It has been shown that there are two types of Human
Immunodeficiency virus, type 1 and 2, both of which are the etiological agents
of AIDS. Both types have similar ways of transmission, but differ in term of
origin, rate of transmission, disease progression, and geographical
distribution. Type -1 is the commonest type
Immunodeficiency virus, type 1 and 2, both of which are the etiological agents
of AIDS. Both types have similar ways of transmission, but differ in term of
origin, rate of transmission, disease progression, and geographical
distribution. Type -1 is the commonest type
world-wide, accounting for the
majority of HIV infections, while type-2 is restricted majorly to west Africa,
accounting for small percentage of infections. It exhibits a longer latency
period, slower progression towards disease, lower viral burden, and decreased
transmissibility than HIV-1.
HIV-1: HIV-1
is divided into major group (group M) and two or minor groups “N, O and P”. Each
group is believed to represent an independent transmission of SIV into humans
(but sub-type within a group is not) (Sharp and Hahn, 2011). A total of 39 ORFs
are found in all six possible reading frames of HIV-1 complete genome sequence but only few of them are functional.
With ‘M’ for “major,” is the most common types of HIV, with more than 90% of
HIV/AIDS cases driving from infections with HIV-1 group M. The M group is
subdivided into further clades, called subtypes, that are also represented with
letter A-K, there are also “circulating recombinant forms” CRFs derived from
recombination between viruses of different subtypes which are each giving a
number. CRF12-BF, for example, is a recombination between subtypes B and F. The
N stands for “non-M and ‘non-P”. This group has only been seen in Cameroun,
only 10 group ‘N’ infections had been identified. The O (“outlier”) group is
not usually seen outside of west-Central Africa. It is reportedly most common
in Cameroun, where a 1997 survey found that about 2% of HIV positive sample
were from group O. Group ‘P’. in 2009 a newly
analyzed HIV sequence was reported to have greater similarity to Simian
Immunodeficiency Virus recently discovered in wild gorilla (SIV gor) than to
SIVs from chimpanzees (SIV cpz). The virus had been isolated from a Cameroonian
woman residing in France who was diagnosed with HIV-1 infection in 2004. The scientist reporting this sequence
placed it in a proposed group P “pending the identification of further human
cases”.
is divided into major group (group M) and two or minor groups “N, O and P”. Each
group is believed to represent an independent transmission of SIV into humans
(but sub-type within a group is not) (Sharp and Hahn, 2011). A total of 39 ORFs
are found in all six possible reading frames of HIV-1 complete genome sequence but only few of them are functional.
With ‘M’ for “major,” is the most common types of HIV, with more than 90% of
HIV/AIDS cases driving from infections with HIV-1 group M. The M group is
subdivided into further clades, called subtypes, that are also represented with
letter A-K, there are also “circulating recombinant forms” CRFs derived from
recombination between viruses of different subtypes which are each giving a
number. CRF12-BF, for example, is a recombination between subtypes B and F. The
N stands for “non-M and ‘non-P”. This group has only been seen in Cameroun,
only 10 group ‘N’ infections had been identified. The O (“outlier”) group is
not usually seen outside of west-Central Africa. It is reportedly most common
in Cameroun, where a 1997 survey found that about 2% of HIV positive sample
were from group O. Group ‘P’. in 2009 a newly
analyzed HIV sequence was reported to have greater similarity to Simian
Immunodeficiency Virus recently discovered in wild gorilla (SIV gor) than to
SIVs from chimpanzees (SIV cpz). The virus had been isolated from a Cameroonian
woman residing in France who was diagnosed with HIV-1 infection in 2004. The scientist reporting this sequence
placed it in a proposed group P “pending the identification of further human
cases”.
HIV-2: HIV-2
is much less pathogenic than HIV-1 and is restricted in its world-wide
distribution. The adoption of “accessory genus” by HIV-2 and its more
promiscuous pattern of co-receptor usage (including CD4-independence) may
assist the virus in its adaptation to avoid innate restricting factors present
in host cells. Adaptation to use normal cellular machinery to enable
transmission and productive infection has also aids the establishment of HIV-2
replication in humans. A survival strategy for any infections agent is not to
kill its host but ultimately become a commensal organism. Having achieved low
pathogenicity overtime, variant more successful at transmission will be
selected (Cheney and McKnight, 2010).
is much less pathogenic than HIV-1 and is restricted in its world-wide
distribution. The adoption of “accessory genus” by HIV-2 and its more
promiscuous pattern of co-receptor usage (including CD4-independence) may
assist the virus in its adaptation to avoid innate restricting factors present
in host cells. Adaptation to use normal cellular machinery to enable
transmission and productive infection has also aids the establishment of HIV-2
replication in humans. A survival strategy for any infections agent is not to
kill its host but ultimately become a commensal organism. Having achieved low
pathogenicity overtime, variant more successful at transmission will be
selected (Cheney and McKnight, 2010).
Reference
Scarlata, C. and Carter, C (2003): Role of
Myristoylation in HIV-1 Gag Assembly, Biochemistry,
42:6408-6417.
Myristoylation in HIV-1 Gag Assembly, Biochemistry,
42:6408-6417.
