Cytokine Response to BCG Infection in Alcohol-Fed Mice

Abstract

Alcoholics have increased susceptibility to infections including tuberculosis. Chronic alcohol treatment impairs host response to bovine mycobacterium infection from BCG. This study assesses the role of four cytokines (TNFα, IFNγ, IL-4, and IL-10) in this impaired response. Twenty male C57BL/6 mice were pair-fed on the Lieber DiCarli control (LCD) or ethanol (LED) diets for 28 days. The LED treated subjects ate ad lib and consumed a mean of 13 g/kg/d of ethanol. After 14 days, based on body weight, subjects were randomly divided into four treatment groups of five each. Ten infected with 2 × 10 6 colony-forming units (CFU) of BCG by tail-vein. On day 28, the mice were sacrificed. Liver was cultured to determine the mycobacteria CFU/g tissue. Spleens were assayed for the levels of TNFα, IFNγ, IL-4, and IL-10 mRNA relative to mRNA levels for a housekeeping gene using a quantitative reverse transcriptase PCR. Without BCG infection, only the mRNA for IFNγ was increased by LED treatment, 51% ( p = 0.0001). BCG infection significantly increased TNFα, IFNγ, and IL-10 mRNA ( p < 0.0001). IL-4 mRNA decreased ( p = 0.0006). Chronic LED plus BCG infection further increased TNFα ( p = 0.002) and IFNγ ( p = 0.04); IL-10 was unchanged, whereas IL-4 was marginally further decreased ( p = 0.06). CFU/liver increased with LED (mean ± SD, 72 ± 33 × 10 5 vs. 39 ± 17 × 10 5; p = 0.004). A significant direct correlation was observed between CFU and TNFα, r = 0.70, p = 0.03. In conclusion, BCG infection increases TNFα, IFNγ, & IL-10 and decreases IL-4. CFU numbers correlate with mRNA for TNFα, and LED inhibits host containment of BCG infection as measured by liver CFU. This study could not identify cytokine alterations in either Th1- or Th2-type immune responses that might contribute to the impaired host response to the BCG infection.