"Individuals with acute bipolar depression show immune alterations. Some of the alterations are similar to those found in acute mania."
That was the bottom line reported by Faith Dickerson and colleagues  following their analysis of blood samples provided by "82 individuals with acute bipolar depression, 147 with acute mania, and 280 controls." Looking for the presence of various antibodies to "human herpesviruses, gliadin, Toxoplasma gondii, and endogenous retroviruses as well as for C-reactive protein (CRP) and pentraxin-3" in said samples, researchers reported a few potentially important findings.
So: "The levels of CRP and IgG antibodies to an endogenous retrovirus, Mason-Pfizer monkey virus (MPMV), were significantly elevated in the bipolar depressed group." Further: "Levels of pentraxin-3 were reduced in both psychiatric groups." Researchers also reported that for 32 individuals who were hospitalised (and I assume treated) for bipolar depression, they "showed a significant decrease in the levels of MPMV antibodies, but not a change in the other markers."
Looking through the list of antigens included for analysis, without looking at the authorship list, I could have told you that the authors Faith Dickerson and/or Robert Yolken were involved in this study based on what has been discussed before on this blog (see here and see here for example). The work coming out of Johns Hopkins has been particularly interesting with their focus on "the role of infectious and inflammatory processes in complex psychiatric disease such as schizophrenia, bipolar disorder, and autism." Their most recent work on pentraxin-3 looks very interesting indeed (see here) and complements their most recent results.
The finding of elevations in the levels of CRP in the "bipolar depressed group" fits in well with the idea of inflammation being somehow involved in psychiatry (see here) and seemingly crossing diagnostic labels (see here). One might reasonable ask whether the research voices are indeed getting stronger for the potential usefulness of 'treating inflammation' when it comes to something like depression (see here) bearing in mind no clinical or medical advice is given or intended.
Finally, is that "endogenous retrovirus" finding reported by Dickerson et al. Regular readers of this blog might already know that I'm an avid [amateur] follower of the idea that all those fossil viruses that lurk in our genomes might be some much more than just junk DNA. With schizophrenia in mind (see here), with attention-deficit hyperactivity disorder (ADHD) in mind (see here), with autism in mind (see here), even with chronic fatigue syndrome / myalgic encephalomyelitis (CFS/ME) in mind (see here), I've covered the topic a few times on this blog. Although never coming across MPMV before, this is not the first time that antibodies to non-human primate viruses have been talked about with psychiatric / behavioural conditions in mind . Indeed a previous paper from Dickerson and colleagues  even went as far as suggesting that as part of suite of inflammatory markers, the presence and elevation of MPMV antibodies is likely derived "from the activation of homologous endogenous retroviruses and to be a reflection of immune activation." Similar sentiments seem to carry over to the most recent results too.
Music: Doves - There Goes The Fear.
 Dickerson F. et al. Immune alterations in acute bipolar depression. Acta Psychiatr Scand. 2015 Jun 9.
 Lillehoj EP. et al. Serum antibodies reactive with non-human primate retroviruses identified in acute onset schizophrenia. J Neurovirol. 2000 Dec;6(6):492-7.
 Dickerson F. et al. A combined marker of inflammation in individuals with mania. PLoS One. 2013 Sep 3;8(9):e73520.
Dickerson F, Katsafanas E, Schweinfurth LA, Savage CL, Stallings C, Origoni A, Khushalani S, Lillehoj E, & Yolken R (2015). Immune alterations in acute bipolar depression. Acta psychiatrica Scandinavica PMID: 26061032