Viruses and Astrobiology
Interview with Dr. Baruch Blumberg (Part II)
Dr. Baruch Blumberg, who served as the first Director of the NASA Astrobiology Institute, is one of the world’s leading experts on the hepatitis B virus. He was the 1976 recipient of the Nobel Prize in Medicine, for his discovery of the virus, and subsequently helped develop both the test used for detecting it and a vaccine to prevent its spread. Hepatitis B virus, a primary cause of fatal liver cancer, has infected some 2 billion people now alive worldwide, and about 375 million remain infected. Blumberg is currently the senior advisor to the president of the Fox Chase Cancer Center and a professor of medicine at the University of Pennsylvania, both in Philadelphia.
Astrobiology Magazine’s Henry Bortman interviewed Dr. Blumberg about hepatitis B, his current research, and the role of viruses in the evolution of life on Earth. In this second and final part of the interview, Dr. Blumberg discusses the worldwide effort to vaccinate children against hepatitis B, and weighs in on the question of whether or not viruses are alive.
|The biomolecule, DNA, that twists throughout the cell nucleus.|
Astrobiology Magazine (AM): The Word Health Organization (WHO) is conducting a global effort to vaccinate people against the hepatitis B virus. How is their work progressing?
Barry Blumberg: It’s now one of the largest vaccination programs in the world. We invented the vaccine in 1969 and the testing process began seven or eight years later. It was finally approved by the Food and Drug Administration, in the early 1980s.
As of 2003, 151 – that’s about 80 percent – of the 192 members of the WHO had universal childhood vaccination programs. I saw a recent publication on this and the number has increased somewhat, so it’s probably over 80 percent now. That means that a very large number of newborns and children in the world have been vaccinated. My guess is that well over a billion – 1.2, 1.3 billion – doses have been administered. It’s compulsory in many parts of the United States, a good part of Europe, Japan, and large parts of China, several countries in Africa, South America, Middle East, Southeast Asia, and the Pacific. Some countries where they have very little hepatitis don’t have a universal vaccination program.
The goal of the WHO is to have vaccination programs in all countries by 2007. My guess is they won’t quite make that, but it’ll be getting pretty close. But there are gaps in the vaccination program in Africa. So, altogether vaccination is pretty widespread. (You can see the data on the WHO website. But there are still places for improvement. In China, for example, there’s very good coverage in the cities, but it’s lower in rural areas.
AM: If the program were administered universally, could this disease be eliminated?
BB: It’s an interesting question that’s under discussion. There may be some intrinsic reasons why eradication, theoretically, is impossible. The virus integrates into the genome of the human host, and as a consequence it remains in the host for life and possibly may be also present in his or her offspring. Now, whether that integrated virus is transmissible or not, is not known. The only way to find that out is to look at it epidemiologically and clinically, that is, to see what actually happens. So it’s possible that we may not be able to fully eliminate it because it’s in the genome, and it gets transmitted from generation to generation.
There are many viral genomes – that is, gene sequences that are highly homologous with viral gene sequences – in the human genome. In fact there are more viral genome homologous sequences than there are coding sequences, which is really kind of bizarre. And they are highly conserved. So that’s one of the issues: whether, because of the integration of the viral DNA into the host DNA, you can never really get rid of it. But that may not be an obstacle, because it may not be infectious. It may not turn into infectious virus, and if you have universal vaccination over the course of several generations, than the transmission may cease. Even if eradication is not possible, much better control is.
|The evolution of genomic complexity and metabolic pathways during Earth’s history. |
AM: Where this vaccination program has been most effective, what has been the impact on the gender ratio in the population?
BB: Emily Oster, who is an economist, just received her doctorate degree for her work on hepatitis B virus. She used demographic and public health data to demonstrate that probably, in two locations, that’s exactly what happened. One of them was Alaska, and the other Taiwan. I want to emphasize that Emily Oster’s work has just been published, and my guess is that there it will be greeted with controversy. But her data are clearly consistent with the hypothesis that vaccination changes the gender ratio. If you consider gender ratio to be a factor in evolution, in that it is related to the size of a population then the vaccination program has changed that.
This virus has been around since before there were humans. Many other animals have hepatitis B-like viruses. That means that there are very similar viruses to which the human virus is related. They have an evolutionary relationship to each other, and my guess is that it does not run exactly parallel to the descent relations of the host species. It’s a very interesting issue that I’d like to see pursued. We’ve tried to identify the first animals with hepatitis B-like viruses, and it’s difficult to pursue that work, because it’s hard to get funding for doing it.
AM: There’s debate among biologists whether viruses were a precursor to modern cellular life, or they evolved as a side effect of cellular life. What are your thoughts on this?
BB: That depends on what you mean by something being alive.
AM: That was going to be my next question.
BB: Well, that is entirely another conversation. Paul Davies, in his book The Fifth Miracle, lists the characteristics of life. He makes the point that there isn’t a firm definition of life. First, there’s replication and the replication of the means of replication. And, generally speaking, when you have life, you have decreased entropy. There’s nutrition and metabolism. There’s transfer of information. And one of the major characteristics of life is variation. Living forms nearly always exhibit diversity of forms that are subject to evolution. Life is complex, but has an organized complexity, and the different parts of an organism are integrated with each other. Now, viruses have a lot of these characteristics. They replicate, they transfer information, and they have a kind of metabolism, which utilizes the metabolism of the host. The major reason people say they can’t be the first life is they live in other cells. So the argument is, they couldn’t be first because they wouldn’t have had the cells. But that’s what’s happening in contemporary viruses. The predecessors of viruses may very well have been able to exist without cells by some mechanism they don’t currently exhibit. I think that’s a very interesting model to test; even if it’s not correct, there will be many interesting experiments and observations that emerge from testing the model.
|Virus-like particles isolated from the extreme environment of Yellowstone National Park, hot springs|
I can tell you that if we find a virus on Mars, we would be pretty excited about it.
AM: How would you go about trying to figure out where viruses fit into the history of evolution?
BB: The question of what role viruses may have taken in early life is being addressed by the study of viruses in extreme environments. About four ago, I helped establish the NASA Astrobiology Institute Virus Focus Group. My colleague, Kenneth Stedman at Portland State University, and I are the co-chairs. We’re encouraging the search for viruses living in extreme environments; it is a growing a growing field of study. We conducted a field trip at thermal sites in and near Mono Lake in eastern California. If all goes according to plan, we will soon visit another geothermal site in the Cascades. We look at viruses that live under extreme environments, which are thought to resemble the environments on early Earth, and possibly on early Mars. It is a systematic observational approach to the question, which, along with theory and experiment, may help us to understand what role they may have had in early days.
AM: You may already have answered my last question, but I’ll ask it anyway. Why are viruses an interesting area of study for astrobiologists?
BB: Because they tell us about the early events in the development of complex life and, conceivably they were the first form of living matter. My guess is that will be debated, but it will generate many interesting observations and experiments.