Kaposi sarcoma herpes virus antibody response and viremia following highly active antiretroviral therapy in the Swiss HIV Cohort study

Kaposi's Sarcoma-Associated Herpesvirus, the Etiological Agent of All Epidemiological Forms of Kaposi's Sarcoma

Simple Summary

Kaposi’s sarcoma-associated herpesvirus (KSHV) is one of the seven oncogenic viruses currently recognized by the International Agency for Research on Cancer. Its presence for Kaposi’s sarcoma development is essential and knowledge on the oncogenic process has increased since its discovery in 1994. However, some uncertainties remain to be clarified, in particular on the exact routes of transmission and disparities in KSHV seroprevalence and the prevalence of Kaposi’s sarcoma worldwide. Here, we summarized the current data on the KSHV viral particle’s structure, its genome, the replication, its seroprevalence, the viral diversity and the lytic and latent oncogenesis proteins involved in Kaposi’s sarcoma. Lastly, we reported the environmental, immunological and viral factors possibly associated with KSHV transmission that could also play a role in the development of Kaposi’s sarcoma.

Abstract

Kaposi’s sarcoma-associated herpesvirus (KSHV), also called human herpesvirus 8 (HHV-8), is an oncogenic virus belonging to the Herpesviridae family. The viral particle is composed of a double-stranded DNA harboring 90 open reading frames, incorporated in an icosahedral capsid and enveloped. The viral cycle is divided in the following two states: a short lytic phase, and a latency phase that leads to a persistent infection in target cells and the expression of a small number of genes, including LANA-1, v-FLIP and v-cyclin. The seroprevalence and risk factors of infection differ around the world, and saliva seems to play a major role in viral transmission. KSHV is found in all epidemiological forms of Kaposi’s sarcoma including classic, endemic, iatrogenic, epidemic and non-epidemic forms. In a Kaposi’s sarcoma lesion, KSHV is mainly in a latent state; however, a small proportion of viral particles (<5%) are in a replicative state and are reported to be potentially involved in the proliferation of neighboring cells, suggesting they have crucial roles in the process of tumorigenesis. KSHV encodes oncogenic proteins (LANA-1, v-FLIP, v-cyclin, v-GPCR, v-IL6, v-CCL, v-MIP, v-IRF, etc.) that can modulate cellular pathways in order to induce the characteristics found in all cancer, including the inhibition of apoptosis, cells’ proliferation stimulation, angiogenesis, inflammation and immune escape, and, therefore, are involved in the development of Kaposi’s sarcoma.

Kaposi Sarcoma in HIV-positive Solid-Organ Transplant Recipients: A French Multicentric National Study and Literature Review

BACKGROUND

Kaposi sarcoma is a vascular tumor related to herpesvirus-8 and is promoted by immunosuppression. For the last 15 years, human immunodeficiency virus (HIV) patients have had access to organ transplantation. The dual immunosuppression of HIV and immunosuppressive treatments might increase the risk and severity of Kaposi sarcoma.

METHODS

We conducted a multicentric retrospective study by collecting cases from French databases and society members of transplanted patients, among which 7 HIV-infected patients who subsequently developed Kaposi sarcoma were included.

RESULTS

In the CRISTAL database (114 511 patients) and the DIVAT (Données Informatisées et VAlidées en Transplantation) database (19 077 patients), the prevalence of Kaposi sarcoma was 0.18% and 0.46%, respectively, in transplanted patients; these values compare with 0.66% and 0.50%, respectively, in transplanted patients with HIV. The median time from HIV infection to Kaposi sarcoma was 20 years. Kaposi sarcoma occurred during the first year after transplantation in most cases, whereas HIV viral load was undetectable. Only 2 patients had visceral involvement. Five patients were treated with conversion of calcineurin inhibitor to mammalian target of rapamycin inhibitor, and 5 patients were managed by decreasing immunosuppressive therapies. At 1 year, 4 patients had a complete response, and 3 had a partial response.

CONCLUSIONS

In our study, Kaposi sarcoma in transplanted patients with HIV did not show any aggressive features and was treated with the usual posttransplant Kaposi sarcoma management protocol.

Interferon lambda 3/4 polymorphisms are associated with AIDS-related Kaposi's sarcoma

BACKGROUND

Kaposi's sarcoma, the most common AIDS-related cancer, represents a major public concern in resource-limited countries. Single nucleotide polymorphisms within the Interferon lambda 3/4 region (IFNL3/4) determine the expression, function of IFNL4, and influence the clinical course of an increasing number of viral infections.

OBJECTIVES

To analyze whether IFNL3/4 variants are associated with susceptibility to AIDS-related Kaposi's sarcoma among MSM enrolled in the Swiss HIV Cohort Study (SHCS).

METHODS

The risk of developing Kaposi's sarcoma according to the carriage of IFNL3/4 SNPs rs8099917 and rs12980275 and their haplotypic combinations was assessed by using cumulative incidence curves and Cox regression models, accounting for relevant covariables.

RESULTS

Kaposi's sarcoma was diagnosed in 221 of 2558 MSM Caucasian SHCS participants. Both rs12980275 and rs8099917 were associated with an increased risk of Kaposi's sarcoma (cumulative incidence 15 versus 10%, P = 0.01 and 16 versus 10%, P = 0.009, respectively). Diplotypes predicted to produce the active P70 form (cumulative incidence 16 versus 10%, P = 0.01) but not the less active S70 (cumulative incidence 11 versus 10%, P = 0.7) form of IFNL4 were associated with an increased risk of Kaposi's sarcoma, compared with those predicted not to produce IFNL4. The associations remained significant in a multivariate Cox regression model after adjustment for age at infection, combination antiretroviral therapy, median CD4+ T-cell count nadir and CD4+ slopes (hazard ratio 1.42, 95% confidence interval 1.06-1.89, P = 0.02 for IFLN P70 versus no IFNL4).

CONCLUSION

This study reports for the first time an association between IFNL3/4 polymorphisms and susceptibility to AIDS-related Kaposi's sarcoma.

Seroprevalence of Kaposi's sarcoma-associated herpesvirus among HIV-infected Uygurs in Xinjiang, China

Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiological agent of Kaposi's sarcoma (KS), which primarily affects human immunodeficiency virus (HIV)-infected adults with advanced immunodeficiency. Xinjiang province in China is an endemic area for Kaposi's sarcoma (KS), however, currently, only limited data for KSHV infection among HIV-infected individuals living in this endemic area is available. A cross-sectional study of 86 HIV positive participants was conducted in Xinjiang, China from 2014 through 2015. Plasma samples were collected and screened for KSHV and HIV infection. HIV pol gene and KSHV ORF-K1 gene were amplified and sequenced, genotypes were determined by phylogenetic analysis. Over all, prevalence was 48.9% (42/86; 95%CI 38.4-59.3%) for KSHV. Only CRF07_BC subtype has been identified among all these HIV positive individuals, while the subtype A and C of KSHV were detected in the participants. Meanwhile, we found that those with high CD4 counts (>500) showed a lower anti-KSHV titer, compared with other groups. Our study indicated a high prevalence of KSHV among HIV positive individuals in Xinjiang, China. Thus, management of HIV/AIDS patients should include KSHV screen and should consider the risk of KSHV-associated malignancies.

Human papillomavirus antibody response following HAART initiation among MSM

OBJECTIVE

To describe effects of HAART on high-risk human papillomavirus (HPV) antibody response in HIV-positive MSM and the meaning of this response for subsequent HPV-related cancer risk.

DESIGN

Prospective seroepidemiological study of 281 HIV-positive MSM initiating HAART between 1995 and 2004 in the Swiss HIV Cohort Study.

METHODS

For each individual, two serum samples, one at HAART initiation (pre-HAART) and another 24 months later (post-HAART), were tested for L1 antibodies to HPV6, 11, 16, 18, 31, 33, 35, 45, 52 and 58, as well as HPV16-E6 antibodies, using a multiplex serology assay. Identification of HPV-related cancer included data linkage with Swiss cancer registries.

RESULTS

Pre-HAART, 45.2% were seropositive for any high-risk HPV-L1 and 32.4% for HPV16-L1. Sexual intercourse during the last 6 months was the only evaluated factor associated with L1 seropositivity pre-HAART. Seropositivity increased post-HAART to 60.5% for any high-risk HPV-L1 [prevalence ratio versus pre-HAART = 1.34, 95% confidence interval (CI) 1.14-1.57] and 48.0% for HPV16-L1 (prevalence ratio versus pre-HAART = 1.48, 95% CI 1.20-1.83), and seroconversion was significantly associated with both lower CD4 cell count and CD4/CD8 ratio (P < 0.01). Only one individual was HPV16-E6-seropositive pre-HAART, but two more seroconverted post-HAART. Anal cancer incidence among the three HPV16-E6-positives post-HAART was significantly increased compared with HPV16-E6-negatives (incidence rate ratio = 63.1, 95% CI 1.1-1211).

CONCLUSION

HAART-related immune reconstitution increases HPV-specific antibody responses, which may discriminate future anal cancer risk in this high-risk population.

Cross-sectional and longitudinal investigation of human herpesvirus 8 seroprevalence in HIV-1-infected individuals in Osaka, Japan

INTRODUCTION

High human herpesvirus 8 (HHV-8) seroprevalence has been reported in men who have sex with men (MSM) and are infected with HIV-1. However, it is unclear when they become infected with HHV-8. Thus, we conducted cross-sectional and longitudinal investigations of HHV-8 seroprevalence in HIV-1-infected individuals in Osaka, Japan.

PATIENTS AND METHODS

Plasma was collected from 121 individuals infected with HIV-1 and the anti-HHV-8 antibody titer was measured using an enzyme-linked immunosorbent assay with whole virus lysate. Subjects were classified into those with and without a past medical history of HHV-8-associated disease; the latter group was then classified into 3 subgroups based on the assumed route of HIV-1 infection: blood products, homosexual contact, and other routes. HHV-8 seroprevalence was compared among the groups and measured again approximately 3 years after the baseline measurement. The relationship between HHV-8 seropositivity and possible associated factors was also investigated.

RESULTS

All 15 subjects with HHV-8-associated disease were seropositive, and all 11 subjects in the blood product group were seronegative. In the MSM group, 25 (30%) of 79 subjects were HHV-8 seropositive and, in the non-MSM group, 1 (6%) of 16 subjects was (p < 0.0001). In the longitudinal investigation, seroconversion was observed in 10 (19%) of 52 subjects in the MSM group who were seronegative at baseline. A correlation was observed between seroconversion and symptomatic syphilis (p = 0.0432).

CONCLUSIONS

HHV-8 seropositivity and seroconversion rates were high in HIV-1-infected MSM, suggesting that, currently, HHV-8 is an epidemic pathogen in this population.

Changes in Clinical Context for Kaposi's Sarcoma and Non-Hodgkin Lymphoma Among People With HIV Infection in the United States

PURPOSE

The biology of HIV-associated cancers may differ depending on immunologic and virologic context during development. Therefore, an understanding of the burden of Kaposi's sarcoma (KS) and non-Hodgkin lymphoma (NHL) relative to antiretroviral therapy (ART), virologic suppression, and CD4 count is important.

PATIENTS AND METHODS

KS and NHL diagnoses during 1996 to 2011 were identified among patients with HIV infection in eight clinical cohorts in the United States. Among patients in routine HIV clinical care, the proportion of cases in categories of ART use, HIV RNA, and CD4 count at diagnosis were described across calendar time. Person-time and incidence rates were calculated for each category.

RESULTS

We identified 466 patients with KS and 258 with NHL. In recent years, KS was more frequently diagnosed after ART initiation (55% in 1996 to 2001 v 76% in 2007 to 2011; P-trend = .02). The proportion of patients with NHL who received ART was higher but stable over time (83% overall; P-trend = .81). An increasing proportion of KS and NHL occurred at higher CD4 counts (P < .05 for KS and NHL) and with undetectable HIV RNA (P < .05 for KS and NHL). In recent years, more person-time was contributed by patients who received ART, had high CD4 counts and had undetectable HIV RNA, whereas incidence rates in these same categories remained stable or declined.

CONCLUSION

Over time, KS and NHL occurred at higher CD4 counts and lower HIV RNA values, and KS occurred more frequently after ART initiation. These changes were driven by an increasing proportion of patients with HIV who received effective ART, had higher CD4 counts, and had suppressed HIV RNA and not by increases in cancer risk within these subgroups. An improved understanding of HIV-associated cancer pathogenesis and outcomes in the context of successful ART is therefore important.

Longitudinal analysis of the humoral response to Kaposi's sarcoma-associated herpesvirus after primary infection in children

Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent for Kaposi's sarcoma (KS)-one of the most common pediatric cancers in sub-Saharan Africa-however, the factors that lead to disease progression are not fully understood. HIV infection, immunosuppression, and high KSHV viral load increase the risk of developing KS, suggesting that the loss of an effective anti-KSHV immune response may be an important risk factor. However, very little is known about the KSHV-specific immune response prior to KS and less is known about the anti-KSHV immune response during the very early stages of infection. We therefore prospectively followed a cohort of 86 Zambian children for 2 years after primary KSHV seroconversion to characterize the humoral immune response during the early stages of KSHV infection. Plasma, peripheral blood mononuclear cells, and oral swabs were collected from patients every 3 months and analyzed for KSHV-specific antibodies and presence of viral DNA. We observed an approximately 40% KSHV seropositive rate among infected children at time points after primary seroconversion, indicating that seroreversion is common after primary KSHV infection. At the time of primary KSHV seroconversion HIV-infected ART-naïve children had a more robust KSHV antibody response compared to HIV-infected children taking ART and HIV-uninfected children. Conversely, the longitudinal anti-KSHV antibody response was highly variable and did not correlate with available clinical information, HIV/ART status, or presence of KSHV DNA. Collectively, our data suggest that there is limited impact by the variations in the humoral immune response in young children after infection. J. Med. Virol. 88:1973-1981, 2016. © 2016 Wiley Periodicals, Inc.

Cancers attributable to infections among adults with HIV in the United States

OBJECTIVE

HIV-infected people are at increased risk of cancers of infectious origin. We estimated the burden of cancer attributable to infections among HIV-infected people in the United States in 2008.

DESIGN

Incidence rates for cancer sites associated with infections were estimated from record linkage between HIV/AIDS registries and cancer registries.

METHODS

Rates were applied to estimates of the population living with diagnosed HIV in the United States in 2008 to obtain the number of incident cancer cases. Site-specific attributable fractions and corresponding 95% confidence intervals (CIs) were estimated from infection prevalence among cancer cases. Infection prevalence data were derived from literature review of case series.

RESULTS

Of an estimated 6200 incident cancer cases (95% CI 6000-6500), 2500 (95% CI 2400-2700) were attributable to infection (attributable fraction = 40%, 95% CI 39-42). The most important infections were Kaposi sarcoma herpes virus, Epstein-Barr virus, and human papillomavirus, which together were responsible for 2200 new cancer cases (95% CI 2100-2400), mainly Kaposi sarcoma, lymphomas, and ano-genital cancers. The attributable fraction in HIV-infected people was highest in the age group 20-29 years (69%, 95% CI 65-72). MSM were the HIV transmission group with the highest attributable fraction (48%, 95% CI 46-50), due to the high incidence of both Kaposi sarcoma and anal cancer.

CONCLUSION

The very high fraction of cancer attributable to infection in HIV-infected people points to special opportunities to prevent these cancers, that is, avoidance, detection, and early treatment of cancer-associated infections, and universal early detection and uninterrupted treatment of HIV infection to avoid immunosuppression.

HIV and human herpesvirus 8 co-infection across the globe: Systematic review and meta-analysis

HIV-infection is an important risk factor for developing Kaposi sarcoma (KS), but it is unclear whether HIV-positive persons are also at increased risk of co-infection with human herpesvirus 8 (HHV-8), the infectious cause of KS. We systematically searched literature up to December 2012 and included studies reporting HHV-8 seroprevalence for HIV-positive and HIV-negative persons. We used random-effects meta-analysis to combine odds ratios (ORs) of the association between HIV and HHV-8 seropositivity and conducted random-effects meta-regression to identify sources of heterogeneity. We included 93 studies with 58,357 participants from 32 countries in sub-Saharan Africa, North and South America, Europe, Asia, and Australia. Overall, HIV-positive persons were more likely to be HHV-8 seropositive than HIV-negative persons (OR 1.99, 95% confidence interval [CI] 1.70-2.34) with considerable heterogeneity among studies (I(2) 84%). The association was strongest in men who have sex with men (MSM, OR 3.95, 95% CI 2.92-5.35), patients with hemophilia (OR 3.11, 95% CI 1.19-8.11), and children (OR 2.45, 95% CI 1.58-3.81), but weaker in heterosexuals who engage in low-risk (OR 1.42, 95% CI 1.16-1.74) or high-risk sexual behavior (OR 1.66, 95% CI 1.27-2.17), persons who inject drugs (OR 1.66, 95% CI 1.28-2.14), and pregnant women (OR 1.68, 95% CI 1.15-2.47), p value for interaction <0.001. In conclusion, HIV-infection was associated with an increased HHV-8 seroprevalence in all population groups examined. A better understanding of HHV-8 transmission in different age and behavioral groups is needed to develop strategies to prevent HHV-8 transmission.

Human herpesvirus 8 seroconversion in a population-based cohort of men in Tobago

Human herpesvirus 8 (HHV-8) is the causal agent of Kaposi's sarcoma (KS). In Tobago, KS is not common; however, HHV-8 seropositivity has been reported to be 39.9% in men with prostate cancer compared to <22.9% in healthier women and men. To understand HHV-8 transmission, we examined HHV-8 seroconversion and seroreversion, and risk factors for these changes in Tobago men. Serum specimens from a sub-cohort of Tobago Prostate Survey men, aged 40-81 years (n = 381/442), were collected at baseline and a subsequent visit between 3 and 9 years and tested for HHV-8 seropositivity using an immunofluorescence assay for antibodies against HHV-8 lytic antigens. Poisson distribution was used to calculate HHV-8 seroconversion and seroreversion rates and their 95% confidence intervals. Differences in baseline characteristics between HHV-seroconverters versus persistent HHV-8 seronegative men and HHV-8 seroreverters versus HHV-8 seropositive men were examined. HHV-8 seropositivity was 12.3% (N = 381) at baseline, with HHV-8 seropositivity significantly higher in increasing age groups, 40-49 (4.0%) to 70-81 (37.5%) years (P-value trend <0.0001). HHV-8 seroconversion and seroreversion rates were 0.23 per 100 person-years (95% C.I., 0.06-0.58) and 2.42 per 100 person-years (95% C.I., 0.89-5.26), respectively. There were significantly more HHV-8 seroconverters who reported "ever smoked cigarettes of >6 months" at baseline compared to HHV-8 persistent seronegative men (P-value = 0.03). Baseline characteristics of HHV-8 seroreverters did not differ from persistent seropositive men. Low HHV-8 seroconversion and seroreversion rates were found. Data suggest that HHV-8 transmission occurred at earlier ages, <40 years, in Tobago men.

New onset of kaposi sarcoma in a human immunodeficiency virus-1-infected homosexual man, despite early antiretroviral treatment, sustained viral suppression, and immune restoration

This is a rare case of new onset Kaposi sarcoma in a man infected with human immunodeficiency virus (HIV) and receiving antiretroviral treatment since primary HIV infection, with normal CD4⁺ cell count and suppressed viral load. The presentation questions the general understanding of Kaposi sarcoma as an acquired immune deficiency syndrome-defining disease occurring predominantly in severely immunocompromised patients infected with HIV.

A role for host activation-induced cytidine deaminase in innate immune defense against KSHV

Activation-induced cytidine deaminase (AID) is specifically induced in germinal center B cells to carry out somatic hypermutation and class-switch recombination, two processes responsible for antibody diversification. Because of its mutagenic potential, AID expression and activity are tightly regulated to minimize unwanted DNA damage. Surprisingly, AID expression has been observed ectopically during pathogenic infections. However, the function of AID outside of the germinal centers remains largely uncharacterized. In this study, we demonstrate that infection of human primary naïve B cells with Kaposi's sarcoma-associated herpesvirus (KSHV) rapidly induces AID expression in a cell intrinsic manner. We find that infected cells are marked for elimination by Natural Killer cells through upregulation of NKG2D ligands via the DNA damage pathway, a pathway triggered by AID. Moreover, without having a measurable effect on KSHV latency, AID impinges directly on the viral fitness by inhibiting lytic reactivation and reducing infectivity of KSHV virions. Importantly, we uncover two KSHV-encoded microRNAs that directly regulate AID abundance, further reinforcing the role for AID in the antiviral response. Together our findings reveal additional functions for AID in innate immune defense against KSHV with implications for a broader involvement in innate immunity to other pathogens.

Immune responses to pathogens rely heavily on the ability of B cells to generate a unique set of antibodies that can bind and eliminate the pathogen. Activation-induced cytidine deaminase (AID) is the enzyme specifically upregulated in activated B cells to diversify the antibody repertoire by introducing mutations within the antibody coding genes. Curiously, AID expression has been observed outside of activated B cells upon infection with a number of viral and bacterial pathogens. However, in such cases AID function is poorly characterized and often deemed inappropriate since its mutagenic activity can put the cell at risk for oncogenic transformation. In this study, we investigate the expression of AID in response to infection with an oncogenic human pathogen Kaposi's sarcoma-associated herpesvirus (KSHV) and the antibody-independent immune defense it exerts. We show that AID marks infected cells for elimination by natural killer (NK) cells and directly impinges on viral fitness. Furthermore, we uncover novel viral immune evasion strategies employed by KSHV to counteract AID. Together, our findings demonstrate a protective role for AID in the response to infection with an oncogenic virus such as KSHV and suggest that AID may actually limit transformation rather than serve as its culprit.

Professional antigen presenting cells in human herpesvirus 8 infection

Professional antigen presenting cells (APC), i.e., dendritic cells (DC), monocytes/macrophages, and B lymphocytes, are critically important in the recognition of an invading pathogen and presentation of antigens to the T cell-mediated arm of immunity. Human herpesvirus 8 (HHV-8) is one of the few human viruses that primarily targets these APC for infection, altering their cytokine profiles, manipulating their surface expression of MHC molecules, and altering their ability to activate HHV-8-specific T cells. This could be why T cell responses to HHV-8 antigens are not very robust. Of these APC, only B cells support complete, lytic HHV-8 infection. However, both complete and abortive virus replication cycles in APC could directly affect viral pathogenesis and progression to Kaposi's sarcoma (KS) and HHV-8-associated B cell cancers. In this review, we discuss the effects of HHV-8 infection on professional APC and their relationship to the development of KS and B cell lymphomas.

Trends in Kaposi's Sarcoma in Miami Beach from 1987 to 2007

Purpose. Kaposi's sarcoma (KS) is a rare low-grade vascular tumor associated with the human herpes virus 8. By analyzing the epidemiology, staging, and treatment of KS, we hoped to improve the quality of care at our institution. Methods. Review of the Mount Sinai Medical Center tumor registry database in Miami Beach, FL, USA, identified 143 cases of KS between January 1, 1987 and December 31, 2007. Results. The majority of patients were non-Hispanic whites, non smoking males diagnosed between 1987 and 1996. Most of the patients were HIV positive, with an equal percentage diagnosed with local or distant disease. Most patients received no chemotherapy or radiation. There were no significant differences in patient survival based on sex, HIV status, or radiation received. There was a trend toward improved survival among older patients who smoked, received no chemotherapy, and had localized stage at diagnosis. Multivariate analysis revealed that non-Hispanic whites had a significant worse survival than Hispanic whites (HR = 0.55, 95% CI (0.33, 0.90), P = 0.02). Patients diagnosed between 1987 and 1996 had a worse survival than those between 1997 and 2007 (HR = 0.33 (95% CI 0.19, 0.55), P < 0.0001). Conclusion. This large retrospective study provides further insight into KS. Ethnicity and date of diagnosis are important predictors of long-term survival.

Differences in Kaposi sarcoma-associated herpesvirus-specific and herpesvirus-non-specific immune responses in classic Kaposi sarcoma cases and matched controls in Sicily

Kaposi sarcoma (KS) might develop because of incompetent immune responses, both non-specifically and specifically against the KS-associated herpesvirus (KSHV). Peripheral blood mononuclear cells from 15 classic (non-AIDS) KS cases, 13 KSHV seropositives (without KS) and 15 KSHV-seronegative controls were tested for interferon-γ T-cell (enzyme-linked immunospot [Elispot]) responses to KSHV-latency-associated nuclear antigen (LANA), KSHV-K8.1 and CMV/Epstein-Barr virus (EBV) peptide pools. The forearm and thigh of each participant was also tested for delayed-type hypersensitivity (DTH) against common recall antigens. Groups were compared with Fisher exact test and multinomial logistic regression to calculate odds ratios (OR) and 95% confidence intervals (CI). A KSHV Elispot response was detected in 10 (67%) classic KS cases, 11 (85%) KSHV seropositives (without KS) and two (13%) seronegative controls. All four cases with KSHV-LANA responses had current KS lesions, whereas five of six cases with KSHV-K8.1 responses had no lesions (P = 0.048). No case responded to both LANA and K8.1. Compared with the seronegative controls, the risk for classic KS was inversely related to DTH in the thigh (OR 0.71, 95% CI 0.55-0.94, P = 0.01), directly associated with DTH in the forearm (OR 1.35, 95% CI 1.02-1.80, P = 0.04) and tended to be increased fivefold per KSHV Elispot response (OR 5.13, 95% CI 0.86-30.77, P = 0.07). Compared with KSHV seropositives (without KS), the risk for classic KS was reduced fivefold (OR 0.20, CI 0.03-0.77, P = 0.04) per KSHV response. The CMV/EBV Elispot responses were irrelevant. Deficiency of both KSHV-specific and KSHV-non-specific immunity is associated with classic KS. This might clarify why Kaposi sarcoma responds to immune reconstitution.