Expression of human endogenous retroviruses (HERVs) in vertically HIV-exposed and noninfected children

Abstract

The DNA of human cells consists of, among other components, complete or degenerated retroviral sequences called endogenous retroviruses (ERVs). The human endogenous retroviruses (HERVs) have similar characteristics to those of exogenous retroviruses, but they are not able to cause infection. They are transmitted genetically as proviral DNA to the germ cells. The expression of HERVs can influence the genetic fabric of the host, either as a benefit or in detriment of the host. There are several families of ERVS integrated in the human genome.Most of the complete genomes of proviral DNA (containing gag, pol and env, in addition to the LTRs) found in the human genome belong to the K family, HML-2 subfamily. Anti-HERV-K antibodies have been associated with HIV infection , being detected in 70% of HIV- infected individuals. The expression of HERVs is capable of inducing cellular immune response, and there are cells that recognize epitopes shared between HERVs and HIV-1 by increasing the immune response against exogenous viruses. Most children born to mothers infected with HIV (65-85%) do not acquire the infection, however, it is likely that a proportion of them had an intrautero contact with the virus. The hypothesis of this study is that these children, having been exposed to HIV during pregnancy, may have a greater expression of HERVs, when compared to those not exposed to HIV. Assuming that the differential expression of ERV-K is somehow a body's response to stress (such as contact with an exogenous retrovirus) seems a possible scenario, which certainly deserves to be investigated. Despite several studies correlating the expression of HERVs in situations of stress, infection by microbial agents, cancer and autoimmune diseases, there is no evidence that the expression of these elements is just a consequence of an alteration of the genetic net of the host, or if it indeed play a role in all these situations. Objectives: 1) To evaluate the expression of HERVs in children exposed to HIV and non-infected, as well as their mothers. 2) To evaluate the polymorphism of HERVs, K113, K115 and K106 in the pairs mother/children. Methods: Study group: Thirty vertically HIV-exposed children and noninfected (from 3 months to 5 years of age) , as well as their mothers (Mothers HIV +/ Exposed Children), followed at the Pediatric Infectious Diseases Division of Federal University of São Paulo (UNIFESP). A control group will consist of 30 children and their non-HIV- infected mothers (non-HIV Mothers / Children not exposed). Following informed consent, 3-5 mL of plasma samples will be obtained from the mother -children pairs of both groups. The RNA extraction kit (QIAampViral RNA Kit) will be used and the cDNA synthesis will be performed with the High Capacity cDNA Reverse Transcription Kit (Applied Biosystems). We will investigate the expression of the family K (HML1-10), H and W. To do so, we will use degenerated primers described in the literature to amplify the 10 subfamilies of HERV-K , as well as primers directed to the envelope region of other families. As no one knows the pattern of expression of endogenous retroviruses in children and babies,these three families will be investigated for being the most active in the human genome. (AU)