Inactivation of White Spot Syndrome Virus (WSSV) by normal rabbit serum: Implications for the role of the envelope protein VP28 in WSSV infection of shrimp
ABSTRACT White Spot Syndrome Virus (WSSV) is a highly pathogenic and prevalent virus affecting crustacea. A number of WSSV envelope proteins, including vp28, have been proposed to be involved in viral infectivity based on the ability of specific antibodies to attenuate WSSV-induced mortality in vivo. In the present study, a series of monoclonal and polyclonal antibodies targeting vp28 were tested for their ability to neutralize WSSV infectivity, with the purpose of identifying epitopes potentially involved in vp28-mediated infection of shrimp. Surprisingly, when used as protein A-purified immunoglobulin, none of the antibodies tested were capable of inhibiting WSSV infectivity. This included one polyclonal preparation that has been previously shown to inactivate WSSV, when used as whole rabbit serum. Moreover, strong inactivation of WSSV by some rabbit sera was observed, in a manner independent of anti-vp28 antibodies. These results underscore the problems associated with using heterogeneous reagents (e.g. whole rabbit antiserum) in viral neutralization experiments aimed at defining proteins involved in infection by WSSV. In light of this, the potential of anti-vp28 antibodies to specifically neutralize WSSV should be reconsidered.
SourceAvailable from: Hans J Nauwynck01/2007, Degree: PhD, Supervisor: Hans J. Nauwynck
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ABSTRACT: The antiviral product cidofovir and a diet supplemented with Spirulina platensis were tested for their efficacy to prevent or delay/reduce mortality due to white spot syndrome virus (WSSV) infection in specific pathogen free (SPF) shrimp Litopenaeus vannamei juveniles. Cidofovir was injected intramuscularly at 200 mg/kg shrimp mean body weight (MBW) at the moment of WSSV challenge. Spirulina was supplemented in the shrimp diet at 25% w/w and shrimp were fed for 4 days at 5% of the MBW per day before WSSV challenge. Shrimp were inoculated orally with WSSV at a dose of 30 SID50 (SID50 = shrimp infectious dose with 50% endpoint) and clinical signs and mortality were followed for 120 h post inoculation (hpi). WSSV infection status was determined by indirect immunoflourescence (IIF) in dead and survivor shrimp at the end of the trial. In two experiments, mortality was delayed approximately for 24 h by cidofovir treatment. The 100% mortality level was reached at 96–108 hpi in mock treated shrimp, whereas in cidofovir treated shrimp, 80–90% mortality was reached at the end of experiment (120 hpi). Significant differences (p < 0.05) in the median lethal time (LT50) of cidofovir-treated shrimp and mock-treated shrimp were found by probit analysis. A Spirulina supplemented diet delayed the onset of clinical signs for 12 h but had no effect on the cumulative mortality at the end of the experiment. This study opens perspectives for antiviral drugs to treat shrimp infected with WSSV.Aquaculture 05/2006; 255(1-4):600-605. DOI:10.1016/j.aquaculture.2005.10.050 · 1.83 Impact Factor