Experimental Infection and Protection of Lambs with a Minute Plaque Variant of Rift Valley Fever Virus

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  • * Virology Department, U.S. Naval Medical Research Unit No. 3, Cairo, Egypt
  • | ** Faculty of Medicine for Girls, Al Azhar University, Cairo, Egypt
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The injection of a single dose containing 5 × 103 plaque forming units (PFU) of a minute plaque variant of Rift Valley fever virus (RVFV) into two susceptible lambs resulted in no detectable viremia, pyrexia or clinical signs of disease. Immunization with the minute plaque variant induced neutralizing antibody as early as seven days post-inoculation; however, no complement fixing antibodies were detected. Lambs immunized in this manner were protected when challenged with an infectious dose containing 1 × 103 PFU of wild type RVFV. These data indicate that the minute plaque variant may hold promise as a candidate live virus animal vaccine.