Heterogeneity and breadth of host antibody response to KSHV infection demonstrated by systematic analysis of the KSHV proteome

Kaposi's sarcoma herpesvirus seroprevalence among blood donors in Uganda

BACKGROUND

Kaposi's sarcoma herpesvirus (KSHV) causes a life-long infection that can progress to several types of KSHV-associated diseases. There is evidence for transfusion transmission of KSHV. In endemic regions, such as sub-Saharan African, KSHV seroprevalence is >40%. However, previous studies of blood donors utilized immunoassays that detect KSHV-associated disease-specific antigens, which may underestimate the true burden of KSHV in a healthy population.

STUDY DESIGN AND METHODS

We utilized samples from an on-going transfusion transmitted infection clinical trial to estimate the seroprevalence of KSHV among 4921 blood donations from healthy donors in Uganda collected between October 2019 and December 2022. A multiplexed bead-based assay was used to measure plasma IgG against five antigens encoded by the K8.1, K10.5, ORF73, ORF38, and ORF25 genes of KSHV. Significant associations between donor characteristics and seroprevalence were assessed by chi-square tests.

RESULTS

Overall, KSHV seroprevalence was 69.1%. Seroprevalence was higher in units collected from older donors compared with younger donors and male donors (71.9% [95% confidence interval (CI) = 70.4%-73.3%]) compared with female donors (61.3% [95% CI = 58.6%-64.0%]; p < .001). KSHV seroprevalnce was higher among units collected from donors positive for T. pallidum (82.5% [95% CI = 73.8%-89.3%]) compared with units collected from donors who were negative (68.8% [95% CI = 67.5%-70.1%]; p < .001). KSHV seroprevalence was higher in units that tested positive for HIV, HBV, or HCV, though these results were not statistically significant.

CONCLUSION

Given the high seroprevalence and limited availability of lab assays that detect active KSHV infections, methods such as leukoreduction or pathogen reduction should be considered to potentially reduce the risk of transfusion transmission of KSHV.

Structures of Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus virions reveal species-specific tegument and envelope features

Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV) are classified into the gammaherpesvirus subfamily of Herpesviridae, which stands out from its alpha- and betaherpesvirus relatives due to the tumorigenicity of its members. Although structures of human alpha- and betaherpesviruses by cryogenic electron tomography (cryoET) have been reported, reconstructions of intact human gammaherpesvirus virions remain elusive. Here, we structurally characterize extracellular virions of EBV and KSHV by deep learning-enhanced cryoET, resolving both previously known monomorphic capsid structures and previously unknown pleomorphic features beyond the capsid. Through subtomogram averaging and subsequent tomogram-guided sub-particle reconstruction, we determined the orientation of KSHV nucleocapsids from mature virions with respect to the portal to provide spatial context for the tegument within the virion. Both EBV and KSHV have an eccentric capsid position and polarized distribution of tegument. Tegument species span from the capsid to the envelope and may serve as scaffolds for tegumentation and envelopment. The envelopes of EBV and KSHV are less densely populated with glycoproteins than those of herpes simplex virus 1 (HSV-1) and human cytomegalovirus (HCMV), representative members of alpha- and betaherpesviruses, respectively. Also, we observed fusion protein gB trimers exist within triplet arrangements in addition to standalone complexes, which is relevant to understanding dynamic processes such as fusion pore formation. Taken together, this study reveals nuanced yet important differences in the tegument and envelope architectures among human herpesviruses and provides insights into their varied cell tropism and infection.

IMPORTANCE

Discovered in 1964, Epstein-Barr virus (EBV) is the first identified human oncogenic virus and the founding member of the gammaherpesvirus subfamily. In 1994, another cancer-causing virus was discovered in lesions of AIDS patients and later named Kaposi's sarcoma-associated herpesvirus (KSHV), the second human gammaherpesvirus. Despite the historical importance of EBV and KSHV, technical difficulties with isolating large quantities of these viruses and the pleiomorphic nature of their envelope and tegument layers have limited structural characterization of their virions. In this study, we employed the latest technologies in cryogenic electron microscopy (cryoEM) and tomography (cryoET) supplemented with an artificial intelligence-powered data processing software package to reconstruct 3D structures of the EBV and KSHV virions. We uncovered unique properties of the envelope glycoproteins and tegument layers of both EBV and KSHV. Comparison of these features with their non-tumorigenic counterparts provides insights into their relevance during infection.

Comparison of the indirect immunofluorescence assay and a commercial ELISA to detect KSHV antibodies

Kaposi's sarcoma-associated herpesvirus (KSHV) is an oncogenic virus involved in several diseases. The gold standard for KSHV sero diagnosis remains the indirect immunofluorescence assay (IFA), which is time-consuming and operator-dependent. We compared this method with an enzyme-linked immunosorbent assay (ELISA) targeting solubilized KSHV whole-genome extract among positive (n = 49, including 76% of HIV-infected patients) and negative (n = 14) control groups. We also included 14 sera with equivocal IFA results. ELISA showed better performance in detecting KSHV antibodies (McNemar's test, P = 0.0455). The sensitivity and specificity of both methods were 79% (64-89) and 100% (66-100) for the IFA, respectively, and 94% (83-99) and 100% (66-100) for ELISA, respectively. All IFA equivocal results were either negative or positive with ELISA. ELISA is more reliable and could be a good alternative for determining KSHV serological status, particularly in the context of immunocompromised patients and equivocal serology with the IFA.IMPORTANCEKaposi's sarcoma-associated herpesvirus (KSHV) sero status remains challenging because no perfect reference is available for the detection of KSHV antibodies. The current gold-standard method, the indirect immunofluorescence assay (IFA), has a very good specificity of close to 100%, but a lower sensitivity of around 80-85%, which decreases to 64-67% in immunocompromised patients. Additionally, this method is time-consuming and operator-dependent compared with new serological assays such as the enzyme-linked immunosorbent assay (ELISA). Thus, further research is still needed to improve KSHV sero diagnosis. Here, we compare the KSHV IgG ELISA kit assay (Advanced Biotechnologies Inc) with the gold-standard IFA, targeting the LANA-1 protein from latent BC-3 cell lines.

Increased human herpesvirus-8 neutralizing response during remission from Kaposi's sarcoma

Human herpesvirus-8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus, is a human oncogenic herpesvirus that is responsible for several diseases including Kaposi's sarcoma (KS). KS prevalence varies dramatically, although emergence increases considerably with human immunodeficiency virus -1 (HIV-1) co-infection, making it one of the most common cancers in HIV-1 patients and sub-Saharan African men, even prior to the HIV-1 epidemic in Africa. Studies have shown that neutralizing antibodies exist in HHV-8-infected sera, which are most likely targeted to viral lytic surface glycoproteins, such as glycoprotein K8.1 (gpK8.1) and gHgL. Fifty-eight HHV-8-positive serum samples were tested for the levels of gpK8.1- and gHgL-binding antibodies and in vitro HHV-8-neutralizing capacity. Each sample was then categorized according to the disease status, which included asymptomatic infection, active KS and remission from KS, and the three measured parameters were compared between the disease groups. We show that neutralizing capacity in infected patient sera increases with remission of KS. Interestingly, antibodies targeting gpK8.1, but not gHgL, were also found to be increased during active disease and remission. Comparison of neutralizing capacity and antibody levels on an individual patient basis revealed that antibody levels, primarily targeting gHgL, are correlated with serum neutralizing response in sub-lingual Kaposi sarcoma (SLK) cells. Adsorption of gHgL or gpK8.1 antibodies from human sera removed the neutralizing response in SLK cells, although some non-specific removal of antibodies from the sera means that this result should be interpreted with caution. Taken collectively, these results suggest that glycoproteins, such as gHgL, are targets for neutralizing antibodies. Furthermore, our data imply that recovery from KS is associated with increased neutralizing capacity, suggesting that neutralizing antibodies may contribute to KS resolution. However, it is vital for further work to be completed in order to elucidate this relationship.

Factors affecting Kaposi's sarcoma-associated herpesvirus transmission in rural Ugandan households, a longitudinal study

BACKGROUND

We report the impact of HIV infection within a household on oral Kaposi's sarcoma-associated herpesvirus (KSHV) shedding.

METHODS

We enrolled 469 individuals from 90 households. Mouthwash rinse samples collected at three monthly visits were analyzed for KSHV DNA using quantitative polymerase chain reaction (qPCR). Generalized linear mixed effects logistic models were applied to analyze factors associated with KSHV ever shedding, and among shedders, always versus intermittent shedding. Linear mixed effects models were applied to models of KSHV viral loads. Intraclass correlation coefficients (ICCs) were calculated to assess the contribution of household-level factors to variations in shedding probabilities. Hotspot analyses of geospatial feature clusters were calculated using Getis-Ord Gi* statistic and visualized using inverse distance weighted interpolation.

RESULTS

Analyses included 340 KSHV seropositive individuals, aged 3 + years, with qPCR results from 89 households. Forty households had 1 + persons living with HIV (PLWH), while 49 had none. Among participants, 149(44%) were KSHV ever shedders. Of 140 who shed KSHV at two or more visits, 34(24%) were always shedders. Increasing number of KSHV seropositive household members was significantly associated with ever shedding [Odds ratio(OR) (95% Confidence Interval(95%CI)):1.14(1.03,1.26);p = 0.013]. Among KSHV shedders, a statistically significant age-related trend was identified with 10-19 years being more likely to be always shedders (type III test p = 0.039) and to have higher viral loads (type III test p = 0.027). In addition, higher viral loads were significantly associated with increasing number of household members [coefficient(95%CI):0.06(0.01,0.12);p = 0.042], increasing number of KSHV seropositive members [coefficient(95%CI):0.08(0.01,0.15);p = 0.021], and living in households with 1 + PLWH [coefficient(95%CI):0.51(0.04,0.98);p = 0.033]. Always shedders exhibited higher viral loads than intermittent shedders [coefficient(95%CI):1.62(1.19,2.05);p < 0.001], and viral loads increased with the number of visits where KSHV DNA was detected in saliva (type III test p < 0.001). Household-level factors attributed for 19% of the variability in KSHV shedding (ICC:0.191;p = 0.010). Geospatial analysis indicated overlapping hotspots of households with more KSHV seropositive individuals and KSHV shedders, distinct from areas where PLWH were clustered.

DISCUSSION

KSHV oral shedding is influenced by multiple factors at the individual, household, and regional levels. To mitigate ongoing KSHV transmission a comprehensive understanding of factors contributing to oral KSHV reactivation and transmission within households is needed.

HIV-associated cancers and lymphoproliferative disorders caused by Kaposi sarcoma herpesvirus and Epstein-Barr virus

SUMMARYWithin weeks of the first report of acquired immunodeficiency syndrome (AIDS) in 1981, it was observed that these patients often had Kaposi sarcoma (KS), a hitherto rarely seen skin tumor in the USA. It soon became apparent that AIDS was also associated with an increased incidence of high-grade lymphomas caused by Epstein-Barr virus (EBV). The association of AIDS with KS remained a mystery for more than a decade until Kaposi sarcoma-associated herpesvirus (KSHV) was discovered and found to be the cause of KS. KSHV was subsequently found to cause several other diseases associated with AIDS and human immunodeficiency virus (HIV) infection. People living with HIV/AIDS continue to have an increased incidence of certain cancers, and many of these cancers are caused by EBV and/or KSHV. In this review, we discuss the epidemiology, virology, pathogenesis, clinical manifestations, and treatment of cancers caused by EBV and KSHV in persons living with HIV.

Factors affecting Kaposi's sarcoma-associated herpesvirus transmission in rural Ugandan households, a longitudinal study

Background

We report the impact of HIV infection within a household on oral Kaposi's sarcoma-associated herpesvirus (KSHV) shedding.

Methods

We enrolled 469 individuals from 90 households. Mouthwash rinse samples collected at three monthly visits, were analyzed for KSHV DNA using quantitative polymerase chain reaction (qPCR). Generalized linear mixed effects logistic models were applied to analyze factors associated with KSHV ever shedding, and among shedders, always versus intermittent shedding. Linear mixed effects models were applied to models of KSHV viral loads. Intraclass correlation coefficients (ICCs) were calculated to assess the contribution of household-level factors to variations in shedding probabilities. Hotspot analyses of geospatial feature clusters were calculated using Getis-Ord Gi* statistic and visualized using inverse distance weighted interpolation.

Results

Analyses included 340 KSHV seropositive individuals, aged 3 + years, with qPCR results from 89 households. Forty households had 1 + persons living with HIV (PLWH), while 49 had none. Among participants, 149(44%) were KSHV ever shedders. Of 140 who shed KSHV at two or more visits, 34(24%) were always shedders. Increasing number of KSHV seropositive household members was significantly associated with ever shedding [Odds ratio(OR) (95% Confidence Interval(95%CI)):1.14(1.03,1.26);p = 0.013]. Among KSHV shedders, a statistically significant age-related trend was identified with 10-19 years being more likely to be always shedders (type III test p = 0.039) and to have higher viral loads (type III test p = 0.027). In addition, higher viral loads were significantly associated with increasing number of household members [coefficient(95%CI):0.06(0.01,0.12);p = 0.042], increasing number of KSHV seropositive members [coefficient(95%CI):0.08(0.01,0.15);p = 0.021], and living in households with 1 + PLWH [coefficient(95%CI):0.51(0.04,0.98);p = 0.033]. Always shedders exhibited higher viral loads than intermittent shedders [coefficient(95%CI):1.62(1.19,2.05);p < 0.001], and viral loads increased with the number of visits where KSHV DNA was detected in saliva (type III test p < 0.001). Household-level factors attributed for 19% of the variability in KSHV shedding (ICC:0.191;p = 0.010). Geospatial analysis indicated overlapping hotspots of households with more KSHV seropositive individuals and KSHV shedders, distinct from areas where PLWH were clustered.

Discussion

KSHV oral shedding is influenced by multiple factors at the individual, household, and regional levels. To mitigate ongoing KSHV transmission a comprehensive understanding of factors contributing to oral KSHV reactivation and transmission within households is needed.

Structures of Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus virions reveal species-specific tegument and envelope features

Epstein-Barr virus (EBV) and Kaposi's sarcoma-associated herpesvirus (KSHV) are classified into the gammaherpesvirus subfamily of Herpesviridae , which stands out from its alpha- and betaherpesvirus relatives due to the tumorigenicity of its members. Although structures of human alpha- and betaherpesviruses by cryogenic electron tomography (cryoET) have been reported, reconstructions of intact human gammaherpesvirus virions remain elusive. Here, we structurally characterize extracellular virions of EBV and KSHV by deep learning-enhanced cryoET, resolving both previously known monomorphic capsid structures and previously unknown pleomorphic features beyond the capsid. Through subtomogram averaging and subsequent tomogram-guided sub-particle reconstruction, we determined the orientation of KSHV nucleocapsids from mature virions with respect to the portal to provide spatial context for the tegument within the virion. Both EBV and KSHV have an eccentric capsid position and polarized distribution of tegument. Tegument species span from the capsid to the envelope and may serve as scaffolds for tegumentation and envelopment. The envelopes of EBV and KSHV are less densely populated with glycoproteins than those of herpes simplex virus 1 and human cytomegalovirus, representative members of alpha- and betaherpesviruses, respectively. This population density of glycoproteins correlates with their relative infectivity against HEK293T cells. Also, we observed fusion protein gB trimers exist within triplet arrangements in addition to standalone complexes, which is relevant to understanding dynamic processes such as fusion pore formation. Taken together, this study reveals nuanced yet important differences in the tegument and envelope architectures among human herpesviruses and provides insights into their varied cell tropism and infection.

Importance

Discovered in 1964, Epstein-Barr virus (EBV) is the first identified human oncogenic virus and the founding member of the gammaherpesvirus subfamily. In 1994, another cancer-causing virus was discovered in lesions of AIDS patients and later named Kaposi's sarcoma-associated herpesvirus (KSHV), the second human gammaherpesvirus. Despite the historical importance of EBV and KSHV, technical difficulties with isolating large quantities of these viruses and the pleiomorphic nature of their envelope and tegument layers have limited structural characterization of their virions. In this study, we employed the latest technologies in cryogenic electron microscopy (cryoEM) and tomography (cryoET) supplemented with an artificial intelligence-powered data processing software package to reconstruct 3D structures of the EBV and KSHV virions. We uncovered unique properties of the envelope glycoproteins and tegument layers of both EBV and KSHV. Comparison of these features with their non-tumorigenic counterparts provides insights into their relevance during infection.

Kaposi sarcoma-associated herpesvirus complement control protein (KCP) and glycoprotein K8.1 are not required for viral infection in vitro or in vivo

Kaposi sarcoma-associated herpesvirus (KSHV), also known as human herpesvirus-8, is the causal agent of Kaposi sarcoma, a cancer that appears as tumors on the skin or mucosal surfaces, as well as primary effusion lymphoma and KSHV-associated multicentric Castleman disease, which are B-cell lymphoproliferative disorders. Effective prophylactic and therapeutic strategies against KSHV infection and its associated diseases are needed. To develop these strategies, it is crucial to identify and target viral glycoproteins involved in KSHV infection of host cells. Multiple KSHV glycoproteins expressed on the viral envelope are thought to play a pivotal role in viral infection, but the infection mechanisms involving these glycoproteins remain largely unknown. We investigated the role of two KSHV envelope glycoproteins, KSHV complement control protein (KCP) and K8.1, in viral infection in various cell types in vitro and in vivo. Using our newly generated anti-KCP antibodies, previously characterized anti-K8.1 antibodies, and recombinant mutant KSHV viruses lacking KCP, K8.1, or both, we demonstrated the presence of KCP and K8.1 on the surface of both virions and KSHV-infected cells. We showed that KSHV lacking KCP and/or K8.1 remained infectious in KSHV-susceptible cell lines, including epithelial, endothelial, and fibroblast, when compared to wild-type recombinant KSHV. We also provide the first evidence that KSHV lacking K8.1 or both KCP and K8.1 can infect human B cells in vivo in a humanized mouse model. Thus, these results suggest that neither KCP nor K8.1 is required for KSHV infection of various host cell types and that these glycoproteins do not determine KSHV cell tropism.

IMPORTANCE

Kaposi sarcoma-associated herpesvirus (KSHV) is an oncogenic human gamma-herpesvirus associated with the endothelial malignancy Kaposi sarcoma and the lymphoproliferative disorders primary effusion lymphoma and multicentric Castleman disease. Determining how KSHV glycoproteins such as complement control protein (KCP) and K8.1 contribute to the establishment, persistence, and transmission of viral infection will be key for developing effective anti-viral vaccines and therapies to prevent and treat KSHV infection and KSHV-associated diseases. Using newly generated anti-KCP antibodies, previously characterized anti-K8.1 antibodies, and recombinant mutant KSHV viruses lacking KCP and/or K8.1, we show that KCP and K8.1 can be found on the surface of both virions and KSHV-infected cells. Furthermore, we show that KSHV lacking KCP and/or K8.1 remains infectious to diverse cell types susceptible to KSHV in vitro and to human B cells in vivo in a humanized mouse model, thus providing evidence that these viral glycoproteins are not required for KSHV infection.

KSHV infection of B cells primes protective T cell responses in humanized mice

Kaposi sarcoma associated herpesvirus (KSHV) is associated with around 1% of all human tumors, including the B cell malignancy primary effusion lymphoma (PEL), in which co-infection with the Epstein Barr virus (EBV) can almost always be found in malignant cells. Here, we demonstrate that KSHV/EBV co-infection of mice with reconstituted human immune systems (humanized mice) leads to IgM responses against both latent and lytic KSHV antigens, and expansion of central and effector memory CD4+ and CD8+ T cells. Among these, KSHV/EBV dual-infection allows for the priming of CD8+ T cells that are specific for the lytic KSHV antigen K6 and able to kill KSHV/EBV infected B cells. This suggests that K6 may represent a vaccine antigen for the control of KSHV and its associated pathologies in high seroprevalence regions, such as Sub-Saharan Africa.

The general transcription factor TFIIB is a target for transcriptome control during cellular stress and viral infection

Many stressors, including viral infection, induce a widespread suppression of cellular RNA polymerase II (RNAPII) transcription, yet the mechanisms underlying transcriptional repression are not well understood. Here we find that a crucial component of the RNA polymerase II holoenzyme, general transcription factor IIB (TFIIB), is targeted for post-translational turnover by two pathways, each of which contribute to its depletion during stress. Upon DNA damage, translational stress, apoptosis, or replication of the oncogenic Kaposi's sarcoma-associated herpesvirus (KSHV), TFIIB is cleaved by activated caspase-3, leading to preferential downregulation of pro-survival genes. TFIIB is further targeted for rapid proteasome-mediated turnover by the E3 ubiquitin ligase TRIM28. KSHV counteracts proteasome-mediated turnover of TFIIB, thereby preserving a sufficient pool of TFIIB for transcription of viral genes. Thus, TFIIB may be a lynchpin for transcriptional outcomes during stress and a key target for nuclear replicating DNA viruses that rely on host transcriptional machinery.

Significance Statement

Transcription by RNA polymerase II (RNAPII) synthesizes all cellular protein-coding mRNA. Many cellular stressors and viral infections dampen RNAPII activity, though the processes underlying this are not fully understood. Here we describe a two-pronged degradation strategy by which cells respond to stress by depleting the abundance of the key RNAPII general transcription factor, TFIIB. We further demonstrate that an oncogenic human gammaherpesvirus antagonizes this process, retaining enough TFIIB to support its own robust viral transcription. Thus, modulation of RNAPII machinery plays a crucial role in dictating the outcome of cellular perturbation.

Immune cell phenotype and function patterns across the life course in individuals from rural Uganda

Background

To determine the pattern of immune cell subsets across the life span in rural sub-Saharan Africa (SSA), and to set a reference standard for cell subsets amongst Africans, we characterised the major immune cell subsets in peripheral blood including T cells, B cells, monocytes, NK cells, neutrophils and eosinophils, in individuals aged 3 to 89 years from Uganda.

Methods

Immune phenotypes were measured using both conventional flow cytometry in 72 individuals, and full spectrum flow cytometry in 80 individuals. Epstein-Barr virus (EBV) IFN-γ T cell responses were quantified in 332 individuals using an ELISpot assay. Full blood counts of all study participants were also obtained.

Results

The percentages of central memory (TCM) and senescent CD4+ and CD8+ T cell subsets, effector memory (TEM) CD8+ T cells and neutrophils increased with increasing age. On the other hand, the percentages of naïve T (TN) and B (BN) cells, atypical B cells (BA), total lymphocytes, eosinophils and basophils decreased with increasing age. There was no change in CD4+ or CD8+ T effector memory RA (TEMRA) cells, exhausted T cells, NK cells and monocytes with age. Higher eosinophil and basophil percentages were observed in males compared to females. T cell function as measured by IFN-γ responses to EBV increased with increasing age, peaking at 31-55 years.

Conclusion

The percentages of cell subsets differ between individuals from SSA compared to those elsewhere, perhaps reflecting a different antigenic milieu. These results serve as a reference for normal values in this population.

Plasmodium falciparum Malaria Is Associated With Increased Kaposi Sarcoma-Associated Herpesvirus (KSHV) Seropositivity and Higher KSHV Antibody Breadth and Magnitude: Results of a Case-Control Study From Rural Uganda

BACKGROUND

Previously, we showed that children with asymptomatic Plasmodium falciparum (Pf) malaria infection had higher Kaposi sarcoma-associated herpesvirus (KSHV) viral load, increased risk of KSHV seropositivity, and higher KSHV antibody levels. We hypothesize that clinical malaria has an even larger association with KSHV seropositivity. In the current study, we investigated the association between clinical malaria and KSHV seropositivity and antibody levels.

METHODS

Between December 2020 and March 2022, sick children (aged 5-10 years) presenting at a clinic in Uganda were enrolled in a case-control study. Pf was detected using malaria rapid diagnostic tests (RDTs) and subsequently with quantitative real-time polymerase chain reaction (qPCR). Children with malaria were categorized into 2 groups: RDT+/PfPCR+ and RDT-/PfPCR+.

RESULTS

The seropositivity of KSHV was 60% (47/78) among Pf-uninfected children, 79% (61/77) among children who were RDT-/PfPCR+ (odds ratio [OR], 2.41 [95% confidence interval {CI}, 1.15-5.02]), and 95% (141/149) in children who were RDT+/PfPCR+ (OR, 10.52 [95% CI, 4.17-26.58]; Ptrend < .001). Furthermore, RDT+/PfPCR+ children followed by RDT-/PfPCR+ children had higher KSHV IgG and IgM antibody levels and reacted to more KSHV antigens compared to uninfected children.

CONCLUSIONS

Clinical malaria is associated with both increased KSHV seropositivity and antibody magnitude, suggesting that Pf is affecting KSHV immunity.

Reactivation of Kaposi's sarcoma-associated herpesvirus (KSHV) by SARS-CoV-2 in non-hospitalised HIV-infected patients

BACKGROUND

While acute SARS-CoV-2 infection and associated inflammation resulted in substantial morbidity and mortality during the COVID-19 pandemic, particularly in unvaccinated patients, long-term effects of SARS-CoV-2 exposure for reactivation of latent oncogenic herpesviruses, such as KSHV, is unknown.

METHODS

We performed a longitudinal observational cross-sectional study on 407 non-hospitalised adult HIV-infected (CD4 count <350 cells/μL) patients attending antiretroviral therapy services in Gugulethu, South Africa, from October 2020 to April 2023.

FINDINGS

KSHV seroprevalence was 53.5%; the quarterly SARS-CoV-2 seroprevalence increased from 76.2% (before roll-out of COVID-19 vaccinations) to 94.9%, with 32.2% being self-reportedly vaccinated against COVID-19. Over the course of recruitment, the quarterly percentage of patients with detectable KSHV viral load (VL) in the peripheral blood increased from 3.3% to 69.2%. The presence of KSHV VL was significantly associated with SARS-CoV-2 RBD antibody titers in unvaccinated (median RBD IgG OD 1.24 [IQR 0.82-2.42] in non-reactivated versus 2.83 [IQR 1.08-4.72] in reactivated patients, p = 0.0030) but not in vaccinated patients (median RBD IgG OD 5.13 [IQR 4.11-6.36] in non-reactivated versus 4.53 [IQR 2.90-5.92] in reactivated patients, p = 0.086). Further logistic regression revealed significantly higher odds of KSHV reactivation in unvaccinated, previously SARS-CoV-2 exposed patients (p = 0.015, adjusted OR 1.28 [95% CI: 1.05-1.55]), but not vaccinated patients (p = 0.080, adjusted OR 0.83 [95% CI: 0.67-1.02]). Interestingly, detectable KSHV VL was not associated with increased inflammatory markers such as C-reactive protein and interleukin-6.

INTERPRETATION

High, and most likely repeated, exposure to SARS-CoV-2 in unvaccinated individuals may have long-term consequences for reactivation of KSHV infection as shown here in the context of HIV-infected patients with impaired immune functions. Post-pandemic prevention and/or monitoring strategies of potential KSHV-associated pathologies in high-risk patients with immunodeficiencies are therefore highly recommended.

FUNDING

This research was funded by the EDCTP2 programme (Training and Mobility Action TMA2018SF-2446).

Antibody profiling and predictive modeling discriminate between Kaposi sarcoma and asymptomatic KSHV infection

Protein-level immunodominance patterns against Kaposi sarcoma-associated herpesvirus (KSHV), the aetiologic agent of Kaposi sarcoma (KS), have been revealed from serological probing of whole protein arrays, however, the epitopes that underlie these patterns have not been defined. We recently demonstrated the utility of phage display in high-resolution linear epitope mapping of the KSHV latency-associated nuclear antigen (LANA/ORF73). Here, a VirScan phage immunoprecipitation and sequencing approach, employing a library of 1,988 KSHV proteome-derived peptides, was used to quantify the breadth and magnitude of responses of 59 sub-Saharan African KS patients and 22 KSHV-infected asymptomatic individuals (ASY), and ultimately to support an application of machine-learning-based predictive modeling using the peptide-level responses. Comparing anti-KSHV antibody repertoire revealed that magnitude, not breadth, increased in KS. The most targeted epitopes in both KS and ASY were in the immunodominant proteins, notably, K8.129-56 and ORF65140-168, in addition to LANA. Finally, using unbiased machine-learning-based predictive models, reactivity to a subset of 25 discriminative peptides was demonstrated to successfully classify KS patients from asymptomatic individuals. Our study provides the highest resolution mapping of antigenicity across the entire KSHV proteome to date, which is vital to discern mechanisms of viral pathogenesis, to define prognostic biomarkers, and to design effective vaccine and therapeutic strategies. Future studies will investigate the diagnostic, prognostic, and therapeutic potential of the 25 discriminative peptides.

Infant feeding and treatment practices could lead to enhanced transmission of Kaposi's sarcoma-associated herpesvirus (KSHV) and other orally shed infections via saliva, in rural south-western Uganda

This qualitative sub-study investigated household practices affecting orally shed infections using Kaposi's sarcoma-associated herpesvirus (KSHV) as a focus. Participants enrolled from 50 households in rural south-western Uganda were followed monthly up to three times. At enrolment, in-depth interviews were completed, and venous blood collected. KSHV seropositivity was defined as anti-KSHV antibody detection to any of 25 antigens by multiplex bead-based assay. Mouthwash samples from every visit were tested by qPCR and KSHV shedders defined as individuals with KSHV DNA detected. At least one KSHV seropositive person was in 48/49(98%) households. Among those, 79% had 1+ KSHV shedders including 45% with 1+ always shedders and 92% with 1+ intermittent shedders, not mutually exclusively. All respondents reported feeding infants with pre-masticated hard food/fruits and testing food/tea temperature. Temperature was tested by tasting, pouring tea on their hand, or touching the cup to their cheek. Some cooled food/tea using a utensil or blowing over it. Food sharing amongst children and adults and using the same dish was common practice. To treat colic pain, carers/mothers reported chewing herbs and spitting into the child's mouth. Feeding and treatment practices did not vary by KSHV status. We identified potential KSHV transmission modes in rural Ugandan households.

Modulation of Epstein-Barr-Virus (EBV)-Associated Cancers by Co-Infections

The oncogenic and persistent Epstein Barr virus (EBV) is carried by more than 95% of the human adult population. While asymptomatic in most of these, EBV can cause a wide variety of malignancies of lymphoid or epithelial cell origin. Some of these are also associated with co-infections that either increase EBV-induced tumorigenesis or weaken its immune control. The respective pathogens include Kaposi-sarcoma-associated herpesvirus (KSHV), Plasmodium falciparum and human immunodeficiency virus (HIV). In this review, I will discuss the respective tumor entities and possible mechanisms by which co-infections increase the EBV-associated cancer burden. A better understanding of the underlying mechanisms could allow us to identify crucial features of EBV-associated malignancies and defects in their immune control. These could then be explored to develop therapies against the respective cancers by targeting EBV and/or the respective co-infections with pathogen-specific therapies or vaccinations.

Evaluation of human herpesvirus-8 viremia and antibody positivity in patients with HIV infection with human herpesvirus-8-related diseases

Human herpesvirus-8 (HHV-8) viremia is associated with refractory conditions in patients infected with HIV-1. Therefore, we evaluated the factors related to plasma HHV-8-DNA. Participants included patients infected with HIV-1 who visited our hospital. Plasma HHV-8-DNA levels were measured using real-time polymerase chain reaction, and anti-HHV-8 antibodies were assessed through enzyme immunoassays using multiple antigens (K8.1, ORF59, ORF65, and LANA). Factors related to plasma HHV-8-DNA were examined using Fisher's exact test or Mann-Whitney U test. The study involved 36 patients infected with HIV-1, of whom 19 were histologically diagnosed with Kaposi's sarcoma (KS), two had multicentric Castleman's disease (MCD), and 15 did not exhibit HHV-8-related disease. Before the introduction of antiretroviral therapy (ART), plasma HHV-8-DNA was detected in 44% (7/16) of patients with KS and in 9% (1/11) of patients without HHV-8-related disease. Among patients with KS, elevated plasma HHV-8-DNA levels (≥0.05 copies/µL) correlated with the presence of CDC category C diseases other than KS (p = 0.0337), anti-HHV-8 antibody negativity (p = 0.0337), anemia (p = 0.0474), and thrombocytopenia (p = 0.0146). Following ART initiation, the percentage of patients positive for plasma HHV-8-DNA decreased from 44% (7/16) to 6% (1/17), and the percentage of patients positive for anti-HHV-8 antibodies increased from 44% (7/16) to 88% (15/17). Finally, plasma HHV-8-DNA positivity and anti-HHV-8 antibody negativity were observed in two patients with MCD. Our findings suggest that insufficient production of anti-HHV-8 antibodies was associated with HHV-8 viremia, and that anti-HHV-8 antibody production was recovered with ART; thus, indicating the possibility of involvement of humoral immunity in suppressing HHV-8 viremia.

Effects of Maternal HIV Infection on Early Kaposi Sarcoma-Associated Herpesvirus Seroconversion in a Kenyan Mother-Infant Cohort

BACKGROUND

We identified whether maternal human immunodeficiency virus (HIV) infection during pregnancy affects transplacental transfer of Kaposi sarcoma-associated herpesvirus (KSHV)-specific antibodies and subsequent infant infection.

METHODS

We followed pregnant Kenyan women through delivery and their infants until age 2 years. Children were classified as HIV-exposed uninfected (HEU) or HIV-unexposed uninfected (HUU) based on maternal HIV status. Maternal venous and cord blood at delivery and child venous blood every 6 months were tested for antibodies to 20 KSHV antigens by multiplex bead-based immunoassay. Multiple comparisons were adjusted using false discovery rate (FDR).

RESULTS

Maternal HIV infection was significantly associated with decreased transplacental transfer of antibodies against all KSHV antigens and lower cord blood levels for 8 antigens at FDR P < .10. Neither birth to 6-month antibody level changes nor 6-month levels differed in HEU and HUU, except for ORF50. By age 24 months, 74% of children KSHV seroconverted but HEU and HUU did not differ in time to seroconversion nor 2-year seropositivity after adjustment for child malaria infection.

CONCLUSIONS

Maternal HIV infection reduced a child's initial KSHV antibody levels but did not affect age of infection. Regardless of HIV exposure in utero, KSHV seroconversion in Kenyan children occurred early; associated factors must be identified.

Comparison of Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus viral load in peripheral blood mononuclear cells and oral fluids of HIV-negative individuals aged 3-89 years from Uganda

We previously found that age, sex and malaria were associated with KSHV in individuals from Uganda. In this study, we have evaluated these same factors in relation to EBV in the same specimens. Overall, 74% (oral fluids) and 46% (PBMCs) had detectable EBV. This was significantly higher than observed for KSHV (24% oral fluids and 11% PBMCs). Individuals with EBV in PBMCs were more likely to have KSHV in PBMCs (P = 0.011). The peak age for detection of EBV in oral fluids was 3-5 years while that of KSHV was 6-12 years. In PBMCs, there was a bimodal peak age for detection of EBV (at 3-5 years and 66 + years) while for KSHV there was a single peak at 3-5 years. Individuals with malaria had higher levels of EBV in PBMCs compared to malaria-negative individuals (P = 0.002). In summary, our results show that younger age and malaria are associated with higher levels of EBV and KSHV in PBMCs suggesting malaria impacts immunity to both gamma-herpesviruses.

Distinctive Kaposi Sarcoma-Associated Herpesvirus Serological Profile during Acute Plasmodium falciparum Malaria Episodes

The seroprevalence of Kaposi sarcoma-associated herpesvirus (KSHV) and the incidence of endemic Kaposi sarcoma (KS) overlap with regions of malaria endemicity in sub-Saharan Africa. Multiple studies have shown an increased risk of KSHV seroconversion in children from high malaria compared to low malaria regions; however, the impact of acute episodes of Plasmodium falciparum (P. falciparum) malaria on KSHV's biphasic life cycle and lytic reactivation has not been determined. Here, we examined KSHV serological profiles and viral loads in 134 children with acute malaria and 221 healthy children from high malaria regions in Kisumu, as well as 77 healthy children from low malaria regions in Nandi. We assayed KSHV, Epstein-Barr virus (EBV), and P. falciparum malaria antibody responses in these three by multiplexed Luminex assay. We confirmed that KSHV seroprevalence was significantly associated with malaria endemicity (OR = 1.95, 1.18-3.24 95% CI, p = 0.01) with 71-77% seropositivity in high-malaria (Kisumu) compared to 28% in low-malaria (Nandi) regions. Furthermore, KSHV serological profiles during acute malaria episodes were distinct from age-matched non-malaria-infected children from the same region. Paired IgG levels also varied after malaria treatment, with significantly higher anti-ORF59 at day 0 but elevated ORF38, ORF73, and K8.1 at day 3. Acute malaria episodes is characterized by perturbation of KSHV latency in seropositive children, providing further evidence that malaria endemicity contributes to the observed increase in endemic KS incidence in sub-Saharan Africa.

High Seroprevalence of Kaposi Sarcoma-Associated Herpesvirus in Men Who Have Sex With Men With HIV in the Southern United States

Background

Disparities in mortality in human immunodeficiency virus (HIV)-associated Kaposi sarcoma have been described, particularly in Black men in the southern United States. It is unclear if there are racial/ethnic differences in the seroprevalence of Kaposi sarcoma-associated herpesvirus (KSHV) that may be contributing.

Methods

This is a cross-sectional study of men who have sex with men (MSM) and transgender women with HIV. Participants were recruited from an outpatient HIV clinic in Dallas, Texas, for a 1-time study visit and were excluded from analysis if they had any history of KSHV disease. Plasma was tested for antibodies to KSHV K8.1 or ORF73 antigens, and KSHV DNA was measured in oral fluids and blood by polymerase chain reaction. KSHV seroprevalence and viral shedding in blood and oral fluids were calculated. Additionally, independent risk factors for KSHV seropositivity were assessed by multivariable logistic regression analysis.

Results

Two hundred five participants were included in our analysis. Overall, KSHV seroprevalence was high (68%) with no significant difference between racial/ethnic groups. Among seropositive participants, KSHV DNA was detected in 28.6% of oral fluids and 10.9% of peripheral blood specimens, respectively. The factors most strongly associated with KSHV seropositivity were oral-anal sex (odds ratio [OR], 3.02), oral-penile sex (OR, 4.63), and methamphetamine use (OR, 4.67).

Conclusions

High local seroprevalence of KSHV is likely a key driver of the high burden of KSHV-associated diseases regionally, though it does not explain the observed disparities in KSHV-associated disease prevalence among racial/ethnic groups. Our findings support that KSHV is primarily transmitted via exchange of oral fluids.

Comparison of Epstein-Barr virus and Kaposi's sarcoma-associated herpesvirus viral load in peripheral blood mononuclear cells and oral fluids of HIV-negative individuals aged 3 to 89 years from Uganda

We previously found that age, sex, and malaria were associated with KSHV viral load in individuals from Uganda. In this study, we have evaluated factors associated with presence of EBV DNA in blood and oral fluids among the same individuals, using the same biological samples. Overall, 74% of oral fluids samples and 46% of PBMCs had detectable EBV, compared to 24% and 11% for KSHV respectively Individuals with EBV in PBMCs were more likely to have KSHV in PBMCs (P=0.016). The peak age for detection of EBV in oral fluids was 3-5 years while that of KSHV was 6-12 years. In PBMCs, the peak age for detection of EBV was 66+ years and KSHV was 3-5 years. Individuals with malaria had higher levels of EBV in PBMCs compared to malaria-negative individuals (P=0.002). In summary, our results show that younger age and malaria are associated with higher levels of EBV and KSHV in PBMCs suggesting malaria impacts immunity to EBV and KSHV.

Immunization of Mice with Virus-Like Vesicles of Kaposi Sarcoma-Associated Herpesvirus Reveals a Role for Antibodies Targeting ORF4 in Activating Complement-Mediated Neutralization

Infection by Kaposi sarcoma-associated herpesvirus (KSHV) can cause severe consequences, such as cancers and lymphoproliferative diseases. Whole inactivated viruses (WIV) with chemically destroyed genetic materials have been used as antigens in several licensed vaccines. During KSHV productive replication, virus-like vesicles (VLVs) that lack capsids and viral genomes are generated along with virions. Here, we investigated the immunogenicity of KSHV VLVs produced from a viral mutant that was defective in capsid formation and DNA packaging. Mice immunized with adjuvanted VLVs generated KSHV-specific T cell and antibody responses. Neutralization of KSHV infection by the VLV immune serum was low but was markedly enhanced in the presence of the complement system. Complement-enhanced neutralization and complement deposition on KSHV-infected cells was dependent on antibodies targeting viral open reading frame 4 (ORF4). However, limited complement-mediated enhancement was detected in the sera of a small cohort of KSHV-infected humans which contained few neutralizing antibodies. Therefore, vaccination that induces antibody effector functions can potentially improve infection-induced humoral immunity. Overall, our study highlights a potential benefit of engaging complement-mediated antibody functions in future KSHV vaccine development. IMPORTANCE KSHV is a virus that can lead to cancer after infection. A vaccine that prevents KSHV infection or transmission would be helpful in preventing the development of these cancers. We investigated KSHV VLV as an immunogen for vaccination. We determined that antibodies targeting the viral protein ORF4 induced by VLV immunization could engage the complement system and neutralize viral infection. However, ORF4-specific antibodies were seldom detected in the sera of KSHV-infected humans. Moreover, these human sera did not potently trigger complement-mediated neutralization, indicating an improvement that immunization can confer. Our study suggests a new antibody-mediated mechanism to control KSHV infection and underscores the benefit of activating the complement system in a future KSHV vaccine.

DNA processing by the Kaposi's sarcoma-associated herpesvirus alkaline exonuclease SOX contributes to viral gene expression and infectious virion production

Alkaline exonucleases (AE) are present in several large DNA viruses including bacteriophage λ and herpesviruses, where they play roles in viral DNA processing during genome replication. Given the genetic conservation of AEs across viruses infecting different kingdoms of life, these enzymes likely assume central roles in the lifecycles of viruses where they have yet to be well characterized. Here, we applied a structure-guided functional analysis of the bifunctional AE in the oncogenic human gammaherpesvirus Kaposi's sarcoma-associated herpesvirus (KSHV), called SOX. In addition to identifying a preferred DNA substrate preference for SOX, we define key residues important for DNA binding and DNA processing, and how SOX activity on DNA partially overlaps with its functionally separable cleavage of mRNA. By engineering these SOX mutants into KSHV, we reveal roles for its DNase activity in viral gene expression and infectious virion production. Our results provide mechanistic insight into gammaherpesviral AE activity as well as areas of functional conservation between this mammalian virus AE and its distant relative in phage λ.

Antibody epitope profiling of the KSHV LANA protein using VirScan

The humoral antibody response against Kaposi sarcoma-associated herpesvirus (KSHV) in infected individuals has been characterized demonstrating the latency-associated nuclear antigen (LANA) as the most antigenic KSHV protein. Despite the antigenicity of the protein, specific LANA epitopes have not been systematically characterized. Here, we utilized a bacteriophage T7 library, which displays 56-amino acid KSHV LANA peptides with 28-amino acid overlap (VirScan), to define those epitopes in LANA targeted by antibodies from a cohort of 62 sub-Saharan African Kaposi sarcoma (KS) patients and 22 KSHV-infected asymptomatic controls. Intra- and inter-patient breadth and magnitude of the anti-LANA responses were quantified at the peptide and amino acid levels. From these data, we derived a detailed epitope annotation of the entire LANA protein, with a high-resolution focus on the N- and C-termini. Overall, the central repeat region was highly antigenic, but the responses to this region could not be confidently mapped due to its high variability. The highly conserved N-terminus was targeted with low breadth and magnitude. In a minority of individuals, antibodies specific to the nuclear localization sequence and a portion of the proline-rich regions of the N-terminus were evident. In contrast, the first half of the conserved C-terminal domain was consistently targeted with high magnitude. Unfortunately, this region was not included in LANA partial C-terminal crystal structures, however, it was predicted to adopt predominantly random-coil structure. Coupled with functional and secondary structure domain predictions, VirScan revealed fine resolution epitope mapping of the N- and C-terminal domains of LANA that is consistent with previous antigenicity studies and may prove useful to correlate KSHV humoral immunity with pathogenesis.

KSHV (HHV8) vaccine: promises and potential pitfalls for a new anti-cancer vaccine

Seven viruses cause at least 15% of the total cancer burden. Viral cancers have been described as the "low-hanging fruit" that can be potentially prevented or treated by new vaccines that would alter the course of global human cancer. Kaposi sarcoma herpesvirus (KSHV or HHV8) is the sole cause of Kaposi sarcoma, which primarily afflicts resource-poor and socially marginalized populations. This review summarizes a recent NIH-sponsored workshop's findings on the epidemiology and biology of KSHV as an overlooked but potentially vaccine-preventable infection. The unique epidemiology of this virus provides opportunities to prevent its cancers if an effective, inexpensive, and well-tolerated vaccine can be developed and delivered.

Adaptive immune responses to Kaposi's sarcoma-associated herpesvirus

Kaposi's sarcoma-associated herpesvirus (KSHV) is a gammaherpesvirus that causes Kaposi's sarcoma (KS), primary effusion lymphoma, multicentric Castleman's disease and KSHV-induced cytokine syndrome. KSHV established lifelong infection and has evolved numerous ways in which to evade adaptive immune responses. Most KSHV infections are asymptomatic but when disease occurs it does so in the context of immune suppression especially HIV infection. It is important therefore to study immune responses to KSHV in order to understand KSHV-related disease pathogenesis.

HOPE in action: A prospective multicenter pilot study of liver transplantation from donors with HIV to recipients with HIV

Liver transplantation (LT) from donors-with-HIV to recipients-with-HIV (HIV D+/R+) is permitted under the HOPE Act. There are only three international single-case reports of HIV D+/R+ LT, each with limited follow-up. We performed a prospective multicenter pilot study comparing HIV D+/R+ to donors-without-HIV to recipients-with-HIV (HIV D-/R+) LT. We quantified patient survival, graft survival, rejection, serious adverse events (SAEs), human immunodeficiency virus (HIV) breakthrough, infections, and malignancies, using Cox and negative binomial regression with inverse probability of treatment weighting. Between March 2016-July 2019, there were 45 LTs (8 simultaneous liver-kidney) at 9 centers: 24 HIV D+/R+, 21 HIV D-/R+ (10 D- were false-positive). The median follow-up time was 23 months. Median recipient CD4 was 287 cells/µL with 100% on antiretroviral therapy; 56% were hepatitis C virus (HCV)-seropositive, 13% HCV-viremic. Weighted 1-year survival was 83.3% versus 100.0% in D+ versus D- groups (p = .04). There were no differences in one-year graft survival (96.0% vs. 100.0%), rejection (10.8% vs. 18.2%), HIV breakthrough (8% vs. 10%), or SAEs (all p > .05). HIV D+/R+ had more opportunistic infections, infectious hospitalizations, and cancer. In this multicenter pilot study of HIV D+/R+ LT, patient and graft survival were better than historical cohorts, however, a potential increase in infections and cancer merits further investigation.

Kaposi's sarcoma-associated herpesvirus T cell responses in HIV seronegative individuals from rural Uganda

T cell responses to Kaposi's sarcoma-associated herpesvirus (KSHV) are likely essential in the control of KSHV infection and protection from associated disease, but remain poorly characterised. KSHV prevalence in rural Uganda is high at >90%. Here we investigate IFN- γ T cell responses to the KSHV proteome in HIV-negative individuals from a rural Ugandan population. We use an ex-vivo IFN- γ ELISpot assay with overlapping peptide pools spanning 83 KSHV open reading frames (ORF) on peripheral blood mononuclear cells (PBMC) from 116 individuals. KSHV-specific T cell IFN- γ responses are of low intensity and heterogeneous, with no evidence of immune dominance; by contrast, IFN- γ responses to Epstein-Barr virus, Cytomegalovirus and influenza peptides are frequent and intense. Individuals with KSHV DNA in PBMC have higher IFN- γ responses to ORF73 (p = 0.02) and lower responses to K8.1 (p = 0.004) when compared with those without KSHV DNA. In summary, we demonstrate low intensity, heterogeneous T cell responses to KSHV in immune-competent individuals.

Malaria Is Associated With Kaposi Sarcoma-Associated Herpesvirus Seroconversion in a Cohort of Western Kenyan Children

BACKGROUND

We aimed to determine whether Plasmodium falciparum infection affects age of Kaposi sarcoma-associated herpesvirus (KSHV) seroconversion in Kenyan children.

METHODS

Kenyan children (n = 144) enrolled at age 1 month, from 2 sites with different levels of malaria transmission (stable/high vs unstable/low) were followed to age 24 months. Plasma was tested for KSHV antibodies using enzyme-linked immunosorbent assay (ELISA; K8.1 and LANA) and a multiplex bead-based assay (K8.1, K10.5, ORF38, ORF50, and LANA) and whole blood tested for P. falciparum DNA using quantitative PCR. Cox proportional hazards models were used to assess associations between P. falciparum DNA detection, malaria annualized rate (P. falciparum detections/person-years), and enrollment site (malaria-high vs malaria-low) with time to KSHV seroconversion.

RESULTS

KSHV seroprevalence was 63% by age 2 years when assessed by multiplex assay. Children with P. falciparum were at increased hazards of earlier KSHV seroconversion and, among children with malaria, the hazard of becoming KSHV seropositive increased significantly with increasing malaria annualized rate. Children from the malaria-high transmission region had no significant difference in hazards of KSHV seroconversion at 12 months but were more likely to become KSHV seropositive by age 24 months.

DISCUSSION

Malaria exposure increases the risk for KSHV seroconversion early in life.

Relationships Between Maternal Antibody Responses and Early Childhood Infection With Kaposi Sarcoma-Associated Herpesvirus

While mother-to-child transmission is believed to play in important role in early childhood infection with Kaposi sarcoma-associated herpesvirus (KSHV), the maternal immune response remains largely uncharacterized. This study aimed to characterize the longitudinal humoral response to KSHV in a cohort of HIV-infected Zambian mothers without KS and identify potential factors that may influence transmission. In total, 86/124 (69.4%) mothers were found to be KSHV seropositive. Longitudinal KSHV titers were fairly stable over time, although seroreversion was still common. Of the total 124 mothers, 81 had at least 1 child KSHV seroconvert during the 2 years analyzed, while the remaining 43 mothers had KSHV-seronegative children. Mothers of KSHV-negative children had higher geometric mean titers than mothers of KSHV-positive children; however, there was no difference in the presence of neutralizing antibodies. This suggests that a strong anti-KSHV immune response, and potentially nonneutralizing antibodies, may reduce transmission.

Kaposi Sarcoma-Associated Herpesvirus Infection and Endemic Burkitt Lymphoma

BACKGROUND

Endemic Burkitt lymphoma (eBL) is associated with Epstein-Barr virus (EBV) and Plasmodium falciparum malaria coinfections. However, the role of Kaposi sarcoma-associated herpesvirus (KSHV), also endemic in Africa, has not been evaluated as a cofactor in eBL pathogenesis.

METHODS

Multiplexed seroprofiles for EBV, malaria, and KSHV were generated for 266 eBL patients, 78 non-eBL cancers, and 202 healthy children. KSHV and EBV loads were quantified by PCR.

RESULTS

KSHV seroprevalence did not differ by study group but was associated with age. Seropositivity, defined by K8.1/LANA or in combination with 5 other KSHV antigens (ORF59, ORF65, ORF61, ORF38, and K5) was associated with antimalarial antibody levels to AMA1 (odds ratio [OR], 2.41, P < .001; OR, 2.07, P < .001) and MSP1 (OR, 2.41, P = .0006; OR, 5.78, P < .001), respectively. KSHV loads did not correlate with antibody levels nor differ across groups but were significantly lower in children with detectable EBV viremia (P = .014).

CONCLUSIONS

Although KSHV-EBV dual infection does not increase eBL risk, EBV appears to suppress reactivation of KSHV while malaria exposure is associated with KSHV infection and/or reactivation. Both EBV and malaria should, therefore, be considered as potential effect modifiers for KSHV-associated cancers in sub-Saharan Africa.

Malaria during pregnancy and transplacental transfer of Kaposi sarcoma-associated herpesvirus (KSHV) antibodies: a cohort study of Kenyan mother and child pairs

BACKGROUND

Kaposi sarcoma-associated herpesvirus (KSHV) seroprevalence in sub-Saharan African children can range up to 50% by age 2 years but factors affecting early age of KSHV infection are not well understood. Malaria during pregnancy has been associated with hindered transplacental transfer of antibodies to several pathogens but whether it affects transplacental transfer of KSHV antibodies is unknown. We aimed to determine if in utero malaria exposure reduced the transfer of KSHV antibodies across the placenta.

METHODS

A cohort study in Kisumu, Kenya enrolled pregnant women at their first antenatal clinic (ANC) visit and followed them through delivery. We included 70 KSHV-positive, HIV-negative mothers and their children. KSHV antibody levels were measured by ELISA (K8.1, ORF73) and multiplex assay (K8.1, ORF73, K10.5, ORF38, ORF50). Transplacental transfer of antibodies was measured by the cord to maternal blood ratio (CMR) of KSHV antibodies. Malaria during pregnancy was defined as detection of Plasmodium falciparum (Pf) DNA at any ANC visit or delivery. Among women with malaria during pregnancy, we examined time of last malaria infection prior to delivery (< 27 vs. 27+ weeks gestation) and malaria incidence rate (MIR) (episodes/100 person-weeks).

RESULTS

KSHV seroprevalence (positive for K8.1 or ORF73 by ELISA) among pregnant women was 88%. Neither malaria during pregnancy, malaria infection timing, nor MIR were associated with maternal delivery KSHV antibody blood levels. Maternal delivery and cord blood KSHV antibody levels were highly correlated but these correlations did not differ by malaria during pregnancy. KSHV transplacental antibody transfer was not associated with malaria during pregnancy, malaria infection timing, nor MIR.

CONCLUSIONS

Malaria during pregnancy does not appear to affect transfer of KSHV antibodies across the placenta.

The Presence of Antibody-Dependent Cell Cytotoxicity-Mediating Antibodies in Kaposi Sarcoma-Associated Herpesvirus-Seropositive Individuals Does Not Correlate with Disease Pathogenesis or Progression

Although the immune response is likely to play a pivotal role in controlling Kaposi sarcoma (KS)-associated herpesvirus (KSHV) and preventing disease development, the exact factors responsible for that control remain ill defined. T cell responses are weak and variable, and neutralizing Abs are more frequently detected in individuals with KS. This suggests a potential role for nonneutralizing Abs, which to date have been largely uninvestigated. Ab-dependent cell cytotoxicity (ADCC) is a common effector function for nonneutralizing Abs and is known to play a protective role in other herpesvirus infections; yet, ADCC has never been investigated in the context of KSHV infection. In this study, we provide, to our knowledge, the first evidence that anti-KSHV Abs are capable of mediating ADCC responses against infected human cells undergoing lytic reactivation. ADCC activity significantly higher than seronegative controls was detected in 24 of 68 KSHV-seropositive individuals tested. However, ADCC responses were not associated with KS development or progression. ADCC activity was also found to be independent of HIV status, sex, age, KSHV Ab titer, and KSHV-neutralizing activity. Nevertheless, additional investigations into effector cell function between KS and asymptomatic individuals are needed to determine whether ADCC has a role in preventing KS.

Risk Factors for Kaposi's Sarcoma-Associated Herpesvirus DNA in Blood and in Saliva in Rural Uganda

BACKGROUND

Detectable Kaposi's sarcoma-associated herpesvirus (KSHV) DNA in blood and increased antibody titres may indicate KSHV reactivation, while the transmission of KSHV occurs via viral shedding in saliva.

METHODS

We investigated the risk factors for KSHV DNA detection by real-time polymerase chain reaction in blood and by viral shedding in saliva, in 878 people aged 3 to 89 years of both sexes in a rural Ugandan population cohort. Helminths were detected using microscopy and the presence of malaria parasitaemia was identified using rapid diagnostic tests. Regression modelling was used for a statistical analysis.

RESULTS

The KSHV viral load in blood did not correlate with the viral load in saliva, suggesting separate immunological controls within each compartment. The proportions of individuals with a detectable virus in blood were 23% among children aged 3-5 years and 22% among those 6-12 years, thereafter reducing with increasing age. The proportions of individuals with a detectable virus in saliva increased from 30% in children aged 3-5 years to 45% in those aged 6-12 years, and decreased subsequently with increasing age. Overall, 29% of males shed in saliva, compared to 19% of females (P = .008).

CONCLUSIONS

Together, these data suggest that young males may be responsible for much of the onward transmission of KSHV. Individuals with a current malaria infection had higher levels of viral DNA in their blood (P = .031), compared to uninfected individuals. This suggests that malaria may lead to KSHV reactivation, thereby increasing the transmission and pathogenicity of the virus.

Distinct genetic architectures and environmental factors associate with host response to the γ2-herpesvirus infections

Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr Virus (EBV) establish life-long infections and are associated with malignancies. Striking geographic variation in incidence and the fact that virus alone is insufficient to cause disease, suggests other co-factors are involved. Here we present epidemiological analysis and genome-wide association study (GWAS) in 4365 individuals from an African population cohort, to assess the influence of host genetic and non-genetic factors on virus antibody responses. EBV/KSHV co-infection (OR = 5.71(1.58-7.12)), HIV positivity (OR = 2.22(1.32-3.73)) and living in a more rural area (OR = 1.38(1.01-1.89)) are strongly associated with immunogenicity. GWAS reveals associations with KSHV antibody response in the HLA-B/C region (p = 6.64 × 10-09). For EBV, associations are identified for VCA (rs71542439, p = 1.15 × 10-12). Human leucocyte antigen (HLA) and trans-ancestry fine-mapping substantiate that distinct variants in HLA-DQA1 (p = 5.24 × 10-44) are driving associations for EBNA-1 in Africa. This study highlights complex interactions between KSHV and EBV, in addition to distinct genetic architectures resulting in important differences in pathogenesis and transmission.

Conserved CxnC Motifs in Kaposi's Sarcoma-Associated Herpesvirus ORF66 Are Required for Viral Late Gene Expression and Are Essential for Its Interaction with ORF34

Late gene transcription in the beta- and gammaherpesviruses depends on a set of virally encoded transcriptional activators (vTAs) that hijack the host transcriptional machinery and direct it to a subset of viral genes that are required for completion of the viral replication cycle and capsid assembly. In Kaposi's sarcoma-associated herpesvirus (KSHV), these vTAs are encoded by ORF18, ORF24, ORF30, ORF31, ORF34, and ORF66. Assembly of the vTAs into a complex is critical for late gene transcription, and thus, deciphering the architecture of the complex is central to understanding its transcriptional regulatory activity. Here, we generated an ORF66-null virus and confirmed that it fails to produce late genes and infectious virions. We show that ORF66 is incorporated into the vTA complex primarily through its interaction with ORF34, which is dependent upon a set of four conserved cysteine-rich motifs in the C-terminal domain of ORF66. While both ORF24 and ORF66 occupy the canonical K8.1 late gene promoter, their promoter occupancy requires the presence of the other vTAs, suggesting that sequence-specific, stable binding requires assembly of the entire complex on the promoter. Additionally, we found that ORF24 expression is impaired in the absence of a stable vTA complex. This work extends our knowledge about the architecture of the KSHV viral preinitiation complex and suggests that it functions as a complex to recognize late gene promoters.IMPORTANCE Kaposi's sarcoma-associated herpesvirus (KSHV; human herpesvirus 8) is an oncogenic gammaherpesvirus that is the causative agent of multiple human cancers. The release of infectious virions requires the production of capsid proteins and other late genes, whose production is transcriptionally controlled by a complex of six virally encoded proteins that hijack the host transcription machinery. It is poorly understood how this complex assembles or what function five of its six components play in transcription. Here, we demonstrate that ORF66 is an essential component of this complex in KSHV and that its inclusion in the complex depends upon its C-terminal domain, which contains highly conserved cysteine-rich motifs reminiscent of zinc finger motifs. Additionally, we examined the assembly of the viral preinitiation complex at late gene promoters and found that while sequence-specific binding of late gene promoters requires ORF24, it additionally requires a fully assembled viral preinitiation complex.

Mutual detection of Kaposi's sarcoma-associated herpesvirus and Epstein-Barr virus in blood and saliva of Cameroonians with and without Kaposi's sarcoma

Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein-Barr virus (EBV) are prevalent in sub-Saharan Africa, together with HIV; the consequent burden of disease is grave. The cofactors driving transmission of the two viruses and pathogenesis of associated malignancies are not well understood. We measured KSHV and EBV DNA in whole blood and saliva as well as serum antibodies levels in 175 Cameroonians with Kaposi's sarcoma and 1,002 age- and sex-matched controls with and without HIV. KSHV seroprevalence was very high (81%) in controls, while EBV seroprevalence was 100% overall. KSHV DNA was detectable in the blood of 36-46% of cases and 6-12% of controls; EBV DNA was detected in most participants (72-89%). In saliva, more cases (50-58%) than controls (25-28%) shed KSHV, regardless of HIV infection. EBV shedding was common (75-100%); more HIV+ than HIV- controls shed EBV. Cases had higher KSHV and EBV VL in blood and saliva then controls, only among HIV+ participants. KSHV and EBV VL were also higher in HIV+ than in HIV- controls. Cases (but not controls) were more likely to have detectable KSHV in blood if they also had EBV, whereas shedding of each virus in saliva was independent. While EBV VL in saliva and blood were modestly correlated, no correlation existed for KSHV. Numerous factors, several related to parasitic coinfections, were associated with detection of either virus or with VL. These findings may help better understand the interplay between the two gammaherpesviruses and generally among copathogens contributing to cancer burden in sub-Saharan Africa.

A multivalent Kaposi sarcoma-associated herpesvirus-like particle vaccine capable of eliciting high titers of neutralizing antibodies in immunized rabbits

Kaposi sarcoma-associated herpesvirus (KSHV) is an emerging pathogen and the causative agent of multiple cancers in immunocompromised patients. To date, there is no licensed prophylactic KSHV vaccine. In this study, we generated a novel subunit vaccine that incorporates four key KSHV envelope glycoproteins required for viral entry in diverse cell types (gpK8.1, gB, and gH/gL) into a single multivalent KSHV-like particle (KSHV-LP). Purified KSHV-LPs were similar in size, shape, and morphology to KSHV virions. Vaccination of rabbits with adjuvanted KSHV-LPs generated strong glycoprotein-specific antibody responses, and purified immunoglobulins from KSHV-LP-immunized rabbits neutralized KSHV infection in epithelial, endothelial, fibroblast, and B cell lines (60-90% at the highest concentration tested). These findings suggest that KSHV-LPs may be an ideal platform for developing a safe and effective prophylactic KSHV vaccine. We envision performing future studies in animal models that are susceptible to KSHV infection, to determine correlates of immune protection in vivo.

An integrative approach identifies direct targets of the late viral transcription complex and an expanded promoter recognition motif in Kaposi's sarcoma-associated herpesvirus

The structural proteins of DNA viruses are generally encoded by late genes, whose expression relies on recruitment of the host transcriptional machinery only after the onset of viral genome replication. β and γ-herpesviruses encode a unique six-member viral pre-initiation complex (vPIC) for this purpose, although how the vPIC directs specific activation of late genes remains largely unknown. The specificity underlying late transcription is particularly notable given that late gene promoters are unusually small, with a modified TATA-box being the only recognizable element. Here, we explored the basis for this specificity using an integrative approach to evaluate vPIC-dependent gene expression combined with promoter occupancy during Kaposi's sarcoma-associated herpesvirus (KSHV) infection. This approach distinguished the direct and indirect targets of the vPIC, ultimately revealing a novel promoter motif critical for KSHV vPIC binding. Additionally, we found that the KSHV vPIC component ORF24 is required for efficient viral DNA replication and identified a ORF24 binding element in the origin of replication that is necessary for late gene promoter activation. Together, these results identify an elusive element that contributes to vPIC specificity and suggest novel links between KSHV DNA replication and late transcription.

Kaposi sarcoma

Kaposi sarcoma (KS) gained public attention as an AIDS-defining malignancy; its appearance on the skin was a highly stigmatizing sign of HIV infection during the height of the AIDS epidemic. The widespread introduction of effective antiretrovirals to control HIV by restoring immunocompetence reduced the prevalence of AIDS-related KS, although KS does occur in individuals with well-controlled HIV infection. KS also presents in individuals without HIV infection in older men (classic KS), in sub-Saharan Africa (endemic KS) and in transplant recipients (iatrogenic KS). The aetiologic agent of KS is KS herpesvirus (KSHV; also known as human herpesvirus-8), and viral proteins can induce KS-associated cellular changes that enable the virus to evade the host immune system and allow the infected cell to survive and proliferate despite viral infection. Currently, most cases of KS occur in sub-Saharan Africa, where KSHV infection is prevalent owing to transmission by saliva in childhood compounded by the ongoing AIDS epidemic. Treatment for early AIDS-related KS in previously untreated patients should start with the control of HIV with antiretrovirals, which frequently results in KS regression. In advanced-stage KS, chemotherapy with pegylated liposomal doxorubicin or paclitaxel is the most common treatment, although it is seldom curative. In sub-Saharan Africa, KS continues to have a poor prognosis. Newer treatments for KS based on the mechanisms of its pathogenesis are being explored.

The Interaction between ORF18 and ORF30 Is Required for Late Gene Expression in Kaposi's Sarcoma-Associated Herpesvirus

In the beta- and gammaherpesviruses, a specialized complex of viral transcriptional activators (vTAs) coordinate to direct expression of virus-encoded late genes, which are critical for viral assembly and whose transcription initiates only after the onset of viral DNA replication. The vTAs in Kaposi's sarcoma-associated herpesvirus (KSHV) are ORF18, ORF24, ORF30, ORF31, ORF34, and ORF66. While the general organization of the vTA complex has been mapped, the individual roles of these proteins and how they coordinate to activate late gene promoters remain largely unknown. Here, we performed a comprehensive mutational analysis of the conserved residues in ORF18, which is a highly interconnected vTA component. Surprisingly, the mutants were largely selective for disrupting the interaction with ORF30 but not the other three ORF18 binding partners. Furthermore, disrupting the ORF18-ORF30 interaction weakened the vTA complex as a whole, and an ORF18 point mutant that failed to bind ORF30 was unable to complement an ORF18 null virus. Thus, contacts between individual vTAs are critical as even small disruptions in this complex result in profound defects in KSHV late gene expression.IMPORTANCE Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent of Kaposi's sarcoma and other B-cell cancers and remains a leading cause of death in immunocompromised individuals. A key step in the production of infectious virions is the transcription of viral late genes, which generates capsid and structural proteins and requires the coordination of six viral proteins that form a complex. The role of these proteins during transcription complex formation and the importance of protein-protein interactions are not well understood. Here, we focused on a central component of the complex, ORF18, and revealed that disruption of its interaction with even a single component of the complex (ORF30) prevents late gene expression and completion of the viral lifecycle. These findings underscore how individual interactions between the late gene transcription components are critical for both the stability and function of the complex.

Kaposi's Sarcoma-Associated Herpesvirus ORF68 Is a DNA Binding Protein Required for Viral Genome Cleavage and Packaging

Herpesviral DNA packaging into nascent capsids requires multiple conserved viral proteins that coordinate genome encapsidation. Here, we investigated the role of the ORF68 protein of Kaposi's sarcoma-associated herpesvirus (KSHV), a protein required for viral DNA encapsidation whose function remains largely unresolved across the herpesviridae. We found that KSHV ORF68 is expressed with early kinetics and localizes predominantly to viral replication compartments, although it is dispensable for viral DNA replication and gene expression. However, in agreement with its proposed role in viral DNA packaging, KSHV-infected cells lacking ORF68 failed to cleave viral DNA concatemers, accumulated exclusively immature B capsids, and released no infectious progeny virions. ORF68 has no predicted domains aside from a series of putative zinc finger motifs. However, in vitro biochemical analyses of purified ORF68 protein revealed that it robustly binds DNA and is associated with nuclease activity. These activities provide new insights into the role of KSHV ORF68 in viral genome encapsidation.IMPORTANCE Kaposi's sarcoma-associated herpesvirus (KSHV) is the etiologic agent of Kaposi's sarcoma and several B-cell cancers, causing significant morbidity and mortality in immunocompromised individuals. A critical step in the production of infectious viral progeny is the packaging of the newly replicated viral DNA genome into the capsid, which involves coordination between at least seven herpesviral proteins. While the majority of these packaging factors have been well studied in related herpesviruses, the role of the KSHV ORF68 protein and its homologs remains unresolved. Here, using a KSHV mutant lacking ORF68, we confirm its requirement for viral DNA processing and packaging in infected cells. Furthermore, we show that the purified ORF68 protein directly binds DNA and is associated with a metal-dependent cleavage activity on double-stranded DNA in vitro These activities suggest a novel role for ORF68 in herpesviral genome processing and encapsidation.

Age of Infection with Kaposi Sarcoma-Associated Herpesvirus and Subsequent Antibody Values Among Children in Uganda

We investigated associations between Kaposi sarcoma-associated herpesvirus (KSHV) seroconversion age and KSHV antibody values in Ugandan children. Every annual delay in KSHV seroconversion age was associated with a reduction of 19% (P < 0.0001) in K8.1 and 27% (P < 0.0001) in ORF73 antibody values at 6 years of age. Early infection may be an important risk factor for KSHV pathogenesis and viral shedding in saliva, leading to transmission.

T-cell responses to KSHV infection: a systematic approach

Prior studies of T-cell responses to KSHV have included relatively few participants and focused on relatively few KSHV antigens. To provide a more comprehensive analysis, we investigated T-cell responses to the whole KSHV proteome using IFN-γ ELISpot. Using ∼7,500 overlapping 15mer peptides we generated one to three peptide pools for each of the 82 KSHV ORFs. IFN-γ ELISpot analysis of PBMCs from 19 patients with a history of KSHV-associated disease and 24 healthy donors (11 KSHV seropositive) detected widely varied responses. Fifty six of the 82 ORFs were recognized by at least one individual but there was little overlap between participants. Responses to at least one ORF pool were observed in all 19 patients and in 7 seropositive donors. Four seropositive donors and 10 seronegative donors had no detectable responses while 3 seronegative donors had weak responses to one ORF. Patients recognised more ORFs than the donors (p=0.04) but the response intensity (spot forming units: SFU per million cells) was similar in the two groups. In four of the responding donors, individual peptides eliciting the predominant responses were identified: three donors responded to only one peptide per ORF, while one recognized five. Using intracellular cytokine staining in four participant samples, we detected peptide-induced IFN-γ, MIP1-β, and TNF-α as well as CD107a degranulation, consistent with multifunctional effector responses in CD8+ and CD4+ T cells. Sequence analysis of TCRs present in peptide specific T-cell clones generated from two participants showed both mono- and multi-clonotypic responses. Finally, we molecularly cloned the KSHV specific TCRs and incorporated the sequences into retroviral vectors to transfer the specificities to fresh donor cells for additional studies. This study suggests that KSHV infected individuals respond to diverse KSHV antigens, consistent with a lack of shared immunodominance and establishes useful tools to facilitate KSHV immunology studies.

The "Topological Train Ride" of a viral long non-coding RNA

As the notion of small molecule targeting of regulatory viral and cellular RNAs gathers momentum, understanding their structure, and variations thereof, in the appropriate biological context will play a critical role. This is especially true of the ∼1100-nt polyadenylated nuclear (PAN) long non-coding (lnc) RNA of Kaposi's sarcoma herpesvirus (KSHV), whose interaction with viral and cellular proteins is central to lytic infection. Nuclear accumulation of PAN RNA is mediated via a unique triple helical structure at its 3' terminus (within the expression and nuclear retention element, or ENE) which protects it from deadenylation-dependent decay. Additionally, significant levels of PAN RNA have been reported in both the cytoplasm of KSHV-infected cells and in budding virions, leading us to consider which viral and host proteins might associate with, or dissociate from, this lncRNA during its "journey" through the cell. By combining the power of SHAPE-mutational profiling (SHAPE-MaP) with large scale virus culture facilities of the National Cancer Institute, Frederick MD, Sztuba-Solinska et al. have provide the first detailed description of KSHV PAN nucleoprotein complexes in multiple biological contexts, complementing this by mapping sites of recombinant KSHV proteins on an in vitro-synthesized, polyadenylated counterpart.

Kaposi's sarcoma-associated herpesvirus polyadenylated nuclear RNA: a structural scaffold for nuclear, cytoplasmic and viral proteins

Kaposi's sarcoma-associated herpes virus (KSHV) polyadenylated nuclear (PAN) RNA facilitates lytic infection, modulating the cellular immune response by interacting with viral and cellular proteins and DNA. Although a number nucleoprotein interactions involving PAN have been implicated, our understanding of binding partners and PAN RNA binding motifs remains incomplete. Herein, we used SHAPE-mutational profiling (SHAPE-MaP) to probe PAN in its nuclear, cytoplasmic or viral environments or following cell/virion lysis and removal of proteins. We thus characterized and put into context discrete RNA structural elements, including the cis-acting Mta responsive element and expression and nuclear retention element (1,2). By comparing mutational profiles in different biological contexts, we identified sites on PAN either protected from chemical modification by protein binding or characterized by a loss of structure. While some protein binding sites were selectively localized, others were occupied in all three biological contexts. Individual binding sites of select KSHV gene products on PAN RNA were also identified in in vitro experiments. This work constitutes the most extensive structural characterization of a viral lncRNA and interactions with its protein partners in discrete biological contexts, providing a broad framework for understanding the roles of PAN RNA in KSHV infection.

Molecular diversity of IgG responses to Epstein-Barr virus proteins in asymptomatic Epstein-Barr virus carriers

The Epstein-Barr virus (EBV) is a ubiquitous pathogen that infects over 90 % of adults. EBV is the primary etiological agent of infectious mononucleosis and is closely associated with nasopharyngeal carcinoma, gastric carcinoma, Hodgkin lymphoma and Burkitt lymphoma. Clinical serological assays for EBV diagnosis only survey a small portion of the viral proteome, which does not represent the total antigenic breadth presented to the immune system during viral infection. In this study, we have generated an expression library containing the majority of EBV ORFs, and have systematically evaluated IgG responses to those EBV proteins in sera from EBV carriers. In addition to confirming previously recognized dominant EBV antigens, this study has identified additional immunodominant antigens, and has revealed a more expansive antigenic profile of the humoral responses to EBV in asymptomatic carriers. This EBV expression library will be deposited in a public repository with the goal of disseminating this new research tool for the application of identifying potential new biomarkers for EBV-associated diseases.

microRNA dependent and independent deregulation of long non-coding RNAs by an oncogenic herpesvirus

Kaposi’s sarcoma (KS) is a highly prevalent cancer in AIDS patients, especially in sub-Saharan Africa. Kaposi’s sarcoma-associated herpesvirus (KSHV) is the etiological agent of KS and other cancers like Primary Effusion Lymphoma (PEL). In KS and PEL, all tumors harbor latent KSHV episomes and express latency-associated viral proteins and microRNAs (miRNAs). The exact molecular mechanisms by which latent KSHV drives tumorigenesis are not completely understood. Recent developments have highlighted the importance of aberrant long non-coding RNA (lncRNA) expression in cancer. Deregulation of lncRNAs by miRNAs is a newly described phenomenon. We hypothesized that KSHV-encoded miRNAs deregulate human lncRNAs to drive tumorigenesis. We performed lncRNA expression profiling of endothelial cells infected with wt and miRNA-deleted KSHV and identified 126 lncRNAs as putative viral miRNA targets. Here we show that KSHV deregulates host lncRNAs in both a miRNA-dependent fashion by direct interaction and in a miRNA-independent fashion through latency-associated proteins. Several lncRNAs that were previously implicated in cancer, including MEG3, ANRIL and UCA1, are deregulated by KSHV. Our results also demonstrate that KSHV-mediated UCA1 deregulation contributes to increased proliferation and migration of endothelial cells.

KS is the most prevalent cancer associated with AIDS in sub-Saharan Africa, and is also common in males not affected by AIDS. KSHV manipulates human cells by targeting protein-coding genes and cell signaling. Here we show that KSHV alters the expression of hundreds of human lncRNAs, a broad class of regulatory molecules involved in a variety of cellular pathways including cell cycle and apoptosis. KSHV uses both latency proteins and miRNAs to target lncRNAs. miRNA-mediated targeting of lncRNAs is a novel regulatory mechanism of gene expression. Given that most herpesviruses encode miRNAs, this mechanism might be a common theme during herpesvirus infections. Understanding lncRNA deregulation by KSHV will help decipher the important molecular mechanisms underlying viral pathogenesis and tumorigenesis.