RNA has an ability to organize semidetached houses, similar to DNA. It needs a 2nd strand of RNA, which has its sequences precisely complementary with regard to the first strand. The 2nd strand is known as the antisense strand, since it has nucleotide sequences complementary to message sense. This procedure is known as “ direct suppression ” . Therefore when, mRNA forms a semidetached house with complementary antisense RNA sequence, interlingual rendition is blocked as a consequence. In the instance of “ indirect suppression ” , the sense sequences interact with the binding proteins or with the enzymes involved in the metamorphosis of nucleic acids. These interactions need non be cistron specific ( 23 ) . This is because either the ribosome can non come in the bases in messenger RNA or the ribonucleinases degrade the duplex RNA quickly. “ Non-specific suppression ” besides occurs when there is an addition in concentration of antisense oligonucleotides ( 22 ) . The Antisense RNA are now in usage for anti-HIV cistron therapy. It specifically inhibits look of few cistrons by stably incorporating with them. This was shown in bacteriums ( 14 ) and in Eukaryotic cells ( 6 ) . The method of utilizing antisense RNA by cistron transportation in to cells which consequences to the suppression of viral reproduction is called intracellular immunisation ( 1 ) .
Nucleic acids can be used as a healing medical specialty since they add up to the footing of antisense and cistron therapies. One of the major applications of the antisense scheme is to modulate the written text of disease-related cistrons in vivo. They have the ability to place their mark in a extremely sequence-specific mode and therefore they are utile in suppression of unusual cistron look and infective viral maps. Cells infected with human immunodeficiency virus type -1 ( HIV-1 ) or different signifiers of leukaemia have tremendously enhanced the chances of antisense research ( 4 ) .
Assorted surveies have been conducted to find the function of Antisense RNA in suppressing the HIV type -1 reproduction. From these surveies, of course happening antisense RNA have been identified. This cognition has been applied to the development of unreal antisense RNA.
Nailya E.Tagieva analyzed HIV-1BRU ORF on the plus strand of genomic DNA. This ORF is encoded by one of the HIV-1 antisense transcripts detected in the cell lines of the patients who were infected acutely and inveterate with HIV-1 ( 19 ) . A section of length 189 bases in this antisense ORF sequence is complementary to the rpm response component ( RRE ) part found in all unspliced and singly spliced HIV RNA transcripts ( 13 ) . Rev response component codifications for rpm protein which directs the export of RNA transcripts from karyon to cytoplasm for their look ( 9 ) . So adhering of antisense ORF sequence to this RRE part inhibit the viral cistron look.
Due to these grounds a survey was carried out by Nailya E.Tagieva to analyse the above suppression in presence of over showing natural antisense- RNA incorporating ORF. Formation of RNA-RNA intercrossed involves structural restraints. Stable Secondary constructions in complementary part prevent binding of antisense-RNA incorporating ORF to RRE ( 15 ) . This intercrossed formation requires helper proteins and structural characteristics to heighten the interaction between them ( 24 ) . Therefore from the consequences we can reason that of course happening antisense RNA possessing antisense RRE, has the possible to cut down HIV cistron look.
HIV-1 targeted antisense RNA is found invariably in free, non- injected cells. This may drive to “ intracellular unsusceptibility ” against consecutive HIV-1 infection. Thus the application of antisense RNA by intracellular look has been used ( 16 ) . Karola Rittner and Georg Sezatiel, 1991 conducted a survey, in which quintuple molarplasmids showing antisense RNA parts which are precisely complementary to put of HIV-1 mark parts was co-microinjected into the proviral HIV-1 DNA. This is done to prove their antiviral activity ( 16 ) . Approximately 75 % suppression was observed when antisense RNA sequence is complementary to the coding sequences of HIV-1 regulative proteins ( 7 ) .
Antisense oligodeoxyribonucleotides which are modified chemically are besides used for the suppression of HIV-1 virus reproduction ( 21 ) . They are added to the civilization medium. It was shown that antisense oligonucleotides which are added complementary to LTR sequences and splicing sites inside the HIV-1 genome, act as virus inhibitors ( 4 ) . But there besides occurs some disadvantages, because cellular consumption and stableness within the cell can non be controlled.
By and large, Retroviral vectors are most normally used as vehicle for efficient cistron transportation since it gets integrated with genome of mark cells ( 12 ) . Retroviral vectors have been used for transportation of functional HIV proteins and its efficiency has been tested in different cell lines and in primary CD4 lymphocytes ( 15 ) . In this instance it is the antisense RNA that is to be carried with the vector. Since we know that, the major marks for HIV infection are primary cells ; there arises restrictions in this scheme. To get the better of this restriction, a survey was carried out on different cell lines transduced with antisense RNA transporting retroviral vectors ( 12 ) .The cell lines transduced with vectors transporting mutated antisense RNA insert or missing insert as control were used ( 12 ) . The consequences reveals that this causes suppression of HIV-1 reproduction in primary T-lymphocytes.
The efficiency of a vector in transporting the antisense RNA and bring forthing the coveted consequence depends on the manner it is constructed ( 5 ) . From this we see that there are two of import considerations for an “ efficient vector ” .
Vector transcript ( individual or dual )
Assorted boosters are used in vectors, like MLV, SV40, HIV, etc. Choosing the right booster would increase the cistron look. While sing the boosters considered as suited campaigners for HIV suppression, tRNAmet human booster has been found to be of high efficiency than its opposite numbers ( 5 ) . In-vitro surveies show that, compared to individual transcript vectors, dual transcript vectors are extremely efficient in suppressing the reproduction of the HIV by interacting with their bases ( 20 ) .
Antisense RNA acts as down regulators of assorted stairss involved in the cistron look. This leads to a decrease or bar of host cell infection ( 18 ) . We can state that antisense RNA are highly- specific virus inhibitors. The of course happening antisense HIV-1 sequence is found to be expressed in assorted types of cells in all the persons affected with HIV-1 ( 11 ) . In the interim, a negative-strand HIV-1 booster has besides been identified ( 10 ) .This will assist in heightening the cognition of design of antisense RNAs.
Naturally happening antisense RNA with the presence of antisense RRE has the ability to suppress HIV cistron look ( 12 ) . Planing a suited vector is of premier importance for an efficient suppression. Double transcript vectors seem to be a good campaigner for reassigning antisense RNA ( 20 ) . Antisense RNA is likely to hold a promising hereafter in the intervention of other type of diseases.