A killer infectious disease called Pertussis is a bacterial infection that causes whooping cough. Vaccines had brought the numbers of cases down dramatically, but now they’re on the rise again and Texas Biomed animals and scientists are involved in the search for something better to treat this health problem that kills more than a hundred thousand infants a year.
Pertussis has seen an alarming resurgence in the last decade. That’s surprising, given that a vaccine for this infectious disease has existed since the 1930s. The original vaccine, made with whole-cell killed Bordetella pertussis bacteria, was very effective but associated with some adverse events. A newer acellular pertussis vaccine with fewer adverse events was approved by the FDA in 1997. Recent epidemiological studies have found, however, that the immunity conferred by the new vaccine wears out during adolescence. That’s a problem, because although whooping cough isn’t fatal to adults, adults whose immunity has waned can carry and transmit the disease to infants, for whom it is frequently fatal. Infants typically receive antibodies from their mothers, but if the mother is not immune to pertussis, she cannot pass on immunity to the infant — thus putting the infant at risk of infection. And although the pertussis bacteria can be killed with antibiotics, the toxins released by the bacteria have done irreparable damage to the lung by the time the infant develops whooping cough. A current but imperfect strategy to protect infants is “cocooning” — that is, vaccinating anyone who might come into contact with the infant, including parents, siblings, grandparents, babysitters, and the like.
Nevertheless, the loss of pertussis immunity in the population as a whole, combined with the fact that many parents now choose not to vaccinate their children, has caused pertussis to become one of the largest preventable causes of death due to infectious disease worldwide in infants. To address this problem, researchers have been working to develop an improved pertussis vaccine. Some of these new strategies are now ready for pre-clinical testing, which is required by the FDA before moving forward with human clinical trials.
“It turns out the baboon is the perfect model for pre-clinical testing, because it is the only animal that mimics humans in that infant baboons develop a persistent cough when exposed to pertussis,” explained Robert Lanford, Ph.D., Director of the Southwest Primate Research Center (SNPRC). SNPRC is one of seven NIH-funded primate research centers across the country, and the only one that houses a colony of baboons. It is thus in a unique position to advance pertussis vaccine research at this critical stage. Working with the FDA and pharmaceutical companies, Lanford’s team is using the baboon model for testing new approaches to improving the acellular vaccine. Some of these new approaches use novel adjuvants (compounds designed to enhance immunity to vaccines) that can be used in combination with the existing acellular pertussis vaccine.
“The fastest way to get a better vaccine is not to make a new vaccine, because it takes decades to get a new vaccine approved; it is to enhance one that we already know is safe,” Dr. Lanford said. Of course, this isn’t guaranteed to work, so some research groups are taking different approaches and attempting to develop a new vaccine from scratch, he added. The goal is to produce data that will be used by the FDA to evaluate the potential effectiveness of the new vaccine and to decide if it can move forward to testing in human clinical trials, explained Dr. Lanford. It is usually a multi-year process. “Drugs that look most promising at first can run into safety problems,” Dr. Lanford explained. “It’s hard to predict which one will get through all three phases of human clinical trials — that’s why we need to work on multiple different approaches simultaneously.”