U.S. data revealed that cytomegalovirus was independently associated with latent tuberculosis infection, and both were associated with high levels of C-reactive protein, suggesting enhanced systemic inflammation, researchers reported.
“Prior studies showed that cytomegalovirus infection may affect progression to active tuberculosis and tuberculosis outcomes,” Yuri van der Heijden, MD, MPH, assistant professor of medicine in the division of infectious diseases at Vanderbilt University Medical Center, told Healio.
“Dr. Moises A. Huaman’s group had been working with the National Health and Nutritional Examination Survey (NHANES) data with potentially interesting findings on this topic particularly around the relationship of cytomegalovirus infection and tuberculosis infection, rather than active tuberculosis so, we decided to collaborate,” van der Heijden said.
Van der Heijden and colleagues analyzed NHANES data from 1999 through 2000 for tuberculin skin testing (TST), TB questionnaires and cytomegalovirus (CMV) antibody testing.
Of the 7,363 participants they included in the study, 403 (5.5%) had latent TB infection (LTBI). Among 4,215 participants who were tested for CMV, 90% of participants with LTBI were CMV positive compared with 58% of those without LTBI, the researchers reported.
The study also demonstrated that a higher proportion of participants with LTBI had high C-reactive protein (CRP) levels compared with those without LTBI (45% vs 31%), and that CMV IgG positive status was associated with LTBI (OR = 8.37; 95% CI, 3.67-19.05). LTBI and CMV were both associated with higher CRP in weighted univariate logistic regression models.
The researchers found that older age (30 to 49 years vs. 6 to 19 years), male sex, foreign birth and large household size were significantly associated with LTBI. Positive CMV IgG remained associated with LTBI (adjusted OR = 2.94; 95% CI, 1.19-7.28) in a multivariable regression model.
Van der Heijden explained that the association between CMV and LTBI is still exploratory, and because of the study design, they are unable to draw conclusions about the direction of the association, such as if one infection predisposes to the other. However, there is a growing recognition that infections such as CMV “may alter host immunity in a way that influences how tuberculosis unfolds in humans,” he said.
Van der Heijden added that previous findings showing how certain individuals do not get infected with TB despite being heavily exposed “raise questions about intrinsic host factors” and how they may be influenced by the interaction between widely present pathogens and the host immune system, although another possible explanation is that individuals with both infections share common external risk factors for both infections.
“Cytomegalovirus and tuberculosis infections are associated with one another, and both infections appear to have a role in chronic inflammation,” van der Heijden said. “The clinical implications of our findings require further investigation.”