Helicobacter sp. MIT 01-6451 infection during fetal and neonatal life in laboratory mice

Helicobacter sp. MIT 01-6451 has been detected in SPF mice kept inJapan. To characterize strain MIT 01-6451, its infection route during fetal and neonatallife and effects on pregnancy were investigated using immunocompetent and immunodeficientmouse strains (BALB/c, C57BL/6, and SCID). MIT 01-6451 was detected in the uterus, vagina,and mammary glands of 50% of infected SCID mice, whereas these tissues were all negativein immunocompetent mice. No fetal infections with MIT 01-6451 were detected at 16–18 daysafter pregnancy in any mouse strain. In newborn mice, MIT 01-6451 was detected inintestinal tissue of C57BL/6 and SCID mice at 9–11 days after birth, but not in BALB/cmice. The IgA and IgG titers to MIT 01-6451 in sera of C57BL/6 female mice weresignificantly lower than those of BALB/c mice. Although no significant differences in thenumber of newborns per litter were observed between MIT 01-6451-infected and MIT01-6451-free dams, the birth rate was lower in infected SCID mice than in control SCIDmice. The present results indicated that MIT 01-6451 infects newborn mice after birthrather than by vertical transmission to the fetus via the placenta and that MIT 01-6451infection shows opportunistically negative effects on the birth rate. In addition, thematernal immune response may affect infection of newborn mice with MIT 01-6451 throughbreast milk.