Lassa fever: implications of T-cell immunity for vaccine development

Lassa fever is a re-emerging viral hemorrhagic fever, which causes signific ant human morbidity in endemic regions of West Africa. Attempts to vaccinat e against this virus in animal models including non-human primates have rev ealed that eliciting a strong cellular immune response protects from clinic al disease, but not infection, in the absence of measurable neutralizing an tibodies. As there is renewed interest in developing a vaccine against Lass a fever for use in humans, several questions should be addressed in view of the scarce knowledge of the mechanisms of natural immunity against this di sease. MHC-dependency of a vaccine relying mainly on the induction of T-cel l immunity and its ability to cross-protect against different Lassa virus s trains will be important issues. Furthermore, the question whether the vacc ine can prevent human-to-human transmission of the virus should be discusse d and the possibility that vaccination could predispose to immunopathology should be excluded. We are addressing some of the above mentioned problems concerning natural immunity through field studies in the Republic of Guinea , West Africa, and are presently studying the CD4 cell responses of Lassa a ntibody positive subjects on the basis of T-cell proliferation assays using recombinant Lassa virus proteins. (C) 1999 Elsevier Science B.V. All right s reserved.