Incubation of different volumes of serum from the Komodo dragon (<i>Varanus komodoensis</i>) with sheep red blood cells (SRBCs) resulted in volume-dependent hemolysis, as measured spectrophotometrically at 540 nm. The hemolysis occurred rapidly, with almost 90% of the hemolytic activity occurring within 20 min of incubation. A thermal profile showed that Komodo dragon serum exhibited low activity from 5- 20℃, but exerted maximum activity at 35℃, which was substantially reduced at 40℃. The maximum activity was observed near optimal temperatures to which Komodo dragons thermoregulate. Mild heat treatment of Komodo dragon serum (56℃, 30 min) depleted the ability to hemolyze SRBCs. In addition, preincubation of Komodo dragon serum with only 5 mM EDTA or phosphate, both chelators of divalent metal ions, reduced the hemolytic activity sharply. These results indicate that the hemolytic activity was due to the presence of a potent serum complement system. Incubation of Komodo dragon serum with 5 mM EDTA and 15 mM Ca²⁺ or Mg²⁺, but not Ba²⁺, Zn²⁺, or Fe²⁺, completely restored activity. These results indicate that Komodo dragon serum complement activity requires the presence of Mg²⁺ or Ca²⁺. This is the first assessment of innate immune activity of a Varanid

Komodo dragons (Varanus komodoensis) are able to feed on large prey items by injecting a dose of toxic bacteria with their bite that, over time, kills the prey by systemic infection. Dragons also suffer bites from other members of their own species during territorial disputes and feeding frenzies. However, they do not suffer the same fate as their prey, suggesting that they have developed a strong immunity to bacterial infections. This study was undertaken to determine the antibacterial activities of serum from the Komodo dragon. Bacterial cultures were treated with different volumes serum from Varanus komodoensis and the growth was monitored by optical density at 430 nm. In addition, the serum was treated with protease, chelators of divalent metal ions, or with mild heat to determine the mechanism of antibacterial activities. Treatment of bacterial cultures with serum from Komodo dragons (Varanus komodoensis) resulted in a volume-dependent decrease in bacterial growth. Cultures of Escherichia coli, Staphylococcus aureus, and Klebsiella oxytoca exhibited moderate-strong growth inhibition by V. komodoensis serum, while cultures of Streptococcus epidermitis, Salmonella typhimurium, Providencia stuartii, and Shigella flexneri were nearly completely obliterated for 24 h by only 10% (v/v) serum. The antibacterial activity of V. komodensis serum occurred very rapidly, as 18% of E. coli growth was inhibited by a five min exposure to serum. Furthermore, 10- and 20-min incubations of E. coli with serum from V. komodoensis resulted in 43 and 68% inhibition of bacterial growth, respectively. The bactericidal capacity of the serum against E. coli was 2,075,000 bacteria/μL serum, and was inhibited by mild heat treatment, pronase, EDTA, and phosphate, indicating that the anti-bacterial action is most probably due to the presence of a potent serum complement protein system

Aims: Soluble serum dipeptidyl peptidase IV (DPPIV) is a protease that cleaves dipeptides from proteins that have alanine or proline next to the N-terminal amino acid. This enzyme demonstrates substantial immune function by regulating T-lymphocyte activity, T-cell chemotaxis, growth, and proliferation during an inflammatory response. The goal of this study was to characterize DPPIV activity in the serum of the Komodo dragon (Varanus komodoensis). Study design: Place and Duration of Study: Serum was collected from eight Komodo dragons at the San Antonio Zoo (n = 5) and Houston Zoo (n = 3) in June of 2012. The samples were analyzed for DPPIV enzyme activity in the Department of Chemistry at McNeese State University in Lake Charles, Louisiana, USA Methodology: We used Ala-Pro-AFC, a dipeptide conjugated to a fluorescent probe via an amide linkage, to measure the activity of DPPIV in the serum of Komodo dragons (Varanus komodoensis). The fluorescent intensity of the product formed was measured at excitation and emission wavelengths of 395 and 530 nm, respectively, in a fluorimeter. Results: Incubation of different volumes of serum from the Komodo dragon with Ala-Pro-AFC resulted in a volume-dependent increase in fluorescent intensity, which was decreased in a concentration-dependent manner by diprotin A, a specific inhibitor of DPPIV activity. Kinetic analysis showed that the DPPIV enzyme activity was detectable after five minutes, and that was nearly linear for three hours. A thermal profile showed that Komodo dragon DPPIV exhibited dramatically reduced activities at low temperatures (5-10 o C), but activity increased linearly with temperature and was maximal at the highest temperature tested (40 o C). Conclusion: These results from this study indicate that Komodo dragons exhibit considerably high serum DPPIV activities, which are likely to contribute to T-cell activation and function, and act as a bridge between innate and adaptive immunity in these ancient vertebrates.

(sPLA2) is an enzyme found in the peripheral circulation of vertebrates which has significant immunological activity. This enzyme exerts immune activity by the hydrolysis of fatty acids from the sn-2 position of membrane glycerophospholipids of microbes, thus compromising membrane integrity and casing eventual lysis. We utilized membrane fatty acids labeled with a fluorescent probe (BODIPY) at the sn-2 position fatty acid to label the membranes. Incubation of different volumes of serum from Komodo dragons with BODIPY-labeled bacteria resulted in liberation of labeled fatty acid in a serum volume-dependent manner. This cleavage of fatty acid occurred rapidly, with a biphasic production of fluorescent product. An immediate accumulation of product was noted, which increased steadily for a 30-minute period, followed by a slower hydrolysis between 30 and 180 min. The activity was temperature-dependent, with low activities observed at 5 o C and a linear increase up to 40 o C. The liberation for fatty acid was inhibited by p-Bromo phenacyl bromide, a specific phospholipase A2 (PLA2) inhibitor, in a concentration-dependent manner, indicating that the activity was due to the presence of sPLA2.