Summary Prospectus by Investment Company (Form 497K)

Class A

Shares

Class C

Shares

Advisor Class

Shares

Class Z

Shares

Maximum Sales Charge (Load) Imposed on Purchases

(as a percentage of offering price)

Maximum Deferred Sales Charge (Load)

(as a percentage of offering price or redemption proceeds, whichever is lower)

Exchange Fee

Management Fees

Distribution and/or Service (12b-1) Fees

Other Expenses:

Transfer Agent

Interest Expense

Other Expenses(b)

Total Other Expenses

Total Annual Portfolio Operating Expenses(c)

For Class C shares, the contingent deferred sales charge, or CDSC, is 0% after the first year. Class C shares automatically convert to Class A shares after eight years.

"Other Expenses" includes acquired fund fees and expenses totaling less than .01%.

If interest expense were excluded, Total Annual Portfolio Operating Expenses would be as follows:

After 1 Year

After 3 Years

After 5 Years

After 10 Years

If you did not redeem your shares at the end of the period, your expenses would be decreased by approximately $100.

forward commitments;

tender option bonds;

zero-coupon municipal securities and variable, floating and inverse floating-rate municipal securities;

certain types of mortgage-related securities; and

derivatives, such as options, futures contracts, forwards and swaps.

Market Risk: The value of the Portfolio's assets will fluctuate as the market or markets in which the Portfolio invests fluctuate. The value of the Portfolio's investments may decline, sometimes rapidly and unpredictably, simply because of economic changes or other events, including public health crises (including the occurrence of a contagious disease or illness), terrorism, war, changing interest rate levels, imposition of new or additional tariffs, and regional and global conflicts, that affect large portions of the market.

Interest Rate Risk: Changes in interest rates will affect the value of investments in fixed-income securities. When interest rates rise, the value of existing investments in fixed-income securities tends to fall and this decrease in value may not be offset by higher income from new investments. Interest rate risk is generally greater for fixed-income securities with longer maturities or durations. Changing interest rates may have unpredictable effects on the markets, may result in heightened market volatility and may detract from Portfolio performance. In addition, changes in monetary policy may exacerbate the risks associated with changing interest rates.

Duration Risk: Duration is a measure that relates the expected price volatility of a fixed-income security to changes in interest rates. The duration of a fixed-income security may be shorter than or equal to the full maturity of a fixed-income security. Fixed-income securities with longer durations have more risk and will decrease in price as interest rates rise.

Below Investment Grade Securities Risk: Investments in fixed-income securities with lower ratings (commonly known as "junk bonds") have a higher probability that an issuer will default or fail to meet its payment obligations. These securities may be subject to greater price volatility due to such factors as specific corporate developments, interest rate sensitivity and negative performance of the junk bond market generally and may be more difficult to trade than other types of securities.

Municipal Market Risk: This is the risk that special factors may adversely affect the value of municipal securities and have a significant effect on the yield or value of the Portfolio's investments in municipal securities. These factors include economic conditions, political or legislative changes, public health crises, uncertainties related to the tax status of municipal securities, and the rights of investors in these securities. To the extent that the Portfolio invests more of its assets in the municipal securities of a particular state or territory, the Portfolio may be vulnerable to events adversely affecting that state or territory, including economic, political and regulatory occurrences, court decisions, terrorism, public health crises (including the occurrence of a contagious disease or illness) and catastrophic natural disasters, such as hurricanes, fires or earthquakes. The Portfolio's investments in certain municipal securities with principal and interest payments that are made from the revenues of a specific project or facility, and not general tax revenues, may have increased risks. Factors affecting the project or facility, such as local business or economic conditions, could have a significant effect on the project's ability to make payments of principal and interest on these securities.

Inflation Risk: This is the risk that the value of assets or income from investments will be less in the future as inflation decreases the value of money. As inflation increases, the value of the Portfolio's assets can decline as can the value of the Portfolio's distributions. This risk is significantly greater for fixed-income securities with longer maturities.

Credit Risk: An issuer or guarantor of a fixed-income security, or the counterparty to a derivatives or other contract, may be unable or unwilling to make timely payments of interest or principal, or to otherwise honor its obligations. The issuer or guarantor may default, causing a loss of the full principal amount of a security and accrued interest. The degree of risk for a particular security may be reflected in its credit rating. There is the possibility that the credit rating of a fixed-income security may be downgraded after purchase, which may adversely affect the value of the security.

Leverage Risk: To the extent the Portfolio uses leveraging techniques, such as TOBs, its net asset value ("NAV") may be more volatile because leverage tends to exaggerate the effect of changes in interest rates and any increase or decrease in the value of the Portfolio's investments.

Tax Risk: There is no guarantee that the income on the Portfolio's municipal securities will be exempt from regular U.S. federal, and if applicable, state income taxes. From time to time, the U.S. Government and the U.S. Congress consider changes in U.S. federal income tax law that could limit or eliminate the federal tax exemption for municipal bond income, which would in effect reduce the income received by shareholders from the Portfolio by increasing taxes on that income. In such event, the Portfolio's NAV could also decline as yields on municipal bonds, which are typically lower than those on taxable bonds, would be expected to increase to approximately the yield of comparable taxable bonds. Actions or anticipated actions affecting the tax exempt status of municipal bonds could also result in significant shareholder redemptions of Portfolio shares as investors anticipate adverse effects on the Portfolio or seek higher yields to offset the potential loss of the tax deduction. As a result, the Portfolio would be required to maintain higher levels of cash to meet the redemptions, which would negatively affect the Portfolio's yield.

Illiquid Investments Risk: Illiquid investments risk exists when certain investments are or become difficult to purchase or sell. Difficulty in selling such investments may result in sales at disadvantageous prices affecting the value of your investment in the

Portfolio. Causes of illiquid investments risk may include low trading volumes, large positions and heavy redemptions of Portfolio shares. Illiquid investments risk may be higher in a rising interest rate environment, when the value and liquidity of fixed-income securities generally decline. Municipal securities may have more illiquid investments risk than other fixed-income securities because they trade less frequently and the market for municipal securities is generally smaller than many other markets.

Derivatives Risk: Derivatives may be difficult to price or unwind and leveraged so that small changes may produce disproportionate losses for the Portfolio. A short position in a derivative instrument involves the risk of a theoretically unlimited increase in the value of the underlying asset, reference rate or index, which could cause the Portfolio to suffer a potentially unlimited loss. Derivatives, especially over-the-counter derivatives, are also subject to counterparty risk, which is the risk that the counterparty (the party on the other side of the transaction) on a derivative transaction will be unable or unwilling to honor its contractual obligations to the Portfolio.

Tender Option Bonds Risk: The Portfolio's participation in TOB transactions may reduce the Portfolio's returns and increase volatility and expose the Portfolio to credit risk and leverage risk. Investments in TOB transactions typically will involve greater risk than investments in fixed rate municipal bonds, including the risk of loss of principal. The interest payments that the Portfolio receives in connection with a TOB transaction ("inverse floaters") vary inversely with short-term interest rates and will be reduced, or potentially eliminated, when short-term interest rates rise. The Portfolio will be subject to leverage risk to the extent that the Portfolio uses the proceeds from a TOB transaction to invest in other securities. If the interest expense on borrowings or other costs of the leverage approach the net return on the Portfolio's investment portfolio or investments made through leverage, as applicable, the benefit of leverage to the Portfolio's shareholders will be reduced. If the interest expense on borrowings or other costs of leverage were to exceed the net return to the Portfolio, the Portfolio's use of leverage would result in a lower rate of net return than if the Portfolio were not leveraged. During periods of rising short-term interest rates, the interest paid on floaters in TOBs would increase, which may adversely affect the Portfolio's net return. The Portfolio's investment in a TOB will generally underperform the market for fixed rate municipal securities when interest rates rise. The value of inverse floaters may be volatile and there may be limited liquidity in the market for inverse floaters. Because investments in inverse floaters issued in TOB transactions are derivative instruments, these investments are also subject to the risks associated with investments in derivatives.

Management Risk: The Portfolio is subject to management risk because it is an actively-managed investment fund. The Adviser will apply its investment techniques and risk analyses in making investment decisions, but there is no guarantee that its techniques will produce the intended results. Some of these techniques may incorporate, or rely upon, quantitative models, but there is no guarantee that these models will generate accurate forecasts, reduce risk or otherwise perform as expected.

how the Portfolio's performance changed from year to year over ten years; and

how the Portfolio's average annual returns for one, five and ten years compare to those of a broad-based securities market index.

Bloomberg Municipal Bond Index

(reflects no deduction for fees, expenses or taxes)

After-tax Returns:

Are shown for Class A shares only and will vary for the other Classes of shares because these Classes have different expense ratios;

Are an estimate, which is based on the highest historical individual federal marginal income tax rates and do not reflect the impact of state and local taxes; actual after-tax returns depend on an individual investor's tax situation and are likely to differ from those shown; and

Are not relevant to investors who hold Portfolio shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts.

Inception date for Class Z shares: 9/28/2018. Performance information for periods prior to the inception of Class Z shares is the performance of the Portfolio's Class A shares adjusted to reflect the expenses of Class Z shares.