Paul W. Stewart

Human susceptibility and resistance to Norwalk virus infection

Infectious diseases have influenced population genetics and the evolution of the structure of the human genome in part by selecting for host susceptibility alleles that modify pathogenesis. Norovirus infection is associated with ∼90% of epidemic non-bacterial acute gastroenteritis worldwide. Here, we show that resistance to Norwalk virus infection is multifactorial. Using a human challenge model, we showed that 29% of our study population was homozygous recessive for the α(1,2)fucosyltransferase gene (FUT2) in the ABH histo-blood group family and did not express the H type-1 oligosaccharide ligand required for Norwalk virus binding. The FUT2 susceptibility allele was fully penetrant against Norwalk virus infection as none of these individuals developed an infection after challenge, regardless of dose. Of the susceptible population that encoded a functional FUT2 gene, a portion was resistant to infection, suggesting that a memory immune response or some other unidentified factor also affords protection from Norwalk virus infection.

Brief but Efficient: Acute HIV Infection and the Sexual Transmission of HIV

BACKGROUND We examined whether viral dynamics in the genital tract during the natural history of acute human immunodeficiency virus type 1 (HIV-1) infection could explain efficient heterosexual transmission of HIV. METHODS We measured HIV-1 concentration in blood and semen samples from patients with acute and long-term HIV-1 infection. We explored the effect of changes in viral dynamics in semen on the probability of transmission per coital act, using a probabilistic model published elsewhere. RESULTS Considered over time from infection, semen HIV-1 concentrations, in men with acute infection, increase and decrease in approximate parallel with changes occurring in blood. Modeling suggests that these acute dynamics alone are sufficient to increase probability of heterosexual transmission by 8-10-fold between peak (day 20 after infection, based on the model) and virologic set points (day 54 and later after infection). Depending on the frequency of coitus, men with average semen HIV-1 loads and without sexually transmitted diseases (STDs) would be expected to infect 7%-24% of susceptible female sex partners during the first 2 months of infection. The predicted infection rate would be much higher when either partner has an STD. CONCLUSIONS Empirical biological data strongly support the hypothesis that sexual transmission by acutely infected individuals has a disproportionate effect on the spread of HIV-1 infection. Acute hyperinfectiousness may, in part, explain the current pandemic in heterosexual individuals.

Amplified transmission of HIV-1: comparison of HIV-1 concentrations in semen and blood during acute and chronic infection

Objectives:This study was conducted to compare viral dynamics in blood and semen between subjects with antibody negative, acute HIV-1 infection and other subjects with later stages of infection. Design:A prospective cohort study was embedded within a cross-sectional study of HIV screening in a Lilongwe, Malawi STD clinic. Methods:Blood samples from HIV antibody negative or indeterminate volunteers were used to detect HIV RNA in plasma using a pooling strategy. Blood and seminal plasma HIV-1 RNA concentrations were measured over 16 weeks. Results:Sixteen men with acute HIV infection and 25 men with chronic HIV infection were studied. Blood viral load in subjects with acute HIV infection was highest about 17 days after infection (mean ± SE, 6.9 ± 0.5 log10 copies/ml), while semen viral load peaked about 30 days after infection (4.5 ± 0.4 log10 copies/ml). Semen viral load declined by 1.7 log10 to a nadir by week 10 of HIV infection. Semen and blood viral loads were more stable in chronically infected subjects over 16 weeks. Higher semen levels of HIV RNA were noted in subjects with low CD4 cell counts. Conclusions:These results provide a biological explanation for reported increases in HIV transmission during the very early (acute) and late stages of infection. Recognizing temporal differences in HIV shedding in the genital tract is important in the development of effective HIV prevention strategies.

Effects of Reducing Dietary Saturated Fatty Acids on Plasma Lipids and Lipoproteins in Healthy Subjects: The Delta Study, Protocol 1

Few well-controlled diet studies have investigated the effects of reducing dietary saturated fatty acid (SFA) intake in premenopausal and postmenopausal women or in blacks. We conducted a multicenter, randomized, crossover-design trial of the effects of reducing dietary SFA on plasma lipids and lipoproteins in 103 healthy adults 22 to 67 years old. There were 46 men and 57 women, of whom 26 were black, 18 were postmenopausal women, and 16 were men > or =40 years old. All meals and snacks, except Saturday dinner, were prepared and served by the research centers. The study was designed to compare three diets: an average American diet (AAD), a Step 1 diet, and a low-SFA (Low-Sat) diet. Dietary cholesterol was constant. Diet composition was validated and monitored by a central laboratory. Each diet was consumed for 8 weeks, and blood samples were obtained during weeks 5 through 8. The compositions of the three diets were as follows: AAD, 34.3% kcal fat and 15.0% kcal SFA; Step 1, 28.6% kcal fat and 9.0% kcal SFA; and Low-Sat, 25.3% kcal fat and 6.1% kcal SFA. Each diet provided approximately 275 mg cholesterol/d. Compared with AAD, plasma total cholesterol in the whole group fell 5% on Step 1 and 9% on Low-Sat. LDL cholesterol was 7% lower on Step 1 and 11% lower on Low-Sat than on the AAD (both P<.01). Similar responses were seen in each subgroup. HDL cholesterol fell 7% on Step 1 and 11% on Low-Sat (both P<.01). Reductions in HDL cholesterol were seen in all subgroups except blacks and older men. Plasma triglyceride levels increased approximately 9% between AAD and Step 1 but did not increase further from Step 1 to Low-Sat. Changes in triglyceride levels were not significant in most subgroups. Surprisingly, plasma Lp(a) concentrations increased in a stepwise fashion as SFA was reduced. In a well-controlled feeding study, stepwise reductions in SFA resulted in parallel reductions in plasma total and LDL cholesterol levels. Diet effects were remarkably similar in several subgroups of men and women and in blacks. The reductions in total and LDL cholesterol achieved in these different subgroups indicate that diet can have a significant impact on risk for atherosclerotic cardiovascular disease in the total population.

Risk of child abuse or neglect in a cohort of low-income children

The purposes of this research were to identify risk factors for reported child abuse or neglect and to examine the roles of stress and social support in the etiology of child maltreatment. Mothers of newborn infants with biomedical and sociodemographic risk factors were recruited from community and regional hospitals and local health departments in 42 counties of North and South Carolina selected for geographic distribution and for large numbers of such newborns. For every four such mothers, the next mother to deliver an otherwise normal newborn was sought. Mothers were interviewed shortly after giving birth, and state Central Registries of Child Abuse and Neglect were reviewed when each infant was 1 year of age. Eight hundred forty-two of 1,111 recruited mothers were successfully interviewed in their homes between March 1986 and June 1987. Seven hundred forty-nine North Carolina births who resided in the state more than 6 months were eligible for inclusion in the analysis. Logistic regression with backward elimination procedures was used in the analysis. Maternal education (p < .01), number of other dependent children in the home (p < .01), receipt of Medicaid (p < .01), maternal depression (p < .05), and whether the maternal subject lived with her own mother at age 14 years (p < .05) were the best predictors of a maltreatment report. Further examination revealed an interaction effect between stressful life events, as measured by life event scores, and social well-being (p < .01). For children born at risk for social and/or medical problems, extreme low income (participation in public income support programs), low maternal education, maternal depression, the presence of any other young children in the home, and a mothers separation at age 14 years from her own mother significantly predict child maltreatment reports in the first year of life. In addition, stressful life events, even if perceived positively, may increase or decrease the risk of maltreatment reports, depending upon the presence of social support.

Antiretroviral drug exposure in the female genital tract: implications for oral pre- and post-exposure prophylaxis

Objectives:To describe first dose and steady state antiretroviral drug exposure in the female genital tract. Design:Non-blinded, single center, open-label pharmacokinetic study in HIV-infected women. Method:Twenty-seven women initiating combination antiretroviral therapy underwent comprehensive blood plasma and cervicovaginal fluid sampling for drug concentrations during the first dose of antiretroviral therapy and at steady-state. Drug concentrations were measured by validated HPLC/UV or HPLC-MS/MS methods. Pharmacokinetic parameters were estimated for 11 drugs by non-compartmental analysis. Descriptive statistics and 95% confidence intervals were generated using Intercooled STATA Release 8.0 (Stata Corporation, College Station, Texas, USA). Results:For all antiretroviral drugs, genital tract concentrations were detected rapidly after the first dose. Drugs were stratified according to the genital tract concentrations achieved relative to blood plasma. Median rank order of highest to lowest genital tract concentrations relative to blood plasma at steady state were: lamivudine (concentrations achieved were 411% greater than blood plasma), emtricitabine (395%), zidovudine (235%) tenofovir (75%), ritonavir (26%), didanosine (21%), atazanavir (18%), lopinavir (8%), abacavir (8%), stavudine (5%), and efavirenz (0.4%). Conclusions:This is the first study to comprehensively evaluate antiretroviral drug exposure in the female genital tract. These findings support the use of lamivudine, zidovudine, tenofovir and emtricitabine as excellent pre-exposure/post-exposure prophylaxis (PrEP/PEP) candidates. Atazanavir and lopinavir might be useful agents for these applications due to favorable therapeutic indices, despite lower genital tract concentrations. Agents such as stavudine, abacavir, and efavirenz that achieve genital tract exposures less than 10% of blood plasma are less attractive PrEP/PEP candidates.

Cigarette smoking, stress-induced analgesia and pain perception in men and women.

&NA; This study examined gender differences in smoking‐related analgesia and stress‐induced analgesia (SIA), as a function of pain modality. Forty men (20 smokers, 20 nonsmokers) and 37 women (17 smokers) were tested twice for pain sensitivity to tourniquet ischemia, thermal heat, and cold pressor tests; once following mental stress and once following rest control, counterbalancing order. Cardiovascular and neuroendocrine responses to mental stress were also examined. While expected gender differences in pain sensitivity were observed, women smokers had greater threshold and tolerance times to ischemic pain than women nonsmokers (P<0.05) when pain testing followed rest. Male smokers had greater threshold and tolerance to cold pressor pain than male nonsmokers (P<0.05) after both rest and stress. Only women showed evidence for SIA, since women nonsmokers demonstrated greater ischemic pain threshold and tolerance following mental stress versus rest (P<0.05), and all women reported lower thermal heat pain unpleasantness after stress versus rest (P=0.05). Only nonsmokers showed expected inverse relationships between sympathetic and hypothalamic–pituitary–adrenal (HPA) axis reactivity measures and sensitivity to pain. Smokers showed evidence for blunted HPA‐axis function at rest and stress. These results indicate that analgesia related to both being a smoker and stress is influenced by gender and pain modality. The reduced pain perception in smokers and absence of relationships between endogenous pain regulatory mechanisms and pain sensitivity may reflect a maladaptive response to chronic smoking.

Recommendations for Planning Pilot Studies in Clinical and Translational Research

Advances in clinical and translation science are facilitated by building on prior knowledge gained through experimentation and observation. In the context of drug development, preclinical studies are followed by a progression of phase I through phase IV clinical trials. At each step, the study design and statistical strategies are framed around research questions that are prerequisites for the next phase. In other types of biomedical research, pilot studies are used for gathering preliminary support for the next research step. However, the phrase “pilot study” is liberally applied to projects with little or no funding, characteristic of studies with poorly developed research proposals, and usually conducted with no detailed thought of the subsequent study. In this article, we present a rigorous definition of a pilot study, offer recommendations for the design, analysis and sample size justification of pilot studies in clinical and translational research, and emphasize the important role that well‐designed pilot studies play in the advancement of science and scientific careers. Clin Trans Sci 2011; Volume 4: 332–337

HIV-1 drug resistance evolution among patients on potent combination antiretroviral therapy with detectable viremia.

Many patients infected with HIV do not achieve or maintain virologic suppression below levels of detection while on potent combination antiretroviral therapy. The likelihood of emergence of incident mutations conferring reduced antiretroviral drug susceptibility was estimated among patients maintained on a stable regimen with ongoing detectable plasma HIV RNA levels. Ninety-eight HIV-infected patients were identified who had 2 genotypic antiretroviral resistance tests available. Poisson log-linear regression models were used to identify predictors and estimate incidence rates of number of acquired antiretroviral drug resistance mutations per person-year. At the 1st resistance test, 88% of patients had evidence of at least 1 mutation. Sixty percent of patients acquired at least 1 new mutation during a median of 9.3 months between consecutive resistance tests, with an incidence rate of 1.61 acquired mutations per person-year (95% CI: 1.36-1.90). Predictors of resistance evolution included average plasma HIV RNA level, HIV RNA slope, and number of mutations detected at the 1st resistance test. The likelihood of acquiring drug resistance mutations while remaining on potent combination antiretroviral therapy that does not confer complete suppression of HIV replication is relatively low and depends on the level of viral replication and prior resistance.

Elevated virus loads of Kaposi's sarcoma-associated human herpesvirus 8 predict Kaposi's sarcoma disease progression, but elevated levels of human immunodeficiency virus type 1 do not

Kaposis sarcoma-associated herpesvirus (KSHV) is found in Kaposis sarcoma (KS), multicentric Castlemans disease, and primary effusion lymphomas. To prospectively evaluate KSHV load as a biomarker for KS clinical status and prognosis in a cohort of men with AIDS-related KS, 2 quantitative polymerase chain reaction (PCR) assays were developed and tested to determine KSHV peripheral blood mononuclear cell (PBMC) virus loads. Most patients (13/15) with good-prognosis KS had < or =1.5 log KSHV copies/10(5) PBMC by both quantitative competitive (QC) and real-time Applied Biosystems (ABI) PCR. Both assays provided 94% specificity for identifying the 16 patients without KS progression during 20 months of follow-up. QC-PCR and ABI-PCR exhibited 100% and 80% levels of diagnostic sensitivity, respectively, for identifying the 5 patients whose KS progressed. Neither dichotomized human immunodeficiency virus loads nor dichotomized CD4 counts predicted either KS progression or KS clinical stage (all positive predictive values < 30%). These results are evidence that the quantity of circulating KSHV in KS patients is biologically meaningful and is measurable with sufficient accuracy to provide clinically useful information.