Functional variation in lymph node arrangements within the axilla

Intradermal Immunization of Leishmania donovani Centrin Knock-Out Parasites in Combination with Salivary Protein LJM19 from Sand Fly Vector Induces a Durable Protective Immune Response in Hamsters

Background

Visceral leishmaniasis (VL) is a neglected tropical disease and is fatal if untreated. There is no vaccine available against leishmaniasis. The majority of patients with cutaneous leishmaniasis (CL) or VL develop a long-term protective immunity after cure from infection, which indicates that development of an effective vaccine against leishmaniasis is possible. Such protection may also be achieved by immunization with live attenuated parasites that do not cause disease. We have previously reported a protective response in mice, hamsters and dogs with Leishmania donovani centrin gene knock-out parasites (LdCen^-/-), a live attenuated parasite with a cell division specific centrin1 gene deletion. In this study we have explored the effects of salivary protein LJM19 as an adjuvant and intradermal (ID) route of immunization on the efficacy of LdCen^-/- parasites as a vaccine against virulent L. donovani.

Methodology/Principal Findings

To explore the potential of a combination of LdCen^-/- parasites and salivary protein LJM19 as vaccine antigens, LdCen^-/- ID immunization followed by ID challenge with virulent L. donovani were performed in hamsters in a 9-month follow up study. We determined parasite burden (serial dilution), antibody production (ELISA) and cytokine expression (qPCR) in these animals. Compared to controls, animals immunized with LdCen^-/- + LJM19 induced a strong antibody response, a reduction in spleen and liver parasite burden and a higher expression of pro-inflammatory cytokines after immunization and one month post-challenge. Additionally, a low parasite load in lymph nodes, spleen and liver, and a non-inflamed spleen was observed in immunized animals 9 months after the challenge infection.

Conclusions

Our results demonstrate that an ID vaccination using LdCen^-/-parasites in combination with sand fly salivary protein LJM19 has the capability to confer long lasting protection against visceral leishmaniasis that is comparable to intravenous or intracardial immunization.

Leishmaniasis is a disease with a wide spectrum of clinical manifestations caused by different species of protozoa belonging to the Leishmania genus that are transmitted by sand fly vectors. Visceral infections of Leishmania cause significant mortality and morbidity and development of a vaccine to prevent leishmaniasis has become a high priority. We have previously reported that intravenous immunization with a live attenuated parasite vaccine comprised of Leishmania donovani parasites lacking the centrin gene conferred protection in mice, hamsters and dogs. In the current report, we describe the immunological response and associated protection to the ID immunization with attenuated parasites in combination with a sand fly salivary protein (LJM19). We observe that protection against experimental ID challenge with L. donovani resulting from ID immunization with live attenuated parasites in combination with LJM19 is comparable to intracardial immunization and offers improved protective immunity compared to immunization with salivary protein alone and non-immunized hamsters. This study supports the potential use of the genetically attenuated vaccine and a recombinant sand fly salivary protein for control of visceral leishmaniasis.

Peripheral lymphovenous communication in lymphoedema

AIM

To investigate whether in lower extremity lymphoedema, lymph proteins enter blood before they do the thoracic duct.

METHODS

Retrospective analysis of routine lymphoscintigraphy in 69 adults imaged at 5, 45 and 150 min following bilateral subcutaneous web space injection of Tc-nanocolloid was carried out. Regions of interest were placed over the liver and ilioinguinal lymph nodes bilaterally on the anterior images at 45 and 150 min. Individual minor (0.5 point for each) and major (1 point for each) criteria of abnormal scintigraphy were applied to each limb and summed to give a lymphoscintigraphic abnormality score. An abnormal limb had a score ≥1.

RESULTS

The ratio of hepatic counts per pixel to total bilateral ilioinguinal counts (L/N ratio) was higher in patients with abnormal results on lymphoscintigraphy (median 6.2; interquartile range 4.0-15.6 pixels×10; n=48) compared with that in patients with normal lymphoscintigraphic results (2.5 [1.5-5.0] pixels×10; n=21; P<0.0002). In the abnormal group, the lymphoscintigraphic score (two limbs summed) correlated with the 150-min L/N ratio (r s=0.42; P<0.005). L/N ratios at 45 and 150 min correlated in the abnormal group (r s=0.44; P<0.005) but not in the normal group (r s=0.3; P>0.05). The 45-min activity, as a percentage of the 150-min activity, was higher in lymph nodes than in the liver in both the abnormal (35.0 [8.2-50.0] vs. 10.6 [5.8-30.0]%; P<0.0001]) and normal groups (38.3 [18.4-63.5] vs. 23.3 [12.4-33.1]%; P<0.05), and, with respect to the liver, was higher in the normal group (P<0.01).

CONCLUSION

In lymphoedema, more lymph proteins enter blood proximal to the thoracic duct. The time courses of nodal and hepatic activities suggest that access may occur within nodes themselves.