Researchers Close In on Ear Infection Vaccine

ENToday recently reported on a move toward more conservative use of antibiotics and ventilation tubes in the treatment of pediatric ear infections (ENToday, Nov. 2006, p. 1). Certainly, it would be preferable if we could find a way to prevent or reduce the number of ear infections a child experiences in the first place. Recent news reports indicate that researchers are now one step closer to that goal.

A research team at the University of Rochester Medical Center recently received a $3.5 million grant from the National Institute of Deafness and Other Communications Disorders (NIDCD) and a $500,000 grant from the Thrasher Foundation to develop a vaccine against nontypeable haemophilus influenzae (NTHi). Preliminary trials of the vaccine could begin as early as next year.

Bacterial Causes of Otitis Media

According to the NIDCD, the three main bacterial causes of otitis media are Streptococcus pneumoniae, Moraxella catarrhalis, and NTHi.

A vaccine targeting S. pneumoniae was introduced in 2000 and marketed by Wyeth as Prevnar, utilizing technology also developed at the University of Rochester Medical Center. The Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics recommended in 2002 that this vaccine be given to all infants and children under the age of 5. Since that time, the CDC reports a 78% reduction in pneumonia rates from the streptococcal strains targeted by this vaccine. A vaccine for NTHi would cause an additional significant reduction in the number of ear infections resulting from bacterial causes.

Decades in the Making

Technologies developed over decades are being combined and utilized to develop a safe and effective vaccine against NTHi. As with all vaccines, the basic idea is to inject the individual with an antigen from the bacteria or virus to stimulate the production of antibodies against that particular bacteria or virus. The antibodies then bind to the antigen, rendering it harmless.

One of the major antigens on the surface of NTHi bacteria cells is lipo-oligosaccharide (LOS), which is highly toxic when given to humans. In an effort to use this antigen to produce a vaccine for NTHi, researchers attempted to remove the toxic effects, creating dLOS, which proved to be unable to start antibody production. However, by combining dLOS with a vaccine for tetanous toxoid, researchers were able to stimulate the immune system to create antibodies in laboratory animals. A Phase I clinical trial involving 40 human adults was then conducted in 2002, showing this vaccine to be safe in that population.