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TABLE 2-1:

Global distribution of HIV-1 by subtype (Lancet 2007; 368:489)(continued)
Regions Total Infected Subtypes
East Europe, central Asia 1,600,000 A, B
East Asia 870,000 B, C,BC, CRF 01
Southeast Asia 7,400,000 B, AE

HIV-2 (See www.cdc.gov/hiv/pubs/facts/hiv2.htm)

HIV-2 is another human retrovirus that causes immune deficiency due to depletion of CD4 cells. It is found primarily in West Africa.*

CLINICAL FEATURES OF HIV-2: Compared with HIV-1, HIV-2 is less transmissible and is associated with a lower Viral Load (VL), leading to slower rates of both CD4 cell decline and clinical progression (Lancet 1994;344:1380; AIDS 1994;8 [suppl 1]:585; JID 1999;180:1116; JAIDS 2000;24:257; Arch Intern Med 2000;160:3286; AIDS 2000;14:441; JID 2002;185:905;AIDS 2008;22:211). Nevertheless, mortality rates for HIV- 1 and HIV-2 infection are similar when adjusted for VL (JAIDS 2005;38:335). HIV-2 has less homology with HIV-1 than HIV-1 subtypes (Nature 1987;328:543), and serology can be negative in 20 to 30% depending on which enzyme immunosorbent assay (EIA) is used. Four FDA-cleared rapid tests detect HIV-2 (See below). Western blots (WBs) for HIV-2 are neither well standardized nor FDA-approved (Ann Intern Med 1993;118:211; JAMA 1992;267: 2775).

Several issues affect the management of HIV-2-infected patients:

1) Many patients are co-infected with HIV-1 (AIDS 2002;16:1775).

2) Doubling time is 6-fold longer than HIV-1 leading to low VL, decreased transmission, and long period of asymptomatic infection (JAMA 1993;270:2083).

3) HIV-2 is not susceptible to NVP or EFV (but ETR shows some activity). (J Clin Microbiol 2000;38:1370; NEJM 2000;342:1758; JAIDS 2000;25:11; AIDS 2004;18:495; Antivir Ther 2004;9:57; J Clin Microbiol 2005;43: 484).HIV-2 is susceptible to PIs but has accelerated genotypic resistance (Antimicrob Ag Chemother 2007;51:604). One report indicates susceptibility to RAL (AIDS 2008;22:1091).

4) Laboratory confirmation of infection may be difficult (see below).

5) There are no commercially available VL assays for HIV-2 or resistance testing (Arch Intern Med 2000;160:3286), although these tests can be performed by some specialty laboratories (J Virol Methods 2000;88:81; CID 2004;38:1771; JAIDS 2000;24: 257; see www.phls.co.uk).

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* Endemic areas in West Africa – Benin, Burkina Faso, Cape Verde, Cote d'lvoire, Gambia, Ghana, Guinea Guinea-Bissau, Liberia, Mali, Mauritania, Niger, Nigeria, São Tome, Senegal, Sierra Leone, and Togo; other African countries – Angola and Mozambique (MMWR 1992;4[RR-12]:1).
2007 © John G. Bartlett, M.D. All rights reserved.7

Chapter 2: Laboratory Tests

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