With increasing whooping cough numbers, developing an effective new vaccine against Bordetella pertussis is a priority. Results from the multifactorial PERISCOPE Project will help scientists and clinicians move forward.
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Dominic Kelly, PhD, talked about vaccine-induced immunity and provided an overview of ongoing clinical trials in the PERISCOPE (Pertussis Correlates of Protection Europe) project in a key research session at the start of the annual meeting of the European Society for Paediatric Infectious Diseases, held virtually this year. Dr. Kelly, a pediatrician at the Children’s Hospital in Oxford and a member of the Oxford Vaccines Group, leads one of the studies in the project looking at infant vaccination.
Dr. Kelly began his presentation by showing a figure depicting where vaccine-induced immunity fits into the larger suite of clinical studies. These studies involve mouse models, human challenge models, and infection patients. A key theme is the use of a core group of immunoassays across all studies, with the hope that they will allow effective cross comparisons.
Dr. Kelly stated, “If we find a correlate of protection in the challenge model, we can then interpret the vaccine studies in the light of that because we are using standardized constant immunoassays.”
The assays being used depend in part on the specific study and the volume of blood available. They will generally include Bordetella-specific antibody and functional antibody assays, as well as interesting studies collecting mucosal samples from infants and adults to look at serological responses. Also under examination are a range of enzyme-linked immune absorbent spot, flow cytometry, and culture techniques looking at Memory B cells, T cells, and gene expression.
Complementing these assay studies, PERISCOPE includes a series of clinical investigations designed to throw light on three areas of interest, described below:
First, researchers hope to gain a better understanding regarding the effects of the original whole cell vaccine versus the current acellular variety. The former uses an inactivated version of the whole organism. Epidemiological studies, animal data, and experience in the field demonstrate that whole-cell vaccination results in a broad, long-lasting, and effective immune response.
By comparison, the acellular pertussis vaccine consists of between three and five protein components, which are purified from cultured Bordetella pertussis. While it is an effective vaccine, its effects are less durable; routine use in some countries is associated with cyclical outbreaks of increasing severity.
A second issue for researchers involved in the PERISCOPE project concerns the effects of maternal immunization. In the United Kingdom in 2012, for example, an increasing number of cases were noted 6-7 years after adoption of an acellular vaccine for routine vaccination in the 2nd-3rd trimester of pregnancy. Vaccination appears to effectively control neonatal disease, but whether this influences infant immune responses and long-term control of pertussis for a population is unknown.
Finally, the group is interested in the effects of an acellular booster across all age groups. While the effects may be short-lived, the booster is a potential strategy for controlling a population by repeated boosting of immunity. This is another area where using novel immunoassays may aid better understanding.
To find answers, the consortium has established four studies: the Gambia Pertussis study (GaPs) in Gambia and AWARE, the sister study to GaPs in the United Kingdom, addressing the acellular pertussis versus cellular pertussis question; the Pertussis Maternal Immunization Study in Finland (MIFI) addressing maternal immunization; and the Booster against Pertussis (BERT) study across three countries (U.K., the Netherlands, and Finland) looking at acellular booster across age groups.