Background. Kaposi sarcoma (KS)-associated herpesvirus (KSHV) is etiologically linked to all KS forms, but mechanisms underlying KS development are unclear. The incidence of KS in human immunodeficiency virus type 1-infected (HIV-1 + ) individuals implicates immune dysregulation; however, the lack of characterization of KSHV immune responses in endemic KS makes the role of HIV-1 unclear. The study objective was to investigate the HIV-1 and KSHV roles in viral nucleic acid detection, antibody responses, and cytokine responses in polymerase chain reaction-confirmed epidemic KS and endemic KS patients and non-cancer controls from sub-Saharan Africa.Methods. KSHV viral DNA (vDNA), total anti-KSHV antibody, KSHV neutralizing antibody (nAb), and cytokines were quantified.Results. KSHV vDNA was detectable in tumors but variably in plasma and peripheral blood mononuclear cells. Consistent with elevated antibody-associated cytokines (interleukin [IL] 6, IL-5, and IL-10), nAb titers were higher in epidemic KS and endemic KS patients than in controls (P < .05). Despite HIV-1 coinfection in epidemic KS, nAb titers were similar between epidemic KS and endemic KS patients (P = 0.3).Conclusions. Similarities in antibody and cytokine responses between epidemic and endemic KS patients suggest that KSHV drives KS pathogenesis, whereas HIV-1 exacerbates it.

By selecting the R5 human immunodeficiency virus type 1 (HIV-1) strain JR-CSF for efficient use of a CCR5 coreceptor with a badly damaged amino terminus [i.e., CCR5(Y14N)], we previously isolated variants that weakly utilize CCR5(⌬18), a low-affinity mutant lacking the normal tyrosine sulfate-containing amino-terminal region of the coreceptor. These previously isolated HIV-1 JR-CSF variants contained adaptive mutations situated exclusively in the V3 loop of their gp120 envelope glycoproteins. We now have weaned the virus from all dependency on the CCR5 amino terminus by performing additional selections with HeLa-CD4 cells that express only a low concentration of CCR5(⌬18). The adapted variants had additional mutations in their V3 loops, as well as one in the V2 stem (S193N) and four alternative mutations in the V4 loop that eliminated the same Nlinked oligosaccharide from position N403. Assays using pseudotyped viruses suggested that these new gp120 mutations all made strong contributions to use of CCR5(⌬18) by accelerating a rate-limiting CCR5-dependent conformational change in gp41 rather than by increasing viral affinity for this damaged coreceptor. Consistent with this interpretation, loss of the V4 N-glycan at position N403 also enhanced HIV-1 use of a different lowaffinity CCR5 coreceptor with a mutation in extracellular loop 2 (ECL2) [i.e., CCR5(G163R)], whereas the double mutant CCR5(⌬18,G163R) was inactive. We conclude that loss of the N-glycan at position N403 helps to convert the HIV-1 envelope into a hair-trigger form that no longer requires strong interactions with both the CCR5 amino terminus and ECL2 but efficiently uses either site alone. These results demonstrate a novel functional role for a gp120 N-linked oligosaccharide and a high degree of adaptability in coreceptor usage by HIV-1.The human immunodeficiency virus type 1 (HIV-1) infection pathway involves a sequential process whereby reversible binding to the CD4 receptor induces a conformational change in the viral gp120-gp41 trimeric complexes that exposes or induces formation of previously inaccessible epitopes in both gp120 and gp41 and dramatically enhances gp120 affinity for a coreceptor (46,57,65,69,71,73,75). Energetic studies have suggested that the gp120 subunit has a high entropy or conformational flexibility that inhibits binding of antibodies or other ligands and that binding to CD4 substantially reduces this flexibility, thus enhancing the subsequent binding of gp120 to additional ligands by an energetic (entropic) mechanism (36, 47). The sequential reversible binding of gp120 to CD4 and to a coreceptor is believed to lower the activation energy for irreversible conformational changes in the metastable gp41 subunits. These conformational changes pull the virus tightly onto the cell surface and induce fusion of the viral and cellular membranes (9, 24).The gp120 glycoprotein contains an inner core of conserved sequences and several variable loops that are heavily N-glycosylated and that form a protective surface shell (8,32,41,55,...

Kaposi sarcoma-associated herpesvirus (KSHV) is the etiologic agent for Kaposi Sarcoma (KS), the most common cancer diagnosed in HIV- infected patients. The role of neutralizing antibodies in KS pathogenesis and in KSHV infected individuals is not clearly understood. The goal of this study was to investigate and compare the prevalence and titers of neutralizing antibodies in plasma samples from KS patients and KSHV infected asymptomatic individuals from Zambia, a KS endemic region in sub-Saharan Africa. Plasma samples (N = 267) consisting of KS patients (group 1) and asymptomatic individuals (group 2) were collected from Lusaka, Zambia. A flow cytometry based quantitative neutralization assay utilizing recombinant KSHV expressing GFP was used to detect KSHV neutralizing antibodies. Our results show that the overall prevalence of neutralizing antibodies in KS patients (group 1) was 66.7% which was significantly higher than the prevalence of 6.5% present in KSHV infected asymptomatic individuals (group 2). Total antibody titers as well as neutralizing antibodies titers were found to be significantly higher among KS patients. It is likely that higher neutralizing antibodies prevalence and titers in KS patients result from higher levels of antigenic stimulation over time. This study is first to compare prevalence and titers of neutralizing antibodies in participants with and without disease from a KSHV endemic region.

Selection of a minor viral genotype during perinatal transmission of human Immunodeficiency virus type 1 (HIV-1) has been observed, but there is a lack of information on the correlation of the restrictive transmission with biological properties of the virus, such as replicative fitness. Recombinant viruses expressing the enhanced green fluorescent protein or the Discosoma sp. red fluorescent (DsRed2) protein carrying the V1 to V5 regions of env from seven mother-infant pairs (MIPs) infected by subtype C HIV-1 were constructed, and competition assays were carried out to compare the fitness between the transmitted and nontransmitted viruses. Flow cytometry was used to quantify the frequency of infected cells, and the replicative fitness was determined based on a calculation that takes into account replication of competing viruses in a single infection versus dual infections. Transmitted viruses from five MIPs with the mothers chronically infected showed a restrictive env genotype, and all the recombinant viruses carrying the infants' Env had higher replicative fitness than those carrying the Env from the mothers. This growth fitness is lineage specific and can be observed only within the same MIP. In contrast, in two MIPs where the mothers had undergone recent acute infection, the viral Env sequences were similar between the mothers and infants and showed no further restriction in quasispecies during perinatal transmission. The recombinant viruses carrying the Env from the infants' viruses also showed replication fitness similar to those carrying the mothers' Env proteins. Our results suggest that newly transmitted viruses from chronically infected mothers have been selected to have higher replicative fitness to favor transmission, and this advantage is conferred by the V1 to V5 region of Env of the transmitted viruses. This finding has important implications for vaccine design or development of strategies to prevent HIV-1 transmission.

Objective: Kaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent for Kaposi's sarcoma (KS), one of the most common cancers in Tanzania. We have investigated KSHV prevalence and factors associated with KSHV infection in Tanzania. Methods: This is a cross-sectional study of voluntary blood-donors from Dar es Salaam, Tanzania. Plasma was screened for KSHV, HIV-1, HBV, HCV and Treponema pallidum (syphilis). Associations between KSHV sero-status and risk factors were analyzed. Odds ratios (OR) and 95% confidence intervals (CI) are reported to evaluate risk factors of KSHV infection. All tests were 2-tailed, and P-values <0.05 were considered statistically significant. Results: The overall KSHV seroprevalence was 56.9%. Significantly increased risk of KSHV infection was detected in persons from the Lake and Central Zones (OR = 6.4, 95% CI = 1.6-25.3, P = 0.008 and OR = 5.7, 95% CI = 1.0-32.5, P = 0.048 respectively). A trend toward increased risk of KSHV infection with HIV-1 coinfection was not significant (OR = 2.8, 95% CI = 1.0-8.0, P = 0.06). Seroreactivity to T. pallidum was surprisingly high (14.9%). Conclusion:The prevalence of KSHV infection and syphilis was high among Tanzanian blood-donors. The most common transfusion-transmissible infections did not associate with KSHV infection. Regions of focal KSHV infection need further investigation for underappreciated risk factors.