Trevor Peter

Neutralizing Antibodies to Adenovirus Serotype 5 Vaccine Vectors Are Directed Primarily against the Adenovirus Hexon Protein

The utility of recombinant adenovirus serotype 5 (rAd5) vector-based vaccines for HIV-1 and other pathogens will likely be limited by the high prevalence of pre-existing Ad5-specific neutralizing Abs (NAbs) in human populations. However, the immunodominant targets of Ad5-specific NAbs in humans remain poorly characterized. In this study, we assess the titers and primary determinants of Ad5-specific NAbs in individuals from both the United States and the developing world. Importantly, median Ad5-specific NAb titers were >10-fold higher in sub-Saharan Africa compared with the United States. Moreover, hexon-specific NAb titers were 4- to 10-fold higher than fiber-specific NAb titers in these cohorts by virus neutralization assays using capsid chimeric viruses. We next performed adoptive transfer studies in mice to evaluate the functional capacity of hexon- and fiber-specific NAbs to suppress the immunogenicity of a prototype rAd5-Env vaccine. Hexon-specific NAbs were remarkably efficient at suppressing Env-specific immune responses elicited by the rAd5 vaccine. In contrast, fiber-specific NAbs exerted only minimal suppressive effects on rAd5 vaccine immunogenicity. These data demonstrate that functionally significant Ad5-specific NAbs are directed primarily against the Ad5 hexon protein in both humans and mice. These studies suggest a potential strategy for engineering novel Ad5 vectors to evade dominant Ad5-specific NAbs.

A Microchip CD4 Counting Method for HIV Monitoring in Resource-Poor Settings

Background More than 35 million people in developing countries are living with HIV infection. An enormous global effort is now underway to bring antiretroviral treatment to at least 3 million of those infected. While drug prices have dropped considerably, the cost and technical complexity of laboratory tests essential for the management of HIV disease, such as CD4 cell counts, remain prohibitive. New, simple, and affordable methods for measuring CD4 cells that can be implemented in resource-scarce settings are urgently needed. Methods and Findings Here we describe the development of a prototype for a simple, rapid, and affordable method for counting CD4 lymphocytes. Microliter volumes of blood without further sample preparation are stained with fluorescent antibodies, captured on a membrane within a miniaturized flow cell and imaged through microscope optics with the type of charge-coupled device developed for digital camera technology. An associated computer algorithm converts the raw digital image into absolute CD4 counts and CD4 percentages in real time. The accuracy of this prototype system was validated through testing in the United States and Botswana, and showed close agreement with standard flow cytometry (r = 0.95) over a range of absolute CD4 counts, and the ability to discriminate clinically relevant CD4 count thresholds with high sensitivity and specificity. Conclusion Advances in the adaptation of new technologies to biomedical detection systems, such as the one described here, promise to make complex diagnostics for HIV and other infectious diseases a practical global reality.

Association between Virus-Specific T-Cell Responses and Plasma Viral Load in Human Immunodeficiency Virus Type 1 Subtype C Infection

ABSTRACT Virus-specific T-cell immune responses are important in restraint of human immunodeficiency virus type 1 (HIV-1) replication and control of disease. Plasma viral load is a key determinant of disease progression and infectiousness in HIV infection. Although HIV-1 subtype C (HIV-1C) is the predominant virus in the AIDS epidemic worldwide, the relationship between HIV-1C-specific T-cell immune responses and plasma viral load has not been elucidated. In the present study we address (i) the association between the level of plasma viral load and virus-specific immune responses to different HIV-1C proteins and their subregions and (ii) the specifics of correlation between plasma viral load and T-cell responses within the major histocompatibility complex (MHC) class I HLA supertypes. Virus-specific immune responses in the natural course of HIV-1C infection were analyzed in the gamma interferon (IFN-γ)-enzyme-linked immunospot assay by using synthetic overlapping peptides corresponding to the HIV-1C consensus sequence. For Gag p24, a correlation was seen between better T-cell responses and lower plasma viral load. For Nef, an opposite trend was observed where a higher T-cell response was more likely to be associated with a higher viral load. At the level of the HLA supertypes, a lower viral load was associated with higher T-cell responses to Gag p24 within the HLA A2, A24, B27, and B58 supertypes, in contrast to the absence of such a correlation within the HLA B44 supertype. The present study demonstrated differential correlations (or trends to correlation) in various HIV-1C proteins, suggesting (i) an important role of the HIV-1C Gag p24-specific immune responses in control of viremia and (ii) more rapid viral escape from immune responses to Nef with no restraint of plasma viral load. Correlations between the level of IFN-γ-secreting T cells and viral load within the MHC class I HLA supertypes should be considered in HIV vaccine design and efficacy trials.

Human immunodeficiency virus type 1 subtype C molecular phylogeny: consensus sequence for an AIDS vaccine design?

ABSTRACT An evolving dominance of human immunodeficiency virus type 1 subtype C (HIV-1C) in the AIDS epidemic has been associated with a high prevalence of HIV-1C infection in the southern African countries and with an expanding epidemic in India and China. Understanding the molecular phylogeny and genetic diversity of HIV-1C viruses may be important for the design and evaluation of an HIV vaccine for ultimate use in the developing world. In this study we analyzed the phylogenetic relationships (i) between 73 nonrecombinant HIV-1C near-full-length genome sequences, including 51 isolates from Botswana; (ii) between HIV-1C consensus sequences that represent different geographic subsets; and (iii) between specific isolates and consensus sequences. Based on the phylogenetic analyses of 73 near-full-length genomes, 16 “lineages” (a term that is used hereafter for discussion purposes and does not imply taxonomic standing) were identified within HIV-1C. The lineages were supported by high bootstrap values in maximum-parsimony and neighbor-joining analyses and were confirmed by the maximum-likelihood method. The nucleotide diversity between the 73 HIV-1C isolates (mean value of 8.93%; range, 2.9 to 11.7%) was significantly higher than the diversity of the samples to the consensus sequence (mean value of 4.86%; range, 3.3 to 7.2%, P < 0.0001). The translated amino acid distances to the consensus sequence were significantly lower than distances between samples within all HIV-1C proteins. The consensus sequences of HIV-1C proteins accompanied by amino acid frequencies were presented (that of Gag is presented in this work; those of Pol, Vif, Vpr, Tat, Rev, Vpu, Env, and Nef are presented elsewhere [http://www.aids.harvard.edu/lab_research/concensus_sequence.htm ]). Additionally, in the promoter region three NF-κB sites (GGGRNNYYCC) were identified within the consensus sequences of the entire set or any subset of HIV-1C isolates. This study suggests that the consensus sequence approach could overcome the high genetic diversity of HIV-1C and facilitate an AIDS vaccine design, particularly if the assumption that an HIV-1C antigen with a more extensive match to the circulating viruses is likely to be more efficacious is proven in efficacy trials.

Initial Response to Highly Active Antiretroviral Therapy in Hiv-1c-infected Adults in a Public Sector Treatment Program in Botswana

Objective:To describe the response to highly active antiretroviral treatment (HAART) in a public sector pilot antiretroviral (ARV) treatment program in Botswana. Methods:The response to HAART is described in adult HIV-infected ARV-naive patients initiating treatment from April 2001 to January 2002 at Princess Marina Hospital in Gaborone, Botswana. Patients had medical and laboratory evaluations before initiating ARV treatment and were followed longitudinally. For analysis, data were collected from charts and patient management records. Results:One hundred fifty-three ARV-naive patients initiated HAART. Most received didanosine plus stavudine (ddI + d4T) with efavirenz or nevirapine. The mean CD4+ cell count increase was 149 cells/mm3 at 24 weeks and 204 cells/mm3 at 48 weeks. The percentage of patients with an HIV-1 RNA level ≤400 copies/mL was 87.0% at 24 weeks and 78.8% at 48 weeks. The Kaplan-Meier 1-year survival estimate was 84.7% (79.0%, 90.8%), with a 3.2-fold increased risk (P = 0.004) of mortality among patients with a CD4+ cell count <50 cells/mm3. The 1-year Kaplan-Meier estimate of toxicity-related drug switches was 32.2% (20.3%, 40.4%). The most common toxicity was peripheral neuropathy, occurring more frequently in patients with a preexisting diagnosis of peripheral neuropathy and among those placed on ddI + d4T-containing regimens. Conclusions:An excellent response to HAART was observed among HIV-1C-infected patients, paralleling those seen elsewhere. Despite excellent responses, high rates of toxicity were observed for ddI + d4T-containing regimens.

Evaluation of the PIMA point-of-care CD4 analyzer in VCT clinics in Zimbabwe.

Point-of-care (POC) CD4 testing was implemented at a stand-alone HIV voluntary testing and counseling centre in Harare, Zimbabwe. To validate the use of this new technology, paired blood samples were collected from 165 patients either by a nurse or a laboratory technician and tested using POC and conventional laboratory CD4 machines. Finger prick (capillary) blood was collected directly into the PIMA POC CD4 Analyzer cartridges and tested immediately, whereas venous blood collected into evacuated tubes was used for CD4 enumeration on a Becton Dickinson FACSCalibur. There was no significant difference in mean absolute CD4 counts between the POC PIMA and Becton Dickinson FACSCalibur platforms (+7.6 cells/μL; P = 0.72). Additionally, there was no significant difference in CD4 counts between the platforms when run by either a nurse (+18.0 cells/μL; P = 0.49), or a laboratory technicians (−3.1 cells/μL; P = 0.93). This study demonstrates that POC CD4 testing can be conducted in a voluntary testing and counseling setting for staging HIV-positive clients. Both nurses and laboratory technicians performed the test accurately, thereby increasing the human resources available for POC CD4 testing. By producing same-day results, POC CD4 facilitates immediate decision-making, patient management and referral and may help improve patient care and retention. POC CD4 may also alleviate testing burdens at traditional central CD4 laboratories, hence improving test access in both rural and urban environments.

Magnitude and Frequency of Cytotoxic T-Lymphocyte Responses: Identification of Immunodominant Regions of Human Immunodeficiency Virus Type 1 Subtype C

ABSTRACT A systematic analysis of immune responses on a population level is critical for a human immunodeficiency virus type 1 (HIV-1) vaccine design. Our studies in Botswana on (i) molecular analysis of the HIV-1 subtype C (HIV-1C) epidemic, (ii) frequencies of major histocompatibility complex class I HLA types, and (iii) cytotoxic T-lymphocyte (CTL) responses in the course of natural infection allowed us to address HIV-1C-specific immune responses on a population level. We analyzed the magnitude and frequency of the gamma interferon ELISPOT-based CTL responses and translated them into normalized cumulative CTL responses. The introduction of population-based cumulative CTL responses reflected both (i) essentials of the predominant virus circulating locally in Botswana and (ii) specificities of the genetic background of the Botswana population, and it allowed the identification of immunodominant regions across the entire HIV-1C. The most robust and vigorous immune responses were found within the HIV-1C proteins Gag p24, Vpr, Tat, and Nef. In addition, moderately strong responses were scattered across Gag p24, Pol reverse transcriptase and integrase, Vif, Tat, Env gp120 and gp41, and Nef. Assuming that at least some of the immune responses are protective, these identified immunodominant regions could be utilized in designing an HIV vaccine candidate for the population of southern Africa. Targeting multiple immunodominant regions should improve the overall vaccine immunogenicity in the local population and minimize viral escape from immune recognition. Furthermore, the analysis of HIV-1C-specific immune responses on a population level represents a comprehensive systematic approach in HIV vaccine design and should be considered for other HIV-1 subtypes and/or different geographic areas.

Identification of Human Immunodeficiency Virus Type 1 Subtype C Gag-, Tat-, Rev-, and Nef-Specific Elispot-Based Cytotoxic T-Lymphocyte Responses for AIDS Vaccine Design

ABSTRACT The most severe human immunodeficiency virus type 1 (HIV-1) epidemic is occurring in southern Africa. It is caused by HIV-1 subtype C (HIV-1C). In this study we present the identification and analysis of cumulative cytotoxic T-lymphocyte (CTL) responses in the southern African country of Botswana. CTLs were shown to be an important component of the immune response to control HIV-1 infection. The definition of optimal and dominant epitopes across the HIV-1C genome that are targeted by CTL is critical for vaccine design. The characteristics of the predominant virus that causes the HIV-1 epidemic in a certain geographic area and also the genetic background of the population, through the distribution of common HLA class I alleles, might impact dominant CTL responses in the vaccinee and in the general population. The enzyme-linked immunospot (Elispot) gamma interferon assay has recently been shown to be a reliable tool to map optimal CTL epitopes, correlating well with other methods, such as intracellular staining, tetramer staining, and the classical chromium release assay. Using Elispot with overlapping synthetic peptides across Gag, Tat, Rev, and Nef, we analyzed HIV-1C-specific CTL responses of HIV-1-infected blood donors. Profiles of cumulative Elispot-based CTL responses combined with diversity and sequence consensus data provide an additional characterization of immunodominant regions across the HIV-1C genome. Results of the study suggest that the construction of a poly-epitope subtype-specific HIV-1 vaccine that includes multiple copies of immunodominant CTL epitopes across the viral genome, derived from predominant HIV-1 viruses, might be a logical approach to the design of a vaccine against AIDS.

Antiretroviral Concentrations in Breast-Feeding Infants of Women in Botswana Receiving Antiretroviral Treatment

BACKGROUND The magnitude of infant antiretroviral (ARV) exposure from breast milk is unknown. METHODS We measured concentrations of nevirapine, lamivudine, and zidovudine in serum and whole breast milk from human immunodeficiency virus type 1 (HIV-1)-infected women in Botswana receiving ARV treatment and serum from their uninfected, breast-feeding infants. RESULTS Twenty mother-infant pairs were enrolled. Maternal serum concentrations of nevirapine were high (median, 9534 ng/mL at a median of 4 h after nevirapine ingestion). Median breast-milk concentrations of nevirapine, lamivudine, and zidovudine were 0.67, 3.34, and 3.21 times, respectively, those in maternal serum. The median infant serum concentration of nevirapine was 971 ng/mL, at least 40 times the 50% inhibitory concentration and similar to peak concentrations after a single 2-mg/kg dose of nevirapine. The median infant serum concentration of lamivudine was 28 ng/mL, and the median infant serum concentration of zidovudine was 123 ng/mL, but infants were also receiving zidovudine prophylaxis. CONCLUSIONS HIV-1 inhibitory concentrations of nevirapine are achieved in breast-feeding infants of mothers receiving these ARVs, exposing infants to the potential for beneficial and adverse effects of nevirapine ingestion. Further study is needed to understand the impact of maternal ARV treatment on breast-feeding HIV-1 transmission, infant toxicity, and HIV-1 resistance mutations among infected infants.

Highly Active Antiretroviral Therapy Started during Pregnancy or Postpartum Suppresses HIV-1 RNA, but Not DNA, in Breast Milk

BACKGROUND The ability of highly active antiretroviral therapy (HAART) to reduce human immunodeficiency virus type 1 (HIV-1) RNA and DNA in breast milk has not been described. METHODS We compared breast-milk HIV-1 RNA and DNA loads of women in Botswana who received HAART (nevirapine, lamivudine, and zidovudine) and women who did not receive HAART. RESULTS Women in the HAART group received treatment for a median of 98 days (range, 67-222 days) at the time of breast-milk sampling; 23 (88%) of 26 had whole breast-milk HIV-1 RNA loads <50 copies/mL, compared with 9 (36%) of 25 women who did not receive HAART (P=.0001). This finding remained significant in a multivariate logistic-regression model (P = .0006). The whole-milk HIV-1 DNA load was unaffected by HAART. Of women who received HAART, 13 (50%) of 26 had HIV-1 DNA loads <10 copies/10(6) cells, compared with 15 (65%) of 23 who did not receive HAART (P = .39). CONCLUSIONS HAART suppressed cell-free HIV-1 RNA in breast milk and may therefore reduce mother-to-child transmission (MTCT) of HIV-1 via breast-feeding. However, HAART initiated during pregnancy or early after delivery had no apparent effect on cell-associated HIV-1 DNA loads in breast milk. Clinical trials to determine MTCT among breast-feeding women receiving HAART are needed.