Cockroach infestations are a public health concern in the U.S. and worldwide, one particularly relevant to children and adults living in substandard housing. The droppings, exoskeletal debris and even saliva of cockroaches contain allergens that in some can provoke an immune response associated with stuffy nose (rhinitis), skin rashes, or in some instances wheezing reminiscent of asthma. Moreover, babies exposed to these allergens risk development of asthma: the Asthma and Allergy Foundation of America (AAFA) estimates that 23-60% of people with asthma living in an urban environment are sensitive to cockroach allergens.
Doctors diagnose cockroach allergy by applying crude extracts of cockroach debris to a patient’s skin and then checking the skin for redness or evaluating blood samples from patients for high levels of the antibody IgE, a readout of allergy. Most extracts used in the test protocol are a mixed bag of cockroach proteins, some called “Bla g”, so-named for the cockroach Blattella germanica.
Similar materials constitute the raw material of allergy shots, or allergen immunotherapy, in which patients are exposed to low doses of cockroach extracts, sometimes over a period of years, in hopes of desensitizing them. Although still experimental, cockroach immunotherapy appears to decrease symptoms in some patients and lower serum levels of IgE and other inflammatory substances following exposure.
To create safer, more effective immunotherapies, LJI scientists Bjorn Peters, Ph.D., and Alessandro Sette, Ph.D., are zeroing in on individual components of the standard cockroach extract to evaluate contributions of individual Bla g allergens and other constituents to the immune response.
To do so, they screened respective fragments of Bla g proteins, or peptides, for their ability to stimulate immune cell responses in blood samples from immunotherapy patients. Sette and Peters found that particular peptides elicited a strong T cell response without necessarily rousing a B-cell or IgE response, suggesting that different components of the extract promoted unique immune reactions.
Interestingly, T cell responses to a particular fragment differed slightly between patients with standard rhinitis symptoms versus those with asthmatic complications. This means that one-extract-fits-all immunotherapies could be improved by tailoring extracts to allergy severity. One way to do that might be to inoculate patients with recombinant allergens chosen specifically for that patient subgroup, rather with crude extracts. Such next-generation desensitization protocols could bring some relief to persons coping with living in cockroach-infested environments or decrease the risk of their children developing asthma.