Humoral and cellular immune responses to Lassa fever virus in Lassa fever survivors and their exposed contacts in Southern Nigeria

Burden of Lassa fever disease in pregnant women and children and options for prevention

Lassa fever is a serious epidemic viral disease in West Africa affecting an estimated 2 million people annually with about 5000-10,000 deaths, although supporting data is sparse. Lassa fever significantly affects neonates, children, and pregnant women, however, comprehensive data on its impact in these populations are lacking. We reviewed the available literature on Lassa fever to assess its prevalence and impact in these populations and implications for vaccine development. Clinical features in children were similar to those observed in adults, with complications such as bleeding. Altered mental status, anasarca (swollen baby syndrome), bleeding, and poor urine output were risk factors for death. The case fatality rate (CFR) in 16 paediatric studies ranged from 6 % to 63 % and was 66.7 % and 75.0 % in two neonatal studies. In a systematic review of studies on pregnant women the CFR was 33.73 %. The adverse foetal outcomes included miscarriage, stillbirth, and intrauterine death associated with maternal death. Since Lassa fever significantly affects neonates, children, and pregnant women, developing a safe and effective, single-dose vaccine for these high-risk populations is vital. Currently, there are four clinical trials assessing Lassa virus vaccines. Only one of these trials is enrolling children aged ≥18 months, and exclude pregnant and breast-feeding women. It is essential that pregnant and breast-feeding women and young children are included in clinical trials that incorporate robust safety surveillance and risk mitigation measures. In our review, potential approaches to address the specific gaps in the areas of diagnosis, management, and prevention of Lassa fever in these specific populations, such as disease surveillance systems and vaccine development, were identified. A comprehensive strategy with investment focused on addressing specific knowledge gaps will be essential in protecting the health of these specific populations in Lassa virus endemic regions.

A Longitudinal Analysis of Memory Immune Responses in Convalescent Crimean-Congo Hemorrhagic Fever Survivors in Uganda

Evaluating the adaptive immune responses to natural infection with Crimean-Congo hemorrhagic fever (CCHF) virus (CCHFV) in human survivors is critical to the development of medical countermeasures. However, the correlates of protection are unknown. As the most prevalent tick-borne human hemorrhagic fever virus with case fatality rates of 5%-30% and worldwide distribution, there is an urgent need to fill these knowledge gaps. Here, we describe adaptive immune responses in a cohort of Ugandan CCHF survivors via serial sampling over 6 years. We demonstrate persistent antibodies after infection and cross-neutralization against various clades of authentic CCHFV, as well as potent effector function. Moreover, we show for the first time persistent, polyfunctional antigen-specific memory T-cell responses to multiple CCHFV proteins up to 9 years after infection. Together, this data provides immunological benchmarks for evaluating CCHFV medical countermeasures and information that can be leveraged toward vaccine immunogen design and viral target identification for monoclonal antibody therapies.

The Adaptive Immune Response against Bunyavirales

The Bunyavirales order includes at least fourteen families with diverse but related viruses, which are transmitted to vertebrate hosts by arthropod or rodent vectors. These viruses are responsible for an increasing number of outbreaks worldwide and represent a threat to public health. Infection in humans can be asymptomatic, or it may present with a range of conditions from a mild, febrile illness to severe hemorrhagic syndromes and/or neurological complications. There is a need to develop safe and effective vaccines, a process requiring better understanding of the adaptive immune responses involved during infection. This review highlights the most recent findings regarding T cell and antibody responses to the five Bunyavirales families with known human pathogens (Peribunyaviridae, Phenuiviridae, Hantaviridae, Nairoviridae, and Arenaviridae). Future studies that define and characterize mechanistic correlates of protection against Bunyavirales infections or disease will help inform the development of effective vaccines.

Olawoye I, Akano K, Okolie J, Eromon P, Olaitan P, Olagunoye A, Adebayo I, Adebayo V, Babalola E, Abioye O, Ajayi N, Ogah E, Ukwaja K, Okoro S, Oje O, Kingsley OC, Eke M, Onyia V, Achonduh-Atijegbe O, Ewah FE, Obasi M, Igwe V, Ayodeji O, Chukwuyem A, Owhin S, Oyejide N, Abah S, Ingbian W, Osoba M, Alebiosu A, Nadesalingam A, Aguinam ET, Carnell G, Krause N, Chan A, George C, Kinsley R, Tonks P, Temperton N, Heeney J, Happi C. Immunological insights into COVID-19 in Southern Nigeria

Introduction

One of the unexpected outcomes of the COVID-19 pandemic was the relatively low levels of morbidity and mortality in Africa compared to the rest of the world. Nigeria, Africa's most populous nation, accounted for less than 0.01% of the global COVID-19 fatalities. The factors responsible for Nigeria's relatively low loss of life due to COVID-19 are unknown. Also, the correlates of protective immunity to SARS-CoV-2 and the impact of pre-existing immunity on the outcome of the COVID-19 pandemic in Africa are yet to be elucidated. Here, we evaluated the natural and vaccine-induced immune responses from vaccinated, non-vaccinated and convalescent individuals in Southern Nigeria throughout the three waves of the COVID-19 pandemic in Nigeria. We also examined the pre-existing immune responses to SARS-CoV-2 from samples collected prior to the COVID-19 pandemic.

Methods

We used spike RBD and N- IgG antibody ELISA to measure binding antibody responses, SARS-CoV-2 pseudotype assay protocol expressing the spike protein of different variants (D614G, Delta, Beta, Omicron BA1) to measure neutralizing antibody responses and nucleoprotein (N) and spike (S1, S2) direct ex vivo interferon gamma (IFNγ) T cell ELISpot to measure T cell responses.

Result

Our study demonstrated a similar magnitude of both binding (N-IgG (74% and 62%), S-RBD IgG (70% and 53%) and neutralizing (D614G (49% and 29%), Delta (56% and 47%), Beta (48% and 24%), Omicron BA1 (41% and 21%)) antibody responses from symptomatic and asymptomatic survivors in Nigeria. A similar magnitude was also seen among vaccinated participants. Interestingly, we revealed the presence of preexisting binding antibodies (N-IgG (60%) and S-RBD IgG (44%)) but no neutralizing antibodies from samples collected prior to the pandemic.

Discussion

These findings revealed that both vaccinated, non-vaccinated and convalescent individuals in Southern Nigeria make similar magnitude of both binding and cross-reactive neutralizing antibody responses. It supported the presence of preexisting binding antibody responses among some Nigerians prior to the COVID-19 pandemic. Lastly, hybrid immunity and heterologous vaccine boosting induced the strongest binding and broadly neutralizing antibody responses compared to vaccine or infection-acquired immunity alone.

[Recent advances in the development of vaccines against hemorrhagic fevers caused by arenaviruses]

Arenaviruses are a global threat, causing thousands of deaths each year in several countries around the world. Despite strong efforts in the development of vaccine candidates, vaccines against Lassa fever or Bolivian and Venezuelan hemorrhagic fevers are yet to be licensed for a use in humans. In this synthesis, we present the arenaviruses causing fatal diseases in humans and the main vaccine candidates that have been developed over the past decades with an emphasis on the measles-Lassa vaccine, the first Lassa vaccine ever tested in humans, and on the MOPEVAC platform that can potentially be used as a pan-arenavirus vaccine platform.