Experimental hookworm infection: a randomized placebo-controlled trial in asthma.
BACKGROUND
Epidemiological studies suggest that hookworm infection protects against asthma, and therefore that hookworm infection may have a direct or an indirect therapeutic potential in this disease. We now report the first clinical trial of experimental hookworm infection in people with allergic asthma.


OBJECTIVE
To determine the effects of experimental hookworm infection in asthma.


METHODS
Thirty-two individuals with asthma and measurable airway responsiveness to adenosine monophosphate (AMP) were randomized and double blinded to cutaneous administration of either ten Necator americanus larvae, or histamine solution (placebo), and followed for 16 weeks. The primary outcome was the change in provocation dose of inhaled AMP required to reduce forced expiratory volume in 1 s by 20% (PD(20)AMP) from baseline to week 16. Secondary outcomes included change in several measures of asthma control and allergen skin sensitivity and the occurrence of adverse effects.


RESULTS
Mean PD(20)AMP improved in both groups, more in the hookworm [1.49 doubling doses (DD)] than the placebo group (0.98 DD), but the difference between groups was not significant (0.51 DD; 95% confidence interval: -1.79 to 2.80; P=0.65). There were no significant differences between the two groups for other measures of asthma control or allergen skin sensitization. Infection was generally well tolerated.


CONCLUSIONS
Experimental infection with ten hookworm larvae in asthma did not result in significant improvement in bronchial responsiveness or other measures of asthma control in this study. However, infection was well tolerated and resulted in a non-significant improvement in airway responsiveness, indicating that further studies that mimic more closely natural infection are feasible and should be undertaken.
Feary
J R
JR
Division of Epidemiology and Public Health, University of Nottingham, Nottingham, UK.
Venn
A J
AJ
Mortimer
K
K
Brown
A P
AP
Hooi
D
D
Falcone
F H
FH
Pritchard
D I
DI
Britton
J R
JR
D000249:Adenosine Monophosphate / Q000008:administration & dosage / Q000009:adverse effects; D000280:Administration, Inhalation; D000328:Adult; D000818:Animals; D001249:Asthma / Q000150:complications* / Q000276:immunology / Q000517:prevention & control / Q000628:therapy*; D001985:Bronchial Provocation Tests; D004311:Double-Blind Method; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D007814:Larva / Q000276:immunology / Q000502:physiology; D008297:Male; D017221:Necator americanus / Q000254:growth & development / Q000276:immunology / Q000502:physiology; D009332:Necatoriasis / Q000150:complications* / Q000175:diagnosis / Q000469:parasitology; D010919:Placebos; D012449:Safety; D012882:Skin Tests
D010919:Placebos; D000249:Adenosine Monophosphate