AUTHOR=Logan Erin , Luabeya Angelique Kany Kany , Mulenga Humphrey , Mrdjen Dunja , Ontong Cynthia , Cunningham Adam F. , Tameris Michele , McShane Helen , Scriba Thomas J. , Horsnell William G. C. , Hatherill Mark 

TITLE=Elevated IgG Responses in Infants Are Associated With Reduced Prevalence of Mycobacterium tuberculosis Infection

JOURNAL=Frontiers in Immunology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2018.01529

DOI=10.3389/fimmu.2018.01529

ISSN=1664-3224

ABSTRACT=<sec id="ST1"><title>Background</title><p>It is unclear whether antibodies can prevent <italic>Mycobacterium tuberculosis</italic> (<italic>Mtb</italic>) infection. In this study, we examined the relationship between total plasma IgG levels, IgG elicited by childhood vaccines and soil-transmitted helminths, and <italic>Mtb</italic> infection prevalence, defined by positive QuantiFERON (QFT) test.</p></sec><sec id="ST2"><title>Methods</title><p>We studied 100 <italic>Mtb</italic> uninfected infants, aged 4–6 months. Ten infants (10%) converted to positive QFT test (QFT+) within 2 years of follow-up for <italic>Mtb</italic> infection. Antibody responses in plasma samples acquired at baseline and tuberculosis investigation were analyzed by enzyme-linked immunosorbent assay and ImmunoCAP<sup>®</sup> assay.</p></sec><sec id="ST3"><title>Results</title><p>QFT− infants displayed a significant increase in total IgG titers when re-tested, compared to IgG titers at baseline, which was not observed in QFT+ infants. Bacille Calmette-Guérin (BCG) vaccine-specific IgG2 and live-attenuated measles vaccine-specific IgG were raised in QFT− infants, and infants who acquired an <italic>Mtb</italic> infection did not appear to launch a BCG-specific IgG2 response. IgG titers against the endemic helminth <italic>Ascaris lumbricoides</italic> increased from baseline to QFT re-testing in all infants.</p></sec><sec id="ST4"><title>Conclusion</title><p>These data show raised IgG associates with a QFT-status. Importantly, this effect was also associated with a trend showing raised IgG titers to BCG and measles vaccine. Our data suggest a possible protective association between raised antibody titers and acquisition of <italic>Mtb</italic> infection, potentially mediated by exposure to antigens both related and unrelated to <italic>Mtb</italic>.</p></sec>