Algal virus associated with altered human cognitive functions

Phycodnaviridae virionMany well-known human viruses, including poliovirus, rabies virus, West Nile virus, can infect cells of the nervous system, leading to alterations in the function of that organ. Could a virus that infects algae also cause human neurological alterations?

Chloroviruses are large DNA-containing viruses that infect unicellular algae called zoochlorellae (pictured: image credit, ViralZone). Unexpectedly, chlorovirus DNA sequences were found in the oropharynx of 40 of 92 individuals (43.5%) who had no known physical or psychiatric illness. The clinical specimens had been obtained as part of a study of cognitive function, and it was possible to determine that presence of chlorovirus DNA was associated with a slight but statistically significant decreased performance in tests for visual motor speed, delayed memory, and attention.

When mice were fed chlorovirus-infected algae, they showed decreased performance in tests of cognitive function, such as recognition memory and sensory-motor gating. Some of these animals developed antibodies against the virus, suggesting that viral replication took place. Furthermore, feeding of chlorovirus to mice was associated with changes in gene expression in the hippocampus, the part of the brain essential for learning, memory, and behavior.

It is not known if the chlorovirus replicates in humans or in mice; only viral nucleic acids were detected. No mention is made of attempts to isolate infectious chloroviruses from humans or mice. The amount of chlorovirus in the oropharynx is not known. However the results of sequence analysis, in which low numbers of sequences were found in each person suggest very low numbers of genomes. Of course, it is possible that virus replication took place some time ago, and its effects linger after replication has subsided.

Chloroviruses are commonly found in inland waters, and the subjects could have acquired the virus via inhalation or drinking contaminated water. It is entirely possible that the virus does not replicate in humans, but is present in the oropharynx as a common environmental contaminant. Many plant and insect virus sequences can be isolated from the human intestinal tract as a consequence of the food we ingest, but there is no evidence that they can replicate at that site. Consequently, chlorovirus might not have any role in the reduced cognitive functions observed in this study. It is possible that exposure to another factor together with chloroviruses, such as heavy metals, is responsible for the observed cognitive differences.

The suggestion that a virus infection might cause subtle cognitive defects is not outlandish. For example, lymphocytic choriomeningitis virus infects rodents congenitally or immediately after birth and establishes a persistent infection of virtually all tissues. These mice show no outward signs of illness, but careful study of infected animals reveals that they are less ‘smart’ than their uninfected peers.

The results are intriguing and warrant more study, including a determination of whether an infectious chlorovirus can be isolated from humans, whether this virus can replicate in human cells in culture, and how they differ from environmental isolates. It would also be important to determine if antibodies to chloroviruses are present in humans, and if they are associated with any diseases. It is too early to conclude that a virus of algae causes altered human neurological functions.

Comments on this entry are closed.

  • David K 13 November 2014, 11:59 am

    This paper found that eluting water over silica columns can yield diatom and algae DNA, probably because of environmental contamination from the sand which was used to make the silica.

    Far more likely scenario: the chloroviruses are coming from environmental contamination (they use Qiagen columns in the paper, which are silica columns), the mouse studies are bollocks, and the authors didn’t read the literature enough to know that this was a potential problem.

  • jshoyer 13 November 2014, 12:27 pm
  • profvrr 13 November 2014, 12:41 pm

    We talked about the Qiagen contamination issue: I don’t think it’s a problem in this paper, because the chlorella virus DNAs were not found in all samples. But they should have run a water control through the column and done some sequencing, as in the paper cited above. At least they should have addressed the possibility.

  • David K 13 November 2014, 12:55 pm

    I could easily imagine that the extent of contamination might differ from column to column, batch to batch. Knowing that algal DNA contamination is an issue specifically, I don’t think even a water control would be enough for me — they should have used a different extraction technique altogether using a non-silica based approach (perhaps TRI reagent and extraction). Until that experiment is done, I prefer to invoke Occam’s razor.

  • James T. 13 November 2014, 5:06 pm

    Yes. It looks like he linked it through the Columbia proxy in the article.

  • pk 14 November 2014, 1:36 pm

    “Some of these animals developed antibodies against the virus, suggesting that viral replication took place.”

    That statement seems straight out of a pharma companies bible. I have managed to develop antibodies against antigens which never replicate.

  • profvrr 14 November 2014, 3:50 pm

    In the previous study, all patient samples were positive due to column contamination.

  • alex W 15 November 2014, 12:54 pm

    correct me if i am wrong, but i don’t think they used any spin-column in their experiment: “DNA was extracted from throat swabs using Qiagen’s Gentra Puregene Buccal Cell Kit.”. just had a glance of the kit and it seem to be the precipitation approach

  • alex W 15 November 2014, 12:57 pm

    were having the same thought immediately….

  • David K 15 November 2014, 3:10 pm

    Good point, I had assumed that all the Qiagen kits use the silica column. I guess that weakens my original statement; however, I would still appreciate some water-only controls. I don’t think anyone expected there to be algal contamination of silica columns, and I could imagine that there are still some surprises out there.

  • alex W 16 November 2014, 3:25 am

    ye, i am with you: may be something funny going on in the hospital pipeline lol

  • alex W 16 November 2014, 3:32 am

    i know my comment should be based on evidences and reasons (i.e. reading and consider the whole paper), but it just feels like modern research has created an atmosphere that sometimes forces people to make extraordinary claim too early, for high journals (job security)

  • Karol 2 January 2015, 5:01 pm

    If we have brain eating algae the chance is that those viruses can fallow the algae. The immune system and Virus can weaken the algae

  • AutismDadd 4 January 2016, 10:38 pm

    ” Furthermore, feeding of chlorovirus to mice was associated with changes in gene expression in the hippocampus, the part of the brain essential for learning, memory and behavior.” i recall reading a report pubmed that discussed a child having mmr antibodies in his brain 8.5 months after vaccination.