Human immunodeficiency virus (HIV) is an infection by one of two viruses (HIV1 and HIV2) that progressively destroy white blood cells (lymphocytes) that protect the body against illness and infection.

This can lead to the development of acquired immunodeficiency syndrome (AIDS), a collection of illnesses that affect people infected with HIV. A person with HIV is considered to have AIDS when they develop an AIDS defining illness.

According to the latest statistics published by the Health Protection Agency, an estimated 73,000 people are living with HIV in the UK; of these approximately 21,600 are unaware of their infection.  In 2006, 7,800 new HIV diagnoses were reported, equating to 13 persons newly diagnosed per 100,000 population. This number is in the same range as the estimate for 2005 (7,900) indicating that the annual number of new diagnoses may have stabilised. 

Two fifths of newly diagnosed persons in 2006 probably acquired their infection in the UK, of whom approximately two thirds were men who have sex with men.  However there continues to be a steady increase in heterosexual HIV transmission within the UK, especially in some ethnic minorities. There are also signs that transmission of HIV among injecting drug users may be increasing.

Over the past decade there has been a major shift in the geographical distribution of HIV-infected persons across the UK. Although London saw the largest numerical increase of residents accessing HIV-related care from 9,200 in 1997 to 24,000 in 2006, the proportional increase over this period (160%) was lower than in all other areas (350%). For example the largest proportional increase occurred in the East of England (610%) from 550 in 1997 to 3,300 in 2006, and between 2005 and 2006, the largest proportional increase was in Yorkshire and The Humber.

The transmission of HIV requires contact with a body fluid that contains infected cells or virus particles such as blood, semen or vaginal secretions. Unprotected sex is the most common way in which people become infected with HIV. Infection can also result from the injection or infusion of contaminated blood through a blood transfusion, the sharing of needles by drug users or an accidental needle prick in a healthcare setting. Infection can also be passed from an infected mother to a child during pregnancy, childbirth or through breast-feeding.

It is not currently thought possible to get HIV through daily social contact such as social kissing, touching, sharing a toilet and eating facilities, or through coughing, tears and sneezing.

There is currently no cure for HIV; however there are many drugs available that can reduce the level of HIV in the body.  Although they cannot eliminate the virus from the body they can slow down the production of the HIV virus and can drive down the amount of the virus in the body, reducing further damage to the immune system.  The aim of treatment is to reduce the quantity of the virus to a minimum, helping to prolong life and good health.

Drugs used to treat HIV are often referred to as anti-HIV or antiretroviral drugs. To provide patients with the best chance of reducing the amount of HIV in their blood, a powerful combination of at least three antiretroviral drugs are prescribed. This is called combination therapy or HAART (Highly Active Antiretroviral Therapy) and is currently the standard way to treat most people with HIV. 

Since its introduction in the mid-1990s, HAART has helped transform the course of HIV infection from a disease that inevitably progressed to death, into a chronic condition requiring long-term clinical management and monitoring.  Its widespread availability and uptake has resulted in a dramatic increase in life expectancy and quality of life among individuals with HIV in the developed world.

Currently, the main types of antiretroviral drugs are:

• Nucleoside analogue reverse transcriptase inhibitors (NRTIS), which target an HIV enzyme called reverse transcriptase
• Nucleotide analogue reverse transcriptase inhibitors (NtRTIs), which target reverse transcriptase in a similar way to NRTIs
• Non-nucleoside reverse transcriptase inhibitors (NNRTIs), which also target reverse transcriptase, but in a different way to NRTIs and NtRTIs
• Protease inhibitors (PIs), which target an HIV enzyme called protease
• Fusion inhibitors, which target a receptor (gp41) on cells of the immune system and prevent the virus from fusing with the cell in order to gain entry
• CCR5 antagonists, which selectively bind to a different receptor on the cell surface (CCR5), preventing the virus that uses this receptor from entering cells
• Integrase inhibitors, a new class of antiretroviral drugs, which target an HIV protein called integrase. 

Antiretroviral therapy usually involves a combination of three antiretrovirals. The general consensus from British doctors is that it is best to start with a combination that involves a non-nucleoside reverse transcriptase inhibitor (NNRTI), or “boosted” protease inhibitors.  This is taken with a combination of two nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs). 

It is very common for people to experience side-effects with some anti-HIV drugs, particularly during the first few weeks of treatment, such as headache, nausea, diarrhoea and tiredness. As a result, antiretroviral therapy is tailored to the needs and circumstances of the individual and decisions on which drug combinations to pursue are made between individual patients and their consultant in order to help reduce these side-effects. 

Antiretroviral therapy is a long-term commitment and in order to achieve the best results it is important that HIV drugs are taken exactly as prescribed; this is referred to as “adherence”.

HIV reproduces itself very quickly, making billions of new viruses every day.  However the virus often makes mistakes when copying itself, making each new generation slightly different from the previous.  These structural differences are called mutations.  Some mutations occur in the parts of HIV which are targeted by anti-HIV drugs. This can result in strains of HIV that have reduced sensitivity to drugs.  These HIV strains are called drug-resistant.

Resistance to current HIV therapies is one of the leading challenges in effective antiretroviral treatment. 

Integrase is one of three HIV enzymes required by the virus in order to replicate (reproduce); the other two key enzymes are reverse transcriptase and protease.

Integrase is responsible for inserting (integrating) the viral DNA into the DNA of the host cell.   By preventing this essential function, an integrase inhibitor affects the ability of the virus to replicate and thus can help to prevent infection of other cells, and to reduce the viral load – the amount of virus present in the blood.

Before 2008, drugs were available that inhibited the HIV protease and reverse transcriptase enzymes. These therapies include protease inhibitors, nucleoside (and nucleotide) reverse transcriptase inhibitors, and non-nucleoside reverse transcriptase inhibitors.  Until MSD introduced 'Isentress'^® (generic name, raltegravir) there were no approved drugs that targeted the integration step of the human immunodeficiency virus (HIV-1) lifecycle.

For this reason, integrase inhibitors represent an important new treatment option in antiretroviral therapy.  An integrase inhibitor can potentially be used in combination with any of the currently available drugs that target different points in the replication cycle of HIV, a key factor when combination therapy is regarded as an important requirement to protect against the development of viral resistance.

Raltegravir is the first integrase inhibitor licensed for the treatment of human immunodeficiency virus (HIV-1) infection.  It is indicated for use in combination with other antiretroviral medicinal products for the treatment of HIV-1 infection in treatment-experienced adult patients with evidence of HIV-1 replication despite ongoing antiretroviral therapy.  Raltegravir comes as a 400mg tablet, to be taken twice daily, with or without food.

For additional information, please see the patient information leaflet or the Summary of Product Characteristics.

The prognosis for people living with HIV has changed dramatically since the first cases of AIDS were diagnosed in the early 1980s. The timely use of effective treatments has led to dramatic improvements in prognosis, and many doctors specialising in the treatment of HIV now believe that as long as a person with HIV receives effective anti-HIV treatment before their immune system has been too damaged by the virus, and if they take their drugs properly and can tolerate them, then they could live a more or less normal life span.