Stability of Spodoptera litura nucleopolyhedrovirus in sodium dodecyl sulphate

Abstract

Sodium dodecyl sulfate (SDS) is a foaming agent used to extract occlusion bodies (OBs) of baculoviruses from infected cells or tissues of an insect. However, these OBs may be damaged by SDS at certain concentrations. In this study, the impact of different concentrations of SDS on OBs of Spodoptera litura nucleopolyhedrovirus (SpltNPV) was determined. Even though the number of OBs harvested increased with the increase in the concentration of SDS used in the extraction, the percentage of damaged OBs also increased correspondingly as detected through scanning electron microscope (SEM) photomicrographs. The result also indicates that infectivity of SpltNPV on second instars of S. litura larvae reduced significantly with an increase of SDS concentration used in the treatment. Among the four concentrations of SDS tested, SDS at 0.1% was able to release more quality virus. Thus, SDS of less than 0.1% is recommended for obtaining optimum number of quality OBs.

Concentration of sodium dodecyl sulfate used in occlusion body extraction affects Spodoptera littoralis nucleopolyhedrovirus biological activity

“…SDS concentrations higher than 1% caused significantly higher LD 50 and LT 50 values, suggesting that these concentrations could cause deceptive results in the assessment of baculovirus biological data. In similar findings to those of our study, Nazli-Huda et al (4) reported that increasing the SDS concentration from 0.005% to 0.2% in OB extraction decreased mortality from 95% to 68% and increased LT 50 values from 3.45 to 4.34 days in third instar S. litura larvae. These researchers recommended that SDS of less than 0.1% should be used to obtain optimum biological activity.…”

“…Both studies report an increase in LT 50 by increasing the SDS. Since larvae had consumed the same amount of OBs treated with different concentrations of SDS in the study by Nazli-Huda et al (4), any increase in the lethal time could be a direct consequence of the relatively lower ratio of intact (undamaged) OBs at higher SDS concentrations. In other words, finding lower LT 50 values at lower SDS concentrations could be due to relatively higher doses taken by larvae.…”

“…Mean time to death was compared at a biologically equivalent dose, LD 90 , in our study, while an absolute dose (2.4 × 10 7 OBs) was used in the study by Nazli-Huda et al (4). Both studies report an increase in LT 50 by increasing the SDS.…”

“…SDS causes OBs to lose their polyhedron envelopes (PEs) (1,4), an electron-dense structure surrounding the OB that is vital to the stability and biological activity of baculoviruses (7,8). OBs without PEs could not keep virions, causing gaps within the OBs (1,4).…”

“…However, the possible negative effects of SDS concentrations on viral efficacy in insects are poorly known. To our knowledge, the only study that examined the effect of different SDS concentrations on baculoviral activity was conducted by Nazli-Huda et al (4). These researchers found that increasing the SDS concentration from 0.005% to 0.2% during OB extraction decreased mortality from 95% to 68% and increased LT 50 values from 3.45 to 4.34 days in third instar Spodoptera litura larvae.…”