Michael P. Busch

Genetic variation in IL28B and spontaneous clearance of hepatitis C virus

Hepatitis C virus (HCV) infection is the most common blood-borne infection in the United States, with estimates of 4 million HCV-infected individuals in the United States and 170 million worldwide. Most (70–80%) HCV infections persist and about 30% of individuals with persistent infection develop chronic liver disease, including cirrhosis and hepatocellular carcinoma. Epidemiological, viral and host factors have been associated with the differences in HCV clearance or persistence, and studies have demonstrated that a strong host immune response against HCV favours viral clearance. Thus, variation in genes involved in the immune response may contribute to the ability to clear the virus. In a recent genome-wide association study, a single nucleotide polymorphism (rs12979860) 3 kilobases upstream of the IL28B gene, which encodes the type III interferon IFN-λ3, was shown to associate strongly with more than a twofold difference in response to HCV drug treatment. To determine the potential effect of rs12979860 variation on outcome to HCV infection in a natural history setting, we genotyped this variant in HCV cohorts comprised of individuals who spontaneously cleared the virus (n = 388) or had persistent infection (n = 620). We show that the C/C genotype strongly enhances resolution of HCV infection among individuals of both European and African ancestry. To our knowledge, this is the strongest and most significant genetic effect associated with natural clearance of HCV, and these results implicate a primary role for IL28B in resolution of HCV infection.

The Risk of Transfusion-Transmitted Viral Infections

Background Accurate estimates of the risk of transfusion-transmitted infectious disease are essential for monitoring the safety of the blood supply and evaluating the potential effect of new screening tests. We estimated the risk of transmitting the human immunodeficiency virus (HIV), the human T-cell lymphotropic virus (HTLV), the hepatitis C virus (HCV), and the hepatitis B virus (HBV) from screened blood units donated during the window period following a recent, undetected infection. Methods Using data on 586,507 persons who each donated blood more than once between 1991 and 1993 at five blood centers (for a total of 2,318,356 allogeneic blood donations), we calculated the incidence rates of seroconversion among those whose donations passed all the screening tests used. We adjusted these rates for the estimated duration of the infectious window period for each virus. We then estimated the further reductions in risk that would result from the use of new and more sensitive viral-antigen or nucleic acid s...

Identification and characterization of transmitted and early founder virus envelopes in primary HIV-1 infection

The precise identification of the HIV-1 envelope glycoprotein (Env) responsible for productive clinical infection could be instrumental in elucidating the molecular basis of HIV-1 transmission and in designing effective vaccines. Here, we developed a mathematical model of random viral evolution and, together with phylogenetic tree construction, used it to analyze 3,449 complete env sequences derived by single genome amplification from 102 subjects with acute HIV-1 (clade B) infection. Viral env genes evolving from individual transmitted or founder viruses generally exhibited a Poisson distribution of mutations and star-like phylogeny, which coalesced to an inferred consensus sequence at or near the estimated time of virus transmission. Overall, 78 of 102 subjects had evidence of productive clinical infection by a single virus, and 24 others had evidence of productive clinical infection by a minimum of two to five viruses. Phenotypic analysis of transmitted or early founder Envs revealed a consistent pattern of CCR5 dependence, masking of coreceptor binding regions, and equivalent or modestly enhanced resistance to the fusion inhibitor T1249 and broadly neutralizing antibodies compared with Envs from chronically infected subjects. Low multiplicity infection and limited viral evolution preceding peak viremia suggest a finite window of potential vulnerability of HIV-1 to vaccine-elicited immune responses, although phenotypic properties of transmitted Envs pose a formidable defense.

The seroepidemiology of human herpesvirus 8 (Kaposi's sarcoma-associated herpesvirus) : distribution of infection in KS risk groups and evidence for sexual transmission

Striking differences in Kaposis sarcoma (KS) risk for AIDS patients who acquire HIV via homosexual activity and those whose HIV infections derive from blood product exposure suggest the presence of a sexually transmitted agent other than HIV in the development of KS. Using an immunofluorescence assay, we examined serum samples from 913 patients for the presence of antibody specific for infection by human herpesvirus 8 (HHV8), an agent whose genome is regularly found in KS tissue. The distribution of HHV8 seropositivity conforms to that expected for a sexually transmitted pathogen and tracks closely with the risk for KS development. Our data support the inference that this virus is the etiologic cofactor predicted by the epidemiology of KS.

Maternal alloantigens promote the development of tolerogenic fetal regulatory T cells in utero.

As the immune system develops, T cells are selected or regulated to become tolerant of self antigens and reactive against foreign antigens. In mice, the induction of such tolerance is thought to be attributable to the deletion of self-reactive cells. Here, we show that the human fetal immune system takes advantage of an additional mechanism: the generation of regulatory T cells (Tregs) that suppress fetal immune responses. We find that substantial numbers of maternal cells cross the placenta to reside in fetal lymph nodes, inducing the development of CD4+CD25highFoxP3+ Tregs that suppress fetal antimaternal immunity and persist at least until early adulthood. These findings reveal a form of antigen-specific tolerance in humans, induced in utero and probably active in regulating immune responses after birth.

A new strategy for estimating risks of transfusion-transmitted viral infections based on rates of detection of recently infected donors

BACKGROUND:  Estimates for human immunodeficiency virus (HIV)‐1 and hepatitis C virus (HCV) transfusion‐transmitted risks have relied on incidence derived from repeat donor histories and imprecise estimates for infectious, preseroconversion window periods (WPs).

Time course of detection of viral and serologic markers preceding human immunodeficiency virus type 1 seroconversion: implications for screening of blood and tissue donors

BACKGROUND: Almost all human immunodeficiency virus (HIV) transmission via blood or tissues that has occurred since anti‐HIV screening was implemented in 1985 is traceable to blood given after infection but before antibody seroconversion, a time that is referred to as the window period. In this study, the performance of newer assays designed to detect viral and serologic markers soon after infection is assessed, and the reduction in the window period achieved by these assays is estimated. STUDY DESIGN AND METHODS: Three cohort studies of persons at high risk for acquiring HIV infection were identified. These studies included well‐controlled HIV type 1 (HIV‐1) polymerase chain reaction (PCR) analyses of serial preseroconversion specimens from HIV‐1‐ seroconverting homosexual men or intravenous drug users. Of 81 enrollees with anti‐HIV‐1 seroconversion documented by a viral lysate anti‐HIV‐1 enzyme immunosorbent assay (EIA) available in 1989, 13 (16%) had PCR‐positive preseroconversion specimens. In the present study, sera from these 13 PCR‐positive samples were further tested for anti‐ HIV by 10 contemporary EIAs and 6 supplemental assays, as well as being tested for plasma p24 antigen and HIV‐1 RNA. Preseroconversion sera from 38 HIV‐1 DNA PCR‐negative cohort participants were also tested by selected anti‐HIV EIAs and tested for p24 antigen and HIV‐1 RNA. On the basis of these laboratory data and the intervals between blood drawing in all 81 men, the reduction in the preseroconversion window period achieved by these new assays was estimated with a mathematical model developed to analyze seroconversion data. RESULTS: Nine (69%) of the 13 preseroconversion PCR‐positive samples had anti‐HIV that was detectable by one or more contemporary anti‐HIV‐1 or anti‐HIV type 2 EIA. Supplemental antibody assays were negative on all four EIA‐nonreactive preseroconversion samples and negative or indeterminate on a high proportion of the nine EIA‐reactive PCR‐positive samples. Eight (61%) of the 13 samples were p24 antigen‐positive, and 11 (85%) were HIV‐1 RNA‐positive. The estimated reductions in the window period (relative to the index viral lysate‐based anti‐HIV EIA) were as follows: contemporary anti‐HIV‐1/2 EIAs, 20.3 days (95% Cl, 8.0–32.5); p24 antigen and DNA PCR, 26.4 days (95% Cl, 12.6–38.7); and RNA PCR, 31.0 days (95% Cl, 16.7–45.3). CONCLUSION: Recent improvement in the sensitivity of anti‐HIV assays has resulted in significant shortening of the preseroconversion window period. Consequently, the incremental reduction in the window period that could be achieved by implementing direct virus‐detection assays has diminished significantly.

Hepatitis C Virus Seroconversion among Young Injection Drug Users: Relationships and Risks

The present study examined reasons for the high incidence of hepatitis C virus (HCV) infection among young injection drug users (IDUs). IDUs <30 years old who tested negative for HCV antibody were enrolled in a prospective cohort. Risk factors for seroconversion were examined using time-dependent regression analyses: 48 of 195 IDUs seroconverted to HCV, for an incidence rate of 25.1/100 person-years (95% confidence interval, 18.7-32.9/100 person-years). Independent risk factors included sharing needles with an HCV-infected sex partner (borderline statistical significance, P=.11) or a person who was not a sex partner, sharing nonsterile drug-preparation equipment, pooling money with another IDU to buy drugs, and exchanging sex for money. Ubiquitous behaviors among young IDUs, such as the forming of injecting or sexual partnerships and consequent sharing of needles and drug preparation equipment, are risk factors for HCV. Interventions to reduce HCV transmission must recognize the importance of relationships on injecting risk.

Use of laboratory tests and clinical symptoms for identification of primary HIV infection

Objective To determine the sensitivity and specificity of symptoms, three HIV-1 RNA assays, a p24 antigen EIA and a third-generation enzyme immunoassay (EIA) antibody test for diagnosis of primary HIV infection (PHI). Design Prospective cohort in a university research program. Participants Of 258 eligible persons screened for PHI, 40 had primary/early infection (22 preseroconversion, 18 within 6 months of seroconversion) and 218 did not. Seven participants with preseroconversion HIV-1 from a second center were added for evaluating laboratory tests. Main outcome measure PHI, defined as a negative or indeterminate antibody test with subsequent conversion. Symptom analysis also included persons with antibody conversion of less than 6 months’ duration. Results The symptoms most strongly associated with PHI in multivariate analysis were fever [odds ratio (OR) 5.2; 95% confidence interval (CI) 2.3–11.7] and rash (OR 4.8; 95% CI 2.4–9.8). The sensitivity and specificity, respectively, for detecting preseroconversion HIV infection were: p24 antigen, 79% and 99%; third-generation EIA, 79% and 97%; HIV-1 RNA by branched chain DNA 100% and 95%; HIV-1 RNA by polymerase chain reaction 100% and 97%; HIV-1 RNA by transcription-mediated amplification testing, 100% and 98%. False-positive HIV-1 RNA tests were not reproducible and had values < 3000 copies/ml, while only one person with confirmed PHI was in this range. Conclusions Rash and fever indicated the highest risk of PHI. HIV-1 RNA tests are very sensitive for PHI but false-positive results occur. False-positive results can be reduced through duplicate testing and considering tests < 5000 copies/ml as indeterminate results requiring additional testing. p24 antigen was more specific than HIV-1 RNA testing but less sensitive.

Comparative sensitivity of HBV NATs and HBsAg assays for detection of acute HBV infection

BACKGROUND: A study was designed to estimate relative analytic sensitivity and window‐period (WP) closure and to project incremental yield of newer HBsAg tests, pooled‐sample NAT, and single‐sample NAT, compared to currently licensed HBsAg tests.