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Traces of miscegenation

Human virus reflects migrations between various ethnic groups in the state of Pará

048-049_Virus_202-1_novoA virus that often lies dormant and harmless and is found in about 80% of the world’s population is being used as a molecular marker of early migratory patterns in the North of Brazil. A study conducted by scientists at the Federal University of Pará (UFPA) shows that an Asian version of the John Cunningham virus, better known by the acronym JCV, can be found among African descendants of Maroons near the Trombetas River, in the northern part of Pará State. The study also reveals that a subtype of the virus associated with the northern Indians of the Americas and the first settlers of the continent is present in the territory of the Suruí indigenous tribe. These data suggest that the Maroons, a historically homogenous community, with origins in the late 18th century, made contact with the indigenous people, who usually carry the Asian type of the virus. The same data also indicate that an ancient strain of the microorganism brought by an individual coming from the northernmost part of the continent penetrated the lands inhabited by the Suruí, who today live in semi-isolation.

Among the inhabitants of Belém, where there has been a mixture of various ethnicities since the city’s founding nearly 400 years ago,  European, African and Asian forms of the JCV were identified, with those of the African variant most common. “The research findings are consistent with the information gathered by studies on the population genetics of Pará and historical data,” says Ricardo Ishak of the Virology Laboratory of UFPA’s Institute of Biological Sciences and the coordinator of the study, which was published in the journal Plos One October 12, 2012. Among the black population, the study also identified one individual with a microorganism that is genetically very similar to the JCV, the BKV virus which is usually found in patients who have undergone bone marrow or kidney transplants and in healthy Chinese.

The study sought to identify the virus in the urine of 341 healthy residents of the city of Belém, 42 indigenous people from 10 tribes, and 63 African descendants of Maroons. The JCV was found in one third of the residents analyzed in the state capital, a rate comparable to that of Australia and urban areas of the United States and Europe, and 40% of the descendants of slaves in the Trombetas River region. “Only one Suruí Indian had the virus,” says Ishak. “But, based on this record, we can say that the JCV circulates in this community.” This was the only indigenous ethnic group in which the virus was identified. By sequencing strands of the pathogen’s DNA, the researchers determined the type and subtype of the virus present in some of the individuals of the sample, that is, 46 people, who represent the populations of Belém, the Maroons and the indigenous people. “Some microorganisms can be considered bio-anthropological markers of migrations and the dynamic of miscegenation, since their types or subtypes are specific to a continent or a population,” says Maria Cátira Bortolini of the Federal University of Rio Grande do Sul (UFRGS) and the author of a study of this line of the Helicobacter pylori bacteria present in the human stomach. “The article [from Plos] is a good example of this premise.”

Out of Africa
The JCV does not cause disease in 95% of those infected. However, in individuals with compromised immune systems, such as AIDS patients, it may cause a neurological disorder known as progressive multifocal leukoencephalopathy (PML)that affects the central nervous system. In the case of the research conducted in Pará, the researchers were not interested in studying the pathogenicity of the virus, but instead were checking its usefulness as a living record of migrations and contacts between people of different ethnic groups or specific geographic origin. This approach has been used abroad for similar studies of various populations, such as the Indians of North America or the Japanese, and even to reconstruct the departure of Homo sapiens from Africa.

Discovered in the early 1970s, the JCV is divided into genetically distinct types and subtypes originating from specific regions of the planet. Therefore, according to some scientists, it lends itself to forming the basis of phylogenetic studies similar to those conducted on the basis of analyzing human mitochondrial DNA and Y chromosomes, which, respectively, reflect the maternal and paternal lineages of an individual or a population. If, for example, an African lineage of the pathogen is identified in a place inhabited by people with the Caucasian biotype, this data is interpreted as an indication that there was a prolonged interaction with an individual of black ethnicity. “This virus is persistent and passes from generation to generation,” says Antonio Vallinoto, an expert in epidemiology and molecular immunology at UFPA and another author of the study. “Its transmission usually occurs between members of the same family or community.” No one knows for sure how the virus is transmitted, but it is possible that one of the means of infection is through contact with contaminated water. The microorganism then lodges permanently in the human kidney.

Scientific studies suggest that the JCV emerged at about the same time as the appearance of Homo sapiens between 100,000 and 200,000 years ago. It likewise originated on the African continent, the cradle of modern man. The most ancestral form of the virus, which emerged in this part of the globe, is now called type C. From Africa, the microorganism would have spread throughout the world’s continents following in the footsteps of humans, its host. Then about 50 thousand years ago, two other types of the virus appeared, type B, originally found in northwest Africa and in Asia, and type A, which possibly emerged when man set foot in Europe. Each large virus type is further divided into subtypes, which are more specific and connected to a narrower area. For example, within type C, there is subtype Af1, predominant in most of Africa. Type B has two major subtypes: Af2, also of African origin, and MY, which is Asian. Type A has the EU subtype, which is linked to Europe.

According to the article written by the Pará researchers, the virus displays great genetic diversity among Belém’s population, with a predominance of type B, while the Maroons have African (Af2) as well as Asian (MY) variants. The Suruí Indians also carried the MY subtype. “We have also seen that there are mutations in the virus found in Pará that appear to have occurred after the JCV entered this part of Brazil,” says Ishak. A typically Amazonian subtype may be emerging from the infectious agent.

Scientific article
CAYRES-VALLINOTO, I. M. V. et al. Human JCV infections as a bio-anthropological marker of the formation of Brazilian Amazonian populations. Plos One. Published online October 12, 2012.