Multiple sclerosis, human T-lymphotropic virus type I, and human endogenous retrovirus sequences

Distribution of human endogenous retrovirus HERV-K genomes in humans and different primates

The distribution of the human endogenous retrovirus (HERV)-K genome was investigated by Southern-blot analyses using a HERV-K-env DNA probe. With the exception of one DNA-sample, obtained from a Chinese individual in whom an amplification of HERV-K was detected, Southern-blot analyses yielded identical hybridization patterns with DNA from peripheral blood lymphocytes of 37 normal healthy blood donors, with DNA from six tumor cell lines, or with 23 DNA samples prepared from various carcinoma tissues. To elucidate whether the integration of HERV-K genomes into the primate lineage occurred as a single event or as an integration with later expansion, we further examined the evolutionary history of HERV-K by Southern blot analyses with DNA samples from different primate species. We detected HERV-K genomes in Macaca mulatta and Macaca silenus, which represent Old World monkeys, but not in prosimians (Galago demidovii) and New World monkeys, represented by Saguinus fuscicollis, Saguinus oedipus, and Callithrix iacchus. Thus, we assume that the infection of the primate lineage with HERV-K had occurred after the divergence of New World and Old World monkeys, but before the evolutionary expansion of large hominoids. In contrast to the apparent lack of HERV-K-env sequences in DNA from tissue of the New World monkey Saguinus oedipus (cotton-top marmoset), we found HERV-K-DNA in the B95-8 cell-line, which is a Saguinus oedipus leukocyte cell-line, immortalized in vitro by Epstein-Barr virus (EBV) and cultivated in human cells. It may be speculated that HERV-K-DNA or HERV-K-particles were introduced into these cells during in vitro transformation with EBV.

Serum antibodies from MS patients do not recognize HTLV-I, HIV-1, HIV-2 and SIV

A retroviral aetiology has been proposed for multiple sclerosis (MS). Although there is as yet no definitive evidence of viral involvement, there have been preliminary reports of antiretroviral antibody detection in sera from MS patients. Such sera have, for example, been found to react with HTLV-I. We here describe investigations involving various immunological techniques which attempt to confirm the virus-specific nature of these antibodies against a range of human and macaque retroviruses. Sera from 25 MS patients, 25 patients with non-associated neurological diseases and 16 patients with non-neurological conditions were tested by immunoblotting methods using lysates of HIV-1-, HIV-2-, HTLV-I- and SIV-infected cells as antigens. None of the sera reacted against any of these retroviral antigens but each serum demonstrated a distinctive and reproducible reaction pattern against cellular components of the cells in which the viruses were propagated. Further examination of the sera was carried out by ELISA using synthetic oligopeptides covering the HIV-1 Gag p24 protein as antigens. None of the sera reacted with the peptides. Our results suggest that in some MS patients the repeated seropositivity to HTLV-I may be due to the reaction with host cell proteins.

Absence of HTLV-1 related sequences in MS from high prevalence areas in western Norway

In Western Norway, long-term follow up epidemiological studies have revealed significant increases in the incidence and prevalence rates of multiple sclerosis (MS) in stable populations, indicating the impact of exogenous factors. In this study 183 MS patients and 102 controls from high prevalence areas in Western Norway were investigated for human T-lymphotropic virus type I (HTLV-1) related sequences by polymerase chain reaction. Using primers targeting the gag, pol and env genes in the HTLV-1 provirus genome, no amplification products were detected in the 183 MS patients or 102 controls. The results strongly suggest that neither HTLV-1 nor a closely related retrovirus participate in the aetiology of MS.

Antibodies in human sera recognizing a recombinant outer membrane protein encoded by the envelope gene of the human endogenous retrovirus K

Human endogenous retrovirus (HERV) K is present in about 50 copies in the human genome and transcription of HERV-K has previously been detected in several tumor cell lines as well as in peripheral blood lymphocytes from healthy donors. By means of immunoblotting we investigated the presence of antibodies recognizing recombinant HERV-K-envelope outer membrane constructs in different serum collectives. A total of 12.6% of sera obtained from normal blood donors was found positive. In serum collectives from breast carcinoma patients, HIV-1-positive individuals, and persons with cytomegalovirus infections no significant difference from the normal blood donor serum collective could be observed. Only a group of persons with a repeatedly raised serum neopterin concentration (> 10 nmol/liter) of unknown cause (HIV and hepatitis B and C virus infections were excluded) showed a significant higher percentage of HERV-K-outer membrane envelope-positive sera (21%). Furthermore we could observe a parallel HIV-1/HERV-K seroconversion, which probably is not due to an HIV-1/HERV-K-outer membrane envelope cross-reactivity. Possible implications of these findings are discussed.

Detection of coronavirus RNA and antigen in multiple sclerosis brain

Epidemiological studies of patients with multiple sclerosis (MS) and animal model data support the hypothesis that viruses initiate the immunopathogenic events leading to demyelination in MS. There have been no reports, however, of consistent detection of viruses in MS central nervous system tissue. We probed MS and control brain with cDNA probes specific for human, murine, porcine, and bovine coronaviruses. We report the in situ hybridization detection of coronavirus RNA in 12 of 22 MS brain samples using cloned coronavirus cDNA probes. In addition, tissue was screened for coronavirus antigen by immunohistochemical methods; antigen was detected in two patients with rapidly progressive MS. Significant amounts of coronavirus antigen and RNA were observed in active demyelinating plaques from these two patients. These findings show that coronaviruses can infect the human central nervous system and raise the possibility that these viruses may contribute to the pathogenesis of MS in some patients.