Hhv6

Mycoplasma pneumoniae Parainfluenza 1, 2, and 3 Respiratory syncytial virus

Herpes simplex Human Coronavirus Influenza A and B

Rubella virus Vaccinia virus

Varicella zoster virus

Abbreviations: CDV, canine distemper virus; EBV, Epstein-Barr virus; CMV, cytomegalovirus; HHV, human herpes virus. Source: From Ref. 1.

in antibody levels in MS patients could be considered a potential causal agent, other reasons for increased antibodies need to be considered. For example, reactivation of a latent virus secondary either to the MS inflammatory process or to the use of immunosuppressive drugs could in some instances explain these serological findings. Alternatively, elevated antibody levels to multiple infectious agents in the same patient could be attributable to nonspecific generalized B-cell hyperactivity. Such a phenomenon could also explain the presence of OCBs in MS CSF.

Similar to serum studies, an increase in CSF viral antibody titer or CSF/serum antibody ratio (after equalization of IgG levels in these two fluids) has been reported for EBV and measles virus. However, such changes have also been reported in some, but not all studies for rubella, human coronavirus 229E, herpes zoster, and other agents. As with serum, increased CSF titers to multiple viruses may be seen in the same CSF sample, furthermore, titers can fluctuate over time, indicating the potential problems inherent in attempts to link a virus to MS by serological methods alone.

In summary, the occurrence of spontaneous human and animal models of virus induced demyelination as well as evidence from epidemiological, serological, and pathological studies provides strong support for the existence of an infectious trigger but not as yet for a persistent CNS infection.

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