Evaluation of the agreement between Brix refractometry and serum immunoglobulin concentration in neonatal piglets

Can immunocrit be used as a monitoring tool for swine vaccination and infection studies?

BACKGROUND

The immunocrit is a cost-effective and straightforward technique traditionally used to assess passive immunity transfer to newborn piglets. However, it has not been previously used for monitoring the effect of vaccination and/or infections. Therefore, this study aimed to evaluate the usefulness of the immunocrit technique as an immunological monitoring tool in a vaccination and challenge scenario, using porcine circovirus 2 (PCV-2) as pathogen model. The immunocrit ratio was monitored in PCV-2 vaccinated (V) and non-vaccinated (NV) 3-week-old piglets (study day 0, SD0) that were subsequently challenged with this virus at SD21 and followed up to SD42. Additional techniques (PCV-2 IgG ELISA, optical refractometry, and proteinogram) were performed to further characterize the results of the immunocrit analysis.

RESULTS

Immunocrit, γ-globulin concentration and PCV-2 S/P values followed similar dynamics: descending after PCV-2 vaccination but ascending after an experimental PCV-2 inoculation. However, statistically significant differences between V and NV animals were only found with the PCV-2 ELISA. In this case, V animals had significantly higher (p < 0.05) S/P values (S/P ratio = 0.74) than NV (S/P ratio = 0.39) pigs only after challenge at SD42. On the other hand, serum total protein obtained by refractometer (STPr) were maintained from SD0 to SD21 and increased in both groups from SD21 to SD42. Correlations between techniques were low to moderate, being the most robust ones found between immunocrit and optical refractometry (ρ = 0.41) and immunocrit with γ-globulins (ρ = 0.39). In a subset of sera, the proteinogram technique was applied to the whole serum and the supernatant of the immunocrit, with the objective to characterize indirectly the immunocrit fraction. The latter one included all protein types detectable through the proteinogram, with percentages varying between 64.3% (γ-globulins) and 82% (β-globulins).

CONCLUSION

The immunocrit technique represented a fraction of the total serum proteins, with low to moderate correlation with all the complementary techniques measured in this study. Its determination at different time points did not allow monitoring the effect of vaccination and/or infection using PCV-2 as a pathogen model.

Effect of post-harvest cold plasma treatment on physicochemical properties and inactivation of Penicillium digitatum in Persian lime fruit

Cold atmospheric plasma (CAP) treatment is used in this study to inactivate Penicillium digitatum in lime fruit at post-harvest. Limes were inoculated manually withP. digitatum spore (106 CFU/fruit) and then were treated with CAP at 30, 60, 90, and 120 s and compared with untreated samples. The results showed that increasing the exposure time of CAP reduced spores to less than 7 CFU/fruit in 120 s on the lime peel. In the treated samples, antioxidant activity had an upward trend. In addition, phenolic compounds, vitamin C, density, soluble solid content (SSC), color, and pH of the lime juice were increased (P < 0.05). Compared to the control sample, no significant changes were observed in the juice yield percentage, texture, acidity, chlorophyll, and carotenoid (P > 0.05). The best exposure for CAP treatment was 60 s since it increased phenolic compounds, antioxidant activity, and vitamin C content in the lime juice.