The sera of Virginia opossum avoid toxic reactions to snake venom by containing compounds that block the key enzymes in the venom.

Pit viper venom is a complex mixture of various enzymes called metalloproteinases. These enzymes wreak havoc inside the bodies of venomous snake-bite victims by causing widespread breakdown of important proteins (proteolyisis) in the tissue surroundings blood vessels and within cells themselves. This damage results in hemorrhaging and the release of secondary toxins from injured tissue. Rapid death is often the outcome. The Virginia opossum is able to block the activity of metalloproteinase enzymes thereby neutralizing their toxic effects.

References

"Malayan pit viper (Calloselasma rhodostoma) envenomation is a major health problem in South East Asia. During envenomation, venom components mainly affect the hemostatic system [causing hemorrhage]. The sera from the North American Virginia opossums (Didelphis virginiana) were able to neutralize the venom of the Malayan pit viper." (Pornmanee et al. 2008:186)

"Hemorrhagins diffuse into the tissue, absorb on to vessels, and cause degradation of extracellular matrix and vascular basement membrane. The destruction of the vascular system can have a secondary effect of a quick release of other toxins (thrombin-like enzymes and procoagulants) into the circulation, which could cause coagulopathy problems." (Pornmanee et al. 2008:188)

"Opossums show no signs of edema, ecchymosis, or necrosis when bitten by venomous snakes. These animals are naturally resistant to the proteolytic effects of Crotalid venoms. They have metalloproteinase inhibitors in their sera that neutralize the hemorrhagic and other proteolytic activities caused by many snake venoms...According to a previous report, there was no evidence to support that opossums produce antibodies against venom molecules when immunized. Opossum serum contains metalloproteinase inhibitors which neutralize toxins from Crotalid venoms." (Pornmanee et al. 2008:187)

"Opossum sera were capable of neutralizing metalloproteinases from Malayan pit viper venom including hemorrhagins, fibrinogenases, and gelatinases... " (Pornmanee et al. 2008:188)

Journal article
Neutralization of lethality and proteolytic activities of Malayan pit viper (Calloselasma rhodostoma) venom with North American Virginia opossum (Didelphis virginiana) serum.

Magazine article
Chemical Arms Race: Opossum vs. Viper


Chemical arms race: opossum vs. viper

Organism
Virginia OpossumDidelphis virginianaSpecies