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Risk for autism linked to herpes infection in pregnant women

Pregnant women with an active case of genital herpes were twice as likely to have a child diagnosed with autism spectrum disorder, according to a study that recently appeared in mSphere.

According to researchers, this is the first study to report a connection between antibody levels of anti-herpes simplex virus 2 (HSV-2) and the risk for autism spectrum disorder (ASD) among offspring.  

“Our data suggest that the presence of high levels of anti-HSV-2 antibodies at midpregnancy increases the risk of ASD in boys,” Milada Mahic, PhD, Center for Infection and Immunity, Columbia University, and colleagues wrote. “These findings provide support for the hypothesis that gestational infection may contribute to the pathogenesis of autism spectrum disorder and have the potential to drive new efforts to monitor women more closely for cryptic gestational infection and to implement suppressive therapy during pregnancy.”

The researchers evaluated blood samples from 875 mothers, 412 of whom had children diagnosed with ASD, who had enrolled in the Autism Birth Cohort study overseen by the Norwegian Institute of Public Health. The blood samples had been collected approximately 18 weeks into each woman’s pregnancy and again at birth. They analyzed the samples for antibody levels related to Toxoplasma gondii, rubella virus, cytomegalovirus, and herpes simplex viruses type 1 and 2.

They found that only the presence of high levels of antibodies to herpes simplex virus-2 was associated with risk for ASD, and that the link was only apparent in the samples taken midpregnancy when the fetal nervous system undergoes rapid development. An increase in herpes simplex virus-2 IgG levels from 240 to 640 arbitrary units/ml was associated with an OR = 2.07(95% CI, 1.06-4.06; P = .03) when adjusted for child’s birth year and parity.

“For boys, no significant differences were found between cases and controls for midpregnancy or postpartum maternal seropositivity to any of the pathogens. Correspondingly in girls, apparent differences for [cytomegalovirus, and herpes simplex viruses type 1 and 2] serostatus between cases and controls were not statistically significant at either the midpregnancy or postpartum time point,” Mahic and colleagues wrote.

They also stated that the sample size was not large enough to make an across-the-board assumption that the effect is sex-specific, but noted that generally speaking, autism is more common in boys. They also suggested that other research should explore if other viruses have similar effects as HSV-2.

“We speculate that ASD risk associated with high levels of antibodies to HSV-2 is not specific to HSV-2 but instead reflects the impact of immune activation and inflammation on a vulnerable developing nervous system. The replicability of these findings should be tested in other cohorts given the potential implications for serological monitoring of HSV-2 infections and opportunities for implementation of suppressive therapy during pregnancy,” researchers wrote. “Broader serosurveys should also be implemented to examine whether other infectious agents have similar impacts on the incidence of neurodevelopmental disorders.”– by Janel Miller

Disclosure: The researchers report no relevant financial disclosures.