Immunological Monitoring for the Treatment of a Case of Chronic Septicemic Cutaneous Ulcerative Disease in a Loggerhead Sea Turtle Caretta caretta

In this case study, phage therapy was applied to treat a multidrug-resistant case of septicemic cutaneous ulcerative disease (SCUD) caused by Citrobacter freundii in a loggerhead sea turtle Caretta caretta. Phages were applied topically, intravenously, into the carapace, and into the exhibit water using various phage cocktails specific to the causative agent over an 8-month period. This was performed in conjunction with antimicrobial therapy. The animal was monitored through weekly cultures, photographs, and complete blood cell counts, as well as immune assays (phagocytosis, plasma lysozyme and superoxide dismutase activity, and plasma electrophoresis profiles). The animal, in comparison to an untreated, unaffected control, had elevated antibody titers to the administered phages, which persisted for at least 35 weeks. Although cultures were clear of C. freundii after phage treatment, the infection did return over time and immune assays confirmed deficiencies when compared to a healthy loggerhead sea turtle. Immune parameters with statistically significant changes over the study period included the following: decreased phagocytosis, increased alpha- and gamma-globulin protein components, and an increased albumin : globulin ratio. When C. freundii appeared again, the multidrug-resistant status had reverted back to normal susceptibility patterns. Although not completely known whether it was another subspecies of bacteria, the therapy did resolve the multidrug-resistant challenge. Phage therapy in combination with antimicrobial agents may be an effective treatment for sea turtles with normally functioning immune systems or less-severe infections. Additional research is needed to better understand and quantify sea turtle immunology.