Safety and immunogenicity of a purified inactivated Zika virus vaccine candidate in adults primed with a Japanese encephalitis virus or yellow fever virus vaccine in the USA: a phase 1, randomised, double-blind, placebo-controlled clinical trial

BACKGROUND

Zika virus infection is a threat to at-risk populations, causing major birth defects and serious neurological complications. Development of a safe and efficacious Zika virus vaccine is, therefore, a global health priority. Assessment of heterologous flavivirus vaccination is important given co-circulation of Japanese encephalitis virus and yellow fever virus with Zika virus. We investigated the effect of priming flavivirus naive participants with a licensed flavivirus vaccine on the safety and immunogenicity of a purified inactivated Zika vaccine (ZPIV).

METHODS

This phase 1, placebo-controlled, double-blind trial was done at the Walter Reed Army Institute of Research Clinical Trials Center in Silver Spring, MD, USA. Eligible participants were healthy adults aged 18-49 years, with no detectable evidence of previous flavivirus exposure (by infection or vaccination), as measured by a microneutralisation assay. Individuals with serological evidence of HIV, hepatitis B, or hepatitis C infection were excluded, as were pregnant or breastfeeding women. Participants were recruited sequentially into one of three groups (1:1:1) to receive no primer, two doses of intramuscular Japanese encephalitis virus vaccine (IXIARO), or a single dose of subcutaneous yellow fever virus vaccine (YF-VAX). Within each group, participants were randomly assigned (4:1) to receive intramuscular ZPIV or placebo. Priming vaccinations were given 72-96 days before ZPIV. ZPIV was administered either two or three times, at days 0, 28, and 196-234. The primary outcome was occurrence of solicited systemic and local adverse events along with serious adverse events and adverse events of special interest. These data were analysed in all participants receiving at least one dose of ZPIV or placebo. Secondary outcomes included measurement of neutralizing antibody responses following ZPIV vaccination in all volunteers with available post-vaccination data. This trial is registered at ClinicalTrials.gov, NCT02963909.

FINDINGS

Between Nov 7, 2016, and Oct 30, 2018, 134 participants were assessed for eligibility. 21 did not meet inclusion criteria, 29 met exclusion criteria, and ten declined to participate. 75 participants were recruited and randomly assigned. 35 (47%) of 75 participants were male and 40 (53%) were female. 25 (33%) of 75 participants identified as Black or African American and 42 (56%) identified as White. These proportions and other baseline characteristics were similar between groups. There were no statistically significant differences in age, gender, race, or BMI between those who did and did not opt into the third dose. All participants received the planned priming IXIARO and YF-VAX vaccinations, but one participant who received YF-VAX dropped out before receipt of the first dose of ZPIV. 50 participants received a third dose of ZPIV or placebo, including 14 flavivirus-naive people, 17 people primed with Japanese encephalitis virus vaccine, and 19 participants primed with yellow fever vaccine. Vaccinations were well tolerated across groups. Pain at the injection site was the only adverse event reported more frequently in participants who received ZPIV than in those who received placebo (39 [65%] of 60 participants, 95% CI 51·6-76·9 who received ZPIV vs three [21·4%] of 14 who received placebo; 4·7-50·8; p=0·006). No patients had an adverse event of special interest or serious adverse event related to study treatment. At day 57, the flavivirus-naive volunteers had an 88% (63·6-98·5, 15 of 17) seroconversion rate (neutralising antibody titre ≥1:10) and geometric mean neutralising antibody titre (GMT) against Zika virus of 100·8 (39·7-255·7). In the Japanese encephalitis vaccine-primed group, the day 57 seroconversion rate was 31·6% (95% CI 12·6-56·6, six of 19) and GMT was 11·8 (6·1-22·8). Participants primed with YF-VAX had a seroconversion rate of 25% (95% CI 8·7-49·1, five of 20) and GMT of 6·6 (5·2-8·4). Humoral immune responses rose substantially following a third dose of ZPIV, with seroconversion rates of 100% (69·2-100; ten of ten), 92·9% (66·1-99·8; 13 of 14), and 60% (32·2-83·7, nine of 15) and GMTs of 511·5 (177·6-1473·6), 174·2 (51·6-587·6), and 79 (19·0-326·8) in the flavivirus naive, Japanese encephalitis vaccine-primed, and yellow fever vaccine-primed groups, respectively.

INTERPRETATION

We found ZPIV to be well tolerated in flavivirus naive and primed adults but that immunogenicity varied significantly according to antecedent flavivirus vaccination status. Immune bias towards the flavivirus antigen of initial exposure and the timing of vaccination may have impacted responses. A third ZPIV dose overcame much, but not all, of the discrepancy in immunogenicity. The results of this phase 1 clinical trial have implications for further evaluation of ZPIV's immunisation schedule and use of concomitant vaccinations.

FUNDING

Department of Defense, Defense Health Agency; National Institute of Allergy and Infectious Diseases; and Division of Microbiology and Infectious Disease.

Early sexual debut is associated with drug use and decreased educational attainment among males and females in Kisumu County, Kenya

Differing global sociocultural contexts of sexual relationships influence age at first sexual intercourse with potentially long-lasting region-specific effects such as increased risk of contracting HIV and other sexually transmitted infections (STIs). In these cross-sectional analyses of data from the screening and enrollment visits for an HIV incidence study in Kisumu County, Kenya, we evaluated factors associated with having experienced an early sexual debut (ESD) among males and females aged 18-35 years. Clinical evaluation was performed and sexual behaviors were assessed via questionnaire. ESD was defined as self-reported age 15 years or younger at first sexual intercourse. Robust Poisson regression was used to estimate prevalence ratios (PRs) and 95% confidence intervals (95% CIs) for factors associated with ESD. Of 1057 participants, 542 (51.3%) were female. Participants' median age at study screening was 25 years (interquartile range [IQR]: 22-29), and at sexual debut was 16 years (IQR: 14-17). Five hundred and four participants (47.7%) reported ESD. ESD was less common among females (PR 0.78, CI 0.67-0.90) and participants with more than primary education (PR 0.56, CI 0.47-0.66). ESD was more common in participants with a history of drug use (PR 1.28, CI 1.10-1.49). Drug use removed the protective effect of education (some secondary education or less, no drug use: PR 0.72, CI 0.61-0.85; some secondary education or less, drug use: PR 0.94, CI 0.74-1.18). ESD was common in our study and associated with lower educational attainment and increased likelihood of drug use. Interventions are needed early in life, well before 15 years of age, to encourage engagement in schooling and prevent drug use. Comprehensive sexual education and interventions to prevent drug use may be beneficial before the age of 15 years.

Longitudinal and Cross-sectional Analyses of Asymptomatic HIV-1/Malaria Co-infection in Kisumu County, Kenya

Individuals infected with HIV-1 experience more frequent and more severe episodes of malaria and are likely to harbor asymptomatic parasitemia, thus potentially making them more efficient reservoirs of malaria. Two studies (cross-sectional and longitudinal) were designed in sequence between 2015-2018 and 2018-2020, respectively, to test the hypothesis that HIV-1 infected individuals have higher prevalence of asymptomatic parasitemia and gametocytemia than the HIV-1 negatives. This article describes the overall design of the two studies, encompassing data for the longitudinal study and additional data to the previously published baseline data for the cross-sectional study. In the cross-sectional study, HIV-1 positive participants were significantly older, more likely to be male, and more likely to have parasitemia relative to HIV-1 negatives (P < 0.01). In the longitudinal study, 300 participants were followed for 6 months. Of these, 102 were HIV-1 negative, 106 were newly diagnosed HIV-1 positive, and 92 were HIV-1 positive and on antiretroviral therapy, including antifolates, at enrollment. Overall parasitemia positivity at enrollment was 17.3% (52/300). Of these, 44% (23/52) were HIV-1 negative, 52% (27/52) were newly diagnosed HIV-1 positives, and only 4% (2/52) were HIV-1 positive and on treatment. Parasitemia for those on stable antiretroviral therapy was significantly lower (hazard ratio: 0.51, P < 0.001), compared with the HIV-1-negatives. On follow-up, there was a significant decline in parasitemia prevalence (hazard ratio: 0.74, P < 0.001) among the HIV patients newly initiated on antiretroviral therapy including trimethoprim-sulfamethoxasole. These data highlight the impact of HIV-1 and HIV treatment on asymptomatic parasitemia over time.

Initiation of anti-retroviral/Trimethoprim-Sulfamethoxazole therapy in a longitudinal cohort of HIV-1 positive individuals in Western Kenya rapidly decreases asymptomatic malarial parasitemia

Interactions between malaria and HIV-1 have important public health implications. Our previous cross-sectional studies showed significant associations between HIV-1 positivity and malarial parasitemia with an increased risk of gametocytemia. In this follow-up longitudinal study, we evaluated these associations to determine the magnitude of asymptomatic parasitemia over time, and to examine the effects of initiating Antiretroviral Therapy (ART) together with the broad-spectrum antibiotic Trimethoprim Sulfamethoxazole (TS) on asymptomatic parasitemia. 300 adult volunteers in a malaria holoendemic region in Western Kenya were enrolled and followed for six months. The study groups were composed of 102 HIV-1 negatives, 106 newly diagnosed HIV-1 positives and 92 HIV-1 positives who were already stable on ART/TS. Blood samples were collected monthly and asymptomatic malarial parasitemia determined using sensitive 18S qPCR. Results showed significantly higher malaria prevalence in the HIV-1 negative group (61.4%) (p=0.0001) compared to HIV-1 positives newly diagnosed (36.5%) and those stable on treatment (31.45%). Further, treatment with ART/TS had an impact on incidence of asymptomatic parasitemia. In volunteers who were malaria PCR-negative at enrollment, the median time to detectable asymptomatic infection was shorter for HIV-1 negatives (149 days) compared to the HIV-1 positives on treatment (171 days) (p=0.00136). Initiation of HIV treatment among the newly diagnosed led to a reduction in malarial parasitemia (expressed as 18S copy numbers/μl) by over 85.8% within one week of treatment and a further reduction by 96% after 2 weeks. We observed that while the impact of ART/TS on parasitemia was long term, treatment with antimalarial Artemether/Lumefantrine (AL) among the malaria RDT positives had a transient effect with individuals getting re-infected after short periods. As was expected, HIV-1 negative individuals had normal CD4+ levels throughout the study. However, CD4+ levels among HIV-1 positives who started treatment were low at enrollment but increased significantly within the first month of treatment. From our association analysis, the decline in parasitemia among the HIV-1 positives on treatment was attributed to TS treatment and not increased CD4+ levels per se. Overall, this study highlights important interactions between HIV-1 and malaria that may inform future use of TS among HIV-infected patients in malaria endemic regions.

Brief Report: Increased Inflammation and Liver Disease in HIV/HBV-Coinfected Individuals

OBJECTIVE

HIV and hepatitis B virus (HBV) coinfection can accelerate morbidity and mortality, especially in sub-Saharan Africa where both infections are common. Although inflammation contributes to disease progression, more information is needed to better understand the pathology. This study compared markers of cirrhosis and inflammation in HIV/HBV-coinfected individuals compared with monoinfected and uninfected patients.

SETTING

The HIV/HBV-coinfected subjects from the Ugandan arm of the prospective African Cohort Study were selected for evaluation and matched by age and gender with HIV-monoinfected, HBV-monoinfected, and uninfected controls.

METHODS

Plasma samples were used to quantify markers of immune activation and inflammation. The FIB-4 (a simple index to predict significant liver fibrosis) score was used to estimate liver fibrosis. Demographic and laboratory characteristics were compared across the groups.

RESULTS

Together, 31 HIV/HBV-coinfected participants were identified and compared with 62 HIV-monoinfected, 7 HBV-monoinfected, and 62 uninfected controls. The HIV/HBV-coinfected group had generally higher levels of inflammation. Most notably, matrix metalloproteinase-2, matrix metalloproteinase-9, and fibroblast growth factor-19 levels were dysregulated among the HIV/HBV-coinfected individuals. Furthermore, the FIB-4 score was higher in the HIV/HBV-coinfected group compared with the HIV-monoinfected group and revealed that 11% of HIV/HBV-coinfected individuals had evidence of undiagnosed advanced liver disease.

CONCLUSIONS

Differences in levels of inflammation exist between individuals with HIV/HBV coinfection compared with monoinfected and uninfected controls. A distinct signature of inflammation was associated with HIV/HBV coinfection that could reflect the mechanism of liver fibrosis and increased risk for disease progression. Finally, there may be an underappreciated amount of undiagnosed advanced liver disease in sub-Saharan Africa.

Clinical laboratory reference values in adults in Kisumu County, Western Kenya; hematology, chemistry and CD4

Background

Clinical laboratory reference intervals (RIs) are essential for diagnosing and managing patients in routine clinical care as well as establishing eligibility criteria and defining adverse events in clinical trials, but may vary by age, gender, genetics, nutrition and geographic location. It is, therefore, critical to establish region-specific reference values in order to inform clinical decision-making.

Methods

We analyzed data from a prospective observational HIV incidence cohort study in Kombewa, Kenya. Study participants were healthy males and females, aged 18–35 years, without HIV. Median and 95% reference values (2.5^th percentile to 97.5^th percentile) were calculated for laboratory parameters including hematology, chemistry studies, and CD4 T cell count. Standard Deviation Ratios (SDR) and Bias Ratios (BR) are presented as measures of effect magnitude. Findings were compared with those from the United States and other Kenyan studies.

Results

A total of 299 participants were analyzed with a median age of 24 years (interquartile range: 21–28). Ratio of males to females was 0.9:1. Hemoglobin range (2.5^th—97.5^th percentiles) was 12.0–17.9 g/dL and 9.5–15.3 g/dL in men and women respectively. In the cohort, MCV range was 59-95fL, WBC 3.7–9.2×10³/μL, and platelet 154–401×10³/μL. Chemistry values were higher in males; the creatinine RI was 59–103 μmol/L in males vs. 46–76 μmol/L in females (BRUL>.3); and the alanine transferase range was 8.8–45.3 U/L in males vs. 7.5–36.8 U/L in females (SDR>.3). The overall CD4 T cell count RI was 491–1381 cells/μL. Some parameters including hemoglobin, neutrophil, creatinine and ALT varied with that from prior studies in Kenya and the US.

Conclusion

This study not only provides clinical reference intervals for a population in Kisumu County but also highlights the variations in comparable settings, accentuating the requirement for region-specific reference values to improve patient care, scientific validity, and quality of clinical trials in Africa.

Asymptomatic Visceral Leishmania infantum Infection in US Soldiers Deployed to Iraq

BACKGROUND

Visceral leishmaniasis (VL), due to Leishmania infantum, is a persistent intracellular parasitic infection transmitted by the bite of infected sand flies. Symptomatic VL has been reported in U.S. soldiers with Iraq deployment. Untreated symptomatic VL can be fatal; asymptomatic VL (AVL) may establish a lifelong risk of reactivation. We report prevalence and AVL risk factors in Operation Iraqi Freedom (OIF) deployers during 2002-11.

METHODS

Healthy soldiers exposed to VL endemic areas in Iraq and 50 controls who never traveled to endemic regions were recruited through military healthcare facilities (2015-17). Responses to a risk factor survey and blood samples were obtained. Leishmania research diagnostics utilized included enzyme-linked immunosorbent assay (ELISA), rk39 test strips, quantitative polymerase chain reaction (PCR), and interferon gamma release (IGRA) assays. Statistical analyses included Fisher exact test, Pearson χ2 test, Mann-Whitney U test, and logistic regression.

RESULTS

200 deployed subjects were enrolled, mostly males (84.0%), of white ethnicity (79.0%), and median age 41 (range 24-61) years. 64% were seropositive for Phlebotomus alexandri saliva antibodies. Prevalence of AVL (any positive test result) was 39/200 (19.5%, 95% confidence interval 14.4%-25.8%). Two (1.0%) PCR, 10 (5%) ELISA, and 28 (14%) IGRA samples were positive. Travel to Ninewa governorate increased risk for AVL (P = .01).

CONCLUSION

AVL was identified in 19.5% of OIF deployers; travel to northwest Iraq correlated with infection. Further studies are needed to inform risk for reactivation VL in US veterans and to target additional blood safety and surveillance measures.

Ciguatera fish poisoning in Hawai'i and the Pacific

Ciguatera fish poisoning (CFP) is a foodborne illness caused by fish containing ciguatoxin (CTX). The toxin is produced by the microalgae Gambierdiscus spp. which are then eaten by reef fish; humans contract the illness when eating either fish that have eaten the algae, or carnivorous fish that have eaten those fish. CTX is an odorless, tasteless, and colorless neurotoxin that blocks voltage-sensitive Na(+) channels and accumulates in many tissues of the fish, especially the viscera. The illness is typically mild to moderate in severity with gastrointestinal (diarrhea, cramping, nausea, vomiting) and neurological (paraesthesias, cold allodynia, fatigue, pruritis) manifestations. Rarely, the disease can be more severe with significant neuropathic or cardiac effects such as bradycardia and hypotension. Endemic to Hawai'i and islands throughout the Caribbean and Pacific, CFP incidence rates range from several to thousands of cases per 100,000 per year. Since fishing is important for local food supply, exportation, and recreation throughout the Pacific, CFP is medically and economically significant in these areas. We present a case of CFP from Hawai'i to illustrate the disease, demonstrating that the diagnosis is primarily clinical, with confirmatory tests from fish samples available in some cases. Treatment is supportive and symptomatic with no disease specific remedy. The prognosis for most cases is good with a short duration of self-limited symptoms, but for some cases neurological sequelae can become chronic. With no effective treatment, education on which species of reef fish and which body parts to avoid eating is essential in the prevention of CFP.