Influenza, Immune System, and Pregnancy

Background Peripartum immunologic changes may affect latent TB infection (LTBI) diagnostic performance among HIV-infected women. Methods HIV-infected women were serially-tested with tuberculin skin test (TST) and interferon gamma release assay (IGRA) (QuantiFERON® TB Gold In-tube [QFT]) in pregnancy and 6 weeks postpartum in Kenya. Prevalence, sensitivity and agreement, and correlates of QFT/TST positivity were assessed. Quantitative QFT mitogen and M. tuberculosis antigen (Mtb-Ag) responses were compared by peripartum stage. Incidence of test conversion at 6 weeks postpartum was evaluated in baseline TST−/QFT− women. Results Among 100 HIV-infected women, median age was 26 years, median CD4 was 555 cells/mm3, and 88% were on antiretrovirals. More women were QFT+ than TST+ in pregnancy (35.4% vs. 13.5%, p=0.001), and postpartum (29.6% vs. 14.8%, p<0.001). Among 18 consistently QFT+ women, 8 (44%) converted from TST− to TST+, with improved test agreement postpartum (56.9%, κ=0.20 to 82.4%, κ=0.60). Three initially QFT−/TST− women had test conversion (TST+ and/or QFT+), suggesting new infection [incidence 13.4/100 person-years]. Mean QFT mitogen (4.46 vs. 7.64 IU/mL, p<0.001) and Mtb-Ag (1.03 vs. 1.54 IU/mL, p=0.03) responses were lower among all women retested in pregnancy vs. postpartum, and specifically among persistently QFT+ women (Mtb-Ag: 3.46 vs. 4.48 IU/mL, p=0.007). QFT indeterminate rate was higher in pregnancy (16%) compared to postpartum (0%) due to lower mitogen response. Conclusion QFT identified >2-fold more women with LTBI compared to TST in pregnancy and postpartum. Lower QFT Mtb-Ag and mitogen responses in pregnancy compared to postpartum suggest pregnancy-associated immunologic changes may influence LTBI test performance.

Leaders gathered at the US National Institutes of Health in November 2014 to discuss recent advances and emerging research areas in aspects of maternal-fetal immunity that may affect fetal development and pregnancy success.

Background In the US, influenza vaccination is recommended annually to everyone ≥ 6 months. Prior receipt of influenza vaccine can dampen antibody responses to subsequent vaccination. This may have implications for pregnant women and their newborns, groups at high risk for complications from influenza infection. Objective This study examined effects of prior vaccination on maternal and cord blood antibody levels in a cohort of pregnant women in the US. Study Design Influenza antibody titers were measured in 141 pregnant women via the hemagglutination inhibition (HAI) assay prior to receipt of quadrivalent influenza vaccine, 30 days post-vaccination, and at delivery (maternal and cord blood). Logistic regression analyses adjusting for age, BMI, parity, gestational age at vaccination, and year of vaccination compared HAI titers, seroprotection, and seroconversion in women with versus without vaccination in the prior year. Results Compared to those without vaccination in the previous year (n=50), women with prior vaccination (n=91) exhibited higher baseline antibody titers and/or seroprotection rates against all four strains after controlling for covariates. Prior vaccination also predicted lower antibody responses and seroconversion rates at one month post-vaccination. However, at delivery, there were no significant differences in antibody titers or seroprotection rates in women or newborns, and no meaningful differences in the efficiency of antibody transfer, as indicated by the ratio of cord blood to maternal antibody titers at the time of delivery. Conclusion In this cohort of pregnant women, receipt of influenza vaccine the previous year predicted higher baseline antibody titers and decreased antibody responses at one month post-vaccination against all influenza strains. However, prior maternal vaccination did not significantly affect either maternal antibody levels at delivery or antibody levels transferred to the neonate. This study is registered with the NIH as a clinical trial (NCT02148874).