A new method of contraception for men (search) may be one step closer to reality, according to a study in the Nov. 12 issue of the journal Science.

Currently, men have two contraceptive options -- vasectomy (search) and condoms -- and scientists are also working on developing hormonal contraception for men.

The new study takes a different approach, using immunization -- not hormones -- to make male monkeys temporarily infertile.

The technique, called immunocontraception (search), “may be extended to humans,” write the researchers, who include Michael O’Rand, PhD, a professor in the cell and developmental biology department at the University of North Carolina, Chapel Hill, medical school.

O’Rand and colleagues immunized nine adult male monkeys with a solution containing a protein called Eppin (search), which comes from the testes. As a result, seven monkeys developed a strong antibody response against the Eppin protein, making them infertile.

The immunized monkeys were then paired with three fertile female monkeys to mate. No pregnancies resulted.

The researchers say testosterone levels in the immunized group were no different from non-immunized monkeys and the treatment had no effect on sperm count.

They also show that the immunocontraception technique was reversible in most monkeys. After the immunization treatment stopped, five of the seven monkeys regained their fertility.

The researchers say immunocontraception may work by hampering Eppin’s ability to interact with a substance in the seminal fluid that carries sperm.

Immunocontraception is not a new idea. However, until now, scientists focused on it as a possible way to immunize females to prevent pregnancy or fertilization.

“This study demonstrates that effective and reversible male [immunocontraception] in primates is an attainable goal,” write O’Rand and colleagues.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: O’Rand, M. Science, Nov. 12, 2004; vol 306: pp 1189-1190.