Quantitative determination by ELISA of tobacco necrosis virus from necrotic local lesions in tobacco.

The amounts of tobacco necrosis virus antigen from necrotic lesions in tobacco leaves were estimated by ELISA. Less than 10% variation among different plates was obtained for the same sample placed in 3 wells randomly selected among the 60 internal wells of the plates, including in each test a dilution series of purified virus. Huxley's simple allometry equations y = bxm (y, absorbance; x, virus concentration) were calculated for each plate and gave reproducible results within a large range of virus concentration. The amount of viral antigen recovered from the necrotic centres of lesions was always significantly lower than those from the living tissues of the halo surrounding the centre. The serological activity recovered from both necrotic and halo tissues was not increased upon various treatments with disaggregating agents. During the continuous growth of the lesions the amounts of viral antigen extracted from the necrotic centre linearly decreased with time, suggesting virus degradation, whereas the amounts of antigen extracted from the living halo tissues increased with time, indicating that mechanisms of restricting viral spread and multiplication were not operating.