Abstract
BackgroundThe human genome contains about 8% of endogenous retroviral sequences originated from germ cell infections by exogenous retroviruses during evolution. Most of those sequences are inactive because of accumulation of mutations but some of them are still capable to be transcribed and translated. The latter are insertionally polymorphic HERV-K113 and HERV-K115. It has been suggested that their presence and expression was connected with several human diseases. It is also believed that they could interfere with the replication cycle of exogenous retroviruses, including HIV.ResultsPrevalence of endogenous retroviral sequences HERV-K113 and HERV-K115 was determined in the Polish population. The frequencies were found as 11.8% for HERV-K113 and 7.92% for HERV-K115. To verify the hypothesis that the presence of these HERVs sequences could affect susceptibility to HIV infection, comparison of a control group (HIV-negative, not exposed to HIV; n = 303) with HIV-positive patients (n = 470) and exposed but uninfected (EU) individuals (n = 121) was performed. Prevalence of HERV-K113 and HERV-K115 in the EU group was 8.26% and 5.71%, respectively. In the HIV(+) group we detected HERV-K113 sequences in 12.98% of the individuals and HERV-K115 sequences in 7.23% of the individuals. There were no statistically significant differences between groups studied.ConclusionThe frequency of HERV-K113 and HERV-K115 sequences in Poland were found to be higher than usually shown for European populations. No relation between presence of the HERVs and HIV infection was detected.
Highlights
Human endogenous retroviruses (HERV) are probably remnants of ancient retroviral infections in human germ cell lines
HERV structure is typical for retroviruses; they consist of gag, pol and env genes surrounded by long terminal repeat (LTR) sequences [7,8]
Literature shows an increasing amount of information about the possible role of endogenous retroviruses in health and disease. Some of those retroelements are involved in human placenta development (HERV-W, HERV-FRD) [9,41], in development and differentiation of normal tissue during embryogenesis [42], and in prevention of fetus rejection by the mother immune system [43]. Another beneficial aspect of HERVs presence in the human genome could be interference with exogenous retroviruses by blocking their receptors with protein Env or interference with virus replication by antisense RNA, which was shown in the case of murine endogenous retroviruses [4]
Summary
Human endogenous retroviruses (HERV) are probably remnants of ancient retroviral infections in human germ cell lines. Some HERVs (mainly belonging to the HERV-K group) are still active and capable of expressing, both at the mRNA and protein levels [15] It is the case of HERV-K113, which is able to produce viral particles, without the possibility of infecting new cells [16]. The human genome contains about 8% of endogenous retroviral sequences originated from germ cell infections by exogenous retroviruses during evolution. Most of those sequences are inactive because of accumulation of mutations but some of them are still capable to be transcribed and translated. It is believed that they could interfere with the replication cycle of exogenous retroviruses, including HIV
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