The work of a leading Irish pathologist which formed a key element in the purported link between autism and the MMR vaccine has been heavily criticised in a US court.
The criticism emerged as Dr Andrew Wakefield, the doctor who first proposed a link between autism and the MMR vaccine, begins his defence against allegations of professional misconduct in Britain.
Prof John O'Leary, professor of pathology at Trinity College Dublin, carried out research in a laboratory at the Coombe hospital confirming the presence of the measles virus in gut biopsies of children with autism.
However, last month, the US Court of Federal Claims in Washington was told by an expert witness, Prof Stephen Bustin: "I do not believe there is any measles virus in any of the cases they [Prof O'Leary's research team] have looked at".
Prof Bustin, a professor of molecular science at Queen Mary's School of Medicine and Dentistry, University of London, and a world expert in the technology of polymerase chain reaction (PCR) - the basis for many medical diagnostic tests - reached his conclusion after visiting the laboratory at the Coombe hospital in 2004 and following a series of studies which failed to replicate Prof O'Leary's results. He was giving evidence in the first test case brought by the families of more than 4,800 US children claiming damages from a fund set up to compensate people harmed by vaccination.
Prof Bustin told the court, it was "a scientific certainty" that the Unigenetics laboratory at the Coombe has failed to identify measles virus RNA (genetic material) in the children it had tested.
Introduced as the author of the "bible of PCR", he told the three judge court: "I have very little doubt that what they [Prof O'Leary and his colleagues] are detecting is a DNA contaminant and not measles virus, and I do not believe there is any measles virus in any of the cases they have looked at".
Prof Bustin's opinion is widely regarded as final proof that the theory put forward by British gastroenterologist, Dr Andrew Wakefield, that a distinctive inflammatory bowel condition - autistic enterocolitis - was the link between the MMR vaccine and increasing levels of autism, lacks credibility.
Dr Wakefield published research in the Lancetmedical journal in 1998 describing how he had detected measles virus in the bowels of 12 children with autism. This led to a sharp drop in the uptake of the MMR vaccine worldwide and a rise in the number of children infected with measles both here and in the UK.
The General Medical Council in London last week began fitness to practise hearings into the professional conduct of Dr Wakefield and two of his co-authors.
Prof Bustin told the court that "the assay used was not specific for measles and it was not properly carried out". He said that the positive result were positive for DNA and as measles is an RNA virus, "if it's DNA it can't be measles". The expert said he suspected that the unigenetics laboratory has been contaminated by DNA from another source. Unigenetics, a private company, is reported to have been paid some stg£800,000 by the UK legal aid fund.
Dr Michael Fitzpatrick, a London GP and author of MMR and Autism: What parents need to knowtold The Irish Timesthat "Bustin's evidence blows out of the water the only single shred of evidence which seemed to prove a link between MMR and autism".
Prof O'Leary was unavailable for comment yesterday. He has strongly disputed the claim that contamination might have occurred in his laboratory. He has said he never set out to prove that MMR caused autism. In addition, he has publicly urged parents to vaccinate children with the combined MMR vaccine.