Molecular identification of interleukin-2 in the lymphoid tissues of the common brushtail possum, Trichosurus vulpecula

The common brushtail possum (Trichosurus vulpecula) is an Australian marsupial. Here we describe the identification of possum interleukin-2 in mitogen-stimulated lymph node cells. We used a strategy of Rapid amplification of cDNA ends using probes designed from recently-sequenced marsupial genomes to identify the IL2 gene and then confirmed that IL-2 expression in possum immune tissue occurs in a similar manner to that in their eutherian counterparts. The predictive possum IL-2 peptide showed 28% and 35% amino acid sequence homology with the mouse and human IL-2 molecules, respectively, consistent with the divergence found within this cytokine family. Despite this low sequence identity, possum IL-2 still possessed the characteristic hallmarks of mammalian IL-2, such as a predicted signal peptide and conserved family motifs.

Uterine and vaginal insemination optimised in brushtail possums (Trichosurus vulpecula) superovulated with pregnant mare serum gonadotrophin and porcine luteinising hormone

Artificial insemination of brushtail possums (Trichosurus vulpecula) is being developed as an assisted breeding model for endangered marsupials, as well as a bioassay for testing fertility control vaccines to manage overabundant populations. Procedures were optimised in animals superovulated with pregnant mare serum gonadotrophin (PMSG) and porcine luteinising hormone (pLH). Of three intervals examined, yields were maximal following uterine insemination at 27–29.5 h after pLH treatment (four eggs, two to three embryos per female). Compared with no insemination, uterine-inseminated animals ovulated 30–36 h rather than 28–34 h after pLH treatment. For the vaginal route, yields were maximal following insemination at 10–13 h after pLH treatment (six to seven eggs, four embryos per female) than at five other intervals, and when using acclimatised females during the autumn breeding season. This protocol was suitable for testing fertility control vaccines in April–June and was influenced by the housing location of animals, the presence of an active corpus luteum and PMSG batch, but not other factors (year of trial, Freund’s adjuvant treatment, changes in bodyweight, dose of PMSG kg–1). Embryos developed to the eight- to 16-cell or unilaminar blastocyst stage after uterine or vaginal insemination, respectively. With the timing of artificial insemination optimised, new methods to synchronise or induce oestrus and ovulation are required to achieve year-round testing of fertility control vaccines or birth of offspring.

208.Zona pellucida vaccines for fertility control of brushtail possums in New Zealand

Introduced marsupial brushtail possums (Trichosurus vulpecula) are a major pest in New Zealand because of their impacts on conservation values and agricultural production. Immunologically-based fertility control (immunocontraception) offers an effective and humane alternative approach to possum management. The zona pellucida (ZP) is an extracellular coat around all mammalian eggs and an attractive target for the development of immunocontraceptive vaccines. Antibodies against ZP are ovary-specific and act by preventing sperm from binding and penetrating the ova and/or by disrupting the development of follicles or early embryo. The aim of these studies was to test the efficacy of possum-derived ZP antigens for their ability to elicit sustained immune responses and cause infertility, and to assess a range of options for development of a bait-delivered contraceptive vaccine. Alloimmunisation with possum ZP2 and ZP3 proteins showed that self-ZP antigens elicited strong humoral immune responses and reduced the fertility of female possums by 72-80%. Several potentially possum-specific immunocontraceptive peptides have been identified by linear epitope mapping and amino acid alignment and are being tested for their ability to reduce fertility. Recent trials have demonstrated that possums mount immune responses against ZP antigens delivered in transgenic plants and bacterial ghosts. Research on antigen and specific peptide identification, non-target effects and delivery systems is ongoing. Research supported by NZ Foundation for�Research Science & Technology, Marsupial CRC and NZ Animal Health Board.

Humoral immunity to cholera toxin and ovalbumin in the brushtail possum (Trichosurus vulpecula)

AIM

To compare the humoral immune responses of female possums to ovalbumin (OVA) and cholera toxin (CT) administered using different routes and dosage regimes.

METHODS

Three groups of mature female possums were immunised intragastrically (n=15) or surgically (intraileal, n=4; Peyer's patches, n=4). Levels of antibodies to OVA and CT in serum, ileal, vaginal, oviduct and uterine secretions were measured by indirect enzyme-linked immunosorbent assay (ELISA). All manipulations were conducted under general anaesthesia.

RESULTS

Antibodies to CT increased significantly in serum (p<0.001) and in lateral vaginal secretions (p<0.05) after intragastric immunisation using 250-1000 microg CT. Simultaneous intragastric administration of CT with 3 mg OVA did not significantly increase antibody levels to OVA. When OVA (3 mg) and CT (250 microg) were injected into the ileum, followed by intragastric administration 4 weeks later, antibody levels to CT were significantly (p<0.05) increased in serum, uterine and medial vaginal secretions, and antibody levels to OVA were significantly (p<0.05) increased in serum and medial vaginal secretions. When OVA (3 mg) with Incomplete Freund's adjuvant was injected directly into Peyer's patches, followed by peritoneal administration 4 weeks later, antibody levels in serum, ileal and reproductive-tract secretions were generally higher than those that resulted from the other immunisation treatments.

CONCLUSIONS

Administration of OVA induced an antibody response in serum and in reproductive and alimentary tract secretions when administered with CT directly into the ileum, or when injected into Peyer's patches and peritoneum. CT was a potent enteric immunogen.

Fertility of brushtail possums (Trichosurus vulpecula) immunised against sperm

The brushtail possum (Trichosurus vulpecula) is a major pest species in New Zealand. Research to develop a possum-specific method of immunologically-based fertility control (immunocontraception) has begun. This study examined the effect of immunization against sperm on the fertility of possums. Possums were assigned to 16 mating groups (two females and one male per group) before the start of the breeding season. One female in each group and eight males were injected subcutaneously with 5 x 10(7) sperm in complete Freund's adjuvant. Animals were given booster injections containing 5 x 10(7) sperm in incomplete Freund's adjuvant 4 and 12 weeks later. Control animals received adjuvants emulsified with phosphate buffered saline. Serum and sperm samples were collected monthly and the number of offspring recorded. Reproductive tract samples were collected from eight immunized and eight control possums of each sex at the end of the breeding season. Samples were screened for sperm antibody binding by an indirect possum sperm ELISA. Increased sperm antibody binding was detected in sera of 22 (15 females and seven males) of the 24 animals immunized against sperm. Immunization significantly reduced the proportion of females producing offspring (2/16 immunized versus 12/16 control) but had no effect on the fertility of males. Immunization increased sperm antibody binding activity in vaginal secretions of female and in prostatic tissue of male possums. Results indicate that there are antigens in possum sperm with immunocontraceptive potential for possum control.

Determination of oestrus and mating in captive female brushtail possums, Trichosurus vulpecula (Marsupialia : Phalangeridae), from urine samples

Reproductive data were collected from captive brushtail possums, Trichosurus vulpecula, by examining daily urine samples for the presence of non-keratinised and keratinised epithelial cells, polymorphonuclear leucocytes, and sperm. Around the time of oestrus there was a massive increase in the number of epithelial cells and leucocytes in urine. The pattern of cell shedding was similar in mated and non-mated females undergoing either spontaneous ovulations or those induced by removal of pouch young. There was no difference between fertile or non-fertile oestrous cycles. During the 2-month sampling period, 97% of females showed changes in cell numbers indicative of oestrus and 72% of females were confirmed to have been mated by the presence of sperm. Conception rate was 74% and offspring were born 16–19 days after mating. When pouch young were removed, 85% of females were mated 7–15 days later and 77% of mated females produced pouch young. Compared with vaginal smears, collection and examination of urine was easier and faster, only one animal handler was required, the method was less stressful for the possum, and cell types in the sample were scored directly without the need for fixation and staining.