Roger Hewson

Specificity, cross-reactivity and function of antibodies elicited by Zika virus infection

Characterizing the Zika virus antibody response Given the public health emergency that Zika virus poses, scientists are seeking to understand the Zika-specific immune response. Stettler et al. analyzed 119 monoclonal antibodies isolated from four donors that were infected with Zika virus during the present epidemic, including two individuals that had previously been infected with dengue virus, another member of the flavivirus family. Neutralizing antibodies primarily recognized the envelope protein domain III (EDIII) or quaternary epitopes on the intact virus, and an EDIII-targeted antibody protected mice against lethal infection. Some EDI/II-targeting antibodies cross-reacted with dengue virus in vitro and could enhance disease in dengue-infected mice. Whether dengue and Zika virus antibodies cross-react in humans remains to be tested. Science, this issue p. 823 Cross-reactive antibody responses may pose a risk for disease on secondary infections with Dengue and/or Zika viruses. Zika virus (ZIKV), a mosquito-borne flavivirus with homology to Dengue virus (DENV), has become a public health emergency. By characterizing memory lymphocytes from ZIKV-infected patients, we dissected ZIKV-specific and DENV–cross-reactive immune responses. Antibodies to nonstructural protein 1 (NS1) were largely ZIKV-specific and were used to develop a serological diagnostic tool. In contrast, antibodies against E protein domain I/II (EDI/II) were cross-reactive and, although poorly neutralizing, potently enhanced ZIKV and DENV infection in vitro and lethally enhanced DENV disease in mice. Memory T cells against NS1 or E proteins were poorly cross-reactive, even in donors preexposed to DENV. The most potent neutralizing antibodies were ZIKV-specific and targeted EDIII or quaternary epitopes on infectious virus. An EDIII-specific antibody protected mice from lethal ZIKV infection, illustrating the potential for antibody-based therapy.

Taxonomy of the order Mononegavirales: update 2016

In 2016, the order Mononegavirales was emended through the addition of two new families (Mymonaviridae and Sunviridae), the elevation of the paramyxoviral subfamily Pneumovirinae to family status (Pneumoviridae), the addition of five free-floating genera (Anphevirus, Arlivirus, Chengtivirus, Crustavirus, and Wastrivirus), and several other changes at the genus and species levels. This article presents the updated taxonomy of the order Mononegavirales as now accepted by the International Committee on Taxonomy of Viruses (ICTV).

A Susceptible Mouse Model for Zika Virus Infection

Zika virus (ZIKV) is a mosquito-borne pathogen which has recently spread beyond Africa and into Pacific and South American regions. Despite first being detected in 1947, very little information is known about the virus, and its spread has been associated with increases in Guillain-Barre syndrome and microcephaly. There are currently no known vaccines or antivirals against ZIKV infection. Progress in assessing interventions will require the development of animal models to test efficacies; however, there are only limited reports on in vivo studies. The only susceptible murine models have involved intracerebral inoculations or juvenile animals, which do not replicate natural infection. Our report has studied the effect of ZIKV infection in type-I interferon receptor deficient (A129) mice and the parent strain (129Sv/Ev) after subcutaneous challenge in the lower leg to mimic a mosquito bite. A129 mice developed severe symptoms with widespread viral RNA detection in the blood, brain, spleen, liver and ovaries. Histological changes were also striking in these animals. 129Sv/Ev mice developed no clinical symptoms or histological changes, despite viral RNA being detectable in the blood, spleen and ovaries, albeit at lower levels than those seen in A129 mice. Our results identify A129 mice as being highly susceptible to ZIKV and thus A129 mice represent a suitable, and urgently required, small animal model for the testing of vaccines and antivirals.

Human Immunodeficiency Virus Type 1 Assembly and Lipid Rafts: Pr55gag Associates with Membrane Domains That Are Largely Resistant to Brij98 but Sensitive to Triton X-100

ABSTRACT The assembly and budding of human immunodeficiency virus type 1 (HIV-1) at the plasma membrane are directed by the viral core protein Pr55 gag . We have analyzed whether Pr55 gag has intrinsic affinity for sphingolipid- and cholesterol-enriched raft microdomains at the plasma membrane. Pr55 gag has previously been reported to associate with Triton X-100-resistant rafts, since both intracellular membranes and virus-like Pr55 gag particles (VLPs) yield buoyant Pr55 gag complexes upon Triton X-100 extraction at cold temperatures, a phenotype that is usually considered to indicate association of a protein with rafts. However, we show here that the buoyant density of Triton X-100-treated Pr55gag complexes cannot be taken as a proof for raft association of Pr55 gag , since lipid analyses of Triton X-100-treated VLPs demonstrated that the detergent readily solubilizes the bulk of membrane lipids from Pr55 gag . However, Pr55 gag might nevertheless be a raft-associated protein, since confocal fluorescence microscopy indicated that coalescence of GM1-positive rafts at the cell surface led to copatching of membrane-bound Pr55 gag . Furthermore, extraction of intracellular membranes or VLPs with Brij98 yielded buoyant Pr55 gag complexes of low density. Lipid analyses of Brij98-treated VLPs suggested that a large fraction of the envelope cholesterol and phospholipids was resistant to Brij98. Collectively, these results suggest that Pr55 gag localizes to membrane microdomains that are largely resistant to Brij98 but sensitive to Triton X-100, and these membrane domains provide the platform for assembly and budding of Pr55 gag VLPs.

Virus Detection and Monitoring of Viral Load in Crimean-Congo Hemorrhagic Fever Virus Patients

We developed a real-time reverse transcription–-PCR that detected 1,164 copies/mL of Crimean-Congo hemorrhagic fever virus per milliliter of serum at 95% probability (probit analysis) and was 100% concordant with nested PCR on 63 samples from 31 patients with confirmed infection. Infected patients who died appeared to have higher viral loads; low viral loads correlated with IgG detection.

Crimean-Congo hemorrhagic fever in Iran and neighboring countries

Crimean-Congo hemorrhagic fever (CCHF) is a zoonotic viral disease that is asymptomatic in infected livestock, but a serious threat to humans. Human infections begin with nonspecific febrile symptoms, but progress to a serious hemorrhagic syndrome with a case fatality rate of 2-50%. Although the causative virus is often transmitted by ticks, livestock-to-human and human-to-human transmissions also occur. The disease is one of the most widely distributed viral hemorrhagic fevers occurring in Africa, the Middle East, Asia, and some parts of Europe. In this study, we have focused on the CCHF situation in Iran and neighboring countries and provide evidence of over 5000 confirmed cases of CCHF in a single period/season.

Dengue virus serotype 3, Karachi, Pakistan.

1. Allander T, Tammi MT, Eriksson M, Bjerkner A, Tiveljung-Lindell A, Andersson B. Cloning of a human parvovirus by molecular screening of respiratory tract samples. Proc Natl Acad Sci U S A. 2005;102:12891–6. 2. Sloots TP, McErlean P, Speicher DJ, Arden KE, Nissen MD, Mackay IM. Evidence of human coronavirus HKU1 and human bocavirus in Australian children. J Clin Virol. 2006;35:99–102. 3. Ma X, Endo R, Ishiguro N, Ebihara T, Ishiko H, Ariga T, et al. Detection of human bocavirus in Japanese children with lower respiratory tract infections. J Clin Microbiol. 2006;44:1132–4. 4. Bastien N, Brandt K, Dust K, Ward D, Li Y. Human bocavirus infection, Canada. Emerg Infect Dis. 2006;12:848–50. 5. Foulongne V, Rodiere M, Segondy M. Human bocavirus in children. Emerg Infect Dis. 2006;12:862–3. 6. Arnold JC, Singh KK, Spector SA, Sawyer MH. Human bocavirus: prevalence and clinical spectrum at a children’s hospital. Clin Infect Dis. 2006;43:283–8. 7. Weissbrich B, Neske F, Schubert J, Tollmann F, Blath K, Blessing K, et al. Frequent detection of bocavirus DNA in German children with respiratory tract infections. BMC Infect Dis. 2006;6:109. 8. Chung JY, Han TH, Kim CK, Kim SW. Bocavirus infection in hospitalized children, South Korea. Emerg Infect Dis. 2006;12:1254–6. 9. Choi EH, Lee HJ, Kim SJ, Eun BW, Kim NH, Lee JA, et al. The association of newly identified respiratory viruses with lower respiratory tract infections in Korean children, 2000–2005. Clin Infect Dis. 2006;43:585–92.

Chikungunya Virus and Central Nervous System Infections in Children, India

Chikungunya virus (CHIKV) is a mosquito-borne alphavirus best known for causing fever, rash, arthralgia, and occasional neurologic disease. By using real-time reverse transcription–PCR, we detected CHIKV in plasma samples of 8 (14%) of 58 children with suspected central nervous system infection in Bellary, India. CHIKV was also detected in the cerebrospinal fluid of 3 children.

Integrating genome-based informatics to modernize global disease monitoring, information sharing, and response.

The rapid advancement of genome technologies holds great promise for improving the quality and speed of clinical and public health laboratory investigations and for decreasing their cost. The latest generation of genome DNA sequencers can provide highly detailed and robust information on disease-causing microbes, and in the near future these technologies will be suitable for routine use in national, regional, and global public health laboratories. With additional improvements in instrumentation, these next- or third-generation sequencers are likely to replace conventional culture-based and molecular typing methods to provide point-of-care clinical diagnosis and other essential information for quicker and better treatment of patients. Provided there is free-sharing of information by all clinical and public health laboratories, these genomic tools could spawn a global system of linked databases of pathogen genomes that would ensure more efficient detection, prevention, and control of endemic, emerging, and other infectious disease outbreaks worldwide.

Development of a real-time RT-PCR assay for the detection of Crimean-Congo hemorrhagic fever virus.

Crimean-Congo hemorrhagic fever (CCHF) is a virulent tick-borne disease with a case fatality rate ranging from 10-50% for tick-borne transmission, and up to 80% for nosocomial transmission. Human cases have been reported in over 30 countries across Europe, Asia, and Africa. It appears to be spreading to new areas with several countries reporting their first human cases of CCHF disease within the past 10 years. We report a novel real-time RT-PCR assay designed to amplify a conserved region of the CCHF virus S segment. It is capable of detecting strains from all 7 groups of CCHF, including the AP92 strain that until recently represented a lineage of strains that were not associated with human disease. The limit of detection of the assay is 5 copies of target RNA, and the assay shows no cross-reactivity with other viruses from within the same genus, or with viruses causing similar human disease.