The PREGVAXGRIP study: a cohort study to assess foetal and neonatal consequences of in utero exposure to vaccination against A(H1N1)v2009 influenza.

BACKGROUND: In October 2009, in the context of an A(H1N1)v2009 influenza pandemic, a vaccination campaign was launched in France, in which one of the priority groups was pregnant women, on account of the high risk of developing complications following infection by this virus. OBJECTIVE: The aim of this multicentric, prospective, observational study was to assess safety and pregnancy outcomes in a cohort of pregnant women when receiving the A(H1N1)v2009 influenza pandemic vaccine. METHODS: This was a prospective study that followed up pregnant women recruited mainly in vaccination centres and maternity departments. Following the expected delivery date, follow-up data were collected concerning the delivery, the infant, and, if appropriate, the reasons why the pregnancy did not reach its term. RESULTS: Between 1 November 2009 and 31 March 2010, 2,415 pregnant women were included at the time of vaccination; 97.6 % of women received a vaccine without adjuvant and 2.4 % received an adjuvanted vaccine. Ninety-two (3.9 %) women were vaccinated during the first trimester of pregnancy, 1,090 (46.5 %) during the second trimester, and 1,162 (49.6 %) during the third trimester. One hundred and thirty-three adverse events (5.5 % of women) were reported, of which 12 were unexpected or serious. There were 2,246 (93.0 %) known pregnancy outcomes with 12 spontaneous abortions (0.5 %), 6 stillbirths (0.3 %), and 4 therapeutic abortions (0.2 %). There were 65 neonates with congenital anomalies, among which 31 were major. But only one congenital malformation (1.4 %) was reported for the 92 women vaccinated in their first trimester. Of the women, 93.3 % were delivered full term and 6.7 % preterm. For 96 (4.2 %) neonates, a disorder was reported in the neonatal period and 130 (5.6 %) were transferred to the neonatology department. CONCLUSIONS: This study suggests that exposure to the A(H1N1)v2009 pandemic influenza vaccine during pregnancy does not increase the risk of adverse pregnancy outcomes. However, because of the relatively small number of women exposed during the first trimester, other studies are needed to exclude an increased risk of malformation.

The common nodABC genes of Rhizobium meliloti are host-range determinants.

Symbiotic bacteria of the genus Rhizobium synthesize lipo-chitooligosaccharides, called Nod factors (NFs), which act as morphogenic signal molecules on legume hosts. The common nodABC genes, present in all Rhizobium species, are required for the synthesis of the core structure of NFs. NodC is an N-acetylglucosaminyltransferase, and NodB is a chitooligosaccharide deacetylase; NodA is involved in N-acylation of the aminosugar backbone. Specific nod genes are involved in diverse NF substitutions that confer plant specificity. We transferred to R. tropici, a broad host-range tropical symbiont, the ability to nodulate alfalfa, by introducing nod genes of R. meliloti. In addition to the specific nodL and nodFE genes, the common nodABC genes of R. meliloti were required for infection and nodulation of alfalfa. Purified NFs of the R. tropici hybrid strain, which contained chitin tetramers and were partly N-acylated with unsaturated C16 fatty acids, were able to elicit nodule formation on alfalfa. Inactivation of the R. meliloti nodABC genes suppressed the ability of the NFs to nodulate alfalfa. Studies of NFs from nodA, nodB, nodC, and nodI mutants indicate that (i) NodA of R. meliloti, in contrast to NodA of R. tropici, is able to transfer unsaturated C16 fatty acids onto the chitin backbone and (ii) NodC of R. meliloti specifies the synthesis of chitin tetramers. These results show that allelic variation of the common nodABC genes is a genetic mechanism that plays an important role in signaling variation and in the control of host range.

The NodA proteins of Rhizobium meliloti and Rhizobium tropici specify the N-acylation of Nod factors by different fatty acids.

Rhizobia synthesize mono-N-acylated chitooligosaccharide signals, called Nod factors, that are required for the specific infection and nodulation of their legume hosts. The biosynthesis of Nod factors is under the control of nodulation (nod) genes, including the nodABC genes present in all rhizobial species. The N-acyl substitution can vary between species and can play a role in host specificity. In Rhizobium meliloti, an alfalfa symbiont, the acyl chain is a C16 unsaturated or a (omega-1) hydroxylated fatty acid, whereas in Rhizobium tropici, a bean symbiont, it is vaccenic acid (C18:1). We constructed R. meliloti derivatives having a non-polar deletion of nodA, and carrying a plasmid with either the R. meliloti or the R. tropici nodA gene. The strain with the R. tropici nodA gene produced Nod factors acylated by vaccenic acid, instead of the C16 unsaturated or hydroxylated fatty acids characteristic of R. meliloti Nod factors, and infected and nodulated alfalfa with a significant delay. These results show that NodA proteins of R. meliloti and R. tropici specify the N-acylation of Nod factors by different fatty acids, and that allelic variation of the common nodA gene can contribute to the determination of host range.

The Rhizobium meliloti region located downstream of the nod box n6 is involved in the specific nodulation of Medicago lupulina.

Six nod box regulatory sequences are present in the Rhizobium meliloti genome. We have analysed the DNA region located downstream of nod box n6, and identified three open reading frames, designated nolQa, nolQb and nolS. LacZ fusions in these ORFs are not induced by classical nod gene inducers, which indicates that their expression either is not under the control of the nod box, or involves another regulatory mechanism acting in conjunction with the NodD/nod box regulatory circuit. Mutations in this n6 locus result in a delay in nodule formation on a particular host, Medicago lupulina. As this region is not strictly conserved among different R. meliloti strains, nolQa, nolQb and nolS may constitute auxiliary nodulation genes, for which the selection pressure is limited to particular host plants.