RT activity profile of two sucrose density gradients. Control B cell line was obtained from the relative of a patient with mitochondriopathy. MS B cell line was obtained from a patient with definite MS.

Consensus sequence with putative ORF from MSRV pol clones. The region corresponding to the PRT ORF cloned in a recombinant vector and expressed in Escherichia coli is boxed. The regions corresponding to the A and B fragments amplified from plasma samples from MS patients are indicated by brackets. The RT and RNase H (RNH) region is boxed with a dotted line. The highly conserved amino acids and/or active sites of enzyme activities of both PRT and RT (including RNH) are underlined.

Specific detection of MSRV-pol RNA sequence by RT-PCR in gradient-purified virion and in MS plasma. PCR products amplified from round 1 (ST1.1) with the ST1.2 primer set. From left to right: water control 1 from RT-PCR step with ST1.1 set; water control 2 amplified from water control 1 with ST1.2 nested primers; molecular weight markers; fractions 1–10 from sucrose gradient with MSRV virion; plasma samples C1 and C2 from healthy blood donors; and plasma samples MS1 and MS2 from two MS patients.

MSRV-cpol sequence amplified between the conserved motifs in the pol gene of retroviruses: alignment with other retroviruses. “Deletions” are represented by dashes; i, inosine. The most highly conserved VLPQG and YXDD regions are shown as separate blocks in bold type at the end of each sequence. Amino acids that are present in all or in all but one of the sequences are underlined. PCR primers (modified from ref. 20; see also ref. 14) PAN-UO and PAN-UI are orientated 5′ to 3′ (sense) whereas primer PAN-DI is 3′ to 5′ (antisense). Degeneracies are shown above (PAN-UO and PAN-DI) or below (PAN-UI) the PCR primer sequences. ⊥, the nine-base 5′ extension cttggatcc; ⌉, the nine-base 5′ extension ctcaagctt. The capture and detector probes DpV1 and CpV1b used in the ELOSA assay are shown below a representative MSRV-cpol sequence. At three positions below the translated MSRV-cpol sequence, alternative amino acids (representing “nonsilent” nucleic acid variations) are shown in italics; K and Y substitutions only were observed in PLI-1-derived clones whereas R and W were encoded by a significant proportion of the clones irrespective of derivation. Note that DpV1 is peroxidase-labeled and that CpV1b may be biotinylated at the 5′ end if streptavidin-coated plates are used. The name of each sequence is indicated on the Left. HTLV1, human leukemia virus type 1; MoMLV, Moloney murine leukemia virus; MPMV, Mason–Pfizer monkey virus; ERV9, endogenous retrovirus 9; MSRV-cpol, MS-associated retrovirus conserved pol region.