Abstract

The immunoglobulin, IgG, was isolated from the pooled sera of Northern elephant seals (Mirounga angustirostris). Purity was evaluated by immunoelectrophoersis and 2.0 mgms were labelled with 125-1. The half-life (T-1/2) in one Northern elephant seal was 9.987 days. The potential use of gammaglobulin as interim therapy in marine mammals is discussed.

Introduction

Infectious diseases in captive marine mammals have been well-documented (1) and there is suggestive evidence, both serologically and by direct isolation, that microbial pathogens constantly challenge feral animals in their natural environment (2,3). Currently, only Erysipelothrix bacterin is given routinely to cetaceans and two experimental vaccines for Pasturella multocida (4) and Pseudomonas pseudomallei (5) are being evaluated.

The purpose of the present study was to determine the metabolism of immunoglobulin IgG in marine pinnipeds. A preliminary report is presented on the IgG half-life in one Northern elephant seal. The potential use of gammaglobulin as an interim therapy is discussed.

Materials and Methods

The IgG was isolated from the pooled sera of 4 Northern elephant seals by AFFI-Gel Blue column chromatography (6). The purity of the preparation was determined by immunoelectrophoresis against rabbit anti-whole elephant seal sera. Two mgms IgG were labelled with I mCi of 125-1 (New England Nuclear) by the Chloramine-T method (7). Labelling efficiency (96%) was determined by the trichloracetic acid method. The final volume injected into the animals was 13.3 ml.

One Northern elephant seal (wt.= 224 lbs) was pre-bled, injected I.V. with the labelled IgG, and bled periodically for 14 days. All blood was collected in heparinized tubes and 0.5 ml of plasma used to determine radioactive counts in a gamma counter.

Although some urine was collected and assayed, it was not possible to obtain total, daily urine samples.

Results

The 125-I - IgG decay curve is shown in Figure 1. The correlation coefficient was 0.995. Using the portion of the curve from 40-80 hrs and 80-280 hrs, the half-life (T-1/2 in days) was calculated to be 9.987 days and fraction catabolized per day, 0.069.

Discussion

In a previous study (8), the quantitative analysis of IgG was determined in Northern fur seals (Callorhinus ursinus) from birth to age 4 mos. It was estimated that the IgG absorbed through the gut rapidly disappeared between 3 and 20 days before the animal began to synthesize its own IgG. The results of the present study in one elephant seal agrees with this previous estimate. We are currently repeating the radiolabelled IgG metabolism in other elephant seals and harbor seals.

The use of gammaglobutin for interim therapy, however, requires that an appropriate level of antibody to selected pathogen(s) be determined. In a previous study (5) at Ocean Park, Hong Kong, 2 dolphins (Tursiops gilli) showed symptoms of P. pseudomallei infection. The IgG was purified from the sera of a dolphin that had previously died of melioidosis.

Assuming a blood volume of 10% body weight, the IgG preparation was adjusted to give a dosage of 2.0 ug AbN/ml final blood concentration. One animal was injected with the gammaglobulin and survived, whereas the other animal died. Although this observation was preliminary and in only one animal, it suggests that interim gammaglobulin therapy may be a viable compliment to other therapy, particularly in bacteremic diseases. We have found significant amounts of circulating antibodies to Salmonella enteritidis, Pasturella multocida, and Erysipelothrix rhusiopathiae in feral pinnipeds on San Miguel Island, California. Specific antibody levels to these pathogens will be determined in our globulin preparations and therapy will be initiated in several stranded animals.

References

1. Medway, W. Some bacterial and mycotic diseases of marine mammals. J. Am. Vet. Med. Assoc. 117: 831-834 (1980).
2. Vedros, N.A.; Quinlivan, J.; and Cranford, R. Bacterial and fungal flora of wild Northern fur seals (Callorhinus ursinus). J. Wildl. Dis. 18: 447-456 (1982).
3. Quinlivan, J.; Vedros, N.A.; and Smith, A.W. The use of Enzyme Linked Immunosorbant Assay (ELISA) in serosurveys for bacterial pathogens in feral marine pinnipeds. (to be published).
4. Vedros, N.A. A potential vaccine for Pasturella multocida infection in marine mammals. Proc. of 13th Annual Conf. of IAAAM, Baltimore, MD (1982).
5. Vedros, N.A. A potential Vaccine for malleoidosis is marine mammals. Proc. of 14th Annual Conf. of IAAAM, Los Angeles, CA (1983).
6. 6. Bio-Rad Laboratories, Bulletin 1062 (1983).
7. McConahey, P.J. and Dixon, F.J. A method for trace iodination of proteins for immunologic studies. Int. Arch. Allergy 29; 185 (1966).
8. Cavagnola, R.Z., and Vedros, N.A. Serum and colostrum levels in the northern fur seal (Callorhinus ursinus).Develop. and Compar. Immunol. 3: 139-146 (1979).