Using high titer West Nile intravenous immunoglobulin from selected Israeli donors for treatment of West Nile virus infection.

BACKGROUND: West Nile Virus (WNV) is endemic in Israel and a significant level of antibodies is present in the population due to natural exposure. Anecdotal cases suggested that the presence of anti-WNV antibodies in intravenous immunoglobulin (IVIG) from Israeli donors (IVIG-IL) assisted the recovery of patients with severe WNV infection. METHODS: To enhance the therapeutic efficacy of IVIG-IL against WNV infection, OMRIX Biopharmaceuticals, Israel, have developed a strategy for selection of plasma units from a 10% fraction of Israeli blood donors with anti-WNV antibodies. Positive units were processed into pharmaceutical grade WNV IVIG (WNIG). Following inoculation with WNV, mice received i.p. injections of different doses (0.01-8 mg/mouse) of IVIG-IL or WNIG, according to the specific experimental protocol. RESULTS: WNIG was about 10 times more potent (per gr of IgG) than was regular IVIG-IL when tested by ELISA and neutralization assays. In a mouse lethal WNV infection model, prophylactic treatment with WNIG was at least 5-10-fold more potent as compared to treatment with IVIG-IL. Treatment with WNIG during active encephalitis, three or four days following WNV infection, had a significant protective effect. WNIG was also very effective in protecting immunosuppressed mice. Indeed, treatment of dexamethasone-immunosuppressed mice with 0.2 or 1.0 mg WNIG 4 h after virus infection, led to 100% survival. CONCLUSION: IVIG produced from selected plasma donated in WNV endemic regions can be used to produce WNV IVIG with superior activity for therapeutic and prophylactic measures.

High titer human immunoglobulin as a specific therapy against West Nile virus encephalitis.

West Nile virus (WNV) is a mosquito-borne disease found most commonly in Africa, west Asia, and the Middle East, where up to 40% of the human population possesses antibodies. It is an emerging disease in the United States, since 1999 and has spread all over the US and Canada. The virus is maintained in nature in a mosquito-bird-mosquito cycle (primarily Culex), with human horses and other animals serving as incidental hosts. WN infection in humans is usually asymptomatic or involves flu like illness but can develop to severe meningo-encephlitis, with symptoms including cognitive dysfunctions, muscle weakness, paralysis and even death. Elderly and depressed immunity factors are at greatest risk of developing severe neurological disease. Studies in animal models have enhanced significantly the understanding of the viral and host factors that determine the pathogenesis and outcome of WNV disease. Currently, vaccines are available for animal use but there is no effective antiviral therapy or human vaccine for WNV infection. Passive administration of antibodies produced from selected donors has shown promising results in animal models.

Safety and efficacy in geese of a PER.C6-based inactivated West Nile virus vaccine.

Studies were performed with an inactivated vaccine against the mosquito-borne flavivirus, West Nile virus (WNV). The mammalian cell line, PER.C6, was selected as the platform for WNV growth since both the neurovirulent strains NY99 and ISR98 that cause epidemics in humans and high mortality in geese, respectively, could be propagated to high titers (10(9) to 10(10)TCID(50)/ml) on these cells. Based on the high DNA homology of the WNV envelope (E) protein and non-structural protein 5 (NS5), and identical neurovirulence in mice and geese, we concluded that NY99 and ISR98 viruses are closely related and therefore vaccine studies were performed with ISR98 as a model for NY99. A robust challenge model in domestic geese was set up resulting in 100% mortality within 7 days of intracranial challenge with 500 TCID(50) WNV. Geese were used to assess the efficacy and safety of an inactivated WNV vaccine produced on PER.C6 cells. Efficacy studies demonstrated 91.4% (53/58) protection of geese compared to no protection (0/13) in geese receiving a sham vaccine. A follow-up study in 1800 geese showed that the vaccine was safe with a survival rate of 96.6% (95% lower CL 95.7%). Initial studies on the correlates of protection induced by the vaccine indicate an important role for antibodies since geese were protected when injected intra-cranial with a mixture of serum from vaccinated, non-challenged geese and WNV. In all, these results provide a scientific basis for the development of an inactivated WNV vaccine based on NY99 produced on PER.C6 cells for human and equine use.

An inactivated West Nile virus vaccine for domestic geese-efficacy study and a summary of 4 years of field application.

Following the isolation in 1997 of West Nile virus from the brains of geese with an acute neuroparalytic disease in Israel, which reappeared in the following years, an inactivated vaccine was prepared from suckling mouse brains. The brain homogenate was inactivated with formaldehyde and blended with mineral oil adjuvant. In 2000, the first flocks were vaccinated according to a schedule of two subcutaneous doses, commencing at the age of 2 weeks and given with a 2-weeks interval. In efficacy trials, the challenge virus was injected at 7 weeks by the intracranial route, and over 85% protection was recorded in vaccinated geese. In extensive field trials conducted in 2001--2003, the vaccine was demonstrated to be safe and efficacious, and over 3 million doses were manufactured in 2000--2003.