HIV-2
Overview
HIV-2 is a type of human immunodeficiency virus primarily endemic to West Africa, but it has spread globally due to migration and globalization. It differs from the more common HIV-1 by being less transmissible, having lower viral loads, a longer asymptomatic phase, and a slower progression to AIDS. While less virulent than HIV-1, it can still lead to serious illness and requires specialized diagnostic tests and treatment strategies, as current antiretroviral therapy (ART) guidelines are not well-defined.
What is HIV-2?
HIV-2 is the second type of Human Immunodeficiency Virus.
Like HIV-1, it is a retrovirus that weakens the immune system by destroying CD4+ T-cells.
It is less common, less infectious, and progresses more slowly than HIV-1.
Mainly found in West Africa, with cases in Europe, India, and other regions due to migration.
Transmission of HIV-2
Same as HIV-1, but less efficient:
Unprotected sex (lower risk compared to HIV-1).
Blood exposure (sharing needles, unsafe transfusion).
Mother-to-child (pregnancy, birth, breastfeeding → but less likely than HIV-1).
Symptoms
The stages are similar to HIV-1, but slower:
1. Acute infection (weeks after exposure)
Flu-like symptoms: fever, rash, swollen lymph nodes, body aches.
Sometimes milder than HIV-1.
2. Chronic (asymptomatic/latent stage)
May last 10+ years without major symptoms.
Virus replicates at a lower level.
3. AIDS (advanced stage)
CD4 count <200 cells/µL.
Severe opportunistic infections (TB, pneumonia, fungal infections).
Weight loss, fever, night sweats, cancers (e.g., Kaposi’s sarcoma, lymphoma).
Diagnosis of HIV-2
Standard HIV tests (antibody/antigen tests) may detect HIV-2, but sometimes less sensitive.
Special tests:
HIV-2 antibody tests (differentiates from HIV-1).
PCR (HIV-2 RNA/DNA test) → more difficult because viral load is often very low.
CD4 count and viral load are monitored, but viral load may be undetectable even without ART.
Treatment of HIV-2
No cure, but ART (Antiretroviral Therapy) is effective.
Challenges: HIV-2 is naturally resistant to:
NNRTIs (Non-Nucleoside Reverse Transcriptase Inhibitors).
Some Protease Inhibitors (PIs).
Effective drugs for HIV-2:
NRTIs (e.g., tenofovir, zidovudine, lamivudine).
INSTIs (Integrase inhibitors) (e.g., dolutegravir, raltegravir).
Some PIs (boosted lopinavir, darunavir).
✅ With ART, people with HIV-2 can live long, healthy lives.
Prevention
Safe sex (condoms).
Safe injection practices.
PrEP (pre-exposure prophylaxis): May be less effective for HIV-2 (ongoing research).
PEP (post-exposure prophylaxis): Recommended after exposure, but regimen may differ from HIV-1.
Routine HIV testing in high-risk populations.
Key Characteristics​
Geographic Origin:Â
HIV-2 is primarily found in West Africa, though it has spread to other parts of the world.
Transmission: It is transmitted through sexual contact, sharing needles, and from mother to child (perinatal transmission).Â
Treatment of HIV-2 Infection
To date, no randomized controlled trials have addressed the timing of ART initiation or the choice of initial or subsequent ART for HIV-2. As a result, the optimal treatment strategy has not been clearly defined. Available evidence and extrapolation from HIV-1 data suggest that ART should be initiated at, or soon after, HIV-2 diagnosis to help prevent disease progression and transmission (AIII). However, people with HIV-2 generally experience poorer CD4 cell recovery on ART compared to those with HIV-1.
In vitro studies indicate that HIV-2 is sensitive to nucleoside reverse transcriptase inhibitors (NRTIs), but resistance to NRTIs appears more likely to develop than with HIV-1. HIV-2 is intrinsically resistant to non-nucleoside reverse transcriptase inhibitors (NNRTIs), making NNRTI-based regimens—including long-acting rilpivirine (RPV) with cabotegravir (CAB)—unsuitable for treatment (AIII). Several small studies have shown poor outcomes with dual-NRTI regimens or regimens combining an NNRTI with two NRTIs. Clinical data on triple-NRTI regimens are inconsistent.
Integrase strand transfer inhibitor (INSTI)–based or protease inhibitor (PI)–based regimens remain the primary treatment options for HIV-2. Three single-arm clinical trials have reported favorable outcomes with INSTI-based regimens. Data supporting PI-based regimens come mainly from observational studies. A randomized controlled trial (FIT-2; NCT02150993) comparing raltegravir (RAL) plus tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) to lopinavir/ritonavir (LPV/r) plus TDF/FTC has been completed, but results are not yet published.
Diagnosis & Treatment
Diagnosis: Diagnosis requires specialized tests, such as HIV-1/HIV-2 differentiation immunoassays, to differentiate it from HIV-1.
Treatment: Treatment strategies are not as well-defined as for HIV-1, and there is a need for more research on optimal antiretroviral treatment (ART) regimens.
Risks & Considerations
- Co-infection:ÂIt is possible to have both HIV-1 and HIV-2 infections simultaneously, which carries the same risks as HIV-1 mono-infection.
- Progression:Â Without treatment, the majority of individuals with HIV-2 will eventually develop AIDS and face fatal outcomes.
- Importance of Testing:ÂConsideration of HIV-2 is important when treating people with West African origins or who have had contact with individuals from that region.