The additional difficulty of obtaining a timely viral
load assay makes monitoring the response to antiretroviral therapy difficult. Regular CD4 cell count monitoring is therefore very helpful to identify individuals with rapid progression. It is also important to note that treatment response may be poorer in those with HIV-2 infection, with significantly lower viral load drops reported when compared with HIV-1-infected patients with similar baseline characteristics [34]. The genome of HIV-2 is very variable and there is a possibility BYL719 in vitro of under-quantification with the viral load assays; thus this response may be poorer still. Regardless of whether HIV-2 RNA is detectable or not, blood should be sent to a specialist HIV-2 viral load testing laboratory for quantification in an alternative assay in all patients where there is a low CD4 cell count. Viral load testing in the United Kingdom is performed at the following centres: Prof. Deenan Pillay/Dr Bridget Ferns Department of Virology Royal Free & University College London Medical School Windeyer Building 46 Cleveland St London W1T 4JF Tel: 0207 6799490/9483 Fax: 0207 5805896 E-mail: [email protected] Dr Duncan Clark/Dr Wnt mutation David Bibby Department of Virology Barts and The London NHS Trust Pathology and Pharmacy Building 80 Newark St London E1 2ES Tel: 02032460358 Fax: 02032460325 E-mail: [email protected]
The UK HIV-2 reference laboratory is based new at the HPA in Colindale and is led by: Dr Jennifer Tosswill Health Protection Agency Sexually Transmitted and Blood Borne Virus Laboratory 61 Colindale Avenue London NW9 5HT Tel: 020 8327 6274 E-mail: [email protected] HIV-2 genotyping can be performed by: Dr Erasmus Smit Consultant Virologist West Midlands Public Health Laboratory Health Protection Agency Birmingham Heartlands Hospital Bordesley Green East Birmingham B9 5SS Tel: 0121 424 1239 Fax: 0121 772 6229 E-mail: [email protected] The laboratories should be contacted in advance of sending specimens to discuss appropriate
samples and the conditions for transporting them. In individuals with undetectable HIV-2 RNA, CD4 cell count may be the only method to identify whether an individual with HIV-2 infection needs treatment and whether that treatment regimen is effective. When detectable, the CD4 cell count decline correlates with HIV-2 RNA viral load and therefore, because of the undetectable or low viral load observed in HIV-2-infected patients, CD4 cell counts can remain stable for many years. However, CD4 cell counts can decline rapidly in those with a high viral load, the rate of decline being the same as in HIV-1-infected patients at comparable viral loads. High CD4 percentage is significantly associated with survival [20].