Chimp/Human Antibodies Can Protect Against Smallpox

A worldwide immunization program officially eradicated naturally occurring smallpox disease in 1980. However, concerns of a bioterror attack involving the highly contagious and fatal virus have prompted researchers to search for new smallpox vaccines and treatments.

The currently licensed smallpox vaccine consists of a live but weakened strain of vaccinia virus, a relative of the variola virus that causes smallpox. Vaccinia immunization has been proven effective in generating immunity against smallpox virus and other orthopoxviruses, including monkeypox and cowpox.

Although most reactions to the vaccinia virus are mild, the vaccine can cause serious and even life-threatening complications in individuals with weakened immune systems or skin conditions such as eczema, in infants younger than 12 months and in pregnant women. Health care providers currently treat smallpox vaccine complications with anti-vaccinia immune globulin (VIG) — pooled antibodies taken from the blood of individuals immunized with the smallpox vaccine. However, VIG is in short supply since the United States discontinued its public smallpox vaccination program in 1972.

NIAID-funded researchers have been working to develop alternatives to VIG based on antibodies they created in the laboratory. The study appearing online this week in PNAS details how senior authors Robert H. Purcell, M.D., co-chief of NIAID’s Laboratory of Infectious Diseases, and Bernard Moss, M.D., chief of NIAID’s Laboratory of Viral Diseases, and their collaborators developed hybrid antibodies from chimpanzees and humans that effectively inhibited the spread of both vaccinia and variola viruses in test tube experiments. Moreover, the hybrid antibodies proved more effective than VIG when tested in mice infected with vaccinia virus, even when given two days after virus exposure.

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Kathy Stover
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Message posted by: Rashmi Nemade