Updated February 2013
This question-and-answer sheet is designed to help providers: (1) identify clients at risk for HIV-2 infection; (2) ensure appropriate HIV testing for those at risk for HIV-2; (3) monitor HIV-2 disease progression; (4) ensure that patients, including pregnant women, receive appropriate treatment for HIV-2; and (5) develop clear prevention messages to convey to the community about HIV-2.
There are two major types of HIV: HIV-1, which is predominant worldwide; and HIV-2, which is prevalent in Western Africa. HIV-2 is endemic in the following countries: Cape Verde, Ivory Coast, Gambia, Guinea-Bissau, Mali, Mauritania, Nigeria and Sierra Leone. Other West African countries with a high seroprevalence include: Benin, Burkina Faso, Ghana, Guinea, Liberia, Niger, Sao Tome, Senegal, and Togo. Angola and Mozambique and the country of India also have a high seroprevalence of HIV-2.
For an expanded discussion of HIV-2, including its epidemiology, genetic diversity, and natural history, see Human Immunodeficiency Virus Type-2.
Who is at risk for HIV-2 infection?
A person is at risk for HIV-2 if he/she:
- Originated from or traveled to an HIV-2-endemic area.
- Received medical care, injections, immunizations, phlebotomy, surgery, or blood products or participated in vaccine trials in an HIV-2-endemic area.
- Had sexual contact or needle-sharing contact with persons who are infected with HIV-2 or who are from an HIV-2 endemic area.
- Was born to a mother with HIV-2 infection.
* It is important to note that HIV-1-infected persons can become co-infected with HIV-2.
What is the prevalence of HIV-2 in New York City and New York State?
Between 1988 and 2010, 166 confirmed cases of HIV-2 were reported nationally; 77 of those cases were in New York City. However, HIV-2 may be underreported because antibody cross-reactivity between HIV-1 and HIV-2 is common and frequently results in misdiagnosis of HIV-2 as HIV-1. It is critical to provide early, effective education and prevention services to ensure that HIV-2 does not become a sub-epidemic within the current epidemic of HIV-1.
Will current laboratory blood tests detect HIV-2?
Most enzyme immunoassays can detect antibodies to HIV-2 and to HIV-1, and all New York State and New York City public health laboratories and major commercial laboratories now conduct enzyme immunoassays (EIAs) that detect antibodies to HIV-1 (group M), HIV-1 (group O), and HIV-2. However, not all combination assays differentiate between HIV-1 and HIV-2. Additional testing, including an assay that differentiates between HIV-1 and HIV-2, is necessary for reactive samples that are indeterminate or nonreactive according to HIV-1 Western blot. Because HIV-2 Western blot tests have not been approved by the FDA, laboratories should follow this algorithm for diagnosing HIV-2 infection.
For a list of FDA-approved tests for HIV-2, see Table 2 of Diagnostic, Monitoring, and Resistance Laboratory Tests for HIV.
For New York City providers requiring assistance with HIV-2 diagnostic testing:
- Contact the New York City Department of Health and Mental Hygiene (NYC DOHMH) at 1-212-447-2864.
For New York State providers outside of New York City requiring assistance with HIV-2 diagnostic testing:
- Contact the New York State Department of Health (NYSDOH) Wadsworth Center Laboratory at 1-518-474-2163 for assistance with HIV-2 diagnostic testing.
What clinical scenarios should prompt testing with an assay that differentiates between HIV-1 and HIV-2?
In addition to the at-risk patients listed in Question 1, the following patients should also receive testing that follows the algorithm for diagnosing HIV-2:
- Patients with opportunistic infections or other clinical symptoms of HIV infection but negative or indeterminate HIV-1 test results.
- Those who have received multiple HIV-1 indeterminate antibody test results.
- Patients with a confirmed diagnosis of HIV-1 but an undetectable viral load that is incompatible with his or her clinical or immunological status.
What are the clinical manifestations of HIV-2?
Although clinical manifestations of persons with HIV-2 infection are the same as those with HIV-1 infection (i.e., compromised immune function and subsequent opportunistic infections and cancers), HIV-2 is associated with lower viral load levels and slower rates of CD4 decline and clinical progression compared with HIV-1.
Do people infected with HIV-2 need different treatments or medications than people with HIV-1?
Many ART regimens that are appropriate for HIV-1 infection may not be as effective for HIV-2-infected patients. Consultation with a provider with experience in the management of HIV-2 is recommended before initiating ART in HIV-2-infected patients. Consider the following factors:
- Generally, HIV-2-infected patients progress symptomatically more slowly than HIV-1-infected patients, which may make the decision of whether to initiate ART more complex than HIV-1.
- Compared with HIV-1 infection, HIV-2 may create more rapid and significantly different resistance patterns to ART agents than HIV-1.
- HIV-2-mono-infected patients should receive two NRTIs and a boosted PI.
- Clinicians should not prescribe NNRTIs or the PIs nelfinavir, atazanavir, or fosamprenavir for HIV-2 mono-infection because they are ineffective; these agents may be used as part of a regimen for HIV-1/HIV-2 co-infected patients if adequate treatment for HIV-2 is also included.
How should HIV-2 disease progression and response to treatment be monitored?
Monitoring CD4 counts in combination with clinical evaluation is currently the most readily available method for assessing HIV-2 disease progression. However, in HIV-2-infected patients, CD4 cell counts often will not increase as dramatically with ART compared with HIV-1-infected patients, which limits the reliability of CD4 count as a marker for response to treatment. Although there are no FDA-approved viral load assays for HIV-2, some specialty laboratories may be able to perform these tests. The NYSDOH Wadsworth Center is currently seeking approval for a viral load assay for HIV-2. For more information, contact the Wadsworth Center at 1-518-474-2163.
Is HIV-2 transmitted vertically from mother to child?
Mother-to-child transmission of HIV-2 is much lower than that of HIV-1. However, high HIV-2 viral loads may increase the risk for transmission. HIV testing of pregnant women should be done with tests that can detect both HIV-1 and HIV-2 antibodies. Pregnant patients who meet any of the risk criteria listed in Question 1 should be tested using HIV-1/HIV-2 differentiating immunoassays and nucleic acid testing.
Research findings indicate that pregnant women with confirmed HIV-2 infection should receive ART prophylaxis to prevent mother-to-child transmission. Although this is similar to the practice in HIV-1 mono-infection, considerations for prescribing the appropriate regimen for HIV-2 in this setting are different from those of HIV-1. Consult with a provider who has experience treating HIV-2 infection, including perinatal ART for the mother and postnatal ART for the exposed infant. For more information about HIV-2 and pregnancy, see Human Immunodeficiency Virus Type-2.
A blood specimen should be obtained from all HIV-exposed infants and should be sent to the Pediatric HIV Testing Service at the NYSDOH Wadsworth Center for diagnostic testing. The Pediatric HIV Testing Service performs an immunoassay that differentiates between HIV-1 and HIV-2 antibodies on all infant samples. If the sample is reactive for HIV-2 antibodies, then a qualitative HIV-2 RNA test is performed to definitively diagnose or exclude HIV-2 infection.
What key messages about HIV-2 should HIV prevention providers convey to their communities?
HIV-2 is transmitted through the same risk behaviors as HIV-1. HIV-2 prevention efforts should reinforce the importance of eliminating or reducing exposure through sex or sharing drug-injecting equipment. Refer at-risk individuals to prevention and harm reduction services that include the following:
- in-depth behavioral counseling
- prevention support groups
- HIV counseling and testing
- male or female condoms
- syringe exchange programs
- screening and early entry into care
In addition to counseling HIV-negative individuals, providers should also counsel HIV-1-infected individuals about the possibility of becoming co-infected with HIV-2. For persons with HIV-1, repeat the importance of avoiding behaviors that may result in co-infection with HIV-2, which can potentially worsen their condition. Explain the importance of early medical care to help ensure that people with HIV-1 and HIV-2 infection access needed services. Comprehensive partner/spouse notification efforts may reduce the number of new HIV-1 and HIV-2 infections. Ensure early access to screening and treatment for those exposed to and/or infected with HIV-1 or HIV-2.
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