Immune responses to filarial infection in laboratory mice

Models of filarial infection in laboratory inbred mice are valuable tools for assessing the relevance of anti-filarial immune responses in protection against these parasites. However, laboratory mice are not permissive for those filarial species which are known to infect humans. Therefore, immunity to the different stages of these filariae, i.e. infective third stage larvae (L3), adults and microfilariae, has been analyzed separately, as a surrogate approach. Although much information has been gathered by analysis of immunity and intervention in particular immune responses in these experimental systems, interference of different stage-specific responses as well as modulation of filarial maturation by the immune system cannot be assessed. A newly established infection model of filariasis, namely infection of laboratory mice with Litomosoides sigmodontis, accommodates the full developmental cycle of the parasite and may overcome this deficiency. Although the disadvantage of this latter model is that it deals with a filaria which is not pathogenic to man, it is the only model in which immunity can be analyzed during maturation of infective larvae into adult worms, the period considered most important for vaccination studies.