Objective To establish an indirect ELISA method for detection of measles virus antibody based on the nucleoprotein of measles virus expressed in prokaryotic system selected as the coating antigen.Methods The working conditions were screened and optimized to determine the operation process of indirect ELISA.The anti-measles virus IgG antibody in 157 sera of healthy children and mothers of newborn infants was detected and compared with the commercial measles virus ELISA IgG antibody detection kit.Results The result showed that the coefficient of variation of intra and inter assay repeatability of the indirect ELISA was less than 10％.Compared with the result of the commercial kit,the total concordance rate of serum samples was 95.5％,and the sensitivity and specificity were 94.8％ and 98.3％,respectively.There was no significant difference between the two methods (x2 =0.313,P＞0.05;x2 =0.000,P＞ 0.05) in the positive rate of measles virus IgG antibody in 85 healthy children at the age of 0～ 15 years.The level of measles virus antibody detected by ELISA established in this study showed the same increasing and decreasing trend as that detected by the commercial kit in different age groups.The correlation coefficient r of the quantitative result was 0.893 (P＜ 0.001),which showed the quantitative potential of the method.Conclusions The ELISA method established in this study has good stability,high sensitivity and specificity,and there was no significant difference between the detection results of commercial kit and the ELISA method.It can be used for the seroepidemiological investigation of measles virus and the evaluation of antibody level of the population after vaccination.

Objective To analyze the relationship between bone mineral density (BMD) of infants over 6 months of age and exclusive breastfeeding and calcium nutrition guidance during pregnancy in Baoding area, and to provide evidence for clinical application. Methods A total of 308 infants over 6 months of age were selected from Baoding Maternal and Child Health Hospital from January 2020 to January 2023, and their BMD was measured by ultrasound. The level of 25 (OH) D3 in subjects' blood was detected. spearman correlation test was used to analyze the correlation between infant bone mineral density and exclusive breastfeeding and calcium nutritional guidance during pregnancy, and logistics regression model was used to analyze the independent factors affecting infant bone mineral density. Results The level of serum 25 (OH) D3 in normal BMD group was significantly higher than that in abnormal BMD group (P<0.05). The rate of exclusive breastfeeding and the guidance rate of calcium nutrition during pregnancy in normal BMD group were significantly higher than those in abnormal BMD group (P<0.05). There was a significant positive correlation between different bone mineral density and exclusive breastfeeding and calcium nutrition guidance during pregnancy (P<0.05). Serum 25 (OH) D3 level, exclusive breastfeeding rate and calcium nutritional guideline rate during pregnancy were independent protective factors for bone mineral density (P<0.05). Conclusion Bone mineral density (BMD) of infants over 6 months of age is positively correlated with exclusive breastfeeding and calcium nutrition guidance during pregnancy, and exclusive breastfeeding and calcium nutrition guidance during pregnancy are independent protective factors affecting BMD of infants over 6 months of age.