The spectrum of reported autoimmune phenomena in HIV infected patients is unexpectedly broad and - owing to the current efficacious treatment regimes - increasing. The likelihood of the occurrence of autoimmune phenomena correlates with a high CD4 count, consequently they are found most frequently soon after infection or after immune reconstitution. It is likely that recent developments, namely the recommendation to treat all patients regardless of their CD4 count, may lead to a further increase in autoimmune phenomena in HIV infected patients. In contrast to the abundance of data of rheumatological and hematological autoimmune disease in HIV infected patients, no systematic study exists which has analyzed the prevalence of autoimmune blistering disease and/or associated autoantibodies in these patients.

The investigators therefore intend to determine the prevalence of selected autoantibodies in our HIV cohort in relation to uninfected controls. According to recent guidelines, all HIV infected patients should receive anti-retroviral treatment at the earliest time point possible, making the restoration of the immune system more likely and leading to a further alignment of the life expectancy relative to age matched, uninfected controls. As a consequence, the incidence of AIBD, especially of bullous pemphigoid, for which age is the single most important risk factor, may rise.

In total, knowledge about the prevalence of AIBD specific auto antibodies might be supportive in the diagnosis of these conditions in the future.

So far no systematic studies exist about the prevalence and incidence of autoimmune blistering disease (AIBD) in HIV infected patients. Various case reports have been published, though the overall frequency appears to be low. The aim of this project is to investigate the frequency of various autoantibodies specific for various AIBD such as bullous pemphigoid, epidermolysis bullosa acquisita and paraneoplastic pemphigus using commercially available ELISA (BPAG1/2, desmoglein 1/3, collagen type VII, envoplakin) as well as indirect immunofluorescence. The knowledge of the frequency of these auto-antibodies in HIV infected patients may elucidate their clinical significance and also help in the diagnosis of AIBD in HIV infected patients.

In this cross sectional study all HIV infected patients at the HIV outpatient clinic (4-Süd) of the Department of Dermatology of Vienna's Medical University will be asked to participate in this study. Currently, the cohort includes approx. 1400 HIV infected patients and it is assumed that at least 600 patients will take part. In addition, it is intended to recruit 300 HIV negative patients who wish to get tested for HIV or require counselling for post-exposure prophylaxis. After receiving the informed consent, 4.5ml of blood will be collected during a routine medical check-up and the aforementioned tests performed.

The primary outcome is the prevalence of BPAG1/2 in HIV infected patients in comparison to uninfected, age matched controls. BPAG1/2 has been chosen as the primary end point given that bullous pemphigoid has the highest frequency among all AIBD. Secondary outcome measure will encompass the prevalence of auto antibodies against desmoglein1/3, collagen type VII, envoplakin as well as results from indirect immunofluorescence studies.

Inclusion Criteria:

• age ≥ 18 years
• signed informed consent

Exclusion Criteria:

• unwillingness to participate in the study
• pregnancy

- all HIV infected patients (confirmed by ELISA, WB, and PCR) at the HIV outpatient clinic (4-Süd) of the Department of Dermatology of Vienna's Medical University

and

- all HIV negative patients at the HIV outpatient clinic (4-Süd) of the Department of Dermatology of Vienna's Medical University who wish to get tested for HIV or require counselling for post-exposure prophylaxis