Virology USMLE Step 1 Practice Question
A 14-day-old male infant born vaginally at 39 weeks gestation presents to the emergency department with vesicular rash on the scalp and eyelids, bilateral conjunctivitis, and respiratory distress. Chest X-ray shows bilateral infiltrates. The mother reports she had primary genital herpes simplex virus (HSV-2) infection at 32 weeks gestation treated with acyclovir until delivery. Laboratory testing confirms HSV-2 by PCR in the infant's vesicular fluid, conjunctival swab, and cerebrospinal fluid. Which of the following best explains this infant's susceptibility to disseminated neonatal HSV disease despite antiviral treatment of the mother during pregnancy?
Answer choices
- AMaternal IgM antibodies actively transferred across the placenta enhance viral replication in neonatal tissues
- BTransplacental infection occurred because primary maternal infection in the third trimester allows sufficient time for hematogenous dissemination to the fetus
- CThe neonatal immune system lacks maternally-derived neutralizing IgG antibodies and has insufficient cell-mediated immunity to contain HSV disseminationCorrect answer
- DVaginal shedding of HSV despite maternal antiviral therapy resulted in mucosal exposure during delivery, and the neonatal epithelial barrier is permeable to viral entry
- EHSV demonstrates selective tropism for neonatal neural and respiratory tissues due to age-dependent differences in viral receptor expression
- FMaternal treatment with acyclovir crossed the placenta and caused teratogenic effects that impaired fetal immune development
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