In 2001, as President of CAHR, Ken Rosenthal initiated the Mark Wainberg Lecture as a way to honour the veteran leader in the fight against HIV/AIDS, the “voice fighting AIDS publicly since the earliest days.”
Flash forward a decade, and Ken Rosenthal, the lecture founder, is now the lecture giver – specifically, the presenter of the 2012 Mark Wainberg Lecture at the annual CAHR conference.
Dr. Rosenthal was, along with Mark Wainberg, one of the first researchers in Canada to focus on HIV/AIDS. Both of them were working to identify the virus that caused AIDS long before anyone knew anything about HIV.
Today, from his base at the McMaster Immunology Research Centre and the Michael G. DeGroote Institute for Infectious Disease Research, Dr. Rosenthal is one of a group of researchers, led by the University of Manitoba’s Frank Plummer, who have been working for more than a decade with a group of Kenyan sex workers who appear to be resistant to HIV.
Dr. Rosenthal’s particular field of interest, and the topic of his lecture, was mucosal innate immunity and its role in HIV pathogenesis and resistance. Most pathogens enter our body, not through the bloodstream, but through the mucosal tissues that line our mouths, guts and, in the case of sexually transmitted infections such as HIV, our genital tracts. Dr. Rosenthal believes that our innate immune systems – a primitive immune defensive system found in all living things – plays a role in helping us to resist these pathogens.
“They are our early defences,” Dr. Rosenthal says. “They buy us time while they influence the adaptive immune response. The innate immune system shapes and influences the nature of the adaptive immune response.”
So what does this have to do with HIV-resistant sex workers? Well, to begin with, HIV is a sexually/mucosally transmitted virus infection that targets immune cells in the mucosa for rapid infection and destruction. Resistance to most infections is usually provided by our innate immune defences. Studies of the HIV-resistant sex workers provide a rare opportunity to understand the mechanism(s) of resistance and Dr. Rosenthal’s group focussed on the role of innate mucosal immunity. Their study showed that, in contrast to HIV-infected sex workers whose innate immune systems were highly activated, the HIV-resistant sex workers had very low levels of innate receptors in the cells of their genital tracts. It’s this low set point in their mucosal immune system that may make some women resistant to HIV infection. It may be genetic. Or it may be a case of persistent exposure to HIV, since there is anecdotal evidence that women who take a break from sex work often become infected upon their return to it. Or it may be some combination of the two. But cracking the secret could lead to ways to develop resistance in other people.
Dr. Rosenthal was recently awarded a large team grant from the Canadian HIV Vaccine Initiative to investigate resistance in another specific group – infants born to HIV-positive mothers. He and his team want to learn more about why infants whose mothers exclusively breastfeed are less likely to get infected with HIV than infants whose mothers use a mixed feeding strategy, adding other fluids or food. One hypothesis is that, in developing countries where there isn’t access to clean water; the contaminated water women must use may create inflammation in their babies’ guts, which makes it easier for the HIV virus in milk to travel into the bloodstream. An alternative hypothesis is that consistent exposure to innate factors in breast milk stave off infectious agents while the baby’s immune system develops.
“Breast milk is a gold mine of various innate immunity factors, and these are all natural products” says Dr. Rosenthal. “If we can identify and clone the genes behind these factors, they could potentially be added to breast milk to prevent HIV infection.”