H W Sheppard

California Department of Public Health, California City, California, United States

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Publications (97)833.05 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Since 1987, when we first formulated the hypothesis that AIDS and HIV disease are the result of inappropriate immune system activation triggered by viral gp 120 signalling at CD4 [1-3], the concept has been supported by several developments. First is a better understanding of the natural history of HIV disease. Second is the elucidation of the role of CD4 in T cell activation. Third is the appreciation of the prominent role of programmed cell death or apoptosis in the normal dynamic equilibrium of the immune system. Last is the failure of antiviral strategies to affect the clinical course of disease in infected individuals.
    06/2011: pages 203-210;
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    ABSTRACT: Transient HIV infections have been invoked to account for the cellular immune responses detected in highly virus-exposed individuals who have remained HIV-seronegative. We tested for very low levels of HIV RNA in 524 seronegative plasma samples from 311 highly exposed women and men from three longitudinal HIV cohorts. Two thousand and seventy-three transcription-mediated amplification (TMA) HIV RNA tests were performed for an average of 3.95 TMA assays per plasma sample. Quadruplicate TMA assays, analyzing a total of 2 ml of plasma, provided an estimated sensitivity of 3.5 HIV RNA copies/ml. Four samples from individuals who did not seroconvert within the following 6 months were positive for HIV RNA. For one sample, human polymorphism DNA analysis indicated a sample mix-up. Borderline HIV RNA detection signals were detected for the other three positive samples but further replicate TMA testing yielded no positive results. Nested PCR assays (n = 254) for HIV proviral DNA in peripheral blood mononuclear cells (PBMCs) from these three individuals were negative. Transient viremia was not reproducibly detected in highly HIV-exposed seronegative men and women. If transient infections do occur, plasma HIV RNA levels may remain below the detection limits of the sensitive assay used here, be of very short duration, or viral replication may be restricted to mucosal surfaces or their draining lymphoid tissues.
    AIDS (London, England) 02/2011; 25(5):619-23. · 4.91 Impact Factor
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    ABSTRACT: This study aimed to characterize genetic features of HIV-1 subtype C envelope glycoproteins capable of eliciting cross-reactive neutralizing antibodies during natural infections. The gp160 sequences were determined for 36 HIV-1 subtype C isolates (donor viruses) from infected individuals residing in Malawi, Zimbabwe, Zambia and South Africa, whose sera displayed a range of cross-neutralizing activities against a panel of 5 subtype C and 5 subtype B viruses (panel viruses). Hierarchical clustering analysis of neutralization data of the panel viruses predicted phylogenetic relationships between subtype B and C panel viruses, suggesting some subtype-specific neutralization determinants. A similar comparison of subtype C donor viruses showed no significant correlation; however of three donor sequence pairs resolvable by phylogenetic analysis, two were also associated within the neutralization clustering dendrogram, suggesting that closely related viruses may elicit antibodies targeting common neutralization determinants. Significantly, viruses that had shorter V1-V4 loops induced antibodies that showed more neutralization breadth against the subtype C panel viruses (p=0.0135). This study indicates that that some structural features of envelope, such as shorter variable loops, may facilitate the elicitation of cross-reactive neutralizing antibodies in natural infections. Collectively these data provide some insights into design features of an envelope immunogen aimed at inducing neutralizing antibodies.
    Virology 12/2007; 368(1):172-81. · 3.37 Impact Factor
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    ABSTRACT: Up to 40% of all mother-to-child transmission of HIV occurs by means of breast-feeding; yet, in developing countries, infant formula may not be a safe option. The World Health Organization recommends heat-treated breast milk as an infant-feeding alternative. We investigated the ability of a simple method, flash-heat, to inactivate HIV in breast milk from HIV-positive mothers. Ninety-eight breast milk samples, collected from 84 HIV-positive mothers in a periurban settlement in South Africa, were aliquoted to unheated control and flash-heating. Reverse transcriptase (RT) assays (lower detection limit of 400 HIV copies/mL) were performed to differentiate active versus inactivated cell-free HIV in unheated and flash-heated samples. We found detectable HIV in breast milk samples from 31% (26 of 84) of mothers. After adjusting for covariates, multivariate logistic regression showed a statistically significant negative association between detectable virus in breast milk and maternal CD4+ T-lymphocyte count (P=0.045) and volume of breast milk expressed (P=0.01) and a positive association with use of multivitamins (P=0.03). All flash-heated samples showed undetectable levels of cell-free HIV-1 as detected by the RT assay (P<0.00001). Flash-heat can inactivate HIV in naturally infected breast milk from HIV-positive women. Field studies are urgently needed to determine the feasibility of in-home flash-heating breast milk to improve infant health while reducing postnatal transmission of HIV in developing countries.
    JAIDS Journal of Acquired Immune Deficiency Syndromes 07/2007; 45(3):318-23. · 4.65 Impact Factor
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    ABSTRACT: Several HIV-1 subtype C-specific gag- and/or nef-based vaccines are currently intended for clinical trial in southern Africa. Here we provide sequences of 64 gag and 45 nef genes sampled in Malawi, Zambia, Zimbabwe, and South Africa and assess the degree of southern African HIV-1 diversity that will confront these vaccines. Whereas reasonable phylogenetic evidence exists for geographical clustering of subtype C gag and nef sequences from various other parts of the world, there is little evidence of similar population founder effects in the southern African epidemic. The entire breadth of subtype C diversity is represented in the southern African genes suggesting there may be no advantage in producing region- or country-specific subtype C vaccines. We do not, however, find much evidence of intersubtype recombination in the Southern African genes, implying that the likelihood of vaccine failure due to the emergence of intersubtype recombinants is probably low.
    AIDS Research and Human Retroviruses 04/2007; 23(3):477-81. · 2.71 Impact Factor
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    ABSTRACT: We examined the rates of variant population turnover of the V1-V2 and V4-V5 hypervariable domains of the human immunodeficiency virus type 1 (HIV-1) gp120 molecule in longitudinal plasma samples from 14 men with chronic HIV-1 infection using heteroduplex tracking assays (HTA). Six men had high rates of CD4+ T-cell loss, and eight men had low rates of CD4+ T-cell loss over 2.5 to 8 years of infection. We found that V1-V2 and V4-V5 env populations changed dramatically over time in all 14 subjects; the changes in these regions were significantly correlated with each another over time. The subjects with rapid CD4 loss had significantly less change in their env populations than the subjects with slow CD4 loss. The two subjects with rapid CD4 loss and sustained low CD4 counts (<150/microl for at least 2 years) showed stabilization of their V1-V2 and V4-V5 populations as reflected by low levels of total change in HTA pattern and low HTA indices (a novel measure of the emergence of new bands and band distribution); this stabilization was not observed in other subjects. The stabilization of env variant populations at low CD4 counts following periods of rapid viral evolution suggests that selective pressure on env, likely from new immune responses, is minimal when CD4 counts drop dramatically and remain low for extended periods of time.
    Journal of Virology 12/2006; 80(21):10591-9. · 5.08 Impact Factor
  • Journal of Human Lactation 09/2006; 22(3):267-8; author reply 268. · 1.64 Impact Factor
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    ABSTRACT: Using the serological testing algorithm for recent HIV seroconversion, we estimated annualized incidences (per 100 person-years) of HIV-1 infection in different at-risk groups in Buenos Aires and Montevideo, during a 5-year period between 1998 and 2003. HIV-positive serum samples from 9 serosurveys conducted among men who have sex with men, patients attending clinics for a sexually transmitted infections consult (STIs), female commercial sex workers, injecting drug users (IDUs), noninjecting cocaine users (NICUs), asymptomatic women screened for HIV infection, and patients with tuberculosis were used. HIV incidences were as follows: 6.7 for men who have sex with men, 2.0 for STIs, 1.3 for female commercial sex workers, 0.0 for Argentinean IDUs, 10.3 for Uruguayan IDUs, 3.1 for Argentinean NICUs, 4.4 for Uruguayan NICUs, and 2.4 for patients with tuberculosis. Among asymptomatic women screened for HIV infection, incidence rose from 0.4 in 1998 to 4.6 in 1999 and to a high of 10.2 in the year 2000. Unexpectedly, high HIV incidences were detected among at-risk groups in Buenos Aires and Montevideo. This pattern shows an emerging HIV epidemic among heterosexuals stemming from core HIV-infected at-risk groups. There is an urgent need for development and implementation of specific prevention strategies to address this burgeoning epidemic.
    JAIDS Journal of Acquired Immune Deficiency Syndromes 09/2006; 42(4):494-500. · 4.65 Impact Factor
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    Infectious Diseases in Obstetrics and Gynecology 02/2006; 2006:95938.
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    ABSTRACT: Heat-treated breast milk of HIV-positive mothers has potential to reduce vertical transmission. This study compared the impact of flash-heating (FH) and Pretoria pasteurization (PP) on HIV, nutrients, and antimicrobial properties in human milk. Milk samples were spiked with 1 x 10 (8) copies/mL of clade C HIV-1 and treated with FH and PP. We measured HIV reverse transcriptase (RT) activity before and after heating (n = 5). Heat impact on vitamins A, B6, B12, and C; folate, riboflavin, thiamin, and antimicrobial proteins (lactoferrin and lysozyme) was assessed. Storage safety was evaluated by spiking with Escherichia coli or Staphylococcus aureus. Both methods inactivated > or = 3 logs of HIV-1. FH resulted in undetectable RT activity. Neither method caused significant decrease in any vitamin, although reductions in vitamins C and E were noted. Heat decreased immunoreactive lactoferrin (P < 0.05) but not the proportions of lactoferrin and lysozyme surviving digestion. FH seems to retain more antibacterial activity. Both treatments eliminated spiked bacteria. FH may be superior to PP in eliminating all viral activity; both methods retained nutrients and destroyed bacterial contamination. Heat-treated breast milk merits further study as a safe and practical infant feeding option for HIV-positive mothers in developing countries.
    JAIDS Journal of Acquired Immune Deficiency Syndromes 10/2005; 40(2):175-81. · 4.65 Impact Factor
  • Haynes W Sheppard
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    ABSTRACT: Inactivated or "killed" virus (KV) is a "classical" approach that has produced safe and effective human and veterinary vaccines but has received relatively little attention in the effort to develop an HIV/AIDS vaccine. Initially, KV and rgp120 subunit vaccines were the two most obvious approaches but, unfortunately, rgp120 has not been efficacious and the KV approach has been limited by a variety of scientific, technical, and sociological factors. For example, when responses to cellular antigens, present on SIV grown in human cells, proved to be largely responsible for efficacy, the KV approach was widely discounted. Similarly, when lab-adapted HIV-1 appeared to lose envelope glycoprotein during preparation (not the case for primary isolates), this was viewed as a fundamental barrier to the KV concept. Also, a preference for "safer", genetically-engineered vaccines, and emphasis on cellular immunity, have left KV low on the priority list for funding agencies and investigators. The recent suggestion that "native" trimeric gp120 displays conserved conformational neutralization epitopes, along with the failure of rgp120, and difficulties in raising strong cellular responses with DNA or vectored vaccines, has restored some interest in the KV concept. In the past 15 years, several groups have initiated pre-clinical development of KV candidates for SIV or HIV and promising, albeit limited, information has been produced. In this chapter we discuss the rationale (including pros and cons) for producing and testing killed-HIV vaccines, the prospects for success, the nature and scope of research needed to test the KV concept, what has been learned to date, and what remains undone.
    Current Drug Targets - Infectious Disorders 07/2005; 5(2):131-41.
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    ABSTRACT: Defining viral dynamics in natural infection is prognostic of disease progression and could prove to be important for vaccine trial design as viremia may be a likely secondary end point in phase III HIV efficacy trials. There are limited data available on the early course of plasma viral load in subtype C HIV-1 infection in Africa. Plasma viral load and CD4+ T cell counts were monitored in 51 recently infected subjects for 9 months. Individuals were recruited from four southern African countries: Zambia, Malawi, Zimbabwe, and South Africa and the median estimated time from seroconversion was 8.9 months (interquartile range, 5.7-14 months). All were infected with subtype C HIV-1 and median viral loads, measured using branched DNA, ranged from 3.82-4.02 log10 RNA copies/ml from 2-24 months after seroconversion. Viral loads significantly correlated with CD4+ cell counts (r=-0.5, p<0.0001; range, 376-364 cells/mm3) and mathematical modeling defined a median set point of 4.08 log10 (12 143 RNA copies/ml), which was attained approximately 17 months after seroconversion. Comparative measurements using three different viral load platforms (bDNA, Amplicor, and NucliSens) confirmed that viremia in subtype C HIV-1-infected individuals within the first 2 years of infection did not significantly differ from that found in early subtype B infection. In conclusion, the course of plasma viremia, as described in this study, will allow a useful baseline comparator for understanding disease progression in an African setting and may be useful in the design of HIV-1 vaccine trials in southern Africa.
    AIDS Research and Human Retroviruses 05/2005; 21(4):285-91. · 2.71 Impact Factor
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    ABSTRACT: The serological testing algorithm for recent human immunodeficiency virus (HIV) seroconversion (STARHS) was employed to estimate HIV incidence among pregnant women from Sao Paulo, Brazil. A cross-sectional study (1999 to 2002) showed an incidence of infection of 0.2 per 100 pregnant women per year (95% confidence interval, 0.041 to 0.608). Western blot profiles suggested an association between results of the STARHS analysis and gp41/gp31 bands.
    Journal of Clinical Microbiology 04/2005; 43(3):1439-42. · 4.07 Impact Factor
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    ABSTRACT: Characterization of optimal CTL epitopes in Gag can provide crucial information for evaluation of candidate vaccines in populations at the epicenter of the HIV-1 epidemic. We screened 38 individuals with recent subtype C HIV-1 infection using overlapping consensus C Gag peptides and hypothesized that unique HLA-restricting alleles in the southern African population would determine novel epitope identity. Seventy-four percent of individuals recognized at least one Gag peptide pool. Ten epitopic regions were identified across p17, p24, and p2p7p1p6, and greater than two-thirds of targeted regions were directed at: TGTEELRSLYNTVATLY (p17, 35%); GPKEPFRDYVDRFFKTLRAEQATQDV (p24, 19%); and RGGKLDKWEKIRLRPGGKKHYMLKHL (p17, 15%). After alignment of these epitopic regions with consensus M and a consensus subtype C sequence from the cohort, it was evident that the regions targeted were highly conserved. Fine epitope mapping revealed that five of nine identified optimal Gag epitopes were novel: HLVWASREL, LVWASRELERF, LYNTVATLY, PFRDYVDRFF, and TLRAEQATQD, and were restricted by unique HLA-Cw*08, HLA-A*30/B*57, HLA-A*29/B*44, and HLA-Cw*03 alleles, respectively. Notably, three of the mapped epitopes were restricted by more than one HLA allele. Although these epitopes were novel and restricted by unique HLA, they overlapped or were embedded within previously described CTL epitopes from subtype B HIV-1 infection. These data emphasize the promiscuous nature of epitope binding and support our hypothesis that HLA diversity between populations can shape fine epitope identity, but may not represent a constraint for universal recognition of Gag in highly conserved domains.
    The Journal of Immunology 11/2004; 173(7):4607-17. · 5.52 Impact Factor
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    ABSTRACT: Candidate human immunodeficiency virus (HIV)-1 vaccines that elicit cytotoxic T lymphocytes may modulate HIV infection, requiring a prototype evaluation to assess participants who become infected with HIV. Of 1497 participants in canarypox HIV-1 vaccine prime-boost trials, 28 (1.9%) acquired HIV-1 infection after vaccination. Median plasma HIV-1 RNA levels (vaccinees, 4.78 log10 copies/mL; placebo recipients, 4.27 log10 copies/mL) and CD4 cell counts (vaccinees, 552 cells/mm3; placebo recipients, 657 cells/mm3) before administration of antiretroviral therapy (ART) and time to a composite end point (plasma HIV-1 RNA level >55,000 copies/mL, CD4 cell count <350 cells/mm3, or initiation of ART) did not differ significantly between vaccinees and placebo recipients (P =.4, P =.1, and P =.7, respectively). Persons who acquire HIV-1 infection while enrolled in HIV-1 vaccine trials can be successfully followed after infection, to determine whether vaccines alter the course of HIV-1 infection.
    The Journal of Infectious Diseases 09/2004; 190(5):903-7. · 5.85 Impact Factor
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    ABSTRACT: The presence of recombinant intersubtypes of HIV-1 in Argentina has been reported since the mid-1990s. In this study, sequences of a region of the gag, pol, and vpu genes of HIV-1 were analyzed in samples of 21 injection drug users (IDUs) residing in the suburbs of the city of Buenos Aires. Genomic characterization and identification of recombination sites were made comparing the 3 regions with reference isolation sequences of subtypes B, F, C, A, and B/F recombinants: CRF12_BF and non-CRF12_BF sequences. Subtype assignment of the analyzed segments was phylogenetically confirmed. All the samples turned out to be BF recombinants in at least 1 of the 3 studied genes. Twelve samples (57%) had the same pattern as the Argentinean CRF12_BF, whereas in the rest, the pattern differed in at least 1 of the 3 genes. The relation of these fragments to the CRF12_BF was phylogenetically verified. These results indicate the predominance of BF recombinants and the presence of a high percentage of sequences closely related to the CRF12_BF in the IDU population in Argentina and suggest a possible association between viral variants and the transmission route.
    JAIDS Journal of Acquired Immune Deficiency Syndromes 06/2004; 36(1):630-6. · 4.65 Impact Factor
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    ABSTRACT: An understanding of the relationship between the breadth and magnitude of T-cell epitope responses and viral loads is important for the design of effective vaccines. For this study, we screened a cohort of 46 subtype C human immunodeficiency virus type 1 (HIV-1)-infected individuals for T-cell responses against a panel of peptides corresponding to the complete subtype C genome. We used a gamma interferon ELISPOT assay to explore the hypothesis that patterns of T-cell responses across the expressed HIV-1 genome correlate with viral control. The estimated median time from seroconversion to response for the cohort was 13 months, and the order of cumulative T-cell responses against HIV proteins was as follows: Nef > Gag > Pol > Env > Vif > Rev > Vpr > Tat > Vpu. Nef was the most intensely targeted protein, with 97.5% of the epitopes being clustered within 119 amino acids, constituting almost one-third of the responses across the expressed genome. The second most targeted region was p24, comprising 17% of the responses. There was no correlation between viral load and the breadth of responses, but there was a weak positive correlation (r = 0.297; P = 0.034) between viral load and the total magnitude of responses, implying that the magnitude of T-cell recognition did not contribute to viral control. When hierarchical patterns of recognition were correlated with the viral load, preferential targeting of Gag was significantly (r = 0.445; P = 0.0025) associated with viral control. These data suggest that preferential targeting of Gag epitopes, rather than the breadth or magnitude of the response across the genome, may be an important marker of immune efficacy. These data have significance for the design of vaccines and for interpretation of vaccine-induced responses.
    Journal of Virology 04/2004; 78(7):3233-43. · 5.08 Impact Factor
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    ABSTRACT: HIV-1 infection in India has been increasing steadily over the last decade. In the absence of potent antiviral therapy, estimates of HIV infection are needed to monitor the epidemic, institute prevention strategies in target populations and determine the suitable populations for vaccine studies. In this report we present the HIV-1 seroprevalence and annual estimates of seroincidence in a high risk population from Calcutta, the most populous city in the eastern part of India. In 1206 high risk subjects tested over two years between February of 1999 and December 2000, we have determined an overall seroprevalence of 40.1% using enzyme-linked immunosorbent assay followed by a confirmatory Western blot testing. Furthermore, using a newly described Standardized Testing Algorithm for Recent HIV-1 Seroconversion (STARHS), we have estimated an annual seroincidence rate of about 7% in this population during this two-year study. Such a high annual seroincidence rate makes this population well suited for studies of HIV-1 prevention, including vaccine trials.
    International Journal of STD & AIDS 08/2003; 14(7):463-8. · 1.00 Impact Factor
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    ABSTRACT: In the first preventative human immunodeficiency virus (HIV) vaccine study to be carried out in Africa, 40 HIV-seronegative Ugandan volunteers were randomly assigned to receive a canarypox vector containing HIV-1 clade B (env and gag-pro) antigens (ALVAC-HIV; n = 20), control vector containing the rabies virus glycoprotein G gene (n = 10), or saline placebo (n = 10). Cytotoxic T lymphocyte activity against target cells expressing clade A, B, and D antigens was assessed using standard chromium-release and confirmatory interferon-gamma enzyme-linked immunospot (ELISPOT) assays. Neutralizing antibody responses to cell line-adapted strains and primary isolates in all 3 clades were also tested. Twenty percent of vaccine recipients generated detectable cytolytic responses to either Gag or Env, and 45% had vaccine-induced HIV-specific CD8(+) T cell responses, as measured by the ELISPOT assay. In contrast, only 5% of the control group had vaccine-specific responses. Neutralizing antibodies against primary and laboratory-adapted HIV-1 clade B strains were seen in 10% and 15% of vaccine recipients, respectively, but responses against clades A and D were not detected. Although the immunogenicity of this clade B-based vaccine was low, ALVAC-HIV elicited CD8(+) T cell responses with detectable cross-activity against clade A and D antigens in a significant proportion of vaccine recipients.
    The Journal of Infectious Diseases 04/2003; 187(6):887-95. · 5.85 Impact Factor
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    ABSTRACT: To examine temporal variation in the effects of CCR5-Delta32 and CCR2-64I chemokine receptor gene polymorphisms on HIV-1 disease progression. Pooled analysis of individual patient data from 10 cohorts of HIV-1 seroconverters from the United States, Europe, and Australia. We studied HIV-1 seroconverters of European (n = 1635) or African (n = 215) ancestry who had been genotyped for CCR5-Delta32 and CCR2-64I. We used Cox proportional hazards models with time-varying coefficients to determine whether the genetic protection against AIDS (1987 case definition) and death varied with time since seroconversion. Protection against AIDS conferred by CCR5-Delta32 held constant at a 31% (RH 0.69, 95% CI 0.54, 0.88) reduction in risk over the course of HIV-1 infection, whereas protection against death held constant at a 39% reduction in risk (RH 0.61, 95% CI 0.45, 0.88). When the period from AIDS to death was isolated, the survival benefit of CCR5-Delta32 diminished 2 years after AIDS. Protection against AIDS conferred by CCR2-64I was greatest early in the disease course. Compared with individuals without CCR5-Delta32 or CCR2-64I, individuals with one or two copies of CCR2-64I had a 58% lower risk of AIDS during the first 4 years after seroconversion (RH 0.42, 95% CI 0.23, 0.76), a 19% lower risk during the subsequent 4 years (RH 0.81, 95% CI 0.59, 1.12), and no significant protection thereafter. The protection against AIDS provided by CCR5-Delta32 is continuous during the course of infection. In contrast, the protection provided by CCR2-64I is greatest early in the course of infection.
    AIDS 03/2003; 17(3):377-87. · 6.41 Impact Factor

Publication Stats

4k Citations
833.05 Total Impact Points

Institutions

  • 2011
    • California Department of Public Health
      California City, California, United States
  • 2005
    • National Institute for Communicable Diseases
      Johannesburg, Gauteng, South Africa
  • 2002–2005
    • State of California
      California City, California, United States
  • 2001
    • University of Washington Seattle
      Seattle, Washington, United States
  • 1998
    • Smith-Kettlewell Eye Research Institute
      San Francisco, California, United States
    • Fred Hutchinson Cancer Research Center
      Seattle, Washington, United States
  • 1997
    • The Rockefeller University
      New York City, New York, United States
  • 1995–1997
    • Walter Reed Army Institute of Research
      Silver Spring, Maryland, United States
  • 1996
    • California Department of Health Care Services
      Sacramento, California, United States
    • Harvard University
      • Department of Epidemiology
      Boston, MA, United States
  • 1994–1995
    • Stanford University
      • Department of Microbiology and Immunology
      Palo Alto, CA, United States