Will a female birth control vaccine work?
Bangalore |Sunday, 2011 2:35:05 PM IST
A birth control vaccine will not become a reality in the near future despite the high hopes of the Indian government, predicts a leading researcher at the Indian Institute of Science (IISc) here. But another researcher says a vaccine for women could hold out hope.
"Almost a quarter century after the idea was considered and after investment of resources and efforts of several competent teams, we are nowhere near the actual use of the proposed vaccines," says A. Jagannatha Rao, once at the forefront of contraceptive research.
None of the vaccines proposed by scientists actually met the requirements for use as a contraceptive vaccine for human application and "one may conclude that immuno-contraception (birth control vaccine) has no place in fertility control," he said in a report in the journal Current Science.
According to Rao, at least three types of vaccines for women and two for men were being developed and tested in laboratories in India, none of which reached a stage for actual use.
The only promising vaccine for males was one based on Follicle Stimulating Hormone (FSH) which is necessary for production of spermatozoa.
Interfering with the action of FSH appeared to be a feasible method of contraception and pioneering studies at the IISc in the 1990s showed that the FSH vaccine worked in male volunteers by eliciting specific antibodies against the hormone.
However, this vaccine failed to make the grade as the immune response in all subjects was not uniform, Rao said.
The only vaccine that showed promise for use in females that came out of Indian studies was the one based on the 'beta subunit' of the hormone hCG (human chorionic gonadotropin) developed by G.P. Talwar at the All India Institute of Medical Sciences (AIIMS) in the 1980s, he added.
According to Rao, the trials on 162 women showed it to be highly effective in preventing conception but had one major problem: only 119, or 80 percent, of the vaccinated women produced antibodies above the minimum level needed to stop pregnancy and the remaining 20 percent did not produce sufficient antibodies.
Another problem was the need for periodic injections to maintain required level of antibodies, he said.
A birth control vaccine in order to be accepted for the family planning programme must be 100 percent effective in all the subjects, he said.
On this count, he told IANS, none of the vaccines developed in India had fared well.
He said some more candidate vaccines have been suggested "but most of them are at the laboratory stage and we still have a long way to go before any of them see the light of the day", he concluded in his report.
Talwar, 85, however, is hopeful that his vaccine will be in market during his lifetime. "We have now developed the hCG vaccine using recombinant technology and a new adjuvant which demonstrates improved immunogenecity," he told IANS.
"Every mouse given this vaccine makes a high amount of antibodies."
This vaccine, he said, has received the approval of the National Review Committee on Genetic Manipulation and is being produced under GMP conditions for toxicology studies.
"If found safe, it is planned to conduct clinical trials with this vaccine for preventing pregnancy, as well as for its possible therapeutic action on those types of cancers which express hCG."
Rao said the problem is that unlike vaccines for diseases like malaria or tuberculosis that target disease-causing organisms, the birth control vaccine is for use in healthy subjects and should not interfere with normal physiological processes.
A vaccine based on Gonadotropin Releasing Hormone (GnRH) showed promise as a contraceptive vaccine in tests in rodents and monkeys.
However it "suppressed secondary sexual characters and behaviour" and thereby failed "to meet the important requirement to be specific, safe and effective vaccine".
Another contraceptive vaccine for women that was the focus of research at New Delhi's National Institute of Immunology was based on "Zona pellucida (ZP) glycoprotein".
This protein which is present in the female egg (ovum) plays a very important role during fertilisation.
Rao said the prospect of using ZP glycoprotein as a contraceptive vaccine "is not there in the near future as its safety is yet to be established in an unambiguous manner".
In vaccines for the male, efforts over the last 40 years focussed on developing a contraceptive vaccine that does not interfere with levels of testosterone -- the male hormone, inhibition of whose production can affect libido "which is completely unacceptable", Rao said.
(Killugudi Jayaraman can be contacted at email@example.com)
--Indo-Asian News Service kj/skb/pg/ky
( 766 Words)
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