UTS brings in American to head infectious disease institute

The University of Technology, Sydney (UTS) has appointed eminent American parasitologist Prof Michael Wallach as director of its new Institute for the Biotechnology of Infectious Diseases.

The university's prize recruit is fresh from a coup of his own: Wallach headed the successful international project to develop a genetically engineered vaccine against one of the poultry industry's most devastating diseases, coccidiosis.

Coccidiosis, caused by the tiny intestinal parasite Eimeria, is a major economic problem for the poultry industry. Infected birds develop diarrhoea and anaemia, and eventually die.

The vaccine is the first genetically engineered, sub-unit vaccine against an apicomplexan parasite. Apicomplexans are a diverse group of amoeba-like blood and intestinal parasites of vertebrates, including human, livestock and fish.

Conventional vaccines are available for several apicomplexan diseases. Wallach plans to develop a major program at the Institute to develop sub-unit vaccines against other members of the apicomplexan rogues' gallery, including:

• Plasmodium, the deadly agent of malaria in humans.
• Cryptosporidium, one of the diarrhoea-causing agents of Sydney's pre-Olympic water contamination scare.
• Toxoplasma, which causes abortion in humans and livestock, and deadly opportunistic infections in AIDS patients.
• Babesia, the agent of cause of tick fever in cattle.
• Neospora, another cause of abortion in cattle.

"Apicomplexans are genetically more complex than bacteria, and very challenging subjects for vaccine development," Wallach said.

"They're genetically plastic, and have a great ability to evade the host's immune response -- they disguise themselves by constantly changing their antigens."

Wallach led the collaboration between UTS and Israeli researchers to develop the Eimeria vaccine.

The new coccidiosis vaccine confirms the feasibility of vaccinating hens to induce antibody production in the yolk of their eggs, protecting hatchlings against infection during the early weeks of life.

Wallach said that by the time maternal antibody protection wanes, chickens raised for meat are ready for market. Chickens begin laying at around 20 weeks, and continue for another 30 weeks, so vaccinating a breeding hen that produces five or six eggs weekly should protect at least 150 chickens.

For egg-producing poultry, the vaccine acts as a shield during early growth, giving the chicken's own immune system time to mature and mount its own defence against Eimeria.

The vaccine does not confer complete protection -- Wallach said such an outcome would not be desirable, because exposure to Eimeria stimulated a protective immune response in chickens raised to produce eggs. The birds remained healthy when protection from the maternal antibodies waned.

Assoc Prof Ian Smith, of UTS, said he believed the new coccidiosis vaccine would have a "revolutionary impact" on the poultry industry, by allowing it to dispense with antibiotics that have been used in formulated feeds as growth promoters.

Constant exposure to antibiotics is suspected to have led to the emergence of antibiotic-resistance genes in the commensal gut bacteria of poultry and other livestock species.

Microbial geneticists have produced strong evidence that resistance genes have then been transferred to human gut bacteria, through the food supply. The end-result is multi-resistant strains of "hospital bacteria" that cause chronic, even lethal infections in surgery patients.

Wallach said the new sub-unit vaccine against Eimeria induced an antibody response against several proteins that form the tough cell wall of the oocysts.

By disrupting the final stage of the parasite's complex life cycle, it prevents the formation of dormant oocysts that can survive outside the bird's body to perpetuate the infection cycle.