Immunity to airborne challenge with Venezuelan equine encephalitis virus develops rapidly after immunisation with the attenuated vaccine strain TC-83

Mice vaccinated subcutaneously with the attenuated vaccine strain of Venezu elan equine encephalitis virus (VEEV) rapidly develop immunity to subcutane ous or airborne challenge with virulent VEEV. The specificity of this immun e response was demonstrated by challenge with a heterologous virus (St. Lou is encephalitis virus). Examination of the levels of VEEV-specific antibody classes in serum and respiratory secretions suggested that the rapid devel opment of immunity was coincident with the appearance of specific IgM and I gG (but not IgA) in the respiratory tract. In order to confirm the role of respiratory tract antibody, mice were passively immunised either intraperit oneally or intranasally with polyclonal VEEV-specific IgG. Intranasal admin istration of specific IgG significantly enhanced protection against airborn e challenge. These results confirm the need to emphasise local antibody pro duction in the development of improved VEEV vaccines. (C) 1999 Elsevier Sci ence Ltd. All rights reserved.