Archive for March, 2017

 

Mar 09 2017

An injection of optimism into biomedical research – Part 5: Millions of babies

by at 3:59 am

This is the fifth and last part of my Injection of Optimism into Biomedical Research Series. I’m getting back to the babies on this one! In Part 1, I talked about the success of newborn screening programs, here I will be discussing a prenatal public health intervention that has saved and helped millions of babies worldwide.

The Rh protein complex is embedded in the membranes of red blood cells. Most individuals are Rh positive (Rh+), which means that their Rh complex contains a specific protein (the RhD antigen); individuals without that protein are Rh negative (Rh-). Approximately 15% of Caucasians, 7% of blacks, and 1% of Asians are estimated to be Rh-. Blood types are generally denoted by a shorthand reporting the ABO blood group and Rh status.  For example, an individual who has an ABO blood group of B and is Rh- is often denoted as “B-.” The Rh type is inherited in a recessive manner, so that a child who is Rh- must have two Rh- parents, but a child who is Rh+ may have two Rh+ parents or one Rh+ and one Rh- parent.

Problems can result if an Rh- woman is pregnant and carrying an Rh+ baby. In that case, the woman’s body may create antibodies to the RhD protein in the baby’s blood. These antibodies can destroy the baby’s red blood cells, leading to severe anemia or even death. This is called “Rh incompatibility” and generally occurs after the first pregnancy, since the first baby is usually born before the development of too many antibodies. In 1960, Rh incompatibility and the resulting hemolytic disease of the newborn (erythoblastosis fetalis) was estimated to result in 10,000 stillborn babies and even more babies who were affected and generally expected to recover after blood transfusions. In 1968, two clinical trials showed that injection of the anti-Rh gamma globulin (RhoGAM) after the delivery of an Rh+ baby by an Rh- woman will prevent problems with later pregnancies. Women who are at risk of Rh incompatibility now generally receive the RhoGAM shot at 7 months and within 72 hours of delivery, as well as in the case of miscarriage or bleeding during pregnancy.

Given that Rh incompatibility used to lead to many cases of perinatal death and illness and is now a rare concern if the RhoGAM shot is appropriately administered, this is a major public health victory. I hope this series as a whole will help renew your optimism and sense of wonder in biomedical research and science in general. Now let me get back to writing that grant proposal…

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Mar 06 2017

An injection of optimism into biomedical research – Part 4: Cancer prevention and early detection

by at 4:13 pm

This is the fourth part  of my Injection of Optimism into Biomedical Research Series. Since I am faculty at the Lombardi Comprehensive Cancer Center, I wanted to have a cancer-related post!

The use of Papanicolaou (Pap) tests for cervical cancer prevention and early detection has been an essential aspect of gynecological care in the United States since the 1950s. Recently Pap tests have been supplemented by the use of viral genotyping tests for the types of human papilloma virus (HPV) which cause essentially all cervical cancers as well as by the HPV vaccine (co-invented by Georgetown’s own Dr. Schlegel!). Given the huge decrease in cervical cancers due to the introduction of the Pap test, it is hard to remember that in the 1940s cervical cancer was a major cause of mortality for young women in the US – it is now only the 14th most frequent cancer in American women while still being a major driver of mortality in many parts of the world – globally it is the 4th most common female cancer and the 2nd most common in the developing world. Improved adoption of screening and vaccination practices are on their way to changing this picture. Since HPV also causes certain types of head and neck cancers in both men and women, HPV vaccines may play an even larger role in cancer prevention in the future.

An important note about cervical cancer: Recent work has shown that both the incidence and mortality rates and the disparities between these outcomes for black and white women are higher than had been previously estimated, particularly for older women, due to the inclusion of women who had had hysterectomies – which generally include removal of the cervix – in the denominator. There is still much work to be done, but the type of tools available for cervical cancer prevention and early detection would be a dream to researchers in other cancer fields!

Hepatocellular carcinoma (HCC) – the most common type of liver cancer – is generally the result of chronic infection with hepatitis B virus (HBV) or hepatitis C virus (HCV); a 2006 study led by the CDC estimated that 78% of cases worldwide can be attributed to these two viruses, which can also lead to a variety of other problems such as cirrhosis. Over the past couple of decades, the incidence of HCC has been increasing in the US, with approximately half of the extra cases between 1975 and 2007 being due to the increase of older individuals with chronic HCV. HCV was only discovered in 1989 and screening of donated blood and organs for this virus only became available in 1992. Since infected blood was a common source for HCV transmission before that time, the CDC recommends that all adults born between 1945 and 1965 be tested for HCV regardless of other risk factors, given that those individuals are five times as likely to be infected compared to other adults and an estimated 45%-85% of HCV-positive individuals are not aware of their status. A number of highly effective treatments for HCV now exist; the primary challenge right now is the high price of the drugs, which often leads to their use being limited to a subset of infected individuals, such as those who already have advanced liver disease.

The situation is somewhat simpler for HBV compared to HCV, as an effective vaccine exists, which is now part of the standard childhood vaccine schedule recommended by the CDC. Consequently the incidence of HCC can be expected to have a substantial drop over the next few decades. I mentioned in Part 1 of this series that I would not discuss the prevention of infectious diseases via vaccination in this series. When talking about cancer prevention though, I could not help but highlight the astounding fact that yes, there are vaccines against specific cancers!

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