Abstract 924 Poster Session IV, Tuesday, 5/4 (poster 147)

Background: Cytomegalovirus (CMV) is the most common human congenital infection. Pre-pregnancy CMV immunity reduces congenital infection. The impact of humoral vs cellular immunity is not well understood. Methods: We studied hyperimmune anti-gB serum is prevention of congenital infection in early pregnancy of inbred JY-9 guinea pigs (GPs). Pregnant dams (N=13) were inoculated with 50,000 PFU of salivary gland GPCMV SQ, with 9 uninfected dams as negative controls. Six/13 infected dams got 1.5 ml pooled normal GP serum IM (non-immune (NI) controls), while 7/13 got 1.5 ml pooled anti-gB serum (neutralization titer = 1:256) IM on day 0, 2 and 5, day 1 being day of infection. Sacrifice was 12-14d post infection. Results: (Table)

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H&E sections showed marked focal mononuclear cell infiltrates in lobules and necrotic foci with neutrophilic infiltrates in trophoblastic septae of NI placentas, with fewer mononuclear infiltrates and no necrosis or infiltrates in PI placentas. Though there were fewer, less dense infiltrates in PI placentas vs NI placentas on H&E sections, significantly more esterase positive mononuclear cells were seen in PI placentas (p<0.05) indicating macrophage invasion. Immunoperoxidase stains revealed better preserved placental architecture, with fewer smaller viral foci in PI vs. NI placentas. Conclusions: 1) anti-gB passive immunization prevented fetal infection and intra-uterine growth retardation, shortened maternal viremia, reduced pregnancy losses and placental inflammation/infection. 3) Macrophage recruitment to placentas suggests protection or damage depending on timing of influx and placental viral load.