A Vaccine Hero

Oct. 11, 2013

By Medical Discovery News

Despite the value of their work, scientists’ accomplishments don’t make them rich, and their talents generally don’t make them famous. For example, ever hear of Maurice R. Hilleman? Probably not, but most people are familiar with the measles, mumps, and rubella (MMR) vaccine he invented.

Hilleman may have saved more lives than any other scientist in the 20th century – he created or contributed to the development of more than 25 vaccines! Vaccines are designed to safely stimulate the immune system to develop resistance to diseases caused by viruses and bacteria.

About .1-.2 percent of children with measles, a highly contagious respiratory infection, die and an estimated 15-30 percent suffer complications like pneumonia. Hundreds of children died from measles every year even though the Food and Drug Administration had approved a measles vaccine in 1963. So Hilleman and a pediatrician named Joseph Stokes worked to minimize the significant side effects of the measles vaccine, which included fever and rash. They developed a scheme where children were injected with the vaccine in one arm and gamma globulin in the other. Gamma globulins are proteins extracted from blood that will temporarily stimulate the immune system. He eventually produced a much safer strain of measles virus called Moraten that is still used in today’s vaccines. But Hilleman did not stop there.

Like measles, mumps is also a viral infection, but it causes swelling of the parotid glands, the two largest salivary glands located in each cheek over the jaw and in front of the ears. Complications are not rare and include meningitis. Before the vaccine, mumps was one of the leading causes of childhood deafness. Mumps has also been reported to induce miscarriages in pregnant women. Hilleman started developing the mumps vaccine when his own daughter, Jeryl Lynn, developed mumps at age five. He isolated the virus from her, and named the vaccine strain derived from that virus after her.

Around 1963 there was a rubella outbreak in Europe. Another contagious viral infection, rubella is a usually mild disease that causes fever and rash in children and young adults, although it is less infectious and severe than measles. But rubella can cause birth defects if acquired by a pregnant woman. Up to 90 percent of infants born to mothers who had rubella during the first 11 weeks of pregnancy developed congenital rubella syndrome. This can cause growth retardation, cataracts, deafness, congenital heart defects, defects in other organs, and mental retardation. The highest risk to the fetus is during the first trimester, but exposure later in pregnancy also is dangerous. From 1963 to 1965, 11,000 babies died and another 20,000 developed birth defects due to rubella. Hilleman was responsible for refining the rubella vaccine and making it safe. At his request, an improved live rubella vaccine superseded his own. 

These three vaccines were combined to create the familiar MMR vaccine in 1971, which now has an added varicella vaccine to protect against chickenpox. Vaccination remains the most effective way to prevent diseases and their potentially serious effects.

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Aging But Still Protected

June 14, 2013

By Medical Discovery News

The people who are at the highest risk of dying from common infections like pneumonia, influenza, and colds are 50 and older. Traditionally, scientists believed that as we age, our immune systems weaken, leaving us more vulnerable than ever to infections. But new research suggests that this isn’t completely true – certain parts of the immune system remain fully functional and robust longer.

It is true that older people make fewer antibodies, proteins that attach to viruses and cells infected with viruses to mark them for elimination by the immune system. This explains why some vaccines aren’t as effective in the elderly. The flu vaccine, for example, contains a “dead” virus that stimulates the body to make more protective antibodies against the flu.

However, other vaccines are well-received in older people, like the varicella zoster virus vaccine that prevents shingles. This vaccine does not involve antibodies, but T-cells, which kill infected cells, and memory T-cells, which recognize and respond to a reinfection.

White blood cells, formally called leukocytes, represent an army ready to defend the body from bacterial or viral attacks. T-cells are one type of soldier in this army, responsible for cellular immunity – killing infected cells to protect the body. The thymus, located between the breast bone and heart, produces T-cells. But as people age, the thymus does too.

The thymus shrinks by about 3 percent a year during middle age, and there is a corresponding fall in the production of T-cells. As humans age, their T-cells increasingly become memory cells. Therefore, it’s been assumed that the T-cell response to kill cells infected with a virus is impaired in older adults, making them more susceptible to viral infections.

To test that assumption, researchers at the McMaster Immunology Research Centre in Ontario isolated blood from people with one of three types of viral infections: West Nile Virus, Epstein-Barr Virus, and Cytomegalovirus. They divided the patients into three groups: those under 40, those middle-aged (41 – 59), and those over 60. They then measured the amount, type, and activity of the T-cells in each group. The older group did indeed have a shift toward the production of memory T-cells. But surprisingly, the amount of virus-specific T-cells did not decrease with age – the older group had roughly the same amount as the middle and younger groups.

These results suggest that the thymus continues to play an important role in producing T-cells that target viral infections as we age. It also indicates that vaccines designed to stimulate cellular immunity, instead of antibodies, would be more effective in older people. So the flu vaccine might prevent more flu cases in older people if the dead virus was replaced with a live but weakened virus, but currently that’s not approved in the U.S. for people over 50.

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