Optic neuritis frequently occurs in multiple sclerosis (MS), and shares several similarities with the optic neuritis of Leber's hereditary optic neuropathy (LHON), which is mainly due to maternally transmitted mitochondrial DNA (mtDNA) mutations. Our report shows for the first time that a mitochondrial DNA background could influence the clinical expression of MS. One European mtDNA haplogroup was found only in MS patients with optic neuritis but not in MS patients without visual symptoms. Therefore, we hypothesize that mtDNA haplogroup J might constitute a risk factor for optic neuritis occurrence when it is coincidentally associated with MS, but not be a risk factor for developing MS per se as suggested previously.

Retroelements represent by far the largest and most widespread class of mobile genetic elements. Representative of several classes of retrotransposons have been characterized in a broad range of plant species, but only a few of them have been shown to be active. Among these, the tobacco Tnt1 retrotransposon has been isolated after insertion mutagenesis and is one of the very few to be transcriptionally active. Tnt1 expression is strongly regulated in a tissue-specific and developmental manner. Moreover, Tnt1 expression is induced by a range of biotic or abiotic elicitors, which all have in common the ability to induce the plant defense response. Regulatory sequences involved in this elicitor-mediated induction have been located in the LTR U3 region. The link between Tnt1 activation and the plant defense response might represent an example of the involvement of transposable elements in genome restructurations needed in response to environmental fluctuations such as pathogen attacks.

Long-term persistence of HIV vaccine-induced seropositivity in uninfected HIV vaccine recipients remains unknown. The duration of HIV humoral-induced responses was assessed in 72 volunteers who had received rgp160 and/or HIV recombinant canarypox virus constructs able to induce immune responses detectable using standard serological tests. Among the 43 rgp160 recipients, 94% and 83% remained HIV seropositive after 5 and 8 years of follow-up, respectively, while all the 29 volunteers who had received canarypox constructs alone were seronegative after 5 years. Because rgp160 induces long-term persistence (>8 years) of vaccine-induced HIV seropositivity, volunteers should be offered long-term follow-up to monitor their serological evolution.

No abstract